Changes of physicochemical and structural properties of wheat gluten induced by apple pectin with different molecular weights

Abstract

In this study, apple pectin (AP) was first subjected to ultrasonic degradation to obtain four kinds of pectins (AP₅₁₈, AP₃₈₄, AP₃₃₅ and AP₂₉₇) with different molecular weights (Mw). Subsequently, the structure-activity relationship between the Mw of AP and the impact of AP on gluten characteristics and network structure was investigated. The result indicated that AP and gluten protein mainly interacted through hydrogen bonds, thus changing the gluten characteristics and network structure. Notely, the changes of gluten properties and network were closely related to the Mw of AP. Specifically, low-Mw AP enhanced the water holding capacity and rheological properties of gluten protein. Compared with the control group, AP₂₉₇ significantly increased the surface hydrophobicity of gluten protein from 86.19 to 105.33, while decreasing the fluorescence intensity of gluten protein from 224.17 to 200.23. The result indicated that AP₂₉₇ was more likely to interact with gluten protein and form protein aggregates. Meanwhile, compared with AP₅₁₈, AP₂₉₇ significantly increased the enthalpy (from 120.83 J/g to 164.82 J/g), β-sheet content (from 32.52 % to 44.28 %), and disulfide bonds content (from 15.67 μmol/g to 19.38 μmol/g) of gluten protein. These above results suggested that the network structure of gluten protein was improved and became more stable. In addition, SEM also further confirmed that AP₂₉₇ could better maintain the gluten network structure. These findings can be said to offer theoretical support for the rational application of AP with varying Mw in wheat flour products.