Mechanism of ultrasonic treatment affecting the conformation and properties of oat-whey dual-protein gel

Abstract

Plant and animal proteins can provide beneficial synergistic effects in compensating for their structural and nutritional inadequacies. In this study, oat protein (OP) was combined with whey protein (WP) and were subjected to ultrasonic treatment to produce a dual-protein gel. This investigation systematically analysed the changes in protein aggregation state, conformation, and properties of OP-WP gels with varying protein ratios (OP, 7:3, 5:5, 3:7 and WP) and ultrasonic power treatments (power 0, 200, 400 and 600 W), and explored the underlying formation mechanism. It was revealed that both increased whey protein content and moderate ultrasonic power significantly reduced the particle size of protein aggregates. Meanwhile, this increased the conversion rate from α-helix to β-sheet and reduced the amount of random coil structures, and decreased the content of free sulfhydryl groups. At 400 W ultrasonic power, the dual-protein gel with an OP:WP ratio of 3:7 exhibited excellent textural properties, rheological behavior, gel strength (147.96 gf) and water-holding capacity (50.96 %). Disulfides and hydrophobic interactions were enhanced by a tight and uniform gel framework. Furthermore, excessive sonication (600 W) disrupted protein conformation by increasing α-helix to 12.90 % and random coiling to 12.99 %, causing a decline in fluorescence intensity and weakening of structural stability of OP-WP gel. This research offers new insights and technical references for the adoption of ultrasonic processing in dual-protein gel systems and the exploitation of novel high-protein food.