Food
Safety
MILK COMPOSITION
Milk is the food which exclusively sustains us
during the first few months of life.
Major constituents
Water
82 – 88 % TS %
12 -18%
Cow 3 -3.7 %
Buffalo 5.5 – 9 %
Fat
3 - 3.7 % SNF %
Protein
Cow 8.5 %
4.5 -5 % Buffalo 8.75 %
Lactose
Minerals
0.7 - 0.9 %
Minor constituents
Milk is considered as a complete diet as
It contains all of the components necessary for growth,
maintenance of life and reproduction.
e.g:
Carbohydrates, Lipid, Protein, Some minerals and Vitamins.
But it is deficient in:
Vitamin C, Vitamin D, Vitamin K, Iron, Copper.
major component
water protein
fat carbohydrates
Major Constituents of Milk
1- water:
- Water is the most important diluent of food solids. As a non-nutrient
component, water in foods has several effects on physical
properties, on food behavior in processing, on microbial growth,
stability, palatability and overall quality.
- Water forms about 80~88% of milk constitutes.
- Water availability, temperature & pH are the most important factors that
control rates of deteriorative changes and the growth of
microorganisms in foods.
2- Protein:
• Milk protein less in human than in cow's milk.
• All milk protein synthesized in the mammary gland.
• Milk protein of high coefficient digestibility (85 – 95%)
Characterized by:
1- Protein of high biological value as:
• It contains all essential amino acids.
• Easily digested.
• Easily absorbed.
• Easily metabolized.
2- Contain moderate amount of non essential amino acids to
decrease stress on body cells.
3- Essential to keep positive nitrogen balance (nitrogen intake more
than nitrogen output).
5- Essential to maintain growth of newborn.
Types of Milk Proteins are:
1. Casein.
2. Whey protein
- Lactalbumin.
- Lactglobulin..
Casein
• It is the main and most dominant milk protein.
• It represents 25% in human's milk and 83% in cow's milk.
• The high phosphate content of casein allows it to associate
with calcium and form calcium phosphate salts.
According to molecular weight and electrophoresis process, casein is separated
in to 3 fractions, each one of them has its own amino acid composition :
α Casein → 75%.
β Casein → 22%.
γ Casein → 3%.
Whey of milk curd
It is the residual clear fluid which formed after removal of
casein and contain:
» Water.
» Lactic acid.
» Lactalbumin & lactglobulin (whey protein)
» Minerals.
» Water soluble vitamins.
The greenish yellow color of whey is due to riboflavin (vitamin
B2)
Lactalbumin
• Represent 87% of whey protein.
• Rich in cystein and cystin
• Simple protein.
• Soluble protein.
• Easily digested.
• Consists of two fractions:
– α Lactalbumin 32% of whey protein.
– β lactglobulin 55% of whey protein.
Lactglobulin
Represent 13% of whey protein.
• Rich in cystein and cystin
• Simple protein.
• Soluble protein.
• Easily digested.
• Consists of two fractions:
– True globulin (Euglobulin) 50%.
– False globulin (Pseudoglobulin) 50%.
• They carry antibodies causing immunity so called immunoglobulins.
• They present in higher concentration in colostrum.
2- Fat
The fat in milk occurs in microscopic globules in an oil-in water type of emulsion.
The globules vary in size from 0.1 to 22 μm in diameter.
The lipid composition is illustrated in the next Table hich shows the most abundant
ratio of lipids is 96–98% triacylglycerols, 0.2–1% phospholipids, 0.2–0.4%
sterols, and traces of fatty acids, as well as vitamins A, D, E, and K.
The nature of emulsifying fat in milk is differ than
suspension of fat in water
What is the responsible for fat emulsion in milk?
• Milk fat is made up of 65% saturated, 32% monounsaturated,
and 3% polyunsaturated fatty acids.
• It contains
• 7% short-chain fatty acids (C4–C8),
• 15–20% medium-chain fatty acids (C10–C14),
• 73–78% long-chain fatty acids (C16 or higher).
• The cholesterol content of whole milk (3.3% fat) and skim milk
is 14 mg/100 ml and 2 mg/100 ml, respectively.
4- Carbohydrates
• Lactose (milk sugar) is the only carbohydrate of milk.
• It is a reducing disaccharide consists of glucose and galactose.
• Human's milk contains 7% lactose while cow's milk contains
5% lactose.
Importance of lactose
1. It is less sweet than sucrose so allow the baby to take large
amount of milk without causing nausea.
2. It is non fermentable carbohydrate so it doesn't produce CO2 in
GIT and the baby doesn't suffer from abdominal colic or
distention.
3. Lactose help growth of lactic acid bacteria, producing lactic
acid, so help in absorption of Ca, P, Fe, Cu which prefer acidic
medium for their absorption.
4. Lactose inhibits growth of putrefactive bacteria which cause
abdominal distention by increasing the acidity of the intestine.
5- Minerals:
• Human milk contain less mineral elements (0.4%) than cow's
milk (0.8%).
• Milk rich in Ca and P which are present in their proper ratio
for absorption (2:1) in human milk while in cow's milk (1:2)
which is not suitable for their maximum absorption .
• Ca and P are essential for:
1. Growth of bone and teeth.
2. Stability of casein.
• Milk is deficient in Fe and Cu which are supplied by their
storage in liver during prenatal life (this store is sufficient till
weaning time).
N.B:
Milk is deficient in Iron but it is more in human milk than cow's
milk Thus anaemia in breast feeding is less common.
• Milk contain adequate amount of Na, K, Mg.
• Human milk contains Na:K (1:2) which is suitable for the
optimal growth of newborn.
minor
component
vitamins gases pigments
salts and
enzymes
minerals
Minor components
vitamins :
1– fat soluble vitamins :
• A , D, E , K
2– water soluble vitamins :
• B,C
( fat soluble )
vitamin A :
• Helps maintain normal vision and skin
• Help to maintain a healthy immune system
• Deficiency cause night blindness
• Dairy product are a good source of vitamin A
vitamin D :
• Cancer protection
• Help to protect children from rickets and aldults from
osteoporosis
• Deficiency has been associated with depression and
chronic fatigue
• Fortified milk is a good source of vitamin D
vitamin E :
• Has antioxidant activity , protect lipid
• Milk contain a small amount of vitamin E
vitamin K :
Involved in blood clotting , bone metabolism and
protein system
Milk contain a small amount of vitamin K
( water soluble )
vitamin C :
• An important antioxidant
• Has role in collagen formation in connective tissue
• Helps in iron absorption , helping wounds and
injuries
• There is a negligible amount of it in milk
vitamin B :
• B1 , ( thiamin ) , B2 ( riboflowin ) , B3 ( naicin ) ,
B5 ( pantothenic Acid) , B12( coalmine)
• Enzyme cofactor .
• Milk is good source of thiamin's B2 , B5 , B12 , but
have a small amount of niacin
• Deficiencies in B vitamins may constitute risks
factors for vascular and neurological diseases and
cancer
• Lactic acid bacteria ( L A B) are used to increase the
production levels of vitamin B in dairy product
Enzymes :
A number of enzymes have been reported to be present in milk
1– lipases :
• Are enzymes that degrade fats the major lipase in milk is
lipoprotein lipase , associated with casein micelle
• Agitation during processing may bring the lipase into
contact with the milk fat resulting in fat degradation and
off flavors
• Pasteurization will inactivate the lipase and increases
shelf life of milk
2– proteases :
• are enzymes that degrade protein
• Protein degradation can be undesirable and result in
bitter off flavors , or it may provide a desirable texture to
cheese during ripening
3– alkaline phosphates :
• is a heat sensitive enzyme in milk that is used as
indicator of pasteurization
4– lacto peroxides :
• the most heat sensitive enzyme when combined with
hydrogen peroxide and thiocyanate : has antibacterial
properties
• It is suggested that the presence of it raw milk inhibits the
disease causing microorganisms ( pathogens )
present in milk
5– lysozyme :
• is another enzyme that has some antibacterial activities ,
although the amount present in milk is very small
pigments
• Water soluble pigment :
• which imparts a yellow color with a green fluorescence
to the whey of milk , was formerly called lacto chrome
(lactoflavin )
• The fat soluble pigment :
• carotene it found in the fat gives the milk a more or less
yellow tinge , which is more pronounced as the fat
particles become more concentrated and form cream
• Yellow milk of cow is due to lower efficiency of
conversion of B carotene or retinol
Gases
• During hand milking , foaming is produced which results
in the loss of 50 % of the total gases present in milk
• When the milk is exposed to atmosphere there is a shift in
the pattern of co2 and o2
• Co2 escapes out and o2 and nitrogen gain entry into milk
salts
• The milk salts composition is influenced by a
number of factor including species , breed , stage of lactation,
health status , climate and feed
• In addition to the major salts e.g phosphates , citrates ,
chlorides , sulphates and carbonates , milk also contain trace
elements , some elements come into milk from feed
• Calcium , prevent osteoporosis . Help build
and maintain strong bones and teeth ( good source )
• Potassium , sodium important in the maintenance of water
balance blood volume and blood pressure ( good source )
• Increasing potassium intake and decreasing sodium can
reduce the risk of cardio vascular disease
• Selenium , important in oxidative stress response and
regulation of thyroid hormone
• Phosphorous , generates energy in your body's cell .
