The Preservation And Safety Of Nanometer Silver-oxidized Starch Coating On Seedless Grape And Nanfeng Orange

In recent years,film preservation technology has become one of the research hotspots of fruit and vegetable preservation due to its green,safe,efficient and convenient advantages.In this paper,oxidized starch as the film substrate,Ag NPs as the inorganic antibacterial agent,and tea polyphenols as the natural preservative to prepare the compound antibacterial preservative film to explore its preservation effect on seedless grape and nanfeng orange.The first part,preparation of Ag NPs by Liquid Phase Chemical Reduction.The lower the rotor speed in the preparation process,the better the performance of the silver nanoparticles.The ultraviolet-visible absorption spectra and transmission electron microscopy showed that the silver nanoparticles with uniform size distribution were prepared at low rotational speed and had good stability.In the second part,the effects of oxidized starch-nano-silver coating on two kinds of fresh fruit were studied.It is found that this method has good preservation effect.The coating can maintain the water and nutrients inside the fruit and reduce the weight loss rate.The antioxidant properties of tea polyphenols and the antibacterial properties of silver nanoparticles can significantly delay the decrease of soluble solids,titratable acids and vitamin C.The film also keeps the relative conductivity of seedless dew grapes low.The shelf life of the two fresh fruits after coating can be extended by 3 to 5 days.When the amount of tea polyphenols in the coating liquid is 2 to 3%,the freshness preservation effect is better.The third part explores the safety of the coating.The migration and accumulation of silver nanoparticles in two fruits were investigated by atomic absorption spectrometry.The storage time was prolonged and the mobility of Ag NPs in fruit increased.The mobility of silver nanoparticles after peeling was only 1 ~ 9%,and its accumulation was far lower than the European limits.However,the mobility of silver nanoparticles was as high as 22 ~ 37% when the fruit was washed without peeling,and its accumulation was higher than the European Union limit after 1 week of storage.This filmpreservation method is more suitable for peeling fruits and vegetables.