Effect of ionic strength on assembly behaviors and rheological properties of rice glutelin based fibrils

This study investigated the assembly behaviors and rheological properties of rice glutelin based fibrils with varying ionic strengths (0-150 mM). The addition of NaCl accelerated the growth rate of fibrils, likely due to the effect of electrostatic screening and specific ions-protein interactions. In the morphological studies, the lower ionic strength (50 mM) promoted the elongation of fibrils, whereas the average contour length reduced from 1005 to 470 nm at the ionic strength of 150 mM, since the chaotic, haphazard aggregation of building block at higher ionic strength was not beneficial to the elongation of fibrils. The increased ionic strength facilitated the polypeptides hydrolysis, leading to the increased content of released smaller peptides (<10 kDa). The released peptides assembled into fibrils with stacked beta-sheet, and the addition of salt promoted the formation of ordered secondary structure. The rheological properties of fibrils were changed with the effect of ionic strength, attributing to the increased fibrils density and the formation of larger fibrillar aggregates. This work provides a new insight into the effect of ionic strength on the formation and rheological properties of rice glutelin based fibrils, which will offer a promising technology for development of the innovative and agriculturally-sustainable food ingredient.