Effect Of Cold Plasma On Blueberry Juice And Sterilization Mechanism Of It

The bactericidal effect of Bacillus sp.in the rot blueberry juice was targeyed in this study.The mortality rate of Bacillus and the effect of quality of blueberry juice was investigated under different treatment time,oxygen concentration and pulse frequency.Moreover,the lethal mechanism of Bacillus was analyzed by atomic emission spectroscopy,flow cytometry and electron microscopy.The main results are as follows:(1)Two strains yeast and four strains bacteria were isolated from the decayed blueberry fruit.After cell morphology observation and molecular biological identification,they were identified as Pichia kudriavzevii,Hanseniaspora uvarum,Klebsiella pneumoniae strain,Bacillus sp.Strain,Serratia marcescens.Strain,Chryseobacterium takakiae strain.According to the results of the comprehensive Koch's rule,it was known that Hansenula sinensis and Bacillus were the dominant bacteria causing the corruption of blueberry fruits.(2)Under the different oxygen concentration and pulse frequency of the cold plasma,the atomic emission spectra of A,B,C,D and E groups did not change significantly.However,under the conditions of five groups,the strength of the main active particles in group E(Oxygen concentration is 1%,pulse frequency is 1500Hz)was the largest.(3)The mortality rate of Bacillus spp.after cold plasma treatment was proportional with time,oxygen concentration and pulse frequency.And then,the proportion of cells with intact cell membrane and green fluorescence emission decreased significantly(p<0.05).At the same time,cell membrane damage,leakage of contents,and cytoplasmic inhomogeneity were also appeared after cold plasma treatment.Moreover,the spectral results showed that the active substances may be the main cause of cell lipids,proteins,DNA,etc.,and finally leading the cell death.(4)The total phenolic content of blueberry juice was significantly(p<0.05)increased after cold plasma treatment and significantly(p<0.05)decreased the contend of anthocyanin and Vc.In addition,the free radical scavenging rate and total reducing power of blueberry juice were increased,but DPPH free radicals and OH radical scavenging were less affected.It was found that total phenol was the most prominent in antioxidant capacity,followed by anthocyanin and ascorbic acid through correlation analysis of the nutrient parameters and the quality parameters of antioxidant capacity.This also showed that phenolic are an important material for the antioxidant effects of blueberries.Meanwhile,Anthocyanins and Vc were the main constituent parameters of the antioxidant capacity of blueberries.