Sodium Hydroxide-Free Soy Protein Isolate-Based Films Crosslinked by Pentaerythritol Glycidyl Ether

Multifunctional soybean protein isolate-graft-carboxymethyl cellulose composite as all-biodegradable and mechanically robust mulch film for "green" agriculture

Multifunctional mulch films with robust mechanical behaviors of biopolymer-based biodegradable mulch materials were highly demanded in promoting the development of "green" agriculture. Herein, a sort of mechanically robust and all-biodegradable soybean protein isolate-graft‑sodium carboxymethyl cellulose composite mulch film was innovatively proposed through the amidation reactions between -COOH on protonated sodium carboxymethyl cellulose and -NH2 on soybean protein isolate. Arising from the reinforced intermolecular interactions upon chemical covalent bonds and physical hydrogen bonds, the maximum tensile strength and the elongation at break were increased from 10.61 MPa and 20.67 % for sodium carboxymethyl cellulose film to 42.15 MPa and 24.8 % for the optimized soybean protein isolate-graft‑sodium carboxymethyl cellulose composite mulch film, respectively. In addition, experimental results showed that the optimized soybean protein isolate-graft‑sodium carboxymethyl cellulose composite mulch film possesses soil moisture retention and controlled urea release properties. When employed as mulch film in practice, the cabbage seed presents higher germination when soil was covered with this versatile mulch film compared to commercial low-density polyethylene mulch film. Our discoveries build a prototype for the manufacture of eco-friendly mulch films with high mechanical strength, soil moisture retention, controlled urea release features.

Development and characterization of taro starch-casein composite bioactive films functionalized by micellar pomegranate peel extract (MPPE)

Starch-casein composite (solid matter content) based bioactive films incorporated with micellar pomegranate peel extract (MPPE) at different concentrations (10, 25, 50, and 100 wt% with respect to base solid matter content) were developed. The extract-free film was used as a control. The bioactive films were characterized for physicochemical, mechanical, barrier, structural, thermal, and bioactive properties. Decreased ζ-potential and surface tension, increased particle size, and improved rheological properties of MPPE added film-forming dispersion (FFD) were recorded. Among all the physical properties of bioactive films, only contact angle was reduced. An increase in MPPE concentration exhibited less hardness, more extensibility, and an excellent barrier to water vapor permeability than the control film. Increased MPPE concentration showed a decline in transparency (%) and lightness (L*) resulting into distinct color to the film. Structural compactness and integrity of the films were confirmed by SEM and XRD patterns. Improved functional interaction and thermal reliability of bioactive films were noted. The interaction patterns between starch-casein composite and MPPE bioactives indicated the development of covalent links. Excellent bioactivities with the slow release of bioactives in hydroalcoholic environment, confirmed by the kinetic study. Remarkable antibacterial effect was noted against E. coli and S. aureus by the films. Overall, increasing the concentration of MPPE in bioactive film showed improved physicochemical strength; hence, prepared bioactive films could be used as food coatings.

Reinforcement of Bonding Strength and Water Resistance of Soybean Meal-Based Adhesive via Construction of an Interactive Network from Biomass Residues

Soybean meal-based adhesives are attractive potential environmentally friendly replacements for formaldehyde-based adhesives. However, the low strength and poor water resistance of soybean meal-based adhesives limit their practical application. This study was conducted to develop a natural fiber-reinforced soybean meal-based adhesive with enhanced water resistance and bonding strength. Pulp fiber (PF), poplar wood fiber (WF), and bagasse fiber (BF) were added as fillers into the soybean meal-based adhesive to enhance its performance via hydrogen bonding between the PF and the soybean meal system. The enhanced adhesive exhibited a strong crosslinking structure characterized by multi-interfacial interactions wherein PF served as a bridging ligament and released residual stress into the crosslinking network. The crosslinked structure and improved interfacial interactions were confirmed by Fourier transform infrared (FTIR) spectrophotometry, thermogravimetric analysis (TGA), and scanning electron microscopy (SEM) measurements. Plywood bonded with 4 wt % PF-containing soybean meal-based adhesive exhibited a wet shear strength (1.14 MPa) exceeding that of plywood bonded with the control group by 75.4% due to the stable crosslinking network having efficiently transformed stress and prevented the permeation of water molecules.