Composition of Milk Composition of Milk

Milk may be defined as the whole, fresh, clean, Milk may be defined as the whole, fresh, clean, lacteal secretion obtained by the complete milking lacteal secretion obtained by the complete milking of one or more healthy milch animals, excluding of one or more healthy milch animals, excluding that obtained within 15 days before or 5 days after that obtained within 15 days before or 5 days after calving or such periods as may be necessary to calving or such periods as may be necessary to render the milk practically colostrums-free, and render the milk practically colostrums-free, and containing the minimum prescribed percentage of containing the minimum prescribed percentage of milk fat and milk solid not fatmilk fat and milk solid not fat

LactoseLactose By weight the most abundant of milk solids By weight the most abundant of milk solids

(4.8-5.2% of milk; 52% of SNF,70% of whey (4.8-5.2% of milk; 52% of SNF,70% of whey solids)solids)

Exists only in milk in true solution form in Exists only in milk in true solution form in milk serummilk serum

One-sixth as sweet as sucrose3 whey by One-sixth as sweet as sucrose3 whey by driolyzed by B-d-galactosidase (lactose)-the driolyzed by B-d-galactosidase (lactose)-the result is increased sweetness and depressed FPresult is increased sweetness and depressed FP

Disacchride-onem mole cule each of glucose Disacchride-onem mole cule each of glucose and galactose.and galactose.

Occurs in twso forms alpha and beta which Occurs in twso forms alpha and beta which differ in their propertiesdiffer in their properties

Alpha form less soluble (7% w/w in water @ Alpha form less soluble (7% w/w in water @ 151500C than betw formC than betw form

Equilibrium mixture of both forms has a Equilibrium mixture of both forms has a solubility of 17% at 15solubility of 17% at 1500CC

Used as a fermentation substrate by LAB-the Used as a fermentation substrate by LAB-the basis for the manufacture of fermented/cultured basis for the manufacture of fermented/cultured dairy products (spoilage microflora-souring)dairy products (spoilage microflora-souring)

Lactose intolerance-absence of lactose.Lactose intolerance-absence of lactose.

Crystallization of lactose occurs in alpha form Crystallization of lactose occurs in alpha form which takes a tomahawk shape-results in a which takes a tomahawk shape-results in a deffect called sandiness in ice cream and deffect called sandiness in ice cream and sweetened condensed milk.sweetened condensed milk.

In addition to lactose milk contains other CHO In addition to lactose milk contains other CHO in small amounts eg glucose galactose OSin small amounts eg glucose galactose OS

NutritionalNutritional Useful source of dietaryUseful source of dietary Promotes absorption of Ca from the dietPromotes absorption of Ca from the diet

Standards for different milks in IndiaStandards for different milks in India

MinimumMinimum

S.S.NoNo

Class of Class of milkmilk

DesignationDesignation % Fat% Fat % SNF% SNF

11 Buffalo milkBuffalo milk Raw Pasteurized,Raw Pasteurized,

boiled, flavoured boiled, flavoured and sterilizedand sterilized

5-65-6 9.09.0

22 Cow MilkCow Milk -do--do- 3.5-4.03.5-4.0 8.58.5

3 3 Goat or Goat or sheep milksheep milk

do-do- 3.0-3.53.0-3.5 9.09.0

44 Standardized Standardized milk milk

-do--do- 4.54.5 8.58.5

MinimumMinimum

S.NoS.No Class of milkClass of milk DesignationDesignation % Fat% Fat % SNF% SNF

5.5. Recombined Recombined milkmilk

Raw Raw PasteurizedPasteurized

boiled, boiled, flavoured flavoured and sterilizedand sterilized

3.03.0 8.58.5

6.6. Toned milkToned milk -do--do- 3.03.0 8.58.5

77 Double toned Double toned milkmilk

-do--do- 1.51.5 9.09.0

8.8. Skim MilkSkim Milk -do--do- Not more than Not more than 0.50.5

8.78.7

Composition Composition

Percentage compositionPercentage composition

Name of Name of SpsSps

WaterWater FatFat ProteinProtein LactoseLactose AshAsh

11 Cow Cow (Foreign)(Foreign)

86.686.6 4.64.6 3.43.4 4.94.9 0.70.7

2.2. Cow Cow (Zebu)(Zebu)

86.586.5 4.94.9 3.23.2 4.64.6 0.70.7

3.3. BuffaloBuffalo 84.284.2 6.66.6 3.93.9 5.25.2 0.80.8

4.4. HumanHuman 87.787.7 3.63.6 1.81.8 6.86.8 0.10.1

Name of Name of SpsSps

WaterWater FatFat ProteinProtein LactosLactosee

AshAsh

SheepSheep 79.479.4 8.68.6 6.76.7 4.34.3 1.01.0

GoatGoat 86.586.5 4.54.5 3.53.5 4.74.7 0.80.8

MareMare 89.189.1 1.61.6 2.72.7 6.16.1 0.50.5

Approx Composition : (Cow)Approx Composition : (Cow) WaterWater 87 % (85-88%)87 % (85-88%) FatFat 3.9 % (2.4-5.5 %)3.9 % (2.4-5.5 %) SNFSNF 8.8% ( 7.9-10.0%)8.8% ( 7.9-10.0%)

• Protein 3.25%Protein 3.25%• Lactose 4.6%Lactose 4.6%• Minerals 0.65-0.7% (Ca, P, citrate, Mg ,Na ,K, Zn, Minerals 0.65-0.7% (Ca, P, citrate, Mg ,Na ,K, Zn,

Cl,Fe,Cu,So Cl,Fe,Cu,So44HCoHCo33))• Acids - 0.18%Acids - 0.18% ( citrate, formate, acetate ,lactate ( citrate, formate, acetate ,lactate

oxalate) oxalate)• Enzymes - Peroxides, catalase, phosphates, lipaseEnzymes - Peroxides, catalase, phosphates, lipase• Gases - Oxygen, NitrogenGases - Oxygen, Nitrogen• Vitamins- ADEK, C&B VitaminsVitamins- ADEK, C&B Vitamins

Terms to describe milk fractions:Terms to describe milk fractions:

Whole MilkWhole Milk

↓ ↓ FatFat

SM/PlasmaSM/Plasma

Plasma =Plasma = Milk-fat (Skim milk)Milk-fat (Skim milk)

Serum =Serum = Plasma-casein micelles Plasma-casein micelles (whey)(whey)

↓ ↓ Cn micellesCn micelles SNF =SNF = Protein, lactose, minerals, Protein, lactose, minerals, acids, enzymes vitaminsacids, enzymes vitamins

Serum/WheySerum/Whey TS =TS = Fat + SNFFat + SNF

Milk described as:Milk described as: An oil-in-waterAn oil-in-water emulsion with fat globules emulsion with fat globules

dispersed in the continuous serum phasedispersed in the continuous serum phase A Colloidal suspensionA Colloidal suspension of casein micelles, of casein micelles,

globular proteins and lipoprotein particlesglobular proteins and lipoprotein particles A solution of lactose, soluble proteins, A solution of lactose, soluble proteins,

minerals, vitamins etc.minerals, vitamins etc.

_______________ MILK_______________________ MILK________

True fat ( 98% TGs + MG+ DG+ FFA

Phospholipids(Lecithin, Cephalin,Sphyngomylin)

Water Total Solids

Fat (Lipids)Emulsion form (50-100 nm dia.)

SNF

AssociatedSubstance

Lactose(solution form, .01 -1 nm)

NitrogenSubstance

Mineralmatter

Otherconstituents

Cholesterol Carotene Vitamins(A,D,E,K)

Non protein Protein(Suspension, 1-100nm dia.)

Caseins(α,β,γ,κ)

α- Lactalbumin β Lactglobulin Proteose Peptones

PO4, citrates , Chlorides of Na, K, Ca, Mg + traces of Fe, Cu, I etc.

•Pigments•Dissolved Gases•Vit. C &B Complex.•Enzymes•etc

Constituents of Milk:Constituents of Milk:

WaterWater water constitutes the medium in which other water constitutes the medium in which other

milk constituents are either dissolved or milk constituents are either dissolved or suspended.suspended.

Mostly in free from but some portion also in Mostly in free from but some portion also in bound form being firmly bound by milk bound form being firmly bound by milk proteins, PL etc.proteins, PL etc.

Milk Fat/ LipidsMilk Fat/ Lipids

StructureStructure The bulk of the milk fat in milk exists in the form of The bulk of the milk fat in milk exists in the form of

small globulessmall globules which average 3um in size (0.1- which average 3um in size (0.1-22um).22um).

Oil-in-water type of emulsionOil-in-water type of emulsion The surface of fat globules is coated with an adsorbed The surface of fat globules is coated with an adsorbed

layer - layer - FGM. FGM. FGM contains FGM contains PL & proteins PL & proteins in the form of a in the form of a

complexcomplex that that stabilizesstabilizes the emulsion (prevents fat the emulsion (prevents fat globules from coalescing & separating ) globules from coalescing & separating )

The emulsion can, however, can be broken by The emulsion can, however, can be broken by agitation at low temperaturesagitation at low temperatures Heating Heating Freezing etc.Freezing etc.

when milk is held undisturbed- fat globules tend to when milk is held undisturbed- fat globules tend to rise to the surface to form a cream layerrise to the surface to form a cream layer

higher fat content , large sized FG - thicker creamhigher fat content , large sized FG - thicker cream Stokes lawStokes law predicts that the FG will cream due to predicts that the FG will cream due to

differences in densities between the fat and plasma differences in densities between the fat and plasma phases of milkphases of milk

however, in cold raw milk, creaming takes place however, in cold raw milk, creaming takes place faster than is predicated by stoke's law alone faster than is predicated by stoke's law alone

IgM forms a complex with lipoproteins k/a IgM forms a complex with lipoproteins k/a cryoglobulincryoglobulin

Cryoglobulin ppts. On to the FG and cause Cryoglobulin ppts. On to the FG and cause flocculation - flocculation - cold agglutinationcold agglutination

As fat globules cluster, the speed of rising increases As fat globules cluster, the speed of rising increases and sweeps up the smaller globules with themand sweeps up the smaller globules with them

The cream layer forms rapidly within 20-30min,. In The cream layer forms rapidly within 20-30min,. In cold milk.cold milk.

Milk LipidsMilk LipidsChemical propertiesChemical properties Economic importance – price index Economic importance – price index Originate either from microbial activity in rumen and Originate either from microbial activity in rumen and

transported to secretary cells via blood and lymph or transported to secretary cells via blood and lymph or synthesis in the secretary cellssynthesis in the secretary cells

Main lipids in milk are triglycerides (glycerol+3FA ,98%) Main lipids in milk are triglycerides (glycerol+3FA ,98%) Major Fatty acids in milk:Major Fatty acids in milk:

Long chain Short chain Long chain Short chain C14-Myristic 11% C4-ButyricC14-Myristic 11% C4-Butyric

C16-Palmitic 26% C6-CaproicC16-Palmitic 26% C6-Caproic

C18-Stearic 10% C8-CaprylicC18-Stearic 10% C8-Caprylic

C18:1-Oleic 20% C10-Capric C18:1-Oleic 20% C10-Capric

There is a small number of There is a small number of monomono, , diglyceridesdiglycerides and and FFA FFA in fresh milk which may be due to either in fresh milk which may be due to either early early lipolysis lipolysis or or incompelete synthesis incompelete synthesis

other lipid classes in milkother lipid classes in milk Phospholipids (0.8%) mainly associated with FGM Phospholipids (0.8%) mainly associated with FGM Cholesterol (0.3%) mainly located in FG core Cholesterol (0.3%) mainly located in FG core

Lipids of milkLipids of milk

ConstituentConstituent Range of Range of occurrenceoccurrence

Location in milkLocation in milk

TriglyceridesTriglycerides 98-99%98-99% Fat globulesFat globules

PL (Lec ,ceph, sphing)PL (Lec ,ceph, sphing) 0.2-1.0%0.2-1.0% Globule membrane Globule membrane and serumand serum

Sterols (Cholesterol, Sterols (Cholesterol, Lansterol)Lansterol)

0.25-0.25-0.40%0.40%

Fat globules, Fat globules, globule membrane globule membrane and milk serumand milk serum

FFAFFA TracesTraces Fat globules and Fat globules and milk serummilk serum

WaxesWaxes TracesTraces Fat globulesFat globules

SqualeneSqualene TracesTraces Fat globulesFat globules

Fat-soluble Fat-soluble vitaminsvitamins

TracsTracs Fat globulesFat globules

Vit .AVit .A 7.0-8.5 ug /g fat7.0-8.5 ug /g fat

CarotenoidsCarotenoids 8-10 ug /g fat8-10 ug /g fat

Vit EVit E 2-50 ug /g fat2-50 ug /g fat

Vit DVit D TracesTraces

Vit KVit K TracesTraces

Functional propertiesFunctional properties provides lubricationprovides lubrication Impart a creamy mouth feelImpart a creamy mouth feel provides unique flavour in butter (low levels of provides unique flavour in butter (low levels of

SCFA)SCFA) Reservoir for other flavours eg. in aged cheeseReservoir for other flavours eg. in aged cheese shortening effect in cheese (keeps protein matrix shortening effect in cheese (keeps protein matrix

extended to give a soft texture)extended to give a soft texture) Provides energy @ 9cal./g. Provides energy @ 9cal./g. Provides nutrients (EFA. Vit.ADEK)Provides nutrients (EFA. Vit.ADEK)

Milk ProteinsMilk Proteins Fall into two distinct typesFall into two distinct types CaseinsCaseins Whey proteinWhey protein

The concentration of proteins in milk :The concentration of proteins in milk :

Grams/litreGrams/litre % of total % of total proteinsproteins

Total proteinTotal protein 3333 100100

Total CaseinsTotal Caseins 2626 79.579.5

Alpha sAlpha s11 1010 30.630.6

Alpha sAlpha s22 2.62.6 8.08.0

BetaBeta 9.39.3 28.428.4

KappaKappa 3.33.3 10.110.1

Total whey Total whey proteinsproteins

6.36.3 19.319.3

Alpha Alpha lactalbuminlactalbumin

1.21.2 3.73.7

Beta lacto Beta lacto globulinglobulin

3.23.2 9.89.8

BSABSA 0.40.4 1.21.2

ImmunoglobulinImmunoglobulin 0.70.7 2.12.1

Proteose peptoneProteose peptone 0.80.8 2.42.4

CaseinsCaseins Found only in milkFound only in milk Caseins constitute about 80% of total proteinCaseins constitute about 80% of total protein Caseins have five classesCaseins have five classes~ Alpha SAlpha S11

~ Alpha sAlpha s22

~ BetaBeta~ KappaKappa~ Gamma (Proteolysis of B-cn.) ( < 5%)Gamma (Proteolysis of B-cn.) ( < 5%)• Caseins are resistant to heat denaturation because:Caseins are resistant to heat denaturation because:~ Primary structure completely definedPrimary structure completely defined

~ have a modest sizehave a modest size~ Do not possess an organized structureDo not possess an organized structure~ Lack tertiary structure & disulfide bondsLack tertiary structure & disulfide bonds~ Very little structure to unfoldVery little structure to unfold• Present in colloidal statePresent in colloidal state• Have low solubility at pH 4.6Have low solubility at pH 4.6• Conjugated proteins (mostly with phosphate Conjugated proteins (mostly with phosphate

groups)groups)• Calcium binding is proportional to phosphate Calcium binding is proportional to phosphate

content.content.

Composition and properties of caseins fractionComposition and properties of caseins fraction

FractionFraction MoleculaMolecular weightr weight

Proportion Proportion whole whole caseins %caseins %

Serine-Serine-PO 4 PO 4 residuesresidues

Calcium Calcium sensitivitysensitivity

CarbohyCarbohydratedrate

Alpha sAlpha s11 23 00023 000 38.138.1 5-95-9 ++++ --

Alpha sAlpha s22 25 00025 000 10.210.2 10-1310-13 ++++++ --

BetaBeta 24 00024 000 35.735.7 55 ++ --

GammaGamma 11600-11600-2050020500

3.23.2 0 or 10 or 1 -- --

KappaKappa 12.812.8 11 -- ++

StructureStructure Caseins organized into particles ( 100 nm)Caseins organized into particles ( 100 nm) Exist in micelles- porous colloidal particlesExist in micelles- porous colloidal particles Biological function is to carry caP (insoluble to Biological function is to carry caP (insoluble to

mammalian young in liquid form for efficient mammalian young in liquid form for efficient nutrition.nutrition.

Micelles Contain:Micelles Contain:~ Casein proteinCasein protein~ CalcuimCalcuim~ PhospharePhosphare~ CitrateCitrate~ Minor ionsMinor ions

~ LipascLipasc~ PlasminPlasmin~ Entrapped milk scrumEntrapped milk scrum Micellar frame workMicellar frame work~ Alpha s forms the network Alpha s forms the network ~ Complexed with caPComplexed with caP~ Beta and Kappa caseins accommodated in the Alpha Beta and Kappa caseins accommodated in the Alpha

S frame work S frame work~ Kappa casein also localized on the micelle surface-Kappa casein also localized on the micelle surface-

provides stabilityprovides stability

K-cn+ Renent K-cn+ Renent CleavageCleavage

At phe 105-Met 106 bond

Eliminates stabilizing ability

Hydrophilic Portion K-Cn .Glycomacropeptide(GMP)

OR Caseinomacropeptide(CMP) Hydrophobic portionPara.kappa casein

Whey proteinsWhey proteins Milk Milk pption at pH. 4.6 pption at pH. 4.6 Supernatant (whey Supernatant (whey

proteins ) proteins ) Colloidal state Colloidal state Globular proteins Globular proteins more water soluble than caseins more water soluble than caseins Heat denaturable ( @ >65Heat denaturable ( @ >6500C)C) Denaturation increase WHC.Denaturation increase WHC. Have good gelling and whipping properties Have good gelling and whipping properties Principal fractions: Principal fractions: B – lactoglobulim, MW- 18,000B – lactoglobulim, MW- 18,000

Alpha- lactalbumin, MW-14,000Alpha- lactalbumin, MW-14,000 BSABSA Ig.Ig. Contain sulphur amino acidContain sulphur amino acid

Nutritional value.Nutritional value. Milk proteins have very high NVMilk proteins have very high NV score very highly on Provisional scoring pattern for score very highly on Provisional scoring pattern for

quality (UN,FAO)quality (UN,FAO) Caseins poorer in SSA, WP –richer Caseins poorer in SSA, WP –richer But complementary nature of the aa profile of the But complementary nature of the aa profile of the

two protein fractions is exceptionally high. two protein fractions is exceptionally high.

Milk protein are complementary to grain and soy Milk protein are complementary to grain and soy proteins proteins

Milk Proteins ideal for fortification of food stuffs.Milk Proteins ideal for fortification of food stuffs. Protein highly digestible.Protein highly digestible.

LactoseLactose By weight the most abundant of milk solids By weight the most abundant of milk solids

(4.8-5.2% of milk; 52% of SNF,70% of whey solids)(4.8-5.2% of milk; 52% of SNF,70% of whey solids) Exists only in milk in true solution form in milk Exists only in milk in true solution form in milk

serumserum One-sixth as sweet as sucrose when hydrolyzed by One-sixth as sweet as sucrose when hydrolyzed by

B-D-galactosidase (lactase)-the result is increased B-D-galactosidase (lactase)-the result is increased sweetness and depressed FPsweetness and depressed FP

Disacchride-one molecule each of glucose and Disacchride-one molecule each of glucose and galactose.galactose.

Occurs in two forms alpha and beta which differ in Occurs in two forms alpha and beta which differ in their propertiestheir properties

Alpha form less soluble (7% w/w in water @ 15Alpha form less soluble (7% w/w in water @ 1500C C than beta formthan beta form

Equilibrium mixture of both forms has a solubility Equilibrium mixture of both forms has a solubility of 17% at 15of 17% at 1500CC

Used as a fermentation substrate by LAB-the basis Used as a fermentation substrate by LAB-the basis for the manufacture of fermented/cultured dairy for the manufacture of fermented/cultured dairy products (spoilage microflora-souring)products (spoilage microflora-souring)

Lactose intolerance-absence of lactaseLactose intolerance-absence of lactase

Crystallization of lactose occurs in alpha form Crystallization of lactose occurs in alpha form which takes a tomahawk shape-results in a deffect which takes a tomahawk shape-results in a deffect called sandiness in ice cream and sweetened called sandiness in ice cream and sweetened condensed milk.condensed milk.

In addition to lactose milk contains other CHO in In addition to lactose milk contains other CHO in small amounts eg. Glucose,galactose, OSsmall amounts eg. Glucose,galactose, OS

NutritionalNutritional Useful source of dietary energyUseful source of dietary energy Promotes absorption of Ca from the dietPromotes absorption of Ca from the diet