Heat-induced aggregation behavior of wheat gluten after adding citrus pectin with different esterification degree

Abstract

Wheat gluten aggregation during heat treatment is beneficial to the final quality of gluten-based products. Exogenous pectin can affect gluten aggregation. However, the effect of pectin with different degrees of esterification on the heat-induced aggregation behavior of gluten and its possible mechanism are still unclear. Thus, the heat-induced aggregation behavior of gluten after adding pectin with different esterification degree was studied in this study. When the temperature was raised from 25 °C to 95 °C, pectin affected gluten aggregation and was related to the degree of esterification. Specifically, the results of rheological properties and particle size indicated that low-ester pectin improved the viscoelasticity of gluten and promoted gluten aggregation. Thermal properties revealed that enthalpy of gluten added with low-ester pectin (37%) increased from 92.96 J/g to 95.40 J/g during heating process. Structurally, the fluorescence intensity and surface hydrophobicity of gluten added with low-ester pectin (37%) were lower than those added with high-ester pectin (73%). In addition, low-ester pectin (37%) significantly increased the disulfide bond content (from 15.31 μmol/g to 18.06 μmol/g) and maintained β-sheet content of gluten compared with gluten alone at 95 °C, indicating that low-ester pectin was more likely to induce gluten aggregation. However, scanning electron microscope showed that the gluten added with low-ester pectin (46%) exhibited a denser network structure at 95 °C than that added with low-ester pectin (37%). These results will provide a theoretical base for the regulation of gluten aggregation and the quality of gluten-based products by pectin with different esterification degree.