THE ACIDITY OF CREAM.

New Zealand Mail, Issue 1291, 26 November 1896, Page 5

THE ACIDITY OF CREAM.

Accuracy is rapidly superseding guess-work in the creamery, and among other improvements in butter-making is that of churning at the point where the degree of acidity is right for best results. In ripening cream the milk sugar in the cream is converted into lactic acid. Considerable work has recently been done to determine the influence that the amount of this acid produced, or, in other words, the degree of ripeness, has upon the quantity and quality of the butter. The production of lactic acid is the result of activity of the lactic ferment, and the rate at which it is produced is affected by <he following conditions :

1. The richness of the cream ; for the more milk left in the cream the greater will be the amount of sugar of milk, the source of the lactic acid, and will contequently develop more acid in a given time than cream containing a larger amount of fat and with correspondingly less water, sugar, and casein.

2. Temperature at which the cream is held.

3. Condition of the atmosphere. Hot muggy weather tends to hasten ripening, while clear, bright, and cold weather retards it.

If sufficient acid is not developed, the crstun does not admit of as exhaustive churning at the low temperature now generally adopted by butter makers. The qualities of a full flavoured butter are also not so well developed. If the cream is overripened, putrefaction follows the normal fermentation, and the result is an inferior quality of butter. It is obvious from the foregoing that in order to secure uniformity in churning and in quality of butter some simple test should be employed. Formerly, the degree of ripeness was determined by depending upon the length of time that the cream has been standing, and by taste an J smell—guides that are not always safe to rely upon. Two very simple and inexpensive methods of determining the degree of aoidity of milk and cream with accuracy are now used in many creameries. These are the Mann's acid test and the Fanington alkaline tablet test. Both bear the names of the scientists who introduced theni. They are not patented. THE MANN'S TEST. i i The necessary apparatus consists of a 50 c. c. pipette, a 50 c. c. burette, and a glass stirring rod. The chemicals used are a standard neutraliser, which contains a known quantity of alkali,and a solution indicator. In the manipulation of this test, stir the cream thoroughly. Fill the pipette to the mark and transfer to a glass tumbler, rinsing the pipette with warm water (if possible use distilled water), putting the rinsing water in the tumbler with the cream. To contents of the tumbler add three drops of the indicator (phenolphtalein). , The burette, which should be fa.stener\ upright to a support, is then filled to the 0 mark with the neutralisec {"alkali solution). While constantly stirring the cream, allow the solution to flow slowly into it until the contents turn to a pink colour. Stop adding the solution the moment the colour becomes permanent. By experimenting with this test it has been found that the best results are obtained where the cream is ripe enough to require 38 to '

42 cubic centimeters of the alkaline solution to neutralise the acid it contains, which is found by taking the reading of the level of the solution in the burette. THE FARRINGTON TEST. The necessary apparatus consists of a white tea cup, a 4oz, 6oz, or Boz bottle, and a No. 10 brass cartridge shell. The neutraliser is prepared by dissolving one of the Faningtom alkaline tablets in loz of water. The cartridge shell is filled with cream and. poured into the teacup, to which is added the same measure of neutraliser.. If no change in colour is produced*, another is added, and so on, until at pink colour is produced. The percent Hg« of ncid in the cream is then* equal to one-tenth of 1 per cent, multiplied by the number of measures of the neutraliser used. By this test the cream is about ripe enough when it contains six-tenths per cent. acid. In preparing the neutraliser, fill the bottle with water and drop in a tablet toeach ounce capacity of the bottle. Thecost of each tablet is about one-tenth of a penny.—American paper.