The use of bromelain in the hydrolysis of mackerel and the investigation of fermented fish aroma

Summary A fish hydrolysate was produced from homogenized mackerel using bromelain to increase the rate and extent of proteolysis. Measurement of the extent of hydrolysis and conversion of insoluble to soluble nitrogen compounds after 1, 2, 3, 5 and 14 days of incubation at 38°C showed that a hydrolysate having some of the characteristics of an oriental fish sauce could be formed from mackerel within this period with a net protein conversion rate of over 75%, but it was necessary to include a 24 hr incubation period prior to the addition of salt. The technique was used for the investigation of the causative agents of aroma production in the mackerel homogenate. Assuming that the proteolysis was still carried out by the protease, the mackerel homogenate was subjected to heat treatment, or mixed with antibiotics, or TGA prior to addition of bromelain. These treatments caused the loss of some of the constituents (associated with oriental fish sauce aroma) which suggests that with mackerel, micro-organisms play a significant role in aroma development. The method could be used for the investigation of sauces prepared from oriental fish; as the causative agents of aroma production might well be different. The bacteria, involved with mackerel could easily produce harmful products which were not investigated.