FIG. 4.-Changes taking place during seven days in the nitrogenous constituents (water-soluble at room temperature) of fresh, cold-stored, and preserved chicken meat.

6.41 39.69

1. 13

1.00

REPORT ON THE ADULTERATION OF DAIRY PRODUCTS.

By HERMANN C. LYTHGOE, Associate Referee.

The referee, with the help of Messrs. Nurenberg and Marsh, assistant analysts of the Massachusetts State board of health, has made a study of the different methods for the preparation of milk serum and for the detection of calcium sucrate in cream. As a result of this work it is apparent that the provisional method for the preparation of milk serum needs no modification, but the method of Baier and Neumann for the detection of sucrose in milk or cream should be made provisional. The work done is embodied in the two following articles.

A COMPARISON OF METHODS FOR THE PREPARATION OF MILK SERUM.

The samples of milk used in this investigation were all milked in the presence of an inspector or an analyst of the Massachusetts State board of health and represented nearly all breeds of dairy cattle, particularly the Holstein, Ayrshire, Dutch Belted, and grade Holstein cows. The methods employed were the provisional (acetic acid) method, natural souring, calcium chlorid method, and asaprol method. details of the methods other than the provisional methods are as follows:

The

Natural souring method.-Allow the samples to sour spontaneously and filter off the

serum.

Calcium chlorid method.-Place 90 cc of milk in a flask, add 0.75 cc of calcium chlorid solution-sp. gr. 1.1375 (when diluted 1:10 this solution reads 26 on the immersion refractometer at 17.6° C.), shake thoroughly, close the flask with a cork carrying a glass tube to act as a reflux condenser, place in a boiling water bath for twenty minutes, cool to 20°, mix the condensed water and serum without shaking, and filter.

Asaprol method. The precipitating solution is made by dissolving 30 grams of asaprol and 55.8 grams of crystallized citric acid in 1 liter of water. If the refraction of this solution is not 36.3 on the scale of the immersion refractometer at 20°, add water or citric acid to make it so. Mix equal volumes of the above solution and the milk, shake well, and filter.

In the accompanying table are the results of the refraction of the milk serum prepared from milk samples of known purity when two or more methods were applied to the same sample of milk. The asaprol method is by far the easiest of manipulation. It gives the clearest serum in the least time and shows the lowest refraction with the least variation. Unfortunately pure asaprol is very difficult to obtain, and, owing to the fact that it decomposes readily, it is not an easy matter to prepare different solutions that will give identical sera with the same sample of milk. The calcium chlorid method is the most difficult of manipulation and is liable to give a cloudy serum rather troublesome to read, but the results are lower than those obtained by the acetic acid method and not so variable. The natural souring method is too slow for ordinary use, but is valuable in the hot weather if the milk is nearly sour when it reaches the analyst. Four years' experience with the provisional method has shown it to be reliable, easy of manipulation, and to give concordant results.

a Matthes and Müller, Zts. öffentl. Chem., 1903, 10: 173.
Ackerman, Zts. Untersuch. Nahr. Genussm., 1907, 13: 186.

c Baier and Neumann, Zts. Untersuch. Nahr. Genussm., 1907, 13: 369.