bacterial counts decrease steadily during a 12- 

 month fermentation, and after 9 months approx- 

 imately 70% of the bacterial isolates were 

 halophiles of bacillus types. These bacteria 

 produced volatile acids in a medium containing 

 acid-hydrolysed rockfish. A diethyl-ether-etha- 

 nol extract of the fermented hydrolysate con- 

 tained the typical aroma of fish sauce. 



A proteolytic yeast has been isolated by 

 Bertullo in Uruguay and used in fish fermenta- 

 tions. Characteristics of the yeast and some 

 details of its use are contained in a patent 

 (Bertullo and Hettich, 1961) . A stable fish hy- 

 drolysate with a pleasant aroma is formed by 

 the growing yeast culture which produces pro- 

 teases, acids, and alcohol. The process has been 

 improved since publication of the 1961 patent. 

 Less sugar is added and the fermentation reach- 

 es the final pH of about 4.3 in 18 to 24 hr. Most 

 of the fat is removed by centrifugation and the 

 dried product is 70% water-soluble. Fermenta- 

 tion of a mixture of 50% fish, 30% soya, and 

 20% alfalfa has yielded a product with a PER 

 exceeding that of the casein control. 



Burkholder et al (1968) have studied fish 

 fermentation with pure cultures of microorgan- 

 isms selected more for their lipolytic activity 

 than for proteolytic activity. Menhaden was 

 fermented with hundreds of different cultures 

 of bacteria, yeast, and molds obtained from var- 

 ious sources. Organoleptic screening of the 

 fermentation products yielded seven yeasts and 

 one mold for further study. It was found that 

 the mold and three of the yeasts could utilize 

 menhaden tryglycerides as a carbon source. Two 

 of the microorganisms, through utilization of 

 nonprotein nitrogen and triglycerides, were able 

 to reduce the fat content and increase the protein 

 content of a menhaden ferment substantially 

 while producing neutral to pleasant flavors and 

 aromas. 



A number of different types of microorgan- 

 isms have been used to preserve fish and neu- 

 tralize fish odor and flavor. The use of Aero- 

 bacter aerogenes, Streptococcus lactis, and other 

 carbohydrate fermenting microorganisms with 

 fish to which sugar or molasses has been added 

 is the subject of a Japanese patent (Tada and 

 Nakayama, 1956). The keeping quality of the 

 fish is greatly improved by fermentation. 



Krishnaswamy, Kadol, and Revankar (1965) 

 fermented a freshwater fish with a pure culture 



of Streptococcus lactis using lactose as the car- 

 bon source. The dried product was cream col- 

 ored with a protein content of about 72 % . Levels 

 of total and available lysine, tryptophan, and 

 sulfur-containing amino acids were very good. 

 The biological value of the product as determined 

 by PER, NPU (net protein utilization), and net 

 protein ratio was not significantly different from 

 that of skim-milk powder. 



Summary of NMFS Work (Generalized) 



In-house. — In-house research within the 

 NMFS has been oriented toward development 

 of a totally water-soluble FPC through the use 

 of enzymatic hydrolysis (Fig. 1). The basic 

 process outline includes enzymatic digestion of 

 a whole fish slurry with control of pH and tem- 

 perature, screening out of bones and scales, and 

 separation of undigested solids by centrifuga- 

 tion. The clarified hydrolysate is spray-dried 

 to yield a soluble product consisting of peptides, 

 polypeptides, and some free amino acids. 



Initial work at College Park included small- 

 scale tests in laboratory flasks with the enzymes 

 pepsin, trypsin, bromelin, ficin, and papain. 

 With the installation of a 30-gal fermentation 

 vessel (Fig. 2) complete with pH and temper- 

 ature recording and control, larger batches were 

 hydrolysed and soluble products were dried on 

 a small vacuum drum dryer. A light yellow 

 product with a pleasant cheeselike aroma and 

 taste was prepared by hydrolysis of red hake 

 ( Urophycis chuss) with Rhozyme P-11 at pH 8.5. 

 Digestion of presterilized hake yielded a whiter, 

 milder flavored product at the expense of sol- 

 uble product yield. 



Several large hydrolysate batches were pre- 

 pared for use in trials of equipment proposed for 

 use in a biological process model scale unit. Cen- 

 trifugation and spray-drying equipment were 

 tested at the plants of several manufacturers and 

 tests of other components of the model unit were 

 performed at the College Park laboratory. Con- 

 tractor for design of the system was Artisan 

 Industries of Waltham, Mass. 



Bertullo process. — For a 2-month period the 

 laboratory processing equipment was used in 

 cooperation with Dr. Victor Bertullo of the 

 University of Uruguay, Montevideo. He had 



