The aim of this study was to investigate the effects of hydrothermal treatment at different temperatures and times on the structure and functional properties of quinoa protein isolate (QPI). The structure of QPI was investigated by analyzing changes in the intrinsic fluorescence spectrum, ultra-violet (UV) spectrum, and Fourier transform infrared spectrum. The solubility, water/oil-holding capacity, emulsifying activity, and emulsion stability of QPI were studied, as were the particle size and the thermogravimetric properties of QPI. The results showed that the average particle size of QPI gradually increased with the increase in hydrothermal treatment time and temperature, and reached a maximum value of 121 °C for 30 min. The surface morphology also became rough and its thermal stability also increased. The endogenous fluorescence and UV spectral intensity at 280 nm decreased gradually with increasing hydrothermal treatment time and temperature, and reduced to the minimum values at 121 °C for 30 min, respectively. After hydrothermal treatment, the secondary structure of QPI tended to be disordered. The functional properties of QPI after treatment were all superior to those of the control. The results of this study might provide a basis for the processing and utilization of QPI.

The application of natamycin as a natural fungicide in edible coatings is challenging because of its low aqueous solubility. In this study, the natamycin/methyl-β-cyclodextrin (N/ME-β-CD) inclusion complex was fabricated and incorporated into waxy corn starch-based coatings for postharvest treatments. The phase solubility of natamycin in the presence of ME-β-CD at 293.2 K, 303.2 K, and 313.2 K is determined and used to calculate the process thermodynamic parameters. The N/ME-β-CD inclusion complex was confirmed and characterized by FTIR and 1H NMR spectroscopy. The results indicated that the inclusion complex was formed and the hydrophobic part (C16-C26) of natamycin might be partially inserted into the cavity of ME-β-CD form the wide rim. The effects of N/ME-β-CD incorporated starch-based coatings (N/ME-β-CD S coatings) on postharvest treatments of cherry tomatoes were evaluated in vivo. The N/ME-β-CD S coatings could reduce weight loss, delay fruit ripening, and inhibit fruit decay caused by Botrytis cinerea in tomato fruit during storage.

ε-Polylysine (ε-PL) is a natural preservative of antimicrobial peptides with broad spectrum and high antibacterial properties. The electrostatic complex delivery system formed by ε-PL and whey protein can be used to maintain the stability of ε-PL and solve the problem of limited application of protein-based food. This work aimed to study the interaction between ε-PL and whey protein by multiple characterization methods. The spectroscopy results showed static quenching type and new stretching of C=O for ε-PL-whey protein complexes. Microstructure studies showed that the combination of ε-PL and whey protein made the structure of the complexes become rough and dense. The interaction between ε-PL and whey protein could improve the stability of the complexes system during storage. Additionally, the interaction affected critical gel temperatures and gel texture properties of complexes with change of whey protein concentration, mass ratio of ε-PL to whey protein, pH value in alkaline solutions, and ion concentration. Overall, this study confirmed the interaction between ε-PL and whey protein, and it will provide a reference for the application of ε-PL in protein food matrix.