MILKY MYSTERIES.

New Zealand Herald, Volume LXVIII, Issue 20762, 3 January 1931, Page 5

MILKY MYSTERIES.

SCIENTIFIC RESEARCH.

STRANGE RAT COLONY.

OPENNE3S OF DOMINION PRODUCT

[from a special correspondent. 1

Bread-and-milk, and nothing but bread-and-milk, from childhood to old age, i 3 the fate of hundreds of rats at , the National Institute for Research in Dairying, near Reading, Berks., where, with the aid of grants from the Empire Marketing Board, the products of cow and dairy are the life study of about 30 specialised scientists. Rats not only live on bread-and-milk alone; they thrive heartily and produce large families, even unto the fourth generation. Theic are rats whose fathers, grandfathers and great-grandfathers knew no other food, and, far from being milksops, they are sharp-toothed, trimwhiskered young rodents, ready to match their wits against a cat any day. In the same shed are cages containing puny, emaciated rats half the size of their neighbours and too weak to rear families. They, too, have been brought up on bread-and-milk, but with this vital difference—the milk has first been sterilised. An interesting fact which has incidentally come to light is thai, rats who have been starved for vitamin B and arc given unlimited supplies in the form of yeast, do not eat enough to make up the deficiency and perish in the midst of plenty. Captain G°'ding, the dairy Chemist in charge of the rat experiments,'."believes ho has proved the far-reaching fact that whereas whole milk is a perfect food, sterilisation destroys certain vitamins and other substances, and sterilised milk, therefore, loses much of its nutritional value. New Zealander's Success. This is, he thinks, of particular interest to New Zealand and where most of the milk used for cheese-making is pasteurised. A special study of this and other problems has; been made at the Reading centre by a New Zeaiander, Dr. George Moir, who won a two years' research scholarship in England and who has just returned to apply his knowledge in New Zealand. While sterilising and pasteurising are, of course, quite separate processes, certain changes may occur in the chemical composition of milk as a result of the "flash" method of pasteurisation, and it is possible that the vitamins may be • affected. Another study of the vitamin content of milk and butter is being made in co-operation with Reading at the Lister Institute, as part of a general scheme of research into the vitamin properties of Empire produce under the Medical Research Council. The home of the research station, of which Dr. R. Stenhouse Williams is director, is an old manor house about four miles outside Reading (famous for biscuits and beer), The house has been converted into up-to-date laboratories, and scientists now perform their titrations and analyses where the old squire may once have polished off his second bottle of port every evening. A mixed herd of 30 or 40 Shorthorns and Guernseys is kept and grade A tuberculin-tested milk of a high average butter-fat content is produced, both for sale and for experiments.

When is a Cheddar Not a Cheddar? What is the difference between "a Cheddar and a Stilton ? or a Cheshire and a Swiss cheese? This is one of the problems that the Reading men are trying to solve. They cannot explain in scientific terms why such small differences ill manufacturing processes should result in such very different, products. • Still less can they explain why exactly _ similar treatment of the same raw material—milk —in different parts of the country, or in different countries, should produce cheeses with distinctly Afferent flavours, textures and keeping qualities. The real difficulty they are facing, as Mr. A. T. Mattick, the bacteriologist, explained, is that milk is so tremendously variable. Its chemical composition, for instance, varies not only according to district, cow, feed, season, etc., but even in different quarters of the same cow's udder. One of the most remarkable pieces of work at Reading is a complete chemical analysis of "typical milk" over a period of several, years. The milk is analysed overy day and a chart made of the fluctuations of its chemical contents. The chart now stretches- right across the laboratory and the rise and fall in the proportion of butter-fat, minerals of various sorts, casein, etc., can be seen at a glance. What are the real causes of these fluctuations and how dc they link up with feed, age and health of the cow. 'season, etc. f These are the sort of problems being tackled. They lead on to broad questions of the influence of rations on the quality—for example, but-ter-fat content —of milk, about which practically nothing is known. Sociology in Cheeses.

Mv. Mattick and his team are making a close study of (he relationship between the various groups of bacteria in milk and cheese. Bacteria, like men, are not sufficient unto themselves. Each race reacts on its fellows and there is a constantly changing; balance between the groups. As in tho world, the population rises and falls, wars and earthquakes (or milk-quakes) reduce it again, revolutions destroy one group and another, takes its place. Bacteria's life is not a peaceful one. This sociology of bacteria is a fascinating study, over which the Beading men wax particularly enthusiastic. "inoculate" bacteria' into "pure cultures of agar-agar (a Japanese seaweed) and grow them in glass dishes in incubators. By these means they can sort the various kinds and observe the habits of each Some of them are undesirables and do harm to cheese, and these, such as "red spot," organisms, must be discouraged. Others may speed up or retard ripening of cheeses. Another fault which is. being studied is "openness" in choose, the most .serious problem of the industry in New Zealand. It lias been estimated to cause New Zealand a loss of £1,000.000 a year. The cause is still unknown, but Beading is co-operating on an extended scheme of research with the Palmerston North dairy research station, to which the Empire Marketing Board has just given a grant. A large batch of cheese mado at the Massey College was recently, sent over to Beading in refrigerated holds containing devices to keep a constant record of the temperature throughout the Voyage. An exactly similar batch was kept at tho Massey College. Samples of all the cheeses were analysed at Nelson, and again at Beading in the case of tiie exported batch. The object was to study the effect of transport and refrigeration on ripening. It was interesting to note that tlie temperature records for the wholo voyage showed an absolutely level, steady temperature throughout and an almost complete absence of fluctuation.