Making Fish Protein Concentrate by Enzymatic Hydrolysis 



A status report on research and some processes and 

 products studied by NMFS 



By 



MALCOLM B. HALE 



National Marine Fisheries Service 



Fishery Products Technology Laboratory 



Regents and Campus Drive 



College Park, Maryland 20740 



ABSTRACT 



Research into biological methods for fish protein concentrate (FPC) preparation which 

 has been carried out within the National Marine Fisheries Service is summarized. The effects 

 of various processing conditions and commercially available proteolytic enzymes on yields and 

 characteristics of water-soluble fish protein hydrolysates are presented. Soluble FPC pre- 

 pared from red hake (Urophyeis chuss) tended to be deficient in either tryptophan or histidine, 

 depending on the pH of hydrolysis. Hydrolysis of raw fish with an alkaline protease of Bacillus 

 subtilis at pH 8.5 or above gave the best balance of essential amino acids and a high yield of 

 soluble product. Pancreatin also gave very good results at pH 8.5. The protein efficiency 

 ratio (PER) of a totally soluble FPC prepared from alewife (Alosa pseudoharengus) was equiv- 

 alent to that of casein. Soluble products prepared from hake were equivalent to casein as a 

 wheat supplement but not as a sole source of protein. Process outlines and preliminary cost 

 estimates are presented for the production of two types of fish protein hydrolysates. Possible 

 food uses and the flavor problem are discussed. This report includes a literature survey of fish 

 protein modifications by fermentation and selected chemical hydrolysis methods as well as by 

 enzymatic hydrolysis processes. 



INTRODUCTION 



Fish Protein Concentrates 



Fish protein concentrates (FPC) are products 

 derived from fish by processes in which the fish 

 protein is placed in a more highly concentrated 

 and stable form. As a form of animal protein 

 FPC can supplement vegetable proteins very ef- 

 fectively. Added in low concentrations they can 

 markedly improve the nutritive value of bread 

 and many other common foods by supplying cer- 

 tain essential amino acids in which vegetable 

 proteins are deficient. As a stable powder (or 

 paste) produced from species of fish not normally 

 used as food, they are the least expensive source 

 of animal protein. 



FPC may be produced by various processes to 

 give products with different costs and proper- 

 ties, thus different application. Most processing 

 methods can be classified as chemical (solvent 

 extraction) or biological (enzymatic and micro- 

 bial) procedures. During recent years most ef- 

 forts have involved the use of solvents, usually 

 isopropyl alcohol, and several pilot plants and a 

 few full-scale industrial plants have been con- 

 structed. By solvent extraction FPC can be pro- 

 duced that is a bland, nearly odorless, lightly 

 colored, water-insoluble but highly nutritive 

 powder. FPC prepared by biological procedures 

 are usually more flavorful and may have desir- 

 able functional properties. In general the bio- 

 logical procedures have not advanced beyond the 

 laboratory or small pilot plant stage. 



