In an actual test, the temperature of the milk placed in such a flask was 105° F., at 7.30 P.M., and had dropped to 93° F. by 9 A.M., the following day. The milk was curdled, and possessed the normal acid taste of such cultures.
The different types of apparatus are all quite simple, and it would be easy to make something at home. Get two round tins, the one less in diameter by from two to three inches than the other, put one or two pieces of wood across the bottom inside the larger tin, and fill up the space between with cotton-wool, which is an excellent non-conductor of heat. Place the smaller tin centrally inside the larger one. Fix three or four distance pieces of wood in the space between them, fill up with cotton-wool, leaving a little space at the top to permit the lid of the smaller tin to be fixed on. The boiling-water vessel may be a tin saucepan with a lid, but no handle, and its proper place would be on the bottom of the inner tin. A tripod stand made of three pieces of wire bound together, and with legs reaching past the hot-water vessel to the bottom of the tin, would support a false bottom of tin forming the shelf on which the vessels of milk to be treated would rest. These might be tumblers covered with tin lids. To prevent radiation through the lid of the inner tin, a thick pad or hood of cotton-wool packed between cloth would be placed over the top. A little experimenting would be necessary to determine the quantity of boiling water required to maintain the proper temperature.
The soured milk obtained in the above manner is of the consistency of ordinary buttermilk; a separation of whey frequently takes place, and this may be poured off if desired. The taste and flavour should be pleasantly acid and agreeable, and both are distinctive enough to give a good idea of the purity of the product. In many places a more concentrated article is made by boiling down the milk to one half or one third of its bulk, and then fermenting it in the ordinary way. A kind of thick pudding is thus obtained, which is highly recommended both as an agreeable article of food and as a stronger medium for the support of the germs it is the purpose of the sour milk treatment to introduce into the digestive system.
The cultures for making soured milk can now be had from all the leading wholesale and retail chemists, with directions as to the quantities to be used.
It is very necessary that the milk used should be not only fresh and good, but also free from chemical preservatives. The effect of these is to inhibit the growth and development of bacteria, and they have therefore an injurious influence on the special lactifying germs it is our object to cultivate. Preservatives are now not nearly so much used as they were, a few years ago, and there should be no difficulty in obtaining milk free from them.
For keeping both fresh and soured milk good a small ice-chest is an excellent device. The germs which are continually dropping into milk kept in open vessels in the air, even in cleanly surroundings, are mostly kept out in the close ice-chest, and the low temperature prevents in a natural way the development of the bacterial germs already in the milk. For the preservation of all kinds of foods the ice-chest is a capital investment, not to mention the benefit of having cooled drinks, etc., as required. They manage things well in this respect in the United States, where ice is regarded as a necessity in the summer time by even the poorest people, and is delivered with the same regularity as the milk.
It is necessary to utter a word of warning as to certain forms in which the sour milk bacillus is being offered to the public. It is being compounded with sugar, chocolate, and other articles, and sold in the form of sweets, etc. There is no reliable proof that these preparations are valuable. Certainly, sugar is a medium in which the lactifying germs can live, but the quantity so introduced into the system must be very small compared with what is obtained from properly fermented milk. It takes some time, even with strong cultures, to fix the acid-producing germs in the large bowel where they are wanted, and until proper evidence is forthcoming that confectionery preparations are efficacious we would recommend that only the regularly fermented milk be used. It would save trouble, no doubt, to treat oneself with a few chocolate creams containing the necessary germs daily, but if the matter is taken up seriously it will be better to take some pains and stick to methods the efficacy of which has been demonstrated, leaving the others until their bona fides has been proved. There are always enterprising firms who are prepared to simplify things for us, but we must make sure that their simplifications are warranted.