BIOLOGICAL QUALITY OF FERMENTED FISH OFFAL AND CHICKEN BY-PRODUCTS

The biological quality of fermented animal by-products prepared from fish and chicken offal was evaluated. A quality index (QI) based on analyses of a few important free amino acids and their corresponding biogenic amines was given. A group separation method based on ion exchange chromatography was found suitable for isolating and purifying amines and amino acids in biological samples. Quality was evaluated in samples fermented with different starter cultures, inoculation sizes and substrate levels. Slow or incomplete fermentation led to the accumulation of biogenic amines, especially tyramine, and resulted in a low QI. Fast initial and continuous stable fermentation for four weeks resulted in low concentrations of biogenic amines and high concentrations of free amino acids and consequently a high QI. The alanine concentration was considered to be a useful tool for estimating proteolysis, and QI related to changes in alanine concentration, lactic acid production and redox potential were considered to give the most useful estimation of the biological quality of fermented fish offal and poultry waste.