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The impact of adding zein on the gluten network during extruded noodle processing and the quality of the noodles by extrusion-cooking were investigated. These changes were studied by size exclusion-high performance liquid chromatography (SE-HPLC), free sulfhydryl (SH) measurement, non-covalent interactions, Fourier-transform infrared spectroscopy (FTIR), particle size analysis, confocal laser scanning microscopy (CLSM), and scanning electron microscopy (SEM). Zein reduced the protein aggregation, resulting in a higher free sulfhydryl content and increased hydrogen bonds and hydrophobic interactions during noodle processing. Moreover, Zein reduced the relative content of β-sheets by 4.54% and 7.48% at the extrusion and cooking stages, respectively. Zein decreased the particle size during extrusion but increased it during cooking. Zein improved the compactness and strength of noodle microstructure during cooking, exhibited higher hardness and impeded water mobility compared to extruded noodles made only with wheat flour (WF). The extruded noodles containing zein showed a significant increase of 26.10% and 61.11% in tensile strength and distance, respectively. Zein did not cause significant changes in the cooking loss and water absorption in the extruded noodles. Research on the impact of zein on protein during the processing of extruded noodles could provide a dependable approach and valuable mechanistic insights for improving the quality of extruded noodles. [Display omitted] • The inclusion of zein in the extruded noodle processing resulted in reduced protein aggregation. • Zein increased hydrogen bonds and hydrophobic interactions during extruded noodle processing. • Zein reduced the relative content of β-sheets in extruded noodles. • Zein improved the quality of extruded noodles to have higher hardness, and tensile force and distance. [ABSTRACT FROM AUTHOR]

Abstract: The effect of frozen storage on the water sorption capability, water mobility, secondary structure, thermal and microscopic properties of gluten-, glutenin- and gliadin-rich fractions were investigated. Lower water sorption capability was observed for samples after frozen storage, suggesting that more hydrophobic moieties were exposed. Conversions of α-helix structure to β-turn structures and specific β-sheet structures were observed in the secondary structure analysis of gluten- and gliadin-rich fractions. Frozen storage induced higher water mobility in hydrated gluten proteins. Similar changes were observed in gluten-water and gliadin-water systems, implying that the changes were primarily attributed to subdued gliadin-water interactions and gliadin can stabilize glutenin network to confine the water mobility. Meanwhile, thermo gravimetric analysis (TGA) and differential scanning calorimetry (DSC) showed that thermal degradation temperature decreased while thermal denaturation stability increased in gluten- and glutenin-rich fractions with the increasing time of frozen storage. However, the enthalpies of all the gluten proteins decreased, indicating more disordered structures in the aged gluten proteins. The micrographs of scanning electron microscopy (SEM) also confirmed more disordered and weak structures in gluten- and glutenin-rich fractions induced by frozen storage. Furthermore, consistent changes in gluten-, glutenin- and gliadin-rich fractions indicated that the variations in conformational, thermal and microscopic properties of gluten might originate from glutenin and gliadin upon frozen storage. [Copyright &y& Elsevier]

Abstract: In this work, a dual-retrogradation treatment (gelatinization–retrogradation–gelatinization–retrogradation) was designed for preparing slowly digestible starch (SDS) products from rice starch. The results showed that a maximum SDS yield in the tested samples increased from 39.3% to 56.7% by the dual retrogradation with the time interval of 36 h. The dual retrogradation also seemed to increase with the melting temperature range (T c–T o) of the SDS products. This increase indicated that more imperfect crystallites were formed during the dual-retrogradation treatment. Furthermore, compared to the single retrogradation, the dual retrogradation generated larger cavities and more solid connection parts in the SDS products. This internal microstructure could result in the increase of slow digestibility. These findings suggest that the dual retrogradation can be used in starchy products to increase the yield of SDS. [Copyright &y& Elsevier]

Abstract: Effect of pectin (34–40% esterification), glycerol and trehalose at two concentrations (0.1% and 0.5%, wt./wt%) on physicochemical and emulsifying properties of phosvitin (Pv) was investigated under the mild conditions (oil volume fraction, 0.25; protein concentration, 5 mg/mL; 10 mM sodium phosphate buffer, pH 7.0). Pv showed better emulsifying properties than sodium caseinate (Sc). Glycerol (0.5%) significantly increased the emulsifying activity index (EAI) of Pv from 19.8 to 20.9 and the emulsion stability index (ESI) from 67.6 to 75.1. The higher ESI of Pv was also obtained by 0.1% pectin and 0.5% trehalose. The results obtained from circular dichroism (CD) spectra indicated that all the tested additives displayed slight effect on the unfolded structure of Pv. Furthermore, fluorescence pattern demonstrated that glycerol and trehalose increased the hydrophobicity of Pv, while pectin displayed an opposite effect. All emulsions exhibited a shear-thinning behavior and the flow behavior was fitted to the power law model. Frequency sweeps of the emulsions illustrated that they behaved like a viscous liquid. [Copyright &y& Elsevier]