LIGHT AND MILK

Te Aroha News, Volume XLI, Issue 6546, 20 November 1924, Page 7

LIGHT AND MILK

AN INTERESTING AMERICAN INVESTIGATION The effect of sunlight on milk has sjgjen ? the subject of investigation by two American chemists of lowa Agricultural College, U.S.A. They, have made a comparative study of the effect produced upon the colour, flavour and bacterial content of milk by placing it’ in white and in coloured bottles respectively. The results proved .that sunlight produces abnormal flavours in milk and cream, hence the necessity of keeping bottles of milk, even in winter, in a special covered client or under a blanket. Though broWn milk bottles prevent these their use, the investigators State, cannot be advocated, because they make it difficult to see' the sediment or the cream line, thus preventing whole milk being distinguished from milk that has been more or less skimmed. Milk kept in brown bottles has also a higher bacterial content than milk in ordinary bottles, which is iff part due to the higher temperature of the brown bottles, and also to the fact that light has a decided influ-; ence in, keeping down the number of bacteria in white bottles. In fact, if part of the same milking is exposed to sunlight in ordinary bottles and the rest kept in the dark in similar bottles, it will be found that the bacterial, content is lower in the exposed ipflk, although the temperature is jiighew. ■ ' \

From the general results of their observations the investigators have drawn the following conclusions:— Sunlight has a pronounced influence on the flavour 6f milk and cream; with sufficient exposure a definite tallowy flavour was produced and with less exposure a distinct sour flavour develdpefl. .. When there was an increase in acidity in milk exposed of ordinary'bottles and brown, the increase was generally greater in the brown bottles. The colour of Ailk exposed to sunlight/doesnot alter nearly as much in brown as in colourless bottles, in which the milk after a time shows a chalky: dead-white appearance and produces butter of much lighter colour. Light has a greater influence on a milk low in- fat content than on a milk with a high fat content. Exposure to air had evidently some influence on the development of a flavour. The tallowy flavour in milk exposed to Sunlight in white bottles apparently decreased • somewhat as a result of storage at low temperature. . Sunlight is observed to produce an abnormal flavour, sometimes tallowy and sometimes otherwise, v in other dairy products, such as ice cream, evaporated milk, ’skim milk, and starters. Whenmilk or cream has acquired a tallowy flavour from exposure to light, it is communicated to the butter, which does not lose it by keeping.