Milk Composition

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Milk Composition

• AVS346 - Lecture 4

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What is Milk?
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Definition of Milk?

• Definition - Normal secretion of the mammary
  gland of mammals
• More precisely it is a very complex product that
  contains more than 100,000 chemicals that are
  either in solution, suspension or emulsion with
  water.

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Milk Composition

• Solution - dissolve to the molecular level
• Lactose
• Minerals
•  Suspension - Colloid, particles so small they
  will not settle out
• Proteins - Casein
•  Emulsion - compounds that don't mix with water
• Butterfat

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Milk

• Nature's most perfect food
• Nutritional value is greater than the sum of it's
  parts
• One of only two foods we eat whose sole purpose
  in nature is food (Honey is the other)
• High quality ingredients
• Protein AA Content
• Fat
• Sugars
• Complete nutrition for the young animal

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Composition of Milk
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Other Compounds Normally Found in Milk

• Acids
• Citrate, Formate, Acetate, Lactate, Oxalate
• Enzymes
• Peroxidase, Catalase, Lipase, Phosphatase
• Gases
• Oxygen, Nitrogen, Carbon dioxide
• Vitamins
• A, C, D, B Complex

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Factors That Effect Milk Composition

• Breed
• Stage of Lactation
• Season
• Genetics
• Nutrition - Feeds
• Disease Mastitis

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Water

• Lactating cows require lots
• 1 lb. per lb. of milk produced
• Carrier for all other components
• Regulated by the lactose production
• Lactose pumped into the micelles causes osmotic
  pressure which draws water in

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Milkfat

• Complex blend of lipids
• Triglycerides
• 98 of lipids
• Mono and Diglycerides, FFA, Phospholipids and
  Cholesterol
• Fat and water don't mix
• Forms globules surrounded by protein
• Rise to top
• Provide the young with energy
• Content highly variable
• Species, breeds, stage of lactation
• Feed, fiber, temperature

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Milkfat Synthesis

• Two Sources
• Blood (VLDL)
• Longchained FA
• FA Synthesis
• Short Chained Acetate and Betahydroxy Butyrate
• Occurs in cytoplasm
• Small lipid droplets coalesce in cytoplasm

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Changes in Fat Percentage During a Milking
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Fatty Acid Composition
FA Triglyceride composition not random C4 97
in 3 binding site
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Milkfat Globules

• Size ranges from 0.1 to 15 microns in diameter
• Covered by a thin membrane from secretory cells
  (Protein and Phospholipids)
• Helps prevent coalescence and flocculation
• Protects fat from enzymatic action
• Properties enable the production of butter,
  whipped cream and ice cream
• Homogenization
• Decreases diameter making them more stable in
  suspension

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Homogenization
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Milk Proteins

• Several types found in milk
• Casein 76
• Whey proteins 18
• beta lactoglobulin
• alpha lactalbumin
• Lactose synthesis
• Serum proteins
• Blood
• Serum albumin
• Enzymes, hormones, antibodies, growth factors,
  lactoferrin, NPN
• Major proteins are unique to milk
• Amino acids balanced for growth
• Manufactured from AA's

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Protein Composition of Milk
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Casein

• Phosphoproteins about 80 of all milk proteins
• Lack Disulfide bonds and has little secondary and
  tertiary structure
• Form a micelle (140nm) - hydrophobic
• Calcium and phosphates stabilize structure
• Several forms
• Alpha - phosphorylated form S1 and S2 variants
  (39)
• Beta - major (28)
• Kappa - glycoprotein (10)
• Stabilizes the micelle
• Gamma - fragments of beta (3)
• Precipitated by
• pH below 4.6 Low solubility Clots in stomach
• Ultracentrifugation
• Ultrafiltration - reduce trucking costs of milk
  used for cheese.
• Rennin - cheese
• Cleaves Kappa casein

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Milk Fat Inversions

• Usually Holstein milk is 3.7 F and 3.1 P
• Fat inversion 2.9 F and 3.0 P
• Low acetate production in rumen
• High grain low fiber diet
• Decrease acetate
• Increase propionate
• Indicator of acidosis

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High Butterfat Content

• Herd of Holsteins at 3.8 F
• Good Thing??
• Dairy producer paid for increased fat
• High butterfat with average of lower milk
  production
• Indicator of unfulfilled milk production

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Lactose

• Major carbohydrate in milk
• Disaccharide
• Glucose and galactose molecule
• Only present in the mammary gland
• Draws water into the alveoli
• Determines the quantity of milk produced

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Lactose
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Lactose Synthesis

• Glucose
• Major precursor
• Can limit secretion
• 50 made from propionate
• Mammary gland uses 60-85
• 60-70 of that is used to make lactose
• Lactose synthetase - Golgi
• Galactosyltranferase-bound
• Alpha lactalbumin-soluable
• regulatory
• lost in secretory vessicles
• Lactose non-permeable
• Water drawn in to vessicles  

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Mineral and Vitamin Content
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Other Things Found in Milk

• Somatic cells
• Bacteria
• Sediment
• Disinfectants
• Antibiotics
• Pesticides
• Aromatic Compounds
• Excess Water
• Other Stuff

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Milk precursors and their origins for the
synthesis of milk by ruminants
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Pounds of raw milk required to make 1 lb of
product
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Milk - Volume Weight Measures

• 1 gallon of milk 8.62 lbs
• 1 pint of milk 1.08 lbs
• 100 lbs of milk 11.6 gallons