postharvest heat treatment for mitigation of chilling injury in fruits and vegetables

REVIEW

Postharvest Heat Treatment for Mitigation of Chilling Injuryin Fruits and Vegetables

Morteza Soleimani Aghdam & Samad Bodbodak

Received: 1 March 2013 /Accepted: 29 September 2013 /Published online: 13 October 2013# Springer Science+Business Media New York 2013

Abstract Low-temperature storage is widely used as apostharvest treatment applied for delaying senescence in veg-etables and ornamentals and ripening in fruits, upholding theirpostharvest quality. But the refrigerated storage of tropical andsubtropical crop plant species provokes a set of physiologicalalterations known as chilling injury (CI) that negatively affecttheir quality and frequently renders the product not saleable.The increasing demand for consumption of fresh fruits andvegetables, along with restriction on the use of syntheticchemicals to reduce CI, has encouraged scientific researchon the use of heat treatments as an environment-friendlytechnology for CI mitigation. Membrane damage and reactiveoxygen species production are multifarious adverse effects ofchilling as oxidative stress in sensitive fruits and vegetables.Chilling mitigation in heat-treated fruits and vegetables couldbe attributed to (1) enhancement of membrane integrity bythe increase of unsaturated fatty acids/saturated fatty acids(unSFA/SFA) ratio; (2) enhancement of heat shock proteingene expression and accumulation; (3) enhancement of theantioxidant system activity; (4) enhancement of the argininepathways which lead to the accumulation of signaling mole-cules with pivotal roles in improving chilling tolerance suchas polyamines, nitric oxide, and proline; (5) alteration inphenylalanine ammonia-lyase and polyphenol oxidase en-zyme activities; and (6) enhancement of sugar metabolism.In the present review, we have focused on the impacts of heattreatments on postharvest chilling tolerance and the mecha-nisms activated by this environment-friendly technology infruits and vegetables.

Keywords Fruits . Vegetables . Heat treatment . Chillinginjury .Membrane damage . Oxidative stress

AbbreviationCI Chilling injuryROS Reactive oxygen speciesunSFA Unsaturated fatty acidsSFA Saturated fatty acidsHSPs Heat shock proteinsPAL Phenylalanine ammonia-lyasePPO Polyphenol oxidaseHWD Hot water dippingHWRB Hot water rinsing and brushingMDA MalonyldialdehydeAOX Alternative oxidaseSOD Superoxide dismutaseCAT CatalaseAPX Ascorbate peroxidaseGPX Glutathione peroxidaseGST Glutathione-S-transferaseMDHAR Monodehydroascorbate reductaseDHAR Dehydroascorbate reductaseGR Glutathione reductaseFADs Fatty acid desaturasePLD Phospholipase DLOX LipoxygenaseAEC Adenylate energy chargeAA/DHA Ascorbate/dehydroascorbateGSH/GSSG Glutathione/glutathione disulfideAAO Ascorbic acid oxidasePOD PeroxidasesHSPs Small HSPsPRs Pathogenesis-related proteinsHSTFs Heat shock transcription factorsHSEs Heat shock consensus elementsPAs PolyaminesNO Nitric oxide

M. S. Aghdam (*)Department of Horticultural Science, College of Agricultureand Natural Resource, University of Tehran, Karaj, Irane-mail: [email protected]

S. BodbodakDepartment of Food Science and Technology, Faculty of Agriculture,University of Tabriz, Tabriz, Iran

Food Bioprocess Technol (2014) 7:37–53DOI 10.1007/s11947-013-1207-4

ODC Ornithine decarboxylaseADC Arginine decarboxylaseNOS Nitric oxide synthaseGSA Glutamate-semialdehydeP5CS Pyrroline-5-carboxylate synthetaseP5C Pyrroline-5-carboxylateP5CR P5C reductaseOAT Ornithine aminotransferasePDH Proline dehydrogenaseP5CDH P5C dehydrogenaseIB Internal browningTP Total phenolsAI Acid invertaseNI Neutral invertaseSS Sucrose synthaseSPS Sucrose phosphate synthaseHK HexokinasePFK Phosphor fructokinase

Introduction

Low-temperature storage has been the main strategy appliedin postharvest to prolong the shelf life of fruits and vegetablesand maintain their quality. Storage at low temperature reducesthe respiratory rate and minimizes fungal disease. However,tropical and subtropical fruits and vegetables are susceptibleto low-temperature treatment, and they suffer from chillinginjury (CI). The symptoms of CI in fruits and vegetables couldbe distinguished into two categories: (1) developmental ormetabolic symptoms with qualitative nature such as abnormalripening and poor flavor and aroma and (2) physiologicalsymptoms such as pitting, discoloration, water soaking,internal breakdown, and susceptibility to mechanicalinjury and fungal attack (Sevillano et al. 2009). In caseswhere chilling impact is very severe, it causes significantdeterioration of the produce and therefore has a great negativeeffect on produce final market value and leads to great eco-nomical losses.

According to the reluctance of consumers to chemical res-idues in fruits and vegetables, applications of safe andenvironment-friendly technologies to prevent or mitigate CIhave great importance; thus, considerable researches havebeen done in this postharvest research field. Therefore, theuse of heat treatments (38–60 °C) is actually considered anenvironment-friendly technology of CI mitigation (Fallik2004). Heat is applied as a prestorage treatment prior to short-ening or prolonging low-temperature storage using hot water,hot air, or vapor heat. The two main commercial hot watertreatments are hot water dipping (HWD) and hot water rinsing

and brushing (HWRB; Fallik 2004). HWD is used at a tem-perature range of 43–53 °C for periods of minutes up to 2 h,while HWRB is applied commercially at temperatures ranging48–63 °C for 10–25 s. The choice of suitable temperatures andtreatment time depends on the cultivar, fruit maturity, fruit size,and condition during the growing season (Lurie 2008). The useof short heat treatments such as HWD and HWRB has beenrecommended by scientific researches because they have nounfavorable impacts on the quality attributes of the fruits andvegetables in comparison with longer treatments. Also, shortheat treatments protect fruits and vegetables against incidenceof postharvest rots, have convenient application and are lowcost, and, ultimately, improve the general appearance of fruitsand vegetables (Fallik 2004).

Malfunction of Membrane: The Primary Effect Causedby Chilling Injury

Cell membrane is the primary structure affected by CI (Wang1982; Nordby and Mc Donald 1991; Sharom et al. 1994; Ruiet al. 2010). The transition of cell membranes from a flexibleliquid crystalline phase to a solid gel structure that occurs atchilling temperature increments the risk of controlled cellmembrane semi-permeability loss (Lyons 1973). Transitionof the cell membranes’ physical phase is considered as the firstimpact of CI at the molecular level (Sevillano et al. 2009). Atchilling temperature, membrane fatty acid peroxidation, in-crease of the saturation degree of fatty acids, degradation ofphospholipids and galactolipids, and rise of the sterol-to-phospholipid ratio lead to the reduction of membrane fluidityand function (Sevillano et al. 2009). If fruits and vegetablesare exposed to damaging temperatures for too long a time,cell membrane rupture takes place, causing leakage of intra-cellular water, ions, and metabolites, which can be monitoredby determining electrolyte leakage (Sharom et al. 1994).Electrolyte leakage is an effective parameter to assess mem-brane permeability and therefore is used as an indicator ofmembrane integrity (Marangoni et al. 1996). In addition, lipidperoxidation, responsible for loss of cell membrane integrity,could be evaluated by the content of malonyldialdehyde(MDA; Wise and Naylor 1987). MDA is the end product ofthe peroxidation of membrane fatty acids. The quantity ofMDA is used as a marker of oxidative stress and a rise ofMDA indicates damage of cell membrane integrity (Hodgeset al. 1999). The main result of both events is the loss ofthe biomembrane functionality (Sevillano et al. 2009). Takentogether, electrolyte leakage and MDA content, as physiolog-ical markers of loss of membrane semi-permeability and mem-brane lipid peroxidation, were widely used by researchers to

38 Food Bioprocess Technol (2014) 7:37–53

indirectly assess cell membrane integrity (Wise and Naylor1987; Sharom et al. 1994).

Oxidative Stress: The Secondary Effect Causedby Chilling Injury

In addition to the direct effect of chilling temperatures on themembrane structure, the loss of membrane integrity is itselfboosted by oxidative stress since cold stress increases thelevels of ROS that stimulate lipid peroxidation in cell mem-branes (Sevillano et al. 2009; Fig. 1). Accumulation of harm-ful ROS such as superoxide (O2

⋅−), hydrogen peroxide(H2O2), hydroxyl radical (OH

⋅), and singlet oxygen lead to

the oxidation of the cell’s vital molecules such as loss ofmembrane integration via lipid peroxidation, protein oxida-tion, enzymatic activity inhibition, and, finally, damage toDNA and RNA and dictates, ultimately, oxidative stress. Inplant cells, ROS accumulation may be due to the inescapableleakage of electrons onto O2 from the electron transport chainin chloroplasts and mitochondria and/or by the activation ofNADPH oxidases located in cell membranes (Bhattacharjee2012). Møller (2001) suggested that plant defense againstoxidative stress was accomplished in two ways. The firstwas the activation of the expression of genes encoding pro-teins involved in activating ROS avoidance such as alternativeoxidase (AOX). The AOX pathway was a branch of therespiratory electron transport chain in the mitochondria thatemerges from the cytochrome. When over-reduction occurs inthis electron transport chain, AOX interferes via inhibiting theexcessive reduction of ubiquinol and thus assists in avoidingROS accumulation (Møller 2001; Fig. 1). This antioxidantactivity of AOX was reported in pepper and tobacco (Purvis1997; Maxwell et al. 1999). An increase in the level of AOXgene expression in pepper fruit treated with methyl salicylateand methyl jasmonate enhanced CI tolerance (Fung et al.2004). Enhancement of AOX gene expression leads to anincrease of resistance against CI via maintenance of thebalance between ROS production and general antioxidantsystem activity (Purvis 1997). The second way of defenseagainst oxidative stress is by inducing the activity or the geneexpression of ROS scavengers such as antioxidant enzymesincluding superoxide dismutase (SOD), catalase (CAT), ascor-bate peroxidase (APX), glutathione peroxidase (GPX),glutathione-S-transferase (GST), monodehydroascorbate re-ductase (MDHAR), dehydroascorbate reductase (DHAR),and glutathione reductase (GR; Møller 2001). In tomato fruit,a biphasic chilling sensitivity pattern during ripening wasfound (Autio and Bramlage 1987). The response to chillingstress by changes in the activity of scavenging enzymes de-pends greatly on the ripening stage. The increased activity ofboth SOD and APX in breaker tomato fruits point to theoccurrence of oxidative stress as an immediate stress responseto chilling and the ability to alleviate it; in red ripe fruits, APXactivity declined (Gómez et al. 2009). Sánchez-Bel et al.(2012) reported that storage of pepper at 1 °C led to CI, whichwas accompanied with (1) the accumulation of MDA due toperoxidation of membrane unsaturated fatty acids (unSFA) asa result of ROS accumulation; (2) degradation of plastids anddisappearance of peroxisomes; and (3) reduction of CATantioxidant enzyme activity. Accumulation of ROS in pepperfruits stored at 1 °C led to the peroxidation of unSFA ofperoxisomes monolayer membrane and the disappearance ofperoxisomes. Since CAT is a peroxisomic enzyme, the reduc-tion of its activity in peppers stored at 1 °C could be attributed

Fig. 1 High FAD gene expression and activity, high levels of cellmetabolic energy (ATP and AEC), and lower levels of activity of PLDand LOX pro-oxidant enzymes, accompanied by boosted activities ofenzymes from the antioxidant system (AOX or SOD, CAT, GPX, GST,APX, DHAR, and MDHAR), result in enhancing the unSFA/SFA ratioand diminishing ROS accumulation, which leads to improved membranefluidity and integrity; all of these biological processes potentially impacton CI tolerance (Aghdam et al. 2013)

Food Bioprocess Technol (2014) 7:37–53 39

to the disappearance of peroxisomes. Higher activity of theenzymatic antioxidant system led to the reduction of ROS,therefore improving membrane integrity and ultimately en-hancing resistance toward CI (Mittler 2002; Fig. 1).

Mechanism Employed by Heat Treatment for Mitigationof Chilling Injury

Postharvest heat treatments applied to fruits and vegetablesprior to low-temperature storage in order to prevent or miti-gate CI have been commercially applied in grape berry (Zhanget al. 2005), pitaya (Narvaez-Cuenca et al. 2011), cherimoya(Sevillano et al. 2010), tomato (Polenta et al. 2007; Sabehatet al. 1996 1998a, b), grapefruit (McDonald et al. 1993;Milleret al. 1990; Wild 1993; Polenta et al. 2007; Rozenzvieg et al.2004; Porat et al. 2002a, b, 2004; Pavoncello et al. 2001),orange (Bassal and El-Hamahmy 2011), banana (He et al.2012; Chen et al. 2008), cucumber (Mao et al. 2007a, b),loquat (Rui et al. 2010), mandarin (Ghasemnezhad et al.2008), pepper (González-Aguilar et al. 2000), and pomegran-ate (Artés et al. 2000; Mirdehghan et al. 2007). Chillingmitigation in heat-treated fruits and vegetables could be attrib-uted to (1) enhancement of membrane integrity by enhancingthe unSFA/saturated fatty acid (SFA) ratio; (2) enhancementof heat shock protein (HSP) gene expression and accumula-tion; (3) enhancement of antioxidant system activity; (4) en-hancement of the arginine pathways which lead to the accu-mulation of signaling molecules with pivotal roles in improv-ing chilling tolerance such as polyamines, nitric oxide, andproline; (5) alteration in phenylalanine ammonia-lyase (PAL)and polyphenol oxidase (PPO) enzyme activities; and (6)enhancement of sugar metabolism. Key results reported byauthors regarding the impact of heat treatments on the chillingtolerance of fruits and vegetables have been summarized inTable 1.

Enhancing Membrane Integrity

Membrane fluidity has the ability to regulate membrane func-tion through its effects on membrane integral protein arrange-ment, permeability, and transmembrane transport activity (Losand Murata 2004). Fatty acid desaturases (FADs) are a groupof enzymes responsible for the increase of membraneunsaturation degree and its fluidity (Hernández et al. 2011).FAD enzyme activities are responsible for increasing theunsaturation degree of fatty acids from the lipid bilayer thatmakes up the cell membrane. In general terms, it has beenaccepted by the scientific community that chilling-sensitivetropical and subtropical fruits and vegetables have lowerunSFA/SFA ratios (Sakamoto and Murata 2002). Higher de-grees of unSFA in lipids generally lead to a lower incidence ofCI (Marangoni et al. 1996). The accumulation of unSFAs like

linoleic and linolenic acids commonly protects the physicalintegrity of plant cell membranes and was related to an in-creased resistance to CI (Wang 1982). The mechanisms oflow-temperature tolerance are partially based on an increase ofunSFA levels that results in the rise of membrane fluidity viaincreasing the FAD activity (Los andMurata 1998; Hernándezet al. 2011; Yu et al. 2009). Increase of the membraneunsaturation degree or its double bond index as the criterionof membrane unsaturation due to the increase of unSFAs suchas linolenic acid (18:3) led to the enhancement of membranefluidity, and cellular function can be enhanced by increasingmembrane integrity. Increase of membrane fluidity decreasesthe membrane’s tendency to change phase from flexible liquidcrystalline to solid gels and results in enhanced CI tolerance(Los and Murata 2004). Cao et al. (2011) observed thatresistance toward CI of chilling-tolerant Qingzhong cv. ofloquat fruit in comparison with chilling-sensitive Fuyang cv.was attributed to a higher content of linolenic and linoleicacids, characteristic unSFA, and lower levels of palmitic andstearic acid, characteristic SFA, with both events yielding ahigher unSFA/SFA ratio. Pinhero et al. (1998) suggested thatincreases of phospholipase D (PLD) and lipoxygenase (LOX)enzyme activities are responsible for the degradation ofunSFA and the reduction of cell membrane integrity, thereforeaugmenting the impact of CI. Lipid peroxidation could becarried out by enzymatic oxidation of unSFA by LOX or bynon-enzymatic oxidation by ROS. In pepper, it was suggestedthat oxidation of membrane unSFA by LOX led to loss ofmembrane integrity and hastened water loss (Maalekuu et al.2006). Peroxidation of membrane unSFA due to the produc-tion and accumulation of ROS is associated with MDA pro-duction that leads to the decrease of membrane integrity. Inaddition to peroxidation of membrane unSFA, regarding therole of ATP and adenylate energy charge (AEC) in the bio-synthesis of unSFA and desaturation of fatty acids (Brown andBeevers 1987; Crawford and Braendle 1996), reduction ofenergy levels (decline of ATP and ADP and increase of AMP,and, finally, decline of AEC) can also reduce membraneintegrity. Membrane integrity has a crucial role in pericarpbrowning of fruits such as litchi (Marangoni et al. 1996). Inpomegranate fruit, hot water treatment (45 °C for 4 min)mitigated CI via enhancement of the unSFA/SFA ratio. Thisalleviation of CI in hot water-treated pomegranate fruit wasassociated with reduction of skin browning and electrolyteleakage and maintenance of fruit firmness (Mirdehghan et al.2007). Rui et al. (2010) reported that hot air treatment (38 °Cfor 5 h) mitigated CI in loquat fruit via reduction of electrolyteleakage and MDA content and decreases of PLD and LOXenzyme activities which are responsible for unSFA peroxida-tion. The mitigation of CI in this fruit was associated with areduction of palmitic, stearic, and oleic acid contents and anincrease of linoleic and linolenic acid contents, ultimatelyenhancing the unSFA/SFA ratio. Rui et al. (2010) suggested


Table 1 Postharvest heat treatments and their mechanism for improving chilling tolerance in fruits and vegetables

Author(s) Treatment Commodity Biochemical effects

Enhancing membrane integrity

Mirdehghan et al. (2007) Hot water: 45 °C for 4 min Pomegranate Decreasing skin browning

Decreasing electrolyte leakage

Storage: 2 °C for 90 days Maintaining firmness

Enhancing unSFA/SFA

Rui et al. (2010) Hot air: 38 °C for 5 h Loquat Decreasing electrolyte leakage

Decreasing MDA content

Storage: 1 °C for 35 days Decreasing PLD and LOX activity

Enhancing unSFA/SFA

Mao et al. (2007a,b) Hot air: 37 °C for 24 h Cucumber Decreasing electrolyte leakage


Storage: 2 °C for 9 days Decreasing PLD and LOX activity

Enhancing membrane binding Ca2+

Diminishing cytosolic Ca2+

Shao and Tu (2013) Hot air: 38 °C for 36 h Loquat Maintaining extractable juice

Decreasing internal browning and decay

Storage: 4 °C for 28 days Decreasing membrane permeability

Enhancing unSFA/SFA

Shao et al. (2013) Hot air: 45 °C for 3 h Loquat Maintaining extractable juice

Decreasing internal browning

Storage: 5 °C for 35 days Decreasing MDA content

Decreasing membrane permeability

Enhancing unSFA/SFA

Enhancing antioxidant system activity

Ghasemnezhad et al. (2008) Hot water: 50 °C for 2 min Mandarin Decreasing ethylene production

Decreasing respiration rate

Decreasing ethanol and acetaldehyde

Storage: 2 °C for 56 days Increasing CAT activity

Decreasing POX activity

Increasing V-ATPase and V-PPase activity

Wang et al. (2012) Hot water: 52 °C for 3 min Banana Increasing APX activityStorage: 7 °C for 10 days

Bassal and El-Hamahmy (2011) Hot water: 41 °C for 20 min Orange Increasing POX and CAT activity

Storage: 1 °C for 20 days Increasing TP content

Increasing AA level

Decreasing AAO activity

Narvaez-Cuenca et al. (2011) Hot air: 25 °C for 24 h Pitaya Decreasing respiration rate

Storage: 1 °C for 20 days Decreasing H2O2 and O2⋅− contents


Cao et al. (2010) Hot air: 38 °C for 12 h Peach Increasing CAT, APX, and GR activity

Storage: 0 °C for 35 days Increasing SOD/LOX activity

Decreasing H2O2 and O2⋅− contents

Safizadeh et al. (2007) Hot water: 53 °C for 3 min Lemon Increasing CAT and SOD activity

Storage: 1.5 °C for 56 days Decreasing POD activity





Increasing SOD, APX, GR and CAT activity


Table 1 (continued)


Decreasing H2O2 content

Shao et al. (2013) Hot air: 45 °C for 3 h Loquat Maintaining extractable juice

Decreasing internal browning



Increasing APX and GR activity

Enhancing AA and GSH contents

Diminishing H2O2 accumulation

Enhancing HSP accumulation

Sevillano et al. (2010) Hot air: 55 °C for 5 h Cherimoya Enhancing sHSP gene expressionStorage: 20 °C for 5 days

He et al. (2012) Hot air: 38 °C for 3 days Banana Decreasing electrolyte leakage


Storage: 8 °C for 12 days Decreasing lightness and chroma

Enhancing sHSP gene expression

Rozenzvieg et al. (2004) Hot water: 62 °C for 20 s Grapefruit Enhancing HSP gene expressionStorage: 2 °C for 56 days

Polenta et al. (2007) Hot air: 38 °C for 24 and 48 h Grapefruit Enhancing HSP accumulationTomato

Pavoncello et al. (2001) Hot air: 62 °C for 20 s Grapefruit Reducing decay

Enhancing HSP gene expression

Enhancing PR gene expression

Sabehat et al. (1998a, b) Hot air: 38 °C for 3 days Tomato Enhancing tom66 and tom111gene expressionStorage: 2 °C for 21 days

Lurie et al. (1996) Hot air: 38 °C for 3 days Tomato Enhancing HSP17 accumulationStorage: 2 °C for 21 days

Zhang et al. (2005) Hot air: 38 °C for 10 h Grape berry Decreasing electrolyte leakage


Storage: −2 °C for 3 days Increasing SOD and CAT activity

Enhancing HSP70 gene expression

Enhancing arginine pathways

Mirdehghan et al. (2007) Hot water: 45 °C for 4 min Pomegranate Decreasing skin browning

Storage: 2 °C for 90 days Decreasing electrolyte leakage

Maintaining firmness

Enhancing endogenous PA contents

Zhang et al. (2013b) Hot air: 38 °C for 16 h Tomato Decreasing electrolyte leakage


Enhancing arginase gene expression

Storage: 2 °C for 28 days Increasing SOD, CAT, and APX activity

Decreasing POX activity

Enhancing endogenous arginine, proline, andputrescine contents

Zhang et al. (2013c) Hot air: 38 °C for 12 h Tomato Enhancing arginase gene expression

Storage: 2 °C for 28 days Enhancing ADC, ODC, and OAT gene expression

Enhancing endogenous proline and putrescine contents

Gonzales-Aguilar et al. (2000) Hot water: 53 °C for 4 min Pepper Enhancing endogenous PA contentsStorage: 8 °C for 28 days

Alteration in PAL and PPO enzyme activities

Chen et al. (2008) Hot air: 38 °C for 2 days Banana Decreasing electrolyte leakage



that heat treatment maintained membrane fluidity and integri-ty in loquat fruit and increased resistance toward CI viareduction of PLD and LOX enzyme activities. Mao et al.(2007a) observed that hot air treatment (37 °C for 24 h)mitigated CI in cucumber fruit, and this process was associat-ed with reduction of electrolyte leakage and MDA content.Hot air treatment decreased PLD and LOX enzyme activitiesand reduced PLD gene expression in cucumber fruit (Maoet al. 2007a). The authors suggested that hot air treatmentassisted in maintaining membrane integrity and enhanced CItolerance by means of diminishing PLD and LOX enzymeactivities. Calcium has a fundamental role in cell membraneintegrity and cell wall strength. The binding of calcium to cellmembrane components, particularly phospholipids, is essen-tial for the preservation of membrane integrity and the controlof its functionality (Aghdam et al. 2012b). In fact, PLDactivity is regulated by cytosolic Ca2+ concentration, and riseof cytosolic Ca2+ concentration in response to environmentalstress such as chilling temperature and/or a hormonal messagesuch as ethylene leads to PLD activation (Aghdam et al.2012b). Mao et al. (2007b) observed that hot air treatment(37 °C for 24 h) mitigated CI in cucumber fruits, and this wasachieved by facilitating Ca2+ binding to cell membranes.Facilitation of Ca2+ binding to membranes by heat treatment

might have been attributed to the change in membrane com-position which occurred during warming. The results of Maoet al. (2007b) indicated that heat treatment reduced PLD andLOX activities by increasing Ca2+ bound to the membrane.Increase of Ca2+ binding to the membrane was accompaniedwith a reduction of cytosolic Ca2+ concentration, which in turndecreased PLD and LOX enzyme activities and PLD geneexpression. In that way, membrane integrity was upheld andthe CI mitigated (Mao et al. 2007b). Increase of cytosolic Ca2+

concentration could activate membrane lipid degradation andstimulate LOX activity, a fact that conducts the reduction ofmetabolic access to the free fatty acids used for the biosyn-thesis of cell membrane phospholipids (Pinhero et al. 1998).Mao et al. (2007b) suggested that hot air treatment led to areduction of LOX activity through the induction of Ca2+

binding to membrane lipids and reduction of cytosolic Ca2+

concentration, thus reducing the availability of free fatty acidsfor the biosynthesis of membrane phospholipids. This phe-nomenon could explain the observed resistance against CI incucumber fruit (Mao et al. 2007b). Shao and Tu (2013)reported that mitigation of CI in hot air-treated loquat fruit(38 °C for 36 h) was accompanied with higher extractablejuice and lower firmness and internal browning (IB). Shao andTu (2013) showed that heat treatment significantly diminished

Table 1 (continued)


Storage: 8 °C for 12 days Increasing PAL activity

Stimulating TP accumulation



Storage: 4 °C for 28 days Diminishing PAL, POD, and PPO activity

Decreasing H2O2 accumulation

Reducing TP accumulation

Diminishing lignin biosynthesis

Enhancing sugar metabolism

Shao et al. (2013) Hot air: 45 °C for 3 h Loquat Decreasing internal browning

Maintaining extractable juice

Storage: 5 °C for 35 days Enhancing reducing sugars

Decreasing sucrose content

Increasing invertase, SS, and SPS activities

Lara et al. (2009) Hot air: 39 °C for 3 days Peach Enhancing increasing and SS activity

Enhancing reducing sugars

Storage: 20 °C for 7 days Decreasing sucrose content

Enhancing HSP, cysteine proteases, and dehydringene expression

Repression PPO gene expression

Mirdehghan et al. (2006) Hot water: 45 °C for 4 min Pomegranate Enhancing reducing sugars

Storage: 2 °C for 90 days Enhancing organic acids (malic, citric, and oxalic acids)

Enhancing total antioxidant activity


the H2O2 level via enhancing SOD, APX, GR, and CATantioxidant enzyme activities; maintained lower membranepermeability related to a higher unSFA/SFA ratio by increas-ing the oleic and linoleic acid levels; and diminished thelauric, myristic, palmitic, and stearic acid levels. Shao andTu (2013) suggested that heat treatment enhanced chillingtolerance in loquat fruit via activation of the ROS scavengingsystem and reduced the peroxidation of membrane unsaturat-ed fatty acids. Shao et al. (2013) reported that hot air treatment(45 °C for 3 h) mitigated CI in loquat fruit and resulted inlower firmness and IB and higher levels of extractable juice.They reported that loquat fruit treated with hot air showedlower MDA content and membrane permeability. Also, loquatfruit treated with hot air showed significantly lower lauric(12:0) and stearic acids (18:0) and higher myristic (14:0) andlinoleic acids (18:2). Loquat fruit treated with hot airmaintained a higher unSFA/SFA ratio. A higher level ofmembrane lipid unsaturation supports the hypothesis statingthat heat treatment could reduce lipid peroxidation and isbeneficial for enhancing the resistance of loquat fruit to CI,in accordance with Cao et al. (2011) and Rui et al. (2010).

Enhancing Antioxidant System Activity

Cao et al. (2011) observed that resistance toward CI ofchilling-tolerant Qingzhong cv. of loquat fruit in comparisonwith chilling-sensitive Fuyang cv. was associated with higherSOD and CATactivities alongwith lower LOX activity, whichled to the mitigation of oxidative stress by decreasing H2O2

and O2⋅− contents. The authors also observed that APX, GR,

and MDHAR activities in Qingzhong cv. were higher than inFuyang cv., which generated an increase of ascorbic acid(AA) and glutathione (GSH) levels, boosting ascorbate/dehydroascorbate (AA/DHA) and glutathione/glutathione di-sulfide (GSH/GSSG) ratios. Narvaez-Cuenca et al. (2011)reported that treatment of yellow pitaya fruit with hot air(25 °C for 24 h) mitigated CI by reducing the respiration rate,H2O2 and O2

⋅− contents, and the MDA level. The authorssuggested that the mitigation of CI in yellow pitaya fruitsubjected to postharvest heat treatment was caused bydiminishing ROS levels and upholding membrane integrity.Cao et al. (2010) reported that hot air (38 °C for 12 h)treatment and SA application (1 mM for 5 min), individuallyor in combination, mitigated CI in peach fruit. In peach fruittreated with a combination of both treatments, the antioxidantenzyme activities (SOD, CAT, APX, and GR) increased andLOX activity decreased. LOX is responsible for superoxideradical production that, after intervention of the SOD enzyme,could be converted into H2O2. H2O2 can be scavenged due toCAT, APX, and GR enzyme activities (Mittler 2002). Peachestreated with hot air in combination with SA have an increasedSOD enzyme activity and decreased LOX activity, meaningthat a rise of the SOD/LOX ratio occurred, which led to a net

reduction of the superoxide radical level, and an increase ofCAT, APX, and GR enzyme activities led to the reduction ofH2O2 levels (Cao et al. 2010).

Ghasemnezhad et al. (2008) reported that hot water treat-ment (50 °C for 2 min) alleviated CI inmandarin fruit stored at2 °C for 8 weeks. The observation was associated with areduction of ethylene production, respiration rate, and anaer-obic metabolite content such as ethanol and acetaldehyde. Theheat treatment also had an influence on the antioxidant enzy-matic system since it increased CATactivity and reduced POXactivity. The authors observed that if the treatment had beenperformed at 55 °C, it would cause damage to the fruit’s skin,probably due to an increase of POX activity which might beresponsible for the reduction of tonoplast integrity. V-ATPaseand V-PPase enzymes could be used as potential indicatorsof vacuolar membrane tonoplast integrity. V-ATPase andV-PPase gene expression in mandarin fruit treated with hotwater at 55 °C increased during posterior cold storage (2 °Cfor 8 weeks), and it might be useful for the sake of maintainingtonoplast integrity (Ghasemnezhad et al. 2008). Wang et al.(2012) reported that banana fruit treated with hot water (52 °Cfor 3 min), which was exposed to short-term storage (7 °C for10 days) afterwards with delay (<6 h), displayed high CItolerance and rise of APX gene expression and activity duringcold storage. Bassal and El-Hamahmy (2011) reported that hotwater treatment (41 °C for 20 min) mitigated CI in Valenciaand Navel oranges by way of enhancing the POX and CATactivities and total phenol (TP) content. Hot water treatmentincreased the AA levels in orange fruits due to the reduc-tion of ascorbic acid oxidase (AAO) activity (Bassal and El-Hamahmy 2011). Safizadeh et al. (2007) reported that thetreatment of Lisbon lemon fruit with CaCl2 and hot water(53 °C for 3 min) mitigated CI. They suggested that CI inlemon fruit under low-temperature storage was the result of adecrease in CAT and SOD activity and an increase of perox-idase (POD) activity. CaCl2 and hot water treatments mitigat-ed CI by increasing CAT and SOD activities and diminishingPOD activity, which led to maintenance of membrane integ-rity reflected by a reduced MDA content. Shao and Tu (2013)reported that hot air treatment (38 °C for 36 h) mitigated CI inloquat fruit, associated with diminishing lignin content, whichmight be attributed to the decrease of H2O2 accumulation.Shao and Tu (2013) suggested that heat treatment coulddiminish H2O2 accumulation by enhancement of the antioxi-dant enzyme activities (SOD, APX, GR, and CAT), whichreduced membrane unSFA peroxidation and maintained ahigher unSFA/SFA ratio and higher membrane integrity.H2O2 not only contributed to lignin biosynthesis but alsocontributed to membrane unSFA peroxidation due to H2O2

accumulation under chilling stress with oxidative facet(Hodges et al. 2004). Heat treatment in loquat fruit ledto lower membrane permeability and lignin content viadiminishing H2O2 accumulation (Shao and Tu 2013).


Enhancing HSP Gene Expression and Accumulation

Heat shock proteins (HSPs) are a stress-responsive family ofproteins with molecular weights ranging between 15 and115 kDa. Five families of HSPs have been identified:HSP70s, chaperonins (HSP60s), HSP90s, HSP100s, andHSPs with low molecular weight, so-called small HSPs(sHSPs). HSPs are widely distributed within the cytoplasmand nucleus, but are also found in cell compartments such asthe mitochondria, chloroplast, and endoplasmic reticulum(Timperio et al. 2008; Wang et al. 2004). Low-temperaturestress causes protein denaturation during the postharvestlife of fruits and vegetables. HSPs show their beneficialaction as molecular chaperones maintaining protein sta-bility (Thomashow 1999). It is obvious that HSPs exerttheir protective role against stress by means of molecularchaperone activity, which consists of (1) recognizing andbinding to unfolded proteins in order to correctly completetheir folding, (2) preventing protein aggregation, and (3) fa-cilitating the renaturation of aggregated proteins. The chaper-one activity of HSPs has been observed both in vivo andin vitro (Ellis and van der Vies 1991; Craig et al. 1994; Lee1995; Boston et al. 1996). sHSPs, with low molecular weightranging between 15 and 42 kDa, have chaperone activitywhich, in contrast to HSPs of higher molecular weight, isindependent of ATP (Gusev et al. 2002). sHSPs contributeto abiotic stress tolerance thanks to their role as stabilizingagents of cell membranes (Nakamoto and Vigh 2007; Horváthet al. 2008). Therefore, membrane attributes such as fluidityand semi-permeability are at least partially under the controlof sHSPs; thus, sHSPs may assist in maintaining the fluidityand integrity of cell membranes in fruits and vegetablessubjected to postharvest chilling stress (Török et al. 2001;Tsvetkova et al. 2002; Horváth et al. 2008). Sevillano et al.(2010) reported that hot air treatment (55 °C for 5 h) mitigatedCI in cherimoya fruit and that this effect occurred associatedwith the induction of sHSP gene expression, and possibly bychaperoning the activity of sHSPs. He et al. (2012) alsoobserved that hot air treatment (38 °C for 3 days) alleviatedCI in banana fruit. They reported that sHSP1 expression inpeel and pulp and sHSP3 expression in peel increased duringheat treatment; the expression of both genes in pulp andsHSP2 in peel was augmented during subsequent storage atlow temperature (8 °C). The authors suggested that heattreatment increased resistance to CI by stimulating sHSP geneexpression in banana fruit during low-temperature storage.Alleviation of CI in banana fruit treated with hot air wasassociated with a reduction of electrolyte leakage and MDAcontent and also decreases in lightness and chroma.Rozenzvieg et al. (2004) observed that hot water treatment(62 °C for 20 s) increased HSP gene expression in grapefruitthat were afterwards stored at low temperature (2 °C), and thisevent was associated with the observed tolerance against CI.

The application of hot air treatment (38 °C) with optimumintensity (24 and 48 h) led to a significant mitigation of CI ingrapefruit and tomato. Thus, the accumulation of HSPs was apowerful tool to evaluate treatment intensity and efficacy andcould predict the success of treatment in the mitigation of CI(Polenta et al. 2007). Hot air treatment (62 °C for 20 s)reduced fruit spoilage and increased HSP and pathogenesis-related protein (PR) gene expression in grapefruit (Pavoncelloet al. 2001). Increase of HSPs may reduce spoilage throughcontribution in the recognition of decay-affected areas andtransport of PRs, such as chitinase and β-1,3-glucanase, toheal this detrimental effect on fruits (Pavoncello et al. 2001).Sabehat et al. (1996) observed that treatment of tomato fruitwith hot air (38 °C for 48 h) mitigated CI and that HSPaccumulation occurred, which persisted during posteriorlow-temperature storage (2 °C). In particular, it seems thattreatment of tomato fruit with hot air (38 °C for 3 days) led tothe stimulation of CI resistance through the rise of HSP17accumulation and the persistence of its level during the lattercold storage (2 °C; Lurie et al. 1996). The induction ofexpression of tomato genes encoding for sHSPs, such astom66 and tom111 , when the fruit was treated with hot air(38 °C for 3 days) and the persistence of their levels duringsubsequent cold storage (2 °C) were associated with toleranceagainst CI (Sabehat et al. 1998a, b).

At the molecular level, the expression of heat shock genesencodingHSPs is regulated by heat shock transcription factors(HSTFs) which have the ability to sense heat and/or coldstress and then activate HSP gene expression by binding toheat shock consensus elements (HSEs) located in the TATA-box-proximal 5′-flanking regions within the promoter of heatshock genes. The eukaryotic HSE consensus sequence hasbeen defined as alternating units of 5′-nGAAn-3′, and efficientHSTF binding requires at least three units of this consensus,which resulted in 5′-nGAAnnTTCnnGAAn-3′ (Schoffl et al.1998; Larkindale et al. 2005). HSTFs are present in thecytoplasm of unstressed cells as a latent monomer that lacksboth DNA binding and transcriptional activity. During expo-sure to stress, HSTFs are converted from monomeric to tri-meric forms, which have high-affinity HSE binding capacityand transcriptional activation (Sorger and Nelson 1989; Al-Whaibi 2011).

Fruits and vegetables are protected against oxidative stressby an antioxidant system including antioxidant enzymes andantioxidant molecules. HSTFs, like molecular sensors, areable to sense ROS such as H2O2 and consequently regulatethe expression of oxidative stress response genes. The geneencoding pea APX1 , an enzyme responsible for scavengingH2O2, contains a functional HSTF binding motif in its pro-moter region (Mittler and Zilinskas 1992). HSTF-dependentAPX1 gene expression in Arabidopsis suggests that HSTFsare involved not only in regulating HSP gene expression butalso in the expression of antioxidant system functioning genes


needed in order to enhance resistance to oxidative stress(Panchuk et al. 2002). In addition to this action of HSTFsregulating the expression of genes encoding for antioxidantenzymes, HSPs are able to induce the activity of antioxidantenzymes. Zhang et al. (2005) observed that hot air treatment(38 °C for 10 h) mitigated CI in grape berry. The rise of CItolerance was accompanied by a reduction of electrolyte leak-age and MDA content and an increase of SOD and CATactivities. Hot air treatment also induced HSP70 expressionin grape berry before the rise in the antioxidant enzymeactivities was observed. The authors suggested that inductionof HSP70 expression and the corresponding protein accumu-lation was associated with a rise of the antioxidant enzymeactivities in grape berry, and that synergistic action betweenHSP70 and the enzymatic antioxidant system led to the in-crease in membrane integrity and resistance to CI. Zhang et al.(2011a) suggested that heat treatment increased the ability ofactivating defense mechanisms during fruit ripening and de-velopment in peach via enhancing HSP gene expression. Inaddition, HSPs are able to improve cellular defense againstoxidative stress by inducing the accumulation of antioxidantmolecules such as GSH. Wang et al. (2006) reported thatpostharvest salicylic acid treatment significantly mitigatedCI in peach fruit, probably by the induction of HSP101 andHSP73 protein expressions, which in turn seems to influencethe rise of AA/DHA and GSH/GSSG ratios. Indeed, theauthors suggested that stimulation of HSP101 and HSP73biosynthesis is correlated with GSH levels in salicylic acid-treated peaches, and a surge in the CI tolerance of fruits maybe due to the synergic action of both HSPs and the antioxidantsystem. By positively influencing the GSH/GSSG balance,HSP action allows maintenance of the GSH supply to DHAR,which is responsible for the conversion of DHA to AA(Sala 1998). Thus, in fruits and vegetables, HSPs may play apivotal role in regulating the antioxidant system such as en-hancing the GSH level and increasing antioxidant enzyme geneexpression and/or activity, which led to the rise of resistanceagainst postharvest CI in oxidative stress facet. In addition tothe aforementioned actions of HSPs, there are evidences thatHSPs also play a synergic action with antioxidant systems inorder to protect the plant from the secondary oxidative effectcaused by stress. It is suggested that environmental stresseslead to a reduction of cell membrane integrity due to increasingROS levels which occur in this situation, which provokedmembrane lipid peroxidation (Fig. 1). Zou et al. (2012) ob-served that the MDA levels were significantly lower in trans-genic rice plants overexpressing OsHSP23 .7 and OsHSP17 .0subjected to salinity and drought stresses than in non-transformed plants. Regarding the last aspect, it has beensuggested that sHSPs may even be involved in ROS scaveng-ing (Härndahl et al. 1999; Fedoroff 2006). Neta-Sharir et al.(2005) reported that HSP21 protected tomato Photosystem IIfrom temperature-dependent oxidative stress. Levine et al.

(1996) suggested that the methionine residues of the HSPsacted as endogenous antioxidants and protected cellular pro-teins from oxidative stress. Hamilton and Heckathorn (2001)reported that sHSPs, by their methionine residues, protectedcellular proteins via ROS scavenging activity, similar to anti-oxidant molecules. It could be concluded that sHSPs not onlyhave a role in the prevention of protein misfolding underoxidative stress but also have antioxidant activities.

Enhancing Arginine Pathways

Arginine, as a metabolically multifunctional amino acid, playscrucial roles not only as a proteins backbone but also as aprecursor for the biosynthesis of signaling molecules such aspolyamines (PAs; putrescine, spermidine, spermine), proline,and nitric oxide (NO) which play potential roles in the en-hancement of tolerance to CI (Mc Donald and Kushad 1986;Wang 1987; Gao et al. 2009;Morris 2009; Jubault et al. 2008).Three enzymes play pivotal roles in the arginine pathway:arginase, arginine decarboxylase (ADC), and nitric oxidesynthase (NOS; Morris 2009). Arginase catalyzes the conver-sion of arginine to ornithine, which in turn could be used forthe biosynthesis of proline and polyamines. It has been sug-gested that the biosynthesis of polyamines or proline could actas a chilling tolerance mechanism in sensitive fruits andvegetables (Zhang et al. 2011b; Shang et al. 2011).

Arginine could be converted to ornithine by arginase.Ornithine is one of the two main precursors of polyaminesand could be converted into putrescine by ornithine decarbox-ylase (ODC) enzyme activity. The second pathway for poly-amine biosynthesis is possible via the ADC enzyme which isresponsible for the conversion of arginine into putrescine. Theanti-senescence biogenic PAs with a polycationic nature atphysiological pH have the ability to bind to negativelycharged molecules such as phospholipids, proteins, andnucleic acids. PAs exhibit antioxidant activities, scavengingof ROS, and enhancement of membrane stability and integrity(Hussain et al. 2011). The interaction of PAs with the anionicgroups of membrane phospholipids could stabilize cellularmembranes under CI stress and therefore delay their disinte-gration (Groppa and Benavides 2008). It has been suggestedthat the mitigation of CI in fruits and vegetables under PAtreatment or enhanced endogenous PA status may be due totheir membrane binding capacity and antioxidant activity(Hussain et al. 2011). In pomegranate fruit, hot water treat-ment mitigated CI via the induction of polyamine accumula-tion. The alleviation of CI in pomegranate fruit treated withhot water was associated with the reduction of skin browningand electrolyte leakage and the maintenance of fruit firmness(Mirdehghan et al. 2007). Gonzales-Aguilar et al. (2000)reported that hot water treatment (53 °C for 4 min) in combi-nation with film packaging mitigated CI and spoilage inpepper fruits via enhancing the polyamine contents, which


was thought to have contributed to the maintenance of mem-brane integrity.

During cold storage of fruits and vegetables, an increase inproline content led to an increase of resistance to CI. Proline,as a multifunctional amino acid, is synthesized from glutamatein cytosol. Free proline accumulation is controlled by theincrease of biosynthesis and reduction of degradation.Proline biosynthesis via the glutamate pathway is prevalentunder stress conditions (Szabados and Savouré 2010).Glutamate is reduced to GSA by the pyrroline-5-carboxylatesynthetase (P5CS) enzyme and spontaneously converted topyrroline-5-carboxylate (P5C). P5CS activity mediates therate-limiting step in proline biosynthesis, which is controlledat the transcriptional level and through feedback inhibition byproline (Savouré et al. 1995). P5C reductase (P5CR) furtherreduces intermediate P5C to proline. As an alternative path-way, proline can be biosynthesized from ornithine, which istransaminated first by ornithine aminotransferase (OAT), pro-ducing P5C, which is then converted to proline by P5CR. Theaccumulation of proline also depends on its degradation,which occurs in the mitochondria via producing P5C fromproline by proline dehydrogenase (PDH)and the conversion ofP5C to glutamate by P5C dehydrogenase (P5CDH; Szabadosand Savouré 2010). Proline has a multifaceted nature andplays key roles in osmotic regulation between the cytoplasmand vacuole, redox regulation of the NAD+/NADH ratio,membrane stabilization, and promotion of ROS scavengingsystems (Sharp et al. 1990; Bohnert and Jensen 1996).Arginine can also be converted to NO via NOS enzymeactivity (Zhang et al. 2011b). PAs, NO, and proline as signal-ing molecules play crucial roles in enhancing resistance to CIin fruits and vegetables.

Zhang et al. (2013b) reported that hot air (38 °C for 16 h)treatment mitigated CI in tomato fruit which was accompaniedwith a reduction of electrolyte leakage and MDA content.They showed that hot air treatment enhanced arginase geneexpression, LeARG1 and LeARG2 , and its enzyme activity.Also, hot air treatment led to an increase in SOD, CAT, andAPX antioxidant enzyme activities; diminishing POX activi-ty; and enhancement of arginine, proline, and putrescine ac-cumulation. It has been suggested that a balance betweenSOD, CAT, APX, and POD activities is crucial for chillingtolerance. SOD catalyzes the dismutation of superoxide freeradicals to O2 and H2O2 (Sevillano et al. 2009). CAT, APX,and POD are crucial enzymes responsible for H2O2 scaveng-ing, but POD decomposes free radicals instead of oxygen(Safizadeh et al. 2007; Zhang et al. 2013a). Zhang et al.(2013b) reported that heat treatment decreased POD activityand increased CAT and APX activities, which not only scav-enged H2O2 but also alleviated the production of phytotoxicfree radicals decomposed by POD. The results of Zhang et al.(2013b) suggested that hot air treatment enhanced arginaseactivity which led to the mitigation of CI in tomato fruit,

perhaps by enhancing the antioxidant system activity andincrement proline status. Recently, Zhang et al. (2013c) re-ported that hot air (38 °C for 12 h) treatment mitigated CI intomato fruits. Tomato fruits treated with hot air showed higherarginase, LeARG1 and LeARG2 , gene expression. Also, themitigation of CI in tomato fruit treated with hot air wasassociated with the enhancement of ADC and ODC geneexpressions, which led to polyamine, especially Put, accumu-lation and an increase of OAT gene expression. Polyamineaccumulation and increase of OAT gene expression led toproline accumulation. Zhang et al. (2013c) suggested thathot air treatment enhanced the chilling tolerance of tomatofruit via activation of the arginine pathway.

Alteration in PAL and PPO Enzyme Activities

It is well known that when fruits and vegetables are storedunder chilling temperature, (1) PAL activity increases due tothe CI effect inducing an increase of TP that accumulates invacuoles; (2) a membrane-selective permeability loss occurs;(3) PPO activity increases in the cytoplasm that is responsiblefor IB; and (4) phenolic compounds accumulated in vacuolesleak to the cytoplasm due to loss of vacuole membrane(tonoplast) selective permeability and contribute to IB inci-dence, an effect influenced by PAL activity (Sevillano et al.2009). PAL, as a key enzyme in the phenylpropanoid path-way, catalyzes the conversion of phenylalanine to trans -cinnamic acid. PAL connected primary metabolism (shikimicacid pathway) with secondary metabolism (phenylpropanoidspathway; Dixon and Paiva 1995). In general terms, it has beenaccepted by the scientific community that an increase of PALactivity in fruit stored at chilling temperatures is part of theresponse of the plant organ in order to mitigate CI (Ismail andBrown 1979; Rinaldo et al. 2010). Postharvest heat treatmentmitigated CI in banana fruit by means of increasing PALactivity (Chen et al. 2008). In accordance with the results ofCai et al. (2006a, b), Dangcham et al. (2008), Sayyari et al.(2009), and Lu et al. (2011, 2010), Aghdam et al. (2012a)determined a decreasing PAL activity in tomato fruits treatedwith SA. Supporting the findings of Aghdam et al. (2012a)regarding PAL activity, Nguyen et al. (2004) observed thatMAP treatment significantly mitigated CI in banana fruit, andthe mitigation was associated with a diminution of PAL activ-ity. PAL activity increase was correlated with CI symptomdevelopment in mandarin fruit during cold storage. Heat treat-ment significantly mitigated CI, and this effect was associatedwith a decrease of PAL activity (Sanchez-Ballesta et al. 2000).Chen et al. (2008) reported that heat pretreatment (38 °C for2 days) mitigated CI in banana fruit during posterior storage at8 °C. Mitigation of CI was determined by a reduction ofelectrolyte leakage and MDA content. These authors showedthat the heat treatment increased PAL gene expression andenzyme activity, stimulating in that way the TP content and


ultimately enhancing CI tolerance in banana fruit. Shao andTu (2013) reported that hot air treatment (38 °C for 36 h)mitigated CI in loquat fruit, accompanied with higher extract-able juice and lower firmness, IB, and decay development.Shao and Tu (2013) reported that heat treatment enhancedantioxidant enzyme (SOD, APX, GR, and CAT) activities,which led to a decreased H2O2 level. Internal and/or externalbrowning in fruits and vegetables is due to the oxidative actionof PPO and POD on phenolics. PAL is a key enzyme in thebiosynthesis of phenolics in fruits and vegetables (Ding et al.2006). Reduction of browning in loquat fruits underpostharvest treatments may be attributed to the decrease ofPAL, PPO, and/or POD activity (Ding et al. 2006; Cao et al.2010) or decrease of the TP content (Cai et al. 2006b). Shaoand Tu (2013) reported that heat treatment diminished PPO,POD, and PAL activities and reduced TP content in loquatfruits, which contribute to the mitigation of IB. Also, Shao andTu (2013) reported that the mitigation of CI in loquat fruit wasassociated with diminishing lignin content, which may beattributed to the reduced PAL, POD, and PPO enzymeactivities.

Enhancing Sugar Metabolism

Shao et al. (2013) reported that hot air treatment (45 °C for3 h) mitigated CI in loquat fruit which was accompanied withlower firmness and IB and higher levels of extractable juice.Also, hot air treatment increased the levels of reducing sugars(glucose and fructose) and decreased the level of sucrose inloquat fruit during cold storage. The enzymes responsible forsucrose metabolism are acid invertase (AI), neutral invertase(NI), sucrose synthase (SS) which cleaves sucrose, and su-crose phosphate synthase (SPS) which is responsible for su-crose biosynthesis (Li et al. 2011). Invertases dispart sucroseto glucose and fructose. Also, SS can dispart sucrose to UDP-glucose and fructose or catalyze a reverse biosynthetic reac-tion in which SPS synthesizes sucrose-6-phosphate, which isdephosphorylated by sucrose-phosphate phosphatase to formsucrose (Mao et al. 2006). Shao et al. (2013) reported that heattreatment enhanced AI, NI, SS, and SPS enzyme activities inloquat fruit. Also, they showed that the net activity of sucrose-metabolizing enzymes, calculated by the following formula,(AI+NI+SS cleaving activities)−(SS synthetic+SPS activi-ty), was positive and increased during storage life, indicatingthat the activities of sucrose degradation enzymes are higherthan sucrose biosynthesis enzymes and that sucrose degrada-tion is prevailing in loquat fruit during storage. This scenarioled to higher glucose and fructose levels in loquat fruit treatedwith hot air. Also, Lara et al. (2009) reported that hot airtreatment (39 °C for 3 days) enhanced NI and SS activitiesin peach fruit, which led to a decrease in sucrose and anincrease in reducing sugar levels. Increase in reducing sugarcontent under heat treatment was also reported byMirdehghan

et al. (2006), who reported that pomegranate fruit treated withhot water (45 °C for 4 min) exhibited higher reducing sugar(glucose and fructose) and organic acid (malic, citric, andoxalic acids) contents as well as higher total antioxidantactivity. Shao et al. (2013) reported that heat-treated loquatfruit showed higher APX and GR activities and AA and GSHcontents, which may contribute to diminishing H2O2 accumu-lation and enhancing chilling tolerance.

Sugar metabolism is essential for the biosynthesis of anti-oxidant molecules which are crucial for the protection offruit and vegetable cells against oxidative chilling stress(Couée et al. 2006). Enhanced glucose state in loquat fruittreated with hot air may activate the oxidative pentose phos-phate pathway and lead to supplying higher NADPH, a majorreducing molecule in the AA-GSH cycle (Carvalho 2008). Liuet al. (2013a) reported that glucose-6-phosphate dehydroge-nase (G6PDH), as a rate-limiting enzyme in the pentose phos-phate pathway, plays a pivotal role in the mitigation of droughtstress with oxidative facet in soybean roots by enhancing GR,DHAR, and MDHAR enzyme activities, which led to in-creased AA and GSH status. Also, Sinkevich et al. (2010)reported that transgenic potato plants overexpressing yeastinvertase showed significantly less MDA content under coldstress. They suggested that the invertase gene expression im-proved cold tolerance via enhancing the antioxidant systemactivity of potato plants (Sinkevich et al. 2010). Also, glucoseis a powerful precursor for AA biosynthesis (Smirnoff et al.2001) and for carbon skeletons of amino acids such asglutamic acid, which are the backbone of GSH biosynthesis(Noctor and Foyer 1998). Therefore, higher glucose content inloquat fruit treated with hot air may contribute to the improve-ment of AA and GSH contents, enhancement of APX and GRactivity, activation of the AA/GSH cycle, and mitigation ofoxidative stress. The protective roles of soluble sugars againstoxidative stress not only are attributed to the increment ofantioxidant system activity but also are due to their ROSscavenging activity (Van den Ende and Valluru 2009). Liet al. (2012) reported that the enhanced expression of sHSPsunder heat stress correlates with the enhanced vacuolar inver-tase gene expression and enzyme activity in tomato fruit. Liuet al. (2013b) suggested that sugar metabolism plays a pivotalrole in the mitigation of oxidative stress via facilitating HSPsas well as antioxidant molecules such as AA and GSH accu-mulation which contributed to the maintenance of membraneintegrity and protein function.

An emerging scenario suggested that hexokinase (HK)activity may regulate ROS production (Bolouri-Moghaddamet al. 2010). Bolouri-Moghaddam et al. (2010) reported thatHK was a powerful glucose sensor, and its activity in themitochondria regulated glucose-6-phosphate and ROS status,activation of the antioxidant system, and the biosynthesis ofphenolics. Bolouri-Moghaddam et al. (2010) suggested thatthe synergistic action of sugars and phenolics played a key


role in redox system, scavenging ROS and improving chillingstress tolerance. Cao et al. (2013) reported that the hightolerance of Ninghaibai cv. of loquat fruit to CI in comparisonwith Dahongpao cv., which is sensitive to CI during coldstorage (1 °C), was attributed to (1) the higher glucose andfructose contents as reducing sugars and lower sucrose contentas a non-producing sugar due to the lower sucrose biosynthe-sis enzyme activities such as SPS and higher sucrose degra-dations enzyme activities such as SS and invertase and (2) thehigher HK and phosphor fructokinase (PFK) enzyme activi-ties which play crucial roles in the defense responses of loquatfruits to chilling stress. The authors showed that “Ninghaibai”cv. had higher activities of HK and PFK, which would bebeneficial in hexose phosphorylation and sugar signal gener-ation when the fruit was under chilling stress (Cao et al. 2013).

Limitation for Heat Treatments

It has been reported that the use of inappropriate heat treat-ments leads to the damage of fruits and vegetables. Trying tofind an appropriate time–temperature regime for fruits andvegetables is necessary for agro-food companies. The toler-ance of fruits and vegetables to heat treatments was deter-mined by species; cultivar; maturity at harvest; pre-harvestfactors such as season, growing location, soil type, and pro-duction practices; and handling between harvest and treatment(Fallik 2004; Valero and Serrano 2010). As a general rule,when treating at higher temperatures, the time should beshorter in order to avoid heat damage. Fruit and vegetabletissue damage may be both external (such as peel browning,

pitting, yellowing, and decay development) and internal (suchas poor color development, abnormal softening, lack of starchbreakdown, flesh darkening, and development of internalcavities; Valero and Serrano 2010).

Concluding Remarks and Future Perspectives

Tropical and subtropical fruits and vegetables are sensitive tolow temperatures and suffer from CI. The incidence of thisphysiological disorder limits the use of low-temperature stor-age, which is employed most widely for lowering the metab-olism and risks of decay, thus reaching a longer shelf life ofplant commodities. Membrane damage and ROS productionare multifarious adverse effects of chilling as oxidative stressin sensitive fruits and vegetables. Today, postharvest technol-ogies are employed in order to inhibit or reduce the impact ofCI in sensitive fruits and vegetables of high commercialinterest. The technologies may have physical, chemical, orbiotechnological nature. The use of heat treatments is actuallyconsidered as an environment-friendly technology for CI mit-igation. From the results presented herein, we conclude thatheat treatments enhanced chilling tolerance in fruits and veg-etables, which were attributed to (1) enhanced membraneintegrity by enhancing the unSFA/SFA ratio; (2) enhancedHSP gene expression and accumulation; (3) enhanced antiox-idant system activity; (4) enhanced arginine pathways whichled to the accumulation of signaling molecules with pivotalroles in improving chilling tolerance, such as polyamines,nitric oxide, and proline; (5) enhanced PAL and PPO enzymeactivities; and (6) enhanced sugar metabolism (Fig. 2). Taken

Fig. 2 Schematic overview of themechanisms by which heattreatments enhance chillingtolerance in fruits and vegetables


together, a deep understanding of the physiological, biochem-ical, and molecular mechanisms employed by heat treatmentwill enable us to provide new precise and effective hot treat-ment strategies for the amelioration of CI in fruits and vege-tables with attractive economic perspectives.

Acknowledgments We are extremely grateful to Dr. Francisco B.Flores, CEBAS-CSIC, Campus de Espinardo, Espinardo-Murcia, Spain,and Dr. Laura Sevillano, IBFG-UAL/CSIC, Edificio Departamental,Campus Miguel de Unamuno, Salamanca, Spain, for their valuablecomments on the manuscript.

References

Aghdam, M. S., Asghari, M., Moradbeygi, H., Mohammadkhani, N.,Mohayeji, M., & Rezapour-Fard, J. (2012a). Effect of postharvestsalicylic acid treatment on reducing chilling injury in tomato fruit.Romanian Biotechnological Letters, 17 , 7466–7473.

Aghdam, M. S., Hassanpouraghdam, M. B., Paliyath, G., & Farmani, B.(2012b). The language of calcium in postharvest life of fruits,vegetables and flowers. Scientia Horticulturae, 144 , 102–115.

Aghdam, M. S., Sevillano, L., Flores, F. B., & Bodbodak, S. (2013). Heatshock proteins as biochemical markers for postharvest chilling stressin fruits and vegetables. Scientia Horticulturae, 160 , 54–64.

Al-Whaibi, M. H. (2011). Plant heat-shock proteins: a mini review.Journal of King Saud University—Science, 23 , 139–150.

Artés, F., Tudela, J. A., & Villaescusa, R. (2000). Thermal postharvesttreatments for improving pomegranate quality and shelf life.Postharvest Biology and Technology, 18, 245–251.

Autio, W. R., & Bramlage, W. J. (1987). Chilling sensitivity of tomatofruit in relation to ripening and senescence. Journal of the AmericanSociety for Horticultural Science, 11 , 1201–1204.

Bassal, M., & El-Hamahmy, M. (2011). Hot water dip and preconditioningtreatments to reduce chilling injury and maintain postharvest qualityof Navel and Valencia oranges during cold quarantine. PostharvestBiology and Technology, 60, 186–191.

Bhattacharjee, S. (2012). The language of reactive oxygen species sig-naling in plants. Journal of Botany, 2012 , 1–22.

Bohnert, H. J., & Jensen, R. G. (1996). Strategies for engineering water-stress tolerance in plants. Trends in Biotechnology, 14 , 89–97.

Bolouri-Moghaddam, M. R., Le Roy, K., Xiang, L., Rolland, F., & Vanden Ende, W. (2010). Sugar signalling and antioxidant networkconnections in plant cells. FEBS Journal, 277 , 2022–2037.

Boston, R. S., Viitanen, P. V., & Vierling, E. (1996). Molecular chaper-ones and protein folding in plants. Plant Molecular Biology, 32 ,191–222.

Brown, D. J., & Beevers, H. (1987). Fatty acids of rice coleoptiles in airand anoxia. Plant Physiology, 84, 555–559.

Cai, C., Chen, K., Xu, W., Zhang, W., Li, X., & Ferguson, I. (2006a).Effect of 1-MCP on postharvest quality of loquat fruit. PostharvestBiology and Technology, 40, 155–162.

Cai, C., Xu, C., Shan, L., Li, X., Zhou, C., Zhang, W., et al. (2006b). Lowtemperature conditioning reduces postharvest chilling injury in lo-quat fruit. Postharvest Biology and Technology, 41, 252–259.

Cao, S., Hu, Z., Zheng, Y., & Lu, B. (2010). Synergistic effect of heattreatment and salicylic acid on alleviating internal browning in cold-stored peach fruit. Postharvest Biology and Technology, 58, 93–97.

Cao, S., Yang, Z., Cai, Y., & Zheng, Y. (2011). Fatty acid composition andantioxidant system in relation to susceptibility of loquat fruit tochilling injury. Food Chemistry, 127 , 1777–1783.

Cao, S., Yang, Z., & Zheng, Y. (2013). Sugar metabolism in relation tochilling tolerance of loquat fruit. Food Chemistry, 136 , 139–143.

Chen, J. Y., He, L. H., Jiang, Y. M.,Wang, Y., Joyce, D. C., Ji, Z. L., et al.(2008). Role of phenylalanine ammonia-lyase in heat pretreatment-induced chilling tolerance in banana fruit. Physiology Plantarum,132 , 318–328.

Couée, I., Sulmon, C., Gouesbet, G., & El Amrani, A. (2006).Involvement of soluble sugars in reactive oxygen species balanceand responses to oxidative stress in plants. Journal of ExperimentalBotany, 57 , 449–459.

Craig, E. A., Weissman, J. S., & Horwich, A. L. (1994). Heat shockproteins and molecular chaperones: mediators of protein conforma-tion and turnover in the cell. Cell, 78 , 365–372.

Crawford, R.M.M., & Braendle, R. (1996). Oxygen deprivation stress ina changing environment. Journal of Experimental Botany, 47, 145–159.

Dangcham, S., Bowen, J., Ferguson, I. B., & Ketsa, S. (2008). Effect oftemperature and low oxygen on pericarp hardening of mangosteenfruit stored at low temperature.Postharvest Biology and Technology,50, 37–44.

de Carvalho, M. H. C. (2008). Drought stress and reactive oxygenspecies: production, scavenging and signaling. Plant Signalingand Behaviour, 3 , 156–165.

Ding, Z., Tian, S., Wang, Y., Li, B., Chan, Z., Han, J., et al. (2006).Physiological response of loquat fruit to different storage conditionsand its storability. Postharvest Biology and Technology, 41 , 143–150.

Dixon, R. A., & Paiva, N. L. (1995). Stress-induced phenylpropanoidmetabolism. The Plant Cell, 7 , 1085–1097.

Ellis, R. J., & van der Vies, S. M. (1991). Molecular chaperones. AnnualReview of Biochemistry, 60, 321–347.

Fallik, E. (2004). Prestorage hot water treatments (immersion, rinsing andbrushing). Postharvest Biology and Technology, 32, 125–134.

Fedoroff, N. (2006). Redox regulatory mechanisms in cellular stressresponses. Annals of Botany, 98, 289–300.

Fung, R. W. M., Wang, C. Y., Smith, D. L., Gross, K. C., & Tian, M.(2004). MeSA and MeJA increase steady-state transcript levels ofalternative oxidase and resistance against chilling injury in sweetpeppers (Capsicum annuum L.). Plant Science, 166 , 711–719.

Gao, H.-J., Yang, H.-Q., & Wang, J.-X. (2009). Arginine metabolism inroots and leaves of apple (Malus domestica Borkh.): the tissue-specific formation of both nitric oxide and polyamines. ScientiaHorticulturae, 119, 147–152.

Ghasemnezhad, M., Marsh, K., Shilton, R., Babalar, M., & Woolf, A.(2008). Effect of hot water treatments on chilling injury and heatdamage in ‘satsuma’ mandarins: antioxidant enzymes and vacuolarATPase, and pyrophosphatase. Postharvest Biology andTechnology, 48 , 364–371.

Gómez, P., Ferrer, M. A., Fernández-Trujillo, J. P., Calderon, A., Artés, F.,Egea-Cortines, M., et al. (2009). Structural changes, chemical com-position and antioxidant activity of cherry tomato fruits (cv. Micro-Tom) stored under optimal and chilling conditions. Journal of theScience of Food and Agriculture, 89 , 1543–1551.

González-Aguilar, G. A., Gayosso, L., Cruz, R., Fortiz, J., Báez, R., &Wang, C. Y. (2000). Polyamines induced by hot water treatmentsreduce chilling injury and decay in pepper fruit. Postharvest Biologyand Technology, 18, 19–26.

Groppa,M.D., & Benavides,M. P. (2008). Polyamines and abiotic stress:recent advances. Amino Acids, 34, 35–45.

Gusev, N., Bogatcheva, N., & Marston, S. (2002). Structure and proper-ties of small heat shock proteins (sHsp) and their interaction withcytoskeleton proteins. Biochemistry (Moscow), 67, 511–519.

Hamilton, E. W., & Heckathorn, S. A. (2001). Mitochondrial adaptationto NaCl. Complex I is protected by anti-oxidants and small heatshock proteins, whereas complex II is protected by proline andbetaine. Plant Physiology, 126 , 1266–1274.

Härndahl, U., Hall, R. B., Osteryoung, K.W., Vierling, E., Bornman, J. F.,& Sundby, C. (1999). The chloroplast small heat shock proteinundergoes oxidation-dependent conformational changes and may


protect plants from oxidative stress.Cell Stress Chaperones, 4, 129–138.

He, L. H., Chen, J. Y., Kuang, J. F., & Lu, W. J. (2012). Expression ofthree sHSP genes involved in heat pretreatment-induced chillingtolerance in banana fruit. Journal of the Science of Food andAgriculture, 92 , 1924–1930.

Hernández, M. L., Padilla, M. N., Sicardo, M. D., Mancha, M., &Martínez-Rivas, J. M. (2011). Effect of different environmentalstresses on the expression of oleate desaturase genes and fatty acidcomposition in olive fruit. Phytochemistry, 72 , 178–187.

Hodges, D. M., DeLong, J. M., Forney, C. F., & Prange, R. K. (1999).Improving the thiobarbituric acid-reactive-substances assay for es-timating lipid peroxidation in plant tissues containing anthocyaninand other interfering compounds. Planta, 207 , 604–611.

Hodges, D. M., Lester, G. E., Munro, K. D., & Toivonen, P. (2004).Oxidative stress: importance for postharvest quality: oxidativestress: postharvest fruits and vegetables.HortScience, 39, 924–929.

Horváth, I., Multhoff, G., Sonnleitner, A., & Vígh, L. (2008). Membrane-associated stress proteins: more than simply chaperones. Biochimicaet Biophysica Acta (BBA)—Biomembranes, 1778 , 1653–1664.

Hussain, S. S., Ali, M., Ahmad, M., & Siddique, K. H. M. (2011).Polyamines: natural and engineered abiotic and biotic stress toler-ance in plants. Biotechnology Advances, 29, 300–311.

Ismail, M. A., & Brown, G. E. (1979). Postharvest wound healing incitrus fruit: induction of phenylalanine ammonia-lyase in injured‘Valencia’ orange flavedo. Journal of the American Society forHorticultural Science, 104 , 126–129.

Jubault, M., Hamon, C., Gravot, A., Lariagon, C., Delourme, R.,Bouchereau, A., et al. (2008). Differential regulation of root argininecatabolism and polyamine metabolism in clubroot-susceptible andpartially resistant Arabidopsis genotypes. Plant Physiology, 146 ,2008–2019.

Lara, M. V., Borsani, J., Budde, C. O., Lauxmann, M. A., Lombardo, V.A., Murray, R., et al. (2009). Biochemical and proteomic analysis of‘Dixiland’ peach fruit (Prunus persica ) upon heat treatment.Journal of Experimental Botany, 60, 4315–4333.

Larkindale, J., Hall, J. D., Knight, M. R., & Vierling, E. (2005). Heatstress phenotypes of Arabidopsis mutants implicate multiple signal-ing pathways in the acquisition of thermotolerance. PlantPhysiology, 138 , 882–897.

Lee, G. J. (1995). Assaying proteins for molecular chaperone activity.Methods in Cell Biology, 50, 325–334.

Levine, R. L., Mosoni, L., Berlett, B. S., & Stadtman, E. R. (1996).Methionine residues as endogenous antioxidants in proteins.Proceedings of the National Academy of Sciences U S A, 93 ,15036–15040.

Li, W., Shao, Y., Chen, W., & Jia, W. (2011). The effects of harvestmaturity on storage quality and sucrose-metabolizing enzymes dur-ing banana ripening. Food and Bioprocess Technology, 4 , 1273–1280.

Li, Z., Palmer, W.M., Martin, A. P., Wang, R., Rainsford, F., Jin, Y., et al.(2012). High invertase activity in tomato reproductive organs corre-lates with enhanced sucrose import into, and heat tolerance of,young fruit. Journal of Experimental Botany, 63, 1155–1166.

Liu, J., Wang, X., Hu, Y., Hu, W., & Bi, Y. (2013a). Glucose-6-1phosphate dehydrogenase plays a pivotal role in tolerance to droughtstress in soybean roots. Plant Cell Reports, 32, 415–429.

Liu, Y.H., Offler, C.E., & Ruan, Y.L. (2013b). Regulation of fruit andseed response to heat and drought by sugars as nutrients and signals.Frontiers in Plant Science , 4 , 282.

Los, D. A., & Murata, N. (1998). Structure and expression of fatty aciddesaturases. Biochimica et Biophysica Acta (BBA)—Lipids andLipid Metabolism, 1394, 3–15.

Los, D. A., & Murata, N. (2004). Membrane fluidity and its roles in theperception of environmental signals. Biochimica et Biophysica Acta(BBA)—Biomembranes, 1666, 142–157.

Lu, X., Sun, D., Li, Y., Shi, W., & Sun, G. (2011). Pre- and post-harvestsalicylic acid treatments alleviate internal browning and maintainquality of winter pineapple fruit. Scientia Horticulturae, 130 , 97–101.

Lurie, S. (2008). Heat treatment for enhancing postharvest quality. In P.Paliyath, D. P. Murr, A. V. Handa, & S. Lurie (Eds.), Postharvestbiology and technology of fruits, vegetables, and flowers (pp. 246–259). Ames, IA: Wiley-Blackwell.

Lurie, S., Handros, A., Fallik, E., & Shapira, R. (1996). Reversibleinhibition of tomato fruit gene expression at high temperature (ef-fects on tomato fruit ripening). Plant Physiology, 110 , 1207–1214.

Lyons, J. M. (1973). Chilling injury in plants. Annual Review of PlantPhysiology, 24, 445–466.

Maalekuu, K., Elkind, Y., Leikin-Frenkel, A., Lurie, S., & Fallik, E.(2006). The relationship between water loss, lipid content, mem-brane integrity and LOX activity in ripe pepper fruit after storage.Postharvest Biology and Technology, 42, 248–255.

Mao, L., Que, F., &Wang, G. (2006). Sugar metabolism and involvementof enzymes in sugarcane (Saccharum officinarum L.) stems duringstorage. Food Chemistry, 98 , 338–342.

Mao, L. C., Wang, G. Z., Zhu, C. G., & Pang, H. Q. (2007a). Involvementof phospholipase D and lipoxygenase in response to chilling stressin postharvest cucumber fruits. Plant Science, 172 , 400–405.

Mao, L., Pang, H., Wang, G., & Zhu, C. (2007b). Phospholipase D andlipoxygenase activity of cucumber fruit in response to chilling stress.Postharvest Biology and Technology, 44, 42–47.

Marangoni, A. G., Palma, T., & Stanley, D. W. (1996). Membrane effectsin postharvest physiology. Postharvest Biology and Technology, 7 ,193–217.

Maxwell, D. P., Wang, Y., & McIntosh, L. (1999). The alternativeoxidase lowers mitochondrial reactive oxygen production in plantcells. Proceedings of the National Academy of Sciences USA, 96 ,8271–8276.

Mc Donald, R. E., & Kushad, M. M. (1986). Accumulation of putrescineduring chilling injury of fruits. Plant Physiology, 82, 324–326.

Mc Donald, R. E., Mc Collum, T. G., & Nordby, H. E. (1993).Temperature conditioning and surface treatments of grapefruit affectexpression of chilling injury and gas diffusion. Journal of theAmerican Society for Horticultural Science, 118, 490–496.

Miller, W. R., Chun, D., Risse, L. A., Hatton, T. T., & Hinsch, R. T.(1990). Conditioning of Florida grapefruit to reduce peel stressduring low-temperature storage. Hort Science, 25, 209–211.

Mirdehghan, S. H., Rahemi, M., Serrano, M., Guillén, F., Martínez-Romero, D., & Valero, D. (2006). Prestorage heat treatment tomaintain nutritive and functional properties during postharvest coldstorage of pomegranate. Journal of Agricultural and FoodChemistry, 54, 8495–8500.

Mirdehghan, S. H., Rahemi, M., Martínez-Romero, D., Guillén, F.,Valverde, J. M., Zapata, P. J., et al. (2007). Reduction of pomegran-ate chilling injury during storage after heat treatment: role of poly-amines. Postharvest Biology and Technology, 44, 19–25.

Mittler, R. (2002). Oxidative stress, antioxidants and stress tolerance.Trends in Plant Science, 7 , 405–410.

Mittler, R., & Zilinskas, B. A. (1992). Molecular cloning and character-ization of a gene encoding pea cytosolic ascorbate peroxidase.Journal of Biological Chemistry, 267 , 21802–21807.

Møller, I. M. (2001). Plant mitochondria and oxidative stress: electrontransport, NADPH turnover, and metabolism of reactive oxygenspecies. Annual Review of Plant Physiology and Plant MolecularBiology, 52, 561–591.

Morris, S. M., Jr. (2009). Recent advances in arginine metabolism: rolesand regulation of the arginases. British Journal of Pharmacology,157 , 922–930.

Nakamoto, H., & Vigh, L. (2007). The small heat shock proteins and theirclients. Cellular and Molecular Life Science, 64(3), 294–306.

Narvaez-Cuenca, C. E., Espinal-Ruiz, M., & Restrepo-Sanchez,L.-P. (2011). Heat shock reduces both chilling injury and the


overproduction of reactive oxygen species in yellow pitaya(Hylocereus megalanthus) fruits. Journal of Food Quality, 34 ,327–332.

Neta-Sharir, I., Isaacson, T., Lurie, S., & Weiss, D. (2005). Dual role fortomato heat shock protein 21: protecting photosystem II from oxi-dative stress and promoting color changes during fruit maturation.The Plant Cell, 17, 1829–1838.

Nguyen, T. B. T., Ketsa, S., & van Doorn, W. G. (2004). Effect ofmodified atmosphere packaging on chilling-induced peel browningin banana. Postharvest Biology and Technology, 31 , 313–317.

Noctor, G., & Foyer, C. H. (1998). Ascorbate and glutathione: keepingactive oxygen under control. Annual Review of Plant Physiologyand Plant Molecular Biology, 49 , 249–279.

Nordby, H. E., & Mc Donald, R. E. (1991). Relationship of epicuticularwax composition of grapefruit to chilling. Journal of Agricultureand Food Chemistry, 39 , 957–962.

Panchuk, I. I., Volkov, R. A., & Schoffl, F. (2002). Heat stress- and heatshock transcription factor-dependent expression and activity of ascor-bate peroxidase in Arabidopsis . Plant Physiology, 129, 838–853.

Pavoncello, D., Lurie, S., Droby, S., & Porat, R. (2001). A hot watertreatment induces resistance to Penicillium digitatum and promotesthe accumulation of heat shock and pathogenesis-related proteins ingrapefruit flavedo. Physiologia Plantarum, 111 , 17–22.

Pinhero, R. G., Paliyath, G., Yada, R. Y., & Murr, D. P. (1998).Modulation of phospholipase D and lipoxygenase activities duringchilling. Relation to chilling tolerance of maize seedlings. PlantPhysiology and Biochemistry, 36, 213–224.

Polenta, G. A., Calvete, J. J., & Gonzalez, C. B. (2007). Isolation andcharacterization of the main small heat shock proteins induced intomato pericarp by thermal treatment. FEBS Journal, 274 , 6447–6455.

Porat, R., Pavoncello, D., Ben-Hayyim, G., & Lurie, S. (2002a). A heattreatment induced the expression of a Na+/H+ antiport gene(cNHX1) in citrus fruit. Plant Science, 162 , 957–963.

Porat, R., Pavoncello, D., Lurie, S., & McCollum, T. G. (2002b).Identification of a grapefruit cDNA belonging to a unique classof citrus dehydrins and characterization of its expression patternsunder temperature stress conditions. Physiologia Plantarum, 115 ,598–603.

Porat, R., Pasentsis, K., Rozentzvieg, D., Gerasopoulos, D., Falara, V.,Samach, A., et al. (2004). Isolation of a dehydrin cDNA from orangeand grapefruit citrus fruit that is specifically induced by the combi-nation of heat followed by chilling temperatures. PhysiologiaPlantarum, 120 , 256–264.

Purvis, A. C. (1997). Role of the alternative oxidase in limiting superox-ide production by plant mitochondria. Physiologia Plantarum, 100 ,165–170.

Rinaldo, D., Mbéguié-A-Mbéguié, D., & Fils-Lycaon, B. (2010).Advances on polyphenols and their metabolism in sub-tropical andtropical fruits. Trends in Food Science and Technology, 21, 599–606.

Rozenzvieg, D., Elmaci, C., Samach, A., Lurie, S., & Porat, R. (2004).Isolation of four heat shock protein cDNAs from grapefruit peel tissueand characterization of their expression in response to heat andchilling temperature stresses. Physiologia Plantarum, 121 , 421–428.

Rui, H., Cao, S., Shang, H., Jin, P.,Wang, K., & Zheng, Y. (2010). Effectsof heat treatment on internal browning and membrane fatty acid inloquat fruit in response to chilling stress. Journal of the Science ofFood and Agriculture, 90, 1557–1561.

Sabehat, A., Weiss, D., & Lurie, S. (1996). The correlation between heat-shock protein accumulation and persistence and chilling tolerance intomato fruit. Plant Physiology, 110, 531–537.

Sabehat, A., Lurie, S., & Weiss, D. (1998a). Expression of small heat-shock proteins at low temperatures. A possible role in protectingagainst chilling injuries. Plant Physiology, 117, 651–658.

Sabehat, A., Weiss, D., & Lurie, S. (1998b). Heat-shock proteins andcross-tolerance in plants. Physiologia Plantarum, 103 , 437–441.

Safizadeh, M., Rahemi, M., & Aminlari, M. (2007). Effect of postharvestcalcium and hot-water dip treatments on catalase, peroxidase andsuperoxide dismutase in chilled Lisbon lemon fruit. InternationalJournal of Agricultural Research, 2 , 440–449.

Sakamoto, T., & Murata, N. (2002). Regulation of the desaturation offatty acids and its role in tolerance to cold and salt stress. CurrentOpinion in Microbiology, 5 , 206–210.

Sala, J. M. (1998). Involvement of oxidative stress in chilling injury incold-stored mandarin fruits. Postharvest Biology and Technology,13, 255–261.

Sanchez-Ballesta, M. T., Zacarias, L., Granell, A., & Lafuente, M. T.(2000). Accumulation of PAL transcript and PAL activity as affectedby heat-conditioning and low-temperature storage and its relation tochilling sensitivity in mandarin fruits. Journal of Agriculture andFood Chemistry, 48, 2726–2731.

Sánchez-Bel, P., Egea, I., Sánchez-Ballesta, M. T., Martinez-Madrid, C.,Fernandez-Garcia, N., Romojaro, F., et al. (2012). Understandingthe mechanisms of chilling injury in bell pepper fruits using theproteomic approach. Journal of Proteomics, 75, 5463–5478.

Savouré, A., Jaoua, S., Hua, X. J., Ardiles, W., Van Montagu, M., &Verbruggen, N. (1995). Isolation, characterization, and chromosom-al location of a gene encoding the Δ-pyrroline-5-carboxylate syn-thetase in Arabidopsis thaliana . FEBS Letters, 372 , 13–19.

Sayyari, M., Babalar, M., Kalantari, S., Serrano, M., & Valero, D. (2009).Effect of salicylic acid treatment on reducing chilling injury in storedpomegranates. Postharvest Biology and Technology, 53 , 152–154.

Schoffl, F., Prandl, R., & Reindl, A. (1998). Regulation of the heat-shockresponse. Plant Physiology, 117, 1135–1141.

Sevillano, L., Sanchez-Ballesta, M. T., Romojaro, F., & Flores, F. B.(2009). Physiological, hormonal and molecular mechanisms regu-lating chilling injury in horticultural species. Postharvest technolo-gies applied to reduce its impact. Journal of the Science of Food andAgriculture, 89 , 555–573.

Sevillano, L., Sola, M. M., & Vargas, A. M. (2010). Induction of smallheat-shock proteins in mesocarp of cherimoya fruit (Annonacherimola Mill.) produces chilling tolerance. Journal of FoodBiochemistry, 34 , 625–638.

Shang, H., Cao, S., Yang, Z., Cai, Y., & Zheng, Y. (2011). Effect ofexogenous gamma-aminobutyric acid treatment on proline accumu-lation and chilling injury in peach fruit after long-term cold storage.Journal of Agriculture and Food Chemistry, 59, 1264–1268.

Shao, X., & Tu, K. (2013). Hot air treatment improved the chillingresistance of loquat fruit under cold storage. Journal of FoodProcessing and Preservation . doi:10.1111/jfpp.12019.

Shao, X., Zhu, Y., Cao, S., Wang, H., & Song, Y. (2013). Soluble sugarcontent and metabolism as related to the heat-induced chillingtolerance of loquat fruit during cold storage. Food and BioprocessTechnology. doi:10.1007/s11947-012-1011-6.

Sharom, M., Willemot, C., & Thompson, J. E. (1994). Chilling injuryinduces lipid phase changes in membranes of tomato fruit. PlantPhysiology, 105 , 305–308.

Sharp, R. E., Hsiao, T. C., & Silk, W. K. (1990). Growth of the maizeprimary root at low water potentials: II. Role of growth and depo-sition of hexose and potassium in osmotic adjustment. PlantPhysiology, 93, 1337–1346.

Sinkevich, M. S., Naraykina, N. V., & Trunova, T. I. (2010). Involvementof sugars in the antioxidant defense against paraquat-induced oxi-dative stress in potato transformed with yeast invertase gene.Doklady Biological Sciences, 434 , 338–340.

Smirnoff, N., Conklin, P. L., & Loewus, F. A. (2001). Biosynthesis ofascorbic acid in plants: a renaissance. Annual Review of PlantPhysiology and Plant Molecular Biology, 52 , 437–467.

Sorger, P. K., & Nelson, H. C. (1989). Trimerization of a yeast transcrip-tional activator via a coiled-coil motif. Cell, 59, 807–813.

Szabados, L., & Savouré, A. (2010). Proline: a multifunctional aminoacid. Trends in Plant Science, 15 , 89–97.


http://dx.doi.org/10.1111/jfpp.12019

http://dx.doi.org/10.1007/s11947-012-1011-6

Thomashow, M. F. (1999). Plant cold acclimation: freezing tolerancegenes and regulatory mechanisms. Annual Review of PlantPhysiology and Plant Molecular Biology, 50 , 571–599.

Timperio, A. M., Egidi, M. G., & Zolla, L. (2008). Proteomics applied onplant abiotic stresses: role of heat shock proteins (HSP). Journal ofProteomics, 71 , 391–411.

Török, Z., Goloubinoff, P., Horvath, I., Tsvetkova, N. M., Glatz, A.,Balogh, G., et al. (2001). Synechocystis HSP17 is an amphitropicprotein that stabilizes heat-stressed membranes and binds denaturedproteins for subsequent chaperone-mediated refolding. Proceedingsof the National Academy of Sciences USA, 98, 3098–3103.

Tsvetkova, N. M., Horvath, I., Torok, Z., Wolkers, W. F., Balogi, Z.,Shigapova, N., et al. (2002). Small heat-shock proteins regulatemembrane lipid polymorphism. Proceedings of the NationalAcademy of Sciences USA, 99, 13504–13509.

Valero, D., & Serrano,M. (2010).Postharvest biology and technology forpreserving fruit quality. Boca Raton, FL: CRC.

Van den Ende, W., & Valluru, R. (2009). Sucrose, sucrosyl oligosaccha-rides, and oxidative stress: scavenging and salvaging? Journal ofExperimental Botany, 60, 9–18.

Wang, C. Y. (1982). Physiological and biochemical responses of plants tochilling stress. Hort Science, 17, 173–186.

Wang, C. Y. (1987). Changes of polyamines and ethylene in cucumberseedling in response to chilling stress. Physiologia Plantarum, 69 ,253–257.

Wang,W., Vinocur, B., Shoseyov, O., & Altman, A. (2004). Role of plantheat-shock proteins and molecular chaperones in the abiotic stressresponse. Trends in Plant Science, 9 , 244–252.

Wang, L., Chen, S., Kong, W., Li, S., & Archbold, D. D. (2006).Salicylic acid pretreatment alleviates chilling injury and af-fects the antioxidant system and heat shock proteins ofpeaches during cold storage. Postharvest Biology and Technology,41 , 244–251.

Wang, H., Zhang, Z., Xu, L., Huang, X., & Pang, X. (2012). The effect ofdelay between heat treatment and cold storage on alleviation ofchilling injury in banana fruit. Journal of the Science of Food andAgriculture, 92 , 2624–2629.

Wild, B. L. (1993). Reduction of chilling injury in grapefruit and orangesstored at 1°C by prestorage hot dip treatments, curing, and wax

application. Australian Journal of Experimental Agriculture, 33,495–498.

Wise, R. R., & Naylor, A. W. (1987). Chilling-enhanced photooxidationevidence for the role of singlet oxygen and superoxide in thebreakdown of pigments and endogenous antioxidants. PlantPhysiology, 83, 278–282.

Yu, C., Wang, H. S., Yang, S., Tang, X. F., Duan, M., & Meng, Q. W.(2009). Overexpression of endoplasmic reticulum omega-3 fattyacid desaturase gene improves chilling tolerance in tomato. PlantPhysiology and Biochemistry, 47, 1102–1112.

Zhang, J., Huang, W., Pan, Q., & Liu, Y. (2005). Improvement of chillingtolerance and accumulation of heat shock proteins in grape berries(Vitis vinifera cv. Jingxiu) by heat pretreatment. Postharvest Biologyand Technology, 38(1), 80–90.

Zhang, L., Yu, Z., Jiang, L., Jiang, J., Luo, H., & Fu, L. (2011a). Effect ofpost-harvest heat treatment on proteome change of peach fruitduring ripening. Journal of Proteomics, 74, 1135–1149.

Zhang, X., Shen, L., Li, F., Meng, D., & Sheng, J. (2011b). Methylsalicylate-induced arginine catabolism is associated with up-regulation of polyamine and nitric oxide levels and improves chill-ing tolerance in cherry tomato fruit. Journal of Agriculture and FoodChemistry, 59, 9351–9357.

Zhang, X., Shen, L., Li, F., Meng, D., & Sheng, J. (2013a).Amelioration of chilling stress by arginine in tomato fruit:changes in endogenous arginine catabolism. Postharvest Biologyand Technology, 76, 106–111.

Zhang, X., Shen, L., Li, F., Meng, D., & Sheng, J. (2013b).Arginase induction by heat treatment contributes to amelio-ration of chilling injury and activation of antioxidant en-zymes in tomato fruit. Postharvest Biology and Technology,79 , 1–8.

Zhang, X., Shen, L., Li, F., Meng, D., & Sheng, J. (2013c). Hot airtreatment-induced arginine catabolism is associated with elevatedpolyamines and proline levels and alleviates chilling injury inpostharvest tomato fruit. Journal of the Science of Food andAgriculture , 93, 3245–3251.

Zou, J., Liu, C., Liu, A., Zou, D., & Chen, X. (2012). Overexpression ofOsHsp17.0 and OsHsp23.7 enhances drought and salt tolerance inrice. Journal of Plant Physiology, 169 , 628–635.


postharvest heat treatment for mitigation of chilling injury in fruits and vegetables

Documents