Biochemistry of Foods

559 Pages·2012·16.354 MB·English

Biochemistry of Foods
Third Edition
Edited by
N. A. Michael Eskin and Fereidoon Shahidi
AMSTERDAMlBOSTONlHEIDELBERGlLONDONlNEWYORKlOXFORDlPARIS
SANDIEGOlSANFRANCISCOlSINGAPORElSYDNEYlTOKYO
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Wewould like to dedicate this book to:
Dr. H. Michael Henderson, a dear friend and
colleaguewith whom one of us (Michael Eskin) wrote the first edition of
BIOCHEMISTRYOF FOODS in 1971, who passed away in 2009.
Preface
The advances made since the publication of the first presents important information on the biochemical
edition of Biochemistry of Foods in 1971 have been changesassociatedwiththedevelopmentofeggs.PartII
extraordinary. This was evident by the more compre- focuses on the biochemical changes occurring during
hensive approach taken in preparing the second edition processing.Chapter6presentsanextensivecoverageof
in1990.Inthethirdeditionwehavetriedtokeeptrueto non-enzymatic browning reactions in foods during
the second edition by significantly updating certain heating and storage. Chapter 7 details the biochemistry
chapters,addingseveralnewchapters,andreplacingthe ofbrewing,andChapter8providesadetaileddiscussion
chapter on food enzymes with recombinant DNA tech- of the biochemical processes involved in producing
nologies. It is a real privilege and pleasure to have cheeseandyogurt.Chapter9reviewsoilprocessingand
written an important textbook that spans almost my fat modification. Part III deals with selected areas
entire career as a food biochemist. I was particularly associated with food spoilage. Chapter 10 presents
delighted that Dr. Fereidoon Shahidi agreed to co-edit a detailed discussion of enzymatic browning, while
thiseditionandtogetherwehavetriedtopresentabook Chapter 11 provides a comprehensive review of lipid
thatstandsoutasanauthoritativetextbookforteachers, oxidation. The final chapter in this section, Chapter 12,
students, and researchers in this very important and provides an updated and revised coverage of off-flavors
dynamic field in food science. in milk. The final section, Part IV, on Biotechnology,
Thebookisorganizedintofourmajorsections.PartI provides an extensive review of recombinant DNA
deals with important biochemical changes occurring in technologies in Chapter 13.
rawfoodsthataffectquality.Inadditiontodiscussingthe In this edition we are particularly grateful to
biochemistry of cereal development in Chapter 1, colleagues from around the world for their important
a section has been added on legumes. Chapter 2 covers contributions to many of the chapters in this book. We
postharvestchangesinfruitsandvegetableswithamore are also appreciative of our wives for allowing us the
extensive discussion of flavor and storage. Chapter 3 manyhoursneededtopullthisbooktogether.Finally,we
provides an in-depth discussion of postmortem changes would like to acknowledge the outstanding editorial
responsible for converting muscle into edible meat and assistanceprovidedbythestaffofElsevierthatmadethe
fish. Chapter 4 covers the latest information on the completion of this book a labor of love.
complex chemical changes involved in the biosynthesis
of milk. The last chapter in this section, Chapter 5, N.A. Michael Eskin and Fereidoon Shahidi
xv
List of Contributors
MichelAliani,DepartmentofHumanNutritionalSciences, KarenM.Schaich,DepartmentofFoodScience,Rutgers
University of Manitoba, Winnipeg, Manitoba, Canada University, New Brunswick, New Jersey, USA
Peter Eck, Department of Human Nutritional Sciences, Fereidoon Shahidi, Department of Biochemistry,
University of Manitoba, Winnipeg Manitoba, Canada Memorial University of Newfoundland, St. John’s,
Newfoundland, Canada
N. A. Michael Eskin, Department of Human Nutritional
Sciences, University of Manitoba, Winnipeg, Manitoba, Margaret Slavin, Department of Nutrition and Food
Canada Studies, George Mason University, Fairfax, Virginia,
USA
H.DouglasGoff,DepartmentofFoodScience,University
of Guelph, Ontario, Canada Graham G. Stewart, GGStewart Associates, 13 Heol
Nant Castan, Rhiwbina, Cardiff, UK
Juan He, Department of Food Science and Technology,
Oregon State University, Corvallis, Oregon, USA VeraLu´ciaValenteMesquita,DepartamentodeNutric¸a˜o
Ba´sica e Experimental, Instituto de Nutric¸a˜o Josue´ de
Arthur R. Hill, Department of Food Science, University
Castro,UniversidadeFederaldoRiodeJaneiro,Brazil
of Guelph, Guelph, Ontario, Canada
Pedro Vazquez-Landaverde, CICATA-IPN Unidad
Chi-Tang Ho, Food Science Department, Cook College,
Queretaro, Colonia Colinas del Cimatario, Queretaro,
Rutgers University,NewBrunswick,NewJersey,USA
Mexico
ErnstHoehn,SwissFederalResearchStation,Switzerland
Monica Whent, Department of Nutrition and Food
Prashanti Kethireddipalli, Department of Food Science,
Science, University of Maryland, College Park,
University of Guelph, Guelph, Ontario, Canada
Maryland, USA
Herman Lutterodt, Department of Nutrition and Food
Liangli Yu, Department of Nutrition and Food
Science, University of Maryland, College Park,
Science, University of Maryland, College Park,
Maryland, USA
Maryland, USA
Yoshinori Mine, Department of Food Science, University
Hua Zhang, Department of Food Science, University of
of Guelph, Guelph, Ontario, Canada
Guelph, Guelph, Ontario, Canada
Michael C. Qian, Department of Food Science and
Ying Zhong, Department of Biochemistry, Memorial
Technology, Oregon, Oregon State University,
University of Newfoundland, St. John’s, Newfoundland,
Corvallis, Oregon, USA
Canada
Christiane Queiroz, Departamento de Nutric¸a˜o Ba´sica e
Kequan Zhou, Department of Nutrition and Food
Experimental, Instituto de Nutric¸a˜o Josue´ de Castro,
Science, Wayne State University, Detroit, Michigan,
Universidade Federal do Rio de Janeiro, Brazil
USA
xvii
Chapter 1
Cereals and Legumes
y z
Kequan Zhou,* Margaret Slavin, HermanLutterodt,** Monica Whent,** N. A.Michael Eskin and LiangliYu**
*DepartmentofNutritionandFoodScience,WayneStateUniversity,Detroit,Michigan,USA,yDepartmentofNutritionandFoodStudies,GeorgeMason
University,Fairfax,Virginia,USA,**DepartmentofNutritionandFoodScience,UniversityofMaryland,CollegePark,Maryland,USA,zDepartmentof
HumanNutritionalScience,UniversityofManitoba,Winnipeg,Manitoba,Canada
Chapter Outline
Part I: Cereals 4 I. Introduction 24
I. Introduction 4 II. Legume Seed Structure 24
II. Cereal Grain Structure 4 III. Legume Seed Composition 24
III. Cereal Grain Composition 5 A. Proximate Composition 24
A. Amyloplasts 6 B. Protein 26
B. The Starch Granule 6 1. Nitrogen Fixation 26
C. Biosynthesis of Starch 7 2. Classification 27
D. Sucrose Starch Conversion in 3. Protein Structure and Properties 27
Developing Grains 7 4. Protein Quality 29
E. Starch Synthesis 10 C. Carbohydrates 29
F. Starch Synthesis: Amylopectin 10 1. Overview 29
G. Protein Bodies 11 2. Insoluble Carbohydrate 30
H. Origin of Protein Bodies 11 3. Soluble Carbohydrate 32
I. Classification of Plant Proteins 12 4. Conclusion 33
J. Prolamins 13 D. Lipids 34
K. Protein Synthesis 14 E. Other Components of Interest 34
L. Lipids 15 1. Enzyme Inhibitors 34
IV. Germination of Cereals 16 2. Lectins 35
A. Mobilization of Cereal Starches by 3. Lipoxygenase 36
a-Amylase 16 IV. Effects of Germination 36
B. Biosynthesis of a-Amylase during A. Carbohydrates 36
Germination 16 B. Lipids 36
C. a-Amylase Activity in Germinated C. Proteins 37
Cereals 18 D. Vitamins and Minerals 37
D. EffectofGerminationonFlourQuality 18 E. Anti-Nutritional Factors 38
E. Treatment of Sprouted Grain: 1. Trypsin Inhibitor Activity 38
Reduction of a-Amylase 18 2. Phytic Acid 38
F. Mobilization of Proteins during F. Nutraceutical Components 38
Germination 19 G. Esthetic Food Quality 39
G. Lipid Mobilization during V. Effects of Fermentation 39
Germination 20 VI. Storage 40
V. Storage of Grains 22 A. Respiration, Moisture, and
A. Respiration 22 Temperature 40
1. Effect of Moisture Content 22 B. Seed Aging and Food Quality 40
2. Effect of Temperature 23 C. Effect on Isoflavones 41
B. Prolonged Storage of Grains and Flour 23 References 41
Part II: Legumes 24
BiochemistryofFoods.DOI:http://dx.doi.org/10.1016/B978-0-12-242352-9.00001-1
Copyright(cid:1)2013ElsevierInc.Allrightsreserved. 3
4 Chapter | 1 Cereals andLegumes
PART I: CEREALS
I. INTRODUCTION
Cerealsare membersofthe largemonocotyledonousgrassfamily,theGramineae,whichmainlyconsists ofwheat,
maize,barley,oats,rice,andsorghum(Andersonetal.,2000).Cereal-basedfoodshavebeenastapledietarysource
for the world’s population for centuries. Cereal grains contain the macronutrients (protein, fat, and carbohydrate)
requiredbyhumansforgrowthandmaintenance,contributingapproximately70%and50%ofthetotalcaloriesand
protein, respectively (Topping, 2007). Cereal grains also supply important minerals, vitamins, and other micro-
nutrientsessentialforoptimalhealth.Theystillprovide20%ofmagnesiumandzinc,30e40%ofcarbohydrateand
iron, 20e30% of riboflavin and niacin, and over 40% of thiamine in the diet (Marston and Welsh, 1980). Global
cerealproductionpercapitafluctuatedaround280kgperyearduringthefirsthalfofthetwentiethcentury,asseenin
Figure1.1(Gilland,2002).Theworldproductionofcerealisprojectedtobe3555Mt,withpercapitaproductionof
378kg(Gilland,1998).Cereal-basedfood,especiallywholegrains,haveshownthepotentialforhealthpromotion,
linkingtoreducedriskofseveralchronicdiseasessuchascoronaryheartdisease,type2diabetes,andcertaintypesof
cancer (Truswell, 2002; Montonen et al., 2003; Slavin, 2000; Slavin et al., 1999). These beneficial effects are
attributedtonumerousphytochemicalscontainedinthegrains.Therefore,thischapterwilldiscussthosebiochemical
changes taking place during development, germination, and storage of cereal grains, with particular attention to
wheat.
II. CEREAL GRAIN STRUCTURE
The different tissues constituting the cereal seed are generally described in terms of their embryogenic origin and
structure(Eversetal.,1999).Thecerealseediscomposedofthreemaintissues:theembryo,theendosperm,andthe
aleuronelayersurroundingthestorageendosperm.ThisisillustratedforwheatinFigure1.2,inwhichtheendosperm
comprises over 80% of the grain weight while the aleurone cells and the germ tissue containing the embryo
embedded in the surrounding scutellum account for 15% and 3%, respectively. The peripheral tissues of the grain
overlyingthestarchyendospermaremadeupsuccessivelyfromtheoutertotheinnersurface:theouterpericarp,the
inner pericarp, seed coat, hyaline layer, and the aleurone layer (Barrona et al., 2007). The germ comprises the
embryonicaxisandthescutellum.Theanatomicalstructureofallcerealgrainsisessentiallysimilarwithsomeminor
FIGURE1.1 Cerealproductionpercapita,1980e2000.(Sources:FAOSTAT;USBureauoftheCensus;adaptedfromGilland,2002.)
III. CerealGrainComposition 5
FIGURE 1.2 Diagram of wheat
grain showing major structures in
(A) longitudinal and (B) transverse
sections (Rathjen et al., 2009 with
permission).
differences.Forinstance,wheatandmaizearesurroundedbyafruitcoatorpericarpandseedcoatortesta,together
referredtoasanakedcaryopsis.Inthecaseofbarley,oats,andrice,however,anadditionalhuskisfoundsurrounding
the caryopsis or kernel of the grain.
III. CEREAL GRAIN COMPOSITION
Cerealgrainsarehighlynutritious,andthemajorcomponentsofthegrainareproteins(approximately10e15%)and
starch(approximately60e70%ofgrain),withnon-starchpolysaccharidesderivedfromthecellwallsaccountingfor
about 3e8% of the total (Saulniera et al., 2007). The composition of cereals varies and highly depends on grain
variety, growing conditions, husbandry, and infection (Tester, 1995). The starchy endosperm constitutes the major
portion of the cereal seed and provides the nutrients necessary for embryo development during germination. The
nutrients are made available by the release of enzymes from the aleurone layer and embryo, which hydrolyze the
endospermreserves.Thesereservesarecontainedindiscretestoragebodiesidentifiedasstarchgranulesandprotein
bodies.Thesecomponentshavemajoreffectsontheuseofcerealgrainduetotheirphysiochemicalpropertiesduring
milling and foodprocessing. It is worth notingthat the non-digestible carbohydrates in cereal grains have received
increased attention as a significant source of dietary fiber, and are purported to have an impact on the nutritional
qualityandhealth-enhancingeffectsofcerealfoods(Salmeronetal.,1997).Inaddition,polysaccharidesincereals
are associated with many other substances, mostly with proteins, polyphenols, and phytate, which can modify
mineral binding by dietary fiber (Vitali et al., 2008).
6 Chapter | 1 Cereals andLegumes
A. Amyloplasts
Amyloplastsareplastidsororganellesresponsibleforthestorageofstarchgranules.Therateofstarchsynthesisin
cereal grains is one of the factors affecting both grain size and yield (Kumar and Singh, 1980). In the mature
endospermofwheat,barley,andrye,starchisfoundastwodistinctfractionsbasedonthesizeofthegranules.The
primary or A-type starch granules range in size from 20 to 45mm, while the secondary or B-type granules rarely
exceed10mmindiameter(Evers,1973).Examinationoftheparticlesizedistributioninwheatendospermstarchby
Evers and Lindley (1977) showed that those starch granules less than 10mm in diameter accounted for approxi-
matelyone-thirdofthetotalweightofstarch.Thepresenceofthesetwostarchgranuletypesinwheatkernelswas
confirmed in studies by Baruch et al. (1979). They found that the size of the starch was affected by seasonal
changes in much the sameway as grain yield and protein content. The starch granule occupies only a very small
partofthetotalplastidduringinitialkerneldevelopmentbutaccountsforcloseto93%atmaturity(Briartyetal.,
1979). In the mature endosperm, A-type starch granules account for only 3% of the total number of granules
although they represent 50e70% of the total weight, owing to their larger size (Evers and Lindley, 1977). The
smaller B-type granules, however, make up 97% of the total number of starch granules but account for only
25e50% of the overall weight.
Isolatedstarchgranulesalsocontainprotein,mostofwhichcanberemovedbywashingrepeatedlywithwater.A
smallpartoftheprotein,however,remainsstronglyassociatedwiththegranuleitself.Lowyetal.(1981)foundthat
thisproteinfractionisreadilyextractedwithsaltsolutionandsuggestedthatitisassociatedwiththestarchgranule
surface.Thisextractablefractionaccountsfor8%ofthetotalproteininthestarchgranule.Themajorproteinfraction
hasamolecularweightofaround30,000andisassociatedwithbothA-andB-typestarchgranules.Basedonamino
acidanalysis,thisproteinisquitedifferentfromwheatgluten.AnadditionalproteinfractionwasextractedfromA-
type starch granules but only following gelatinization in the presence of sodium dodecyl sulfate. This fraction was
quite different, and based on electrophoresis, was thought to be part of the internal granule components.
B. The Starch Granule
Starch granule shape can be characteristic of a genus and species (Ellis, 1998). The shape and size of the starch
granulevarywiththedifferentcereals(Table1.1).Thesizedistributionofthestarchgranulesintheamyloplastsand
thecompositionofstarchgranulesandtheirpropertieschangeduringgranuledevelopment.ThelargeA-typestarch
granulesofwheat,barley,andryearelenticular,whilethesmallerB-typestarchgranulesaresphericalorpolyhedral.
Thestarchgranulesofrice,oats,andmaizeareirregularandpolyhedralinshape,thoseofricebeingcomparablein
size to the B-type starch granules of wheat and barley, while those of maize are larger (Ellis, 1998). Starch is
composedofamyloseandamylopectin,withthelevelofamyloserangingfrom20%to30%formostcerealstarches
(Katzetal.,1993).Inthecaseofcertainvarietiesofmaize,barley,andrice,thestarchiscomposedalmostexclusively
TABLE1.1 StructureandAmyloseContentofSomeWholeGranularCerealStarches
Source GranuleShape GranuleSize(nm) AmyloseContent(%)
Wheat Lenticularorround 20e25 22
Maize Roundorpolyhedral 15 28
Waxymaize Round 15(5e15) 1
High-amylose Roundorirregularsausage-shaped 25 52
Barley Roundorelliptical 20e25 22
Rice Polygonal 3e8 17e19a
21e23b
Oats Polyhedral 3e10 23e24
aJaponica
bIndica
AdaptedfromLineback(1984).
III. CerealGrainComposition 7
of amylopectin; these are referred to as ‘waxy’. High-amylose starches are also found, for example, in the case of
amylomaize.
A portion of amylose in the starch granule is complexed with lysophospholipids as a function of the stage of
developmentoftheendosperm,atwhichtheamyloseisformed(Morrison,1993).B-typegranulesareinitiatedlater
ingraindevelopmentthanA-typegranules.TheproportionsofamyloseandoflysophospholipidsroseinbothA-type
and B-type starch granules duringgrain development of wheat and barley(Morrison and Gadan, 1987; McDonald,
1991).
C. Biosynthesis of Starch
Sucroseisbelievedtobethemainsourceofcarbonforstarchsynthesisinthecerealendosperms,andisconvertedto
starchviaaseriesofenzyme-catalyzedreactions(Duffus,1993).Starchsynthesisisachievedthroughtheactionof
starchsynthase,whichcanutilizeeitheradenosinediphosphoglucose(ADPG)oruridinediphosphoglucose(UDPG)
asasubstrate(RecondoandLeloir,1961).ADPGappearstobethemoreactiveglucosyldonorandisformedbythe
action of ADPG-pyrophosphorylase (Preiss and Levi, 1979).
ATPþa-Glucose-1-P / ADPGþPP
i
The amount of inorganic pyrophosphate (PP) in developing grains is controlled by the enzyme alkaline inorganic
i
pyrophosphatase (EC 3.6.1.1). This enzyme limits the accumulation of PP and was thought to be the controlling
i
factor in starch synthesis, as PP inhibited ADPG-pyrophosphorylase in sweet corn (Amir and Cherry, 1972). The
i
activity of both ADPG-pyrophosphorylase and alkaline pyrophosphatase was studied by Kumar and Singh (1983)
during the development of wheat grain. Their results, shown in Figure 1.3, indicate that both enzymes increased
steadily,reachingamaximum28daysafteranthesis,butthendeclinedwithmaturity.Therapidincreaseinalkaline
pyrophosphataseactivity14daysafteranthesiscorrespondedwiththeperiodofrapidstarchsynthesis.Theinability
of the intermediate metabolites of sucroseestarch conversion to inhibit the activity of alkaline pyrophosphatase
eliminated any possible regulatory role for this enzyme in starch biosynthesis.
D. Sucrose Starch Conversion in Developing Grains
The amount offree sugars formed during the development of wheat was examined by Kumar and Singh (1981) in
relation to grain size and starch content. Their results, summarized in Figure 1.4, indicate that the non-reducing
sucrosereachedamaximumlevel14daysafteranthesis,thendeclinedandleveledoffafter28days.Starchsynthesis
FIGURE1.3 Activityofalkalineinorganicpyrophosphatase(B)andADPG-pyrophosphorylase(l)duringwheatgraindevelopment(Kumarand
Singh,1983).