Effect of different amino acid composition on hygroscopicity of two antioxidant pentapeptide powders from soybean protein by DVS and LF-NMR

In order to evaluate the effect of amino acid composition on hygroscopicity, this study investigated different adsorbed water mobility and distribution of two soybean antioxidant pentapeptides, Ser-His-Cys-Met-Asn (SHCMN) and Ser-His-Glu-Cys-Asn (SHECN) powder by dynamic vapor sorption and low-field nuclear magnetic resonance (LF-NMR). In addition, effect of adsorbed water on its physical structure at microstructural level was observed by scanning electron microscope (SEM). The results show the hygroscopicity of SHECN is greater than that of SHCMN and moisture-induced crystallization of SHECN occurs. The maximum of mass change of SHCMN was 17.67 and 33.53% for SHECN. After treated by 75% RH for 28 h, the physical state of SHCMN pentapeptide powder still presented as a free flowing powder. However, the amorphous structure of SHECN powder was converted from a free flowing powder into a rubbery sticky mass. These results could provide insight into the interaction of water and peptide powder.