Abstract: Abstract: Using "Mei Zao" cherry as test material, polylactic acid/poly-3-Hydroxybut-yrate-co-4-hydroxybutyrate (PLA/P34HB) as substrate, diatomaceous earth with peppermint essential oil as sustained release antibacterial The agent is prepared by using a cast film forming process to prepare an active antibacterial film for preserving the cherry. The physicochemical indexes such as the composition of the top air in the fresh-keeping bag and the mass loss rate during storage of the cherries at (4±1) °C were studied. The effect of the change of the water state inside the cherry on the quality was investigated by low-field nuclear magnetic resonance (LF-NMR). The results showed that the oxygen transmission rate (OTR) of the film with diatomite loaded with peppermint essential oil increased from 250.37（cm3?m-2?d-1?Mpa-1）to 290.45（cm3?m-2?d-1?Mpa-1）compared with PLA/P34HB film. The improvement of OTR was beneficial to maintain the nutrient composition and texture of cherry. LF-NMR showed that the film containing menthol oil with menthol oil kept the water activity of cherries very well. When the storage time was 12 days, the combined water peak area ratio was about 2 times that of the bare group, which effectively delayed the corruption of the cherries in the package and prolonged the Shelf life.

Key words: Keywords: polylactic acid, peppermint essential oil, cherry, preservation, LF-NMR