BUTTER FAT

Nelson Evening Mail, Volume LVI, 18 November 1922, Page 2

BUTTER FAT

THE THEORY AND PR INCH’LEE OF

ITS ESTIMATION

(T>.y ilatterfat.)

f Milk-, which is one of our most important. primary products; contains fat, surrar. compounds of nitrogen mid proteins, and small quantities of mineral snlrstitln-es. Of these various constituents fat. is perhaps the most important* and more attention lias been paid to the estimation of the fat in milk than that of , any other of its constituents. Fat appears hi milk as very small globules or particles, which being much lighter, than (the medium in which they are suspended 'biivo-a Uditleltcy to rise to the surface, tin which fact depends ihti separation of bream by skimming. Cream, iti which form we tire most familiar with butter ' fat, consists of the globules of fat toge ther with a proportion of the aqueous ! portion of milk adhering to them, and it is obtained either by "setting” the milk .or by mechanically separating it.

The methods of estimation of fat are very numerous and may be divided conveniently into three classes:—

1. Gravimetric methods, ill which the fat is separated from the milk by a suitable solvent, arid weighed after evaporation of the solvent. 2. Volumetric methods, in which the fat is separated from the milk by suitable means, and its volume measured.

3. Indirect methods, in which the amount of fat is deducted from the determination of some, physical property. Of those methods Gravimetric ones arc undoubtedly the most accurate, but they are all to a certain extent of a tedious nature and are not generally used except where very exact results live required for legal purposes, or in the ease of disputes. In passing, it is interesting to note that the majority .of Gravimetric methods depend on the fact that if milk is dropped on blotting paper it spreads out to a much greater extent ihan is possible in a basin or even on a flat surface of glass. The indirect methods are of no great scientific or practical value, but are useful to use- conjointly with other methods. This type of method is exemplified by allowing milk to stand in a specially graduated vessel and measuring off the volume of cream thrown up, but it is naturally of little use in the accurate determination of the fat in milk.

The most important methods of fat determination from a practical standpoint are undoubtedly of a. volumetric nature as they nave placed milk testing within the reach of the 'average dairy farmer of limited moans and leisure to devote to the subject, although herd-testing should be as integral a part of a dairyman’s life ns is milking—dairy science is unfortunately as yet in its infancy in this Dominion. The chief methods of this kind are the Babcock method and the Gerber method of which the latter is generally considered to be quicker and to give more accurate results. The Babcock method which consists essentially in treating the milk with an equal volume of strong sulphuric acid, and separating the fat by whirling at a high speed or centrifuging, as it is known, has a serious objection in the time spent in whirling, and the Gerber qiothod was evolved to remedy this defect. Tiv testing milk by the Gerber method 10 c.c. of strong sulphuric acid are run into special graduated tubes or “acido-butyrometers” followed by 11 c.c. of the milk sample, well mixed," care being taken to inn the milk down the sides of the tube to prevent it mixing with t!ie acid. One c.c. of amyl alcohol is finally added to assist the fat to separate out and the bottles arc closed with rubber stoppers, well shaken to ensure that the contents are thoroughly mixed, and whirled in a centrifuge for 2-3 minutes at approximately 600 revolutions per minute. The amount: of fat can now be read off from the scale on the tubes and the determinations thus obtained are almost identical with those from standard gravimetric methods. The same principle is employed for skim milk and cream in special tubes with very satisfy, lug results.

When it is considered that a cow producing not more than 175-lb of butter per annum, bo-ides being cared for and fed at a loss, would eat up the profit made by a cow' producing 250-Ib per annum, assuming all butter over 226 ib is clear profit, it behoves dairymen to give the culling of their herds the most serious consideration with the facilities and advantages of modern dairy science at their disposal.