A method was developed for the extraction of rennet from fresh frozen vells. Frozen vells were partially thawed and minced in a Hobart "Wonder worker." The tissue was treated with 2.0 per cent potassium alum and allowed to stand for 20 hours before sufficient 0.45 M disodium phosphate was added to bring the pH of the mixture to 5.7. Dry sodium chloride was added until the salt concentration in the moisture of the mixture was 10 per cent. The tissue was then mixed with 3/4-inch pumice gravel in a volume ratio of 1 to 2 and packed into extractor columns. The tissue was extracted continuously with a 10 per cent sodium chloride solution. The yield of enzyme and extract viscosity from 60 undried vells was compared with that from 60 dried vells. The undried vells yielded 2. 99 x 106 R.U. in 86 liters of extract and the dried vells yielded 3.03 x 106 R.U. in 74 liters of extract. The viscosities of the initial extracts were 5.8 and 6.2 centipoise respectively. Drying temperature, moisture content and pH had no effect on extract viscosity . Viscosities of extracts were viii reduced by aging the dried vells prior to extraction, adjusting sodium chloride to 10 per cent in extracting solutions, and adding 2 to 3 per cent potassium alum to undried vell tissue and holding for 20 hours before neutralizing to pH 5.7 %plusmn; 0.2 with disodium phosphate. The mean activity value of extracts representing 96,000 vells was 45.5 R.U. with a standard deviation of ± 19.57 for individual vells. This variation in enzyme content precluded useful comparisons of yield based on small numbers of individual whole vells.

A procedure was developed for the extraction of rennet from fresh frozen vells. Frozen vells were minced in a Model VCM-25 Hobart Vertical Cutter/Mixer. Dry sodium chloride was added until the salt concentration in the moisture of the tissue was 10%. Salted tissue was placed in galvanized steel cells and heated in a water bath to 49, 54, 57 and 60 C for 0, 15, 30, 45 and 60 minutes. The heated tissue was dried to about 4% moisture at ambient temperature with the aid of an electric fan. The dried salted tissue was extracted with a sodium chloride solution adjusted to give a salt concentration of 10% in the extraction solution. Salted vell tissue heated to 49 C for 60 minutes and to 54 C for 30 minutes prior to drying produced 82 and 55%, respectively, more recoverable enzyme activity than unheated salted tissue. However, tissue which was salted, heated and not dried prior to extraction produced less recoverable activity than unheated samples. Unsalted vell tissue which was heated to 49, 54, 57 and 60 C for 15, 30, 45 and 60 minutes and extracted without being dried yielded lower recoverable activity than unheated samples. Heating unsalted vell tissue to 54, 57 and 60 C for 15, 30, 45 and 60 minutes prior to drying did not increase recoverable enzyme activity over unheated samples. Unsalted tissue heated to 49 C produced a slightly higher recovery than unheated samples.