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The origin and mechanism of formation of the volatile fatty acids (VFA) present in budu were investigated. The acids did not appear t o derive from the breakdown of the fish lipid. When the fish was allowed to spoil, a single bacterial species predominated, and as the fermentation progressed, the appropriate VFA were formed.Using (U-lJC)-protein hydrolysate it was shown that amino acids are the precursors of the n-butanoic and 17-pentanoic acid and also contributed to the formation of other acids. The bacterium did not use glucose as a carbon source nor did any particular combination of unlabelled amino acids produce the fatty acids. The metabolic route by which the fatty acids are produced from the amino acids is not known. An experiment that allowed spoilage to occur, prior to salting, in the normal environment involved in the preparation of budu, showed that the VFA were produced.

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The changes that occur during the commercial production of budu, a Malaysian fish sauce were examined. It was shown that the maximum volume of liquid was produced after 140 days and that proteolysis continued to occur until 200 days when 56 % of the insoluble fish protein had been hydrolysed into soluble form. The colour was produced early during the fermentation. The aroma constituents, ammonia and trimethylamine, were produced early in the fermentation process, but the volatile fatty acids did not appear when fresh fish (Stolephorus) was used for the fermentation. In the commercial production, n-butanoic acid concentration remained constant during the fermentation but ethanoic acid did increase during the period. The salt concentration and the pH were approximately constant throughout, at 26 % and 5.65, respectively.

SynopsisA study of the immobilization of trypsin and other enzymes onto hydrolyzed poly(2-hydroxyethyl methacrylate)-g-co-polyethylene using hydroxyl and carboxyl activating agents has been undertaken. Some emphasis was placed on the immobilized trypsin system which involved examination of the variation of (i) the extent of hydrolysis of the graft copolymer, (ii) the concentration of activating agent, and (iii) the temperature of coupling. With the trypsin system, an increase in carbodi-imide concentration gave an increase in the amount of protein immobilized but a marked decrease in the retention of enzymic activity. Comparison of the behavior of the free with the immobilized enzyme showed that satisfactory yields were obtained and the immobilized system has an extended pH profile and good stability and thus would have broad applicability. The kinetic factors were examined further, and the role of the graft copolymer chains in the immobilized system is discussed.