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Impact of winemaking practices on the concentration andcomposition of tannins in red wine

P.A. SMITH1,2, J.M. MCRAE1 and K.A. BINDON1

1 The Australian Wine Research Institute, Urrbrae, SA 5064, Australia; 2 Flinders Centre for Marine BioproductsDevelopment (CMBD), and Department of Medical Biotechnology, School of Medicine, Flinders University, Bedford Park,

SA 5042, AustraliaCorresponding author: Dr Paul Smith, email [email protected]

AbstractThis review summarises key findings from research on the impact of winemaking practices on the concentration and compositionof tannins in red wines. The impact from the point of crushing onwards is summarised from our research and recent literature takinginto account the effect of maceration, yeast selection, addition of mannoproteins, addition of oenotannins, fining by animal andplant proteins, filtration, oxygen exposure, barrel treatment, bottling and accelerated-ageing techniques. A sufficient body ofevidence has developed in certain areas to make generalisations, but in several other areas tannins continue to show large variabilityof response to winemaking interventions depending on the grapes and their particular methods of treatment. Progress has beenmade in determining the underpinning mechanisms for some of the effects, but significant further research is required to understandwhy many of the effects occur. Knowledge gaps remaining in the area and proposals for future research are identified that willprovide the opportunity for improved management of vineyards and winemaking to optimise tannins in grapes and wine, and forincreased capacity to meet wine specification, consumer expectations and profitability.

Keywords: colour, enzyme, extraction, filtration, fining, maceration, packaging, tannin, winemaking, yeast

IntroductionThere are many points along the wine value chain whereknowledge of factors influencing the concentration and compo-sition of tannins can be used to influence the final wine style.Such knowledge can inform decision making concerningharvest, winemaking, ageing and packaging. It has also providedthe opportunity for improved management of vineyards andwinemaking to optimise tannins in grapes and wine, and forincreased capacity to meet wine specification, consumer expec-tations and profitability.

Tannins, including grape-derived condensed tannins(flavanoids) and oak-derived hydrolysed tannins (non-flavonoids), produce sensations of astringency in food and drinkand contribute significantly to the ‘structure’ of wine. The termastringency refers to the drying and puckering sensations in themouth and is a characteristic of red wine that is consideredpleasant when balanced with other factors including alcoholand sugar content (Gawel 1998). Wine acidity also influencesastringency with wines of greater acidity being perceived asmore astringent (Fontoin et al. 2008). The sensory perception ofwine tannins is dependent on the maximum intensity, totalduration and time taken to reach maximum intensity, as well asthe extent of mouth drying and mouth roughness (Gawel1998). Knowledge of the structure of the tannins in a winematrix, the points where they can be manipulated and theimpact of these structures on the sensory properties of wine isessential for improving the end product.

Tannin chemistryTannins are highly reactive phenolic substances and are catego-rised as either condensed or hydrolysable. Grape phenolic sub-stances are chemically modified as soon as grapes are crushed,which continues through fermentation and ageing. Many types

of reactions happen at different rates at the various stages ofwine production, and these reactions determine the final colourand taste properties. Tannins are one of the critical classes ofphenolic substances that undergo significant changes duringwinemaking; in particular the conversion of ‘grape’ tannins (a)into more chemically complex ‘wine’ tannins (b) (Figure 1).

Hydrolysable tanninsHydrolysable tannins are generally extracted from the oak barrelsused in wine ageing. Their structure consists of a glucose mol-ecule acylated with galloyl groups. The quantity of these oak-derived tannins depends on the amount of time the wine is agedin the barrels, whether the barrels were new or had been usedpreviously and the origin of the oak. Relative to condensedtannins, hydrolysable tannins occur only in low concentration inoaked wines, and as such will not be discussed in this review.

Grape tanninsCondensed tannins are readily extracted from the skin, fleshand seeds of grapes during the winemaking process and con-tribute the majority of tannins to red wine, up to 4 g/L. Theyconsist of repeating flavan-3-ol units, such as catechin,epicatechin, epigallocatechin and epicatechin gallate (Herderichand Smith 2005). The subunits are linked by acid-labileinterflavan bonds. They are extracted from the skin, seeds and,to a lesser extent, the flesh of grapes in variable proportionduring winemaking. Skin tannins consist of long polymericchains ranging from an average of 3 to 83 flavonol subunits[mean degree of polymerisation (DP)] and constitute a largerproportion of gallocatechin-derived units because of thegreater proportion of prodelphinidins to procyanidins ingrape skin. These tri-hydroxylated subunits consist mainly ofepigallocatechin, but with trace amounts of gallocatechin andepigallocatechin 3-O-gallate. Seed tannins are much smaller

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doi: 10.1111/ajgw.12188© 2015 Australian Society of Viticulture and Oenology Inc.

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(reported as being between DP 2 to 16) than skin tannins andare composed mainly of catechin and epicatechin subunits, witha greater proportion of galloylated units (13–29%) comparedwith that of skin tannins (Herderich and Smith 2005).

Wine tanninsStructurally, wine tannins are less well understood than grapetannins. This is largely because the structure of wine tannins ismostly resistant to methods of analysis, such as acid-catalysedcleavage of the interflavan bonds and subsequent thiolysis orreaction with phloroglucinol (Cheynier et al. 2000, Kennedyand Jones 2001, Herderich and Smith 2005). Once condensed,tannins have been extracted from grapes; they are structurallymodified by yeast, enzymes and fermentation by-products (e.g.acetaldehyde). After fermentation, wine tannins continue toundergo chemical changes that gradually alter the purple hue ofyoung wine to a brick red colour and generally the tanninsbecome less astringent.

Structural alterations of tannins involve both direct andindirect condensation reactions and depolymerisation of thetannins. The mechanisms of these processes have been dis-cussed in detail elsewhere (Cheynier et al. 2000). In brief, directcondensation reactions occur with flavanol-3-ol monomers,anthocyanins, anthocyanin-derived pigments and oligomers.Indirect condensation reactions are facilitated by oxidationproducts, including acetaldehyde from ethanol and also pro-duced by yeast; pyruvic acid from glycerol; and glyoxylic acidfrom tartaric acid. These can alter the interflavan bonds, sus-ceptibility to acid-catalysed cleavage and sensory characteristics.For example, acetaldehyde-mediated condensation reactionslead to ethyl-linked tannins but these ethyl-linked structuresare unstable. The incorporation of anthocyanins andanthocyanin-derived pigments leads to the formation of col-oured pigmented tannins that are generally more resistant tobleaching by sulfur dioxide and contribute to long-term colourstability. The structure of tannins influences the sensory prop-erties. Larger molecular mass tannins are perceived as moreastringent while smaller molecular mass tannins, such asflavanol monomers and other non-flavonoid phenolics, are per-ceived as bitter (Fontoin et al. 2008, McRae et al. 2013).

Impact of the winemaking process on tanninsThere are many points during the red wine production processwhich influence the concentration and composition of tannins.Although critical to the outcome of the wine, this review will

not discuss the factors that influence tannins during grape pro-duction or grape properties at harvest. This review will focusfrom the point of crushing onwards and include a summary ofrecent literature reporting on the effect of maceration, yeastselection, addition of mannoproteins, addition of oenotannins,fining (animal and plant proteins), filtration, oxygen exposure,barrel treatment, bottling and accelerated-ageing techniques.

MacerationFor the purpose of this review, which has a specific focus on theconcentration and composition of tannins, maceration is definedas the period during which the fermenting must or wine is incontact with the grape cap (grape insoluble solids, pomace, ormarc). To identify maceration techniques that alter tanninextraction, the authors aim to highlight winemaking methodsthat influence the transfer of tannins to wine during the period ofcap contact. To clarify this definition, Figure 2 shows the struc-ture of a grape cell and the localisation of potential sources ofgrape tannins for wine. Winemaking intervention can targettannins according to their location within the grape cell, therebyaltering the degree to which it is extracted. These effects,however, may also be exerted by changing the degree to whichtannins are lost as a precipitate, adsorbed to sedimenting mate-rials (i.e. lees) or by affecting other colloidal properties whichunderpin its stability in wine. The period of cap contact can affectall of these aspects, thereby altering points at which tannins areextracted, removed or stabilised during the winemaking process.

Winemaking techniques that manipulate the macerationprocess affect the extent or rate of transfer from the cap to themust (wine). These techniques may either increase the solubilityof extractable components, in this instance the focus of thecurrent review, tannins, or decrease the integrity of the cap insome way (Figure 2). This may occur simply through extendingthe length of cap contact time or by a more strategic interventionthat facilitates breakdown of the plant cell wall or intracellularmembranes, releasing the cell contents to the wine medium. Itshould be noted that grape composition may strongly influencethis process. For example, it is considered that anthocyanins maybe necessary to facilitate the solubilisation and retention oftannins (Figure 2) during fermentation through the formation ofpolymeric pigments (Kilmister et al. 2014).

Various effects of maceration on grape and wine phenolicsubstances have been reviewed (Sacchi et al. 2005, Casassa andHarbertson 2014). In terms of the management of tannins spe-cifically, these reviews have highlighted that enzyme addition

)b()a(

Figure 1. Tannins are one criticalclass of phenolic substances thatundergo significant changes duringwinemaking, in particular theconversion of (a) ‘grape’ tanninsinto more chemically complex (b)‘wine’ tannins.

602 Impact of winemaking practices on tannins Australian Journal of Grape and Wine Research 21, 601–614, 2015

© 2015 Australian Society of Viticulture and Oenology Inc.

and extended maceration (EM) are winemaking techniques thatconsistently increase tannins in the finished wine. To add to thepoints raised in these reviews, experimental results are summa-rised below from a range of studies that aim to understand theway that such winemaking techniques affect the extraction andcomposition of tannins during the maceration process. Obser-vations from the current literature and reviews highlight thatduring the early stages of fermentation, extraction of tanninsfrom the skin exceeds that from the seed while in the laterstages of maceration, extraction of seed tannins predominates.Reports about the extraction of skin and seed tannins duringfermentation have identified a lag phase during which seedtannins are poorly extractable (Peyrot des Gachons andKennedy 2003, Cerpa-Calderón and Kennedy 2008,Hernández-Jiménez et al. 2012), which appears to be related tothe period in which hydration of the seed takes place. In thedeveloping grape berry, accumulation of seed tannins is knownto occur up to veraison, after which it declines. The decline ofseed tannins during grape ripening may be related to a period ofprogrammed oxidation, whereby tannins may be rendered lessextractable, and the seed itself less permeable, in preparation forsenescence (Kennedy et al. 2000).

Further to this, work by Peyrot des Gachons and Kennedy(2003) and Cerpa-Calderón and Kennedy (2008) identified anapproach by which the extraction of skin tannins could bestudied during the winemaking process. Skin tannins appear tofollow a Boltzmann sigmoid extraction model, reaching a

plateau (Cerpa-Calderón and Kennedy 2008), while the extrac-tion of seed tannins follows a linear model once the initialhydration phase is complete (Hernández-Jiménez et al. 2012).According to these studies, extraction of skin tannins may bemore variable depending upon the conditions of maceration,while seed tannins could increase in a linear manner whenmaceration is extended. It is noted, however, that the studies ofCerpa-Calderón and Kennedy (2008) and Hernández-Jiménezet al. (2012) were undertaken on a limited sample set, henceextrapolation to other conditions is not possible at present. Theenvironmental, genetic and ripeness effects that limit skin andseed hydration and their resulting extractability should be animportant component of further research.

Cerpa-Calderón and Kennedy (2008) also showed that theheight of the plateau reached in terms of the extraction of skintannins was dependent upon the conditions of maceration. Inthat study uncrushed grapes were compared with varyingdegrees of grape crushing. Generally, a higher level of grapecrushing was found to increase the extraction of both skin andseed tannins (maximum at 75% crush) and also decrease thetime required to reach 50% extraction. In light of this, it wouldappear probable that the degree to which the cap (skins, seeds)remains in contact with the must/wine will significantly affectthe extraction of tannins. While this may seem logical, the effectof cap management during winemaking has received surpris-ingly little research attention. During fermentation, the cap canbe: punched down by periodically plunging the buoyant solids;

Figure 2. The interaction between the grape cells and wine involves a complex process of extraction of tannins and loss of tannins through adsorption,precipitation, sedimentation and stabilisation that leads to retention in the final wine.



pumped over, in which a lower layer of wine is pumped backonto the cap; or continually submerged such as in rotary orsubmerged cap techniques. The review of Sacchi et al. (2005)concluded that rotary fermenters extracted more tannins thanthe punch-down method, which in turn showed greater extrac-tion than the pumping over technique. More recent work byIchikawa et al. (2012) showed that submerged cap extractedmore tannins than punching down and, interestingly, reportedthat losses of tannins following pressing were reduced insubmerged-cap ferments. Bosso et al. (2012) explored this moredeeply, also observing a higher concentration of tannins inwines made by the submerged-cap method, but suggested thatlower extraction of tannins may in fact have taken place than inpunched down wines. They suggest that the higher concentra-tion of tannins in finished submerged-cap wines was because ofhigher retention of tannin, which is in agreement with theresults of Ichikawa et al. (2012). Bosso et al. (2012) suggestedthat the degree to which the cap became oxidised during thefermentation process may also have affected the stability oftannins. The role of oxygen on the extraction of tannins inwinemaking will be discussed later in this review.

A further aspect of maceration which affects the extractionof tannins is the degree of grape cell wall integrity. Fermentationcauses a loss of pectic polysaccharides and associatedhemicelluloses from the grape skin cell wall (Doco et al. 2007,Romero-Cascales et al. 2012, Bindon and Smith 2013, Zietsmanet al. 2015). Macerating enzymes available for commercial useusually contain pectin-degrading enzyme activities, and maycontain certain additional enzymes such as hemicellulases(Bautista-Ortín et al. 2007a, Romero-Cascales et al. 2012,Zietsman et al. 2015). Hence their application in macerationmay significantly enhance the degradation of pectic materialfrom the grape cell wall (Romero-Cascales et al. 2012,Apolinar-Valiente et al. 2014, Zietsman et al. 2015). There isevidence that the removal of the pectic fraction from cell wallsdecreases the adsorption properties of the cell wall for tannins(Bindon and Smith 2013, Ruiz-Garcia et al. 2014). By inference,this may render tannins more extractable from the skins duringfermentation. Based on this, it is observed that the application ofmacerating enzymes is generally successful in increasing theextraction of tannins during red winemaking (Ducasse et al.2010, Busse-Valverde et al. 2010, 2011, Ortega-Heras et al.2012, Bautista-Ortín et al. 2013, González-Neves et al. 2013,Nel et al. 2014), although there are some instances where theeffect is variable or negligible depending on cultivar, environ-mental conditions or stage of the winemaking process(Bautista-Ortín et al. 2007a, Busse-Valverde et al. 2010,Ortega-Heras et al. 2012, Nel et al. 2014). In terms of the com-position of tannins, however, the application of maceratingenzymes does not show consistent effects. For example, Ducasseet al. (2010) showed for Merlot that increased wine tannins inresponse to a variety of enzyme treatments had a variable effecton mean degree of polymerisation (mDP), % galloylation and %epigallocatechin of tannins. This may indicate that the effect ofenzyme application is exerted on both skin and seed compo-nents. A role for enzymatic degradation of seed cell walls waslater confirmed by the results of Busse-Valverde et al. (2011)and Bautista-Ortín et al. (2013). In particular, Bautista-Ortínet al. (2013) showed that that polygalacturonase and cellulaseactivity favour the degradation of seed cell walls, promotingrelease of seed proanthocyanidins.

An aspect which has not received significant attention untilrecently is the potential losses of tannins as an adsorbed fractionwithin the gross (early racking) wine lees. Gross wine lees areexpected to be primarily yeast biomass and some tartrates, and

yet the evidence suggests that grape-derived solids (pulp)co-sediment with the wine lees and have the capacity to adsorbtannins (Figure 2) (Bindon et al. 2010a,b, Hanlin et al. 2010).Grape pulp cell walls have been identified as having a highbinding capacity for grape-derived tannins (Bindon et al.2010a,b) and are present in significant proportion in the fer-menting must. A hypothesis proposed here is that maceratingenzymes may not only affect extraction, that is, facilitate releaseof tannins from the skin or seed cell wall, but that they mightalso limit loss of tannins via adsorption and subsequent sedi-mentation. Degradation of the cell walls in the presence ofmacerating enzymes, in particular losses of pecticpolysaccharides (Le Bourvellec et al. 2012a, Ruiz-Garcia et al.2014), can reduce the adsorption capacity for tannins. Wepropose that this may be an additional factor which enhancesthe retention of tannins in solution in enzyme-treated wines,while recognising that extraction may simply be enhanced viadegradation of the skin and seed cell walls.

To understand in greater detail how a disruption of cellularintegrity during the maceration process can influence extractionof tannins, other winemaking techniques can be discussedwhich have produced similar results to enzyme application. Theimpact of variations in temperature profile within the fermenthas recently been reported in relation to impact on tannins andcolour (Lerno et al. 2015). There was a relatively constantincrease in extraction of tannins over time, and it can be seenthat increasing fermentation temperature led to increasedextraction of tannins and seed tannins (as assessed by galloylatedsubunits from phloroglucinolysis) for all treatments duringactive fermentation. Treatments in which the must temperaturewas the same (regardless of the cap temperature) were notsignificantly different in the concentration of tannins. TheSacchi et al. (2005) review discussed that the application ofthermovinification (heating the must to between 60 and 70°C)can lead to an increase in extraction of anthocyanins whenincluded with a skin contact period after heating. That reviewconcluded, however, that effects on extraction of tannins wereunknown or variable. Since that report, more recent studieshave focused on the application of alternative heating tech-niques, such as flash déténte or microwave, to facilitate themaceration process. Flash déténte is the process of rapidlyheating the grapes (to around 95°C) for a set period, thenapplying a strong vacuum. The process is proposed to degradethe cellular structure. Evidence for this has been provided byDoco et al. (2007) who found that the process, when includedwith skin contact, increased extraction of the polysaccharides ofthe grape berry cell wall, namely arabinogalactans andrhamnogalacturonans. The extent to which the processdegraded grape cell walls was found to be highly cultivardependent; therefore limitations may exist in the effectiveness ofthe technique. In terms of a corresponding effect on the concen-tration of wine tannins, Morel-Salmi et al. (2006) showed thatfor two seasons on the grape cultivars, Grenache, Mourvedreand Carignan, flash déténte-treated wines had a higher tanninconcentration as well as an increased tannins-to-anthocyaninsratio. When pressed directly after treatment, however, phenolicsubstances were lost. Cap maceration was therefore a require-ment of the treatment, which is in strong agreement with thefindings of Doco et al. (2007) with respect to polysaccharides.

Another method which applies heat to grape must is the useof microwave maceration, which has not yet been applied on acommercial scale as has flash déténte. It is, however, noted to bea promising technology for cultivars such as Pinot Noir that aretraditionally poor in tannins (Carew et al. 2014a,b). Studies onPinot Noir have shown that microwave application causes a



release of cellular contents not achievable with standardthermovinification (Carew et al. 2014a). Similar to the resultsfor flash déténte, microwave-treated Pinot Noir resulted in ahigher concentration of wine tannins only when fermentedwith continued cap contact (as opposed to early press off)(Carew et al. 2014a,b). Interestingly, microwave-treated PinotNoir musts pressed before the onset of fermentation resulted inwines with equivalent phenolic profiles to that of a controltreatment fermented with cap contact (Carew et al. 2014a).

A promising technique, which is non-thermal but mayfacilitate extraction during the maceration process by disruptionof cellular integrity, is pulsed electric field (PEF). This is a rela-tively new technology to winemaking, and is not yet widely inuse. It is a processing method that causes permeabilisation of cellmembranes with low energy requirement, apparently minimis-ing deterioration of other important food components(Puértolas et al. 2012). Key pilot studies have been conductedby Delsart et al. (2012, 2014) who showed that PEF (500–700 V/cm, 40–100 ms) application on Merlot disrupted the cellslocated in the hypodermis and epidermis, increasing the diffu-sion of tannins to the must, and ultimately to the wine. Theirresults suggested that under their PEF conditions, the cells of theMerlot grapes studied became more permeable. Delsart et al.(2014) and Cholet et al. (2014) undertook further studies onPEF treatment of Cabernet Sauvignon; high energy, long dura-tion PEF produced wine higher in tannins (by 34%) than that ofa standard maceration treatment. The treatment appeared todepolymerise high molecular mass tannins into smaller, moreextractable tannin components. The high energy PEF treatmentappears to modify the tannins associated with the skin cell wallswhile lower energy PEF affects grape vacuolar tannins (seeFigure 2). Delsart et al. (2012, 2014) suggest that the conditionsof PEF application produce a highly specific response in terms ofthe quantity and type of tannins extracted. Therefore, while thistechnique is promising, it requires considerable optimisationbefore it becomes more widely applied.

The processes discussed so far focus primarily on disruptionof the grape cellular structure for increased extraction of tanninsduring maceration. The Sacchi et al. (2005) review discussedearly work on must freezing that demonstrated increased con-centration of wine tannins, and highlighted that this approachmay cause both cellular disruption and protection from oxida-tion in the early stages of maceration. More traditional macera-tion methods attempt to influence key stages of the macerationprocess. The process known as cold soak is a pre-fermentationmaceration step which can involve holding crushed must at lowtemperature, or the application of dry ice. Sacchi et al. (2005)did not report a consistent effect of cold soaking on wine phe-nolic substances. In reviewing the variety of recent reports thathave applied these techniques, it is evident that a high level ofvariability in response is expected, because of grape cultivar,vintage, regional and/or environmental factors which may limitthe effectiveness of the method. For example, key studies byBusse-Valverde et al. (2010) and González-Neves et al. (2013)applied low temperature techniques pre-fermentation to threegrape cultivars, and found that while cold soaking could effec-tively increase the concentration of proanthocyanidins in wine,the effect was not consistent across grape cultivars. For bothstudies, the concentration of tannins in Shiraz wines was notaffected by the cold soak treatment. Moreno-Pérez et al. (2013)studied Monastrell and found that the cold soak-treated winesgenerally contained a higher concentration of proantho-cyanidins, but this was region specific, with one of four regionalstudies having a negligible result. Further studies by De Beeret al. (2006), Ortega-Heras et al. (2012) and Nel et al. (2014)

found a variable effect of cold soak on wine tannins, which maydemonstrate further examples of the influence of vintage,cultivar and region.

According to studies by Busse-Valverde et al. (2010, 2011),the effect of cold soaking on wine tannins is related to enhancedseed tannin extraction in the wines. Cold soaking is proposed tofacilitate the activity of endogenous grape maceration enzymesin degrading cell wall structure, to limit polyphenol oxidaseactivity, or to delay fermentation; factors which might beexpected to enhance either the extraction or preservation ofgrape-derived phenolic substances in wine. In light of thecrucial observations by Hernández-Jiménez et al. (2012),however, a hydration period is required before significantextraction of seed tannins proceeds. Therefore the possibilityexists that a cold soak period simply extends the macerationperiod relative to a standard maceration period. Simply stated,the extension of the maceration period, rather than the tem-perature of the pre-fermentative cold soak, may facilitateextraction from grape seeds. To explore this hypothesis further,more detailed EM studies are required.

Extended maceration is a technique whereby cap contact isheld for longer than the usual short period during which alco-holic fermentation occurs (5–10 days) and instead extends up to50 days. This technique has been extensively reviewed bySacchi et al. (2005) as well as by Casassa and Harbertson (2014)and was proposed to be one of the principal methods by whichan increase in extraction of tannins can be achieved. A keyobservation in both reviews is that, generally, EM does notenhance anthocyanins (colour) in wine, but the primary effect ison phenolic substances, polymeric pigments or tannins. Thiscurrent review has summarised recent literature, and in light ofthe observations also highlighted by Casassa and Harbertson(2014) some key points emerge:

1. For most studies of EM, an increase in the extraction of seedtannins has been observed as cap contact is continued.Exceptions to this were found where the maceration periodwas not sufficiently long, or where maceration times werecomparatively close.

2. The effect of EM varied with respect to grape cultivar, season,ripeness and region.

There were a few cases in which the application of an EMperiod produced a limited effect on wine tannins. Álvarez et al.(2006) found that for Monastrell subjected to maceration timesof 4 and 8 days, no significant difference in extractionof tannins to wine occurred. Given the observations ofHernández-Jiménez et al. (2012) and Cerpa-Calderón andKennedy (2008), the time point for the maximum extraction ofskin tannins and the initiation of seed hydration with subse-quent extraction of seed tannins might be beyond this timeperiod. This might explain why no effect was observed. Afurther study by Cadot et al. (2012) compared Cabernet Francwines produced from grapes at two stages of maturity and withtwo superimposed maceration times of 9 and 15 days. Thatstudy found that at these two maceration times, no differencewas observed in the concentration or composition of tannins.The observations of Cadot et al. (2012) are perhaps less repre-sentative of the general outcomes of EM; longer EM trialsexceeding 20 days following crushing have produced more con-sistent results. In these, the differences in extraction of tanninsare clear, and importantly the predominance of the extraction ofseed tannins in the later stages of maceration is observed. Thestudy of Cerpa-Calderón and Kennedy (2008) has previouslybeen highlighted as key in the understanding of the transfer of



tannins from grapes to wine during the maceration process. Thefundamental point of this research is that for crushed fruit, aplateau in the extraction of skin tannins occurs at approximatelyday 9 of maceration. Extraction of seed tannins predominatesafter this point. In light of the points raised above, it is importantto consider that the timing of maceration assigned by differentresearchers for EM studies can significantly impact their results.Some fundamental studies were conducted by Harbertson et al.(2009) and Casassa et al. (2013a,b) where EM was continuedfor 20 or 30 days, respectively, significantly longer than previ-ously reported work. These studies considered Merlot andCabernet Sauvignon grapes and observed that the increasedtannins from EM were primarily derived from seed tannins.Wines which had not undergone EM (10 days) tended to havea more a balanced proportion of seed and skin tannins. In themore detailed study of Casassa et al. (2013b), EM (30 days) ledto increased extraction of tannins during maceration, which atthe final sampling point was ∼73% seed derived. Similarly, Gilet al. (2012) observed that for Cabernet Sauvignon andTempranillo, wines produced from riper grapes contained ahigher proportion of skin tannins, and tannins increased withEM time independent of grape ripeness. Accordingly, tanninmDP and the proportion of epigallocatechin as a function of thecomposition of tannins decreased with EM, a strong indicationthat extraction of tannins from seeds was increased with EM. Ina detailed study Busse-Valverde et al. (2012) macerated wine upto 20 days, yet compared tannins extracted at 5, 10 and 20 days.Tannins in wines increased significantly from 5 to 10 days, butonly a small increase occurred from 10 to 20 days. In this study,the proportion of skin-derived proanthocyanidins was consist-ently higher at all the maceration stages analysed, but it is notedhere also that the time of analysis was important. The largestincrease in wine tannins was from 5 to 10 days, and thereafteronly a small increase occurred to 20 days which was mainly seedtannins. This example is one where skin tannins appeared toplateau by 10 days of maceration for all the samples fermented,yet a small increase in tannins was derived from seeds withadditional maceration time. The Busse-Valverde et al. (2012)study is an example of a winemaking where seed tannins werepoorly extractable, and the extraction of skin tannins predomi-nated irrespective of the maceration time. Irrespective of grapecomposition, the only increase in wine tannins from 10 to 20days maceration was derived from seeds. This indicates thatgrape composition may significantly impact on the extractabilityof skin or seed tannins, and as highlighted previously, thiswarrants further study.

YeastThe wide-ranging impact of different yeast on wine aroma andcolour has been well established over many years; the effect ofyeast on tannins, however, has been less thoroughly investigated.With recent advances in analytical methods with improved speci-ficity and sensitivity for determining the concentration and com-position of tannins, research has demonstrated that choice of yeastcan also have a major effect on tannins in wine.

Early research (Bautista-Ortín et al. 2007b) that specificallyincluded measurement of tannins reported that in 2002 and2003 Monastrell grapes that were fermented with INRA 7303and Rhone 2323 yeast strains showed effects in 2003 only for adifferent concentration of tannins in wine. Specifically, Rhone2323 led to a 43% increase in polymeric tannins post-ferment,and at 8 months of age the increase was maintained at 28%.Saccharomyces cerevisiae and S. bayanus have well establishedcolour impacts in red wine, and early research reported similarimpact of tannins in red wine (Hayasaka et al. 2007); several

Saccharomyces interspecific hybrids are also able to fermentgrape juice to completion. Eleven commercially availableSaccharomyces strains were used in one study (Blazquez-Rojaset al. 2012) with Australian Cabernet Sauvignon – S. cerevisiae(7), S. bayanus (2) and interspecific Saccharomyces hybrids (2).Yeast selection increased the final concentration of tannins byup to 33%. Specifically, wines prepared with S. bayanus AWRI1176 and S. cerevisiae AWRI 1486 had the lowest and highestconcentration of tannins (1.51 and 2.06 g/L epicatechin equiva-lents, respectively), and those prepared with S. cerevisiae AWRI1555 and AWRI 1486 had the lowest and highest concentrationof pigmented polymers (15.4 and 29.5 mg/L, malvidin-3-glucoside equivalents, respectively). Both S. bayanus wines hada high concentration of pigmented polymers. Saccharomycescerevisiae strains produced wines with lower colour density[13.2–15.5 absorbance units (a.u.)], and S. bayanus strains andSaccharomyces hybrid (AWRI 1501) produced wines with thehighest colour density (15.7–16.0 a.u.). Saccharomyces bayanuswines had the highest concentration of SO2-resistant pigmentsand lowest anthocyanins. A range of intermediate values fortannins and colour were reported for the strains AWRI 796, 838,1493, 1553, 1554, 1501 and 1503.

A further study (Holt et al. 2013) which evaluated theimpact of fermenting Shiraz must with different yeast strainsalso showed that choice of strain had a strong influence onseveral aspects of wine composition, including up to a 37%increase in the concentration of tannins for the same fruit.Across three parcels of Shiraz over two vintages (2009, 2010)wine fermented with S. cerevisiae AWRI 1631 had consistentlythe highest concentration of tannins (an average of 1165 mg/Lepicatechin equivalents over 2009 and 2010) and, as observedby Blazquez-Rojas et al. (2012), wine fermented with S. bayanusAWRI 1375 was consistently the lowest in tannins (an averageof 850 mg/L epicatechin equivalents over 2009 and 2010), buthighest in non-bleachable pigments. The authors additionallyshowed that the size of tannins as measured by mDP was lowestfor AWRI 1375 across these wines. Wine prepared with S.cerevisiae AWRI 1537 had also consistently a low concentrationof tannins (887 mg/L epicatechin equivalents average over 2009and 2010) but was different from that fermented with S. bayanusAWRI 1375 in that it was low in non-bleachable pigments. Arange of intermediate values of tannins and colour werereported for the strains AWRI 1575, 1375, 1493, 796, 1483 and1620, many of which are commercially available.

While Cabernet Sauvignon and Shiraz traditionally have amoderate level of tannins available in the fruit, Pinot Noir canbe limited both in tannins and colour. The low skin to seedtannin ratio and the less diverse anthocyanin profile can makeit difficult to achieve higher concentration of wine tannins andstable wine colour. This has led to a range of investigations intoways to improve the colour stability and concentration andcomposition of tannins in Pinot Noir wines. Yeast selection hasbeen shown to be an effective tool in diversifying these charac-teristics (Carew et al. 2013). The strain S. cerevisae EC1118(AWRI 838) was compared as a control treatment against:inoculation at day 0 with strain RC212 (common in Pinot Noirwinemaking); a ‘wild’ ferment that was subsequently inocu-lated at day 3 with EC1118; a day 0 inoculation with S. bayanusAWRI 1176; and a day 0 inoculation with Torulaspora delbrueckiisubsequently inoculated at day 3 with S. cerevisae EC1118 (AWRI838). Importantly, this study also assessed the persistence of thepost-ferment effects at 6 months of age. The wines from RC212showed significantly higher concentration of tannins post-ferment and at 6 months relative to that of the wild-initiatedferment and S. bayanus AWRI 1176 treatments (which had 70%



and 60% less tanninss, respectively, at 6 months). Althoughlower in tannin, the two sequential inoculations had a higherproportion of trihydroxylated tannin subunits suggesting theymay have a higher proportion of skin tannins. Wines fermentedwith RC212 had a relatively higher component of galloylatedsubunits indicating a higher relative proportion of seed tanninsubunits, highlighting the impact that yeast selection can haveon composition of the tannins, not just concentration.

The variability observed in the concentration and composi-tion of tannins for these studies may stem from several mecha-nisms. Different rates of fermentation and of ethanolicextraction may account for some of the observations, althoughin the Shiraz, Cabernet Sauvignon and Pinot Noir studies dis-cussed, all ferments had the same length of skin contact so thisdoes not account for the differences reported. Enzyme activity ofwine yeast has also been linked to the extraction of compoundsfrom grape skins, and may play a role. The variable increase inpigmented polymer formation has been ascribed to the evolu-tion of reactive intermediates such as aldehydes that can directlylink phenolic substances and can also create polymeric tanninsthat undergo subsequent rearrangement and modificationduring ageing. Acetaldehyde-mediated linkages that result inethyl-linked bridges are one such example, where these inter-mediate polymers subsequently undergo degradation and rear-rangement to new polymeric forms. As discussed previously, agrowing body of literature demonstrates that the relationshipbetween the concentration of tannins, ethanol concentrationand pomace contact time is complex. Extraction of tannins isinfluenced by: the physical breakdown of grape solids whichaffects its adsorption; differential yeast adsorption of tanninsfrom the liquid phase of wine; variable expression by yeast ofenzymes contributing to the release of tannins from the grapematrix (e.g. β-glucosidase, pectinase, proteolytic enzymes); andthe colloidal stability of soluble macromolecules that bind totannins. What is clear is that the phenolic style of red wines canbe significantly modulated by choice of commercially availablewine yeast, and ongoing research is required to determine themechanisms by which these differences are elicited.

MannoproteinsMannoproteins, naturally present in wines and derived fromthe cell walls of S. cerevisae, are increasingly being added inoenological products to wines with the intention of preventingtartrate instability or modulating mouthfeel. In red wines theyhave the potential to interact with tannins and other phenolicsubstances through the formation of colloids of relativelyunknown stability and, as such, there is interest in the effect ofmannoprotein addition on colour effects and tannins. Low tomedium molecular mass mannoproteins have been shown to bemore effective than high molecular mass mannoproteins at lim-iting particle growth of seed tannins in model wine conditions(pH 3.4 buffers containing 2 g/L tartaric acid, 12% ethanol)(Poncet-Legrand et al. 2007), but knowledge gaps remain ontheir effects on colloids in red wine. Mannosylated yeastinvertase was shown to have tenfold lower binding affinity fortannins than bovine serum albumin (BSA), but in model winesthey may have greater solution stability than that of other yeastproteins (Rowe et al. 2010).

Early mannoprotein research focused on colour effects, butmore recent reports have investigated in more detail the impacton the concentration and composition of tannins. Two commer-cial preparations containing yeast mannoproteins were added tothree Portuguese wines after malolactic fermentation (MLF) at0.2 g/L and 0.4 g/L (Rodrigues et al. 2012) and aged for 21

months. The wines were also subjected to an ‘accelerated’ageing test at 35°C. The commercial mannoprotein products didnot have an effect on colour stabilisation in these wines and, ingeneral, the overall evolution of the composition of tannins didnot differ significantly relative to that of the control with noaddition. One of the commercial mannoproteins limited thechange of grape tannins with mDP between 8 and 14. Many ofthe tannins present after fermentation chemically rearrangeduring ageing into new forms of ‘wine’ tannins that are notdirectly accounted for through acid-catalysed depolymerisation,except through the ‘mass conversion yield’ parameter. Thisparameter was not reported, but the authors of this reviewadvocate that it should be as it allows an estimate of the rear-rangements of tannins. Nonetheless, the mass conversion yieldis relatively unchanged in this study, likely as a result of the lowvariance in the proportion of subunits reported for the tanninsin the ‘accelerated’ ageing test.

By contrast, addition of mannoproteins at the start ofwinemaking has resulted in a decrease in the concentration ofwine proanthocyanidins and in wine stable colour (Guadalupeand Ayestaran 2008) but with no effect on monomeric phenolicsubstances and anthocyanins. The concomitant decrease inmannoproteins led the authors to propose a destabilisation ofpolysaccharide–tannin colloids for the loss of tannins, and whilethis appears likely, no direct evidence is provided for such col-loidal instability in that work. The composition of tannins wasnot assessed nor was the impact on sensory properties. Previousresearch (Guadalupe et al. 2007) with a similar experimentaldesign (mannoprotein addition at the start of winemaking) alsoshowed a decrease in non-bleachable colour, colour intensityand in the concentration of wine tannins, but sensory evalua-tion showed a decrease in astringency and an increase of thewine sweetness and roundness. A recent study (Rinaldi et al.2012) on the impact of mannoproteins on sensory and salivaprecipitation has reinforced earlier findings that mannoproteinsdecrease the perception of astringency in red wines.

OenotanninsThe impact of oenotannin addition on wine has been recentlyreviewed (Versari et al. 2013), with limited literature published inthe interim. One key observation is that, in general, oenotanninshave little impact on colour stabilisation regardless of timing, dose,oenotannin type, grape cultivar or maturity. Occasionally colourimpacts are observed soon after completion of fermentation, butthey are often not maintained through ageing (and in some casesthe experimental wines were not assessed after ageing). In the fewreports where the sensory impact of addition of tannins wasevaluated, their impact on astringency was often observed, leadingto the conclusion that oenotannin addition can affect mouthfeelproperties. The nature of these mouthfeel properties needs to beassessed individually, however, as the composition of theoenotannins is highly variable and in some wines with the addi-tion of a high dose, the sensory impact was considered as negative(Harbertson et al. 2012).

Recent research (Bautista-Ortín et al. 2015) has providedfurther insight into the dynamics of what may happen tooenotannins when they are added. The study analysed theimpact of cell walls on the concentration and composition ofcommercial oenotannins, reinforcing the earlier discussionabout interactions between tannins and cell-wall material fromgrape skin and pulp that could eliminate tannins (particularlylarger tannins) from must through adsorption and phase sepa-ration. They propose that oenotannins should be added to winewhen the cell-wall material suspended in the must is low (e.g. at



the end of alcoholic fermentation or after pressing) especially forcultivars with high binding capacity cell walls and thatoenotannins with a smaller proportion of high molecular masstannins should be used to reduce the impact on loss of tannins.This reinforces other observations made using purified grapetannins (Bindon et al. 2010a,b, Bindon and Smith 2013).

FiningThe mechanisms of interaction between proteins and phenolicsubstances, including tannins, have been thoroughly reviewed(De Freitas and Mateus 2012). The authors noted that the draw-back of some of the earlier literature investigating phenolicsubstance protein interactions was the use of methods thatlacked specificity and sensitivity. Some recent wine-focusedapplications have been reported that do use improved methodsand as such merit discussion.

Animal proteinsGelatin is widely used for fining wines, and several key refer-ences report the effect on concentration and composition oftannins. The general observation from early research was thathigher molecular mass tannins are removed preferentially, andthe tannins removed tend to be more highly galloylated(Sarni-Manchado et al. 1999, Maury et al. 2001). Differenttypes of gelatin removed different amounts of tannin (9–16%)depending on the wine and the gelatin composition. Oneknowledge gap left from these two reports is that they measuredonly tannin that was able to depolymerise under acid-catalysedthiolysis conditions and because there is often a large proportionof tannins that cannot be depolymerised, these tannins are leftunaccounted for when using only this method. Gel permeationchromatography of wine tannins allows a more accurate assess-ment of size and complements the information available fromacid-catalysed depolymerisation. The combination of bothmethods in addition to quantitation by precipitation with BSAand RP-HPLC has been used to assess the effect of gelatin andegg albumin in a Pinotage wine (Oberholster et al. 2013). Thisresearch showed that both fining agents decreased the concen-tration of tannins, although to varying degrees depending onthe analytical method selected to measure the tannins, empha-sising the need to understand the interrelation of analyticalmethods. Again, preferential removal of galloylated tannins wasshown and removal of larger molecular mass (MM) species(∼25% decrease in mDP) was demonstrated by both gel per-meation chromatography and acid-catalysed depolymerisationmethods. A wider range of fining agents (potassium caseinate,isinglass, egg albumin and three gelatins) and of dosage wasassessed using similar methods, with the additional reporting ofthe mass conversion yield effect on the tannins (Bindon andSmith 2013). Removal of tannins at the maximal dose rangedbetween 9 and 19% and, again, higher MM tannins were pref-erentially removed. The effect of these proteins was also com-pared against plant fibres, as discussed subsequently. A similarselection of proteins (egg albumin, isinglass, gelatin, casein,potassium caseinate) was assessed by fractionating monomeric,oligomeric and polymeric phenolic substances that were quan-tified using the vanillin assay and by performing acid-catalyseddepolymerisation (Cosme et al. 2009). This showed a decreasein mDP between 6 and 14% for the polymeric fraction for allfining agents and, similarly to the work in Pinotage, ∼ 25%decrease in mDP for egg albumin. Swim bladder isinglass wasfound to be more effective than fish skin isinglass. Caseinremoved the most monomers. Treatment of four wines withfour fining agents (bentonite, gelatin, gluten protein, egg

albumin) decreased tannins by ∼10% as assessed using twomethods with lower specificity, but no compositional informa-tion was determined (González-Neves et al. 2014).

Plant-based fining agentsThere is increased interest in finding alternatives to animalproteins for use as fining agents in wine. Initial observations ofthe binding affinity of apple cell wall material for tannins(Renard et al. 2001) have led researchers to report on the effec-tiveness of plant cell wall materials from apples and grapes aswine fining agents [Bindon and Smith (2013), Guerrero et al.(2013), Bautista-Ortín et al. (2015) and references therein].Such plant cell walls have proved to be effective fining agents,with apple cell walls achieving reduction in tannins as high as42% and grape fibres as high as 38% (Bindon and Smith 2013).Apple and grape fibres generally show the characteristic prefer-ence for higher MM tannins but grape fibres sometimes removeboth high and low MM tannins. The number of reports in thisarea is large and comprehensive review is beyond the scope ofthe current review. The impact of cell walls on the extractabilityof tannins in wine has been reviewed (Hanlin et al. 2010) ashas, more broadly, the interactions of phenolic substances withmacromolecules (Le Bourvellec and Renard 2012b).

A range of plant proteins has also been assessed. Patatin, aglycoprotein from potato, performed effectively with ∼10% reduc-tion in tannin concentration, decreased astringency and effective-ness similar to gelatin but better than egg albumin and casein andwith little effect on colour (Gambuti et al. 2012). Gluten and yeastextract protein have been claimed as effective but despite measur-ing tannins by colorimetry in hot acid, the authors did not reportthe values; however, the total phenolic index was reduced(Iturmendi et al. 2010). Corn proteins have also showed effective-ness at removing tannins at a level between 6 and 24% dependingon the dose or protein composition (Simonato et al. 2009). Pro-teins from soybean, pea, lentil flour and gluten have also beenapplied to wines and the impact on tannins from dimer to decamerwas assessed using Matrix Assisted Laser Desorption IonisationMass Spectrometry MS. In a model solution of oligomericprocyanidins, lentil flour was the most effective (16% decrease)followed by gluten, soy and pea proteins (Granato et al. 2010).

Impact of wine filtrationFiltering red wines prior to bottling is considered essential bymany winemakers for maintaining clarity and stability in thefinished wine (El Rayess et al. 2011) as well as removingresidual fining agents (Deckwart et al. 2014). Wines are gener-ally first treated with more coarse filtration membranes suchas pad filtration with hydrophilic polyvinylidene fluoride(Bohanan et al. 2012) or cross-flow filtration (El Rayess et al.2012a,b) and can then be filtered through a series of mem-branes with decreasing pore size (Ulbricht et al. 2009). Filteringred wines can be a source of concern for winemakers for twomain reasons. First, filtering red wines in particular can foul themembranes and this brings extra costs associated with the timerequired for changing membranes as well as the cost of themembranes themselves. Second, filtering is perceived to alterthe texture and mouthfeel of wine and can lead to the phenom-enon of ‘bottle-shock’ – a period of altered sensory characters inthe product. Research into filtration effects has focused on thesensory impact of wine filtration as well as the cause of mem-brane fouling and thus how fouling can be predicted and miti-gated either in the wine or in the membrane manufacture.

The extent to which a wine will foul a membrane dependson the wine colloidal properties and the type of membraneused in the filtration. Red wine colloids include tannins,



polysaccharides and tannin–polysaccharide complexes (ElRayess et al. 2012a,b). The concentration of tannins has beenfound to decrease significantly after fining with cross-flowmembranes (El Rayess et al. 2012a, Oberholster et al. 2013),suggesting that tannins are involved in membrane fouling. Ahigher concentration of tannins in wine also significantlydecreased the rate of flux in wines passing through a ceramiccross-flow membrane which further implied that high concen-tration of tannins in wine (greater than 1.25 g/L) could poten-tially foul membranes (El Rayess et al. 2012a,b). Thecontribution of tannins to membrane fouling is not consideredas significant as that of polysaccharides, particularly pectins,which have been shown to form a gel-like coating over cross-flow membranes, and mannoproteins (Vernhet and Moutounet2002, El Rayess et al. 2012a,b). Cross-flow filtration can alsoalter tannin composition, with filtered wines showing adecrease in size of tannins (mDp) by up to 25% (Oberholsteret al. 2013).

Different types of membranes used in wine filtration havedifferent surface properties that can also influence the extent towhich tannins bind to filtration membranes (Vernhet andMoutounet 2002, Ulbricht et al. 2009). Model wines sterile fil-tered with membranes made of polyethersulfone (PES) demon-strated lower fluxes and a greater proportion of adsorbedtannins and polysaccharides than the same wine filtered withpolypropylene membranes (Ulbricht et al. 2009). Other studieshave demonstrated that PES membranes bind significantlyfewer tannins than membranes made from polyvinylpyr-rolidone (Schroën et al. 2010). The reason for the differenttannin-binding capacity of filtration membranes relates to dif-ferences in the surface properties. Membranes with greaterpolarity have greater interaction with phenolic substancesbecause of greater hydrogen bonding (Vernhet and Moutounet2002, Schroën et al. 2010). Research into ways of modifying thesurface properties of membranes may therefore reduce theextent of membrane fouling by tannins.

The impact of filtration on the concentration and composi-tion of tannins has prompted much research into the sensoryimpacts of red wine filtration. Several studies have noted that,despite the decrease in the concentration and in size distributionof tannins of filtered wines, there is negligible difference intexture and mouthfeel between unfiltered control wines andeither cross-flow filtered or sterile-filtered red wines, regardlessof the membrane type used (Schobinger et al. 1992, Bohananet al. 2012, Buffon et al. 2014). This suggests that when consid-ering the wine production chain, the inconvenience of mem-brane fouling may be a greater issue than any loss of mouthfeelof red wines.

Methods for reducing the potential of red wines to foulmembranes include treating wines with pectinolytic enzymesprior to filtration (El Rayess et al. 2012a,b) and changing themembrane surface to minimise tannin interaction (Vernhet andMoutounet 2002, Schroën et al. 2010). Further research in thisarea is required to understand better the role of tannins andwine colloids in membrane fouling in order to develop methodsthat can predict the membrane-fouling capacity of a red wineprior to filtration. More research is also required to understandthe long-term effects of filtration on wine colloid structure andmouthfeel.

Oxygen exposure, barrel treatment, bottling andaccelerated-ageing techniquesAgeing red wines has long been used to allow flavours todevelop and astringency to mellow (Chira et al. 2012). Greaterastringency intensity is directly associated with higher concen-

tration and larger molecular size of tannins (Vidal et al. 2003),so the reasons for the change in wine astringency with ageinghave been suggested to involve a decrease in the concentrationof tannins because of precipitation and a decrease in molecularsize of tannins because of subunit cleavage (Cheynier et al.2006, Chira et al. 2012). Aged red wines, up to 50 years old,however, can have concentration and average molecular size oftannins similar to that of tannins of younger wines (McRae et al.2012, Bindon et al. 2014) and yet have lower astringency. Thissuggests that other changes have occurred to the structure of thetannin molecules that cause the decrease in wine astringency(McRae et al. 2013). The cost of maintaining barrels and long-term storage of wine has prompted much research into newtechnologies to accelerate the ageing process. This has involveddifferent methods of oxygen exposure, the use of oak staves,and ageing on wine lees (Tao et al. 2014). The impact of oxygen,barrel-ageing and bottle-ageing as well as the impact of themore common accelerated ageing techniques on the structureand development of tannins are discussed below.

The most significant change in the structure of tannins withageing involves oxidation and depolymerisation reactions.Oxygen reacts readily with phenolic substances as reviewed inOliveira et al. (2011). The presence of oxygen produces highlyreactive quinones from flavonoids and acetaldehyde fromethanol, which promote polymerisation of tannins because ofdirect and indirect condensation reactions between tannins andflavan-3-ols or anthocyanins (He et al. 2008). These reactionsincrease tannins size by incorporating more polymer subunits aswell as reducing the water solubility of the tannins because ofthe cross-linking of subunits through hydroxyl groups(Cheynier 2006, He et al. 2008, Poncet-Legrand et al. 2010).Structural rearrangement reactions also occur with wine ageingas a result of the low pH of wine. The chemical bonds betweentannin subunits—flavan-3-ols—are continually broken andreformed, which also changes the tannins structure in such away as to reduce the water solubility (Haslam 1980). This canlead to precipitation of tannins and thus sediment forming inthe bottle (Waters et al. 1994). The extent of the precipitation oftannins from solution can potentially be mediated by interac-tions with polysaccharides (Maury et al. 2001, Cheynier et al.2006) which can keep in solution the tannins that would haveotherwise precipitated. The structural modifications to tanninsoccur faster at lower pH (Kontoudakis et al. 2011, McRae et al.2013). As a result of these reactions, wine tannins are structur-ally different from the original grape tannins, and aged winetannins are different even from young wine tannins. The maindifference is that the number of bonds between subunits thatcan be broken by exposure to acid is significantly reduced as aresult of subunit cross-linking and the incorporation ofanthocyanins (He et al. 2008). In terms of analysis, thesechanges manifest as a decrease in the mDp, which is a way ofdetermining molecular size of tannins (Vernhet et al. 2011).This may have contributed to the assumption that tanninsbecome smaller with age and yet other techniques for sizemeasurements of tannins, including gel permeation chromatog-raphy and small-angle x-ray scattering, have indicated thattannins remain of similar (McRae et al. 2012) or slightly largersize with wine ageing (McRae et al. 2014a) while others showdecreased size with age (Bindon et al. 2014) and as such furtherresearch work is required to understand size and compositionchanges with age.

Wine astringency is positively associated with the concen-tration and molecular size of tannins (Vidal et al. 2003). Giventhat the changes in tannins that occur during red wine ageinghave limited impact on either of these parameters, it must be



concluded that the changes that occur in wine astringency withageing are because of other structural characteristics of tannins.Astringency is a tactile sensation that occurs largely as a result ofwine tannins interacting with salivary proteins and oral epithe-lial cells (Payne et al. 2009, De Freitas and Mateus 2012) and ismeasured in vitro by assessing the extent of the interactionbetween tannins and a model protein (Obreque-Slier et al.2010). Tannins isolated from wines that were about 10 years oldhave been shown to interact less strongly with proteins thantannins isolated from younger wines (McRae et al. 2010).Astringency studies have also indicated that pigmented poly-mers, those tannins that contain anthocyanins, are less astrin-gent than pigmented tannins (Vidal et al. 2004a). Thus thecombined effects of the structural changes that occur in tanninsduring wine ageing all contribute to the softening of astringencyduring red wine ageing.

Red wines traditionally undergo barrel ageing in French orAmerican oak prior to bottling. Ageing wines in barrels not onlyimparts favourable flavour compounds, particularly oaklactones and phenolic aldehydes, but the long-term exposure tooxygen through the pores in the oak induces changes in thetannins and thus in wine astringency (Cano-Lopez et al. 2008,Oberholster et al. 2015). The impact of barrel ageing on redwine will vary depending on the type of oak used. French oak ismore porous than American oak, allowing greater oxygeningress (Tao et al. 2014). Generally, the amount of oxygeningress through barrels has been estimated to be between 1.7and 2.5 mL/(L · month) (Cano-Lopez et al. 2008). Wine alsoextracts hydrolysable tannins from the oak, such asellagitannins, which are characterised as a glucose moietybound to multiple gallic acid subunits via ester linkages(McManus et al. 1985). The extraction of phenolic substancesfrom oak staves is low, with a concentration up to 250 mg/L(Quinn and Singleton 1985) compared to around 2000–4000 mg/L of tannin in red wines regardless of oak treatment(Herderich and Smith 2005). The extraction into white wines isalso reportedly below sensory threshold (Pocock et al. 1994),suggesting that the astringency and mouthfeel of red wines ispredominantly because of the condensed tannins from grapes.

The reduction in astringency intensity of red wine withbarrel ageing is therefore more likely to involve changes to thestructure of tannins because of gradual oxidation and ageingprocesses. Hydrolysable tannins have also been shown to beoxidised in preference to catechins, and produce a significantlylarger concentration of peroxides in wine, which promote thepolymerisation of condensed tannins (Vivas and Glories 1996).This suggests that although hydrolysable tannins play a limiteddirect role in wine astringency, their presence can influencewine astringency by promoting structural changes in winetannins. Oak cellulose can also adsorb phenolics (Barrera-Garciaet al. 2007), and the extent of this interaction depends upon theage of the oak barrel as well as the type of oak (Sánchez-Iglesiaset al. 2009). Adsorption of condensed tannins to oak can lowerthe concentration of tannins in the wine and this also contrib-utes to the reduction in overall astringency during barrel ageing.

Wine tannins undergo further changes during bottle ageing.Oxidation can occur gradually during bottle ageing as a result ofthe oxygen ingress through the bottle closure as well as theconsumption of the total package oxygen (TPO) (Ugliano et al.2012, McRae et al. 2013). Total package oxygen refers to theoxygen present in both in the bottle headspace and dissolved inthe wine during transfer and bottling and the greater the TPO,the greater the extent of oxidation reactions and the more rapidthe changes in the structure of tannins. The type of closure usedin the bottle will impact the amount of oxygen that the wine is

exposed to over time (Ugliano et al. 2012, Gambuti et al. 2013)with cork generally allowing greater oxygen ingress than screwcaps. Wines bottled under closures that allowed for greateroxygen ingress have been shown to have a reduced interactionwith protein than the same wines bottled under wines with lowoxygen permeation (Gambuti et al. 2013).

Common techniques to reduce the time involved in wineageing involve the controlled gradual application of oxygen towine using macro-oxygenation during alcoholic fermentationor micro-oxygenation (MOX) before or after MLF. Macro-oxygenation normally occurs during primary fermentationduring pump-overs although the amount of oxygen ingress canvary greatly depending on how the process is carried out(Moenne et al. 2014). In a more controlled environment, bub-bling large volumes of air through active ferments in rotaryfermenters has been shown to induce changes in tannins andastringency that are consistent with characteristics of agedwines (McRae et al. 2014b). These oxygen-treated wines dem-onstrated similar tannin characteristics after 2 months of ageingto those of the control wines after 2 years of ageing, and thedifferences between the control and oxygen-treated wines werestill significant after 2 years of bottle ageing (McRae et al.2014b). The oxygen-treated ferments contained a lower con-centration of tannins, and the composition of tannins showedlower molecular mass and mass conversion yield. Furtherresearch into controlled macro-oxygenation is warranted.

Exposing wines to small amounts of oxygen with MOX isincreasingly a popular technique for developing wine colourand texture, and much research has been conducted in this areaand reviewed recently (Gomez-Plaza and Cano-Lopez 2011,Schmidtke et al. 2011, Anli and Cavuldak 2012). Micro-oxygenation involves the controlled addition of small doses ofoxygen to wines in tanks, usually either pre-MLF [10–30 mL/(L· month)] or post-MLF [1–5 mL/(L · month)] (Gomez-Plaza andCano-Lopez 2011). The effect of MOX reportedly increasescolour stability through the formation of pigmented polymersand decreases astringency; however, results vary greatlydepending on wine composition, timing of MOX application,dosage and temperature (Gomez-Plaza and Cano-Lopez 2011,Oberholster et al. 2015). Micro-oxygenation has been shown tobe most effective on high phenolic wines and when additionswere made pre-MLF (Cano-Lopez et al. 2008). Combinationtreatments of MOX with oak staves are also more effective thanMOX alone in accelerating wine ageing as well as producingfavourable sensory attributes (Cano-Lopez et al. 2008,Sánchez-Iglesias et al. 2009, Oberholster et al. 2015). One of theeffects of adding oxygen to wine is the production of acetalde-hyde from ethanol, which promotes polymerisation of tanninsand the formation of pigmented polymers through ethyl link-ages. A different approach to accelerating wine ageing is thedirect addition of acetaldehyde as a tannin cross-linking agent(Sheridan and Elias 2015). This technique resulted in a decreasein the concentration of tannins and an increase in colour sta-bility, as expected with wine ageing, although the impact ofacetaldehyde addition on flavour and mouthfeel are yet to bedetermined.

Ageing on lees is another method for improving the devel-oped characteristics of a wine. As well as the aroma and flavourimpacts [summarised in Tao et al. (2014)], ageing on lees canchange the phenolic composition of wine. This is mostly becauseof the adsorption of phenolic substances to yeast cell walls andsterol in the cell membranes, resulting in the removal of sometannins and an overall decrease in the concentration of tanninsleading to lower astringency. Storing wines on lees also resultsin yeast autolysis, releasing polysaccharides which can reduce



wine astringency (Vidal et al. 2004b). Wines aged on lees incombination with MOX have been shown to have greatercolour stability and more pigmented polymers than eithermethod alone (Sartini et al. 2007, Tao et al. 2014). Other pro-cesses that have been investigated include the application ofelectric fields, gamma radiation and ultrasonic waves, whichhave been thoroughly reviewed by Tao et al. (2014). Moreresearch into combination treatments for accelerated ageing ofred wines may reduce the need for extended wine ageing.

Overall, wines of lower pH stored under a closure thatallows for greater oxygen ingress will develop more rapidly thanwines of higher pH and limited oxygen exposure. The applica-tion of oxygen to wines either as macro-oxygenation duringprimary fermentation or as MOX post-fermentation can inducecharacteristics of wine ageing more quickly. Understanding howred wine tannins change with ageing and how these changesimpact the astringency of wine is enabling new technologies tobe developed that shorten the ageing period of young red wines.

ConclusionsResearch undertaken to improve the understanding of theimpacts of winemaking practices on the concentration and com-position of tannins in red wines shows that significant impactsoccur at many points of the wine production process, includingthrough maceration, yeast selection, addition of mannoproteins,addition of oenotannins, fining by animal and plant proteins,filtration, oxygen exposure, barrel treatment, packaging/bottling and accelerated ageing techniques. A sufficient body ofevidence has developed in certain areas to make generalisations,but several other areas continue to show large variability oftannins in response to winemaking interventions depending onthe grapes and their particular methods of treatment. Progresshas been made in determining the underpinning mechanismsfor some of the effects, but significant further research isrequired to understand why many of the effects occur. Futureresearch will provide the opportunity for improved manage-ment of vineyards and winemaking to optimise tannins in grapeand wine, and for increased capacity to meet wine specification,consumer expectations and profitability.

AcknowledgementsThis work was supported by Australian grapegrowers andwinemakers through their investment body Wine Australia,with matching funds from the Australian Government. TheAustralian Wine Research Institute is a member of the WineInnovation Cluster in Adelaide.

ReferencesÁlvarez, I., Aleixandre, J.L., García, M.J. and Lizama, V. (2006) Impact of

prefermentative maceration on the phenolic and volatile compounds inMonastrell red wines. Analytica Chimica Acta 563, 109–115.

Anli, E. and Cavuldak, A. (2012) A review of microoxygenation applicationin wine. Journal of the Institute of Brewing 118, 368–385.

Apolinar-Valiente, R., Romero-Cascales, I., Williams, P., Gómez-Plaza, E.,López-Roca, J.M., Ros-García, J.M. and Doco, T. (2014) Effect ofwinemaking techniques on polysaccharide composition of CabernetSauvignon, Syrah and Monastrell red wines. Australian Journal of Grapeand Wine Research 20, 62–71.

Barrera-Garcia, V.D., Gougeon, R.D., Di Majo, D., De Aguirre, C., Voilley,A.E. and Chassagne, D. (2007) Different sorption behaviors for winepolyphenols in contact with oak wood. Journal of Agricultural and FoodChemistry 55, 7021–7027.

Bautista-Ortín, A.B., Fernández-Fernández, J.I., López-Roca, J.M. andGómez-Plaza, E. (2007a) The effects of enological practices inanthocyanins, phenolic compounds and wine colour and their depend-ence on grape characteristics. Journal of Food Composition and Analysis20, 546–552.

Bautista-Ortín, A.B., Romero-Cascales, I., Fernández-Fernández, J.I.,López-Roca, J.M. and Gómez-Plaza, E. (2007b) Influence of the yeaststrain on Monastrell wine colour. Innovations in Food Science. EmergingTechnologies 8, 322–328.

Bautista-Ortín, A.B., Jiménez-Pascual, E., Busse-Valverde, N., López-Roca,J.M., Ros-García, J.M. and Gómez-Plaza, E. (2013) Effect of wine macera-tion enzymes on the extraction of grape seed proanthocyanidins. Food andBioprocess Technology 6, 2207–2212.

Bautista-Ortín, A.B., Ruiz-García, Y., Marín, F., Molero, N.,Apolinar-Valiente, R. and Gómez-Plaza, E. (2015) Remarkableproanthocyanidin adsorption properties of Monastrell pomace cell wallmaterial highlight its potential use as an alternative fining agent in redwine production. Journal of Agricultural Food Chemistry 63, 620–633.

Bindon, K.A. and Smith, P.A. (2013) Comparison of the affinity and selec-tivity of insoluble fibres and commercial proteins for wineproanthocyanidins. Food Chemistry 136, 917–928.

Bindon, K., McCarthy, M. and Smith, P.A. (2014) Development of winecolour and non-bleachable pigments during the fermentation and ageingof (Vitis vinifera L. cv.) Cabernet Sauvignon wines differing in anthocyaninand tannin concentration. LWT – Food Science Technology 59, 923–932.

Bindon, K.A., Smith, P.A. and Kennedy, J.A. (2010a) Interaction betweengrape-derived proanthocyanidins and cell wall material. 1. Effect onproanthocyanidin composition and molecular mass. Journal of Agricul-tural and Food Chemistry 58, 2520–2528.

Bindon, K.A., Smith, P.A., Holt, H. and Kennedy, J.A. (2010b) Interactionbetween grape-derived proanthocyanidins and cell wall material. 2. Impli-cations for vinification. Journal of Agricultural and Food Chemistry 58,10736–10746.

Blazquez-Rojas, I., Smith, P.A. and Bartowsky, E.J. (2012) Influence ofchoice of yeasts on volatile fermentation-derived compounds, colour andphenolics composition in Cabernet Sauvignon wine. World Journal ofMicrobiological Biotechnology 28, 1–11.

Bohanan, L.P., Block, D. and Heymann, H. (2012) Evaluating the effects ofmembrane filtration on sensory and chemical properties of wine. Ameri-can Journal of Enology and Viticulture 63, 436A–436A.

Bosso, A., Panero, L., Petrozziello, M., Follis, R., Motta, S. and Guaita, M.(2012) Influence of submerged-cap vinification on polyphenolic compo-sition and volatile compounds of Barbera wines. American Journal ofEnology and Viticulture 62, 503–511.

Buffon, P., Heymann, H. and Block, D.E. (2014) Sensory and chemicaleffects of cross-flow filtration on white and red wines. American Journalof Enology and Viticulture 65, 305–314.

Busse-Valverde, N., Bautista-Ortin, A.B., Gómez-Plaza, E., Fernández-Fernández, J.I. and Gil-Munoz, R. (2012) Influence of skin macerationtime on the proanthocyanidin content of red wines. European FoodResearch and Technology 235, 1117–1123.

Busse-Valverde, N., Gómez-Plaza, E., López-Roca, J.M., Gil-Munoz, R. andBautista-Ortín, A.B. (2011) The extraction of anthocyanins andproanthocyanidins from grapes to wine during fermentative maceration isaffected by the enological technique. Journal of Agricultural and FoodChemistry 59, 5450–5455.

Busse-Valverde, N., Gómez-Plaza, E., López-Roca, J.M., Gil-Muñoz, R.,Fernández-Fernández, J.I. and Bautista-Ortín, A.B. (2010) Effect of differ-ent enological practices on skin and seed proanthocyanidins in threevarietal wines. Journal of Agricultural and Food Chemistry 58, 11333–11339.

Cadot, Y., Caillé, S., Samson, A., Barbeau, G. and Cheynier, V. (2012)Sensory representation of typicality of Cabernet franc wines related tophenolic composition: impact of ripening stage and maceration time.Analytica Chimica Acta 732, 91–99.

Cano-Lopez, M., Bautista-Ortin, A.B., Pardo-Minguez, F., Lopez-Roca, J.M.and Gomez-Plaza, E. (2008) Sensory descriptive analysis of a red wineaged with oak chips in stainless steel tanks or used barrels: effect of thecontact time and size of the oak chips. Journal of Food Quality 31,645–660.

Carew, A.L., Gill, W., Close, D.C. and Dambergs, R.G. (2014a) Microwavemaceration with early press off improves phenolics and fermentationkinetics in Pinot Noir. American Journal of Enology and Viticulture 65,401–406.

Carew, A.L., Smith, P.A., Close, D.C., Curtin, C. and Dambergs, R.G. (2013)Yeast effects on Pinot Noir wine phenolics, color, and tannin composition.Journal of Agricultural and Food Chemistry 61, 9892–9898.

Carew, A.L., Sparrow, A.M., Curtin, C.D., Close, D.C. and Dambergs, R.G.(2014b) Microwave maceration of Pinot Noir grape must: sanitation andextraction effects and wine phenolics outcomes. Food and BioprocessTechnology 7, 954–963.

Casassa, L.F. and Harbertson, J.F. (2014) Extraction, evolution, and sensoryimpact of phenolic compounds during red wine maceration. AnnualReview of Food Science and Technology 5, 83–109.



Casassa, L.F., Beaver, C.W., Mireles, M.S. and Harbertson, J.F. (2013a) Effectof extended maceration and ethanol concentration on the extraction andevolution of phenolics, color components and sensory attributes ofMerlot wines. Australian Journal of Grape and Wine Research 19, 25–39.

Casassa, L.F., Larsen, R.C., Beaver, C.W., Mireles, M.S., Keller, M., Riley,W.R., Smithyman, R. and Harbertson, J.F. (2013b) Impact of extendedmaceration and regulated deficit irrigation (RDI) in Cabernet Sauvignonwines: characterization of proanthocyanidin distribution, anthocyaninextraction, and chromatic properties. Journal of Agricultural and FoodChemistry 61, 6446–6457.

Cerpa-Calderón, F.K. and Kennedy, J.A. (2008) Berry integrity and extrac-tion of skin and seed proanthocyanidins during red wine fermentation.Journal of Agricultural and Food Chemistry 56, 9006–9014.

Cheynier, V. (2006) Flavonoids in wine. Andersen, O.M. and Markham,K.R., eds. Flavonoids – chemistry, biochemistry and applications (CRCPress: Boca Raton, FL, USA) pp. 263–318.

Cheynier, V., Remy, S. and Fulcrand, H. (2000) Mechanisms of anthocyaninand tannin changes during winemaking and aging. Rantz, J.M., ed. Pro-ceedings of the American Society of Enology and Viticulture 50th Anni-versary Annual Meeting; 19–23 June 2000; Seattle, WA, USA (AmericanSociety of Enology and Viticulture: Davis, CA, USA) pp. 337–344.

Cheynier, V., Duenas-Paton, M., Salas, E., Maury, C., Souquet, J.M.,Sarni-Manchado, P. and Fulcrand, H. (2006) Structure and properties ofwine pigments and tannins. American Journal of Enology and Viticulture57, 298–305.

Chira, K., Jourdes, M. and Teissedre, P.L. (2012) Cabernet Sauvignon redwine astringency quality control by tannin characterization and polym-erization during storage. European Food Research and Technology 234,253–261.

Cholet, C., Delsart, C., Petrel, M., Gontier, E., Grimi, N., L’Hyvernay, A.,Ghidossi, R., Vorobiev, E., Mietton-Peuchot, M. and Geny, L. (2014)Structural and biochemical changes induced by pulsed electric field treat-ments on Cabernet Sauvignon grape berry skins: impact on cell wall totaltannins and polysaccharides. Journal of Agricultural and Food Chemistry62, 2925–2934.

Cosme, F., Ricardo-da-Silva, J.M. and Laureano, O. (2009) Effect of variousproteins on different molecular weight proanthocyanidin fractions of redwine during wine fining. American Journal for Enology and Viticulture60, 74–81.

De Beer, D., Joubert, E., Marais, J. and Manley, M. (2006) Macerationbefore and during fermentation: effect on Pinotage wine phenolic compo-sition, total antioxidant capacity and objective colour parameters. SouthAfrican Journal for Enology and Viticulture 27, 137–150.

De Freitas, V. and Mateus, N. (2012) Protein/polyphenol Interactions: pastand present contributions. Mechanisms of astringency perception. CurrentOrganic Chemistry 16, 724–726.

Deckwart, M., Carstens, C., Webber-Witt, M., Schäfer, V., Eichhorn, L.,Schröter, F., Fischer, M., Brockow, K., Christmann, M. andPaschke-Kratzin, A. (2014) Impact of wine manufacturing practice on theoccurrence of fining agents with allergenic potential. Food additives andcontaminants part A. Chemical Analysis, Control, Exposure and RiskAssessment 31, 1805–1817.

Delsart, C., Ghidossi, R., Poupot, C., Cholet, C., Grimi, N., Vorobiev, E.,Milisic, V. and Peuchot, M.M. (2012) Enhanced extraction of valuablecompounds from Merlot grapes by pulsed electric field. American Journalof Enology and Viticulture 63, 205–211.

Delsart, C., Cholet, C., Ghidossi, R., Grimi, N., Gontier, E., Gény, L.,Vorobiev, E. and Mietton-Peuchot, M. (2014) Effects of pulsed electricfields on Cabernet Sauvignon grape berries and on the characteristics ofwines. Food and Bioprocess Technology 7, 424–436.

Doco, T., Williams, P. and Cheynier, V. (2007) Effect of flash release andpectinolytic enzyme treatments on wine polysaccharide composition.Journal of Agricultural and Food Chemistry 55, 6643–6649.

Ducasse, M.A., Canal-Llauberes, R.M., de Lumley, M., Williams, P.,Souquet, J.M., Fulcrand, H. and Cheynier, V. (2010) Effect of maceratingenzyme treatment on the polyphenol and polysaccharide composition ofred wines. Food Chemistry 118, 369–376.

El Rayess, Y., Albasi, C., Bacchin, P., Taillandier, P., Mietton-Peuchot, M. andDevatine, A. (2012a) Analysis of membrane fouling during cross-flowmicrofiltration of wine. Innovative Food Science and Emerging Technolo-gies 16, 398–408.

El Rayess, Y., Albasi, C., Bacchin, P., Taillandier, P., Mietton-Peuchot, M. andDevatine, A. (2012b) Cross-flow microfiltration of wine: effect ofcolloids on critical fouling conditions. Journal of Membrane Science 385,177–186.

El Rayess, Y., Albasi, C., Bacchin, P., Taillandier, P., Raynal, J.,Mietton-Peuchot, M. and Devatine, A. (2011) Cross-flow microfiltrationapplied to oenology: a review. Journal of Membrane Science 382, 1–19.

Fontoin, H., Saucier, C., Teissedre, P.-L. and Glories, Y. (2008) Effect of pH,ethanol and acidity on astringency and bitterness of grape seed tanninoligomers in model wine solution. Food Quality and Preference 19, 286–291.

Gambuti, A., Rinaldi, A. and Moio, L. (2012) Use of patatin, a proteinextracted from potato, as alternative to animal proteins in fining of redwine. European Food Research and Technology 235, 753–765.

Gambuti, A., Rinaldi, A., Ugliano, M. and Moio, L. (2013) Evolution ofphenolic compounds and astringency during aging of red wine: effect ofoxygen exposure before and after bottling. Journal of Agricultural andFood Chemistry 61, 1618–1627.

Gawel, R. (1998) Red wine astringency: a review. Australian Journal ofGrape and Wine Research 4, 74–95.

Gil, M., Kontoudakis, N., González, E., Esteruelas, M., Fort, F., Canals, J.M.and Zamora, F. (2012) Influence of grape maturity and maceration lengthon color, polyphenolic composition, and polysaccharide content ofCabernet Sauvignon and Tempranillo wines. Journal of Agricultural andFood Chemistry 60, 7988–8001.

Gomez-Plaza, E. and Cano-Lopez, M. (2011) A review on micro-oxygenation of red wines: claims, benefits and the underlying chemistry.Food Chemistry 125, 1131–1140.

González-Neves, G., Favre, G. and Gil, G. (2014) Effect of fining on thecolour and pigment composition of young red wines. Food Chemistry 157,385–392.

González-Neves, G., Gil, G., Favre, G., Baldi, C., Hernández, N. andTraverso, S. (2013) Influence of winemaking procedure and grape varietyon the colour and composition of young red wines. South African Journalof Enology and Viticulture 34, 138–146.

Granato, T.M., Piano, F., Nasi, A., Ferranti, P., Iametti, S. and Bonomi, F.(2010) Molecular basis of the interaction between proteins of plant originand proanthocyanidins in a model wine System. Journal of Agriculturaland Food Chemistry 58, 11969–11976.

Guadalupe, Z. and Ayestaran, B. (2008) Effect of commercial mannoproteinaddition on polysaccharide, polyphenolic, and color composition in redwines. Journal of Agricultural and Food Chemistry 56, 9022–9029.

Guadalupe, Z., Palacios, A. and Ayestaran, B. (2007) Maceration enzymesand mannoproteins: a possible strategy to increase colloidal stability andcolor extraction in red wines. Journal of Agricultural and Food Chemistry55, 4854–4862.

Guerrero, R.F., Smith, P. and Bindon, K.A. (2013) Application of insolublefibers in the fining of wine phenolics. Journal of Agricultural and FoodChemistry 61, 4424–4432.

Hanlin, R.L., Hrmova, M., Harbertson, J.F. and Downey, M.O. (2010)Review: condensed tannin and grape cell wall interactions and theirimpact on tannin extractability into wine. Australian Journal of Grape andWine Research 16, 173–188.

Harbertson, J.F., Parpinello, G.P., Heymann, H. and Downey, M.O. (2012)Impact of exogenous tannin additions on wine chemistry and winesensory character. Food Chemistry 131, 999–1008.

Harbertson, J.F., Mireles, M.S., Harwood, E.D., Weller, K.M. and Ross, C.F.(2009) Chemical and sensory effects of saignée, water addition, andextended maceration on high brix must. American Journal of Enology andViticulture 60, 450–460.

Haslam, E. (1980) In vino veritas – oligomeric procyanidins and the aging ofred wines. Phytochemistry 19, 2577–2582.

Hayasaka, Y., Birse, M., Eglinton, J. and Herderich, M. (2007) The effect ofSaccharomyces cerevisiae and Saccharomyces bayanus yeast on colour proper-ties and pigment profiles of a Cabernet Sauvignon red wine. AustralianJournal of Grape and Wine Research 13, 176–185.

He, F., Pan, Q.H., Shi, Y. and Duan, C.Q. (2008) Chemical synthesis ofproanthocyanidins in vitro and their reactions in aging wines. Molecules13, 3007–3032.

Herderich, M.J. and Smith, P.A. (2005) Analysis of grape and wine tannins:methods, applications and challenges. Australian Journal of Grape andWine Research 11, 205–214.

Hernández-Jiménez, A., Kennedy, J.A., Bautista-Ortín, A.B. andGómez-Plaza, E. (2012) Effect of ethanol on grape seed proanthocyanidinextraction. American Journal of Enology and Viticulture 63, 57–61.

Holt, H., Cozzolino, D., McCarthy, J., Abrahamse, C., Holt, S., Solomon, M.,Smith, P.A., Chambers, P.J. and Curtin, C. (2013) Influence of yeast strainon Shiraz wine quality indicators. International Journal of Food Microbi-ology 3, 302–311.

Ichikawa, M., Ono, K., Hisamoto, M., Matsudo, T. and Okuda, T. (2012)Effect of cap management technique on the concentration ofproanthocyanidins in Muscat Bailey wine. Food Science and TechnologyResearch 18, 201–207.

Iturmendi, N., Duran, D. and Marin-Arroyo, M.R. (2010) Fining of redwines with gluten or yeast extract protein. International Journal of FoodScience and Technology 45, 200–207.



Kennedy, J.A. and Jones, G.P. (2001) Analysis of proanthocyanidin cleavageproducts following acid-catalysis in the presence of excess phloroglucinol.Journal of Agricultural and Food Chemistry 49, 1740–1746.

Kennedy, J.A., Troup, G.J., Pilbrow, J.R., Hutton, D.R., Hewitt, D., Hunter,C.R., Ristic, R., Iland, P.G. and Jones, G.P. (2000) Development of seedpolyphenols in berries from Vitis vinifera L. cv. Shiraz. Australian Journal ofGrape and Wine Research 6, 244–254.

Kilmister, R.L., Mazza, M., Baker, N.K., Faulkner, P. and Downey, M.O.(2014) A role for anthocyanin in determining wine tannin concentrationin Shiraz. Food Chemistry 152, 475–482.

Kontoudakis, N., González, E., Gil, M., Esteruelas, M., Fort, F., Canals, J.M.and Zamora, F. (2011) Influence of wine pH on changes in color andpolyphenol composition by micro-oxygenation. Journal of Agriculturaland Food Chemistry 59, 1974–1984.

Le Bourvellec, C. and Renard, C.M.G. (2012b) Interactions betweenpolyphenols and macromolecules: quantification methods and mecha-nisms. Critical Reviews in Food Science and Nutrition 52, 213–248.

Le Bourvellec, C., Watrelot, A.A., Ginies, C., Imberty, A. and Renard, C.M.(2012a) Impact of processing on the noncovalent interactions betweenprocyanidin and apple cell wall. Journal of Agricultural and Food Chem-istry 60, 9484–9494.

Lerno, L.A., Reichwage, M., Ponangi, R., Hearne, L., Block, D.E. andOberholster, A. (2015) Effects of cap and overall fermentationtemperature on phenolic extraction in cabernet sauvignon fermentations.American Journal of Enology and Viticulture doi: 10.5344/ajev.2015.14129.

Maury, C., Sarni-Manchado, P., Lefebvre, S., Cheynier, V. and Moutounet,M. (2001) Influence of fining with different molecular weight gelatins onproanthocyanidin composition and perception of wines. AmericanJournal of Enology and Viticulture 52, 140–145.

McManus, J.P., Davis, K.G., Beart, J.E., Gaffney, S.H., Lilley, T.H. andHaslam, E. (1985) Polyphenol interactions. Part 1. Introduction; someobservations on the reversible complexation of polyphenols with proteinsand polysaccharides. Journal of the Chemical Society, Perkin Transactions2 9, 1429–1438.

McRae, J.M., Falconer, R.J. and Kennedy, J.A. (2010) Thermodynamics ofgrape and wine tannin interaction with polyproline: implications for redwine astringency. Journal of Agricultural and Food Chemistry 58, 12510–12518.

McRae, J.M., Dambergs, R., Kassara, S., Parker, M., Jeffery, D.W., Herderich,M. and Smith, P.A. (2012) Phenolic compositions of 50 and 30 yearsequences of Australian red wines: the impact of wine age. Journal ofAgricultural and Food Chemistry 60, 10093–10102.

McRae, J.M., Schulkin, A., Kassara, S., Holt, H.E. and Smith, P.A. (2013)Sensory properties of wine tannin fractions: implications for in-mouthsensory properties. Journal of Agricultural and Food Chemistry 61, 719–727.

McRae, J.M., Kirby, N.M., Mertens, H.D.T., Kassara, S. and Smith, P.A.(2014a) Measuring the molecular dimensions of wine tannins: compari-son of small-angle X-ray scattering, gel-permeation chromatography andmean degree of polymerization. Journal of Agricultural and Food Chem-istry 62, 7216–7224.

McRae, J.M., Day, M., Bindon, K., Kassara, S., Schmidt, S., Schulkin, A.,Kolouchova, R. and Smith, P.A. (2014b) Effect of early oxygen exposureon red wine colour and tannins. Tetrahedron 71, 3131–3137.

Moenne, M.I., Saa, P., Laurie, V.F., Pérez-Correa, J.R. and Agosin, E. (2014)Oxygen incorporation and dissolution during industrial-scale red winefermentations. Food Bioprocess Technology 7, 2627–2636.

Morel-Salmi, C., Souquet, J.M., Bes, M. and Cheynier, V. (2006) Effect offlash release treatment on phenolic extraction and wine composition.Journal of Agricultural and Food Chemistry 54, 4270–4276.

Moreno-Pérez, A., Fernández-Fernández, J.I., Bautista-Ortín, A.B.,Gómez-Plaza, E., Martínez-Cutillas, A. and Gil-Muñoz, R. (2013) Influ-ence of winemaking techniques on proanthocyanidin extraction inMonastrell wines from four different areas. European Food Research andTechnology 236, 473–481.

Nel, A.P., van Rensburg, P. and Lambrechts, M.G. (2014) The influence ofdifferent winemaking techniques on the extraction of grape tannins andanthocyanins. South African Journal of Enology and Viticulture 35, 304–320.

Oberholster, A., Carstens, L.M. and du Toit, W.J. (2013) Investigation of theeffect of gelatine, egg albumin and cross-flow microfiltration on the phe-nolic composition of Pinotage wine. Food Chemistry 138, 1275–1281.

Oberholster, A., Elmendorf, B., Lerno, L., King, E., Heymann, H.,Brenneman, C. and Boulton, R.B. (2015) Barrel maturation, oak alterna-tives and micro-oxygenation: influence on red wine aging and quality.Food Chemistry 173, 1250–1258.

Obreque-Slier, E., López-Solís, R., Peña-Neira, A. and Zamora-Marín, F.(2010) Tannin-protein interaction is more closely associated with astrin-

gency than tannin-protein precipitation: experience with two oenologicaltannins and a gelatin. International Journal of Food Science and Technol-ogy 45, 2629–2636.

Oliveira, C.M., Ferreira, A.C.S., De Freitas, V. and Silva, A.M.S. (2011)Oxidation mechanisms occurring in wines. Food Research International44, 1115–1126.

Ortega-Heras, M., Pérez-Magariño, S. and González-Sanjosé, M.L. (2012)Comparative study of the use of maceration enzymes and cold pre-fermentative maceration on phenolic and anthocyanic composition andcolour of a Mencía red wine. LWT-Food Science and Technology 48, 1–8.

Payne, C., Bowyer, P.K., Herderich, M. and Bastian, S.E.P. (2009) Interac-tion of astringent grape seed procyanidins with oral epithelial cells. FoodChemistry 115, 551–557.

Peyrot des Gachons, C. and Kennedy, J.A. (2003) Direct method for deter-mining seed and skin proanthocyanidin extraction into red wine. Journalof Agricultural and Food Chemistry 51, 5877–5881.

Pocock, K.F., Sefton, M.A. and Williams, P.J. (1994) Taste thresholds ofphenolic extracts of French and American oakwood: the influence of oakphenols on wine flavor. American Journal Enology and Viticulture 45,429–434.

Poncet-Legrand, C., Doco, T., Williams, P. and Vernhet, A. (2007) Inhibitionof grape seed tannin aggregation by wine mannoproteins: effect ofpolysaccharide molecular weight. American Journal of Enology and Viti-culture 58, 87–91.

Poncet-Legrand, C., Cabane, B., Bautista-Ortín, A., Carrillo, S., Fulcrand, H.,Pérez, J. and Vernhet, A. (2010) Tannin oxidation: intra-versus intermo-lecular reactions. Biomacromolecules 11, 2376–2386.

Puértolas, E., Luengo, E., Álvarez, I. and Raso, J. (2012) Improving masstransfer to soften tissues by pulsed electric fields: fundamentals andapplications. Annual Review of Food Science and Technology 3, 263–282.

Quinn, K.M. and Singleton, V.L. (1985) Isolation and identification ofellagitannins from white oak and an estimation of their roles in wine.American Journal of Enology and Viticulture 36, 148–155.

Renard, C.M.G.C., Baron, A., Guyot, S. and Drilleau, J.F. (2001) Interactionsbetween apple cell walls and native apple polyphenols: quantification andsome consequences. International Journal of Biological Macromolecules29, 115–125.

Rinaldi, A., Gambuti, A. and Moio, L. (2012) Precipitation of salivary pro-teins after the interaction with wine: the effect of ethanol, pH, fructose,and mannoproteins. Journal of Food Science 77, 485–490.

Rodrigues, A., Ricardo-Da-Silva, J.M., Lucas, C. and Laureano, O. (2012)Effect of commercial mannoproteins on wine colour and tannins stability.Food Chemistry 131, 907–914.

Romero-Cascales, I., Ros-García, J.M., López-Roca, J.M. and Gómez-Plaza,E. (2012) The effect of a commercial pectolytic enzyme on grape skin cellwall degradation and colour evolution during the maceration process.Food Chemistry 130, 626–631.

Rowe, J.D., Harbertson, J.F., Osborne, J.P., Freitag, M., Lim, J. andBakalinsky, A.T. (2010) Systematic identification of yeast proteinsextracted into model wine during aging on the yeast lees. Journal ofAgricultural Food Chemistry 58, 2337–2346.

Ruiz-Garcia, Y., Smith, P.A. and Bindon, K.A. (2014) Selective extraction ofpolysaccharide affects the adsorption of proanthocyanidin by grape cellwalls. Carbohydrate Polymers 114, 102–114.

Sánchez-Iglesias, M., González-Sanjosé, M.L., Pérez-Magariño, S.,Ortega-Heras, M. and González-Huerta, C. (2009) Effect of micro-oxygenation and wood type on the phenolic composition and color of anaged red wine. Journal of Agricultural and Food Chemistry 57, 11498–11509.

Sacchi, K.L., Bisson, L.F. and Adams, D.O. (2005) A review of the effect ofwinemaking techniques on phenolic extraction in red wines. AmericanJournal of Enology and Viticulture 56, 197–206.

Sarni-Manchado, P., Deleris, A., Avallone, S., Cheynier, V. and Moutounet,M. (1999) Analysis and characterization of wine condensed tannins pre-cipitated by proteins used as fining agent in enology. American Journal ofEnology and Viticulture 50, 81–86.

Sartini, E., Arfelli, G., Fabiani, A. and Piva, A. (2007) Influence of chips, leesand micro-oxygenation during aging on the phenolic composition of a redSangiovese wine. Food Chemistry 104, 1599–1604.

Schmidtke, L.M., Clarke, A.C. and Scollary, G.R. (2011) Micro-oxygenationof red wine: techniques, applications, and outcomes. Critical Reviews inFood Science and Nutrition 51, 115–131.

Schobinger, U., Stuessi, J. and Waldvogel, R. (1992) Importance of winecolloids for the sensorial quality of wine. Mitteilungen Klosterneubg 42,205–212.

Schroën, C.G.P.H., Roosjen, A., Tang, K., Norde, W. and Boom, R.M. (2010)In situ quantification of membrane foulant accumulation byreflectometry. Journal of Membrane Science 362, 453–459.



Sheridan, M.K. and Elias, R.J. (2015) Exogenous acetaldehyde as a tool formodulating wine color and astringency during fermentation. Food Chem-istry 177, 17–22.

Simonato, B., Mainente, F., Suglia, I., Curioni, A. and Pasini, G. (2009)Evaluation of fining efficiency of corn zeins in red wine: a preliminarystudy. Italian Journal of Food Science 1, 97–105.

Tao, Y., García, J.F. and Sun, D.-W. (2014) Advances in wine aging tech-nologies for enhancing wine quality and accelerating wine aging process.Critical Reviews in Food Science and Nutrition 54, 817–835.

Ugliano, M., Diéval, J.B. and Vidal, S. (2012) Oxygen management duringwine bottle ageing by means of closure selection: current trends andperspectives. Wine and Viticulture Journal 27 (5), 38–43.

Ulbricht, M., Ansorge, W., Danielzik, I., König, M. and Schuster, O. (2009)Fouling in microfiltration of wine: the influence of the membrane polymeron adsorption of polyphenols and polysaccharides. Separation and Purifi-cation Technology 68, 335–342.

Vernhet, A. and Moutounet, M. (2002) Fouling of organic microfiltrationmembranes by wine constituents: importance, relative impact of winepolysaccharides and polyphenols and incidence of membrane properties.Journal of Membrane Science 201, 103–122.

Vernhet, A., Dubascoux, S., Cabane, B., Fulcrand, H., Dubreucq, E. andPoncet-LeGrand, C. (2011) Characterization of oxidized tannins: compari-son of depolymerization methods, assymetric flow field-flow fractionationand small-angle X-ray scattering. Analytical and Bioanalytical Chemistry401, 1559–1569.

Versari, A., du Toit, W. and Parpinello, G.P. (2013) Oenological tannins: areview. Australian Journal of Grape and Wine Research 19, 1–10.

Vidal, S., Francis, L., Noble, A., Kwiatkowski, M., Cheynier, V. and Waters,E. (2004a) Taste and mouth-feel properties of different types of tannin-like

polyphenolic compounds and anthocyanins in wine. Analytica ChimicaActa 513, 57–65.

Vidal, S., Francis, L., Williams, P., Kwiatkowski, M., Gawel, R., Cheynier, W.and Waters, E. (2004b) The mouth-feel properties of polysaccharides andanthocyanins in a wine like medium. Food Chemistry 85, 519–525.

Vidal, S., Francis, L., Guyot, S., Marnet, N., Kwiatkowski, M., Gawel, R.,Cheynier, V. and Waters, E.J. (2003) The mouth-feel properties of grapeand apple proanthocyanidins in a wine-like medium. Journal of theScience of Food and Agriculture 83, 564–573.

Vivas, N. and Glories, Y. (1996) Role of oak wood ellagitannins in theoxidation process of red wines during aging. American Journal of Enologyand Viticulture 47, 103–107.

Waters, E.J., Peng, Z., Pocock, K.F., Jones, G.P., Clarke, P. and Williams, P.J.(1994) Solid-state 13C NMR investigation into insoluble deposits adheringto the inner glass surface of bottled red wine. Journal of Agricultural andFood Chemistry 42, 1761–1766.

Zietsman, A.J., Moore, J.P., Fangel, J.U., Willats, W.G., Trygg, J. and Vivier,M.A. (2015) Following the compositional changes of fresh grape skin cellwalls during the fermentation process in the presence and absence ofmaceration enzymes. Journal of Agricultural and Food Chemistry 63,2798–2810.

Manuscript received: 12 August 2015

Revised manuscript received: 15 September 2015

Accepted: 16 September 2015



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