MilkMilk

ObjectivesObjectives

• Formation of milk (lactation)

• Nutritional Value of milk

• Composition of milk

• Human milk and animal milk

• The colostrum

LactationLactation• 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)

Nutritional Value of Milk :Nutritional Value of Milk :

• Almost complete diet for infant • Deficient in : vit K , C + Fe , Cu

3 3 rd rd m citrus fruitm citrus fruit

66th th m soup ,egg yolkm soup ,egg yolk

ColorColor

• White ± yellowishyellowish ,opaque

carotenescarotenes( colostrum + cow’s milk)

• Emulsion of fat + colloidal state of proteins & Ca phosphate

ReactionReaction

• pH cow’s 6.66.6 ,human milk 7.07.0

• Good buffer( proteins ,HCO3-, PO4,)

• Used for hyperacidity

• Lipids

• Proteins

• Carbohydrate

• Minerals and vitamins

Composition of milkComposition of milk

• Human & cows about 3.5%

• Present in form of emulsion emulsion surrounded by a thin coat layer of (PL, cholesterol and proteins)

• TAG: 99 %,99 %, main palmitic, oleic, stearic acids

• Human milk 10% essential. F.A.

• Cow’s milk 10% butyric acid

Milk FatMilk Fat

Other lipids :

• Small amount of cholesterol, phospholipids, fat soluble vit. & carotenes

• RichRich in vit. A

• PoorPoor in vit. K fairfair in E

• Cow’s milk poor in D but human fair

Milk ProteinsMilk Proteins

• Human 1.2%1.2% , cow’s 3.5%3.5%

• Casien : 80% (cow’s),40% (human) ,

phosphoproteinphosphoprotein,

• Rich in methionine,

• Poor in cystine & cysteine

• Ppt at its pI (4.6)

• Not coagulable

Lactalbumin & Lactoglobulin (whey Lactalbumin & Lactoglobulin (whey protein)protein)

• Human 60% , Cow 20 %

• Separate in whey

• Heat coagulable

• High biological value

• Can’t ppt at pH 4.6

• Include Ɣ –globulin (ab.)

Other proteins

• Lactoferrin:

↑↑↑↑ absorption of iron in intestine

Contain enzymes e.g.

proteinases,

amylase,

peroxidase, catalase,

alkaline phosphatase

Lactose (most suitable sugar)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

• BacteriaBacteria

• Lactose Lactic acid ↓pH

• ↑ solubility & absorption of Ca , Mg 2, PO4 , Fe, Cu

• Inhibits growth of putrefactive bacteria

Milk Minerals & VitaminsMilk Minerals & Vitamins

• Human less in minerals than cow’s• RichRich in Ca , PO4 , K, Cl• FairFair amn. of Na & Mg• Both milk poorpoor in Fe & Cu but

human is richer• RichRich in vit A & B2

• PoorPoor in C & K• FairFair in others

Comparison Between Human & Comparison Between Human & Animal MilkAnimal 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•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

ColostrumColostrum• 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

• Fats are lower but with higherhigher fat soluble vitamins, carotenes (yellowish coloryellowish color )

• Easier to digest

• Lower lactose , less sweet & more suitable for new born

Some Milk ProductsSome 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

Milk ClottingMilk Clotting RenninRennin

• Casein paracasein (sol) +peptone –like

• Paracasein + Ca 2+ insoluble Ca para.

ppts entangling fat + fat soluble vit.

milk clot or cheesemilk clot or cheese

WheyWhey :

• greenish yellow (riboflavin) in color contains

water &

water soluble vitamins,

lactalbumin, lactaglobulins,

lactose,

minerals,

reduced Ca content

Milk CurdlingMilk Curdling• It is the precipitation of casein

at its isoelectric pH, (pH =4.6)

• Produced by the action of action of lactobacillus acidophiluslactobacillus acidophilus

• Fermenting lactose

• Casein ppts + fats + fat soluble vit. to form curds or yogurt

WheyWhey of the milk curds

contains

less less lactoselactose

moremore B- vitamins( produced by bact.)

moremore calcium (not ppt with casein)

Advantages of colostrum for Advantages of colostrum for babybaby

• Highly nutrititve: high proteins and minerals

• High antibody contents; mainly gamma globulins which give immunity

• Laxative effect : which prevents constipation