Prolamin, an important storage protein of grains, is able to dissolve in aqueous ethanol because of its unique hydrophilic−hydrophobic property. The low allergenicity of prolamin makes it a good replacement of gluten to maintain textural properties of gluten-free food; the film-forming property makes it an excellent coating material for candy or nuts to extend shelf life and reduce flavor loss. However, the prolamin extraction process is not environment friendly with high energy and water consumption. The utilization of the switchable extractant will minimize the environmental impact of prolamin processing and get maximum utility out of the extractant and cut down energy and water consumption as well as simplify the extraction procedures. A switchable composite extractant (SCE) has been developed for a complete extraction of zein, which is the most abundant prolamin. By virtue of the solvent temperature-swing property, the SCE-simplified zein extraction increased the solvent usefulness and reduced the energy and water consumption. The electrophoretic patterns of the protein extracted by the SCE and aqueous ethanol showed the same main bands as the commercial counterpart. The extracted zein showed a similar protein recovery rate compared to aqueous ethanol (28.74% vs 29.38%) and a similar amino acid profile and solubility in aqueous ethanol (92.35% vs 92.06%) compared to the commercial counterpart with better tensile properties (4.38 MPa vs 2.68 MPa). The advantages of this new technique are numerous: (a) energy and water consumption was largely reduced; (b) procedures were simplified since no rectification of ethanol was needed; (c) potential harm of ethanol vapor to workers or industrial environment was minimized; and (d) no additional procedure was needed for the recycling of the SCE. This method minimizes the environmental impact of prolamin processing, optimizes the extractant, reduces the energy and water consumption, and simplifies the extraction procedures.

No abstract

The application of curcumin (Cur) in fat-free food is limited due to its poor water solubility, stability, and bioaccessibility. In this study, zein-gum arabic-tannic acid (zein-GA-TA) composite particles with high physical stability were fabricated to deliver Cur (ZGT-Cur). Their stability and in vitro release properties were also evaluated. The results showed that the thermal and photochemical stability of Cur was improved after loading into composite particles. Meanwhile, the retention rate of Cur in ZGT-Cur composite particles was enhanced compared with Z-Cur or ZG-Cur particles. Fourier transform infrared (FTIR) spectroscopy confirmed that the hydrogen bond within the particles was greatly enhanced after the addition of tannic acid (TA). The in vitro antioxidant activity of Cur in ZGT-Cur composite particles was higher in terms of 2,2'-azino-bis (ABTS) (93.64%) and 1,1-diphenyl-2-picrylhydrazyl (DPPH) (50.41%) compared with Z-Cur or ZG-Cur particles. The bioaccessibility of Cur in ZGT-Cur composite particles was 8.97 times higher than that of free Cur. Therefore, the particles designed in this study will broaden the application of Cur in the food industry by improving its stability and bioaccessibility.

The destabilization of zein gel particles by salt ions seriously limits their practical application. In this study, zein gel particles exhibiting excellent stability to salt ions were developed by grafting gum arabic with tannic acid. Gum arabic (GA) was first coated onto the surface of zein gel particles, followed by addition of tannic acid to further reinforce non-covalent cross-linking between GA and the zein gel particle surface. The stability of the gel particle dispersions was characterized by Turbiscan analysis, gel particle diameter changes and visual inspection of phase separation. The tannic acid-treated zein–GA gel particles were highly protected from precipitation or aggregation in the presence of NaCl (0–3 mol/L) at different pH values (4.0, 7.0 or 8.5). The gel particles prepared in this study will therefore have broader applicability in different pH and salt ions ion environments.

As consumers’ interest in nature-sourced additives has increased, zein has been treated hydrothermally under alkaline conditions to prepare a nature-sourced emulsifier. The effects of mild hydrothermal–alkaline treatment with different temperatures or alkaline concentrations on the emulsifying properties of zein were investigated. The emulsification activity and stability index of zein hydrolysates increased by 39% and 164%, respectively. The optimal simple stabilized emulsion was uniform and stable against heat treatment up to 90 °C, sodium chloride up to 200 mmol/L, and pH values ranging from 6 to 9. Moreover, it presented excellent storage stability compared to commonly used food emulsifiers. The surface hydrophobicity caused the depolymerization of the tertiary structure of zein and the dissociation of subunits along with exposure of hydrophilic groups. The amino acid composition and circular dichroism results reveal that the treatment dissociated protein subunits and transformed α-helices into anti-parallel β-sheets and random coil. In conclusion, mild hydrothermal–alkaline treatment may well contribute to the extended functional properties of zein as a nature-sourced emulsifier.