QUALITY OF MILK.

King Country Chronicle, Volume XXVI, Issue 3444, 17 March 1932, Page 7

QUALITY OF MILK.

STORAGE AND COOLING. ADDRESS BY MR. P. 0. VEALE. At the dairy factory managers' conference held at Patea recently, Mr. P. O. Veale, dairy research chemist at Hawera, gave advice to the managers present on the quality of milk, proper cleanliness, and the effect of storage and cooling. Mr. Veale said that as milk grading was to be instituted, a'nd as Mr. Singleton was to address them on the subject, he would give the members some suggestions as to how they could avoid unclean conditions and describe some of the causes tending to contamination, so as to help them in their operations on the farm and in the milking shed. He gave them three classes of possible trouble: (1) Material and visible dirt; (2) dirt in the equipment of the shed; (3) imperfect cooling and storage overnight.

Speaking first of the material dirt, he said that this might not be very serious, because in many cases in Tarahaki it was caused by a sediment that was mainly fine sand or dust, a sterile matter that was insoluble and contained no bacteria. Milk with this sediment might be quite satisfactory in the cheese vat, but he did not say this to approve

of dirty surroundings. But the dirt could be removed by filtering, whereas no filtering would catch the germs of bacteria if present'in the milk. He stressed the importance of being particularly careful with the night's .milk.

Need for Cleanliness.

Referring to the need for scrupuI lous care with the equipment—cans and machines—Mr. Veale said that | carelessness would be extremely detrimental. In finest milk, for human consumption and under the strictest methods, there were seldom less than 10,000 bacteria to a cubic centimetre, i and, if given a chance to multiply, these would soon deteriorate the milk. With hand milking in an average shed, the number w,as much greater, and this would quite likely be overlooked in the cleaning process. The chute would be clean on top but the milk would be contaminated at the bend. Little unconsidered trifles like these were a fruitful source of trouble. Mr. Veale then referred to the question of storage and cooling which was the greatest field for research into the causes of unsatisfactory quality. The shed might be clean and looking well, and the last word in conditions likely to affect quality, and yet there might be contamination. He added that there were two causes contributing to quality: (a) the condition under which the milk was produced, and (b) under which it was kept, and of these, the second was by far the more important. Even in a cooling machine, germs might multiply, and therefore how much more under ordinary temperature on a stand. Generally, the milk graded according to these conditions. Milk Not Cooled. He gave instances in the shed of a farmer with a large herd, where conditions were otherwise very good and hygienic, but where trouble was caused as the result of the great amount of warm milk going through the machine, and which never got a chance to cool. The supplier provided a wooden cover to his chute, and this tended to defeat the idea of the chute and to allow less cooling than would otherwise be the case. The cover tended to prevent the aeration and cooling which should result otherwise. The cover would keep out dirt from the air and from birds, but would not allow the escape of the natural gases and permit ventilation.

Referring to temperatures, he said that trouble occurred with the night's milk, which had to stand a number of hours. The ideal temperature for this period was 50 degrees or below, but this was hardly ever achieved. If kept at 60 degrees, there would probably be a slight drop in quality, but generally finest would be secured. A temperature up to G 5 could be tolerated under very special circumstances, but 70 was not so favourable, and the slightest slip in the ordinary procedure caused the bacteria to get away; over 70, the supplier would have great difficulty in dodging second grade. The bacteria would be active and would multiply faster as the temperature rose. Sheds and equipment might be of the best, but if the milk could not be cooled all the work went for nothing. The cooling was the most important factor, and he added that the water could be taken away and used for other purposes in the shed to avoid waste.

Generally, he said, in conclusio'n, where trouble was experienced the storage and cooling of the night's milk was the question to be faced first and foremost, and, in case of trouble, should first be examined by the instructor, for a failure in this respect might undo all the cleanliness on the farm and in the shed. In reply to a question, Mr. Veale said the methelin blue test was reliable to a point, and was valuable in reflecting generally the quality of the milk, but it had its limitations. Milk strongly aerated sometimes tended to hold up the blue and "flattered" itself as to grade.