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Food Chemistry H.-D. Belitz · W. Grosch · P. Schieberle Food Chemistry 4th revised and extended ed. With481Figures,923Formulasand634Tables 123 ProfessorDr.Hans-DieterBelitz† Professorem.Dr.WernerGrosch Ehem.apl.ProfessorfürLebensmittelchemie anderTechnischenUniversitätMünchen Ehem.stellvertr.DirektorderDeutschenForschungsanstalt fürLebensmittelchemieMünchen Lichtenbergstraße 85748Garching ProfessorDr.PeterSchieberle OrdinariusfürLebensmittelchemie anderTechnischenUniversitätMünchen LeiterdesInstitutsfürLebensmittelchemie anderTechnischenUniversitätMünchen DirektorderDeutschenForschungsanstalt fürLebensmittelchemieMünchen Lichtenbergstraße 85748Garching ISBN 978-3-540-69933-0 e-ISBN 978-3-540-69934-7 DOI10.1007/978-3-540-69934-7 LibraryofCongressControlNumber:2008931197 ©Springer-VerlagBerlinHeidelberg2009 Thisworkissubjecttocopyright.Allrightsarereserved,whetherthewholeorpartofthemate- rialisconcerned,specificallytherightsoftranslation,reprinting,reuseofillustrations,recitation, broadcasting, reproduction onmicrofilmorinanyotherway,andstorageindatabanks.Dupli- cationofthispublication orpartsthereofispermittedonlyundertheprovisionsoftheGerman CopyrightLawofSeptember9,1965,initscurrentversion,andpermissionforusemustalways beobtainedfromSpringer.ViolationsareliabletoprosecutionundertheGermanCopyrightLaw. Theuseofgeneraldescriptivenames,registerednames,trademarks,etc.inthispublicationdoes notimply,evenintheabsenceofaspecificstatement,thatsuchnamesareexemptfromtherelevant protectivelawsandregulationsandthereforefreeforgeneraluse. Production:le-texpublishingservicesoHG,Leipzig Typesetting:le-texpublishingservicesoHG,Leipzig Coverdesign:KünkelLopkaGmbH,Heidelberg,Germany Printedonacid-freepaper 987654321 springer.com Preface Preface to the FirstGermanEdition The very rapid development of food chemistry and technology over the last two decades,whichisduetoaremarkableincreaseintheanalyticalandmanufacturing possibilities, makes the complete lack of a comprehensive, teaching or reference text particularly noticeable. It is hoped that this textbook of food chemistry will helptofillthisgap.Inwritingthisvolumewewereabletodrawonourexperience from the lectures which wehave given, covering various scientificsubjects, over thepastfifteenyearsattheTechnicalUniversityofMunich. Sinceaseparatetreatmentoftheimportantfoodconstituents(proteins,lipids,car- bohydrates,flavorcompounds,etc.)andoftheimportantfoodgroups(milk,meat, eggs,cereals,fruits,vegetables,etc.)hasprovedsuccessfulinourlectures,thesub- jectmatterisalsoorganizedinthesamewayinthisbook. Compounds which are found only in particular foods are discussed where they play a distinctive role while food additives and contaminants are treated in their ownchapters.Thephysical andchemical properties oftheimportant constituents of foods are discussed in detail where these form the basis for understanding ei- therthereactionswhichoccur,orcanbeexpectedtooccur,duringtheproduction, processing,storageandhandlingoffoodsorthemethodsusedinanalyzingthem. Anattempthasalsobeenmadetoclarifytherelationshipbetweenthestructureand propertiesatthelevelofindividualfoodconstituentsandatthelevelofthewhole foodsystem. The book focuses on the chemistry of foodstuffs and does not consider national or international food regulations. We have also omitted a broader discussion of aspectsrelatedtothenutritionalvalue,theprocessingandthetoxicologyoffoods. Alloftheseareanessentialpartofthetrainingofafoodchemistbut,becauseofthe extent of thesubject matterand theconsequent specialization, must today bethe subjectofseparatebooks.Nevertheless,forallimportant foodswehaveincluded briefdiscussionsofmanufacturing processesandtheirparameterssincetheseare closelyrelatedtothechemicalreactionsoccurringinfoods. Commodityandproductiondataofimportancetofoodchemistsaremainlygiven in tabular form. Each chapter includes some references which are not intended toformanexhaustivelist.Nopreferenceorjudgementshouldbeinferredfromthe choiceofreferences;theyaregivensimplytoencouragefurtherreading.Additional literatureofamoregeneralnatureisgivenattheendofthebook. This book is primarily aimed both at students of food and general chemistry but alsoatthosestudentsofotherdisciplineswhoarerequiredorchoosetostudyfood chemistry asasupplementary subject. Wealsohope that thiscomprehensive text vi Preface will prove useful to both food chemists and chemists who have completed their formaleducation. WethanksincerelyMrs.A.Mödl(foodchemist),Mrs.R.Berger,Mrs.I.Hofmeier, Mrs.E.Hortig,Mrs.F.LynenandMrs.K.Wüstfortheirhelpduringtheprepara- tionofthemanuscriptanditsproofreading.WeareverygratefultoSpringerVerlag fortheirconsiderationofourwishesandfortheagreeablecooperation. Garching, H.-D.Belitz July1982 W.Grosch Preface to the FourthEnglishEdition The fourth edition of the “Food Chemistry” textbook is a translation of the sixth German edition of this textbook. It follows a general concept as detailed in the preface tothefirsteditiongiven below. Allchapters have beencarefully checked and updated with respect to the latest developments, if required. Comprehensive changeshavebeenmadeinChapters9(Contaminants),18(PhenolicCompounds), 20 (Alcoholic Beverages)and 21(Tea, Cocoa). Thefollowing topics werenewly added: (cid:129) thedetectionofBSEandD-aminoacids, (cid:129) theformationandoccurrenceofacrylamideandfuran, (cid:129) compoundshavingacoolingeffect, (cid:129) technologicallyimportantmilkenzymes, (cid:129) thelipoproteinsofeggyolk, (cid:129) thestructureofthemuscleandmeataging, (cid:129) foodallergies, (cid:129) thebakingprocess, (cid:129) thereactivityofoxygenspeciesinfoods, (cid:129) phytosterols, (cid:129) glycemicindex, (cid:129) thecompositionofaromaswasextended:odorants(pineapple,rawandcooked mutton, black tea, cocoa powder, whisky) and taste compounds (black tea, roastedcocoa,coffeedrink). Theproduction datafortheyear2006weretakenfromtheFAOviaInternet.The volumeofthebookwasnotchangedduringtherevisionassomeexistingchapters wereshortened. Weareverygrateful toDr.MargaretBurghagen fortranslatingthemanuscript.It wasourpleasuretocollaboratewithher. WewouldalsoliketothankProf.Dr.JürgenWederandDr.RolfKiefferforseveral valuablerecommendations.WearealsogratefultoSabineBijewitzandRitaJauker forassistanceincompletingthemanuscript,andChristelHoffmannforhelpwith theliteratureandtheindex. Garching, W.Grosch Mai2008 P.Schieberle Contents 0 Water................................................. 1 0.1 Foreword .............................................. 1 0.2 Structure............................................... 1 0.2.1 WaterMolecule......................................... 1 0.2.2 LiquidWaterandIce .................................... 2 0.3 EffectonStorageLife.................................... 3 0.3.1 WaterActivity .......................................... 3 0.3.2 WaterActivityasanIndicator ............................. 5 0.3.3 PhaseTransitionofFoodsContainingWater................. 5 0.3.4 WLFEquation.......................................... 6 0.3.5 Conclusion............................................. 7 0.4 References ............................................. 7 1 AminoAcids,Peptides,Proteins ......................... 8 1.1 Foreword .............................................. 8 1.2 AminoAcids ........................................... 8 1.2.1 GeneralRemarks........................................ 8 1.2.2 Classification,DiscoveryandOccurrence ................... 9 1.2.2.1 Classification........................................... 9 1.2.2.2 DiscoveryandOccurrence................................ 9 1.2.3 PhysicalProperties ...................................... 12 1.2.3.1 Dissociation............................................ 12 1.2.3.2 ConfigurationandOpticalActivity......................... 13 1.2.3.3 Solubility .............................................. 14 1.2.3.4 UV-Absorption ......................................... 15 1.2.4 ChemicalReactions ..................................... 16 1.2.4.1 EsterificationofCarboxylGroups.......................... 16 1.2.4.2 ReactionsofAminoGroups............................... 16 1.2.4.2.1 Acylation .............................................. 16 1.2.4.2.2 AlkylationandArylation ................................. 18 1.2.4.2.3 CarbamoylandThiocarbamoylDerivatives.................. 20 1.2.4.2.4 ReactionswithCarbonylCompounds....................... 21 1.2.4.3 ReactionsInvolvingOtherFunctionalGroups................ 22 1.2.4.3.1 Lysine................................................. 23 1.2.4.3.2 Arginine............................................... 23 1.2.4.3.3 AsparticandGlutamicAcids.............................. 23 1.2.4.3.4 SerineandThreonine .................................... 24 1.2.4.3.5 CysteineandCystine .................................... 24 1.2.4.3.6 Methionine............................................. 24 1.2.4.3.7 Tyrosine ............................................... 24 viii Contents 1.2.4.4 ReactionsofAminoAcidsatHigherTemperatures ........... 25 1.2.4.4.1 Acrylamide ............................................ 25 1.2.4.4.2 MutagenicHeterocyclicCompounds ....................... 26 1.2.5 SyntheticAminoAcidsUtilizedforIncreasing theBiologicalValueofFood(FoodFortification)............. 29 1.2.5.1 GlutamicAcid.......................................... 32 1.2.5.2 AsparticAcid........................................... 32 1.2.5.3 Lysine................................................. 32 1.2.5.4 Methionine............................................. 33 1.2.5.5 Phenylalanine .......................................... 33 1.2.5.6 Threonine.............................................. 33 1.2.5.7 Tryptophan............................................. 33 1.2.6 SensoryProperties ...................................... 34 1.3 Peptides ............................................... 34 1.3.1 GeneralRemarks,Nomenclature........................... 34 1.3.2 PhysicalProperties ...................................... 36 1.3.2.1 Dissociation............................................ 36 1.3.3 SensoryProperties ...................................... 36 1.3.4 IndividualPeptides ...................................... 38 1.3.4.1 Glutathione ............................................ 38 1.3.4.2 Carnosine,AnserineandBalenine ......................... 39 1.3.4.3 Nisin.................................................. 39 1.3.4.4 LysinePeptides ......................................... 40 1.3.4.5 OtherPeptides.......................................... 40 1.4 Proteins ............................................... 40 1.4.1 AminoAcidSequence ................................... 41 1.4.1.1 AminoAcidComposition,Subunits ........................ 41 1.4.1.2 TerminalGroups ........................................ 42 1.4.1.3 PartialHydrolysis ....................................... 43 1.4.1.4 SequenceAnalysis ...................................... 44 1.4.1.5 DerivationofAminoAcidSequence fromtheNucleotideSequenceoftheCodingGene ........... 46 1.4.2 Conformation .......................................... 48 1.4.2.1 ExtendedPeptideChains ................................. 48 1.4.2.2 SecondaryStructure(RegularStructuralElements) ........... 49 1.4.2.2.1 β-Sheet................................................ 50 1.4.2.2.2 HelicalStructures ....................................... 51 1.4.2.2.3 ReverseTurns .......................................... 52 1.4.2.2.4 Super-SecondaryStructures............................... 52 1.4.2.3 TertiaryandQuaternaryStructures ......................... 53 1.4.2.3.1 FibrousProteins ........................................ 53 1.4.2.3.2 GlobularProteins ....................................... 53 1.4.2.3.3 BSE .................................................. 55 1.4.2.3.4 QuaternaryStructures.................................... 56 1.4.2.4 Denaturation ........................................... 56 1.4.3 PhysicalProperties ...................................... 58 1.4.3.1 Dissociation............................................ 58 1.4.3.2 OpticalActivity......................................... 60 1.4.3.3 Solubility,HydrationandSwellingPower ................... 60 1.4.3.4 FoamFormationandFoamStabilization .................... 62 1.4.3.5 GelFormation .......................................... 62 Contents ix 1.4.3.6 EmulsifyingEffect ...................................... 63 1.4.4 ChemicalReactions ..................................... 64 1.4.4.1 LysineResidue ......................................... 64 1.4.4.1.1 ReactionsWhichRetainthePositiveCharge................. 64 1.4.4.1.2 ReactionsResultinginaLossofPositiveCharge ............. 65 1.4.4.1.3 ReactionsResultinginaNegativeCharge ................... 65 1.4.4.1.4 ReversibleReactions..................................... 66 1.4.4.2 ArginineResidue........................................ 66 1.4.4.3 GlutamicandAsparticAcidResidues ...................... 67 1.4.4.4 CystineResidue(cf.alsoSection1.2.4.3.5).................. 67 1.4.4.5 CysteineResidue(cf.alsoSection1.2.4.3.5)................. 68 1.4.4.6 MethionineResidue ..................................... 69 1.4.4.7 HistidineResidue ....................................... 69 1.4.4.8 TryptophanResidue ..................................... 70 1.4.4.9 TyrosineResidue........................................ 70 1.4.4.10 BifunctionalReagents ................................... 70 1.4.4.11 ReactionsInvolvedinFoodProcessing ..................... 70 1.4.5 Enzyme-CatalyzedReactions ............................. 74 1.4.5.1 Foreword .............................................. 74 1.4.5.2 ProteolyticEnzymes..................................... 74 1.4.5.2.1 SerineEndopeptidases ................................... 74 1.4.5.2.2 CysteineEndopeptidases ................................. 76 1.4.5.2.3 MetaloPeptidases....................................... 76 1.4.5.2.4 AsparticEndopeptidases ................................. 76 1.4.6 ChemicalandEnzymaticReactions ofInteresttoFoodProcessing ............................. 79 1.4.6.1 Foreword .............................................. 79 1.4.6.2 ChemicalModification................................... 80 1.4.6.2.1 Acylation .............................................. 80 1.4.6.2.2 Alkylation ............................................. 82 1.4.6.2.3 RedoxReactionsInvolvingCysteineandCystine............. 82 1.4.6.3 EnzymaticModification.................................. 83 1.4.6.3.1 Dephosphorylation ...................................... 83 1.4.6.3.2 PlasteinReaction........................................ 83 1.4.6.3.3 Cross-Linking .......................................... 86 1.4.7 TexturizedProteins...................................... 87 1.4.7.1 Foreword .............................................. 87 1.4.7.2 StartingMaterial ........................................ 88 1.4.7.3 Texturization ........................................... 88 1.4.7.3.1 SpinProcess ........................................... 88 1.4.7.3.2 ExtrusionProcess ....................................... 89 1.5 References ............................................. 89 2 Enzymes .............................................. 93 2.1 Foreword .............................................. 93 2.2 GeneralRemarks,IsolationandNomenclature ............... 93 2.2.1 Catalysis............................................... 93 2.2.2 Specificity ............................................. 94 2.2.2.1 SubstrateSpecificity..................................... 94 2.2.2.2 ReactionSpecificity ..................................... 95 2.2.3 Structure............................................... 95 x Contents 2.2.4 IsolationandPurification ................................. 96 2.2.5 MultipleFormsofEnzymes............................... 97 2.2.6 Nomenclature .......................................... 97 2.2.7 ActivityUnits .......................................... 98 2.3 EnzymeCofactors....................................... 98 2.3.1 Cosubstrates............................................ 99 2.3.1.1 NicotinamideAdenineDinucleotide........................ 99 2.3.1.2 AdenosineTriphosphate.................................. 102 2.3.2 ProstheticGroups ....................................... 102 2.3.2.1 Flavins ................................................ 102 2.3.2.2 Hemin................................................. 103 2.3.2.3 PyridoxalPhosphate..................................... 103 2.3.3 MetalIons ............................................. 104 2.3.3.1 Magnesium,CalciumandZinc ............................ 104 2.3.3.2 Iron,CopperandMolybdenum ............................ 105 2.4 TheoryofEnzymeCatalysis .............................. 106 2.4.1 ActiveSite ............................................. 106 2.4.1.1 ActiveSiteLocalization.................................. 107 2.4.1.2 SubstrateBinding ....................................... 108 2.4.1.2.1 Stereospecificity ........................................ 108 2.4.1.2.2 “LockandKey”Hypothesis............................... 109 2.4.1.2.3 Induced-fitModel ....................................... 109 2.4.2 ReasonsforCatalyticActivity............................. 110 2.4.2.1 StericEffects–OrientationEffects......................... 111 2.4.2.2 StructuralComplementaritytoTransitionState............... 112 2.4.2.3 EntropyEffect .......................................... 112 2.4.2.4 GeneralAcid–BaseCatalysis.............................. 113 2.4.2.5 CovalentCatalysis ...................................... 114 2.4.3 ClosingRemarks........................................ 117 2.5 KineticsofEnzyme-CatalyzedReactions ................... 117 2.5.1 EffectofSubstrateConcentration .......................... 117 2.5.1.1 Single-SubstrateReactions ............................... 117 2.5.1.1.1 Michaelis–MentenEquation .............................. 117 2.5.1.1.2 DeterminationofK andV............................... 120 m 2.5.1.2 Two-SubstrateReactions ................................. 121 2.5.1.2.1 OrderofSubstrateBinding ............................... 121 2.5.1.2.2 RateEquationsforaTwo-SubstrateReaction ................ 122 2.5.1.3 AllostericEnzymes...................................... 123 2.5.2 EffectofInhibitors ...................................... 125 2.5.2.1 IrreversibleInhibition.................................... 126 2.5.2.2 ReversibleInhibition .................................... 126 2.5.2.2.1 CompetitiveInhibition ................................... 126 2.5.2.2.2 Non-CompetitiveInhibition............................... 127 2.5.2.2.3 UncompetitiveInhibition ................................. 128 2.5.3 EffectofpHonEnzymeActivity .......................... 128 2.5.4 InfluenceofTemperature ................................. 130 2.5.4.1 TimeDependenceofEffects .............................. 131 2.5.4.2 TemperatureDependenceofEffects ........................ 131 2.5.4.3 TemperatureOptimum ................................... 133 2.5.4.4 ThermalStability ....................................... 134 2.5.5 InfluenceofPressure .................................... 136