QUALITY OF BUTTER

New Zealand Herald, Volume LXXIII, Issue 22449, 19 June 1936, Page 15

QUALITY OF BUTTER

THE RAW MATERIAL EFFECT OF CONTAMINATIONS BACTERIA IN MILK BY TAN The continued controversy concerning the quality of butter is an encouraging sign. One of the contributors to the press, Mr. W. Percival Levy, in a desire to get down to fundamentals, has asked a series of questions which are worthy of discussion. Tho bacterial content of bulked (pasteurised) cream to-day is certainly much less than the 150,000,000 per c.c. mentioned by Mr. Levy. Such a substance would not bo fit for manufacture into butter. Tho bacterial content of cream 25 and more years ago is not known for tho reason that dairy bacteriology was not practised at that time. Some information, however, regarding tho bacterial popidation of milk delivered to creameries is available as the result of a personal experience. An Early Example In 1911 a suggested method of sterilising milk for town supply through tho agency of an electrical current was tested. Samples were obtained from an ordinary farm supply to a creamery and after treatment by the sterilising process were sent to an analyst for bacteriological examination. Untreated samples were included. Tho analyst's report, dated July 27, 1911, was as follows: —" Nono of the specimens submitted contained any Tubercle Bacilli. Culture plates were made with four dilutions of one cubic centimetre of each milk specimen with tho following average returns:—No. 1 (milk), 3440 organisms per c.c.; No. 2 (milk), 2420 organisms per c.c.; No. 3 (milk), 7500 organisms per c.c. The pathogenic bacteria present consisted of Streptococci and Bacillus coli communis, the former of which is commonly, and the latter always found in milk, in quantities varying with the cleanliness observed in milking. . . . The results obtained are remarkably low. . . . exceptionally clean samples of milk." It must bo noted that this milk was not cooled and represented an average factory supply in that district. Tho samples would bo about 12 hours' old when subjected to bacteriological examinations and were kept at atmospheric temperatures during that period of time. With milk of this quality delivered to factories one can understand why butter made from its cream possessed such an attractive, natural flavour. Pasteurising Temperatures It also furnishes an answer to Mr. levy's next question.—ls it not a fact that if the cream contained a lower bacteria (acidity) content a relatively higher percentage of natural flavour would be retained in tho manufactured article 9 If the milk and cream were of this quality I liave mentioned to-day the present high pasteurising temperatures would not bo necessary and a more natural flavour in tho butter would be secured —much superior, in fact, to that of somo exhibits at a recent winter exhibition, the flavour of which, in the judgment of experienced dairy workers, registered the zero of absolute flatness. A few words regarding tho action of bacteria are necessary in connection with tho next question: If the bacteria content (acidity) of the cream today is higher than that of 25 years ago, what is tho cause of such rise? .All types of these organisms do not produce acidity in milk. In fact some are anti-acid and are responsible for a sweet curd, slimv milk and other conI taminations. Others again aro gas formers, while a number constitute the putrefactive group. Yeasts and moulds produce bitterness and other undesirable flavours in milk and cream. Under right production methods beneficial bacteria predominate and establish themselves to tho exclusion of undesirable types. New Factors What is tho cause of increased contamination of milk and cream to-day notwithstanding many improved milking sheds? Under our present methods of production three entirely new factors have been introduced, the effects of which upon the quality of milk and cream have not been ascertained in a conclusive manner. I refer to the use of milking machines, the separation of cream on tho farm, and the excessive stimulation of pasture growth by the indiscriminate use of largo quantities of artificial or inorganic manures.'Little is known about tho effect of vacuum pressure upon tho warm butter-fat structure, while the sanitary condition of the pipe system is still an enigma, and oiui of our greatest handicaps to quality, for 110 standard of sterilysis has yet been established to which all milking machines must conform. The average care of cream on tho farm, an acute problem in itself, is a problem which awaits a solution long overdue. Excessive stimulation of pastures promotes a rapid growth of tho plants far in advanco of earlier years and this must exert an influence upon the but-ter-fat structure and its natural and characteristic flavour and aroma. As it is sometimes difficult for cream graders to distinguish between feed flavours and bacterial contaminations it is not practicable to separate these two issues entirely. Cream may have a strong feed flavour with a low bacterial count and vice versa.

Under our present grading system cream may contain a high latent bacterial contamination and still bo graded finest quality. The reason is that the bacteria present liavo not had time to develop and affect tho cream. Hence we find apparently good cream coming out of a "dirty" shed and plant. The obvious remedy for these anomalies is simple bacterial checks such as the natural curd test at tho farm, and ripened cream samples at the factory. These reveal latent contaminations and would improve tho present grading system to that extent.