SILAGE FROM FISH WASTE - CHEMICAL AND MICROBIOLOGICAL ASPECTS

Fresh fish waste was manufactured into fish silage using formic acid t o reduce pH to 3.5. The pH remained below 4.0 for up to 30 days. The c hemical composition (g/kg) of silage varied with the type of raw mater ial; moisture 726 to 803 (mean 764); oil 3 to 71 (mean 38); ash 35 to 72 (mean 51); protein 144 to 161 (mean 147). During the first 8 days a fter silage manufacture, concentrations of the low-salt-soluble and in soluble protein fractions decreased while the non-protein nitrogen con tent increased. Silage viscosity continued to decrease with time up to day 15. The ensiling process caused a sharp initial decrease in the t otal number of bacteria, in lactic acid bacteria and in coliform speci es followed by a more gradual decrease up to 48 h. A comparative study of silage manufactured from flat-fish frames (A) and round-fish heads (B) at pH 3.5 or 4.5, showed chemical composition (g/kg) of 726 and 7 77 moisture; 70 and 3 oil; 55 and 70 ash; 149 and 150 protein for A an d B, respectively. Silage viscosity showed greater decreases at pH 3.5 than at pH 4.5. Silage manufactured from round-fish heads showed grea ter viscosity decreases at both pH levels.