Abstract
Plasma is a new technology used to modify myofibrillar proteins (MPs) structure and promote protein aggregation. In order to study the mechanism of plasma modifying MPs thus the effects on qualities of MP gels, MPs were extracted by 0.6 M NaCl solution prepared with plasma-activated water (PAW) at different treatment time (0 s, 30 s, 60 s, 120 s, 240 s). With the prolonged PAW treatment time from 0 to 240 s, the pH values of natural MP solutions decreased significantly from 5.91 to 2.61 (P < 0.05), the H2O2 concentration in PAW increased from 0 to 70.82 μg/L (P < 0.05), and the net negative charges of MPs first decreased and then increased (P < 0.05). In addition, PAW caused significantly (P < 0.05) weakened ionic bonds and enhanced hydrophobic interactions, which promoted the aggregation and gelation of MPs thus forming MP gel with higher gel strength and a denser three-dimensional network. Furthermore, Raman spectra and intrinsic fluorescence suggested that PAW promoted the unfolding of MP structures and transformation from α-helixes and random coils to β-sheets and β-turns. Dynamic rheology indicated a gradually increased storage modulus and shortened degradation time of MPs with an increasing treatment time of PAW. Furthermore, PAW modification significantly improved the water holding capacity of MPs gels. These results demonstrated that the declined pH of MP solutions induced by PAW and increased H2O2 in PAW altered the ζ-potential of MP solutions and promoted the unfolding and aggregation of MPs during heating via hydrophobic interactions, ultimately enhancing gelling properties of MPs. The present work suggested the potential use of PAW in preparing freshwater MP gels with high quality.