A novel strategy of vacuum-packaged chicken feet for bacteriostasis and antioxidation: Pickering emulsion of ZnO / Star anise essential oils combined with radiofrequency treatment

Vacuum-packed meat products that require a longer shelf-life need high temperatures as secondary sterilization. In order to reduce the quality change and flavor loss caused by autoclaving, ZnO nanoparticles (ZnO NPs) equipped with star anise essential oil (SAEO) were used to make a Pickering emulsion (ZS) to treat cooked tiger skin chicken feet, and then combined with radiofrequency (RF) treatment for pasteurization. The emulsions made from the combination of different concentrations of ZnO NPs and SAEO were evaluated, and a suitable concentration combination (0.03 % (w/w) ZnO NPs, 0.4 % (v/v) oil phase) was selected for the experiment. In the subsequent experiments, the treatment groups of ZS treatment combined with RF treatment for 20 min (ZSRF-20) and 30 min (ZSRF-30) were able to maintain the microbial load of the samples at a low level (reducing the CFUs by about 2 logarithms compared with the control group). Comparing with high pressure steam (HPS), the synergistic treatment group showed less change in appearance and color, and had a better mitigating effect on the degree of lipid oxidation of the samples during the pasteurization process, with CD value and TBARS value of 0.028 mmol/g and 0.065 μg/g with ZSRF-30 treatment. In addition, the sulfhydryl content indicated that the synergistic pasteurization treatment slowed down protein oxidation. Volatiles and flavor were evaluated and the synergistic treatment group was able to reduce the flavor loss of the samples. The findings suggested that the treatment with ZSRF would be a novel approach to preserve the quality of vacuum-packed chicken feet.

Industrial relevance

Pickering emulsion containing ZnO NPs and Star anise essential oil was prepared and combined with radiofrequency heating for co- pasteurize of vacuum-packed tiger chicken feet. RF can cause microbial inactivation, and its mechanisms include thermal and non-thermal effects. Compared with autoclaving, the use of RF for pasteurization better preserves food flavor and reduces variation in quality. Vegetable oil can enhance the wettability of ZnO NPs and enhance their emulsification properties. The emulsion prepared by ZnO NPs and plant essential oil showed antibacterial properties. Combined with radiofrequency heating, flexible pasteurization can be achieved.