MILK UTENSILS NEED FREQUENT CLEANSING.

Star (Christchurch), Issue 18045, 4 January 1927, Page 6

MILK UTENSILS NEED FREQUENT CLEANSING.

HEALTH DEPT. GIVES ADVICE TO FARMERS ON STERILISATION (Contributed by the Department of Health.) This article is written more particularly for the information and guidance of dairy farmers in country districts to achieve their aim to turn out mik as clean and free from contamination as they possibly can. Milk is one of the most nourishing and most delicate of all foods —nourishing because it supplies all the constituents necessary to support life, and delicate because it is prone to undergo deleterious changes if due precautions are not observed in its handling. These changes arc chiefly induced by germs or bacteria, and as cleanliness is the main factor by which the number and species of such germs may be kept under control, cleanliness in the handling of milk is of the utmost importance. Except that first drawn from the teat, milk as it exists in the udder of the healthy cow may be considered to be practically free from germ life, milk may be drawn from the udder of a healthy cow, but in ordinary practice milk is more or less exposed to bacterial contamination, and this is the reason souring and other changes take place. By far Ihe greater number of bacteria in milk come from ordinary dirt, and may be kept out of the milk by cleanly methods of producing and handling milk. Milk is one of the best media used in the laboratory for growing bacteria, and the few bacteria that are found in even the best of milk may therefore multiply to millions and may make the milk unwholesome unless great care is taken to prevent their growth and increase. PRODUCTION OF CLEAN MILK. The cow must be healthy; the shed must l>e clean, well lighted and ventilated, and the surroundings also should be clean. Any operation likely to produce dust before or during milking, especially of hand milking, must be avoided. The cow must be clean and washing the udder and flanks with water gives the best results —after washing the udder and teats must be wiped with a clean damp cloth. The milkers' hands and clothes must be clean. In hand-milking, the milk pail should have as small an opening as can be used. The first stream of milk from each teat should be rejected, and the practice of wet-handed milking

should be avoided. The milk should be moved from the cowshed immediately after milking for straining and cooling. Tt shoul dbe handled in a clean, air}*, well-lighted shed kept solely for the purpose. The milk must be cooled to 50 deg. F. where possible, otherwise to the lowest temperature obtainable. It should be kept as cool as possible in closed vessels during storage and transit. The milking utensils, including the cooler, should be well rinsed with cold water immediate ly after use and after rinsing, the utensils should be thoroughly washed and scrubbed with hot water to which soda has been added, and afterwards rinsed in clean water and sterilised by steam. Sterilisation depends entirely on heating the utensils to a sufficiently high temperature for a sufficient period of time. Scalding will not sterilise. After sterilisation the utensils must be protected from contamination until required. Straining cloths and udder cloths and everything that comes either directly or indirectly in contact with the npilk must be washed and sterilised after each milking.

WHEN STRAINING SHOULD BE DONE. Straining should take place before f cooling, which should be done as soon as possible after milking and invariably in a pure atmosphere. The value of a straining cloth is frequently over-rated. The. straining cloth strains out visible dirt to a considerable extent, such as particles of grit, straw, etc., from the milk, but, bacteria are far too small for any straining cloth to prevent them from passing through. Tt is, therefore, useless for the purpose of removing bacteria that have already gained access to the milk. If a cloth is used that \ has not been properly washed and i sterilised since it was last used, bar- ; tcria will have bred and multiplied on the cloth, and it will thus be a fertile source of contamination. Where there is any risk of the straining cloth not 7->eing properly sterilised after each milking it is better to use a cotton wool disc. These discs are cheap enough, and after use can be thrown away. The quantity of the dirt strained out of the milk is visible on the strainer, and is an excellent guide as to the quality of the work being done in the cowsheds. Butter muslin is not an efficient strainer, even when several thicknesses are used. A straining cloth is far more effective, and this has to be washed and thoroughly sterilised by boiling or in steam and new ones frequently used, otherwise bad results will be obtained. The metal gauze strainer keeps out the grosser impurities, and requires the same care as the above. Do not attempt to strain too. large an amount of milk without changing the strainer or straining material. If this is done the latter part of the milk poured on it may have the effect of washing through dirt with bacteria, which has been strained out of the previous milk. J he strainer may be a means of infecting a large quantity of good milk by a small amount of bad milk. COOLING PROCESS. It is almost impossible to produce milk free from bacteria or to destroy all bacteria by pasteurisation. .Tt is, therefore, necessary to prevent bacteria from multiplying in milk, and the only allowable method of preserving milk is by cooling it. A low temperature restrains the growth of all kinds of bacteria. The degree of temperature needed to preserve milk will depend greatlv on the length of time that the : milk is to be kept. The marked 1 effects of temperature arc well recog- ' nised, and everyone is aware that milk keeps better in winter than in summer. * The higher the temperature the more readily do coliform bacteria - multiply, and these bacteria readily 1 cause souring and curdling of milk. 5 Milk to be safely kept should be L cooled immediately after milking to 50 degrees Fahrenheit or lower, and with the exception of the necessary heating , for pasteurisation should not subsequently be permitted to exceed that ’ temperature. The maintenance of a » jow temperature alone will not ensure a low bacterial content unless the milk is clean to start with, but on the other v hand maintenance at a comparatively high temperature, such as 60 to 70 deg. ’ Fahrenheit, is likely to result in a high i* content even with an originally “clean” milk. During a part of the winter months there may be little difficulty to cool to 50 deg. Fahrenheit, but in sum- ~ mer months this temperature in many ) cases, especially in the North Island, is only possible with the use of ice. Ob- } serrations in Auckland have shown ) that, for six months of the summer the average temperature on delivery of raw milk was 70 deg. Fahrenheit, and for six months 57 deg. Fahrenheit. Where the water supply is derived from a deep ’ well the difficulty is less. If a demand I- for ice could be established, possibly ) J the cost of production of ice might be ' lowered ami its use encouraged, es-

pedal ly at farms within easy access of a city. If the temperature of the milk is lowered sufficiently at the farm, the temperature of the outer air does not affect it markedly during transit except when it is exposed to the direct sun’s rays or in an excessively warm atmosphere. Milkcans are frequently left by farmers at the side of the road to await collection by the depot wagons and arc frequently exposed to Ithe direct rays of the sun and to dust. This is frequently the case also at railway stations. Covered motor wagons are fortunately superseding open carts, and by this means transport to the cities is accelerated. In retailers’ premises in the towns there should be no difficulty in imposing a definite standard of 50deg F., at which the temperature of all milk for sale should be kept. In houses the use of the ice chest for storage of milk should be more general. It is important for the public to recognise it has a duty also in the matter of storing the milk in thoroughly clean receptacles and keep it stored at a low temperature, and protected from flies, dust and odours. MILK COOLERS. Milk coolers offer a large surface for the contamination of the milk. If the cooling is carried out in a proper dairy where the air iS" pure the number of organisms gaining admission is small, but in cases where cooling is carried out in a dirty cowshed or in dusty places serious pollution has to be considered. On the other hand, coolers are frequently found in a dented or damaged condition, which makes it practically impossible to keep them clean. Many have repeatedly been repaired with solder, and it is seldom that a smooth surface has been left. It is advised that coolers be fitted with metal covers: these covers fit one on each side of the cooler and protect the milk from dust while in use. They are easily removed for cleansing, and they do not interfere with the cleansing of the cooler itself. In regard to coling on a large scale, where certain types of pasteurisers are used, milk can be left in the pasteuriser, after having been heated to the requisite temperature for the required time, and cooled by passing the cooling mixture through the coil. This means less handling and also prevents exposure of the milk to large surfaces or to the air, and.is a great improvement in this Yespect on the use of the ordinary surface coolers. MIXING MILK. It seems hardly necessary to point out the injurious effects of the addition of stale milk to fresh milk, but fresh milk is often spoiled in this way. The mixing occurs where a milkman mixes the remnants of his morning delivery with the fresh milk received by him in the afternoon or the following day. The consequence is an immediate increase in the number of bacteria and a considerable reduction of the period during which the milk remains useful. Apart from this, indiscriminate mixing of various grades of milk at milk depots, etc., results in comparatively clean milks being depreciated by dirty ones. N.B.—Other aspects of this subject will be dealt with in a future article.