This document summarizes various protein sources, including animal proteins from milk, meat, fish, and eggs as well as plant proteins. Milk proteins are divided into casein and whey proteins like lactalbumin and lactoglobulin. Meat proteins include myofibrillar, stromal, and sarcoplasmic proteins. Fish proteins contain myosin, actin, and soluble muscle enzymes. Egg proteins are found in egg whites as ovalbumin and in egg yolks as livetin and phosvitin. Proteins are an essential part of the human diet and are used in the body for growth, repair, and maintenance.
5. Milk proteins
The proteins of cows milk can be divided into
two groups :-
Casein
Milk serum
Casein
Which are phosphoproteins and comprises 78%
Of the total weight
6. Cont
Casein is defined as heterogeneous group of
phosphoproteins precipitated from skim milk
at pH 4.6 and 20属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.
7. 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
8. 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 milks total weight is non
protein nitrogen (NPN) containing substances, and
these includes peptides and amino acids.
9. Skim milk
pH at 4.6 rennin heat (85-95属C)
(lactic acid
bacteria) Casein calcium chloride
curd (de wheying)
Casein curd high calcium
(de wheying) rennet (de wheying)
acid casein
casein co- precipitate
11. 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.
12. 3 categories of meat proteins
1. myofibrillar (contractile)
55% of total muscle protein
salt soluble with ionic strength of over 0.3
needed
2. 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.
13. 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
14. 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.
15. 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.
16. 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.
17. 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.
18. 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.
19. Egg yolk
Egg yolk proteins precipitates
the yolk is diluted with
water.
The protein component
of egg yolk are like livetin,
phosvitin, lipoproteins etc.
Egg yolk contains considerable amount of
lipids.
Lipoproteins are the excellent emulsifiers.
20. 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属C to -14属C.