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THE RHEOLOGY OF BUTTER

A thesis presented

in partial fulfillment of the

requirements for the degree

of Doctor of Philosophy

in Food Technology

at

Massey Pniversity.

Michelle Harnett

1989.

i i

Abstract.

A para l l e l p l at e vi s co e l a s t omet e r was b ui lt t o per form creep

c o mp l i ance t e s t s on b utter and re l ated fat s . C reep movement

w a s mea s ured with a l inear di spl acement t rans d ucer and

r e c o rded by a data l ogger de s i gned and b ui l t f o r c reep

c o mp l i ance expe r iment at i on .

A t emperat ure o f 1 0 °C was ma intained by p l acing the para l l e l

p l at e vis c o e l as t omet e r in a re f rigerated incubat o r .

A s e r i e s o f pre l iminary expe r i ment s e s t ab l i shed the creep

r e sponse was l inear and that t he direct i o n in wh i ch some

s amp l e s we re sheared was cri t i cal . The d urat i on o f creep

c o mp l i ance t e st ing was a l s o fo und to a f fect r e s ul t s .

C reep behavi o ur o f b utter wa s a s s umed t o be v i s co e l a st i c

( based o n p revi o us st udies ) and was mode l led with a

genera l i z ed Ke lvin mode l . El a s t i c and v i s co us parameters were

f itted to the dat a by a Marquadt non- l i near l e a s t squares

c urve algor ithm . Cont inuo us ret ardat i o n spect r a we re found by

p l ott ing L(�) against ln t ime . Data whi ch had been both

s moothed and di f fe rent i ated by the met ho ds of S av i t z ky and

G o l a y (1964) showed evidence o f the e xi st ence o f three or fou�

m a in group s o f ret ardat i on mechan i sms .

O n remova l o f stre s s a fter creep comp l i ance t e s t ing a part i a l

r e c ove ry o f st rain w a s observed, howeve r , s amp l e s fai l ed t o

r ecove r a s m uch a s p redi cted b y v i s co e l a s t i c t h e o r y . A second

c reep / recovery cycle re s ulted in a respons e s s im i l ar in

magn i t ude to the f i r s t recove r y . All fat produ c t s tested

s h owed the s ame pat t e rn of response o n repeated creep / recove ry

c y c l ing .

An expl anat ion , bas e d on the behavi o r o f p o l yme r s , was put

f o rward t o exp l a i n t he obs e rved pat t e rn o f respon s e . The

i ii

c r y s t a l network was tho ught t o a l i gn in the direct i on in whi ch

s t r e s s was app l ied . The format i o n o f new ' bonds ' was t hen

tho ught to l ock the network in i t s ' new p o s i t i on .

A n umbe r o f s amp l e s were rewor ke d , The c reep c urve seen on

creep/ re cove ry cyc l ing o f reworked samp l e s was s im i l a r in

s hape to t h at s een for t he o ri g i n a l s amp l e s . Howeve r , the

c urve s were t hree to fo ur t imes great e r than tho s e s een for

t he original s amp l e s . I n gen e ra l , creep re sponse wa s f o und t o

b e inve r s e l y proport i onal t o hardne s s .

The ret ardat i on spect ra o f reworked samp l e s di f fered from

t h o s e seen for the o r i ginal s amp l e s in s everal way s . The

spect ra wer e smoothe r , the b ul k o f the spectra had moved t o

short e r t ime s and t he y were l a rger than those seen for the

o r i ginal s ampl e s .

A s urvey o f s e a s on a l b utter s amp l e s was a l s o unde rt aken . C reep

comp l i ance paramet e r s were fo und t o corre l ate we l l with

s e ct i l it y hardne s s and s o l id . fat c ontent .

•

i v

Aim of Study.

The a ims o f t h i s work a r e :

a ) T o s t udy t h e rhe o l og i ca l prope rt i e s o f but t e r a n d re lated

fat product s by a creep comp l i ance method .

b ) T o gain a c l earer unde r s t anding o f the re l at i onship between

rhe o l ogical propert ies , comp o s i t i on and s t r uct ure o f b utter

and r e l ated product s .

c ) T o us e thi s knowledge t o improve the rhe o l o g i c a l properties

of b ut t e r .

V

Acknowledgments.

I am indebt ed t o my s upervi s o r s D r . M . W . T ay l o r , Dr . J. LeLievre , D r . R . Lambert and D r . R . Norr i s , who s e advice and

s upport wa s grat e fu l l y rece ived . I am a l s o i ndebt ed to the New

Z e a l and D a i r y Re search I n s t i t ute who funded t he pro j ect in the

form o f a re se arch contract . In addi t i on I wou l d l i ke to thank

A l a s t a i r MacGibbon , Trevor B i s s e l l and othe r membe rs o f the

Mi l k fat S ect i on , New Z e a l and D a i r y Re se arch I nst itute for

t he i r ide a s and d i s cu s s i on . Inva luable techn i ca l a s s i st ance

was rende red by t he t echn i c a l s t a f f of the Food Techn o l ogy

D epartment , Mas s e y Unive r s i t y and by the Da i ry Products

D eve l opment Cent re s t a f f , New Z e a l and D a i ry Re s e a rch

I n s t i t ute . F i na l l y , thanks to TD for moving to Pa lme rs to n

North.

List of Contents.

ABS TRACT . i i

A IM . iv

ACKNOWLEDGE MENTS . v

C HAPTER ONE : AN INTRODUCT ION IN THREE PARTS .

P a rt A : Rhe o l ogy .

lA . l. Int roduct ion .

1 A . 2 . S t re s s and s t rain .

1A . 3 . S o l i ds , l i qu ids , p l a st i c s .

1A . 4 . V i s c oe l a st i c s .

1A . 5 . Me chan i ca l mode l l i ng .

1A . 6 . Fundament a l t e st ing .

1A . 6 . 1 . Stat i c t e st ing .

1A . 6 . 2 . Dynam i c test ing:

1A . 7 . Emp i r i c a l t e s t ing .

P a rt B : Me asu rement o f the rhe o l og i c a l paramet e r s o f but t e r

1

1

1

1

2

7

7

10

10

19

2 2

and margarine . 23

l B . l . Int roduct i on . 2 3

1B . 2 . Fundament a l t echn i que s . 2 3

1 B . 2 . 1 . Creep comp l i ance . 2 3

1 B . 2 . 2 . Cont i nuous she a r .

1 B . 2 . 3 . Dynam i c t e s t ing .

1 B . 3 . Emp i r i c a l and imitat ive t e s t ing .

1 B . 3 . 1 . Sect i l it y ha rdne s s .

1 B . 3 . 2 . E xt ru s i on .

1 B . 3 . 3 . Compre s s ion .

1 B . 3 . 4 . Pene t r omet ry .

1 B . 3 . 5 . Spreadab i l it y s i mu l at i on .

P art C : But t e r and margar ine .

lC . l . I n t roduct i on .

1 C . 2 . Butter

34

3 7

4 1

4 1

4 3

4 5

4 7

5 0

5 1

5 1

5 1

1 C . 2 . 1 . Manu f acture .

1 C . 2 . 2 . S t rut ure .

1 C . 2 . 3 . F act o rs af fect ing rhe ol ogy .

1 C . 3 . Margarine

1 C . 3 . 1 . Man u f acture .

1 C . 3 . 2 . S t ruture .

1 C . 3 . 3 . F act o rs af fect ing rheology .

1 C . 4 . Ammi x but t e r .

1 C . 4 . 1 . Man u f acture .

1 C . 4 . 2 . S t ruture .

1 C . 4 . 3 . F act o rs af fect ing rheo l ogy .

1 C . 5 . A ft e rward .

C HAP TER TWO : MATERIALS .

2 . 1 . But t e r f rom comme rc i al dai ry fact o ri e s .

2 . 1 . 1 . Comme rc i al s amp l e i dent i ficat i on .

5 1

5 4

5 5

6 2

6 2

6 6

6 7

7 2

7 3

7 3

7 5

7 8

7 9

7 9

7 9

2 . 2 . B ut t e r made u s ing di f fe rent c ream cool ing techn iques . 7 9

2 . 3 . Butt e r and anhydrous product s made f rom the s ame fat . 8 0

2 . 4 . Rewo rk ing . 8 3

2 . 5 . S t o rage . 8 4

C HAP TER T HREE : E S TABL I S HED MET HOD S .

3 . 1 . E xt ract i o n o f mi l k f at .

3 . 2 . S e ct i l it y h ardness .

3 . 3 . F at t y ac i d c ompo s it ion .

3 . 4 . T ri g l y c e ri de compo s it ion .

8 5

8 5

8 5

8 6

8 8

3 . 5 . S o l i d f at content by nuc l e ar magnet i c re s o n ance . 8 8

3 . 6 . S o l id f at cont ent by di f fe rent i al s c anning c al o rimet ry . 8 9

3 . 7 . Compari s on o f nuc l e ar magnet i c re s o n ance and di f f e rent i al

s c an n i ng c al o rimet ry .

C HAP TER FOUR : CREEP CO MP L I ANCE MET HOD .

4 . 1 . The i n s t rument .

4 . 2 . Temp e rat u re ' cont ro l .

4 . 3 . The dat a c o l l e ct i on s y stem .

4 . 4 . S amp l e p rep arat i on , l o ading and runn i ng .

4 . 5 . Rec ove ry and l o ad cyc l i ng .

4 . 6 . D at a an al y s i s .

9 0

9 2

9 2

9 4

9 6

10 0

10 3

1 0 3

4 . 6 . 1 . Creep curve s . 10 3

4 . 6 . 2 . Re coverey . 114

4 . 6 . 3 . P resent at i on o f re s u l t s . 1 1 4

4 . 6 . 4 . Retardat i o n spect r a . 117 4 . 7 . P re l iminary exper iment s . 12 9

4 . 7 . 1 . L inearit y . 12 9

4 . 7 . 2 . Orientat i o n . 12 3

4 . 7 . 3 . Repe at ab i l i t y . 141

C HAP T ER F IVE: LARG E D EFORMAT ION T EST ING. 149

5 . 1 . I nt roduct i on . 149

5 . 2 . Expe r iment a l method . 15 2

5 . 3 . Expe riment a l and result s . 15 3

5 . 4 . D i s cus s i on . 16 3

5 . 5 . Conclu s i on . 17 2

5 . 6 . Tradit i onal s e ct i l it y ha rdne s s t e s ti n g vs . l a rge

de f o rmat ion t e s t ing . 17 2

C HAP T ER S I X : AN INTROD UCT I ON TO CREEP CO MP L IANC E

EXP ER I MENTAT I ON .

P a rt A

6A . 1. Exper iment a l .

6A . 2 . Re su l t s .

6A . 3 . D i s cu s s ion .

P a rt B : But t e r s manu factured u s i n g di fferent cream coo l ing

t e chn i ques .

6B . l . Expe riment a l .

6B . 2 . Re sult s .

6B . 3 . D i s cu s s i on .

C HAP T ER S EVEN : T HEORY .

7 . 1. Int roduct ion .

7 . 2 . Load c y c l ing .

7 . 2 . 1 . Expe riment a l .

7 . 2 . 2 . Re s u l t s .

7 . 2 . 3 . D i s cu s s i on .

7 . 3 . Rework i n g .

17 4

1 7 ·4

17 4

17 4

17 6

17 8

17 8

17 8

17 9

18 1

18 1

18 1

18 1

18 1

19 1

19 4

7 . 3 . 1 . Experiment a l . 1 9 4

7 . 3 . 2 . Re sult s . 1 9 4

7 . 3 . 3 . D i s cu s s i on . 2 0 4

7 . 4 . Deve l opment o f a theory t o e xpl a in ob s e rved behavi our . 2 0 6

7 . 4 . 1 . I ntroductory comment s . 2 0 6

7 . 4 . 2 . Theory A . 2 0 6

7 . 4 . 3 . Theory B . 2 0 8

Chapt e r E i ght : But t e r and Anhydrous P roduct s made from the

S ame F at . 2 1 3

8 . 1 . I nt rodu ct i on . 2 1 3

8 . 2 . Expe r iment al . 2 1 3

8 . 3 . Re s u lt s . 2 1 4

8 . 3 . 1 . Sect i l it y hardne s s and sol id fat cont ent . 2 1 4

8 . 3 . 2 . Creep comp l i ance . 2 2 9

8 . 4 . D i s c u s s ion . 2 3 5

8 . 4 . 1 . Compo s i t i on 2 3 5

8 . 4 . 2 . Reworking . 2 4 2

C HAP TER N I NE : SEAS ONAL TREND S I N FRI T Z AND AMMI X BUTTER . 2 4 5

P art A : E s t ab l i shed methods . 2 45

9A . 1 . I nt roduct i on . 2 4 5

9A . 2 . Experiment a l . 2 4 5

9A . 3 . Re s u l t s and di s cu s s i on . 2 46

9A . 3 . 1 . Sect i l it y hardne s s . 2 4 6

9A . 3 . 2 . S o l i d fat content . 2 46

9A . 3 . 3 . Compar i s on between sect i l i t y hardne s s and s o l i d

fat cont ent . 2 5 1

9A . 3 . 4 . D i f fe rent i a l s canning ca l o r imet ry . 2 5 5

9A . 3 . 5 . Fatty a c i d compo s it i on . 2 5 6

9A . 3 . 6 . Triglyceride c ompo s i t i ion . 2 6 1

9A . 4 . Conclu s i on .

P art B : C reep compl i ance .

9 B . 1 . Exp e rimenta l .

9 B . 2 . Re s u lt s .

9 B . 3 . D i s cu s s ion .

9 B . 4 . Con c l u s i on .

2 6 4

2 6 5

2 6 5

2 6 5

2 7 1

2 7 2

CHAP TER TEN : GENERAL D I S CUS S ION .

1 0 . 1 . D eve l opement o f the c reep comp l i ance method .

1 0 . 1. 1. Equ ipment .

10 . 1. 2 . Data C o l l e ct i on .

10 . 1 . 3 . Tempe rature Contro l .

1 0 . 1 . 4 . Accuracy .

1 0 . 2 . D at a ana l y s i s .

10 . 2 . 1. The V i s c oe l a s t i c Mode l .

10 . 2 . 2 Dat a Ana l y s i s .

10 . 2 . 3 . Ret a rdat ion Spectra .

10 . 2 . 4 . Approp r i atene s s o f the Mode l .

1 0 . 3 . P re l iminary Exper iment s .

10 . 3 . 1. L i n e a r i t y .

1 0 . 3 . 2 . Durat ion o f E xper iment .

10 . 3 . 3 . Orient a t i on o f Sample .

10 . 4 . Load Cyc l i ng .

1 0 . 5 . P roduct s made from t he same fat .

1 0 . 6 Rewo rked pr oduct s .

10 . 7 . Seasonal s u rvey .

1 0 . 8 . Conc l u s i on and future work .

APP END I X 1: Computer P rograms .

2 7 4

2 7 4

2 7 4

2 7 4

2 7 5

2 7 5

2 7 6

2 7 6

2 7 7

2 7 8

2 7 8

2 7 9

2 7 9

2 8 0

2 8 2

2 8 4

2 8 9

2 9 0

2 9 1

2 9 3

2 9 6

APP END I X 2 : Non- l inear Lea s t Square s Cu rve F i t t ing Re s u lt s . 3 13

APPEND I X 3 : D i f fe rent i a l S cann ing C a l o r imetry Me l t i ng

The rmograms , 19 8 5 - 19 8 6 S e ason .

REFERENCE S .

3 42

3 5 6

List of Tables.

Table 1 . 1 : Creep r e s u l t s report ed by var ious worker s . 2 6

Table 1 . 2 : Re sults repor t ed b y D a v i s ( 1 9 73 ) us ing a var iety o f r heological met hods . 2 9

Table 1 .3 : Compar i s on o f the results repor ted by S hama and S herman ( 1 9 7 0 ) and Gupta a nd D eMan ( 1 9 8 5 ) . 3 1

Table 2 . 1 . Pr oduct ion conditions used i n the manufacture o f butt er and anhydr ou s pr oduct s from the s an e milk fa t . 8 2

Table 2 . 2: Product temper atur e s recorded dur ing pr oduct ion of butter and a nhydr o u s pr oduc t s from the same milk fa t . 8 2

Table 3 . 1 : Compo s i t i on o f standard a� hydr ous mi lk fa t . 8 7

Table 3 . 2: Norma l iz ing factor s f or fat t y acid we ight per centage s , relat ive to c 16 : o· 8 7

Table 4 . 1: The e f fect o f varyi�g the n umb er of exponent i a l terms used i n f it t ing dat a to the pr e f i ned mode l . (Sample TUI A ugu st ' 86 , 1 0°C . ) 1 1 0

Table 4 . 2 : P arameter s f itted t o cr eep c ompl iance dat a by two met hods , e xponen t i a l pee l ing and non-l inear c�rve f itt ing . 1 13

Table 4 . 3 : A compar i s on o f retardat ion t imes calculated by a lea s t sq uares c ur ve f i t t ing pr ogr am ( NONLIN ) and tak en from conti nuous r e t arda t ion s pectr a, F igures 4 . 2 0 and 4 . 2 2 . 1 2 8

Table 4 . 4: S tr a in r e sponses observed o n the applicat ion o f s tr e s s . 13 1

Table 4 . 5 : Cr eep compl iance par ameter s f ound for one s ample on t he app licat ion o f dif fer ent str e s s e s . 13 1

Table 4 . 6 : Cr eep compl iance parameter s obt a ined fr om patted Fr itz butt er s s he ar e d i n t he thr ee poss ible direction s . 13 4

Table 4 . 7 : Recover y dat a f or the butter TUI Apr i l ' 8 7 . 13 6

Table 4 . 8: Cr eep compliance par ameter s obt a ined from patted Fr itz butter s sheared i n two direct ions . 13 6

Table 4 . 9 : Cr eep compl iance par ametr s obta ined from unpatted Fr i tz but ter s sheared i n two dir ect ions . 13 8

Table 4 . 1 0 : Cr eep compliance par ameter s fitted t o cr eep curves observed for t he butter TT January , 1 9 8 6 . 1 4 4

Table 4 . 1 1: Creep c ompl iance par ameter s f itted t o cr eep curve s observed for t he butter TT Apr i l , 1 9 8 6 . 1 4 7

Table 5 . 1 : P er centage solid fat determined by NMR and tr adit ional sect i l ity h ardrie s s values a t 1 0°C for butt er s used in large de f orma t ion t e s t ing . 1 5 4

Table 5 . 2 : An e xample o f dat a reco rded by the Perkin E lme r dat a s ta t io n dur i ng la rge de fo rmation tes t ing . 16 1

Table 5 . 3 : Comparison o f sectility hardness tes t ing ( t radi t io n a l ) with s he a r t es t ing .

Table 5 . 4: Sect i lity hardness results ( C R Analys e r ) .

16 4

16 4

Table 5 . 5: The fit o f v a r io us models to shear speed vs . fo rce data fo und at 5 , 1 0 a nd 1 5° C fo r four s amples express ed as co rre lat io n coe f f i c ients . 16 9

Table 6 . 1 : Rheo logical pa rameters fo und fo r creep and reco v ery experiments o f d i f fe ring length . 1 7 5

Table 6 . 2 : Sect i lity hardness v a lues a t 1 0°C fo und fo r but t e rs manufactured f ro m c ream s ub j ected to di f fe rent c re am coo l ing techniques . 1 8 0

Tab l e 6 . 3 : C reep compl iance pa ramete rs f itted to t he c reep res ponse o f but t e rs manufactured from c ream s ub j ected to di f fe rent c ream coo l ing techniq ues . 1 8 0

Table 7 . 1 : Sect i l ity ha rdness es and so l id fat co ntents o f s e lected det e rmined at 1 0° C . 1 83

Table 7 . 2 : C reep compl iance parameters fo r s amp les co l lected t h roughout the yea r . 1 8 7

Table 7 . 3 : Ov erall creep respo ns e d isp layed by s amples co l lected thro ughout t he yea r . 1 8 8

Table 7 . 4 : Co r relat ion co e f f ic ients fo und between v a r io us c reep compliance pa rame t e rs and sect i lity ha rdness fo r s amples o f butte r co llected t h ro ughout t he yea r . 1 8 9

Table 7 . 5: Creep compliance pa rameters f itted to o riginal and rewo rked but t e r pa i rs . 1 9 5

Table 7 . 6: P e rcent age changes s een i n creep respo nse o n t he rewo rking o f but t e r s amp les . 1 9 7

Table 7 . 7 : Pecent age change fo und i n s elect ed pa ramet e rs o n compa ring f i rs t and seco nd c reep respo ns es . 1 9 7

Table 7 . 8: Ret a rdation t imes found fo r o rigianl and rewo rked butters . 2 0 3

Table 8 . 1: S e c t i lity hardness res u l ts , 1 0°C . 2 1 5

Table 8 . 2 : So l id fat contents as det e rmined by NMR . 2 1 5

Table 8 . 3 Creep compliance parame t e rs fo r o r igina l and rewo rked s amples o f but t e r , plas t i c ized milkfat and a mi lkfat/o i l blend manufactured f rom t he s ame fat so urce . 2 2 0

Table 8 . 4: Co r relat ion coe ff i c ients found between v a r io us c reep comp l iance pa r amet e rs and sect ility h a rdness' fo r o rigina l and rewo rked butters ,

plast ic ized milk f at and milk fat/ o i l blend m anufact u red f rom th e s ame f at . 2 2 1

Table 8 . 5 : Pe rcent age ch anges seen i n various param eters go ing f rom o r iginal t o rewo rk ed .

Table 8 . 6 : Comparison o f second c reep response with the f i r st c reep response .

23 1

233

Table 9 . 1 : The sect i l ity h a rdness o f s amples o f patted butte r det e rmined at 1 0° C . 2 4 7

Table 9 . 2: Pe rcentage solid fat a s det ermined by NMR for s amples o f milk fat ext racted f rom F r itz butt e r . 2 4 9

Table 9 . 3: P e rcent age solid fat a s det e rmined b y NMR for s amples o f milk fat ext racted f rom �� ix butt e r . 2 5 0

Table 9 . 4 : Fatt y acid composit ion o f F ritz b utt e r s col lect ed dur ing the 1 9 8 5 - 1 9 8 6 season . 2 57

Table 9 . 5 : Fatt y acid compos s iton o f Amm ix butt e r s collect ed du ring th e 1 9 8 5 - 1 9 8 6 season . 2 5 8

Tab le 9 . 6 : Trigly ce ride com po s it ion o f F r itz b utt e rs collected du ring th e 1 9 8 5 - 1 9 8 6 season . 2 6 2

Table 9 . 7 : Triglycer ide compo sit ion of Amm ix butt e rs colle cted during th e 1 9 8 5 - 1 9 8 6 season . 2 63

Table 9 . 8 : Creep com pl iance paramet e rs f itted t o butters . 2 67

Table 9 . 9: Co rrelat ion coe f f ic ient s found between sect i l it y h a rdne s s a nd s o l id f at content and c reep compl iance paramet e rs for a numbe r o f b utt e rs .

2 6 9 Table 9 . 1 0 : C reep compliance par amet e r s f o r samples collect ed th rough out the yea r . 2 7 0

List of Figures.

F igure 1 . 1: Rate o f sh ea r vs . sh ear for a Bingh am plast i c . 6

Figu re 1 . 2: Standa rd rh eological m ode ls : a) Hookean sprin g , b) Newton ian da shpot , c ) St Ven ant glide r . 8

F i gure 1 . 3: Rh eological m odel s: a) B ingh am plast i c , b ) Max wel l un it , c) Kelvin un it and d) , Burgers m ode l . 9

F i gu re 1 . 4: Typic a l c reep an d recove ry curve for a plast ic f at . 1 3

Figure 1 . 5 : A m ode l c reep cu rve . 1 4

F igure 1 . 6: The generalized Kelvin m odel . 16

Figu re 1 . 7: St re s s re spon s e t o s in uso ida l st rain . 2 1

Figure 1 . 8: Creep parameters repo rted by G upt a an d D eMan ( 1 9 8 5 ) plotted again st force used . 3 3

Figure 1 . 9: Th e m odif ied Bin gh am body . 36

Figu re 1 . 1 0: a) Th e Vis cous -Max we l l -Bingh am mode l (D e in e r and He ldman, 1 9 86) , b) st uctural applicat i on of the m ode l . 3 9

Figure 1 . 1 1: Th e P a s i lac HCT 2 cont in uous butterm aker . 5 3

Figure 1 . 1 2: D i f f e rent ial scann ing calorim et ry m e lt in g th e rm ogram o f a F r itz butter . 5 7

Figure 1 . 1 3: D iagram of a sect ion th rough a sc raped s u rface heat exchange r . 6 4

Figure 1 . 1 4: Cont in uous soft m a rga rine p roduct ion ( E r i ks on, 1 9 8 5) . 6 5

F igure 1 . 1 5: D i f f e rent i a l s cann in g calorim et ry m e lt in g th e rm ogram o f a t ab le m a rgarine . 6 9

Figure 1 . 16: Th e Amm ix proce s s . 7 4

F igure 1 . 1 7: D i f f e rent i a l scann ing calorim et ry m e lt in g the rm ogram of an Amm ix b utte r. 7 7

F igure 2 . 1: P lant con f igurat i on used in the m an u fa ct u re o f butt e r an d anhydrous product s f rom t he smae f at . 8 1

F igure 4 . 1: The pa rallel p l at e viscoelast ometer . 9 3

F igure 4 . 2 : Diffe rent ial s c ann ing calorim et ry m e lt ing therm ogram i l lust rat in g the c hanges in s o l id fat content with tem pe r ature at 1 0 and 1 5oC . 9 5

F i gu re 4 . 3 : Fluct u at i on in tem pe rat ure obse rved ove r � f o rt y hour period . 9 7

F igure 4 . 4: D at a collect ion syst em . 9 8

F igure 4 . 5: Ch a rt recorde r t race seen on pe rforming a c reep compl iance expe r iment . 9 9

F igure 4 .6: P lan and s ide views o f th e s ample cutt e r . 1 0 1

F igure 4 . 7: A c reep and recove ry curve . 1 0 4

F igure 4 . 8 : A c reep compl iance curve sh owing ext rapo l at ion back t o 0 t ime . 1 06

F igu re 4 . 9: Ln Q plotted aga inst t ime sh owing th e st r a ight l ine port ion of th e graph ext rapo lated to 0 . 1 0 8

F igure 4 . 1 0 : Creep and recove ry curve s sh owing inst a nt aneous comp l iance, th e s um o f comp l i ances recovered and th e un recovered st r a i n . 1 1 5

F igure 4 . 1 1: Re sult presentat ion b y th e curve f itt ing p rogram NONLIN . 1 16

F igure 4 . 12 : An ideal cont inuous ret a rdat ion spect rum c a lculated for the s ample MAN May 1 9 8 7 . 1 1 9

F igure 4 . 13 : Ret a rdat ion spect rum found f o r the sample MAN May 1 9 8 7 us ing raw dat a . 1 2 0

Figure 4 . 1 4 : Cont inuous reta rdat ion spect rum found f o r MAN May 1 9 8 7 a fter smooth ing raw dat a . 122

F igure 4 . 1 5 : Th e ideal cont inuous ret a rdat ion spect rum found for MAN May 1 9 8 7 a ft e r smooth ing . 122

F igure 4 . 16: Th e cont inuous ret a rdat ion spect rum found f o r MAN May 1 9 8 7 a ft e r different iat ing th e raw dat a . 123

F igure 4 . 1 7: Th e ideal cont inuous ret a rdat ion spect u rm f ound for MAN May 1 9 8 7 a ft e r diffe rent iat ing according t o the meth od o f S az itz ky and Go lay ( 1 96 4) . 123

F igure 4 . 1 8: Th e ideal cont inuous ret a rdat ion specturm f ound for MP� May 1 9 8 7 a ft e r a 13 point cubic different iat ion . 1 2 4

F igure 4 . 1 9 : Th e ideal cont inuous ret a rdat ion specturm f ound for MAN May 1 9 8 7 a ft e r a 7 point qua rt i c different iat ion . 1 2 4

F igure 4 . 2 0 : The cont inuous ret a rdat ion spect u rm found f o r MAN May 1 9 8 7 a ft e r smooth ing and different iat ing according t o the meth od o f S avitz ky and Golay ( 1 96 4) . 1 2 5

F igure 4 . 2 1 : Th e ide a l cont inuous ret a rdat ion specturm found for MAN May 1 9 8 7 a ft e r smooth ing and di f fe rent iat ing according to th e meth od o f Savitz ky a nd G o l a y ( 1 96 4 ) . 1 2 5

F igure 4 . 2 2 : The cont inuous ret a rdat ion spect u rm found f o r MAN Apr i l 1 9 8 7 a ft e r smooth ing and di f fe rent iat ing �ccording t o the meth od o f S avitz ky and Golay . 1 26

F igure 4 . 2 3: The ideal cont in uous ret a rdat ion s pecturm foun d for MAN April 1 9 8 7 a ft e r smoot h ing and di fferent i at in g according to t he method of S avitzk y an d Golay ( 1 9 6 4) . 1 2 6

F igure 4 . 2 4: Th ree dimen s ion a l axes imposed on a pat o f butt e r . 1 3 3

Figure 4 . 2 5: Ope rat ing prin c iples o f t he S ig FD 1 4 0 patt e r . 1 3 9

F igure 4 . 2 6 : Creep compliance curve s foun d f o r t he samp le T T Jan ua ry ' 8 6 . 1 4 3

Figure 4 . 2 7: Creep compl iance curves foun d for the samp le T T Ap ril ' 8 6 . 1 4 5

Figure 5 . 1 : Front an d s ide views o f t he apparat us att ached t o t he c R An a lyser used for shea r test ing . 1 5 1

Figure 5 . 2: Force vs . shear speed f o r t he sample TUI Februa ry 1 9 8 7 . 1 5 5

Figure 5 . 3 : Force vs . s hea r speed f o r t he samp le MAN MAy 1 9 8 7 . 1 56

Figure 5 . 4 : Force vs . shear speed f o r t he sample TT Februa ry 1 9 8 7 . 157

Figure 5 . 5 : Force vs . s hear speed f o r t he s ample TT M a rch 1 9 8 7 . 1 5 8

Figure 5 . 6: Shear fa i lu re st res s plotted aga in st tempe rat ure . 16 0

Figure 5 . 7 : St ress vs . distance moved by the p robe . 16 2

F igure 5 . 8 : Fo rce vs . s hear speed f o r both she a r te st in g an d sect i l it y h a rdness test ing, sample MAN May 1 9 8 7 . 165

Figure 5 . 9: Force vs . s hear speed f o r bot h shea r test ing an d sect i l it y ha rdn e s s test ing, sample T T Ma rch 1 9 8 7 . 166

F igure 7 . 1 : Typical c reep complian ce curve seen on repeat edly applyin g an d removin g st res s . 1 8 4

Figure 7 . 2: Cont in uous reta rdat ion spect ra foun d for the butt e r TUI April 1 9 8 7, a ) f i r st c reep respon se, b ) , s econ d c reep respon se . 1 8 5

Figure 7 . 3: Cont inuous ret ardat ion spect ra foun d for t he butte r T T March 1 9 8 7, a ) f i r st c reep respon se, b ) , secon d c reep respon se . 1 86

F igure 7 . 4: Fi rst and secon d c reep c u rves observed for the but e r TUI Ma rch 1 9 8 7 . 1 9 2

F igu re 7 . 5: Cont inuous reta rdat i on s pect ra foun d for t he butt e r TUI Ma rch 1 9 8 7, a ) f i r st c reep_ re spon se, b ) , secon d c reep respon s e . 1 9 9

F igure 7 . 6: Cont inuous reta rdat ion spect ra foun d for t he butte r T T Feb . 1 9 8 7, a ) f i r st c reep respon se, b ) , s e cond c reep respon se . 2 0 0

F igure 7 . 7: Cont inuous ret a rdat ion spect ra found for t he reworked butter TUI Ma rch 1 9 8 7, a) f i r st c reep respon se, b ) , second c reep respon se . 2 0 1

F igure 7 . 8 : Cont i nuous ret a rdat ion spect ra foun d f o r the rewo rked butt e r TT Feb . 1 9 8 7, a) first c reep response, b) , secon d c reep re sponse . 2 0 2

F igure 8 . la : Di fferent i a l scann ing calorimetry m e lt in g th e rm ogram found for o ri g in a l plast i c ized m i l kfat . 2 16

F i gu re 8 . l a : D i f fe rent i a l scann i ng calorimetry m e lt ing therm ogram found for rewo rked plast ic ized m i l kf at . 2 1 7

F igu re 8 . 2 a : D i f ferent ia l scann ing calorimetry m e lt ing the rmogram found for origin a l m i lkfat/ o i l blend . 2 1 8

Figure 8 . 2b : D i f ferent ia l scann ing calorim etry m elt ing th e rm ogram found for rewo rked m i lkfat/ o i l blend . 2 1 9

Figure 8 . 3 : Cont in uous ret a rdat i on spect ra found for plast ic ized m i lkfat : a) i n it ial creep respon se, b) secon d c reep re spon se . 2 2 3

Figu re 8 . 4 : Cont inuous ret a rdat ion spect ra found for butt e r : a) c reep respon se, b) second c reep respon se .

in it i a l 2 2 4

Figure 8 . 5: Cont in uous ret a rdat ion spect ra found fo r m i lk fat/ o i l bl en d : a) init i a l creep re spon se, b) second c reep re spon se . 2 25

F igure 8 . 6 : Cont in uous ret a rdat ion spect ra found f o r rewo rked plast ic ized m i l k f at: a) init ia l c reep re spon se, b) second creep respon se . 2 26

F igure 8 . 7 : Cont in uous ret a rdat i on spect ra found for reewo rked butt er: a) in it ia l creep respon s e, b) second c reep respon se . 2 2 7

Figure 8 . 8: Cont in uous ret a rdat ion s pect ra found f o r reworked m i lkf at/ o i l blend : a) init ia l c reep response, b) secon d creep respon se . 2 2 8

Figure 9 . 1 : The variat ion o f sect il it y h a rdness w ith season . 2 4 8

Figu re 9 . 2 : Th e variat ion o f pe rcent age s o l id fat with season . 2 5 2

Figure 9 . 3 : Solid f at cont ent plott ed aga i n st sect i l it y h a rdne s s showing l in e s of best f it for all s amples and F r itz and Amm ix butt e r s sepa rate ly .

2 5 3

Figure 9 . 4 : D i f fe rent ial s cann ing calorim et ry melt ing th e rm og ram s found for Oct ober an d December Amm ix butt ers 2 5 5

F igure 9 . 5 : We ight pe recent age s o f c 16: 0 and c 1 8 : l f o r Fritz and Amm ix butt ers col lected ove r th e ' 8 5 - ' 86 season . 2 5 9

F igure 1 0 . 1 : A c reep a nd recove ry curve . 2 8 1

F igure 1 0 . 2 : Typical c reep com p liance cu rve seen on repeatedly applying and rem o ving st re s s . 2 8 5

Figure 1 0 . 3 : P roposed rheological m odel s t o represent th e c reep compliance beh aviour of butt e r . 2 8 8