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Milk

Milk. Objectives. Formation of milk (lactation) Nutritional Value of milk Composition of milk Human milk and animal milk The colostrum. Lactation. Preparation of breast during pregnancy : carried out by the ovarian and placental hormones (estrogen & progesterone mainly )

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Milk

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  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)

  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% butyricacid

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

  10. 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

  11. Lactalbumin & Lactoglobulin (whey protein) • Human 60% , Cow 20 % • Separateinwhey • 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. Bacteria • LactoseLacticacid ↓pH • ↑ solubility & absorption of Ca , Mg 2, PO4 , Fe, Cu • Inhibits growth of putrefactive bacteria

  15. Milk Minerals & Vitamins • Humanless in minerals than cow’s • Rich in Ca , PO4 ,K, Cl • Fairamn. 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

  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 2+insoluble Ca para. ppts entangling fat + fat soluble vit. milk clot or cheese

  21. 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 bytheaction of lactobacillus acidophilus • Fermenting lactose • Casein ppts + fats + fat soluble vit. to form curds or yogurt

  23. Wheyof the milk curds contains less lactose moreB- vitamins( produced by bact.) morecalcium (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

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