Combined frequency ultrasound and controlled germination to improve protein composition, conformation, interactions,...

To improve the composition and structure of wheat protein, the varieties in the composition, conformation and interactions of proteins in germinated wheat flour treated with single-frequency (60 kHz, SFWF), dual-frequency (20 + 60 kHz, DFWF), and triple-frequency (20 + 40 + 60 kHz, TFWF) ultrasound in five days were investigated, as well as their mechanisms. The results showed DFWF produced the lower ratio of gliadins to glutenin and higher gliadins with glutenin (germination, 48 h) and TFWF had highest gliadins at 72 h. The obvious decline of fluorescence intensities at 72 h of germination time in DFWF and TFWF revealed that combined frequency ultrasound could significantly influence the protein conformation by regulating the posttranslational modification. Moreover, dual-frequency and triple-frequency ultrasound treatment could generate superior ionic, hydrogen bonds and hydrophobic interactions at 24 h and 72 h, respectively. Besides, SDS-PAGE confirmed the changes in the subunits of protein of DFWF and TFWF at 72 h and 120 h, and the starch granules of DFWF had the densest starch protein matrix complex at 24 h. These findings demonstrated that treatment with combined frequency ultrasound could be a potential and valid method to improve the quality and properties of germinated wheat flour.