Harnessing pea proteins for thermo-reversible gels: Novel strategy and molecular principle

Thermo-reversible gels (such as gelatin) have a wide range of applications in the food and pharmaceutical fields. This work reports a thermo-reversible gel prepared with pea protein isolate fractionated using ionic strength-shifting method (I_0.125: 0.5 → 0.125 M, I_0.08: 0.5 → 0.08 M, I_0.06: 0.5 → 0.06 M). The ionic strength-shifting fractioned pea protein isolate (ISS-PPI) can form thermo-reversible gels within a window of pH 4 and protein concentration of 8-12 %, all of which possessing high water holding capacities above 94.67 ± 2.33 %. The gel prepared from ISS-PPI of I_0.125 had higher strength than the gels of I_0.06 and I_0.08. Dynamic rheological measurement disclosed the thermo-reversibility of the gel being stable upon repeated heating and cooling process from 80 °C to 4 °C. The SDS-PAGE results showed that ISS-PPI were primarily composed of legumin, vicilin and convicilin and the latter two were considered mainly involved of reversible gelation. The internal pores of the I_0.06 gel at 12 % protein concentration were consistently sized and most uniformly distributed, as observed by scanning electron microscopy (SEM). Hydrogen bonds were shown to be dominant in forming the gel network structure during the cooling process while hydrophobic interactions and disulfide bonds were not significantly involved. This research opened up thermal reversible gelation of pea protein which hosts great opportunities in plant-based jelly-like foods formulation.