Further interpretation of the underlying causes of the strengthening effect of alkali on gluten and noodle quality: Studies on gluten, gliadin, and glutenin

Alkali significantly enhanced gluten strength and noodle texture. To further understand the underlying mechanisms of the gluten strengthening effect of alkali, the macroscopic rheological properties, microstructure, intermolecular interactions, water mobility, molecular weight distribution (MWD) and structure, and the molecular chain morphology changes of gluten and its subfractions (glutenin and gliadin) were separately investigated. Alkali increased the G′ and G″ of gluten and glutenin fractions. Scanning electron microscopy (SEM) images confirmed that alkali induced a more compact structure in all fractions and a membrane-like structure in gluten and glutenin. Quartz crystal microbalance with dissipation (QCM-D) results demonstrated that alkali promoted alkali/protein-protein interactions in gluten and glutenin fractions. Hydrophobic interactions and water-solids interaction were enhanced by alkali in all fractions. Glutenin fraction was shown to play a key role in the protein polymerization of fresh gluten samples in the presence of alkali, while both glutenin and gliadin contributed to the enhanced polymerization during cooking. Atomic force microscopy (AFM) images showed that alkali induced remarkable aggregations of protein molecular chains in gluten system.