HYGIENIC DAIRYING.

Hawera Star, Volume XLVI, 22 July 1926, Page 6

HYGIENIC DAIRYING.

CORRECT SHEIMBISIATI ON

METHODS

LECTURE BY MI!). P. O. VBA BE.

-GNIr. DP. O'. Voale, -tho .seieiitivsit at tlie Hawem Dairy Laboratory, delivered a further laet-ure yesterday o-u dairying. There uvas a good laititcndanoe of dairymen, and) girl students of the. Technical School home science classes. Mr. Veale dealt with the special relation of bacteria to dairy u-teiiusils and cleaning. Mr. T. A. Winks presided. Air. Yea to commenced liis address by saying that milk normally contained many millions of bacteria, to the cubic centimetre, 95 per cent or more being of itihe .hiarunjleisls lactic acid variety. A problem for the dairyman wa.sl to. remove these effectually. Mr, Veale proceeded to define sterilisation as it was understood in the laboratory, and instanced three methods. Hot air sterilisation of glassware, dishes and vessels: (2) the autoclave sterilisation of media; (3) fractional sterilisation of media by .steam. OBEIAiN! BUT NIOT STERILE.

Arriving .at sterilisation as it applied to the dai-y farmer land factory manager, the speaker dealt oomprehensiveiy with cieammesis which did not amount to sterilisation. If farm, methods were to bo any good, they must follow the lines adopted in the laboratory. The first laispect of cleanliness which did_ not amount to .sterility was the presence of a layer of dried, milk in cans, which arose from insufticienib water during the (Washing process. A second fault was the presence of a layer of fat on the inside of the cans. This might- arise from neglect to- use soda, or of using warm water for washing at too low a temperature. If a. piece of tissue- paper were taken and rubbed on almost any cleaned can on a stand a. translucent -spot would show on the paper at .the point of rubbing. A thin Jayer of grease was more common than dried milk inside the cans. Another common fault was the presence, of a thin layer of albumin. This occurred when the vessels had -been cleaned with hot water first, instead of cold. Boiling water did not -necessarily destroy the spores of moulds, the presence of which precluded, sterility. A further cause of complaint was the use of insufficient changes of water. The habit of pouring the water from one oa-n to another at washing, should not be followed. Sour milk contained up to 20,000,000 bacteria per cubic centimetre, and -a drop of this, in a- can would contaminate much washing water.

“Slimy” milk, and “fruity” whey, were caused by unclean utensils. Such troubles might get into a factory and resist -a,ll efforts to eliminate them. “CEIRTIETEID” MILK.

In England .and America it was customary to provide “certified” milk, milk, guaranteed l to contain a minimum q-f bacteria, and for which a. higher price wa-s paid than for the ordinary article. This custom did not obtain yet in New Zealand, lb lit it was due -to come. Elsewhere the- public had been educated to- demand the “certified” milk, which was guaranteed free from disease ,especially tuberculosis. Heavy fines were imposed if the grade fell below “certified” -standard. ‘ Great •precautions were taken by purveyors <>i this article to cleanse,and sterilise- their utensils. The practice followed elsewhere in. -securing this high grade milk for ftho public wa-s: -Firstly, to wa-sh with cold water to remove the albumen ; secondly, wash with hot water and caustic -soda to -remove, the layei of fat Which protected bacteria in and below it; -thirdly, wash with several changes of boiling water. (This was a.s far (as things went in New Zealand, and if -properly carried out it was assumed -that the can was quite clean. Abroad, however, the process was continued.) The cans were then sterilised by steam at -a temperature of 2T2F or 100 C.. the process being continued for 10 to 15 minutes for each can. Then all -the (bacteria, which had resisted -previous cleanings would bo killed. Chemical methods were crude, and the presence of, -say, ammonia could he detected when diluted to a millionth part.

STEAM STERILISATION' TO COME

In actual practice it was impossible to remove bacteria by water. Steam was the only adequate means. The practice of using it was not general in New Zealand, and perhaps it would not become so until the trade' in “certified” milk was established. This high grade milk could not contain more than 10,000 bacteria to the cubic centimetre, which in itself showed the extreme difficulty which existed in getting rid of bacteria from milk and its surroundings. However, the cold water, hot water with caustic soda, followed! by boiling water, if properly carried out, should he sufficient for cheese factory produce under present conditions. The speaker condemned the. practice of taking home hot water in the cans from the factories. No matter how hot it- was at the start, and how near the farm, the water could not be kept boiling. Any defect such as “fruitiness” would be perpetuated. Another had practice was taking home whey in milk utensils, and unless extreme care were taken the following day’s mlilk supply would ho contaminated.

Instead, of being given to suppliers to take home, the hot water at the factories should he used to pasteurise the whey and prevent the spread of tuuerculosis bacteria to the cheese in tbe factory and to other herds. RE-CONTAMINATION.

Another danger point wais re-con-tamination of vessels after they had once been cleaned. This was a very real contingency. A can was frequently stood upside down on the milk stand, where dirty hoots caused contamination. If placed on a support, flirt and dust frequently had access to the cams. It was a common thing for the milk chute to project into the stand, and liquid that missed the cans went down below and congealed in a mass l of bacterial contamination. Such congealed milk sometimes had a red tinge, and this bacteria entering milk bad been known to give a rod tinge to that also. The best remedy was a well cleaned concreto floor. Cans standing with water in them, or even mouth up, were sources of rccontamination. Lids were another source of recontamination. They were often treated in a perfunctory manner, thrown around off-hand, and allowed to pick up much bacteria. FOUL STANDS. It was no uncommon thing early in the season to see young calves killed, skinned, and the carcase thrown down near the stand. It seemed remarkable that so abominable a practice could he followed, hut .such was the case. t MILKING- STANDS. Mr Veale then went into the correct type of milking machine installation. In the first place, more often than not the- farmer did not make' the best use of the lie of his land. Sheds were placed in foolish positions, which gave trouble afterwards. One essential was the provision of an adequate deep drain behind the cows. As a ! rule the drain was either absent altogether, or

merely a shallow depression. To be ef-' ficient, flit drain should bo 10 inelie-s deep, and! have a curved section. The fall should- be in! the direction: opposite to the milk stand, instead of, a-s was frequently the ease, running out at the same end as the milk .stand. Ihe yard should have a straight fall towards the shed, and the drainage of both yard and shed should' join- a drain, running between them and at right angles to both. Cows- leaving t-h-e -shed .should go up hill. When they went down hill, a series of .steps were formed, which eventually, for the safety of the- animals, required the construction of concrete -steps. The .speaker knew of one place where it liaw been necessary to install no less than three such steps-. If the arrangeipent of the- shed permitted the cows to leave it on am uphill -slope, a. concrete ledging should bo laid down for them to pass over. This would make easier drainage- and washing. ' ERECTING THE PLANT. In- the erection of their milking plant, the farmers’ real interests were not always considered by the machinery companies. Lifts .should be avoid u ed, but frequently the need for them was not obviated. The milk pipe should have a fall of about three- inches to ensure that it drained cleanly. Too high an erection- should be avoided. An ideal height for the plant- wa-s sft 9in. The releasor should have a drop of 14 inches, and along the 30 feet of chute the fall should he half an inch a- foot, giving a total of 15 inches. This ensured a continuous flow, without being so rapid as to prevent cooling, or the production of froth in the cans, and a churning effect. Some form .of distributor was required, say -six inches in depth. As the cans were about 2ft 7in high, the foregoing measurements gave the. best conditions. This type should he possible of attainment on most farms. VACUUM TANK. The construction of the vacuum tank and the releaser was not always -good. A broken inflation drew the. milk, round the vacuum -system into the vacuum tank, and nearly -always flooded the releaser, with throe -separate entries to the vacuum tank, namely, the pump, vacuum pipe system, and the releaser. • CLEANING MACHINES. The principles for cleaning machines were, m general, the same as those which applied to utensils. If the milk pipe were properly -arranged all would go well. The flushing of the machines with cold water was generally resorted to, and little .notice was taken of the two or three per cent, of water which might vet into tile- milk as a -result. The cold water prevented the milk from adhering to the apparatus. The use of cbkl water after milking took away the albumin, which was not affected by the caustic soda. Brushes scratched the surface of the rubber, which became a lodging ground for albumin-. Heat and cold contracted and expanded tlie surfaces. Bacteria got in, and the rubber closed on them. \

Referring to the care of teat cups before milking, Mr Veale said that in America -a custom obtained of dipping the cups in a. -sterilizing solution of strong brine- or hy-drocloride. The idea wa-s; to prevent the growth of bacteria during milking. The practice was not altogether sound, because it presupposed the presence of bacteria which should have- been obviated by a proper -prior system of sterilization.

SUN AND OXYGEN

Very few bacteria cultures could resist the effect of the sunlight and oxygen combined. The projection of water into the air was followed in fill umber of continental cities for -purification purposes. There -was no better system of -sterilzin-g milking machine parts than to. treat them with cold witter, hot water or caustic soda, boiling water, than hanging them up in a dry, sunny place. The use of disinfectant solution led farmers to believe that there was no need for further .sterilization. Fat and albumin, however, protected bacteria from disinfecting solution; and, besides that, if the solutions were not renewed, they became -actual agents for augmenting bacteria.' Without speeia-l facilities, the farmer could not say whether his solution had lost -strength •or not.

Messrs Winks r,.nd Taylor (Low garth) thanked Mr Veale for his lecture.

The chairman, said the final discourse would he o-iven next Friday at 2 p.m., when Air Veale would take for his 'subject “The Pasteurisation of Alilk for Cheese-making.” Tbe proceedings then terminated.