Effects Of Atmospheric Pressure And Low Temperature Plasma On Postharvest Blueberry Quality And Surface Fungal Diversity

Recently,atmospheric cold plasma(ACP)is considered as an efficient,flexible,economical,and ecofriendly non-thermal method for food sterilization,which can effectively inactivate microorganisms,therebyextending the shelf time of food.As a highly nutritious fruit,blueberries are known for rich anthocyanins,which has strong antioxidant properties.However,blueberries are susceptible to microbial infections during postharvest storage,which affect their quality.Therefore,this study investigates the effects of ACP treatment on the quality and fungal diversity of postharvest blueberries during storage.This paper mainly includes the following four parts:(1)Detection of electrochemical characteristics of ACP: This study measured the voltage,current,chamber temperature and humidity during ACP discharge.Meanwhile,optical emission spectroscopy(OES)and ozone detectors were used to detect the reactive oxygen and nitrogen species(RONS)produced by plasma device.The results show that the voltage and current were stable during the ACP discharge process,which produced various RONS.(2)The influence of ACP on blueberries natural flora and external Botrytis cinerea(B.cinerea)during postharvest storage: This study evaluated the effects of ACP treatment on the population of intrinsic micororganisms on the blueberries surface and the natural fruit decay during postharvest storage.Meanwhile,the antifungal effects of ACP anainst the B.cinerea in vitro and on blueberries were measured.The results show that ACP treatment could effectively control the growth of native microorganisms(bacteria and fungi)on the blueberries and reduced the natural decay incidence of blueberries during 10 d postharvest storage.Meanwhile,ACP treatment significantly inhibited the spore germanitaion and mycelial growth of B.cinerea in vitro and reduced the decay incidence of blueberries artificially inoculated with B.cinerea.(3)The influence of ACP on the quality of postharvest blueberries: This study measured the sensory quality(firmness and color)and physicochemical quality(pH,ORP,conductivity,free radicals,antioxidant enzymes,nitrates,nitrites,and anthocyanins)of blueberries with or without ACP treatment during postharvest storage.Meanwhile,the surface morphology and chemical bonds of the blueberry peel was observed by scanning electron microscope(SEM)and fourier transform infrared(FTIR)spectroscopy.The results show that short-term(?15min)ACP treatment could significantly reduce the degree of lipid peroxidation and had little influence on the firmness,pH,ORP and anthocyanin content.However,20 min ACP treatment caused severe oxidative damage to the blueberry peel,resulting in the softening of the fruit and the leakage of anthocyanin.In summary,short-term ACP treatment could markedly improve the postharvest quality of blueberries,which is a promising method for postharvest preservation of blueberries.(4)The influence of ACP on the fungal diversity on blueberries during postharvest storage: Illumina high-throughput sequencing technology was used to analyze the effects of ACP treatment on the fungal community structure on the surface of blueberries.The results show that ACP treatment changed the community structure of fungi on the surface of blueberries during 40 d postharvest storage.The ACP treatment significantly reduced the abundance and OTUs number of the fungal community on the surface of blueberry,but had no significant effects on the diversity of the fungal community.