Optimisation of ultrasound-assisted enzymatic extraction conditions of umami compounds from fish by-products using the combination of fractional factorial design and central composite design.

In this work, ultrasound-assisted enzymatic extraction (UAEE) conditions of umami compounds from Labeo rohita head (LRH) was optimised using the combination of fractional factorial design (FFD) and central composite design (CCD). Six factors that can potentially influence the degree of hydrolysis (DH), equivalent umami concentration (EUC), and extraction yield (EY) of umami extract were screened through FFD. The three most significant variables were further optimised using the CCD. The developed models were successfully fitted to the experimental data and used to determine optimal extraction conditions. The optimum DH (22.73%), EUC (6.61 g MSG/100 g protein), and EY (76.34%) of umami extract were achieved with a liquid-solid ratio of 3 (v/w), ultrasonication time of 19.20 min and hydrolysis time of 140.45 min. Besides, UAEE umami extract exhibited higher DH, EUC, EY, and umami taste compared to that of the conventional enzymatic extraction (CEE).