Notes on milk proteins types and the forms on which each type present with illustrating the different charges in different pH.

1. Notes on
Milk proteins composition

2. Milk
Water 87.5% Total solids (T.S) 12.5%
Solid not fat (SNF)
True fat(TG 98%)Associated fat 2% Protein3.3%
Lactose 4.7%
Miscellanies
Casein80% Whey pt 14-24%
Minerals
Vitamine
Gasses
enzyme
Bacteria
Alpha,
Beta,
Kappa
Heat labile
Heat stable
Sterols
Phospholipids
Cartenoid
Fat sol.vit
Free fatty acids
2
Fat 3.4%

3. Milk proteins 3.3% (33g/l)
Nitrogenous substances
Creatine , creatinine Casein 80% (26 g/l)
FGM protein 0.04%(0.4 g/l)
Whey pt 20%(6.5-7 g/lAmmonia, urea
Non nitrogenous substances (NPN)
Colloidal
suspension
Colloidal
solution
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4. 1- Small size particles 2- Electrically charged 3- Hydrophilic
N.B. Hydrophilic (water loving) has affinity for water , salt can destabilize the colloidal
system by changing the water binding &reducing protein solubility.
Milk proteins
Typical characters of a colloid
Milk proteins are synthesized in the mammary
gland, but 60% of the amino acids used to build
the proteins are obtained from the cow's diet.
Total milk protein content and amino acid
composition varies with cow breed and individual
animal genetics.
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5. Milk proteins Milk contains 3.3% total protein.
The casein family contains
phosphorus and will coagulate
or precipitate at pH 4.6.
The serum (whey) proteins do not
contain phosphorus, and these
proteins remain in solution in milk at
pH 4.6.
Milk contains all essential amino
acids (that can not be synthesized
by human body and should be
supplemented in Food (9-20 a.a).
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6. Character of Milk proteins
The basic unit of each protein is amino acids which contain
both basic amino groub (NH2)and slightly acidic carboxyle
group (CooH) called amopholytes
Milk proteins carrying electric charge which determined by the PH of milk.
PH= 1.00
The protein molecule has
a net zero charge so,
positive and negative
charges are equal so
attraction and precipited.
The protein molecule has
a net positive charge so,
remains seperated – so
milk remains in a solution.
PH= 4.6 PH= 10.00
The protein molecule has
a net negative charge so,
remains seperated – so
milk remains in a solution.

7. PH= 4.5 which called iso-electric point (curd formation)
PH= 4.5
No. Of positive charges =No. Of
negative charges = zero
So, positive charge on one molecule link up
with negative charge on neighbouring
molécule to form clusters (ppt).
1- Negatively charged in alkaline solution.
2- Positively charged in aidic PH.
3- Neutral at iso-electric point .
The amphoteric properties of protein
means the ability of a.a to absorb hydrogen
ions in acidic solution and emit hydrogen in
alkaline solution.
So, amino acids appears in three states:
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8. Thank you for attention
Presented by :
Dr. Dina A. B. Awad
Lecturer of food hygiene department
Faculty of veterinary medicine
Benha university , Egypt