Yangyong Dai

Effects of low poly(vinyl alcohol) content on properties of biodegradable blowing films based on two modified starches

Biodegradable films from hydroxypropyl distarch phosphate (HPDSP)/poly(vinyl alcohol) (PVA) and cationic starch/PVA blends were obtained by extrusion blowing at ratios of 100:0, 95:5, 90:10, 85:15, and 80:20. The morphology, X-ray patterns, transparency, mechanical properties, thermal properties, and water vapor permeability (WVP) of the films were measured and compared. Scanning electron microscopic micrographs of the films showed continuous matrix texture as well as better compatibility between modified starches and PVA. X-Ray diffraction indicated the formation of ordered crystalline structures in the films during extrusion blowing. The addition of PVA to modified starches significantly increased their tensile strength (TS, 3.92 MPa) while decreasing their water vapor permeability (WVP, 3.23 × 10−10 g m−1 s−1 Pa−1). The starch/PVA composite films did not show phase separation.

Effects of bran, shorts and feed flour by ultra-fine grinding on rheological characteristics of dough and bread qualities

Wheat bran, shorts and feed flour are rich in dietary fiber and micronutrients. The effects of ultra-fine ground bran, shorts and feed flour on rheological characteristics of dough and bread qualities were investigated. Water absorption and dough development time gradually increased while mixing tolerance index and dough stability time decreased with the addition of bran, shorts and feed flour. The extension resistance and energy values for all blended flours were significantly higher than those of the control flour. The gluten index decreased while the gluten yield increased with the increase of bran, shorts and feed flour. Peak viscosity of the blended flour significantly decreased compared to the control flour. Pasting temperature rose from 67.05°C to 71.55, 72.6 and 69.25°C for bran, shorts and feed flour blends, respectively. The total scores of sensory evaluation and hardness of crumb texture significantly decreased with the increase of bran, shorts and feed flour.

Effects of Organic Modification of Montmorillonite on the Properties of Hydroxypropyl Di-Starch Phosphate Films Prepared by Extrusion Blowing

The knowledge gained from starch-nanocomposite-film research has not been fully applied commercially because of the lack of appropriate industrial processing techniques for nanofillers and starch films. Three organically modified montmorillonites (OMMTs) were prepared using a semidry kneading method. The effects of the OMMTs on the structures and properties of starch nanocomposite films, prepared by extrusion blowing, were investigated. The X-ray diffraction (XRD) analysis results revealed that the OMMTs with various quaternary ammonium salts possessed differing layer structures and d-space values. The results of the XRD and Fourier-transform infrared spectroscopy (FT-IR) showed that the starch–OMMT interaction resulted in a structural change, namely the starch–OMMT films possessed a balanced exfoliated and intercalated nanostructure, while the starch–MMT film possessed an exfoliated nanostructure with non-intercalated montmorillonite (MMT). The results of the solid-state nuclear magnetic resonance (NMR) analysis suggested that the starch-OMMT nanocomposite possessed comparatively large quantities of single-helix structures and micro-ordered amorphous regions. The starch–OMMT films exhibited good tensile strength (TS) (maximum of 6.09 MPa) and water barrier properties (minimum of 3.48 × 10−10 g·m·m−2·s−1·Pa−1). This study indicates that the addition of OMMTs is a promising strategy to improve the properties of starch films.