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The effects of fennel essential oil (FEO) and peppermint essential oil (PEO) on chitosan-based films were evaluated in this study. The results showed that the addition of FEO and PEO slightly increased the density and thickness, while significantly decreasing the moisture content, water swelling, and solubility properties. The color values (L, a, b, ΔE and whiteness index (WI)) of the composite films containing FEO and PEO changed obviously with a tendency toward yellowness, which was beneficial in resisting food decomposition caused by ultraviolet light. The differential scanning calorimetry (DSC) and fourier-transform-infrared (FTIR) results indicated that the addition of FEO and PEO affected the structure of the chitosan films, while the interaction between the chitosan and polyphenols in FEO and PEO established new hydrogen bonds and improved the thermal stability. The environmental scanning electron microscopy (ESEM) illustrated that the surfaces of the composite films containing FEO and PEO were smooth, but the cross-section was rougher than in pure chitosan film. Furthermore, the composite films containing FEO and PEO exhibited prominent antioxidant activity. In short, the novel active chitosan-based films with incorporated FEO and PEO present broad application prospects in fresh-cut meat or vegetable packaging. [ABSTRACT FROM AUTHOR]

The objective of the present study was to produce antioxidant hydrolysate from Tibetan egg white protein hydrolyzed with papain, and to investigate the effect of added papain egg white hydrolysate (PEWH) on the quality characteristics and amino acid profiles of yak milk yogurt. A response surface methodology (RSM) was utilized to analyze the effects of hydrolysis time (X1), the ratio of enzymes to substrates, and enzyme dosage (X3) on the superoxide anion radical (O2−) scavenging activity of hydrolysates. The predicted maximum value of O2− scavenging activity (89.06%) was obtained an X1 of 2.51 h, X2 of 4.13%, and X3 of 4500 U/g of substrate, almost approaching the experimental value (88.05 ± 1.2%). Furthermore, it was found that the addition of PEWH to yak milk can enhance acidification, sensory score, the number of lactic acid bacteria (LAB), and the amino acid content in yak milk yogurt. The results suggested that PEWH displayed an exceptional potential to be developed as a functional food ingredient that could be applied during the manufacturing process of yak milk yogurt. [ABSTRACT FROM AUTHOR]