The rheological and fracture properties of Gouda cheese 0000 0262 6824 Promotor: dr. ir. P. Walstra, hoogleraar in de Zuivelkunde Co-promotor: dr. ir. T. van Vliet, universitair hoofddocent Ono\, i^9 Hannemieke Luyten The rheological and fracture properties of Gouda cheese Proefschrift ter verkrijging van de graad van doctor in de landbouwwetenschappen, op gezag van de rector magnificus, dr. C. C. Oosterlee, in het openbaar te verdedigen op dinsdag 10 mei 1988 des namiddags te vier uur in de aula van de Landbouwuniversiteit te Wageningen BIBLIOTHEEK LANDBOUWUNIVERSITEIT WAGENINGEN /SAJ^ L/^&L&I^ fif/JOtlbi) \Z)*i STELLINGEN 1. Voorvee lmateriale nbepale nd evloeieigenschappe n het gedragbi jbreuk . Dit proefschrift/ - 2. Hetbestudere nva nhe treologisc hgedra gva nmelkgele ni s zeernutti gvoo rhe tbegrijpe nva nd econsistenti eva n -kaas. •Di t proefschrift. Materiaaleigenschappen vanlevensmiddele n kunnenhee lgoe d bestudeerd wordenme tcompressie- ,buig- ,rek - en/of afschuifmetingen,mit sd euitvoerin g vand eexperimente n en deberekenin g vand eresultate n goedgebeurt . Dit proefschrift. Kaaska nbeschouw d wordenal see ncomposietmateriaal :d e matrixbestaa tui tgezwolle neiwitdeeltjes ,vetbolletje s gedragen zichal svulstof . Dit proefschrift. Dekorthei d vankaa sword tvoornamelij k bepaald doord e eiwitafbraak, dep He nhe t zoutgehalte. Hoogstwaarschijnlijk isvergaand eafbraa kva nhe teiwi t totklein e brokstukken hierbijwezenlijk . Dit proefschrift. Devloeieigenschappe n vanGouds ekaa s zijn maximaal inhe t pH-gebied 5,15-5,35. Bijdez epH' sworde ndaaro mgemakke ­ lijker rondeoge ne nminde rscheure ngevorm d danbi jhoger e of lagerepH . Dit proefschrift. 7. Detoenam eva nd evervormin g bijbreu k met toenemende vervormingssnelheid, zoalso.a .gevonde ndoo r Ross-Murphy en doorDickinso n enGoulding , zouverklaar d kunnenworde n doordatbreu kme tee neindig esnelhei d voortschrijdt. Dickinson. E.. Colliding. I.e.. J. Text. Stud.. 11 (1980) 51-63 Ross-Murphy, S.B.. In: Biophysical methods in food research, ed. H.w-S. Chan (1984) 8. Hetontbreke nva nee nalgemee nt egebruike nonderzoeksvoor - schriftbi jhe tCOST-9 0projek t 'Reologieva n kaas', veroorzaakt date rallee n zeervoo rd ehan d liggende informatie uitverkrege nka nworden . Masi. P. In: Physical properties of foods-2. eds. R. Jowitt et al. (19B7) Het zounutti g zijno md eomstandighede n inmodel-experimen ­ tenwaari nd evormin gva nlysinoalanin e bestudeerdwordt , meeroveree nt elate nkome nme tdi eva n levensmiddelen. 10. Het isnie tnoodzakelij k datbacteriecelle nvolledi g gelyseerd zijn,wille nhu nintracellulair eenzyme ni nee n substraatkunne nwerken . 11. Het feitda tchocolademel k beschouwd kanworde n alsee n vastesto fe nkaa sal see nvloeistof ,hoef the tgenoege ni n hetconsumere nerva nnie tt ebederven . 12. Bijd ebestuderin gva nmacroscopisch e materiaaleigenschappen zouhe t zeer zinvolzij nmee r aandachtt ebestede naa n onregelmatigheden ind estruktuu r groterda nmoleculair e schaal. 13. Hetgebrui kva na-calorisch evetvervanger s invoedse l lost heteigenlijk eprobleem ,he tt evee le nt eve teten ,nie t noodzakelijkerwijzeop .Di tproblee m ismee rva npsycholo ­ gischeda nva n levensmiddelentechnologische aard. 14. Gelukkig voord eNederlands eeconomi eheef td etoevoegin g 'manager'aa nee nfunktiebeschrijvin gnie taltij doo kee n inhoudelijkebetekenis . proefschrift vanHannemiek eLuyte n Therheologica l and fracturepropertie so fGoud acheese . Wageningen, 10me i1988 . ABSTRACT Luyten, H. (1988), 'The rheological and fracture properties of Gouda cheese.' Ph.D. thesis, Laboratory of Dairying and Food Physics, Department of Food Science, Wageningen Agricultural University (223pp ,Englis han dDutc h summaries). key-words: rheology, fracture, fracture mechanics, consistency, visco-elasticity,Goud acheese ,composition ,maturation ,ey efor ­ mation. The rheological and fracture behaviour of Gouda cheese was stu­ died. Methods for determining these properties of visco-elastic materials are described. Application of the theory of fracture mechanics, after modification and expansion, to visco-elastic materials with a low or no yield stress is discussed. For such materials, of which Gouda cheese is an example, the flow proper­ tiesgreatl y affect the fracturebehaviour . From theeffec to fvariatio n incompositio n (fat,water ,NaC lan d Ca content,pH )an d maturation on the behaviour of Goudacheese , itma y be concluded that this cheesema y be considered as acom ­ posite material. Fat particles act as a filler in a swollen pro­ tein matrix. The amount of fat and the rigidity of the fatpar ­ ticles affect the rigidity of the cheese. Factors like pH, water and NaCl content, that change the properties of the protein matrix, clearly affect the rheological and fracture behaviour, e.g. the rigidity and the shortness, of the cheese. The trends of these changes on the protein matrix are similar to those on rennet and acid skimmilkgel sunde rvariou sconditions . As an example of the importance of the experimental results for cheese manufacturing, the relation between the pH of cheese and eyeo r slit formationwa s studied. CONTENTS page 1. INTRODUCTION 1 2.METHOD S FORDESCRIBIN G RHEOLOGICALAN D FRACTURE PROPERTIES OFVISCO-ELASTI CMATERIAL S 5 2.1 Introduction 6 2.1.1 Deformation of amaterial ;stres san d strain 6 2.1.2 Fracture 8 2.2 Materials and Theologicalmethod s 10 2.2.1 Preparation ofchees e samples 10 2.2.2 Rheological apparatus 12 2.3 Methods formeasurin g rheological and fracture propertieso fchees e 14 2.3.1 Uniaxial compression 14 2.3.1.1 Influenceo f sample sizean d shape 20 2.3.1.2Th e fracturemod e 24 2.3.1.3Effec t of friction 30 2.3.1.4Cree pmeasurement s incompressio n 35 2.3.1.5Conclusion s 36 2.3.2 Tension 37 2.3.2.1Specime n shape 38 2.3.2.2Stres s and straincalculation s 39 2.3.2.3Executio no fth emetho d 41 2.3.2.4Cree pmeasurement s intensio n 41 2.3.3 Bending 42 2.3.3.1Stres s and straincalculation s 42 2.3.3.2Executio no fth emetho d 45 2.3.4 Shear 46 2.3.4.1Calculatio no f stress,strai nan d moduli 46 2.3.4.2Executio no fth emetho d 50 2.4 Comparison of thedifferen t rheological and fracture measurements 51 2.4.1 Comparison ofcompression ,tensio n and bending tests 52 2.4.1.1Th eYoun gmodulu s incompressio n and in tension 53 2.4.1.2Th estress-strai n curve 55 2.4.1.3Fractur e stressan d strain 59 2.4.1.4Elongationa l viscosity 63 2.4.2 Comparison ofcompressio n and shearexperiment s 64 2.4.2.1Th emodulu s incompressio n and in shear 65 2.4.2.2Th eapparen t viscosity incompressio n and inshea r 67 2.5Evaluatio no fth emethod suse d 69 2.6Summar y 70 VISCO-ELASTICAN D FRACTURE PROPERTIES OFGOUD A CHEESE 71 3.1 Fractureo fvisco-elasti cmaterials ,theoretica l considerations 71 3.1.1 LEFM 72 3.1.2 Visco-elastic behaviour 80 3.1.3 Influence of flowo n fracture 82 3.2 Resultsan d discussion 85 3.2.1 The influenceo f thestrai n rateo nth e rheological behaviour 85 3.2.2 Theinfluenc e of thestrai n rateo nth e fracture properties 91 3.2.3 Notch-sensitivity and fracture initiation 95 3.2.4 Fracture energy 99 INFLUENCE OFCOMPOSITIONA L FACTORSO NTH ERHEOLOGICA L AND FRACTURE BEHAVIOUR OFGOUD ACHEES E 109 4.1 Introduction 109 4.1.1 General approach 109 4.1.2 Influenceo fcompositio n 110 4.2 Materials andmethod s 113 4.2.1 Cheesemakin g fromnatura l milk 113 4.2.2 Recombined and filled cheesemil k 114 4.2.3 Changing thecompositio n of test-pieceso f cheese 115 4.3 Influence ofwate r and fatconten t 117 4.3.1 Compositematerial san d application toGoud a cheese 117 4.3.2 Influence ofwate rconten t 122 4.3.3 Influenceo f fat 126 4.3.3.1Influenc eo f fato nth erigidit y and firmness 127 4.3.3.2Influenc eo f fato n fracturebehaviou r 140 4.4 Influenceo f pH,calciu m and sodiumchlorid e 146 4.4.1 pH 147 4.4.2 Calcium 154 4.4.3 NaCl 155 4.5 General discussion and summary 158 INFLUENCEO FMATURATIO N ONTH ERHEOLOGICA LAN D FRACTURE PROPERTIES OFGOUD A CHEESE 165 5.1 Introduction 165 5.2 Materials andmethod s 166 5.3 Fusiono f curd particles 166 5.3.1 Introduction 166 5.3.2 Resultsan d discussion 167 5.4 Influence ofmaturatio n 176 5.5 Influence ofprotei n breakdown 179 5.5.1 Introduction 179 5.5.2 Results anddiscussio n 182 GENERALDISCUSSIO N 191 6.1 Therheologica l and fracturebehaviou r ofGoud a cheese 191 6.2 Comparison between thebehaviou r ofchees e and ofmil k gels 194 6.3 Application of several resultso f thisstud y 197 6.3.1 Application of fracture and flowbehaviou r of cheese toey ean d slit formation 200 6.3.1.1Introductio n 200 6.3.1.2Method s 201 6.3.2.3Result san ddiscussio n 202 LITERATURE REFERENCES 206 LISTO FSYMBOL S 213 SUMMARY 215 SAMENVATTING 218 CURRICULUM VITAE 221 NAWOORD 223 1. INTRODUCTION Besides taste, consistency is an essential quality mark of cheese. In this context consistency means the resistance of a material to permanent as well as recoverable deformation. The consistency of cheese does not only influence eatingproperties , but also the behaviour of cheese during handling, cutting, curd fusion,hol eformatio netc .Thes epropertie sconcer nth ebehaviou r of the material during deformation and breaking, that are the rheological and fracture properties under different conditions and time scales. During eating, for example, cheese is quickly deformed until it fractures; the time scale of this deformation is less than a second. During hole formation, on theothe r hand, the cheese mass is slowly stretched around the growing hole; it must flowan dma yno tfracture .Th etim escal eo fthi sdeformatio n is of the order of magnitude of a week.