bakeries and confectioneries

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19Bakeries and

ConfeCtioneries

C O N C H A C O L L A R A N D C R I S T I N A M . RO S E L L

Contents

19.1 Introduction 56019.2 By-ProductsandWastesGeneratedduringProcessing

ofFoodProductsinBakeriesandConfectioneries:QualitativeandQuantitativeAspects 561

19.3 PotentialoftheBy-ProductsfromBakeriesandConfectioneriesforProspectiveProductionofBiologicalofCommercialSignificance 56319.3.1 UseofCerealBy-ProductsasAnimalFeed 564

19.3.1.1 SeparationofBakeryProducts 56619.3.1.2 ProcessingofBakeryWasteforFeed

Preparation 56619.3.1.3 CommercialProductsforFeeding

ObtainedfromBakeryWaste 56819.3.2 ProductionofSourdoughfromBakery By-Products 56819.3.3 ProductionofSugarsorPolysaccharides 57019.3.4 IsolationofPhytosterolsfromCerealBy-Products 57219.3.5 ProductionofOrganicAcidsfromCereal

By-ProductsandBakeryWastes 57319.3.6 ProductionofDietaryFiberfromCereal

By-Products 57419.3.7 ProductionofProteinsandEnzymesfrom

CerealBy-Products 57519.3.8 Biofuel 57619.3.9 Miscellaneous 577

19.4 SocioeconomicAspectsoftheIdentifiedValue-AddedProcesses 578

560 Valorization of food Processing By-Products

19.1 Introduction

Currently,thereisawarenessaboutglobalpollutiontogetherwithrisingproductioncostsandsometimesdecreasingavailabilityofrawmateri-als,leadingtoanemphasisontheimportanceofrecovery,recycling,andupgradingoffoodprocessingwastes.AccordingtotheEuropeanLandfillDirective,theamountofbiodegradablewastesenttolandfillsinmembercountriesby2020mustreach35%ofthelevelsof1995.TheEuropean food processing industry operations are forced to complywithincreasinglymorestringentEUenvironmentalregulationsrelatedtodisposalorutilizationofby-productsandthelargevolumesofaque-ouswastesgenerated(Kosseva2009).Thesewastesrepresentconsider-ableamountsofpotentiallyreusablematerialsandenergyinspiteofthe fact that theypose serious environmental and economical chal-lenges.Mostofthematerialsgeneratedaswastesbythefoodprocess-ingindustriescontaincomponentsthatcouldbeutilizedassubstratesandnutrientsinavarietyofbiotechnologicalandchemicalprocessesandcouldyieldvalue-addedproducts.Consequently,revalorizationofby-productsorwastehasbecomeapriority/necessityinrecenttimes.

Cerealgrainsarethemostimportantcropthatprovidesmorefoodandenergytothehumanracethananyothercrop(FAOSTAT2010).Amongthecerealgrains,wheataccountsforaround29%ofthetotalcerealproduction,andisconsideredasthemostpopularcerealsince72% of the total production is destined for human consumption.Wheatisusuallygroundtoflourandusedtoproduceawiderangeofbakeriesandconfectioneryproducts.Thebakeryindustryisoneoftheworld’smajorfoodindustriesandvarieswidelyintermsofproductionscaleandprocess.Traditionally,bakeryproductsmaybecategorizedasbreadandbreadrollproducts,pastryproducts(e.g.,piesandpas-ties),andspecialtyproducts(e.g.,cake,biscuits,donuts,andspecialtybreads).Themajorequipmentsusedinprocessingincludethemiller,mixer/kneading machine, bun and bread former, fermenter, bakeovens, cold stage, andboilers.Themainprocesses employed in the

19.5 EnvironmentalConcernsandRegulatoryConsiderations 58019.6 SpecificCaseStudy:ValorizationofSpecificBy-Product 58119.7 FutureTrends,Bottlenecks,andResearchGaps 583References 584

561Bakeries and confectioneries

productionofbakeryproductsincludemilling,mixing,fermentation,baking,andstorage.Thegeneralproductionprocessflowchartofthebakery industry (Chenet al.2006) indicates thatalmosteveryunitoperationgeneratesorganicwastes andwastewater.Theproductionprocessesalsocontributetonoisepollutionandairpollutioninaddi-tiontothesolidwastesandwastewater.

Inthischapter,anin-depthupdate/stateoftheartoftherevalori-zationofby-productsandwastesfrombakeriesandconfectioneriesisprovided.Adetaileddescriptionofby-productsandwastesgeneratedduringprocessingoffoodinbakeriesandconfectioneriesisenvisagedfromthequalitativeandquantitativepointsofview.Thepotentialoftheby-productsfrombakeriesandconfectioneriesfortheproductionof biologicals of commercial significance is identified and discussedwithspecialreferenceto ingredients,enzymes,phytochemicals,bio-fuel,andbiomaterials.Somechallengesandopportunitiesofcurrentwasteprocessingtechniquesaredetailed(description,monitoring,andauditing)anddiscussedintermsoftechnologicalsuitability,socioeco-nomicimpact,environmentalconcerns,andregulatoryconsiderations.The practical implementation represented by one application on thevalorizationofaspecificby-productisincludedasacasestudy.Futuretrends,bottlenecks,andresearchgapsareretrievedanddiscussed.

19.2 By-Products and Wastes Generated during Processing of Food Products in Bakeries and Confectioneries: Qualitative and Quantitative Aspects

By-products and wastes from the cereal industries, namely, wheatprocessingindustries,consistofawiderangeofitemswhichcanbeclassifiedintothreemajorgroupsthatcorrespondtothestagesofpro-ductionandutilizationsystems(FallowsandWheelock1982):

• Onthefarm,wherethemajorwasteisthestraw.• Duringprimaryprocessingormilling.• Duringsecondaryprocessing.Thisgroupisdominatedbythe

by-productsgeneratedinthebreadbakingindustry.• Duringthedistributionofcereal-basedproducts.Aconsid-

erableamountofwaste isgeneratedat this leveldue to theperishabilityofthebakedproducts.


Theby-productthatisgeneratedonthefarmisthestraw,whichisgenerallyusedformakingbedsforanimalsorstorageofothercrops,andbulkfeedingofruminants.Otherusesofstrawincludeitsutiliza-tionasbuildingmaterial,inpapermaking,asafuel,orasarawmate-rialforthechemicalindustry,namelyintheproductionoffurfural.Althoughthemosteconomicalmethodofdisposalofstrawpracticeduntilnowisburning,thispracticeisnotdesirablesinceitcausesenvi-ronmentalpollutionandthereisariskoffirespreading.Recently,athorough revisionof the treatmentmethods (incineration, combus-tion,composting)thathavebeenappliedtowheatstrawtoconvertitintousefulmaterialssuchasbiomass,biogas/biofuel,animalfeeding,andcompostingwasreported(ArvanitoyannisandTserkezou2008).Infact,thereisgreatpotentialforconversionofwheatstrawintobio-mass or biogas in view of the economic and environmental issues.Nevertheless, considerable effort has been put into developing newwheatvarietieswithshorterstrawlength(for increasingtheirresis-tanceto lodging-bendingundertheweightofrainorgrain),whichallowstoincreasethegrainyieldwithoutincreasingthestrawyield.

Theprimaryprocessingofwheat,milling,resultsintheproductionoflargequantitiesofby-productsthatincludebranandgerm.Thepri-maryproductofthisindustryisthewheatflourderivedfromthestarchyendosperm.Generally,28%ofthegrainisremovedduringtheproduc-tionofwhiteflourwhichisrelativelyrichinfibers,vitamins,minerals,andalsofatandproteinthatcomefromthegerm.Itwasestimatedin2007that434millionmetrictonsofwheatwasgroundtoflourandtheprocessgeneratedover121millionmetrictonsofbran(FAOSTAT2010).Themillingby-productsareprimarilyusedasanimalfeedstuffs,althoughalternativessuchastheextractionofdietaryfiberandproteinfromthebranortheproteinfromthegermforinclusioninthehumanfoodsupplyhavebeenproposed.

The secondary processing of cereals refers to bakeries and con-fectioneriesprocessing.Alargevarietyofbakedgoodsareproducedinbakeriesandconfectioneryindustries,althoughbreadisthemostpopularproduct.Bread ismassivelydowngraded fromhigh-qualityfood to feedorwaste. Surplus bread in retail, if not devaluated bydown-pricing at the end of shelf life, will end up as animal feed.Also, theoverages,productionerrors, andout-of-specbread in thebakeriesaredowngradedtoanimalfeed.Itisestimatedthat10–25%


ofhigh-valuestaplefoodisthusdegradedtofeedorworse.Atbest,bakeriesorretailersmaygetasmallfeewhentheyareabletosellitasanimalfeed,andintheworstcase,theyhavetopayfordumpingit.Inadditiontotheby-productsgeneratedduringthesecondaryprocess-ing, bakeries and confectioneries also generate enormous wastewa-ter,whichismixedwithmajorrawmaterialssuchasflour,fat,sugar,ormilk, through severalunitoperations suchasmachinecleaning,utensilcleaning,washing,spillages,dusting,andsoon.

Further, a large quantity of by-products is also generated afterdistributionofbakedgoodsduetotheirveryshortshelflife.Theprod-uctsthatcanberecycledincludebread,dough,pasta,crackers,cerealbagels, sweetgoods,andsnackchips.Themajorwastegeneratorofthissectoristhefactory-bakedslicedloaves.Ithasbeenestimatedthat2%ofthebreadproductioniswasted,althoughsomeothersreportedthattheamountoflosscouldbeabout5%.Largebakeryandsnacksfoodmanufacturersproducelargevolumesofgoods.Althoughthesemanufacturingunitsgeneratesmallpercentagesofrejectedproduct,theyamounttohundredsoftonsofinedibleproductperweek.

Thefirststepforrecyclingofwastesmustbetheidentificationofthewasteorby-productsandtheirfurthercharacterization.Knowledgeof their chemical composition, particle size, and physicochemicalpropertieswillfacilitateoptimalrecycling,aswellasthebesidesiden-tificationofappropriateapplications.

19.3 Potential of the By-Products from Bakeries and Confectioneries for Prospective Production of Biological of Commercial Significance

Numerous valuable substances formed during food production aresuitable for separation and recycling at the end of their life cycle,even thoughpresent-day separationand recyclingprocessesarenotabsolutely cost efficient. Transformation of by-products and wastesfrommilling,bakeries,andconfectioneryindustriesintovalue-addedbiological products of commercial significance (enzymes, pigments,flavors, functional ingredients,micronutrients,nutraceuticals,activepharmaceuticalingredients,phytochemicals,biofuel,andbiomateri-als)canbeachievedbyusingtheby-productseitherasrawmaterialfor secondaryprocessesoras animal feed, asoperating supplies,oras ingredients of novel/innovative products. The waste processing


techniques used to convert the residues into commercial productsshouldmeetthecleanproductionrequirementsconsideredsofarasastrategicelementinmanufacturingtechnologyforcurrentandfutureproductsinseveralindustries.Thewastemanagementhierarchyisoneoftheguidingprinciplesofthezerowastepractice(Kosseva2009).Byanalogywiththisprinciple,thedevelopmentofgreenproductionpro-cessescanbeachievedfollowingtheshort-,medium-,andlong-termgoals(Laufenberget al.2003).Demandis focusedonthedevelop-mentofcost-effective technology,optimizationofprocesses includ-ingseparationsteps,alternativeprocessesforthereductionofwastes,optimizationoftheuseofresources,andimprovementinproductionefficiency(Laufenberget al.2003).

19.3.1 Use of Cereal By-Products as Animal Feed

Many by-products have substantial potential value as animalfeedstuffs.Wastecerealproductshavebeenarichsourceofnutri-tious and cost-effective animal feed. Wastes from bakeries andconfectioneries include damaged and returned bread, baked andunbakedwastedough,slicercrumbs,andsoonthatarepasttheirexpiration date. The bread lost from human consumption is usu-allydowngradedtoanimalfeeduse.Allthoseproductsareconsid-eredtobehighlyenergeticduetotheirhighcarbohydratecontent(Arosemenaet al.1995).Hence,itisfrequentlysuggestedthatthename“driedbakerywaste”shouldbeprecededbythesourceofthewaste.Thiswasteisconsideredpalatableandrichincarbohydrates,althoughitsproteinandvitamincontentsarelowandgreatlyvarybetweenproducts(Table19.1).Variabilityinapproximatecompo-sition of wastes is considered a major hurdle for the feed manu-facturing industries,which require rawmaterialswitha constantcompositionandregularsupply.

Toassessthepossibleuseofthebakerywasteasfeed,analyticaldata on the nutritive value of residue are necessary in addition toanimal trials that are indispensable to assess feedstuff palatability,animalefficiency,andpotentialhazards(BoucquéandFiems1988).Earlyin1965,itwasnotedthatinclusionofdriedbakeryproductsinthebroilerdietdidnothaveanyadverseeffectontheirperformance(Damron et al. 1965). From that time on, different studies have


corroboratedtheuseofdriedbakerywastesforpartialreplacementof cereals in the animal fattening diet. In fact, bakery waste hasbeenusedtoreplaceupto30%ofthecorninthedietofbeefcattle(Passini et al. 2001). Replacement of corn with bakery waste didnot result inamodificationof thequalityof themeat,confirmingthe use of bakery waste as a source for feeding cattle. The inclu-sionofbakerywasteupto25%inthefatteningdietsoflambsdoesnotaffect theperformanceof the lambsandevenan improvementwasobservedinthequalityofthetailfatandinternalfatprobablyduetotheincreaseinfattyacidsynthesisbyrumenmicroorganismsinduced by the higher soluble sugars present in the bakery waste(Afzalzadehet al.2007).Astudyconductedtoevaluatetheeffectsoffeedingaerobicallyprocessedandvacuum-dried foodwaste-broilerlitterandbakeryby-productmixturestofinishingpigsindicatedthatacorn–soydietcouldbereplacedwithafoodwastemixtureupto50%withoutcausinganysignificanteffectonpigproduction,carcasscharacteristics,meatquality,andtastepaneltestwiththeexceptionof reduced feed efficiency and lower meat color score (paler color)(KwakandKang2006).Nevertheless,itshouldbeemphasizedthattheextentofbakerywasteuseasafeedingredientdependsonthecostsoftheconventionalfeedstuffs,thesafetyofanimalhealth,andtheattractivenessofalternativeusesforthatwaste.

Table 19.1 Proximate Composition of Dried Bakery By-Products Reported by Different Authors

NUTRIENTAL-TULAIHAN ET AL. (2004)

DALE ET AL. (1990)

SALEH ET AL. (1996)

PASSINI ET AL. (2001)

KWAK ET AL. (2006)

Moisture (%) 8.43 10.2 8.11 6.86 11.00Crude protein (%) 12.22 10.6 12.53 8.75 8.46Ether extract (%) 1.32 11.1 11.04 15.94 8.28Crude fiber (%) 0.108 2.5 2.25 0.00 1.16Ash (%) 1.38 4.8 4.48 1.78 1.78Calcium (%) 0.18 — 0.28 0.07 —Phosphorus (%) 0.15 — 0.52 0.16 —Sodium (%) 3.2 — 0.93 — —Potassium (%) 0.45 — — — —Magnesium (%) 0.08 — — — —Chloride (%) 0.12 — 1.37 — —Energy (kcal/kg) 3895 3630 3670 — —


19.3.1.1 Separation of Bakery Products Package materials in packedbakery foods pose a major difficulty during the separation of thecereal fromitspackaging.Shreddingorcrushing isnotanefficientsolutionduetothecontaminationoftherecoveredcerealwithpack-agingmaterials.Theresultingproductrequiresfurthersiftingbeforebeing subjected to subsequent production processes. An alternativestepwastoemptythepackagingbyhand,whichisslow,costly,andhaspotentialhealthandsafetyimplications.Amethodforprocessingunsorted,partlypackagedbakeryproductsdeliveredwithaddedfor-eignbodiesincludescomminutingthedeliveredstalebakeryproductswithoutanyprecedingsorting,andthensievingthebakeryproducts(Bscheider1990).Themajorityofthepackagingmaterialisremovedbysuctionduringsievingandthenthesievedfractionisdriedbyheat-ing.Anyresiduesofaluminumfoilpackagescanberemoved,aftercooling the bakery product granules, by squashing and subsequentsieving. The process can be completely automated in a plant thatcontainsacomminuter,asievingmachinewithasuctionapparatusattached, and at least onedrier.With thisprocess, it is possible toobtain high-grade bakery product granules. Some companies havedesigned specificmachinery to separate awide rangeof packagingmaterialsfromitscontentswithupto99%efficiency.Theseparationisdoneusingcentrifugalforce,airflow,andmechanicalactionthatcauseminimaldamagetothepackagingandgeneratehigherairflow,whichincreasesseparationefficiency.

19.3.1.2 Processing of Bakery Waste for Feed Preparation Bakery wastemustbeprocessedinordertoconvertbreadcrumbs,disposedofasanindustrialwaste,intoafeedthatismerchandizedtohavehighaddedvaluebesidesyieldinga satisfactoryproduct for feeding. Initially, itisnecessarytocrushanddrythewastebreadintofinepowderandgranularmaterialwithlowmoisturecontentsothatitcouldbeusedasamixedfeedforlivestock.Therefore,allthoseproductsaresubjectedtodrying,cleaning,mixing,andmilling.Yoshihiroet al.(2006)pro-posedthefollowingprocess: thebakerywaste is fed intoaprimarydryingpassagecontainingrotarycrushingvanesandahotairinjec-tionnozzle; thewatercontent inthewastebreadisevaporatedandremovedbytheheatedprimarydryingpassageandhotairfromtheinjectionnozzle;andthenthewastebreadissuppliedintoasecondary


dryingpassagewhilecrushingmorefinelybyarotarycutter.Aglu-tenformulafeedcanalsobeobtainedbymixingbreadcrumbasanessentialcomponentwithwaterasaformulatingagentandanutri-tive-assistantagent(Minoru2004).Thismixtureisfedintoascrewextruderandsubjectedtoheatingfollowedbymixingandkneadingat40–140°C.Thus,aninexpensivepellet-likeglutenformulafeedisobtainedhavingexcellentdigestionabsorbabilityandshape-holdingproperties.Theformulafeedcanbeusedasafeedforcultivablefishes,pets,andsoonbyregulatingthenutritionalcomponent.

Anaerobicfermentationhasbeenappliedtobakeryby-productsandwheatbranamongotherfoodwastesforimprovingthephysicochemi-calcharacteristicsofthefeedusinglacticacidbacteria(Lactobacillus salivarius).Bakerywasteandwheatbranwereinoculatedwithlacticacidatlevelsof0.1%,0.2%,0.5%,and1.0%andfermentedanaerobi-callyatroomtemperature(25°C)for10–30days(Yanget al.2006).Thestorageundernonanaerobicconditionsledtomicrobialputrefac-tionwithaconcomitantlossofwaterandwater-solublecarbohydrateandincreasesinproteinandfiber.Anaerobicfermentationwiththelactic acidbacteria led to an increase in thewater-soluble carbohy-dratesalongwitha simultaneousfiberdecrease,andcontributed totheoverallnutritionalimprovement.Short-termstorage(10days)waspreferredbecausenoadditionalchangesinthechemicalcomponentswereobtainedwithlong-termstorage,whichalsoinducedasignifi-cantreductioninthenumberoftotalandlacticacidbacteria.Onthebasisoftheseresults,0.2%inoculumwasconsideredastheoptimumlevelforimprovingnutritionalpropertiesofthebakerywasteandbranusinglacticacidbacteria(Yanget al.2006).

One problem that assumes significance in recent times is theincreasinglevelofdioxininthefeed.SeveralincidentsinEuropewith dioxins were reported, starting with contaminated feedand resulting in contaminated food for human consumption. In2003,arapidalertwasissuedbytheEuropeanUnion,reportingthe presence of elevated dioxin levels (3.3–13.3ng TEQ/kg) indriedGermanbakerywastewhichwasusedinanimalfeed.PartofthatbakerywastewasusedbyaDutchcompanyforthe produc-tion of different types of feed. In that reported case, the sourceofthedioxinswasfoundtobethewastewoodusedforthedry-ingof thebakerywaste (Hoogenboomet al.2004).Further, the


waste is sometimes blended with different oils, and the use ofnon-feed-gradeoils in theproductionof feed could alsobeheldresponsiblefordioxinlevels.Otherwise,theuseoftoohighdry-ingtemperaturescouldalsoleadtoanincreaseinthedioxinlevels(Independent2008).

19.3.1.3 Commercial Products for Feeding Obtained from Bakery Waste Bak-eryby-productsaresometimesmarketedasindividualfeedingredi-ents, or as a mixture of two or more feedstuffs. In fact, there is amaize–glutenfeedwhichisamixtureofsteepwater,bran,gluten,andgermmeal.Inaddition,high-energyingredientscanbeobtainedforfeeding.AnexampleistheoneregisteredasCookieMeal®(http://www.bakeryfeeds.com) that nutritionally increases the quality ofthe feedingpelletsbyprovidingproteins, fats,fibers,minerals, andvitamins.

19.3.2 Production of Sourdough from Bakery By-Products

Theuseofwastebreadintheproductionoffreshbreadwithdesirablebakeryeffectswaswellunderstoodeveninthe1950s.Currently,theadditionofwastebreadtothebreaddoughinthepreparationoffreshbreadinvolvesgrindingcertainproportionsofwastebread.Althoughwastebreadisavaluablenutrient,onlyaverysmallproportioncanbereusedowingtothegeneralattitudeinthetrade.Moreover,insomecountries,regulationsallowonlyamaximumof3%ofstalebreadtobeaddedwhenprocessingfreshbread.Nevertheless,theuseofstaleor surplus bread for the sourdough processing has become a moreacceptedalternative.The resultingproductobtainedbyabacterio-logicalfermentationprocessisacompletelynewsubstancethatcanbeusedforthepreparationofbreadandbakeryproducts.Inastudyconductedusingbacteriathatformhomofermentingand/orhetero-fermenting lactic and acetic acid, for example, Lactobacillus brevisandLactobacillus fermenti, fermentingdoughwasmade fromwastebread, suchaspiecescutoffcrispbread(Wilhelm1986).Theacidvalueofthatdoughvariedfromabout20to30,suchthatitcanbeusedtoreplacetraditional,natural,orcrystallinedoughacidifyingagentscompletelyorpartially.Thatfermentingdoughwasobservedto be particularly suitable for improving the baking properties of

http://www.bakeryfeeds.com

http://www.bakeryfeeds.com


pentosansinwholemealandrefinedflour,andthebreadbakedwithithadexcellentimprovementsinflavor.

AdifferentrecyclingprocesswasproposedbyFelch(2000),whichuses stalebreadand/orcakesas thestarter forproducingyeastandsourdough.Thestalebreadand/orcakeisthenhydrolyzedbyeitherusing enzymes or acidic hydrolysis, and subjected to purification ifrequired.Followinghydrolysis,theliquidsyrupfractionisseparatedandmixedwithwaterunderaerobicconditionswithsteepingyeast,andisconvertedintoyeastbiomass.Inasecondseparationstage,theyeastisdrawnoff.Thehydrolyzedfractionseparatedfromthesyrupinthefirststageismixedwithmilledryeproductsandwater,andisthenconvertedintosourdoughusingasourdoughstartercultureand/orprocessfluid,preferablywithlacticacidbacteria.

Bakedgoods,andespeciallybreadsbasedonmilledwheatorryeproducts,canalsobesubjectedtosequentialprocessingforobtaininganassortmentofproductsthatcanbeusedbackinthebread-makingpro-cess.Forrecyclingbakeryproducts,Meuser(1998)andhiscolleagues(MeuserandMartens2009)proposedthefollowingsteps:(a) prepara-tionofthestartingmaterial;(b)preparationofafermentationsubstratebyenzymatichydrolysisof the startingmaterial; (c) fermentationofthehydrolysatewithacid-formingbacteria(Lactobacilli delbrükii),andfinallyperformingoneof the following steps: (i) recoveryofbaker’syeast,(ii)recoveryofanacidliquor,(iii)recoveryofballastsubstances,(iv) recoveryof ethanol, and (v) recoveryofCO2.Theendproductsof thisprocess are recovered separately, andused formakingbakedgoods.Thisprocessindicatespotentialscopeforthebreadfactoriestousethereturnedandremainderbreadeconomicallywithintheframeofaholisticconceptofthepreparationandmarketing.

The recycling of stale or surplus bread has acquired such impor-tancethatevencommercialproductsareavailableforupgradingthiswaste.Astarter launchedasSonextraSustain(Sonneveld2010)canefficientlygeneratesourdoughfromstaleorsurplusbread,complyingwiththeholisticconceptoftheproduction.Thisstarter,3.8%onstalebreadbasis,generatedasourdoughthatcouldbeaddedtothenormalbreadrecipewhichultimatelydeliversextrataste,flavor,andsoftness(upto20%softerafter3days),withoutdeteriorationinthebreadqual-ity, such as crumb structure and volume. Among other claims, thesupplyingcompanyindicatedthatthepHloweringduringsourdough


fermentationisfastenoughtopreventropeformationbyBacillus sub-tilis andBacillus cereus,butwithoutdeliveringacid taste to thefinalbreadwhenaddedupto20%onflourbasisinthefinalbreadrecipe.Optimumfermentationperiodsarealsodecreasedbyafactorof3–4(from36–48hto12h),enablingthebakerytoprocesstheleftoverandwastebreadwithin24h.

19.3.3 Production of Sugars or Polysaccharides

Wheatbranfrommillsandbakerywastesuchasbrokenpiecesandcrumbsofbakedgoodsareanadequatefeedstockfortheproductionof chemicalsdue toahighyieldof almost80gglucose/100g sub-strate.Wheatbran constitutes a significantunderutilized sourceofsugarsandhenceitisconsideredasasourceforobtainingsugarsordifferentpolysaccharides.

Industrial wheat bran is composed of the outer coverings of thegrain,thealeuronelayer,andtheremnantsofthestarchyendosperm.Itconsistsmainlyofstarch,arabinoxylans,cellulose,β-glucans,pro-tein, and lignin. Therefore, recovery of the maximum amount ofsugars from hemicellulose, cellulose, and glucan necessitates appli-cationofdifferenttreatments.Enzymaticliquefactionwiththermo-stableα-amylasefollowedbysaccharificationwithamyloglucosidasereleasedbetween20and34gglucan/100gwheatbran,dependingontheextractionrateduringmilling(Palmarola-Adradoset al.2005).Afterfiltration,thesolidmaterialmustbehydrolyzedforrecoveringthesugarsfromthecelluloseandhemicellulose.Palmarola-Adradoset al.(2005)comparedtheefficiencyofdifferenthydrolysismethods(acidhydrolysiswith1%sulfuricacid,enzymatichydrolysis,thermalpretreatment followed by enzymatic hydrolysis, thermal pretreat-mentunderdiluteacidconditionsfollowedbyenzymatichydrolysis)for sugar production and observed that arabinose, xylose, and glu-cose were released from all the treatments although yield of sugarwas significantly affected by the treatment conditions. The highestyield(53gtotalsugarper100gstarch-freebran,whichwasequiva-lentto31gtotalsugarper100gwheatbran)wasobtainedwiththethermalpretreatmentunderdiluteacidconditionsfollowedbyenzy-matichydrolysis.Thistreatmentreleasedarabinose:xylose:glucoseintheproportion2.5:4.3:3.1.Acidhydrolysisalsosupportedveryhigh


yieldbutreleasedmostlypentosans(arabinoseandxylose).Itmustberemarkedthatitisdesirabletoincreasetheyieldofglucose,ifeffectiveutilizationofbranaslow-costfeedstockfortheethanolproductionispreferred,sincecurrently,therearenopentose-fermentingorganismsusedincommercialethanolproduction.

Bakery waste contains mainly starch and minimal amounts ofhemicellulosesandcelluloses.ChoiandMathews(1996)proposedatwo-stepacidhydrolysisofbakerywastewhichyielded92%conver-sionintoglucosewithnoxyloseinthehydrolysate.Duringthefirststep,driedbakerywaste,aftergrindingandsieving,washydrolyzedwith2%(w/w)sulfuricacidat132°Cfollowedbyanotherhydrolysiswith 15% (w/w) sulfuric acid at the same temperature. Alternativesteps include recovery of fats, sugars, proteins, and starch that arepresentinthebakerywaste(MullerandGrob1977).Theindividualrecovery of thewaste bakery componentshas thepotential topro-vide value-added foodproducts.Muller andGrob (1977)proposedasystemforsequentialisolationofindividualcomponentsofbakerywaste.Firstasolventextraction–filtrationstepisperformedtoremovefatandoilcomponents,followedbysugarrecoverywithanalcoholicsolution. The filter residue could be subjected to acid or enzymatichydrolysisfollowedbyanaerobicfermentation.Thepurification,con-centration,anddryingoftheproductallowsrecoveryofcrudeproteinforreuseinfoodproducts.

Otherwise, thebakerywaste couldbehydrolyzed toconvert thestarch into glucose or other fermentable sugars, and recovered byultrafiltration (Muller 1977). The resulting glucose-containing liq-uidcouldbeusedfortheproductionofdesiredyeastorbacteria.Theprotein-containingsolidsthatremainaftertheultrafiltrationstepareavaluablesourceofproteinsthatmaybeusedfortheproductionofanimalfeedorinhumannutrition.

Pullulanisanextracellular,linear,unbranched,andwater-solublemicrobial polysaccharide consisting of α-(1–6)-linked maltotrioseunits that are increasingly utilized for its filming properties. Thispolysaccharide is used in food, cosmetics, pharmaceutical, agri-cultural,andchemical industries (Deshpandeet al.1992).Bakerywaste has been proposed as an alternative substrate for economicproduction of pullulan (Thirumavalavan et al. 2008), and acid-hydrolyzed bakery waste was used, after neutralization, as a sole


sourceofcarbonbyAureobasidium pullulansforthebatchproductionofpullulan.

19.3.4 Isolation of Phytosterols from Cereal By-Products

Thelipidextractsofcertaincerealby-productsmayberichsourcesofhealth-promoting compounds such asphytosterols.Thus, sitosterol,campesterol, brassicasterol, and stigmasterol were isolated as themajorphytosterolsfromthelipidextractsobtainedfromwheatgermand bran (Jiang and Wang 2005).Wheat germoil has a universalhealth-improvingactionincludingnormalizationofthefunctionsoftheimmuneandtheendocrinesystem.Itstimulatesthereproductivefunction,increasesworkingabilityandlifetonus,andstrengthensthestresstolerance.Inaddition,itcontributestofasthealingofwounds,burns, ulcer, and diseases of the gastrointestinal tract. It possessesantiatherosclerotic andheart-protecting properties, and reduces thelevelofcholesterolinthebloodandtheliver.Hence,theworld’slead-ingcompaniesinthecosmeticindustryusewheatgermoilforpro-ducingcreams,lotions,cosmeticmasks,balms,shampoos,andsoon.

Wheat fractions are rich in a number of phytosterols, but thepotential of fractions such as bran, germ, and straw has not beenexploitedtoitsfullextent.Germextractshadthehighesttotalphy-tosterolcontentfollowedbystrawandbranextracts(Dunfordet al.2009).Phytosterolextractionfromwheatgerm,bran,andstrawcanbecarriedoutbyapressurizedsolventextractionsystem,butthesol-venttypeandthetemperaturesignificantlyaffectthephytosterolcon-tentandcompositionof theextractscollected fromwheat fractions(Dunfordet al.2009).Whenpetroleumether,chloroform,n-hexane,andethanolwereusedassolvents,ethanolextractionresultedinthelowesttotalphytosterolrecoveryfromgerm,whereasβ-sitosterolwasthemostabundantphytosterolinstrawhexaneextracts.

Recently, Tikhonov (2010) proposed a process to obtain an oilconcentrate from wheat germ, in which wheat germs were previ-ouslydriedtoamoisturecontentof6–8%andthensubjectedtocoldpressing.Theoilobtainedwasextractedtwicewith92–93vol.%ethylalcoholataratioof1:3and1:2,respectively.Thealcoholicextractswerecombined,maintained,andafterseparationofthephaseswereevaporatedundervacuumatatemperatureof50–60°C.Thismethod


allowedobtainingoilenrichedwithphytosterols,anddifferentformsof tocopherols and carotenoids, which increase the nutritional andhealingpropertiesthereof.Thisoilconcentratehasthepotentialforuse as an additive in the preparation of medicinal compounds andprophylacticagentssuitableforrestoringdisordersinsexualfunctions.

19.3.5 Production of Organic Acids from Cereal By-Products and Bakery Wastes

Reclamationofthesolidandhigh-energycerealby-products(bran,streams)andbakerywastes(stalebread,breadrolls,andcookies)hassignificantimpactoneffectivemanagementofwastes.Besidestheirprimaryapplicationasanimalfeed,thewasteshavepotentialforpro-ductionofvaluableproductssuchasorganicacidswithagoodcon-versionefficiency.Theoptimizationoftheproductionoflacticacid,fromdiscardedbread crust, by an amylolytic lactic acidbacterium,Lactobacillus amylovorus, and the application of the culture filtrateobtainedfromthelacticacidfermentationinthebread-makingpro-cessasaneconomicalmethodofrecyclingbakerywasteshavebeenreported (Oda et al. 1997). Addition of 2.0% yeast extract in themediumcontaining3.58%breadcrustledtomaximumacidproduc-tion.Inthemediumsupplementedwith2.0%cornsteepliquorand2.0%defattedsoybeanpowder,47.2%oftotalsugarswasconvertedintodl-lacticacid in72hunder static incubation.Thebreadmadewiththeadditionoftheculturefiltratewaspreferredoverthosewithand without the addition of commercial fermented seasoning withrespecttotasteandoverallacceptability.

Anovelgenericfeedstockproductionstrategybasedonsolid-statefermentation(SSF)hasbeendevelopedandappliedtothefermenta-tiveproductionofsuccinicacid(Duet al.2008).Wheatwasfraction-ated into bran, gluten, and gluten-free flour by milling and glutenextractionprocesses.Theresultingsolutionswereseparatelyutilizedforthehydrolysisofgluten-freeflourandglutentogenerateaglucose-rich stream of over 140g/L glucose and a nitrogen-rich stream ofmorethan3.5g/Lfreeaminonitrogen.Amicrobialfeedstockconsist-ingofthesetwostreamscontainedalltheessentialnutrientsrequiredfor succinicacid fermentationsusingActinobacillus succinogenes. Inafermentation using only the combined hydrolysate streams, around


22g/Lsuccinicacidwasproduced.TheadditionofMgCO3intothewheat-derivedmediumimprovedthesuccinicacidproductionfurthertomorethan64g/L.Increasingtheinoculumconcentrationto20%didresultintheproductionof62.1g/Lsuccinicacid(Doradoet al.2009).ResultsindicatedthatA. succinogenescellswereabletoutilizeglucoseandmaltoseinthewheathydrolysateforcellgrowthandsuc-cinicacidproduction.TheseresultsdemonstratedthattheSSF-basedstrategyisasuccessfulapproachfortheproductionofagenericfeed-stockfromwheat,andthatthisfeedstockcanbeefficientlyutilizedforsuccinicacidproduction.Theproposedprocesscouldbepotentiallyintegrated into a wheat-milling process to upgrade the wheat flourmillingby-products (WFMB) into succinic acid,oneof the futureplatformchemicalsofasustainablechemicalindustry.

19.3.6 Production of Dietary Fiber from Cereal By-Products

Cereal milling by-products, mainly bran and husk/hull, are tradi-tionalsourcesfordietaryfiberisolationandpurification.Nowadays,there is a trend to seek new sources of dietary fiber, such as agro-nomicby-products(fruits,vegetables, leguminous,plants)thathavetraditionallybeenundervalued(Rodríguezet al.2006).Today,theyareconsideredasapromisingsourceoffunctionalcompounds.Cellwallmaterialscontainbetween60%and90%dietaryfiber,whereasthebranfractionsofsomewhole-graincereals,suchasoats,wheat,andrice,contain16–32%,35–45%,and20–33%totaldietaryfiber,respectively. This is hinderedby the fact that the yieldof cellwallmaterial from fruit and vegetables on a fresh weight basis is verylow (1–4%) (Redgwell and Fischer 2005). Grigelmo-Miguel andMartín-Belloso (1999)have compared the characteristicsofdietaryfiberfromby-productsofprocessingfruitsandgreensandfromcere-als. The dietary fiber constituents and dietary fiber concentrates ofapple,pear,orange,peach,artichoke,andasparagusandofwheatandoatbranweremeasuredusinganenzymatic-gravimetricmethod.Inaddition,thewater-holdingcapacityofthedietaryfiberconcentratesand cereals was estimated by centrifugation. Dietary fiber concen-tratesoffruitsandgreensshowedahighcontentoftotaldietaryfiber(35–59g/100g),insolubledietaryfiber(21–44g/100g),andsolubledietary fiber (10–14g/100g). The soluble fraction was found to be


greaterindietaryfiberconcentratesinfruitsandgreensthaninwheatandoatbran (3–4g/100g).Measurementsofwater-holding capac-ityshowedthatdietaryfiberconcentratesoffruitsandgreenshadagreateraffinityforwaterthanthosefromcereals.

19.3.7 Production of Proteins and Enzymes from Cereal By-Products

Aprocessforthemicrobialbioconversionofcerealmillingby-prod-ucts into proteinaceous material for human consumption has beenpatented(Moo-Younget al.1990).Theby-productswereaerobicallyfermentedbythefungusNeurospora sitophilaatsuitabletemperature,pH,andnutrientconditionsoveraperiodsufficienttogrowmicro-bial biomass protein. The resulting microbial biomass product hadarelativelyhighcontentofprotein,dietaryfiber,ergosterol,naturalflavor compounds, andB vitamins.Thebiomass lacked animal fatand cholesterol. As animal feed, this product appears to be com-petitivewithsoymealandfishmeal.Asahumanfood,thisproductappearstobesuitableforspecialhealth-consciousgroupswhoseekvegetarian, high-fiber, and/or low-cholesterol diets. More recently,dosSantos et al. (2004) evaluatedwhetherSSF is thebest systemforproducingenzymes.Theyfoundthatthetechniqueisappropri-atefortheproductionofenzymesandotherthermolabileproducts,especiallywhenhigheryieldscanbeobtainedthaninsubmergedfer-mentation.UsingSSF,theproductionofglucoamylasesfromwheatbranhasbeenaccomplished (Pandey1991).Nowadays,gelatiniza-tioniscoupledwithliquefaction,whichispossiblebytheactionofthermostableamylases.Sodhiet al.(2005)determinedthatthepro-ductivityofthermostableamylasesfromBacillussp.wasaffectedbythenatureof thesolidsubstrate (wheatbran, ricebran,cornbran,andcombinationoftwobrans).Maximumenzymeproductionwasobtained on wheat bran supplemented with glycerol (1.0%, w/w),soybeanmeal (1.0%,w/w),l-proline (0.1%,w/w), vitaminBcom-plex (0.01%)andmoistenedwith tapwater containing1%Tween-40.Sangeethaet al.(2004)havestudiedtheproductionoffructosyltransferasebyAspergillus oryzaeemployingawidevarietyofagricul-turalby-productsas substrates.They found that,among them, thebest resultswereobtainedwhenricebran,wheatbran, corngerm,spentcoffee,andteawereusedsupplementedwithyeastextractand


complete synthetic media. Commercial pectinase preparations areproduced from fungal microorganisms mainly by Aspergillus nigerstrains.TheuseofSSFforpectinaseproductionhasbeenproposedusing different solid agricultural and agro-industrial residues assubstrates, such as wheat bran (Castilho et al. 1999, Singh et al.1999).ThebranwasalsousedtoproduceglucoamylaseandproteaseenzymesviaSSFusingAspergillus awamori andAspergillus oryzae,respectively.Feruloylesteraseandxylanaseactivitiesweredetectedin culture supernatants from Humicola grisea var. thermoidea andTalaromyces stipitatus grown on wheat bran. Maximum activitieswere detected from cultures of H. grisea grown at 150rpm, with9.1U/mL of xylanase activity on wheat bran. Maximum feruloylesteraseactivitywas0.33U/mL.Analysisofresidualcellwallmate-rialaftermicrobialgrowthshowedpreferentialsolubilizationofara-binoxylanandcellulose,twomainpolysaccharidespresentinwheatbran (Kosseva2009).Theproductionof low-cost cell-wall-decon-structingenzymesusingagro-industrialby-productscould lead totheproductionof low-cost enzymes for use in the valorizationoffoodprocessingwastes(Mandalariet al.2008).

19.3.8 Biofuel

Cerealsandvariousindustrialwasteproductsfromthebakeryindus-tryappeartobeamongthemostpromisingrawmaterialsforfuturesubstitutionoftheconventionalonesthatareusedinthepetrochem-ical and fermentation industry (Polman 1994). The bioconversionofcropsandresiduestofuelsandchemicals isreceivingincreasingattentionduetotheperceivedneedforthereductionofconsumption.Theterm“biofuel”referstoliquid,gas,andsolidfuelsproducedfrombiomass. Biofuels include bioethanol, biomethanol, vegetable oils,biodiesel,biogas,biosyntheticgas,biooil,biochar,Fishcher–Tropschliquids,andbiohydrogen(Demirbas2008).Bioconversionofwasteresidues(by-products)fromcerealprocessingindustriesrequiresbio-catalystsandenzymeswhichdegradexylanosicandcellulosicmate-rial. However, one of the major drawbacks of this process is thatthe yeast used for fermentation can utilize only hexose as sugars,whilemanymillingby-productsandbakerywastecontainsignificant


quantitiesofhemicelluloseandcelluloses thatyieldpentose sugarsuponhydrolysis.

Vidmantieneet al.(2006)describedamethodforhydrolyzingthepolysaccharides from cereal-derived waste to yield a sugar feedstocksuitableforfermentationintotechnicalethanolusingacomplexofamy-lolyticandhemicellulolytic/cellulolyticenzymes.Theenzymatictreat-mentofrawmaterialswascarriedoutbyliquidconcentratedamylaseandglucoamylase incombinationwithxylanase, containingcellulaseandglucanaseactivities.Apartfromethanol,methanol,propanol,buta-nol,isoamylandamylalcohols,acetaldehyde,ethylacetate,andmethylacetatewerefoundinthedistillate.Themaximumethanolconcentra-tionreachedafterfermentationofryeandwheatbranwas44g/L,andforryeandwheatgrainitwas73and69g/L,respectively.Anenzymepreparation from Humicola insolens, Ultraflo has also been suggestedforsolubilizingwheatbran.Thispreparationcontainedferuloylester-ases andglycosidehydrolases capableof solubilizingwheatbran,buttotalsolubilizationwasnotachievedeitherthroughsterichindranceorthroughthelackofcertainkeyactivities(Fauldset al.2006).

19.3.9 Miscellaneous

Someotherproductscanalsobeobtainedfromtherecyclingofcerealby-products.Delrueet al. (1998)describedanadditivecompositionfor enhancing the strength and/or stability of food products. Theadditivecompositioncomprisesacookedcerealby-product,inwhichtheedible starch isgelatinized toanextent,andcanbeaddedatalevelofatleast0.5%tomasa(corndoughwhichhasusuallybeennix-tamalized)orothercerealgrainflourordough.Anewfoodhasbeenalsoobtainedbyreusingbreadcrustandwastebread(overproducedbread)asrawmaterials(ShinjiandYoshikazu2003).Thosematerialsare gelatinized, melted, andkneadedwith aheated screw extruderat a water content of 8–75wt% and 30–180°C under a pressure of0–15MPaandextruded througha formingdieattached to the tipend of the cylinder barrel of the extruder. The processed food is adoughfoodoraprocessedfoodhavingplate,rod,granule,orfoamedshape. Recently, a multistep process was applied for the enzymatictreatment of the leftover bread to produce syrup which serves as a


substrateforfermentations(MeuserandMartens2010)(moredetailsinthecasestudysection).Bioabsorbents,paper,andsooncanbecitedamongthenonfoodusesofthecerealwaste.

Wheatbrancanbeusedasfillingmaterialintheproductionpro-cess of paper products. The incorporation of wheat bran up to 5%doesnotsignificantlyaffect thestrengthpropertiesof theresultingpapermaterials(ModzelewskaandAdamska2006).Theadditionofagreateramountofwheatbrancanleadtothedeteriorationofpaperpropertiesduetothereductioninthetensilestrength.

Biosorptionisanemergingprocessthatusesbiomaterialsformetalremovalandwasteremediation.Functionalgroupssuchascarboxyl,hydroxyl,sulfhydryl,andamidopresentinthewheatstrawandbrancanattachheavymetalionsfromwaters.Thebenefitsofusingthosematerialsasbioabsorbentsforremovalofmetalionsrelyontheirhighefficiency,highabsorptioncapacity,costeffectiveness,andrenewabil-ity(Farooqet al.2010).

Thebakeriesandconfectioneryindustriesgeneratealargeamountof waste water that is produced from general cleanup operations,which could contain grease, sugar, flour, filling ingredients, anddetergents.Thewastewatercanbetreatedbyphysicalmethodspass-ing through several storage tanks, chemical methods, or biologicalagents.Consideringthetypeofaeration,anaerobicmethodshavealsobeenproposed(Shinet al.1990),inwhichmethanegasisgeneratedthatcanbeusedforheatingpurpose.Abioremediationschemethatincluded pH adjustment and mixing aeration systems, an externalbiologicalreactorforproductionandperiodicinjectionoftheappro-priatebacteria,andabiologicalfilterwasrecommendedfortreatingoilandgreaseinbakerywastewater(KeenanandSabelnikov2000).

19.4 Socioeconomic Aspects of the Identified Value-Added Processes

Breadisthesinglelargestitemintheconsumers’wastebin.Ithasbeenestimated that inItaly theannualamountofbakerywaste isabout110,000–130,000metrictonsperyear,ofwhich70%isproducedinNorthernItaly(Cevolani2004).In2009,itwasreportedthatU.K.consumers’ waste bin holds/contains seven million slices of breadeveryday (Partos2009).U.K.bakeries correspond to782,000mT/yearofavoidablefoodwaste,whichcostsaround1.5millioneuros.


Since the twelfth century, bread in the United Kingdom has beenregulatedbyprescribedquantitiesandissoldin400or800gormul-tiplesof400gthereafter.However,theEuropeandirective2007/45/ECofferedsomefreedomtothebakersandretailers,allowingdif-ferentbreadsizes.ThesamereportindicatesthatthisECregulationcontributed,intheUnitedKingdom,toadecreaseintheamountofdailybreadwastebecausepeoplecanbuythebreadtheyuse.Thereisgreatpressureonthebakeryindustrytodesignsolutionstocom-bat waste, owing to their important contribution to the total foodwaste.Overthelastdecade,theEuropeanlegislativerequirementsforwastedisposalarebecomingincreasinglyrestrictive(ECRegulation1493/1999),andaccordingly there isapressingneed for theproperdisposalofwastematerial.Inaddition,owingtotheincreasingneces-sitytotakeintoconsiderationthevariousaspectsaimedatprevent-ing environmental pollution, promotion of economic motives, andneedtoconserveenergyandnewmaterials,severalnewmethodsandpoliciesforwastehandlingandtreatmenthavebeenintroducedintothe recovery, bioconversion, andutilizationof valuable constituentsfromfoodprocessingwastes.Besidestheirpollutionandhazardousaspects, milling, bakeries, and confectionery processing wastes dohaveapotentialforrecyclingrawmaterials,forconversionintousefulproductsofhighervalueasaby-product,asrawmaterials forotherindustries, and for their use as food or feed/fodder after biologicaltreatment,asithasbeenshownintheprecedingsections.

Different goals in product development and food production—highest product quality and safety, highest production efficiency,andminimizingthenegativeenvironmental impact—areintegratedintheholisticconceptoffoodproduction(Laufenberget al.2003).Therecyclingofresiduesisimportanttoeverymanufacturingbranchandhashighdevelopingpotential.Asystematicreductionofproductlossesandemissionsisprofitableunderbotheconomicalandecologi-calaspects,andspecialattentionisgiventotherecoveryofvaluablesubstances or product losses and internal process water recycling(Laufenberget al.2003).Theneedforsustainableproductionofprod-uctsusingrenewable,nonhazardousmaterialsandenergyefficiently,whileconservingbiodiversity,isfulfilledbythegreen/cleanproduc-tionprocesses.Cleanproductionsystemsarecircularandusefewermaterialsandlesswaterandenergy;asaresult,resourcesflowthrough


theproduction–consumptioncycleatslowerrates(Laufenberget al.2003).Significant environmental and economicbenefits can accruefrom separating industrial wastes with the objective of recycling/reusingthesevaluablecomponentsand/orthebulkofwater,byusingcleanproductionsystems.

19.5 Environmental Concerns and Regulatory Considerations

Differentstudieshavepointedouttheimportantcontributionofthecerealwastetotheglobalpollution.Aspecificexampleisincludedinthissectiontogivesomenumbersabouttheincidenceofthispollu-tion.Duringtheperiodbetween1980and1998,anaveragemassof8TgofcerealwastewasburnedannuallyinSpain,with1Tgofashremainingonthecerealfieldsaftercombustion(OrtizdeZárateet al.2005).Byusingemissionfactors,itwasdeducedthatpollutantemis-sionslinkedtothecerealwaste-burningprocessreachvaluesof11TgCO2,80GgofTPM,and23GgofNOxperyearduringthecereal-burningperiod.Theseemissionsrepresent46%ofthetotalCO2and23% NOx emitted in Spain during the burning period that lasts 1monthafterharvesting.Therefore, theproductionof1kgof cerealcropimpliesthat410gofcarbonand3.3gofnitrogenaregoingtobeintroducedintotheatmospherebythispollutantprocess.

Althoughrecycling isamajorconcern innumerous industries, itrequiresadditionaltechnologyandspecializedpersonnel.Generally,manufacturersdisposeof thewaste inovercrowded landfills,whichhaspromptedthecreationofspecializedcompaniesthatcollectandrecycle inedible bakery products. In addition, in response to morestringent regulations and rapidly escalating costs associated withwaste management, many industries have started to investigateand implement resource recovery systems for treating their residualstreams. The application of biotechnology across various industrysectorshasinvariablyledtobotheconomicandenvironmentalben-efits including less expensiveprocessing, enhancedproductquality,entirely new products, and environmentally sustainable processingrelative to conventional operations. Economic drivers are the mainfactorforincreasingacceptanceofbioprocessingandbioproducts,butsustainabilityconsiderationsareplayinganincreasingrole.Ineffect,theapplicationofbiotechnologyhascontributedtoanuncouplingof


economicgrowthfromadverseenvironmentalimpact.Industrialbio-technology ischangingthewayenergy,chemicals,andotherprod-ucts are produced. Through engineered biocatalysis, biotechnologyis enabling the use of previously unusable renewable materials andproductionofnovelproducts.Functionallyacceptableproducts thatare lesspollutingandpersistent thanconventional counterparts areemerging. All this is being achieved with reduced environmentalimpact and enhanced sustainability. Undoubtedly, biotechnology issettotransformindustrialproductiontoabasisthatismorecompat-iblewiththebiosphere(GavrilescuandChisti2005).

19.6 Specific Case Study: Valorization of Specific By-Product

Theimplementationofawastemanagement systemcouldappear,atfirstglance,tobetimeconsumingandcostly.However,inmostcases,goodenvironmentalpracticeleadstogoodbusiness.Aninterestingcasestudyisthevalorizationofstaleorsurplusbreadthatcanbeupgradedthroughsequentialenzymaticandfermentativeprocesses(MeuserandMartens2009).Leftoverbreadorbreadreturnshasbecomeaseriousenvironmentalandeconomicalproblemand,asishasbeenillustratedinprevioussections,theyhavebeenmainlyrecyclingtofeedstuff.MeuserandMartens (2009)showedtheeconomyof theprocessingofbreadreturnstoafeedstuffbydrying,indicatingthattheeconomicvalueofthe leftover bread is lower than that of thewheat for feeding, but acompleterecycleprocessattheplaceoforiginwouldbemorevaluable.

Meuser (1998) gave a specific example of a system for recyclingstalebread(Figure19.1).Stalebread(4000kgwetbasisor2400kgdrybread)ismixedwith2000Lofwaterinathermostatictank.Theadditionofα-amylase initiated the liquefactionprocessat70°Cfor3hatpH5.2,followedbysaccharificationwithamyloglucosidaseat60°C over a period of 16h. At least 80% of the initial starch washydrolyzed.Consideringthatoftheinitialbread1680kgarestarch,1493kgglucosewasobtained.Afterwards,proteinwashydrolyzedbyaproteasewithexoandendopeptidaseactivity,at45°C,pH5.2over21h.Duringthistime,70%oftheproteinwasconvertedintosolu-ble low–molecular-weightpeptidesandaminoacids.Then,proteasewasinactivatedbyheatingat100°Cfor30min.Adecantationstepwas included to separate the insoluble solids (mainly fibers),which


wasdepositedataflowof394kg/h.Thehydrolyzedsuspensionwasfermented with Lactobacillus delbrückii for 24h, during which thepHdecreasedto4.0.Therefore,approximately5%oftheglucosewasconverted into lactic acid and the remaining 1418kg glucose wassubjected to continuous aerobic and anaerobic fermentation in twodifferenttanks.Itisstatedthatintheaerobictanktheconcentrationofglucoseshouldbe20g/Landintheanaerobictank125g/L,whereastheyeastconcentrationinbothtanksshouldbeabout40g/L.Fromthedailyrhythm,initially,batchwisefermentationapproachresultedinaflowof250kgglucose/hforcontinuousfermentation.Basedontheglucosecontentinthefermentationsubstrate,themassflowratioof25:75wassharedbetweenthetwofermentationstages;thereforeand taking into account the losses occurred during decantation, inpractice14.1kgglucose/hwillleadtotheaerobicstageand42.1kgglucose/htotheanaerobicstage.Thefermentationprocessresultedin7.6kgofdryyeastfromtheaerobicfermentationand3.2kgfromtheanaerobicone.Therangeof solublenitrogencompoundsaccountedfor40–45%of the acid-fermented liquid, and the yeastdryweighthadaproteincontentof40–45%.Inaddition,19.6kg/hofethanol,

Breadreturns

Water

Starch hydrolysis

Protein hydrolysis

Lactic acid fermentation

Feed

Ethanol

Carbon dioxide

Liquid sour

Liquid yeast

Fermentationsubstrate

Anaerobic fermentationAerobic fermentation

Figure 19.1 Simplified flow sheet for the recycling of bread returns. (Adapted from Meuser, F. 1998. Process for recycling bakery products, more specially rests of bread and bread remainders. International patent number EP0821877, filed July 11, 1997, issued February 4, 1998.)


18.5kg/hofcarbondioxide,20–24kg/hoffibers,and220–240kg/hofacidliquorwereproduced.Thosevaluesrefertothetransformationofglucoseandproteinintotheendproducts,whereasthedischargedmassincludesthewetmassofyeastandfiber.Theyieldofethanolandcarbondioxidereferstoanefficiencyofdistillationorliquefactionof90%ofthemassflowoftheanaerobicfermentationstep.

Meuser andMartens (2009) estimated the economic viability ofthe recyclingprocessgivingananalysisof thebreak-evenpoint forthe application of the processing of bread returns in the industrialbakery.Thecalculationof theeconomicviabilitywasestimated forrecycling100kgofbread returns.Theobtainedproductswill yield1943×106€/a,includingliquidyeast,proteins,ethanol,carbondiox-ide,andfeedstuff,whereastherunningcosts(electricity,enzymesandnutrients,air,water,etc.)willbe687€/aandthefixedcost(invest-mentinterest,maintenance,andstaff)willreach1103€/a;thus,thefinal balance for this process will be 153€/a, confirming the costeffectivenessofthisrecyclingprocess.

Insummary,staleandbreadremainsareconvertedbyenzymaticandfermentativeprocessingintorawandauxiliarymaterialsfortheproductionofbreadandotherbakeryproducts,whichcouldclosetheproductioncycleinasustainableway.Thisbreadisbackinthepro-cessstagesofmanufactureofbread.Thespecialadvantageisthatthetransformation of bread in return for bread-making essential com-modities,inparticular,theyeast,isassociatedwithavalue.Infactthetransformation of bread in return for bread-making essential com-modities,inparticular,theyeast,attributesmorevaluetothemate-rial.Afurtheradvantageisthattheenergyrequiredforthiseffortcanbekeptlowbyusingthewasteheatoftheoven.Finally,itshouldbementionedthattheapplicationoftheprocedurerepresentsanenvi-ronmentally friendly measure, since it helps to increase the energyuse for thebakingof thenecessary rawandauxiliarymaterials forproduction,botheconomicallyandnutritionally.

19.7 Future Trends, Bottlenecks, and Research Gaps

Economical and environmental benefits could be derived when thevalorizationoftheby-productsiscombinedwiththereductionofthewaste.However,implementationofthesystemsforreducingwasteand


improvingenvironmentalperformancerequirestheactiveinvolvementofemployeeteamswhohelptoidentifyareasthatrequirewastemini-mization.Thevariablecompositionofthebakeriesandconfectionerywastesrenders theprocessingorrecyclingof thoseby-productsverydifficult into value-added compounds. Development of rapid tech-niquesforcharacterizingthoseproductsisneededtoidentifyitspos-sible recycling process. Further research is needed for hydrolyzingpentosesugar,makingitavailableforethanolproduction.

Differentstrategiesandprocesseshavebeenreportedinscientificdocumentsandpatentsbuttheglobal implementationatthediffer-entstagesofprocessingandtheutilizationsystemarerequired.Therecycling of thedifferent by-products or wastes must be integratedintotheproductioncycletomeettheholisticconceptintheproduc-tionsystem,whichinturnwillcontributetosustainableproduction.Waste minimization initiatives will have a positive impact on theconsumption of raw materials, reduction in energy and water dis-posal cost, andwastedisposal cost.Theexploitationof clean/greenproductiontechnologiesfor(a)upgradingbakeriesandconfectioneryby-product residues for the production of existing and novel typesofproductsbymeansofbioconversionviaSSFand (b) theconver-sionofbakerywastes intooperating supplies suchasbioadsorbentsforwastewatertreatmentwouldresultinsustainableproductionandenvironmentalandeconomicbenefitsinmanufacturing,monitoring,andwastemanagement.

ReferencesAfzalzadeh,A.,Boorboor,A.,Fazaeli,H.,Kashan,N.,andGhandi,D.2007.

Effectofbakerywasteonsheepperformanceandthecarcassfatquality.Journal of Animal and Veterinary Advances6:559–562.

Al-Tulaihan,A.A.,Najib,H.,andAl-Eid,S.M.2004.Thenutritionalevalua-tionoflocallyproduceddriedbakerywaste(DBW)inthebroilerdiets.Pakistan Journal of Nutrition3:294–299.

Arosemena, A., DePeters, E. J., and Fadel, J. G. 1995. Extent of variabilityinnutrientcompositionwithinselectedby-productfeedstuffs.Feedstuffs61:32–37.

Arvanitoyannis, I. S. andTserkezou, P. 2008. Wheat, barley and oat waste:Acomparativeandcriticalpresentationofmethodsandpotentialusesof treated waste. International Journal of Food Science and Technology43:694–725.

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