Fibrillation of whey protein isolate by radio frequency heating for process efficiency: Assembly behavior, structural characteristics, and in-vitro digestion

In this study, a novel technology involving radio frequency heating (RF) was applied to promote the production of whey protein isolate (WPI) nanofibrils. As the prolonged treatment time, gradual increases were observed in the conversion rate (>16 h with the conventional processes), fluorescence intensity, and free amino acid content of WPI. During the fibrillation process, WPI was hydrolyzed into small molecular weight peptides that self-assembled into fibrils, resulting in a significant increase in the ζ-potential and surface hydrophobicity. Conformational and structural changes that favored an increased content of β-sheets were confirmed by Fourier transform infrared and circular dichroism spectroscopy. A linear fibril structure with a proper aspect ratio (length/diameter, 35.50 ± 0.39) formed at 7 h. Moreover, the good resistance to proteolytic digestion (especially gastric stage) of certain fibrils makes them suitable for application as nutraceutical delivery vehicles. Our findings move a step forward for WPI fibrillation by RF heating.