Autolysis and rancidity development in tropical freshwater fish viscera during fermentation

To develop an ensiling process to preserve the nutrients in fish viscera, the offal was homogenised with 10% (w/w) molasses. Propionic acid (0.5% v/w) was added as an antimycotic agent. NaCl (2% w/w) and ethoxyquin (0.02% w/w) were added to see the effect on autolytic changes and rancidity development, respectively. Fermentation was carried out under microaerophilic condition at 26 ± 2°C. Total volatile nitrogen, non-protein nitrogen, alpha-amino nitrogen (autolytic changes) and free fatty-acid content increased (P < 0.001) rapidly during the first 4 days and then remained constant up to 8 days. Salt had no influence on autolysis. Peroxide value (PV) increased (P < 0.001) initially up to 3–4 days and then decreased. A rapid increase (P < 0.001) up to 2 days and small (P > 0.05) subsequent increase in iodine value (IV) were observed. Thiobarbituric acid (TBA) number increased linearly up to 8 days of fermentation period. Ethoxyquin was effective in controlling oxidative rancidity, as indicated by significantly (P < 0.001) lower PVs and TBA numbers and higher IVs.