Milk

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Milk
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Objectives

• Formation of milk (lactation)
• Nutritional Value of milk
• Composition of milk
• Human milk and animal milk
• The colostrum

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Lactation

• Preparation of breast during pregnancy
• carried out by the ovarian and placental
  hormones (estrogen progesterone mainly)
• Initiation of milk secretion
• Under the effect of lactogenic hormone (from
  ant. Pituitary), starts at the last days of
  pregnancy due to lowering of hormones (where
  prev. hormones inhibit releasing of the
  lactogenic hr.)
• Milk letting
• Flow of milk from breasts occurs after delivery
  by the suckling reflex and release of oxytocin
  (post. Pituitary)

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Nutritional Value of Milk

• Almost complete diet for infant
• Deficient in vit K , C Fe , Cu
• 3 rd m citrus fruit
• 6th m
  soup ,egg yolk

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Color

• White yellowish ,opaque
• carotenes( colostrum cows milk)
• Emulsion of fat colloidal state of proteins
  Ca phosphate

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Reaction

• pH cows 6.6 ,human milk 7.0
• Good buffer( proteins ,HCO3-, PO4,)
• Used for hyperacidity

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Composition of milk

• Lipids
• Proteins
• Carbohydrate
• Minerals and vitamins

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Milk Fat

• Human cows about 3.5
• Present in form of emulsion surrounded by a thin
  coat layer of (PL, cholesterol and proteins)
• TAG 99 , main palmitic, oleic, stearic acids
• Human milk 10 essential. F.A.
• Cows milk 10 butyric acid

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Other lipids

• Small amount of cholesterol, phospholipids, fat
  soluble vit. carotenes
• Rich in vit. A
• Poor in vit. K fair in E
• Cows milk poor in D but human fair

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Milk Proteins

• Human 1.2 , cows 3.5
• Casien 80 (cows),40 (human) ,
• phosphoprotein,
• Rich in methionine,
• Poor in cystine cysteine
• Ppt at its pI (4.6)
• Not coagulable

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Lactalbumin Lactoglobulin (whey protein)

• Human 60 , Cow 20
• Separate in whey
• Heat coagulable
• High biological value
• Cant ppt at pH 4.6
• Include ? globulin (ab.)

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Other proteins

• Lactoferrin
• ???? absorption of iron in intestine
• Contain enzymes e.g.
• proteinases,
• amylase,
• peroxidase, catalase,
• alkaline phosphatase

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Lactose (most suitable sugar)

• Only CHO in milk
• Human 7.4 , cows 4.7
• Digestion gives glucose galactose for E
• Galactose can form glycolipids
• Less sweet not nausea
• Helps growth of lactic acid- producing bacteria
  in the intestine

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• Bacteria
• Lactose Lactic acid
  ?pH
• ? solubility absorption of Ca , Mg 2, PO4 ,
  Fe, Cu
• Inhibits growth of putrefactive bacteria

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Milk Minerals Vitamins

• Human less in minerals than cows
• Rich in Ca , PO4 , K, Cl
• Fair amn. of Na Mg
• Both milk poor in Fe Cu but human is richer
• Rich in vit A B2
• Poor in C K
• Fair in others

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Comparison Between Human Animal Milk
Hman Milk Animal Milk
1- Proteins Amount of curds Types of curds small fine and thin Large Thick and tough
2-Fats Fat globules Volatile acids Small size Absent Large High amounts
3- Carbohydrate Lactose Lactose
4-Minerals Ca P content CaP ratio Iron Smaller Suitable 21 Deficient Higher Not suitable More deficient
5- Reaction Alkaline(7.0) More acidic (6.6)
6- Digestion Easy Difficult
7-Growth promotion More Less

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Colostrum

• Yellowish secreted during the first week
• Differs from mature in
• Higher protein with less casein more whey
  protein
• Esp rich in IgA which prevents gastroenteritis
• Minerals are higher
• Vitamins are higher

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• Fats are lower but with higher fat soluble
  vitamins, carotenes (yellowish color )
• Easier to digest
• Lower lactose , less sweet more suitable for
  new born

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Some Milk Products

• Full cream milk milk containing all of its fat
  e.g. nestogen, SMA and SIMILAC
• Acidified milk milk with pH lower than ordinary
  milk and is used in infants suffering from
  diarrhea or vomiting e.g. Pelargon and prodieton
• Fortified milk milk to which concentrated forms
  of vitamins or minerals are added

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Milk Clotting

• Rennin
• Casein paracasein (sol) peptone
  like
• Paracasein Ca 2
  insoluble Ca para.
• ppts entangling fat fat
  soluble vit.
  
  
• milk clot
  or cheese

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Whey

• greenish yellow (riboflavin) in color contains
• water
• water soluble vitamins,
• lactalbumin, lactaglobulins,
• lactose,
• minerals,
• reduced Ca content

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Milk Curdling

• It is the precipitation of casein at its
  isoelectric pH, (pH 4.6)
• Produced by the action of lactobacillus
  acidophilus
• Fermenting lactose
• Casein ppts fats fat soluble vit. to form
  curds or yogurt

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Whey of the milk curds

• contains
• less lactose
• more B- vitamins( produced by bact.)
• more calcium (not ppt with casein)

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Advantages of colostrum for baby

• Highly nutrititve high proteins and minerals
• High antibody contents mainly gamma globulins
  which give immunity
• Laxative effect which prevents constipation