Farm Dairy Instruction: Care of Milk and Cream

New Zealand Journal of Agriculture, Volume 79, Issue 3, 15 September 1949, Page 213

Farm Dairy Instruction: Care of Milk and Cream

By

W. G. Batt,

Supervisor of Dominion Farm Dairy

Instruction.

THOUGH the correct treatment of milk and cream before delivery to the manufacturing dairy will do much to retard development and multiplication of bacteria and avoid unsatisfactory flavours, it is essential that the utmost cleanliness of equipment and during milking is maintained to keep the numbers of bacteria to - a minimum and to confine those present to the more satisfactory types.

CONTAMINATION of milk or cream between the time of its extraction from the cow and its delivery to the manufacturing ,dairy is chiefly from four sources: — 1. From unclean methods of hand milking or stripping; 2. Direct contamination through the milk or cream coming in contact with equipment improperly cleaned; 3. Indirect contamination, caused by the milk or cream absorbing the smell of unclean surroundings, manure heaps, unclean woodwork, concrete, etc., and 4. During transport, by the milk or cream being agitated, in cans improperly cleaned or of pitted and unsatisfactory metal. Thorough cleanliness of the cow’s teats and udder and the hands of the milker is essential in both hand and machine milking. As hand milking is frequently done into an open bucket, contamination, from dust can be considerable, especially in milking sheds of the closed type and in those where hay and other fodders are fed to the animals. Any measures taken to reduce the prevalence of dust in and about the milking shed and milk room will bring an improvement in quality. Cleanliness of Air Supply to Shed Equal in importance to the cleanliness of equipment is the cleanliness of the air supply to the milking shed, milking machine, cream separator, or milk cooler. An air

supply impregnated with dust or affected by the unclean smell of insanitation will cause very serious contamination both by air-borne bacteria and by absorption and its consequent taints. During the milking operation the intake of air by the milking machine is immense, and it is essential that it should be from a clean source, if possible from grassed surroundings. Contamination of dairy produce by this means is very considerable, and especially during the summer months large quantities of milk and cream are affected. In many cases this is due to insufficient attention to the cleanliness of concrete and surroundings, but in a larger number the fault is due to an unsatisfactory layout of the dairy premises. Many concrete yards the exits from which are not concreted and fenced are arranged in such a way as to provide a permanent menace to quality, particularly where the prevailing wind carries contamination from these sources to the milking machine and releaser room. In no circumstances should the traffic of cows be allowed near the releaser room, and proper planning will provide against such a contingency.

Properly-planned Layout Essential

The objective in planning the layout of dairy premises is to provide against the possibility of contamination of dairy produce by unsatisfactory surroundings during the whole life of the milking shed, and this is simple if adequate attention is given to the fundamentals. A modern and properly-planned layout will ensure that the entry of stock to the concrete and their exit from it are confined to a distant point where the prevailing wind will carry dust and odours away from, and not to, the milking premises.

Figs. 1 and 2 show the front and back views of a walkthrough milking shed in which the cows enter the concrete holding yards by a concrete race Bft. wide and after milking are returned to this race and the grazing paddocks by an exit race 3ft. wide leading from the bails. The releaser room end of the shed is placed into the prevailing wind, ensuring that the air supply to the releaser and cooler is as clean as possible.

With the exception of the concrete races, the whole surroundings are grassed, providing the utmost cleanliness of air. There is no mud or cut-up surroundings at such a shed, and the maintenance of good-quality produce from such a dairy is very materially assisted. The milking shed shown in Figs. 1 and 2 has no open drain, the drainage fall of the concrete being to the Bft. entry race, from the end of which an open drain extends to a drainage sump. , Figs., 3 and 4 also show the front and back views of a walk-through milking shed in which the layout is arranged in conjunction with a central farm race which gives access to arid from each grazing paddock. The main concrete holding yard is placed at the end of the shed, and the herd of 160 cows enters this yard from. the farm, race and is taken to the crush yard in front of the bails as required. As the cows are milked they are returned to the farm -race by a concreted and fenced exit race 3ft. wide leading from the bails as shown in Fig. 4 and travel individually to the paddock intended for them. In this layout the concrete floors of the bails, exit race, and holding yards have one fall from the back of the race to the front of the yard, which is kerbed, and the only open drain leads from the front of the yard to the sump or cistern. ’ Here again, the area surrounding the shed is grassed, ensuring an air supply •as clean .as possible. There is no possibility of contamination from cut-up or unsatisfactory surroundings, and the only area from which dust can arise from the traffic of cows isat the farm race, but the risk of contamination from that source is negligible, because it is . distant from

the shed and arranged so that the prevailing wind carries dust away from - the, premises. If proper consideration is given to essential and fundamental points, the provision of a similar layout is simple. Where the erection of new dairies is contemplated careful and proper planning should be made to. achieve the objective of a clean air supply to the premises at all times. Such an arrangement is equally applicable .to the internal-race type of milking shed. Cooling of Milk As milk intended for manufacturing is released by the milking machine or delivered from hand milking it should be cooled immediately to a

temperature of 65 degrees F. or less or chilled by refrigeration. Surface cooling of milk and cream carried out in a clean atmosphere has special value, as it reduces animal heat and animal odour by aeration, and, more important, it reduces the temperature of the produce to a level at, which bacteria do not develop rapidly. This class of cooling, however, is undesirable under unsatisfactory conditions and in fact may be harmful, as the greater exposure of the produce to an unclean air will provide additional contamination. Clean, fresh air, is essential for aeration and cooling.

The cooling of cream as it leave* the separator has additional value, as its bulk or volume is contracted bycold and its consequent thicker consistency enables it to be transported with less agitation, which ensures better quality on delivery.

During summer, and particularly in districts with warm climates, there is considerable churning of milk and cream during transport to the manufacturing dairy. The condition is more pronounced in milk containing large fat globules, but is caused primarily by inefficient cooling or lack of cooling. Such a condition in milk or cream is unsatisfactory, as the churning makes it difficult to take a correct sample for butterfat testing, the quality is affected by oiliness, and generally a metallic flavour is imparted by the agitation of the produce

against the warm metal. Faulty treatment of this kind is usually costly and can be corrected by }®nt cooling, by filling the cans to a J, e \ el H y hl n c J rnSX ? th. vp£p T tn nL?t fhp frL Kin hnt Produce from toe sun. During hot a creai ? hl ’ a k?sepEated to ensure .ess agitation during anspo t. , se °‘ a Spreader Whether milk is .conveyed to the transporting cans mechanically or by hand, the use of a spreader which delivers an equal quantity to each container at the same time is an

advantage, as it provides a uniform quality and uniform fat content over each of the several cans. Frequent stirring of ■ milk with a metal plunger during the time it is awaiting . delivery to the factory is essential not only to improve quality by aeration, but to ensure a uniform distribution' of butterfat. The serum containing fat globules rises to the surface . of milk in the form of cream fairly rapidly, and causes an uneven distribution of butterfat, making it difficult to take a representative sample for testing purposes. This is considerable in those milks containing fat globules larger than average. Where a pronounced layer of cream has formed on the surface of milk agitation during . transport to the factory, especially in hot weather, may separate some of the fat from the serum, making representative sampling even more difficult and imparting an oily and metallic flavour. Judicious stirring of the milk . while it is awaiting: delivery . retards the formation of cream .on its surface, improves . the flavour of the milk by releasing undesirable gas, and ensures a better distribution, of? butterfat. If milk or cream must be kept some hours before delivery to, the manufacturing dairy, it is again highly important that it should be kept in clean, fresh air. Generally the greater the circulation of clean air at the milking shed, milk room, or separator room, the better is the quality of milk and - cream. The same applies most particularly where cream is not delivered daily to the manufacturing dairy, and ;it is essential that it. should be kept under satisfactory conditions away from the milking shed. Each skimming of cream should be held in a separate container and each thoroughly stirred with a metal plunger before 'mixing and . aggregating for delivery.

Effect of Agitation Broadly the more milk or cream is agitated against metal during transport the greater and quicker is the deterioration in quality, but this has greater application to milk or cream produced under unclean or unsatisfactory conditions. Though > it is desirable and advantageous to' have these raw . products delivered/ to the manufacturing dairy as quickly? as convenient and with as little agitation as possible, ? tests have shown that milk and cream produced under good conditions will not suffer if transport facilities are reasonable. Deterioration in quality during transport is greater in cans or vessels partly filled than, in those that are completely filled, as agitation is more intense.

The production and delivery ; of milk and cream of consistently good quality are achieved best by observation of the following points: ' 1. Ensuring ; that cows are , not in a heated condition . during milking, and encouraging... habit forming to ensure the contentment of cows by . the tranquillity of quiet regularity. 2. Insistence on the ; utmost. cleanliness of teats and udders of cows and the hands of milkers. - 3. Observing and maintaining the utmost cleanliness and sterilisation of all dairy equipment. 4. Ensuring that all metal used in dairy production is in good condition and properly tinned and that all rubber has a good-inside surface. 5. The provision and maintenance of a clean air supply to the ‘ dairy premises and provision against airborne contamination. 6. Using an efficient cooling system. 7. Spreading the milk over each of the several cans. ' \ 8. Frequently stirring with a metal plunger all milk awaiting' delivery. 9. Holding the milk and cream in clean, fresh air before delivery. , 10. Keeping each delivery of cream separate and by stirring with a metal plunger before aggregating. ; 11. Not mixing warm and cold cream. 12. Reducing agitation during transport.