Abstract: A nano-packaging material was prepared by blending polyethylene (PE) with nano-Ag, nano-TiO2 and kaolin, structurally characterized and analyzed for physical properties. Its effect on quality preservation of lettuce was investigated by periodically measuring the changes of weight loss rate, chlorophyll, vitamin C and MDA contents, and polyphenol oxidase (PPO) activity during refrigerated storage. It was observed that nano-particles were evenly distributed in the composite material. Compared with ordinary PE material, it showed an increase in tensile strength of 31.69%, a decrease in water vapor permeability of 28.07%, and a decrease in oxygen permeability of 2.10%. After 14 d of storage at 4 ℃, the weight loss rate, MDA content and PPO activity of lettuce packaged with the nano-material were 1.35%, 23.01 nmol/g and 5.43 U/g, respectively, which were those from ordinary PE packaging (2.75%, 26.35 nmol/g and 7.63 U/g, respectively), while the nano-material resulted in significantly increased VC and chlorophyll contents in lettuce in comparison with the control (ordinary PE material). This composite material could better maintain the sensory quality and nutrients of lettuce during cold storage and consequently extend its shelf life.

Key words: lettuce, nano-packaging material, preservation