1. Milk

2. Objectives Formation of milk (lactation) Nutritional Value of milk
Composition of milk
Human milk and animal milk
The colostrum

3. 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)
Formation of milk is an active secretory process that occurs in three successive processes:

4. 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

5. Color White ± yellowish ,opaque carotenes( colostrum + cow’s milk)
Emulsion of fat + colloidal state of proteins & Ca phosphate

6. Reaction pH cow’s 6.6 ,human milk 7.0
Good buffer( proteins ,HCO3-, PO4,)
Used for hyperacidity

7. Composition of milk
Lipids
Proteins
Carbohydrate
Minerals and vitamins

8. 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.
Cow’s milk 10% butyric acid

9. Other lipids : Rich in vit. A Poor in vit. K fair in E
Small amount of cholesterol, phospholipids, fat soluble vit. & carotenes
Rich in vit. A
Poor in vit. K fair in E
Cow’s milk poor in D but human fair

10. Casien : 80% (cow’s),40% (human) ,
Milk Proteins
Human 1.2% , cow’s 3.5%
Casien : 80% (cow’s),40% (human) ,
phosphoprotein,
Rich in methionine,
Poor in cystine & cysteine
Ppt at its pI (4.6)
Not coagulable
The rate of growth of newborns of different species of animals depend on a greater extent upon the ratio of proteins in their milk

11. Lactalbumin & Lactoglobulin (whey protein)
Human 60% , Cow 20 %
Separate in whey
Heat coagulable
High biological value
Can’t ppt at pH 4.6
Include Ɣ –globulin (ab.)

12. Other proteins Lactoferrin: ↑↑↑↑ absorption of iron in intestine
Contain enzymes e.g.
proteinases,
amylase,
peroxidase, catalase,
alkaline phosphatase

13. Lactose (most suitable sugar)
Only CHO in milk
Human 7.4% , cow’s 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

14. ↑ solubility & absorption of Ca , Mg 2, PO4 , Fe, Cu
Bacteria
Lactose Lactic acid ↓pH
↑ solubility & absorption of Ca , Mg 2, PO4 , Fe, Cu
Inhibits growth of putrefactive bacteria

15. Milk Minerals & Vitamins
Human less in minerals than cow’s
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

16. 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
High amounts
3- Carbohydrate
Lactose
4-Minerals:
Ca: P content
Ca:P ratio
Iron
Smaller
Suitable 2:1
Deficient
Higher
Not suitable
More deficient
5- Reaction
Alkaline(7.0)
More acidic (6.6)
6- Digestion
Easy
Difficult
7-Growth promotion
More
Less
Fine and thin curds are easier to digest
Large amounts of volatile fatty acids render animal milk irritant to gastric mucosa
Large size of fat globules interfere w their adequate digestion

17. 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

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

19. 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

20. Milk Clotting Rennin Casein paracasein (sol) +peptone –like
Paracasein + Ca insoluble Ca para.
ppts entangling fat + fat soluble vit.
milk clot or cheese

21. greenish yellow (riboflavin) in color contains
Whey :
greenish yellow (riboflavin) in color contains
water &
water soluble vitamins,
lactalbumin, lactaglobulins,
lactose,
minerals,
reduced Ca content

22. 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

23. Whey of the milk curds contains less lactose
more B- vitamins( produced by bact.)
more calcium (not ppt with casein)

24. 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