A biotechnological process for the valorization of fish waste

Abstract

Thirty-two strains of yeasts ( Saccharomyces cerevisiae and Candida sp.) and 14 strains of lactic acid bacteria ( Lactobacillus plantarum and Pediococcus acidilactici) were screened on fish waste supplemented with molasses to select suitable combinations for fish silage fermentation. The parameters studied were molasses concentration, pH and temperature. Microbiological counts including standard plate count, coliforms, enterococci, staphylococci, Salmonella, Clostridium, lipolytics, proteolytics, yeasts and moulds were made. In parallel, physico-chemical analyses, including pH, dry matter, ash, total nitrogen (TN), total non-protein-nitrogen (NPN), total volatile nitrogen (TVN), lipids, reducing sugars and trimethylamine (TMA) were also carried out on the material before the fermentation and on the product. Results indicated that the most suitable conditions for the fermentation were 30% of molasses at pH 5·2 and at 26–28°C. The product was free of coliforms and Salmonella. The chemical determinations showed a net decrease of the pH, low TMA content and low total volatile nitrogen, but a net increase in reducing sugars in the product. Non-protein-nitrogen was high in the product relative to the raw material.