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Milk
Milk is one of the most hygenic food available to mankind, it is most nearly perfect food. Though, it is no longer considered as perfect food as it was then. The term perfect food is used for food which can fulfill all nutritional requirements of human being. Modern research has shown that the need of human body are very complex. It requires more than thirty distinct material in its food supply. No single food stuff supplies all of them. Milk is the only food which supplies nearly all of them. To illustrate the food value of milk it may be pointed out that animals live on milk alone during most rapid period of growth. It may be further pointed out that an infant may double its birth weight in single week while living exclusively on its mother's milk. In view of these facts it is not surprising that milk was once considered as perfect food. The imperfection of milk as food become apparent when an attempt was made to raise the animals to maturity on milk alone, it was observed that animals grew well for a time eventually they become anemia, become sick and ultimately died. It is now admitted that milk lacks sufficient quantity of several elements which are necessary for normal growth and maintenance of human body. Since, then milk is considered to be most nearly perfect food.
Defination of Milk
Milk may be defined as whole, clean, lacteral secretion obtained by complete milking of one or more healthy milch animal, properly fit and excluding that obtained 15 days before and 5 days after cowing. It shall confirm to the standards that lie under FSSAI.
Milk may be defined as whole, clean, lacteral secretion obtained by complete milking of one or more healthy milch animal, properly fit and excluding that obtained 15 days before and 5 days after cowing. It shall confirm to the standards that lie under FSSAI.
Constituents of Milk
1. Water
2. Fat
3. Protein
4. Lactose
5. Ash (Mineral Salts)
1. Water
2. Fat
3. Protein
4. Lactose
5. Ash (Mineral Salts)
Fat free fraction of milk i.e., constituents of serum/skim milk are: water, protein, lactose and ash.
Constituents of Total Solids: fat, protein, lactose, ash
Constituents of SNF: protein, lactose, ash.
1. Water: Water varies 84-89%, however a individual sample may exceed the unit. The water present is not different with ordinary water. In milk water may be said to be colloidal dispersion medium for the solid constituent of milk. It serves as a continous phase. Generally, water exists in three different states of dispersion:
(i) Course dispersion/Emulsion State: 0.0001 mm
(ii) Colloidal Dispersion: 0.0001 - 0.000001 mm
(iii) Molecular Dispersion/ Free solution State: less than 0.000001 mm
2. Fat: It is also known as butter fat. It is commercially the most valuable constituent of milk. It is also of great importance from the view point of value of milk. 1 gram of fat contains 4.11 kilocalories. On average, the fat is present in milk in the state of emulsion and it is found in the form of globules. the size of fat globules normally varies from 2 to 10 micrometer depending upon species and breed of animal, kind of food given to animal and the stage of the lactation. The specific gravity of fat is 0.93 at 60 degree Fahrenheit. Milk fat is a mixture of glycrides and soluble fatty acids:
(a) Butylic Acid
(b) Caproic Acid
(c) Caprylic Acid
(d) Capric Acid
(e) Lauric Acid
(f) Myristic Acid
(g) Steoric Acid
(h) Oleic Acid
3. Proteins: It is the most complex organic substance. These are the muscle building components. Proteins contain nitrogen, carbon, hydrogen, sulphur, some times phosphorus. 1 gram of protein furnishes around 4.27 kilocalories. Proteins are normally present in the state of colloidal dispersion. Milk contains the three proteins:
(a) Caseim: 80%
(b) Lactolbumin: 15%; Albulum
(c) Lactoglobium: 5% Globulin
Albulum and Globulin combined are said to be Whey Protein.
4. Caseim: It is the most important protein in the milk. Being present in the largest amount it can be formulated by acid on enzyme lactolbumin. It occur in milk in the state of sol and it is cogulated by heat and not by acid. The cogulation of lactolbumin starts about 70 degree Celcius.
Lactoglobium: Normally, milk contains about 0.05% which is approximately 5% of total protein. Bad in colestrum, its content is as high as 12%.
5. Lactose: It is also known as milk sugar which is only found in milk. It is only present as true solution. Energy value of lactose is 3.95 kilocalories. The sweet taste of milk is due to lactose content. It is converted into lactic acid by acid forming bacteria and milk is crystallated when acidity reaches certain point. It is the carbohydrate which is present.
6. Ash: White ash is milk and is composed of oxides and chlorides of mineral elements present in milk. It is composed of following components: Calcium oxides, Magnesium oxides, Nitrogen oxides, Phosphorous peroxide.
1. Water: Water varies 84-89%, however a individual sample may exceed the unit. The water present is not different with ordinary water. In milk water may be said to be colloidal dispersion medium for the solid constituent of milk. It serves as a continous phase. Generally, water exists in three different states of dispersion:
(i) Course dispersion/Emulsion State: 0.0001 mm
(ii) Colloidal Dispersion: 0.0001 - 0.000001 mm
(iii) Molecular Dispersion/ Free solution State: less than 0.000001 mm
2. Fat: It is also known as butter fat. It is commercially the most valuable constituent of milk. It is also of great importance from the view point of value of milk. 1 gram of fat contains 4.11 kilocalories. On average, the fat is present in milk in the state of emulsion and it is found in the form of globules. the size of fat globules normally varies from 2 to 10 micrometer depending upon species and breed of animal, kind of food given to animal and the stage of the lactation. The specific gravity of fat is 0.93 at 60 degree Fahrenheit. Milk fat is a mixture of glycrides and soluble fatty acids:
(a) Butylic Acid
(b) Caproic Acid
(c) Caprylic Acid
(d) Capric Acid
(e) Lauric Acid
(f) Myristic Acid
(g) Steoric Acid
(h) Oleic Acid
3. Proteins: It is the most complex organic substance. These are the muscle building components. Proteins contain nitrogen, carbon, hydrogen, sulphur, some times phosphorus. 1 gram of protein furnishes around 4.27 kilocalories. Proteins are normally present in the state of colloidal dispersion. Milk contains the three proteins:
(a) Caseim: 80%
(b) Lactolbumin: 15%; Albulum
(c) Lactoglobium: 5% Globulin
Albulum and Globulin combined are said to be Whey Protein.
4. Caseim: It is the most important protein in the milk. Being present in the largest amount it can be formulated by acid on enzyme lactolbumin. It occur in milk in the state of sol and it is cogulated by heat and not by acid. The cogulation of lactolbumin starts about 70 degree Celcius.
Lactoglobium: Normally, milk contains about 0.05% which is approximately 5% of total protein. Bad in colestrum, its content is as high as 12%.
5. Lactose: It is also known as milk sugar which is only found in milk. It is only present as true solution. Energy value of lactose is 3.95 kilocalories. The sweet taste of milk is due to lactose content. It is converted into lactic acid by acid forming bacteria and milk is crystallated when acidity reaches certain point. It is the carbohydrate which is present.
6. Ash: White ash is milk and is composed of oxides and chlorides of mineral elements present in milk. It is composed of following components: Calcium oxides, Magnesium oxides, Nitrogen oxides, Phosphorous peroxide.
In addition to five major constituents. There are some more constituents present/embedded in minute quantities.
Minor constituents of milk are:
1. Vitamins:
(a) Fat soluble vitamins: Vitamin A, Vitamin D, Vitramin E and Vitamin K.
(b) Water soluble vitamins: Vitamin B1, Vitamin B2, Vitamin B6, Vitamin B12 and Vitamin C
2. Gases:
Freshly drawn milk contains about 7 to 10% by volume of dissolved gases. Carbon dioxide is present in largest quantity others are Nitrogen and Oxygen. These gases are absorbed during the milking from atmosphere/air. Carbon dioxide content decreases rapidly after milking, gases may also develop by bacterial fermentation in old and dirt milk.
3. Enzymes:
Catalytic substances secreted by living sense are known as enzymes. Some enzymes originate from animal cell and some from bacteria. Presence of enzymes give useful information about physiological condition and bacteriological quality of milk. Principle enzymes found in milk are:
(a) Amylase
(b) Catalase
(c) Galactase
(d) Lipase
(e) Deroxidase
(f) Phosphatase
(g) Reductase
4. Pigments:
Pigments are colouring substance. In milk there are two types of pigments:
(a) Fat soluble pigments: Carotene, Xanthophyl, etc.
(b) Water solube pigments: Riboflvine, Lactocromes, etc.
Minor constituents of milk are:
1. Vitamins:
(a) Fat soluble vitamins: Vitamin A, Vitamin D, Vitramin E and Vitamin K.
(b) Water soluble vitamins: Vitamin B1, Vitamin B2, Vitamin B6, Vitamin B12 and Vitamin C
2. Gases:
Freshly drawn milk contains about 7 to 10% by volume of dissolved gases. Carbon dioxide is present in largest quantity others are Nitrogen and Oxygen. These gases are absorbed during the milking from atmosphere/air. Carbon dioxide content decreases rapidly after milking, gases may also develop by bacterial fermentation in old and dirt milk.
3. Enzymes:
Catalytic substances secreted by living sense are known as enzymes. Some enzymes originate from animal cell and some from bacteria. Presence of enzymes give useful information about physiological condition and bacteriological quality of milk. Principle enzymes found in milk are:
(a) Amylase
(b) Catalase
(c) Galactase
(d) Lipase
(e) Deroxidase
(f) Phosphatase
(g) Reductase
4. Pigments:
Pigments are colouring substance. In milk there are two types of pigments:
(a) Fat soluble pigments: Carotene, Xanthophyl, etc.
(b) Water solube pigments: Riboflvine, Lactocromes, etc.
Physio-Chemical Proprties of Milk
1. Flavour and Taste: Milk produced under proper condition has slightly sweet taste and mild aromatic flavour. Sweet taste principally comes from lactose. Typical flavour and aroma is due to milk fat. Flavour and taste are readly affected by unclean surrounding and feeding of animals.
2. Colour of Milk: Milk ranges in colour from Bluish-white to Golden-white depending upon the breed of animals, kind of feed given to animal, amount of fat and solid present in the animal. Cow milk is usually yellowish-white in colour, whitness is due to suspended particle of casein and fat but mainly due to caseim. After removal of fat from cow milk it is known as skimmed milk or serum which is slightly bluish. After removal of caseim from serum the remainder known as whey which is slightly greenish-white in colour.
3. Viscosity of Milk: Viscosity of fluid is its resistance of flow, shear or agination. It is expressed in terms of centipoise which is a unit of force. Viscoity of water is 1.005 centipoise at 20 degree Celcius. Viscosity of milkm is approximately 1.5 to 1.7 times more viscous than water due to presence of fat emulsion and colloidal dispersed particle of caseim. Homogenization increases viscosity and addition of water reduces viscosity of milk. Normally, viscosity of milk varies from 1.5 to 2.0 centipoise.
4. Specific Gravity of Milk: Specific gravity of milk means the weight of a given volume of milk as compared with weight of equal volume of water at same temperature. Specific gravity of milk varies with the temperature, with increase in temperature specific gravity is decreased and vice-versa. It is therefore necessary to record specific gravity of milk at standard temperature. The standard temperature used to find specific gravity of milk is 15.6 degree Celcius or 60 degree Fahrenheit. Milk is a complex colloidal system in which the dispersion medium water contain salt and sugar in solution. It is therefore heavier than water.
Specific gravity of mixed milk varies from 1.028 - 1.034.
Specific gravity of cow milk varies from 1.028 - 1.032.
Specific gravity of buffalo milk varies from 1.030 - 1.036.
Specific gravity of milk influenced by its constituents as each individual content of milk posses a different specific gravity.
Specific gravity of Water = 1
Specific gravity of Fat = 0.93
Specific gravity of Protein = 1.346
Specific gravity of Lactose = 1.666
Specific gravity of Ash = 4.12
Since, the fat is the lightest constituent of milk its removal from milk increases specific gravity. Simultaneously, adding fat to milk decreases specific gravity. Addition of water decreases specific gravity. Addition of water decreases specific gravity and addition of sugar and salt increases specific gravity.
Specific Gravity of Milk = Weight of Unit Volume of Milk/Weight of Unit Volume of Water at same Temperature.
For every 1 degree increase in temperature 0.1 is added to lactometer reading and vice-versa.
Specific Gravity of Milk = 1 + CLR/1000.
5. Freezing Point of Milk: Freezing point of water is the temperature at which ice and water exist in equillibrium with each other or it is a temperature at which ice and water both have the same vapour pressure. Addition of solute to water lowers the vapour pressure because it hinders the ability of water molecules to escape from the surface. Thus, happens that, ice and solution will be at equillibrium at lower pressure than pure water and ice. The freezing point of milk depends upon lactose content and solube mineral salts of milk. Freezing of milk tends to be constant irrespective of changes in fat and protein content. Freezing point of milk is lower than that of water. Water freezes at 0 degree Celcius.
Freezing Point of Cow Milk = -0.544 degree Celcius.
Freezing Point of Buffalo Milk = -0.542 degree Celcius.
Freezing Point of Mixed Milk = -0.544 degree Celcius.
Freezing point of milk has an influence on checking the adultration of milk in water. Approximately, each 0.01 degree above change in freezing point of milk indicates 2% added water. Amount of water can be calculated bu formula.
w = [(t - t')/t]100.
where, w is percentage added water
t is minimum freezing point
t' is freezing point of milk.
6. Boiling Point of Milk: Milk is slightly hevier than water. Since the boiling point is influenced by the factors responsible for its specific gravity. Milk boils at 100 degree Celcius or 212 degree Fahrenheit at sea level and average milk boils at 100.17 degree Celcius or 212.3 degree Fahrenheit. The variation in the boiling point of milk are very little. Therefore, they are of little practical importance.
7. Refractive Index of Milk: The degree of refraction of light in milk serum as compared with that of air is called refractive index of milk. Refractive index of milk is 1.35 and that of water is 1.33, it is denoted by η.
η = sin i/sin r
8. Specific Heat of Milk: The ratio between amount of heat required to raise a given weight of substance to given temperature and the amount of heat required to raise same amount of water to the same temperature is termed as specific heat. Specific heat of milk ranges between 0.92 to 0.93. It changes with the temperature. Milk has highest specific heat of 0.938 at 15 degree Celcius. However, an average value of 0.93 is used if the temperature ois not specified.
9. Electrical Conductivity of Milk: In a pure solution the conductivity is a function of ionic concentration. If a hetrogenous system such as exists in milk the fat and colloidally dispersed particles of casiem obstruct the ions in their migration and decrease the conductivity. The electrical conductivity increases with the increase in temperature and vice-versa. The average electrical conductivity of cow milk at 30 degree Celcius is 4.67 millimole/cm and 3.67 millimole/cm for buffalo milk.
10. Surface Tension: Surface tension of milk varies with the temperature and total solid content of milk. Surface tension of milk at 20 degree Celcius is 54.5 dyne/cm and at 15.6 degree Celcius (60 degree Fahrenheit) it varies between 40 - 45 dyne/ cm.
11. Chemical Reaction of Milk: When mik is freshly drawn from the animal it shows an amphoteric reaction. This reaction is just because of Protein since it contains both Carboxyl as well as Ammino group.
12. pH of Milk: pH of normal milk ordinarlly falls betwwen 6.5 - 6.7. Values higher than 6.7 usually denotes/indicates the mustitic condition of the udder of animals and values below 6.5 indicates the presence of colestrum in milk of poor quality.
13. Acidity of Milk: Fresh milk is slightly acidic in nature but it doesn't contain any lactic acid. Acidity of milk is of two types:
(a) Natural or Apparent Acidity: Natural acidity in milk is largely due to the presence of phosphates and citrates of mineral elements, protein and carbon dioxide. Like any free acids these components have power to neutralize alkalies. The normal acidity of milk varies between 0.1 - 0.2% with an average of 0.15%. The natural acidity of colestrum is 0.4%.
(b) Developed Acidity: Developed acidity is developed in milk after it is drawn from the animal. This is due to action of certain bacteria on milk sugar. It can safely be declared that a sample of milk contains some lactic acid if the acidity of 0.3% and spontenously cogulates when acidity goes beyond 0.6%.
1. Flavour and Taste: Milk produced under proper condition has slightly sweet taste and mild aromatic flavour. Sweet taste principally comes from lactose. Typical flavour and aroma is due to milk fat. Flavour and taste are readly affected by unclean surrounding and feeding of animals.
2. Colour of Milk: Milk ranges in colour from Bluish-white to Golden-white depending upon the breed of animals, kind of feed given to animal, amount of fat and solid present in the animal. Cow milk is usually yellowish-white in colour, whitness is due to suspended particle of casein and fat but mainly due to caseim. After removal of fat from cow milk it is known as skimmed milk or serum which is slightly bluish. After removal of caseim from serum the remainder known as whey which is slightly greenish-white in colour.
3. Viscosity of Milk: Viscosity of fluid is its resistance of flow, shear or agination. It is expressed in terms of centipoise which is a unit of force. Viscoity of water is 1.005 centipoise at 20 degree Celcius. Viscosity of milkm is approximately 1.5 to 1.7 times more viscous than water due to presence of fat emulsion and colloidal dispersed particle of caseim. Homogenization increases viscosity and addition of water reduces viscosity of milk. Normally, viscosity of milk varies from 1.5 to 2.0 centipoise.
4. Specific Gravity of Milk: Specific gravity of milk means the weight of a given volume of milk as compared with weight of equal volume of water at same temperature. Specific gravity of milk varies with the temperature, with increase in temperature specific gravity is decreased and vice-versa. It is therefore necessary to record specific gravity of milk at standard temperature. The standard temperature used to find specific gravity of milk is 15.6 degree Celcius or 60 degree Fahrenheit. Milk is a complex colloidal system in which the dispersion medium water contain salt and sugar in solution. It is therefore heavier than water.
Specific gravity of mixed milk varies from 1.028 - 1.034.
Specific gravity of cow milk varies from 1.028 - 1.032.
Specific gravity of buffalo milk varies from 1.030 - 1.036.
Specific gravity of milk influenced by its constituents as each individual content of milk posses a different specific gravity.
Specific gravity of Water = 1
Specific gravity of Fat = 0.93
Specific gravity of Protein = 1.346
Specific gravity of Lactose = 1.666
Specific gravity of Ash = 4.12
Since, the fat is the lightest constituent of milk its removal from milk increases specific gravity. Simultaneously, adding fat to milk decreases specific gravity. Addition of water decreases specific gravity. Addition of water decreases specific gravity and addition of sugar and salt increases specific gravity.
Specific Gravity of Milk = Weight of Unit Volume of Milk/Weight of Unit Volume of Water at same Temperature.
For every 1 degree increase in temperature 0.1 is added to lactometer reading and vice-versa.
Specific Gravity of Milk = 1 + CLR/1000.
5. Freezing Point of Milk: Freezing point of water is the temperature at which ice and water exist in equillibrium with each other or it is a temperature at which ice and water both have the same vapour pressure. Addition of solute to water lowers the vapour pressure because it hinders the ability of water molecules to escape from the surface. Thus, happens that, ice and solution will be at equillibrium at lower pressure than pure water and ice. The freezing point of milk depends upon lactose content and solube mineral salts of milk. Freezing of milk tends to be constant irrespective of changes in fat and protein content. Freezing point of milk is lower than that of water. Water freezes at 0 degree Celcius.
Freezing Point of Cow Milk = -0.544 degree Celcius.
Freezing Point of Buffalo Milk = -0.542 degree Celcius.
Freezing Point of Mixed Milk = -0.544 degree Celcius.
Freezing point of milk has an influence on checking the adultration of milk in water. Approximately, each 0.01 degree above change in freezing point of milk indicates 2% added water. Amount of water can be calculated bu formula.
w = [(t - t')/t]100.
where, w is percentage added water
t is minimum freezing point
t' is freezing point of milk.
6. Boiling Point of Milk: Milk is slightly hevier than water. Since the boiling point is influenced by the factors responsible for its specific gravity. Milk boils at 100 degree Celcius or 212 degree Fahrenheit at sea level and average milk boils at 100.17 degree Celcius or 212.3 degree Fahrenheit. The variation in the boiling point of milk are very little. Therefore, they are of little practical importance.
7. Refractive Index of Milk: The degree of refraction of light in milk serum as compared with that of air is called refractive index of milk. Refractive index of milk is 1.35 and that of water is 1.33, it is denoted by η.
η = sin i/sin r
8. Specific Heat of Milk: The ratio between amount of heat required to raise a given weight of substance to given temperature and the amount of heat required to raise same amount of water to the same temperature is termed as specific heat. Specific heat of milk ranges between 0.92 to 0.93. It changes with the temperature. Milk has highest specific heat of 0.938 at 15 degree Celcius. However, an average value of 0.93 is used if the temperature ois not specified.
9. Electrical Conductivity of Milk: In a pure solution the conductivity is a function of ionic concentration. If a hetrogenous system such as exists in milk the fat and colloidally dispersed particles of casiem obstruct the ions in their migration and decrease the conductivity. The electrical conductivity increases with the increase in temperature and vice-versa. The average electrical conductivity of cow milk at 30 degree Celcius is 4.67 millimole/cm and 3.67 millimole/cm for buffalo milk.
10. Surface Tension: Surface tension of milk varies with the temperature and total solid content of milk. Surface tension of milk at 20 degree Celcius is 54.5 dyne/cm and at 15.6 degree Celcius (60 degree Fahrenheit) it varies between 40 - 45 dyne/ cm.
11. Chemical Reaction of Milk: When mik is freshly drawn from the animal it shows an amphoteric reaction. This reaction is just because of Protein since it contains both Carboxyl as well as Ammino group.
12. pH of Milk: pH of normal milk ordinarlly falls betwwen 6.5 - 6.7. Values higher than 6.7 usually denotes/indicates the mustitic condition of the udder of animals and values below 6.5 indicates the presence of colestrum in milk of poor quality.
13. Acidity of Milk: Fresh milk is slightly acidic in nature but it doesn't contain any lactic acid. Acidity of milk is of two types:
(a) Natural or Apparent Acidity: Natural acidity in milk is largely due to the presence of phosphates and citrates of mineral elements, protein and carbon dioxide. Like any free acids these components have power to neutralize alkalies. The normal acidity of milk varies between 0.1 - 0.2% with an average of 0.15%. The natural acidity of colestrum is 0.4%.
(b) Developed Acidity: Developed acidity is developed in milk after it is drawn from the animal. This is due to action of certain bacteria on milk sugar. It can safely be declared that a sample of milk contains some lactic acid if the acidity of 0.3% and spontenously cogulates when acidity goes beyond 0.6%.
Factors affecting Composition of Milk
There is a great deal of composition variation in the milk. No two animals give milk in same composition if a number of milk samples ar collected from different sources and subjected to careful analysis. It is probable that no two samples shows exactly same composition. The composition The composition of milk of same cow is not always same. The composition of milk varies because of the various reasons. Among the constituents of milk fat content is most variable after fat content varies in following protein, lactose and ash.
The factor which are responsible for the variation in the composition of milk are:
a) Individuality of Animal: Animals belonging to the particular breed produce milk with different composition. Although they are kept under the similar condition and given exactly same feed. Milk produced by these animals in different composition such, difference in composition of milk are attribute to individual difference in animal. The heridity character may be the reason for such variation.
b) Breed: The breed is one of a most important factors influencing the composition of milk of some breeds of cow. The following table shows the average composition of milk of cows:
c) Species: The composition of milk varies from species to species. Buffalo milk is rich in fat as compared to cow milk. Human milk is low in protein as compared to cow and buffalo milk and some that lesser in fat percentage, protein percentage but higer in lactose content. the following table shows the average composition of some of the important species:
d) Health/Physical Condition of Animals: The variation of composition of milk also depends upon the physical conditions of animals. If the animals is suffering from mustitic disease there is reduction in fat, protein and lactose content of milk but there is significantly increase in chloride content.
e) Age of Animal: The composition of milk varies because of age of animals. This factor is as considerable importance with regards to yields of milk/animals and also slight significance in compositionof milk. It has been observed for the percentage fat to increase slightly from the first to second or third lactation and then remains fairly transparent during the subsequent lactation. During the last few lactation the fat content is slightly reduced/reduces due to increase in the age of animals.
f) Stage of Lactation: The period from the time the calf is born until the animal ceases or stop to give milk is called period of lactation. The section of milk immediately after the calving is known as colestrum. It contains more protein and more total solid than that of normal milk. The composition of colestrum changes rapidly in successive milking and become normal milk in about 5-7 days after the calving. The fat percentage is also affected by the stage of lactation. In colestrum, it is low and during last stage of lactation, fat content slightly increase.
g) Season of Year: Generally, fat content of milk tends to increase in early winter and decrease in early summer. It seems probable that atleast two factors are responsible for these changes. The first factor is in majority, calves are born in early spring and consequently large percentage of animal reach to low fat stage of their lactation period in early summer and the condition which is responsible for this is temperature variation in between the season.
h) Weather Condition: During the long period of draught in summer, the yield of milk and SNF percentage content is reduced but the fat content is slightly increased. During the serious drought condition. The composition of many samples of milk may fell below in weather season.
i) Interval between the Milking: When milking is done twice in 24 hours and the interval between the milking is not exactly 12 hours each the fat of two milking is usually different. The milk drawn in long interval are usually rich in fat than the milk drawn in long interval are usually poor in fat content. That is why evening milk is slightly richer in fat as compared to morning milk.
j) Milking to Milking: It has been observed that milk obtained from individual animals differ in its composition in every milking. The interval both the milking and evironmental differ tends to cause such variation.
k) First and last Milking: There is a considerable variation in the fat content of 'foremilk', 'mid milk' and 'last milk'/'stripping'. Last milk i.e., stripping is usually rich in fat content since stripping are very rich in fat content unless each quater of udder in throughly strips at every milking slightly decrease in fat content. There is no variation in foremilk.
l) Feed: When the animal have given sufficient balanced rashan, feed has no effect on the composition of milk. When the feeding is changed there is no variation in the composition of milk but such variation are temporary.
m) Environmental conditions at the time of Milking: Anything which causes this discantentment and uneasyness in the animals at the time of milking causes to animals being nervous and leads to the holding up of last milk with the result, last milk is not led down and the fat content of milk decreases.
n) Excitment: The composition of milk is affected due to the excitment in the animals. It is not possible to predict the changes that may take place when it result into decrease and increase in fat content.
o) Exercise: There are many degree of exercise. Light exercise stimulates milk production without appreciable change in composition. In case of severe exercise as when animals are used as working animals, the volume of milk yield is usually reduced when fat content is slightly increased.
p) Milker: The amount of milk from a particular animal as well as its compostion is greatly influenced by the milker. Certain animals produce milk when particular milker milk that animal. Any change in milker likely to effect the quantity and quality of milk adversely. Sometimes, when the milker is not efficient and not able to draw milk completely from animalk there is slightly decrease in fat content.
The factor which are responsible for the variation in the composition of milk are:
a) Individuality of Animal: Animals belonging to the particular breed produce milk with different composition. Although they are kept under the similar condition and given exactly same feed. Milk produced by these animals in different composition such, difference in composition of milk are attribute to individual difference in animal. The heridity character may be the reason for such variation.
b) Breed: The breed is one of a most important factors influencing the composition of milk of some breeds of cow. The following table shows the average composition of milk of cows:
e) Age of Animal: The composition of milk varies because of age of animals. This factor is as considerable importance with regards to yields of milk/animals and also slight significance in compositionof milk. It has been observed for the percentage fat to increase slightly from the first to second or third lactation and then remains fairly transparent during the subsequent lactation. During the last few lactation the fat content is slightly reduced/reduces due to increase in the age of animals.
f) Stage of Lactation: The period from the time the calf is born until the animal ceases or stop to give milk is called period of lactation. The section of milk immediately after the calving is known as colestrum. It contains more protein and more total solid than that of normal milk. The composition of colestrum changes rapidly in successive milking and become normal milk in about 5-7 days after the calving. The fat percentage is also affected by the stage of lactation. In colestrum, it is low and during last stage of lactation, fat content slightly increase.
g) Season of Year: Generally, fat content of milk tends to increase in early winter and decrease in early summer. It seems probable that atleast two factors are responsible for these changes. The first factor is in majority, calves are born in early spring and consequently large percentage of animal reach to low fat stage of their lactation period in early summer and the condition which is responsible for this is temperature variation in between the season.
h) Weather Condition: During the long period of draught in summer, the yield of milk and SNF percentage content is reduced but the fat content is slightly increased. During the serious drought condition. The composition of many samples of milk may fell below in weather season.
i) Interval between the Milking: When milking is done twice in 24 hours and the interval between the milking is not exactly 12 hours each the fat of two milking is usually different. The milk drawn in long interval are usually rich in fat than the milk drawn in long interval are usually poor in fat content. That is why evening milk is slightly richer in fat as compared to morning milk.
j) Milking to Milking: It has been observed that milk obtained from individual animals differ in its composition in every milking. The interval both the milking and evironmental differ tends to cause such variation.
k) First and last Milking: There is a considerable variation in the fat content of 'foremilk', 'mid milk' and 'last milk'/'stripping'. Last milk i.e., stripping is usually rich in fat content since stripping are very rich in fat content unless each quater of udder in throughly strips at every milking slightly decrease in fat content. There is no variation in foremilk.
l) Feed: When the animal have given sufficient balanced rashan, feed has no effect on the composition of milk. When the feeding is changed there is no variation in the composition of milk but such variation are temporary.
m) Environmental conditions at the time of Milking: Anything which causes this discantentment and uneasyness in the animals at the time of milking causes to animals being nervous and leads to the holding up of last milk with the result, last milk is not led down and the fat content of milk decreases.
n) Excitment: The composition of milk is affected due to the excitment in the animals. It is not possible to predict the changes that may take place when it result into decrease and increase in fat content.
o) Exercise: There are many degree of exercise. Light exercise stimulates milk production without appreciable change in composition. In case of severe exercise as when animals are used as working animals, the volume of milk yield is usually reduced when fat content is slightly increased.
p) Milker: The amount of milk from a particular animal as well as its compostion is greatly influenced by the milker. Certain animals produce milk when particular milker milk that animal. Any change in milker likely to effect the quantity and quality of milk adversely. Sometimes, when the milker is not efficient and not able to draw milk completely from animalk there is slightly decrease in fat content.
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