Milk of the cow is an opaque, white or yellowish white, very slightly alkaline fluid that is chemically termed as an emulsion which is a colloidal suspension of fat and other particles. It is just a little more viscous than water. In taste it is sweet or bland and it also has a faint but an unique odour. If kept for long it ferments and gets sour. Specific gravity of the ordinary milk is between 1.027 to 1.034. This is lower in a milk that has a higher fat content. If a drop of milk is inspected under microscope, numerous minute globules of fat can be seen to be floating as an emulsion.
It is these particles that join together when milk is kept for some time to form the cream on the surface. When churned, the cream separates into butter and the buttermilk is also secured simultaneously. The butter on being melted on fire quickly turns into clarified butter or ghee, which can bepreserved for considerably long periods unlike all the other products of milk which get spoiled soon. It is the fat globules that are responsible for the yellowish white colour of the milk.
If milk is kept standing in an undisturbed way, it settles into three layers. The layer at the top consists of these fat particles, the cream being the lightest and also a considerable amount of bacteria that are attached to these particles rather permanently. The middle is constituted by what is called the milk plasma and a small amount of fat.
The lowest layer at the bottom consists of the rest of the bacteria in the milk and also various types of dirt. Such a natural settling out of milk makes it possible for us to separate out the butter fat and to control the amount of fat in the milk that the milk we need shall contain. If milk is kept raw i.e. unboiled, it becomes spoiled after 10-12 hours. It becomes then indigestible and actually harmful and poisonous and is therefore to be totally avoided from being consumed in any manner whatsoever.
Milk is so much valued as a food because it contains most substances that are nutritionally essential for the growth and development of bones, nerves, muscles and other tissues of the body. Milk also contains vitamins which are indispensable to health and also act as inbuilt mechanisms of the body to combat several debilitating diseases such as rickets (disease of children characterised by softness of the bones caused by deficiency of vitamin D), scurvy (disease marked by sponginess and bleeding of the gums of the teeth due to a lack of vitamin C) and such other results of defective nutrition. The detailed constituents of the milk is an accordance with the individual animal and the nature of the feed that it consumes. On an average, cow’s milk contains principally of 4 per cent of casein (the albuminoids), 4 per cent of butter (fat), 5 per cent of milk sugar (sugar), several types of salts and 86 per cent of water.
There is a large percentage of calcium phosphate in it, a very important salt that is required for two inestimable functions of the body viz. development of bones and for bringing about a proper coaguability or clotting of the blood. The following are the other valuable component salts that are found in cow’s milk: potassium and magnesium phosphates, sodium chloride and a trace of phosphate of iron. The following are the inorganic constituents: gases like carbon dioxide, nitrogen and oxygen in solution and mineral salts like compounds of calcium, potassium, sodium, phosphorus, iron, sulphur and chlorine. Of these salts, the first four occur in an amount that is slightly higher than necessary to combine with sulphur, phosphorus and chlorine that are available. The excess is principally calcium which gets combined with casein to form calcium caseinate.
The composition of milk, varies specially as regards the percentage of the fat and the proteins which vary much from time to time. Buttermilk or the milk that remains after the cream or its fat content is fully taken out as butter is an important product of milk that has extensive medicinal application in Ayurveda and also as a household and readily available remedy.
Sweetened or salted and seasoned as desired, this forms lasst This is composed of 91% of water, 0.5% fat, 4% sugar, 0.5% lactic acid (an acid that in unique to milk), 3.5% protein, and 0.7% ash. Whey is another important product of milk. This is the watery portion of milk obtained when milk is purposefully broken by mixing with it a little bit of sour, like lemon juice. The fat portion that gets separated and collected out by hand or machines is chartna, paneer or cheese. All of these products of milk have their own distinctive value in nutrition and medicine.
Cow’s milk contains slightly more salt and much less sugar in comparison with breast milk. Cow’s milk invariably consists of fat globules and bacteria and also particle of many foreign matter— all floating as a suspension in the fluid portion of the milk or the plasma. Though it is secreted in a sterile i.e. a bacteria-free state in the cavities of the udder, a number of bacteria get Introduced in the milk from many sources. Infact, the nature of the bacteria content of the milk is the surest index of the cleanliness of the milk.
This however can be assured only with meticulous care taken, such as milking only from healthy cows and in a healthy and hygienic surroundings by milkers who are also healthy and have clean hands. And, a good way of further ensuring the healthiness of the milk obtained is to chill it as soon as possible. It is because of all these reasons and more so because such scrupulous aspects of hygiene are rarely met with, an important aspect that one should also appreciate in knowing about milk is to evaluate it properly as a disease carrying agent.
The protein or the body building substance in the milk occur in cow’s milk in the form of casein .in combination with calcium; physically it forms the colloidal particles in suspension. There are too other protein components viz. lactalbumin and lactoglobulin, both being unique and characteristic of milk. Proteins in turn are made up various combinations of about 20 types of aminoacids. In fact the value of protein depends upon the number and the proportion of the amino acids that go into its constitution.
Of the several types of amino acids, four are essential in a child’s diet; these are: tryptophane, lysine, crystine and hystidine. The lactalbumin found in milk contains 4.08 per cent of this crystine while its casein contains only 0.26 per cent. There is a greater amount of lactalbumin or breast milk in comparison with cow’s milk and this is why breast milk is more suited to the infant than the cow’s milk. But there is no doubt that cow’s milk protein is the next in the list. But to supply an adequate amount of the protein, nearly double the amount of cow’s milk will have to be given to the child.
But it is interesting to note here that the Indian cow’s milk approaches breast milk more nearly in comparison with other milks for eg. of the foreign i.e. European cow’s or of the buffaloes. Ordinarily the amount of protein in European cow’s milk is double that of European mother. The fat content is however nearly the same in both while the sugar content is a little less in the cow’s milk there. The European physicians therefore advise the mothers there to dilute their cow’s milk with an equal amount of water and to also make good the fat and sugar deficiency in such a mixture by adding one teaspoonful of cream to every three ounce of the prepared milk, which they henceforth designate as the humanised milk for their infants.
If however this advise is followed blindly by the Indian mothers using Indian cow’s milk, the result would be down right harmful. For, the child so fed would be practically suffering from a deficiency not merely of protein, fat and carbohydrates but also of the essential vitamins and mineral salts.
Buffaloe’s milk is richer than cow’s milk and consequently yields more butter. Ass’s milk contains less of salts and fats but more of sugars. Breast milk contains more of fat and less of salts but it contains all the necessary elements for the child in absolutely correct proportion, neither more nor less and is therefore the most ideal food for its all around development. Actually there is no other type of milk or milk substitutes that can replace breast milk in all ways, or, in any way, for that matter.
It is the food that Nature has intended for the purpose and therefore non replaceable. Goat’s milk contains an excess of calcium but in other ways, it varies very little from the mother’s milk; probably this may be thus the next best to breast milk for the human child. Then comes the ass’s milk and cow’s milk comes only after the ass’s milk as it differs much more from the human milk
In areas where cow’s milk of reliable and standard quality is not available as it happens in modern metropolitan complexes, many types of prepared products from milk are used. They are: powdered milk, evaporated milk, condensed milk, lactic acid milk, peptonlsed milk, butter milk and whey. Of these, the last four are employed only in feeding the invalid, the small, the weak and the premature children. This is specially so in connection with cheese, protein, milk, lactic acid milk and whey. For preparing all of these products only the pasteurised i.e. bacteria free milk should be used.
Milk is the diet for energy, bodily heat and growth. Persons who take milk and its products like butter, cheese, curd and buttermilk do not need any medicine generally. Children given ample milk daily grow taller; a milk diet adds to the beauty and is the satwic food also. Almost all milk foods are rich in proteins, calcium and phosphates; all of these are vital to build, maintain and energise the body. They are good for bones and teeth and are rich for blood.