Biochemical changes associated with fast fermentation of squid processing by-products for low salt fish sauce

In order to enhance the economical values of squid processing by-products and reduce the environmental problems caused by the wastes from squid processing, the possibility of utilizing squid processing by-products for low salt fish sauce production was investigated. Low salt fish sauce was prepared experimentally from squid processing by-products, according to three different manufacturing techniques (A, B and C) with or without the autolysis process and the addition of flavourzyme, soybean koji. Fish sauce products with similar quality were obtained at 48 °C after 30 days fermentation. The content of total soluble nitrogen in three fish sauce A, B and C were 2.135 ± 0.038%, 1.958 ± 0.041% and 2.038 ± 0.043%, respectively. The content of formaldehyde nitrogen in three fish sauce A, B and C were 1.028 ± 0.038 g/100 ml, 1.000 ± 0.046 g/100 ml, 1.127 ± 0.043 g/100 ml, respectively. The salt content in three fish sauce A, B and C were 8.842 ± 0.138%, 9.058 ± 0.142%, 8.764 ± 0.129%, respectively. At the same time, changes in total soluble nitrogen, conversion of nitrogen, pH, formaldehyde nitrogen, total titration acid, total volatile base nitrogen, salt concentration, protease activity, total plate counts of fish sauce were observed during fermentation. The results suggested that total soluble nitrogen, conversion of nitrogen, formaldehyde nitrogen, total volatile base nitrogen and salt concentration increased throughout the fermentation period. However, pH, total titration acid, protease activity and total plate counts showed different changes in different fermentation stage. The result of amino acids analysis suggested that glutamic acid was the most prominent in three fish sauce samples. The results from quantitative descriptive analysis test showed that all fish sauce samples were tasted and no particularly strong or unpleasant flavor.