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Milk Composition and Properties Art Hill University of Guelph www.foodscience.ca American Cheese Society

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Page 1: Milk Composition and Properties - American Cheese  · PDF fileMilk Composition and Properties Art Hill University of Guelph   American Cheese Society

Milk Composition and Properties

Art HillUniversity of Guelphwww.foodscience.ca

American Cheese Society

Page 2: Milk Composition and Properties - American Cheese  · PDF fileMilk Composition and Properties Art Hill University of Guelph   American Cheese Society

Contents

• Milk structure• Amounts and properties of principal

milk components• Transfer of milk components to cheese• Q & A

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Page 3: Milk Composition and Properties - American Cheese  · PDF fileMilk Composition and Properties Art Hill University of Guelph   American Cheese Society

WHAT’S IN THE BAG?

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Page 4: Milk Composition and Properties - American Cheese  · PDF fileMilk Composition and Properties Art Hill University of Guelph   American Cheese Society

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Milk Structure

• Milk is a dispersion of fat globules (fat particles) and casein micelles (protein particles) in a continuous phase of water, sugar (lactose), whey proteins, and minerals.

• Milk Plasma = milk minus fat globules ≈skim milk

• Milk Serum = plasma minus micelles ≈ Cheese whey

• Milk permeate = serum less whey proteins

Page 5: Milk Composition and Properties - American Cheese  · PDF fileMilk Composition and Properties Art Hill University of Guelph   American Cheese Society

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Milk

Plasma500X

Serum50,000X

Figure 8.1. Structural elements of milk. After Walstra and Jenness in Dairy Chemistry & Physics, Wiley & Sons., N.Y.

fatglobules0.1 - 10 microns

caseinmicelles10-300nM

Page 6: Milk Composition and Properties - American Cheese  · PDF fileMilk Composition and Properties Art Hill University of Guelph   American Cheese Society

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Electron microscope image of skim milk showing a large micelle casein micelle in the foreground and smaller ones around it. Photo credit, Paul Spagnuolo, University of Guelph.

Page 7: Milk Composition and Properties - American Cheese  · PDF fileMilk Composition and Properties Art Hill University of Guelph   American Cheese Society

Gravity creaming

0

0.2

0.4

0.6

0.8

1

1.2

0 30 60 90 120 150 180 210Time (min)

Norm

alize

d Fa

t

Tank C Tank D

NF = % fat/control fat

Page 8: Milk Composition and Properties - American Cheese  · PDF fileMilk Composition and Properties Art Hill University of Guelph   American Cheese Society

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Vertical gravity creaming device, Lodi, Italy

Page 9: Milk Composition and Properties - American Cheese  · PDF fileMilk Composition and Properties Art Hill University of Guelph   American Cheese Society

Contents

• Milk structure• Amounts and properties of principal

milk components• Transfer of milk components to cheese• Q & A

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Page 10: Milk Composition and Properties - American Cheese  · PDF fileMilk Composition and Properties Art Hill University of Guelph   American Cheese Society

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Proximate Analysis (kg/hl)

Fat 3.90 Most diverse Protein 3.30 Casein 2.54 (77%)

Whey 0.76 (23%)Lactose 4.8 Glucose + galactose

Ash 0.70 Includes all essential minerals

Solids 12.7 We truck a lot of water

Page 11: Milk Composition and Properties - American Cheese  · PDF fileMilk Composition and Properties Art Hill University of Guelph   American Cheese Society

Species

• Milk from any of the order ruminant can be used to make cheese, especially those of the suborder ruminata.

• Camels and Illamas are ruminants of the suborder Tylopoda, and their milk is not great for cheese.

• None ruminant milk is low in casein

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Page 12: Milk Composition and Properties - American Cheese  · PDF fileMilk Composition and Properties Art Hill University of Guelph   American Cheese Society

Typical gross composition (kg/100 kg) of milk of cow, sheep, buffalo and goat milk).

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Cow Sheep Buffalo Goat

Fat 3.9 7.2 7.4 4.0

Total protein

3.3 4.6 3.8 3.2

Casein 2.6 3.9 3.2 2.6

Whey protein

0.7 0.7 0.6 0.6

Lactose 4.6 4.8 4.8 4.3

Ash 0.7 0.9 0.8 0.8

Page 13: Milk Composition and Properties - American Cheese  · PDF fileMilk Composition and Properties Art Hill University of Guelph   American Cheese Society

Some properties of caseins that are important to cheese making.

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Name Symbol Percent of casein

Properties

Alpha-S1 casein

α-S1 33 Binds Ca strongly.Broken down by rennet, but not by plasmin.

Alpha-S2 casein

α-S2 11 Binds Ca strongly

Beta-casein β 33 Partially soluble in cold milk.Broken down by plasmin, but not rennet.

Kappa-casein

κ 11 Stabilizes casein against coagulation.Bonds with whey proteins during heating.

Page 14: Milk Composition and Properties - American Cheese  · PDF fileMilk Composition and Properties Art Hill University of Guelph   American Cheese Society

Some properties of whey proteins that are important for cheese making.

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Name % of Whey

Protein

Properties

Beta-lactoglobulin 40 Interacts with kappa-casein at T >65ºC. Principal component of ricotta cheese.

Alpha-lactalbumin 15 Coagulates slowly at temperature >60ºCOther heat sensitive proteins

10 Mainly immunoglobulin's and serum albumin.

Heat stable proteins

14 Cannot be removed by heat, not recovered in ricotta cheese.

Non-protein nitrogen

21 Amino acids, ammonia, urea and small protein fragments.

Page 15: Milk Composition and Properties - American Cheese  · PDF fileMilk Composition and Properties Art Hill University of Guelph   American Cheese Society

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Raw milk

Vat, 85 C, 10 min

HTST, 98 C, 1.87 min

UHT, 140 C, 6 s

Effect of milk heat treatment on yogurt viscosity Effect of milk heat treatment on yogurt viscosity versus incubation time. versus incubation time.

Page 16: Milk Composition and Properties - American Cheese  · PDF fileMilk Composition and Properties Art Hill University of Guelph   American Cheese Society

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50

40

30

20

10

70 75 80 85 90Pasteurization temperature °C

Whey protein denaturation versusHTST (16s) temperature (Fox et al 2000)

1 2Maximum curd firming rate versus whey protein denaturation (Fox al, 2000)30

25

20

15

10

5

00 10 20 30 40Whey protein denaturation (%)

90

70

50

300 10 20 30 40Whey protein denaturation (%)

Time from setting (rennet addition) to cutting versus whey protein denaturation (Fox et al, 2000)

4

30

25

20

15

10

5

00 10 20 30 40

Whey protein denaturation (%)

Curd firmness versus whey protein denaturation (Fox et al, 2000)

3

Page 17: Milk Composition and Properties - American Cheese  · PDF fileMilk Composition and Properties Art Hill University of Guelph   American Cheese Society

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Factors affecting composition

• Species• Genetics (Breed)• Feed• Milking frequency• Stage of lactation• Number of lactations• Season

Page 18: Milk Composition and Properties - American Cheese  · PDF fileMilk Composition and Properties Art Hill University of Guelph   American Cheese Society

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• Species– Goat milk

• Fat globules: Mean 2.76 μM, Range 0.73 – 8.58 μM versus 3.5 and 0.92 – 15.8 μM for cow milk

• More lipolysis especially greater release of short chain fatty acids relative to cow milk

• Low heat stability at native pH relative to cow milk;

• Casein reduced in Alpha-S1 null milk• More fat relative to protein• Plasmin activity

Page 19: Milk Composition and Properties - American Cheese  · PDF fileMilk Composition and Properties Art Hill University of Guelph   American Cheese Society

– Sheep milk • Much higher solids• More fat relative to protein• Traditionally valued for hard cheese

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Page 20: Milk Composition and Properties - American Cheese  · PDF fileMilk Composition and Properties Art Hill University of Guelph   American Cheese Society

Breed: typical fat and protein contents (kg/100 kg) for the milk of several breeds of dairy cows (various sources)

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Breed Fat Protein Protein/Fat Ratio

Jersey 5.4 3.8 0.7

Holstein 3.8 3.2 0.84

Guernsey 4.9+ 3.6 0.73

Ayershire 4.0 3.3 0.83

Page 21: Milk Composition and Properties - American Cheese  · PDF fileMilk Composition and Properties Art Hill University of Guelph   American Cheese Society

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Protein group or

phenotype DistributionMilk Com-

position

Curd Prop-erties

Cheese Yield

κ-CN vs other casiens

13% casein +protein -RCT, +CF,

+Y

-SYNκ-CN B vs A

% B 25 in Holstein; 88 in Jersey

+protein, +CN

-RCT, +CF, +SYN

+Y, +FR

β-LG B vs A

B in most breeds

+CN#, +Fat, +CN/fat, +Plasmin

-RCT, +CF, -SYN

+Y

Page 22: Milk Composition and Properties - American Cheese  · PDF fileMilk Composition and Properties Art Hill University of Guelph   American Cheese Society

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• Feed– More roughage = higher fat and lower

P/F– Nutritionally functional fats

Page 23: Milk Composition and Properties - American Cheese  · PDF fileMilk Composition and Properties Art Hill University of Guelph   American Cheese Society

Fish MealFunctional Fats in Milk

DHA and CLA

• Direct addition

• Genetics

• Feed

Page 24: Milk Composition and Properties - American Cheese  · PDF fileMilk Composition and Properties Art Hill University of Guelph   American Cheese Society

• Stage of Lactation– Milk production peaks at about 60 days of

lactation and declines there after– Fat and protein are minimum at 60 days and

increase thereafter– Protein/fat ratio peaks at sixty days and

decreases thereafter.

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Page 25: Milk Composition and Properties - American Cheese  · PDF fileMilk Composition and Properties Art Hill University of Guelph   American Cheese Society

Lactation number

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# Fat Prot Lact Ash SNF Solids

1 3.55 3.21 4.89 0.68 8.76 12.33

2 3.65 3.49 4.72 0.74 8.94 12.60

3 4.09 3.80 4.51 0.80 9.05 13.20

4 4.54 4.10 4.19 0.86 9.19 13.67

Bhosale et a;. Veterinary World Vol.2, No.1, January 2009

Page 26: Milk Composition and Properties - American Cheese  · PDF fileMilk Composition and Properties Art Hill University of Guelph   American Cheese Society

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Mean fat content by month kg/hl

3.703.753.803.853.903.954.004.054.10

Aug Sep OctNov Dec Ja

nFeb Mar Apr May Ju

n Jul

Fat k

g/hl

91/92 96/97 97/98 98/99 99/00 00/01

Figure 4.1 top left

Page 27: Milk Composition and Properties - American Cheese  · PDF fileMilk Composition and Properties Art Hill University of Guelph   American Cheese Society

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Mean protein content by month kg/hl

3.103.153.203.253.303.353.403.453.50

Aug Sep OctNov Dec Ja

nFeb Mar Apr May Ju

n Jul

Prot

ein

kg/h

l

91/92 96/97 97/98 98/9999/00 00/01

Figure 4.1 top right

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Mean Other Solids content by month kg/hl

5.64

5.68

5.72

5.76

5.80

5.84

Aug Sep OctNov Dec Ja

nFeb Mar Apr May Ju

n Jul

Oth

er S

olid

s kg

/hl

91/92 96/97 97/98 98/9999/00 00/01

Figure 4.1 bottom left

Page 29: Milk Composition and Properties - American Cheese  · PDF fileMilk Composition and Properties Art Hill University of Guelph   American Cheese Society

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Mean protein/fat ratio by month

0.810.820.830.840.850.860.870.88

Aug Sep OctNov Dec Ja

nFeb Mar Apr May Ju

n Jul

Prot

ein/

fat r

atio

91/92 96/97 97/98 98/9999/00 00/01

Figure 4.1 bottom right

Page 30: Milk Composition and Properties - American Cheese  · PDF fileMilk Composition and Properties Art Hill University of Guelph   American Cheese Society

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Summary of seasonal effects

§ Fat minimum in August, maximum in October§ Protein content changes roughly in parallel with

fat content, but the fat variations are smaller causing high protein fat ratios (P/F) during the summer and low P/F ratios in the winter.§ Casein content also varies with season.§ Casein can be estimated as:

casein = (0.833 x protein) - 0.208

Page 31: Milk Composition and Properties - American Cheese  · PDF fileMilk Composition and Properties Art Hill University of Guelph   American Cheese Society

Contents

• Milk structure• Amounts and properties of principal

milk components• Transfer of milk components to

cheese• Q & A

31

Page 32: Milk Composition and Properties - American Cheese  · PDF fileMilk Composition and Properties Art Hill University of Guelph   American Cheese Society

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12.1. Distribution of Milk Components(kg/100 kg of standardized milk, assuming cheese of 40% moisture and 50% FDM; expected yield is

about 10% of milk weight)

Fat Prot CHO Ash SolidsMilk 3.3 3.2 5.0 0.73 12.4Cheese 31.0 25.0 1.7 2.2 60.0Whey 0.22 0.61 5.3 0.58 7.0%Transfer 93 78 3 30 49

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Q and A