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MILK CLOTTING AND CHEESE MAKING PROPERTIES OF A CHYMOSIN‐LIKE ENZYME FROM HARP SEAL MUCOSA
Author(s) -
SHAMSUZZAMAN KAZI,
HAARD NORMAN F.
Publication year - 1985
Publication title -
journal of food biochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.507
H-Index - 47
eISSN - 1745-4514
pISSN - 0145-8884
DOI - 10.1111/j.1745-4514.1985.tb00348.x
Subject(s) - chymosin , pepsin , rennet , chemistry , food science , autolysis (biology) , casein , chromatography , biochemistry , enzyme
Pepsin A was isolated from the gastric mucosa of two year old harp seal ( Pagophilus groenlandicus ). Seal pepsin A has a relatively high CU/PU ratio of 0.074, although it is lower than that of calf chymosin (0.170). Equivalent milk clotting units of chymosin and seal pepsin A catalyzed formation of the same amount of nonprotein nitrogen (NPN) when incubated with 2% casein and for both there was no appreciable increase in NPN formation in the second hour of incubation. Seal pepsin A was similar to chymosin in clotting milk substrate with respect to the influence of pH, dilution, calcium chloride and temperature.Cheddar cheeses prepared with either calf rennet or pepsin A as coagulating agent were similar in yield, chemical composition and taste as judged by sensory preference tests. Estimation of protein degradation in the aged cheeses by ultraviolet absorption of citrate‐HC1 extracts, gel filtration chromatography of protein soluble in 6 N urea, and determination of amino acids indicated there was slightly more protein degradation in cheese prepared with calf rennet after 30 weeks aging.Sal pepsin A appears to make a major contribution to the excellent cheese‐making characteristic of crude seal pepsin(s). However, other components of the seal mucosa extract are probably responsible for the accelerated aging of Cheddar cheese noted in previous reports.