HEALTH NOTES.

Otago Daily Times, Issue 19906, 28 September 1926, Page 13

HEALTH NOTES.

MILK. ITS COMPOSITION. DANGERS ARISING FROM ADULTERATION. Contributed by the Department of Health. Milk is a substance which varies considerably in composition even in animals of the' same species. The basic ingredient is water, in which the remaining components are either dissolved or held in suspension. ’Ordinarily .milk contains approximately 87 per cent, of water, and at least 3.25 per cent, of butter-fat and 8.57 of solids other than fat. When the solids fall below this the purchaser does not receive full value for his expenditure. On this account legal standards have been adopted in practically all countries. Fat is one of the most valuable constituents of milk. It is present in the form of an emulsion, the droplets being held in suspension and giving the milk its normal colour. The amount of fat varies considerably,' many cows producing a milk which contains as high as 5 per' cent, of milk,- while with other breeds the percentage is much lower. Milk strippings are richest in cream, while the first milk drawn is poor in this ingredient. . Unfortunately, the richness of milk cannot in every imtaqce be determined by the thickness of the cream layer, although most housewives place entire dependence upon this method. Milk which has stood but a short time will necessarily have only a thin stratum of cream, while that which has been agitated may show none at all, the fat being evenly distributed. Again, milk which has been heated beyond a certain temperature shows only a slight cream layer. It is to be realised that a deficincy in a small amount of fat is not nearly as important as other considerations, such as the presence of disease bacteria. IMPORTANT AS FOODS. A number of, substances, called proteins, of complex chemical composition, are also found in milk, and are important as foods. The principal one is familiar as the curd in sour milk. When milk is taken into the stomach the casein is precipitated from its watery solution by the ferment renhin' used in cheesemaking. The casein of cows’ milk when precipitated in this manner during the act of digestion forms much larger and tougher curds than the casein of mother’s milk, and hence is more difficult of digestion. Other proteins, known ns albumin and globulin, are also present. Proteins are always present even in skim milk, and for this reason milk deprived of its fat has still considerable food value. A third constituent of milk is lactose, or milk, sugar. This substance is similar to ordinary sugar in composition, but differs from it in its sweetness, and other properties. It chars upon heating, thus Kiying the milk a brown colour when the temperature approaches the boiling point. When the sugar is acted upon by bacteria in the milk, it ferments and the product of this fermentation is lactic acid. The latter causes old milk to taste sour, and throws down the casein in the form of curd. While there is approximately 7 per cent, of milk sugar in mother’s milk, there is jess than 5 per cent, in bow’s milk. Lactose is to be preferred _ over other sugars in the preparation of infants’ food. Various salts notably compound of lime and phosphorus, are also present in ihilk. ABNORMAL QUALITIES OF MILK. A bitter taste may bo caused by certain plants or weeds eaten by cows, or it may bo due to the action of bacteria. In the first instance the milk is bitter when drawn, while in the second the bitterness does not develop until several hours later. Bitter milk is never desirable although it may not be directly injurious. A change in the colour may be brought about by a number of causes. It may bo due to the consumption by cows of certain plants containin'” a large amount of pigment or it may result from contamination with various bacteria producing a rod or blue discolouration. Frequently discolouration is due to the presence of blood resulting from inflammation of the udder. The use of milk of this character is dangerous; therefore, any variation from the normal colour should be recognised as a warning signal. Sljmv milk may be due to inflammation of the udder, to age, or the presence of bacteria. Milk showing these properties should be rejected as unfit for consumption. Milk readily absorbs odours, and the flavour may be modified by many articles with which it comes in contact. Thus, milk which has been stored with foods which possess a distinct odour, often develops the characteristic scent even when exposure has been of short duration. Cattle which have been fed on fermented foods, ensilage that is too green, mouldy grain, etc., almost invariably secrete milk of a distinctive colour. MILK ADULTERATION, The addition of water is unquestionably the oldest form of adulterating milk. In proportion to the amount of water addea it causes a diminution in the various elements, and if the water is contaminated it may bring about the development ol typhoid fever, dysentery, and, other waterborne diseases. Skimming is the least objectionable form of adulteration from a health standpoint. It consists in removal of the fat by a separator or by abstraction of the top mijfe or cream. The legal standard in New Zealand is that milk shall contain at least 5.25 per cent, of fat. Milk is occasionally adulterated with colouring agents to give it the appearance of richness. PRESERVATIVES. Milk is an exceedingly perishable product, compared in this respect with fish, heat, etc. It spoils most readily if not maintained at a proper temperature, and if cleanliness is not exercised in the handling. Certain chemicals have been found to delay or retard this decomposition, and these substances ' known as milk preservatives were at one time ■ widely in use to preserve milk. Chemicals are not to be regarded as substitute for cold and cleanliness, the only satisfactory preservatives, and their use is a plain indication that tho ordinary and customary precautions in handling have not been exorcised. These adulterants, now prohibited by ‘.aw, are easily recognised by suitable tests and samples are constantly examined for such by the department. ACCIDENTAL IMPURITIES. From a health standpoint the accidental impurities of milk are more important than those just discussed, tho adulterations intentionally added by man. Illness seldom arises in adults from the abstraction of any element contained in milk but serious maladies may result from contamination which is accidental though nevertheless preventive. Carefulness in production and handling is as much, to be esteemed aS strict. honesty in composition, although in the past the average person has given more consideration to tho former than to the latter. BACTERIA IN MILK. Invariably accompanying and intimately associated with dirt _in mill:, are other substances far more injurious than dirt in itself. These are bacteria. All milk contains bacteria in greater or less degree. Certain of these organisms may be derived from, the udder of either diseased or normal animals, others may have their source in filthy conditions in the milking sheds, or they may occur from contamination in handling and arc therefore an index of faulty milking or methods of handling of milk. A good milk may contain very few bacteria, and there are undoubted instances of untreated (raw) milk containing as few as 100 bacteria per cubic centimetre. When milk is exposed to a temperature of 145 degrees F. and is held at that point for 30 minutes all disease-producing organisms are destroyed. If the supply is then imediately chilled further multiplication of the remaining germs is temporarily inhibited. This treatment of milk is 'taken advantage •of in the process known as “pasteurisation.” The difference between pasteurisation and boiling is only one of degree, tho former destroying only harmful organisms while the latter kills practically all varieties haimful and harmless alike. Boiling, however, is open to the objection? that it produces a change in the colour of the milk, retards the rising of the cream, leaves a “cooked taste.” and destroys certain vital principles which are found in raw milk It is a very certain way, however, of making a suspicious rpjlk absolutely safe. For adults pasteurised milk is as nutritious n» raw milk, and the digestibility of the two is the same. For infants, however, there is the objection that pasteurisation partially destroys the anti-scorbutic vitamin. This is of little moment, for in all cases of infants fed artificially the addition to the diet of the juice of fresh fruit such u th»