THE PRODUCTION OF CLEAN MILK FOR HUMAN CONSUMPTION

Pukekohe & Waiuku Times, Volume 7, Issue 349, 1 February 1918, Page 4

THE PRODUCTION OF CLEAN MILK FOR HUMAN CONSUMPTION

By H. Munro, Inspector of Stock and of Dairies, Wellington. (From the Journal of Agriculture"; While the value of milk as human food) particularly for young children and invalids, is universally recognised, the many ways in which it may become contanimated, and its consequent danger to life and health, are not so fully realised. It is necessary, in the first place, to recognise that once foreign matter gains access to milk only the larger solids, which are the least injurious impurities, can be wholly removed ; liquid filth and the greater proportion of the bacteria which are responsible for souring, putrefaction, and disease cannot be eliminated by mechanical means, such as straining. Efficient pasteurization of milk is of considerable benefit, in that it destroys dangerous bacteria and adds to its keeping qualities; it is, nevertheless, only a partial remedy for milk which has already become contaminated. It follows, therefore, that milk which is once polluted remains permanently more or less damaged according to the extent of the pollution, and that care on the part of the producer to prevent contamination is infinitely more valuable from the standpoint of both public health and economy than any purifying treatment which can be applied later. The conditions essential for the production of wholesome milk are healthy cows in good condition, clean utensils, sanitarv premises and surroundings, careful and prompt treatment of the milk after milking, and an ample supply of good water. The principal sources of milk-con-tamination are dirt from the flanks, udders, and tails of the cows, from the milker's hands and clothes, and from unclean utensils, dust from the air, injurious odours due to insanitary surroundings, and improper treatment after milking. It is practically impossible to produce clean milk from cows which are driven through a quagmire to the milking shed, held in a filthy yard prior to milking, or milked in dirty premises. Before milking, the cow's udder and teats, and also the milker's hands, should be washed in clean water, and carefully dried. Dry cleaning is unsatisfactory, as the remaining scurf and dust find its way into the milk. Objectionable and injurious odours are very readily absorbed by milk, particularly when it is being poured, as in milking, straining, cooling, etc., or when stored in the vicinity of strongsmelling substances of any kind. Injurious bacteria of all kinds increase most readily in milk at a temperature of SUdeg to lOOdegF., and the rapidity of their increase diminishes proportionately as the temperature of the milk is lowered. Milk should therefore be removed from the milking shed to the dairy as soon as possible after milking, and immediately strained and cooled. The dairy should be kept exclusively for storing and treating milk, and should not be used as a storeroom for any other commodity. The straining of milk through open gauze strainers or open textured or dirty cloths is only a pretence, and cannot be too strongly condemned. The straining should be done through cotton-wool, on the principle of the " Ulax" strainer, or if on occasions it is found necessary to use cloths they should be clean and of close-textured material, and should be washed and boiled after treating each lot of milk. For cooling, the corrugated circular cooler is most suitable, as by its use the milk while being cooled is to some extent simultaneously aerated. It is also the easiet type of cooler to clean, which is in itself a strong recommendation. The temperature to which milk can be cooled depends on the volume in which it is permitted to flow over the cooler, as well as on the temperature of the water used. Artesian water, being usually pure as well as cold, is the most suitable source of supply for cooling. When this is not procurable under-ground tanks so constructed as to prevent the entvv of surface water or foreign matter, and fitted with a hand-pump, provide the best substitute. Where milking machines are installed the pumping can, of course, be done by machinery. When the water is stored in tanks above ground, or conveyed in pipes, these should be protected from the sun. In order to retain the milk at the low temperature secured by passing over the cooler, and also to reduce it still lower if possible, the cans containing the cooled milk should be placed in a concrete trough in the dairv containing sufficient water to cover them to within a few inches of the tops and provided with a constant flow. Wooden troughs are unsuitable for this purpose. Warm milk should on no account be mixed with cold milk.

Straining, cooling, and aerating purifies milk, and increases its keeping qualities by removing foreign matter, retarding the development of bacteria, and helping to remove objectionable odours and gases. The value of such treatment, however, depends to a great extent on the time which is permitted to elapse between the milking and the treatment, as well as on the efficiency with which the work is done. If the milk is allowed to stand for some time after milking before being strained and cooled the value of each process will lie correspondingly reduced. Thfl milk from cows showing signs of disease or sickness in any form should be discarded until the cause is ascertained and tho animal completely recovers or is disposed of. Even in the absence of other and more definite symptoms, a rapid diminution of tho milk-yield is characteristic of abnormal health in a cow, and in all such cases the milk should be discarded until the yield returns to normal or tho cause of the drop is known to be harmless. Milk produced from cows for twenty-one days before calving is usually not normal milk, and it is not advisable to mix it with milk intended for human consumption. Milk produced from cows for several days after calving is unlit for human consump tion, more particularly for infants By regulation under the Food and Drugs Act it is made an offence to

soil milk from a cow for seven clear days after calving. Milk which appears in any way abnormal, such as bloody, watery, or slimy, should be unhesitatingly discarded, even when the cow appears in good health and the udder normal.

Milk-cans and other metal utensils used for handling milk should be well tinned, and so constructed as to permit of easy cleaning; wooden vessels of any kind are unsuitable for handling milk. Rusty cans are not only difficult to clean, but the flavour of milk contained in them is injuriously affected. Utensils having open seams, crevices, or corners, such as kerosene-tins, which are occasionally converted into milkbuckets, permit the accumulation of decomposed milk, rust and slime, and are consequently quite unsuitable for handling milk. Milk utensils should be cleaned immediately after they have been used, and before the milk has time to dry on them. They should be first rinsed with cold water, then washed with hot water and soda, again rinsed with clean water, and finally scalded with boiling water. Immediately they are scalded they should be inverted on a drainingstand, so that they may dry quickly exposed to the sun and protected from dust, Brushes should always be used for washing. If very hot water is used on utensils with milk still adhering to them a coating of milk will eventually become scalded on to the metal, and will be found difficult to remove. Milk utensils may appear to be clean after being washed with warm water, but unless they have been scalded they will probably still contain numerous bacteria which will hasten the souring of milk. The increasing shortage of good dairy labour during the past two years has been responsible for a rapid incrsase in the installation of milking machines. In the opinion of the writer, given proper care, machines provide a more sanitary method of producing milk than hand milking, as by the former method the milk is to a great extent protected from contamination from the skin of the cow. human hands, and odours from the milking shed. Too great stress cannot, however, be placed on the necessity for regular and thorough cleansing of every part of the plant, as carelessness in the cleansing of any part will readily convert their advantages into a menace. The plant should be erected so that water can be pumped through the whole system—both releaser and vacuum—and angles in the milk pipes should be as far as possible avoided. Milk should not be released in the milking shed or engine room ; it rhould be released over a cooler into cans in a separate apartment, and then removed to the dairy. The following is a copy of directions issued by the Dairy Division of the Department for the cleaning of milking machines:

REQUISITES 1. Plentiful supply of clean cold water. 2. Provision for boiling water. 3. Set of suitable brushes for cleaning rubber tubing and piping. 4. Vacuum tank should be so placed that drainage connects with main dram. 5. Vacuum tank should be fitted outside the sheds where the air is pure, and in such a position that it may be easily cleaned. G. Two or three wash-up tubs placed outside the milking shed. 7 Have milk pipes on automatic releasers erected' in lengths of not more than fift. 8. Vacuum pipes should be laid so as to allow water to be ejected or pumped through them and drain to the vacuum tank. 9. Use only rubber parts which are sound. Split inflations result in the contamination of the whole vacuum system, and where such have been in use thorough cleansing should take place before next milking. 10. Where steam is in use the pipes should be so arranged as to allow it to be blown through the whole system.

BEFORE MILKING I. Rinse all rubber parts and buckets with clean cold water. 2 Wash cows' teats- and udder with clean water and dry with a clean cloth before putting on teatcups. AITER MILKING 1. Draw cold water through teatcups, releaser, and vacuum tank. 2, Wash any dirt from outside the teat-cups and tubes after placing in tub No 1. Take down pipes of autorna tic releasers daily for washing. 4. Every day wash with a brush iu hot soda-water in tub No 2 all parts with which milk comes iu contact—viz , teat-cups, tubes, releaser pipes, etc. This should be done as soon after milking as possible. Draw brush through daily. 5. After these parts are thoroughly washed they should be rinsed with clean water and then thoroughly scalded with boiling water. 6. Leave all rubbers in a bath of clean water to which some lime or salt has been added This water should be fresh every day. 7. Scald all rubber parts daily H. Flush out vacuum pipes and tank with hot soda water daily. !». Removo bottom or t >p of vacuum tank daily; f pining tap is not sufficient. Taps of pipes should be givf'ti special attention and left open when nut in use 10. \fter washing, placo the milk buckets outside and expose them to tho sun and fresh air.

I hint's 1. Do not use kerosene tins to carry away milk. 2. Do not use lukewarm water where scalding is specified 3. Do not iiso a cloth for washing any dairy utensil; use a brush. A grave responsibility rests on all who are connected with the production and handling of milk for human consumption, and any act of carelessness which results in the contaminating of such milk may ultimately bo responsible for mortality or serious illness, particularly among infants.