FAT IN MILK

New Zealand Herald, Volume LXXI, Issue 21911, 21 September 1934, Page 5

FAT IN MILK

SEPARATION LOSSES USE OF BABCOCK TEST MODIFICATION OF PRINCIPLE nY PAN No. 111. In addition to testing whole milk and cream the Babcock method is also used to determine the amount of butter-fat remaining in skimmed or separated milk, buttermilk and the whey obtained in cheese-making. Until recent years the procedure was the same as when testing whole milk excepting that a special bottle was used and rather more sulphuric acid was added to the sample of milk. As time went on, more consideration was given to the loss of butter-fat in separation and it was found the ordinary method of testing was not quite accurate in that the finer globules of butter-fat in the sample were not recovered and brought into the graduated neck of the test bottle. After some research work it was discovered that the addition of a small quantity of butyl alcohol had the desired effect, and results from the use of this method were satisfactory. Working under this system the operator now measures 9 c.c. of skim milk, 2 c.c. of butyl alcohol, and 9 c.c. of sulphuric acid. New Zealander's Part Credit must be given to a New Zealand worker, Mr. W. E. Hughes, formerly of Hamilton, but now of Melbourne, for his part in perfecting this modification. As the result of his researches it wag established that the best results, as compared with gravimetric analysis, were obtained when the following rules were followed:—Periods of whirling ten, five and three minutes, hot water being added as usual; speed of centrifuge about 200 r.p.m. greater than the ordinary rotation; while the temperature of the sample during whirling must be maintained. The steam turbine type or Babcock centrifugal machine fulfils the latter requirement. Operators of this test who obtain results which are obviously too low may follow the above rules with advantage. It has been asked what relation do the results from the butyl alcohol method bear to those obtained from the former one. There is no relation at all. Quite a mass of information has been accumulated upon this point, but two examples must suffice. Two samples of skim milk from farm cream separators were tested under the old method and the result in both cases was .02 per cent. Tested by the butyl alcohol modification the test of one sample was .08 per cent and of the other .10 per cent. This showß how misleading results from the old method were, and the need for the improvement obtained under the new routine.

Using the butyl Babcock method a readjustment of skim milk test values by dairy farmers and others has become necessary. Instead of .01 per cent or .02 per cent a reading of .10 per cent must be regarded as indicating good separation, while .08 per cent is better still, but seldom obtained. Lower readings than these must be regarded with a certain amount of suspicion unlesa checked by gravimetric analysis. At one time, as the result of such check, it was not considered right to record any result lower than .08 per cent. This rule could with advantage be revived, and readings lower than this verified by the Rose-Gottlieb or other standard fat-extraction methods. Mechanical Improvements It must be remembered that when the Babcock test was perfected the mechanical separation of milk. from cream was practically in its infancy and high >kim milk butter-fat tests were common. Creain separators had hollow bowls without discs or other apparatus inside to make the separation of butter-fat really exhaustive. Consequently skim tests of .25 per cent and higher were met with and excited no comment. At these higher values the old method is more reliable and giveß results which compare fairly well with gravimetric analysis. Having regard to the low value then placed upon skim milk and the butter-fat which it might contain. Dr. S. M. Babcock was justified in regarding his test as quite satisfactory for skim or separated milk Modern improvements to the separator bowls in the form of devices for dividing the milk into thin sheets have also doubtless had the effect of breaking into smalled particles the globules of fat which escape into the skim milk. This would explain the partial failure of the old testing method for separated milk. As modern improvements have somewhat altered the circumstance of cream separation, so a modification in testing practice has been devised to meet the new requirements. Advantage of Changes For the testing of whole milk and separated cream the Babcock test is reliable and satisfactory and the changes in connection with the testing of skim milk, butter-milk and whe\ simply bring it up to date in respect of these fluids. This is an advantage to dairy farmers and also a great help to factory managers, all of whom can now keep a check upon losses in separating and manufacturing processes. In any calling or profession it is well to have definite standards of work. It eliminates guessing and haphazard methods and introduces system and so conserves our energy and produces the best results. The dairy farmer, therefore, should set a limit to separation losses, beyond which ho steadfastly refuses to go. This limit could very well be fixed at .10 per cent, rather less than more. Frequent tests of skim milk should be made with this object in view. Likewise the dairy factory manager, using this test regularly to check the loss of fat in the butter-milk, should have a maximum figure as a guide. This could reasonably be fixed at, say, .66 per cent, free of added water and every effort made to keep the loss within the neighbourhood of that figure.