"Ultrasound treatment of preformed nanofibrillated whey protein Isolate: Effects on structure, enzymatic hydrolysis, and bioactivity"

Nanofibrillar protein structures have attracted considerable interest in food science due to their high aspect ratio, which confers unique mechanical and functional properties, enhancing the textural and structural characteristics of food systems. Ultrasonication, as a non-thermal processing technology, has emerged as a promising method in food modification. This study investigated the effects of high-intensity ultrasound treatment (200 W cm⁻²) applied for 10, 20, and 30 minutes following nanofibril formation on the structural integrity, digestibility, and antioxidant activity of whey protein isolate (WPI) nanofibrils. Sonication for 30 minutes caused significant fragmentation and disruption of the heat-induced fibrils, accompanied by an increase in β-sheet content. Increasing sonication duration from 10 to 30 minutes resulted in progressively higher visual brightness, indicating enhanced transparency and reduced turbidity of nanofibrillar dispersions. Moreover, extended sonication significantly improved pepsin- and trypsin-mediated hydrolysis of the nanofibril substrates, with the most pronounced effects observed at 135 and 180 minutes of hydrolysis for pepsin and trypsin, respectively. DPPH radical scavenging activity was significantly enhanced by ultrasound treatment. The optimal condition involved 30 minutes of ultrasonication combined with a minimum of 135 minutes of enzymatic hydrolysis, irrespective of the enzyme employed, leading to a substantial increase in antioxidant activity. Furthermore, the combination of 30 minutes sonication and at least 180 minutes of hydrolysis at constant enzyme concentration significantly enhanced the ferric reducing antioxidant power of WPI nanofibril hydrolysates. These findings demonstrate that ultrasound treatment holds potential for improving the nutritional and functional properties of protein-based food systems.