Optimization of conditions for natural fermentation of freshwater fish processing waste using sugarcane molasses

Conditions like, substrate level and incubation time at elevated temperature (37+l°C) for fermentation of fish
waste by in situ lactic acid bacteria (LAB) using sugarcane molasses as source of sugar to obtain the desirable pH
(<3.8) were optimized by response surface methodology. The visceral wastes resulting from processing of freshwater
carps (Catla catla, Labeo rohita and Cyprinus carpio) were used for the study and had an initial pH of 5.8 and LAB
count of 4.6 log cfu/g. Sugarcane molasses at 7.5% (w/w) as a source of sugar and fermentation for 48 h at 37±1°C
were found optimum to get the desired pH reduction. The usefulness of the model was further validated using different
random combinations of 2 independent variables. During storage for 14 days, fish waste fermented under optimized
conditions showed an increase in LAB count from the initial 4.6 to 8.3 log cfu/g. However, enterobacteria and
staphylococci were not detected during storage. The pH and total titrable acidity of the fermented silage stabilized
around 3.8 and 1.8, respectively. The lactic fermentation stabilized fish waste has the potential for use as an ingredient
in aquaculture/animal feeds.