The effect of degree of esterification of pectin on the interaction between pectin and wheat gluten protein

Pectins with different degree of esterification (DE) (37, 46, 58, 63 and 73%) were prepared by alkali method and the effect of the DE on the interaction between pectin and wheat gluten protein was investigated in the present study. The results showed that low-ester pectin increased the water holding capacity (WHC) and viscoelasticity of gluten protein. The low-ester pectin promoted the conversion of sulfhydryl groups (-SH) to disulfide bonds (-S-S-). Compared with control gluten protein, the -S-S- content of gluten protein added with low-ester pectin significantly increased from 18.82 to 21.65 μmol/g, indicating that the gluten network structure was strengthened. Compared with high-ester pectin, low-ester pectin increased β-sheet content by 18.48%, suggesting that the stability of gluten protein was enhanced. In addition, intrinsic fluorescence spectra showed that the maximum intrinsic fluorescence intensity (Imax) of gluten protein added with low-ester pectin decreased from 826.53 to 630.47. Meanwhile, the surface hydrophobicity (H0) of gluten protein added with low-ester pectin decreased from 497.33 to 419.82. These results showed that low-ester pectin interacted more easily with gluten protein than high-ester pectin and formed some aggregates. Moreover, SEM and mercury intrusion results indicated that the low-ester pectin (DE-46%) was beneficial to maintaining the gluten network structure. These results will provide a theoretical basis for the application of pectin in wheat flour products.