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To optimize the process of ultrasound-assisted enzymatic extraction of total flavonoids from the roots of Houttuynia cordata, the appropriate liquid to material ratio, particle size, ethanol concentration, enzymatic digestion time, and enzyme addition was screened out by single-factor experiments, and the optimal conditions for the extraction of the flavonoids from Houttuynia cordata were optimized by Box-Behnken response surface. Meanwhile, the antioxidant activity of flavonoids was investigated. The results showed that the optimum extraction process was liquid to material ratio of 28:1 mL/g, particle size of

Plant essential oils, which can effectively extend the shelf life of fruits and vegetables, possess antioxidant, antibacterial and insect repellent properties, demonstrating them as promising natural preservatives for fruits and vegetables. However, the applications of plant essential oils in fruit and vegetable preservation are limited due to their disadvantages such as high volatility, poor stability and weak hydrophilicity, as well as strong aroma. Stable plant essential oil delivery systems that can form a barrier to the external environment provide new methods and approaches to overcome these limitations. In addition, the delivery systems can improve biocompatibility and have controllable release function, thus enhancing the utilization rate of plant essential oils. In the present paper, we review the composition, antioxidant, antibacterial and insect repellent activity and mechanisms of action of plant essential oils, and summarize various delivery systems including nano-emulsions, microemulsions, microcapsules, and liposomes and their preparation methods, and discuss the major factors affecting the encapsulation efficiency, particle size and physical stability of plant essential oils such as preparation methods, emulsifiers, the type and concentration of wall material. Finally, we summarize the applications and prospects of delivery systems for plant essential oils in fruit and vegetable preservation with the aim of providing a theoretical foundation for the development of new, effective fruit and vegetable preservatives.

There are various species of plants in the Lauraceae family, and these plants are widely distributed in China. Their essential oils have many biological activities, such as bacteriostatic, antioxidant and insect repellent activities and are ideal natural preservatives, effective antioxidants, and green insect repellents. Therefore, they are of research significance and have broad application prospects. The effects of the growth cycle, plant parts, extraction methods, and geographical environment on the major components of essential oils from Lauraceae plants (LEO) are reviewed with a focus on the antimicrobial, antioxidant and insect repellent activities and mechanisms of LEO. In addition, common edible coatings, microencapsulation, and nano-emulsion technologies based on LEO for food packaging and preservation are summarized. We hope that this review will provide a theoretical basis for the application of LEO in food preservation.