Recovery of digestive enzymes from Atlantic cod (Gadus morhua) and their utilization in food processing

Han, Xiao-Qing (1993) Recovery of digestive enzymes from Atlantic cod (Gadus morhua) and their utilization in food processing. Masters thesis, Memorial University of Newfoundland.

[English] PDF (Migrated (PDF/A Conversion) from original format: (application/pdf)) - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. Download (17MB) [English] PDF - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. (Original Version)

Abstract

An extraction process for the recovery of proteolytic enzymes from the digestive tract of cod (Gadus morha) is described. Processing variables were optimized by employing a rotatable experimental design with computer graphics-assisted response surface methodology (RSM). A simple extraction procedure was developed which effectively isolated both acid and alkaline proteases from cod viscera with recovery yields of 52% and 30%, respectively. Further purification and characterization revealed that the crude acid proteases consisted of three types of gastric enzymes designated as acid proteases A, B, and C. Acid protease B was classified as fish pepsin II. Acid proteases A and C possessed properties similar to chymosin and gastricsin, respectively. The partially purified alkaline proteases possessed properties of trypsin-like enzymes and acted on N-benzoyl-L-tyrosine ethyl ester (BTEE), a synthetic substrate for chymotrypsin. -- Utilization of the crude isolated proteases was tested in milk-clotting for cheese making, as well as preparation of protein hydrolysates from under-utilized fish species. Cod pepsin was capable of clotting milk efficiently at low temperatures, which shows its potential use in cold renneting of milk. Capelin protein hydrolysate with a recovery yield of 55.8% was obtained when crude cod gastric proteases were used over a 4 h hydrolysis period at ambient temperatures.

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