Studies on Soft Curd Milk Prepared by the Enzyme Treatment Method

Abstract

This is a preliminary report on the investigation of the characteristics of enzyme-treated milk. 1

The enzyme treatment 1 is carried out by adding one part of pancreatic concentrate, which has a high tryptic value, to 10 to 15 thousand parts of cold raw whole cow milk and then pasteurizing the enzyme-milk mixture immediately in the usual manner. The milk proteins are altered by the pancreatic enzymes as the temperature of the milk rises during pasteurization.

Methods. Amino nitrogen was determined by the Van Slyke gasometric method. All other nitrogen determinations were made with the Kjeldahl method. The precipitin reaction was carried out according to the technic of Hektoen and Welker. 2 All control milk samples were prepared identically the same as the enzyme-treated milk samples and from the same milk without enzyme being added. The technic of the digestibility test which was found to be satisfactory is as follows:

Eight hundred ml of milk at 37°C is mixed with 80 ml of .5 N HCl containing .056% U.S.P. pepsin. The resulting pH is 4.8. Fifty ml portions are removed and filtered after 5 and 30 minutes'digestion at 37°C with mild agitation. The filtrates are set aside for total N analysis. The digest is then neutralized to pH 7.5 with NaOH and .112 g of U.S.P. trypsin is added. After 15 minutes of mild agitation at 37°C a third 50 ml portion is removed and adjusted to isoelectric pH 4.8 with HCl and then filtered to get the non-coagulable isoelectric protein filtrate. This is repeated every 20 minutes thereafter until a total digestion time of about 2 1/2 hours has elapsed. During the digestion, a pH level of 7.5 is maintained by the addition of NaOH. This test was used to study the digestibility of enzyme-treated milk.

Results. It was found that the enzyme-milk filtrates contained an average of 18.1% more protein than the control milk filtrates in 6 trials.

Table I shows the results of a typical digestibility test.

Enzyme-treated milk samples and their controls were made up to a 70% alcohol content, permitted to stand at room temperature over night and filtered. Total nitrogen was then determined on the filtrates to obtain the amount of alcohol-soluble protein in the milk. Table II shows that the enzyme treatment increases the amount of alcohol-soluble protein in whole milk.