Biotransformation of fish waste into a stable feed ingredient

Chopped pilchard wastes, including viscera, heads and tails, were mixed with 25% molasses and inoculated with a starter culture composed of Saccharomyces sp. and Lactobacillus plantarum. The silage was incubated at 22°C. Changes in nutritional quality and biochemical properties (pH, dry matter, ash, total and volatile nitrogen, lipids and trimethylamine) were monitored during a fermentation period of 15 days. Microbiological determinations were also carried out, including standard plate count, coliforms, Clostridium, lipolytic and proteolytic microorganisms. Results indicated that the pH decreased considerably and remained constant at 4.2 and 4.5 in the two trials. The total nitrogen decreased while the non-protein nitrogen and total volatile nitrogen increased significantly. Almost the same pattern in the two trials was observed. The trimethylamine decreased or remained constant at low levels depending on the initial value. The microbiological characteristics showed a rapid decrease of coliform and Clostridium counts to reach a low level after 5–7 days. Lipolytic and proteolytic microoganisms decreased notably during the fermentation and reached a minimum after 8 days and 5 days, respectively, in the two trials.