eng Enviro Research Publishers Current Research in Nutrition and Food Science Journal 2347-467X 2322-0007 2026-07-13 14 2 26552 article Minh Van Nguyen 1 Musiige Denis 1 Derrick Kakooza 1 Hung Duc Pham 2 Faculty of Food Technology, School of Fisheries and Life Sciences, Nha Trang University, Khanh Hoa Province, Vietnam Faculty of Aquaculture, School of Fisheries and Life Sciences, Nha Trang University, Khanh Hoa Province, Vietnam Enzymatic hydrolysis is an effective approach for valorizing fish processing by-products into functional protein ingredients. In the present study, yellowfin tuna (Thunnus albacares) viscera were hydrolysed using Alcalase, and the hydrolysis process was optimised through response surface methodology (RSM). The influences of reaction time (2-12 h), temperature (47-64 °C), and enzyme concentration (0.3-1.2%, v/w) on degree of hydrolysis (DH) and protein solubility were investigated using a central composite design. Statistical analysis indicated that all three processing variables significantly affected the responses (p<0.05), although reaction time and enzyme concentration contributed more strongly than temperature. The developed quadratic models adequately described the experimental data, yielding coefficients of determination of R² = 0.97 and R² = 0.95 for DH and solubility, respectively. The optimum hydrolysis conditions for achieving maximum DH (66%) and solubility (28%) were 6.7 h, 53.4 °C, and 0.88% Alcalase. These findings demonstrate that yellowfin tuna viscera can be efficiently converted into protein hydrolysates and provide a basis for their further evaluation as alternative protein ingredients for animal feed applications. https://www.foodandnutritionjournal.org/volume14number2/optimization-of-alcalase-hydrolysis-to-enhance-degree-of-hydrolysis-and-protein-solubility-in-yellowfin-tuna-thunnus-albacares-viscera/ Alcalase Enzymatic hydrolysis Fish protein hydrolysate Response surface methodology Yellowfin tuna viscera