Chemical and microbial changes in fish viscera during fermentation ensiling at different temperatures

Abstract

Fermentation ensiling of fresh water fish viscera with 10% (w/w) molasses, 0.5% (v/w) propionic acid and 0.02% (w/w) ethoxyquin at 26 ± 2°C and 37°C was investigated. The pH values and reducing sugar contents were significantly ( P ≤ 0.001) lower, and lactic acid contents higher ( P ≤ 0.001), in mixtures fermented at 37°C than those fermented at 26°C. Coliforms, Escherichia coli, enterococci, staphylococci and salmonella were absent from 48 h or 72 h onwards in fermentation at 37 and 26°C. Clostridium perfringens was absent after 48 h, and spores after 72 h, of fermentation at both temperatures. Markedly lower ( P ≤ 0.001) bacterial total viable count and marginally lower ( P ≥ 0.05) yeast and mould counts were noted in samples held at 37°C. Lactic acid bacterial counts were higher initially (up to 48 h) at 37°C than at 26°C. The ensiling was thus faster at 37°C than at 26°C.