Effect of pulsed ultrasound pretreatment on enzymatic hydrolysis and bio-functional properties of luffa cylindrica seed protein hydrolysates

Pulsed ultrasound pretreatment was investigated as a strategy to enhance the enzymatic hydrolysis and bio–functional properties of Luffa cylindrica seed protein concentrate. The influence of ultrasound power (100–200 W) and treatment time (5–25 min) on the degree of hydrolysis (DH), structural characteristics, functional properties, and antioxidant activity of Alcalase–generated hydrolysates was evaluated. Ultrasound pretreatment resulted in higher DH values compared with conventional enzymatic hydrolysis (8.13% after 4 h). Ultrasound–assisted treatments followed by only 2 h of hydrolysis produced DH values of 9.6–35.3%, with the maximum obtained at 200 W for 25 min, suggesting that ultrasonic pretreatment may accelerate proteolysis while reducing processing time. SDS–PAGE indicated progressive degradation of native proteins, including reduced intensity of high–molecular–weight bands (>45 kDa) and the appearance of peptides below 15 kDa. FTIR analysis suggested ultrasound–induced conformational changes that may facilitate enzyme accessibility. Moderate treatment (200 W, 5 min) was associated with the highest emulsifying activity (33.3 m 2 g −1 ) and foam capacity, whereas prolonged treatment (200 W, 25 min) corresponded with improved foam stability and antioxidant activity. Ultrasound treatment also resulted in more negative zeta potentials (up to − 20.6 mV), which may contribute to improved solubility and dispersion stability. Overall, pulsed ultrasound appears to be a promising approach for modifying the structural and functional properties of L. cylindrica protein hydrolysates for potential food applications.