Electrolyte systems relating to milk : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Chemistry at Massey University

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ELECTROLYTE SYSTEMS RELATING TO M ILK

A the si s p r e s ent ed i n par t ial :fulfi lment of' the req_ui r ement s for the degr e e of' Doc t or of' Phi l o s ophy i n Chemi s t ry at Ma s s ey U niversi ty.

KEV IN NEIL PEARCE

June , 1 97 2

ABSTRACT

A pH t i t rati on me thod using a gla s s el e ct rode

/

saturated calomel el e c t rod e c ell ha s been appli ed to the det ermi nat i on o� a c i di ty and s tab i li t y constant s i n d i lute a �ueou s solut i ons at 2 5 C . 0 Two compu t er

p rograms in FORTRAN hav e been wri t t en and u sed t o cal cula t e the cons tant s from the ti t rati on data .

Acidi t y constant s for the homologous s eri e s of

alipha ti c ^cJ...w di carboxyli c acids (succ i ni c aci d t o s ebac i c

acid inclu si v e) hav e b e en d e t e rmined . Acidi t y c onstant s for tri carballyl i c , c i t ri c and a number of o"!-.her ca rboxyl i c a cid s hav e al so b e en det ermi ned and the valu e s obtai ned are

i n good agre ement wi th value s report ed by other workers. A new s e t of mi cro aci d i t y constant s , differing �rom tho s e

reported by other work e r s, ha s been obtai ned for ci tr i c acid from a pH t i t rati on study of vari ou s methyl e st er s

of c i tri c acid . The s tabi li ty con stant s for the magne s i um and cal cium complexe s of c i t r i c acid have been rede t e rmined .

The me thod of cal culat ing a c i d it y constan t s from

sub s t i tuent e ffe c t s ha s been refi ned t o dj_ s t i ngui sh b e tw e e n mac r o and mi cro a ci d i t y cons tant s and ha s been u s ed w i t h some succ e s s i n t h e predi ct ion o � both mi cro and macro

acidi ty cons tants. Good value s hav e been obtai n ed for the fi r s t and s e cond but not the thi rd a ci d i ty constant s for ci tri c acid u sing thi s t echni�ue. An analogous method for cal culating s tab i l i ty con s tant s from substi tuent effect s ha s been t e s t ed and found promi s i ng but i t s appli ca t i on i s

hamp ered by th e lack of sui table exp er imental dat a.

The thermodynami c ba s i s of th e ca t i on exchange r e si n method of determini ng cat i on acti v i ti e s i n soluti on has b e en d e s cribed and a new m ethod of resin calibrati on u s i ng

two parame ter equati ons dev el oped. The i on e xchange re si n

me thod has been appli ed t o s tudi e s of th e s e a sonal variati on of mi lk c omp o s i t ion and to bri ef s tudi e s of the effe c t s of mi lk pH ad ju stment , th e fac t ors affect ing the renne t i ng t i me of mi lk and the d e t ermi nat i on of cation a c t i vi t i e s i n non bovi ne mi lks.

Some of th e probl em s a s s o ci ated wi th calculat ing cat i on a c t i vi t i e s in milk hav e been bri efl y di scuss ed. I n a

preli minary study of synthet i c wh e y , comp ari sons have b e en made betwe en cat i on a c t ivi ti e s det ermi ned exp er iment a lly and tho s e cal culat ed from a knowl edge of comp o s i ti on and of the relevant acidi t y and s t abi li ty constant s.

I am i nd eb t ed t o the f ollowing:

Dr

L.K.

C r eamer , New Zealand Dairy R e s earch I n s t i tut e ,

for guidance and cont i nui ng interest. Dr R . D . Reeve s , for supervi s ion.

Pr ofe s s or G . N . Malcolm, for supervi si on.

Dr R . C . Lawr ence , New Zealand Dairy Re sear ch I n s t i tut e , for helpful comment s.

Profe s s or W . A . E . M cBryd e , Uni v er si ty of Wat erloo, Ontari o , for h elpful di s cus s i ons and for arranging t h e

comput er pro c e s s ing o f data.

N ew Zea land Dairy Res ear ch I n s t i tut e for employment and the u s e of fa ci l i t i e s duri ng the cour s e o f the work.

TABLE OF C ONTENT S

Cr�TER 1 . GENERAL INTRODUC T I ON

page 1 1 . 1 A De s cript i on of M i lk and S ome of i t s Proper t ies. 1 1 . 2 An I ntroduc t i on t o the P r e s ent Work. 6

PART I ACIDITY AND STABILITY CONSTANT S CHAPTER 2 . INTROD�CT I ON

2 . 1 Defi ni t i ons .

2 . 2 A Bri ef Surv ey o f M ethods Avai l able for

9 9

D e t ermining Aci di ty and S t ab i li ty C ons t an t s. 1 3

2 . 3 The M i cr o Acidi ty C on s t ant s for C i tri c Aci d. 1 4 2 . 4 S t ruc tural Formulae of Acid s Rel at ed to C i tric

Aci d . 1 8

CHAPTER _3. THEORY AND C OMPUTER PROGRAM S 3 . 1 Derivat i on o f General Formulae .

3 . 2 The M ethod of Least Squar e s. 3 . 3 C omputer Programs .

CHAPTER �-. EXPER IMENTAL

4.1 De s crip ti on of Apparatus. 4 . 2 Reagent s.

4 . 3 Exp eri mental Pro c edure . CHAPTER 5. RESULT S

1 9 1 9 24 28

33 33 34 36 3 9

5 . 1 T h e ^{ex w} Di carboxyli c Aci ds . 40

5 . 2 Aci d i ty C on s t ant s for Vari ou s C arb oxyl i c Aci d s. 43 5 . 3 A c i d i t y C on s t an t s for C i tri c Aci d . 43 5 . 4 Aci d i ty C on s t ant s for the M e thyl C i trat e s . 4 5 5 . 5 S t ab i li ty C on s t ant s for Variou s C i trat e Compl ex e s. 49

··�

CHAPTER 6 . D I SCU S S ION 6 . 1 Error .

6 . 2 Int eract i on B etween the Supp ort i ng El e c t rolyte and the Acid Ani on .

6 . 3 The Hydrogen I on Ac tivi ty Co effi cient . 6 . 4 C alculat i on of Acidi ty C ons tant s from the

Sub s t i tuen t Effect.

6 . 5 M i cro Ac idi ty C onstants for C i t ri c Aci d . 6 . 6 C alcula t i on of Stab i li ty C on s t ant� fr om

Sub s t i tuent Effe c t s .

PART I I CAT I ON AC TIV I T IES IN M ILK . M I LK PRODU C'l' S AND OTHER FLU IDS

p age

6 1 6 1

64 67

7 1 7 9

8 3

C HAPTER

7 .

INTRODUCT ION 9 2

CHAPTER 8 . THEORY AND APPLICAT I ON OF THE I ON EXCHANGE RESIN METHOD FOR DETERIHNING CAT ION

ACT IVIT IES 96

8 . 1 General Theory of the I on Exchange R e s i n M e t hod for Det ermi ni ng C at i on Ac tivi t i e s .

8 . 2 Appli c at i on . CHAPTER

C HAPTER 1 0 . EXPERIMENTAL. 1 0 . 1 D e s cripti on of Apparatus. 1 0 . 2 Reagent s .

1 0 . 3 Procedure s . CHAPTER 1 1 . RESULT S

1 1 . 1 The Eff e c t o f T emperature on Re s in C alibr a t i on .

1 1 . 2 The Effect of R e sin B ead S i ze . 1 1 . 3 Elu ti on Kinet i c s .

1 1 . 4 C alibrat i on of the I on Exchange Re s i n .

9 6 9 9

1 0 1 1 08 1 08 1 0 9 1 1 0 1 1 3 1 1 3 1 1 4 . 1 1 5 1 1 5

I .

CHAPTER

1 1

₍C ont i nued)

1 1 a5

C a t ion Ac t i vi t i e s in Bov i ne Raw Ski m M ilk S ea son Trend s ^a

1 1 . 6

The V a ri at i on of C at i on Activ i t i es i n M i lk

:page

1 2 2

w i th Temperature.

1 2 6

1 1 . 7

M i lk :pH and Cal cium I on Activ i t y .

1 29 1 1 . 8

Rennet ing T i m e and C alc ium I on Act i vi t y .

1 2 9 1 1 . 9

C at i on Acti v i t i e s i n Goa t , C ow and She ep Mi lks.

1 31

CHAPTER

1 2 .

DI SCUSSION.

1 2 . 1

Func t i onal Relati onship s and Regr e s s i ons B et ween E�uilibrium Solu t i on C a t ion Activi t i e s and R e s in C ompositi on.

1 2 . 2

Limi ta t i ons of the C at i on Exchange R e s i n M ethod

1 3 6

1 3 6

of D e t ermini ng C a t i on Activi t i e s .

1 39 1 2 . 3

Pre ci s i on and Ac cura cy o:f the C at i on E xchange

R e s i n M ethod for Det e rmining C at i on A ct ivi ti e s.

1 4 2

PAR'r I I I PRED ICTI ON OF CAT ION ACT IV ITIES IN vVI-IEY A.T\fD SYNTHET IC WHEY

CHAPTER

1 3.

THEORET ICAL PRED I CT I ON Mm EXPER IMENTAL DETER11INAT I ON 0? CAT ION ACT IV I T I ES IN

SYNTHET IC WHEY

1 46

1 3 . 1

Ski m M i lk as an E�ui librium Sys t em.

1 4 - 6

1 3 . 2

C al culat i on of C at i on A c t i v i ti e s in Syntheti c

Whey .

1 51

1 3 . 3

Exp e ri ment al Det erminat i on of C a t ion A c t iv i t i e s

i n Synthet i c Whey.

1 51

CHAPTER

1 4 .

SUMMARY A.l'iJD GENERAL CONCLUSIONS.

1 4 . 1

Summary.

1 4 . 2

Sugg e s t i ons for Further Work.

APPEND IX I . Volume of the M i celle Pha s e of M i lk .

1 59

1 59

1 60

1 64

APPENDIX I I . The Kin

e

t i c s of' M e thyl C i trat e S aponi f'i cat i on .

APPE\ID IX I I I . Symb ol s an d U ni t s . REFERENCES

TABLES

page

1 68 1 71 1 72.

1 . 1

T h e C omp o si t ion of Typ i c al Bovine Ski m Milk.

2 1 . 2

Approximat e C ompo s i t i on of' th e Serum and M i celle

Pha s e s of' Typ i c al B ovi ne Skim Milk at

2 0 °C . 4 4 . 1

Approxi mat e Yi eld s o f M e thyl C i trat e s Pr oduc ed

by Saponifi cat i on.

5 . 1

Therm odynami c and C onc entrat i on Ac idi ty C on s t an t s for the ^aw Di carb oxyl i c A ci d s .

3 7

41 5.2

Acidity C onstant s for V ar i ou s C arb oxyli c Acids.

44 5 . 3

Acidi ty C onstant s and S t andard Dev i at i ons for

C i tr i c Aci d as a Fun ct i on of' Aci d C onc entr at i on

i n

0 . 1

mmol

/

l KCl S oluti on .

4 6 5 . 4

C onc entrati on Aci d i ty C on s t ant s for C i tri c

Acid at

I

⁼

0 . 1 .

5 . 5

Aci d i ty C onstant s for the M ethyl Ci trat e s.

5 . 6

A Summary of' V alue s Repor t ed for th e S t ab il i ty C on stant s of' C i tri c A c i d

/

C al cium C omplexe s.

5 . 7

M e t al I on C oncentrat i on s C al cul at ed from C on s t ant s Giv en b y C ampi e t al . , for C i tri c Aci d .

5 . 8

S t ab il i t y C onstant s for C i tr i c Aci

d/

^{C alcium}

C ompl exe s .

5 . 9

V ar i at i on wi th I oni c S tr e ngth of' the S t ab il i t y

47 48 5 0 5 3 54

C onstan t s for C i tr i c Aci d

/

C alcium C omplexe s.

56 5 . 1 0

A Summary of' V alue s Rep or t ed for the S t ab il i ty

C ons tant s for C i tr i c Acid

/

Magn esium C omple xe s .

58

TABLES

₍

C onti nued

₎

5 . 1 1 S t ab i li t y C onstant s for C i tr i c Aci d/M agn esium C ompl exe s .

5 . 1 2 S t ab i l i ty C onstant s for V ari ou s C om pl ex e s . 6 . 0 pH t o pC H C orr e c t i ons .

6 . 1 I llustrat i on s of the Meth od o f C al culat ing the Effect s of Sub s ti tuent s on Aci d Strengths . 6.2 Acid S t rengthening Effect of S ub sti tuent s for

Ali phat ic C arb oxyl i c Aci d s in Aqueou s S oluti on .

6o3 C al cul at i on of the Mi cro Ac i d i ty C on s t ant s f or C i tri c Aci d .

6 . 4 C al culat i on of Macro Acidi ty C onstant s f or C i tr i c

page

59 60 69

73

7 3 7 5

A ci d from C al culat ed M i cro Aci d ity C o ns t ant s . 76 6 . 5

6 . 6

6 . 7 6 . 8

C al cula t ed pK ' s for Several Aci d s .

A C ompari s on of C a l cula t ed and Experi mental Acidi ty C on s t ant s for C i tri c Acid .

C ompari son o f C alculated and Experi mental pK ' s for the Mono M ethyl C i tra t e s .

C ompl ex Strengthening Eff e c t of Sub st i tuent s . 6.9 C al culati on of Stab i li ty C on s t ant s for Vari ous

C i trat e C om pl ex e s .

6 . 1 0 A C ompari s on of C al culated and Experimental

77 8 2

8 2 8 5 8 6

Log Stab i l i ty C on stant s . 88

1 0 . 1 Analysi s M et hod s . 111

1 1 . 1 Flame Phot om et r y R e sult s from the C al ibrati on

of IR-1 20 R e s i n at 1 2°C . 11 7

11. 2 C alibrat i on Dat a for Amb e rl i t e IR-1 20 a t 1 2°C . 11 8

11 . 3 C alibrat i on Dat a for Amb erl i t e IR-1 20 a t 23°C . 120

1 1 . 4 Amb e rli t e IR-1 20 R e s i n C alibra t i on P aram t e r s . 1 21

TABLES ( C ont i nued )

1 1 . 5 Duoli t e C -20 Re s i n C alibrati on Parame t ers . C al culat ed from t he Data of V an Krev eld and Van Minnen ( 1 955) .

page

1 21 11 . 6 C at i on Activi t i e s in Raw B ov i ne Mi lk . 1 27 11 . 7 Effe ct s of Add i t iv e s on Ski m Mi l k . 1 34 1 1 . 8 C at i on C onc entrat i ons and Ac t iv i ti e s i n

Vari ou s Mi l k s . 134

13 . 1 Experi ment al R e sul t s for Synthe t i c Whey . 152 13 . 2 C al cula t ed Re sul t s for Synt het i c Whe y . 157 A I I . 1 React i on Rat e C on s tant s for the Saponifi cat i on

of the Methyl E s t ers of C i t ri c Ac i d . 1 70

I

'

PIGURES

2 . 1 The C ompl e t e Di s s oci ati on Sch eme for C i tri c Acid .

3 . 1 S i mpl i fi ed Flow C hart for C omput er P rogram t o C alculate Aci di ty C onstant s from pH

T i trat i on Dat a .

3 . 2 S i mpl i fi ed Flow Chart for C omputer P rogram t o C alculate S t ab i l i ty C onstant s of M e t al I on C ompl exe s fr om pH T i t rat i on Data .

1 1 . 1 Effect of T emperature on Re sin C ompo s i t ion . 1 1 . 2 R e s i n Bead Fra c t i onati on S cheme Us i ng Standard

S i eve s .

1 1 . 3 Vari ati on of C olumn Effluent C oncentrati on wi th T o tal V ol ume of Effluent .

1 1 . 4 Seasonal Vari a t i on of S odi um and Pot a s sium C onc ent rati ons and pH .

1 1 . 5 S e a s onal V ari ati on of M agn es ium and C al ci um

pag e

1 5

29

30 1 1 3

1 14

1 1 6 1 23

Ion C oncentr at i ons and Activi t i e s . 1 24 1 1 . 6 C at i on Ac tivi t i e s in M i lk wi th Adju s t ed pH ' s . 1 30 1 1 . 7 V ari a t i on of the Rennet C oagulati on T ime of

M i lk wi th C al c i um I on Act iv i ty .

1 1 . 8 V ari at i on o f R enne t C oagulati on Time o f M i lk

1 3 2

wi th pH . 1 33

1 3 . 1 C ompari son of C al culat ed and Experi m ental Data

for Syntheti c Whey . 1 54

1 3 . 2 pH T i trat i on Curv e s for Syntheti c Whey and

S kim M i lk . 1 55

AI . 1 V olume Frac t i on of the M i c el l e Pha s e

of

M i lk . 1 66

A I I . 1 Saponi fi cati on S cheme f or the Methyl C i trat e s . 1 68