SOURCES OF PROTEINS…..

BY:- KETAKI PATIL

• Animal proteins • Plant proteins

Animal protein

• Milk proteins • Meat proteins • Fish proteins • Egg proteins

Milk proteins

• The proteins of cow’s milk can be divided into two groups :-

• Casein • Milk serum

Casein Which are phosphoproteins and comprises 78%Of the total weight

Cont…• Casein is defined as heterogeneous group of

phosphoproteins precipitated from skim milk at pH 4.6 and 20°C.

• The proteins remaining in solution, the serum or whey proteins, can be separated into classic lacto globulin and lactalbumin fractions by half saturation with ammonium sulphate or by full saturation with magnesium sulphate.

• The whey protein is composed of lactalbumin and lacto globulin.

• lactalbumin contains a protein with the characteristics of a globulin, this protein known as B-lacto globulin and it is the most abundant whey proteins.

• It has molecular weight of 36,000• It is rich in lysine, leucine, glutamic acid &

aspartic acid

Milk serum proteins:-which make up 17% of the total weight .

The later group includes B- lacto globulin (8.5%), A lactalbumin (5.1%), Immune globulins (1.7%), &

serum albumins .

In addition, about 5% of milk’s total weight is non protein nitrogen (NPN) containing substances, and these includes peptides and amino acids.

Skim milk

pH at 4.6 rennin heat (85-95°C)(lactic acid bacteria) Casein calcium chloride curd (de wheying)

Casein curd high calcium (de wheying) rennet (de wheying)

acid casein casein co- precipitate

Caseinate whey

heat aggregation ultra filtration ion- exchange

lactalbumin whey protein whey protein conc. isolate

Meat proteins

• The proteins of muscle consist of about 70% structural or fibrillar proteins and about 30% water soluble proteins.

• The fibrillar proteins contain about 32 to 38% myosin, 13 to 17% actin, 7% tropomyosin, & 6% stroma proteins.

• 3 categories of meat proteins • 1. myofibrillar (contractile)– 55% of total muscle protein– salt soluble with ionic strength of over 0.3

needed2. Stromal proteins (connective tissue)

10 - 15% of total muscle protein primarily collagen.most abundant protein in animal body (20 -

25% of total body protein) - skin, sinews, tendons, etc.

3. Sarcoplasmic proteins (water soluble, intracellular fluid)

30% of total muscle protein ( 20% of binding ability)

– isoelectric points generally between pH 6 - pH 7

– hundreds of enzymes in cells for energy, growth,

etc.

– most are relatively low molecular weight (small)

proteins

Myoglobin

“conjugated” protein consists

of a typical amino acid protein

chain and a non-protein heme

molecule.

Heme portion

• Responsible for all color. Heme

is attached to the protein by a

histidine amino acid.

Fish protein

• The protein of fish flesh can be

divided into groups on the basis of

solubility.

• The skeletal muscle of fish consist of

short fibers arranged between sheets

of connective tissue in fish muscle is

less than in mammalian tissue.

• The myofibril of fish contains some important proteins myosin, actin, actomyosin & tropomyosin.

• The soluble proteins include most of the muscle enzymes and account for about 22% of the total protein

• During the frozen storage the actomyosin becomes progressively less soluble & the flesh becomes increasingly tough.

Egg proteins

• The proteins of egg are characterized by their high biological value and can be divided into the egg white and egg yolk proteins.

• The egg white contains at least eight different proteins like ovalbumin, conalbumin, lysozymes, avidin,ovamucin, non protein etc.

• Biological value of egg is 100• Liquid egg white contains 10-

11% of protein• The dried form contains about

83%. • Most abundant protein is

ovalbumin, a phosphoprotein with a mol.wt. of 45,000 that contains small portion of carbohydrate.

Egg yolk

• Egg yolk proteins precipitatesthe yolk is diluted withwater. • The protein componentof egg yolk are like livetin,phosvitin, lipoproteins etc.• Egg yolk contains considerable amount of lipids.• Lipoproteins are the excellent emulsifiers.

Cont…

• When fluid egg yolk is frozen, changes take place, causing the thawed yolk to form a gel .

• Gelation increases as the freezing temperature is lowered from

-6°C to -14°C.

How Proteins are used in the body

…Thank you….