Definition of Biological Procedures 



The work described in this publication has 

 been called the "Biological Method" within the 

 FPC program of the National Marine Fisheries 

 Service (NMFS). It involved the use of en- 

 zymes (biological catalysts) to convert fish pro- 

 tein into a stable concentrate with desirable pro- 

 perties. The enzymes partially break down the 

 proteins in the fish tissue making them more 

 or less soluble and releasing much of the fat 

 (lipid) so that it can be separated. The enzyme 

 systems employed may be the natural enzymes 

 contained in the fish (autolysis), purified com- 

 mercial enzyme preparations from various bio- 

 logical sources (e.g., plants, animal organs, or 

 microbial cultures) , or the enzymes may be sup- 

 plied by living cultures of microorganisms. 



Objectives of Program 



Development of a biological process is being 

 pursued because (1) the product can have spe- 

 cial properties, such as solubility, which make 

 it more suitable for certain applications than 

 solvent extracted FPC, (2) it may be possible 

 to produce an acceptable protein concentrate 

 more cheaply through biological means than 

 through solvent extraction, and (3) a biological 

 method with proper controls would be more suit- 

 able for use on shipboard or on a small scale in 

 remote areas. 



The primary objective of work carried out at 

 the National Center for Fish Protein Concen- 

 trate (NCFPC) has been to develop a process 

 for making a totally water-soluble product which 

 will offer distinct advantages for use in such 

 foods as soups and beverages. Although pro- 

 cessing costs have been considered throughout 

 the work, the major concern has been for im- 

 provement of the amino acid pattern and nu- 

 tritive value of the soluble product. 



STATE OF THE ART 



Literature Survey 



Most of the references described here are in- 

 cluded in a FPC bibliography' which was com- 



'■ Available from the U.S. Department of Commerce, 

 National Technical Information Center, Springfield, VA 

 22151. Price $3.00. 



piled for the National Center for FPC by the 

 Special Bibliographies Section of the Library of 

 Congress (Library of Congress, 1970). 



Enzymatic hydrolysis of fish. — Several pro- 

 cesses for the enzymatic hydrolysis of fish have 

 been reported in the technical and patent liter- 

 ature. Some of these processes are intended pri- 

 marily for animal feed products but could be 

 used to produce FPC for human consumption. 



A patent by Keyes and Meinke (1966) de- 

 scribes an enzymatic hydrolysis process in which 

 a proteolytic enzyme, an antibiotic and a chelat- 

 ing agent are added to a whole fish slurry. Pro- 

 cessing begins on board ship and the fish are 

 readily pumped to a land-based holding tank for 

 final processing to oil, meal, and solubles frac- 

 tions. 



Enzymes produced by the growth of molds 

 of the genus Aspergillus on wheat bran are used 

 to digest fish in a patent by Jeffreys and Krell 

 (1965). Either a water extract or the whole, 

 comminuted culture may be added and results 

 are claimed to be superior to those obtained with 

 purified commercial enzymes. A short-term di- 

 gestion may be carried out at 45° to 55°C after 

 which the liquefied fish is drum-dried. The use 

 of clean, eviscerated fish is recommended to ob- 

 tain a product for human consumption. If yeast 

 and a little sugar are added for fermentation 

 combined with hydrolysis at 34°C, it is claimed 

 that a product free of fish odor and taste is ob- 

 tained. 



Preservation and hydrolysis of fish using pep- 

 sin at pH 3 is described in a patent by Hasden- 

 teufel (1968). A product yield of 19.5% is 

 claimed. 



The preparation of fish hydrolysates by di- 

 gestion with papain has been reported by Sen 

 etal. (1962) and by Sripathy et al. (1962). They 

 developed conditions for the preparation of hy- 

 drolysates rich in peptones and proteoses for 

 possible use in bacterial culture media. A pro- 

 cess description with yield data for the hydrolysis 

 of fish with papain has been published by Sri- 

 pathy, Sen, and Lahiry (1964). 



FPC development efforts in France have been 

 concentrated on enzymatic hydrolysis methods. 

 Professor Ploquin and co-workers at the Uni- 

 versity of Nantes have developed a fish hydrol- 

 ysis process which uses papain and a relatively 



