Optimization of protein hydrolysate from visceral waste of nile tilapia (Oreochromis niloticus) by response surface methodology

The present study was targeted to determine the best hydrolysis conditions to produce visceral protein hydrolysates from Nile tilapia (Oreochromis niloticus) using alcalase enzymes. Box-Behnken design for response surface methodology was used to optimize the hydrolysis conditions (time, pH and temperature) for preparing protein hydrolysates from Nile tilapia visceral waste. The results showed that the temperature and time are the main factors that influence the degree of hydrolysis. The relationship between the variables and the degree of hydrolysis is characterized by the following equation: Y=41.46– 0.6150A+0.5350B+0.1975C-1.21AB–0.6750AC–0.8500BC–4.64A²–3.87B²–3.39C², where A, B and C are pH, temperature and time, respectively. The optimized hydrolysis should be carried out at a pH of 7.9, a temperature of 55.8⁰C and with an alcalase enzyme concentration of 1.5% for 1.5 h. At these optimal conditions, alcalase hydrolysis resulted in a desirability value of 0.854, with 41.46% degree of hydrolysis. The amino acid (AA) with the highest value in Nile tilapia viscera hydrolysates is glutamate (5.32 g/100 g), while the AA with the lowest level is glutamine (0.32 g/100 g). The AA analysis indicates that the AA profiles of the Nile tilapia viscera hydrolysates were generally high in essential AAs. The optimal hydrolysis condition can be a good reference for enhancing the potential of visceral protein hydrolysates in future functional food development.