70. Skimmed Milk and Buttermilk
[I had addressed a number of questions to Dr. Aykroyd, Director of Nutrition Research, Coonoor, and to Sjt. Satis Chandra Dasgupta, on the advantages and disadvantages of skimmed milk and about making it popular. Both of them have kindly favoured me with their considered opinions which will speak for themselves.- M. D.]
Coonoor, the 18th May, 1937
Dear Mr. Desai,
I am sending under separate cover two copies of Health Bulletin No. 23, The Nutritive Value of Indian Foods and the Planning of Satisfactory Diets, with a reprint of a scientific paper about skimmed milk, etc.
You ask a number of questions about the nutritive value of separated milk and buttermilk. Separated or skimmed milk is of high nutritive value, since it contains all the valuable elements present in whole milk except fat and vitamin A. Whole milk of good quality is to be preferred to separated milk because it contains vitamin A, but there is no question that the regular consumption of separated milk very greatly improves the health and development of Indian children fed on "typical' Indian diets based largely on rice or millet, containing no milk or eggs, and very small quantities of vegetables. An important advantage of skimmed milk, of course, is that it is cheaper than fresh whole milk.
We have used imported dried skimmed milk in a number of experiments. Children receiving 1 oz. of dried skimmed milk powder daily for 3-4 months showed greater increases in height and weight than children on a precisely similar diet without milk. The general condition of the milk-fed children showed remarkable improvement. The milk was given in liquid form, roughly 8 times its weight of water being added to the milk powder to 'reconstruct' liquid milk.
There can be no doubt that liquid separated milk would produce the same effect as dried powder, which is after all only the former reduced to powder by a mechanical process. Such milk should on no account be allowed to go to waste. Only a little organization is required to arrange for its distribution to school children, etc.
With regard to taste, we have found no difficulty whatever in persuading children to drink reconstructed skimmed milk, or, in another experiment now in progress, liquid separated milk. They seem to like it. I cannot agree that fresh separated milk has a bitter taste. I would suggest that any objection to the taste of such milk might be overcome by the addition of a little sugar. It could also be consumed mixed with cereals, in the form of pudding or porridge.
The transport of liquid separated milk is attended with the same difficulties as the transport of whole milk. Milk is a perishable article of food. Boiling or pasteurization to some degree extend the period during which milk remains fit for consumption. The only way to preserve milk is to turn it into cheese, or to condense, evaporate or powder it. The 'khoa' of Northern India, used in the making of sweetmeats, is an evaporated milk product which seems to keep for some time.
The distribution of liquid separated milk would have to be undertaken in the same way as that of liquid whole milk - i.e. on a daily basis. Boiling before distribution would cause no serious loss in nutritive value.
'Buttermilk' is a term which has several meanings in India. 'Buttermilk' made from curds - i.e., soured milk from which a good proportion of the fat has been removed - has roughly the same nutritive value as separated milk, provided no water is added. If, as often happens, large quantities of water are added to 'buttermilk' of this nature, the resulting product is still called 'buttermilk' but of course its food value has been greatly lowered. A third form of 'buttermilk' is the liquid which separates out when cream is churned into butter. This type of "buttermilk' is of relatively low nutritive value, since most of the valuable elements remain in the original milk from which the cream was obtained. It should, however, not be waited, since it has some food value and is better than no milk at all.
One important fact should be borne in mind. Separated or skimmed milk is not suited to form the sole food of infants, it must be supplemented by some food substance rich in vitamin A - e.g. cod-liver oil. It may, however, be used with advantage to supplement the diets of young children past infancy when such diets are largely based on cereals and contain few vegetables and no animal protein. Separated milk in such circumstances is much better than no milk at all. Our own experiments have demonstrated its value as a food for older children. It would also be a very useful addition to the diet of expectant and nursing mothers.
I have no objection to your publishing this letter in the Harijan.
Buttermilk contains all the ingredients of whole milk except butter and vitamin A. If I were to valuate boiled milk in which vitamin C is destroyed, I would put the following values on the ingredients:
a) Butter and vitamin
A - 8 annas
b) Proteids - 5 annas
c) Milk, sugar and mineral salts and vitamin B - 3 annas
If, therefore, whole milk is valued at 16 annas, buttermilk which contains items B and C should be valued at 8 annas. As a matter of fact it is sold proportionately for much less and is therefore a cheap but valuable article of diet for poorer people who cannot obtain whole milk. Where butter is produced on a manufacturing scale by separating cream from milk, the buttermilk is sometimes a drag on the manufacturer.
Buttermilk can be made into dahi and sold locally. There is a limited sale for such dahi where large quantities of milk are handled. Where there are cheap means of communication such dahi is transported to distant places also.
By souring buttermilk with sour dahi or acid substances like citric acid or alum the proteins are precipitated. This is chhana. Chhana is also obtained by acidifying whole milk. But then that chhana brings down the fats with it also. Chhana from buttermilk is inferior to that from whole milk and sells cheaper. Manufacture of chhana is one of the common commercial uses of buttermilk. It can be carried longer distances than dahi but fetches less value. The sugar and mineral substances 'C' are left in the water after separation of chhana. Chhana is, therefore, less nutritious than buttermilk-dahi' and has only 5 annas value as against 8 annas of buttermilk-dahi.
Buttermilk will yield casein which is another form of chhana. If there is no demand for chhana or dahi, casein can be made from buttermilk.
4. Condensed Milk.
Buttermilk can be best popularized by being condensed and sold as condensed skimmed milk. Tons of 'Cowshed' brand skimmed condensed milk are imported. As I found by experiment, condensed milk can be made in cottages. There are difficulties to be overcome in proper packing, but they are not insurmountable.
Buttermilk is a dangerous substance if it or its products are passed off as whole milk. Dishonest persons separate some cream from milk and sell the partially separated milk as whole milk or as whole-milk-dahi or whole-milk-chhana. The dahi or chhana of towns is frequently made from milk from which cream has been separated partially.
Chhach is to buttermilk as dahi is to whole milk. When butter is taken out of whole-milk-dahi chhach is left. When butter or cream is taken out of milk, and the buttermilk is converted into dahi, it is equivalent to chhach. The appearances of such dahi, and chhach are different but the substances are same. If buttermilk-dahi is churned, it at once takes the appearance of and becomes indistinguishable from and identical with chhach.
For making milk-powder from whole milk or buttermilk special vacuum and steam heating machinery are to be used. Milk-powder cannot be made in cottages.
S. C. DASGUPTA