Application of plasma-activated water for Escherichia coli decontamination and shelf-life extension of kale

The aim of this study was to examine the effectiveness of plasma-activated water(PAW)for inactivating Escherichia coli(E.col)and retention of key quality factors for kale.Different plasma discharge times(1,2,3,4,5,and 10 min)and different exposure times(2,4,6,8,10,and 15 min)were used to investigate the inactivation effect of E.coli spot-inoculated on kale.The influence of different exposure times on the pH,hardness and color of kale was studied post-treatment.In addition,the effects of PAW on the shelf-life of kale over 12 d of storage at 4℃ were investigated.The results showed that after the treatment of 5-PAW-8(8 min treatment by PAW generated by 5 min plasma discharge),the population of E.coli on kale was reduced by approximately 1.55 log colony-forming units(CFU)/g and the changes in pH,hardness and color of kale were not significant(P>0.05).During the storage period after 5-PAW-8 treatment,the hardness,weight loss,color,surface morphology and ascorbic acid were found to be better than those of the two control groups(P<0.05).Furthermore,no significant changes were observed in pH values,the content of total phenols,or 1,1-dipheny1-2-picrylhydrazyl radical scavenging capacity(P>0.05).It is indicated that PAW treatment is a promising methodfor improving microbiological safety and extending the shelf-life of kale.

Development of predictive models for egg freshness and shelf-life under different storage temperatures

The objective of the present study was to develop models for egg freshness and shelf-life predictions for the selected evaluation indicators including egg weight,Flaugh unit(HU),and albumen height.Experiments were carried out at different storage temperatures for a total period of 29-32 d.All data were collected and fitted in to Arrhenius equation for egg freshness,while the HU data were applied to a probability model for shelf-life prediction.The results showed that egg weight,albumen height,and HU decreased significantly,while albumen pH increased with the extension of storage time.The higher the storage temperature,the faster the egg quality decreased.In addition,the bias factor,accuracy factor,and the standard error of prediction were selected to verify the developed quality models.Maximum rescaled R-square statistic,the Hosmer-Lemeshow goodness-of-fit statistic,and the receiver operating characteristic curve were used to evaluate the goodness-of-fit of the developed probability model for the shelf-life of eggs,which indicated that the presented predictive models can be used to assess egg freshness and predict shelf-life during different storage temperatures.

Cumulative damage by nonthermal plasma exceeds the defense barrier of multiple antibiotic-resistant Staphylococcus aureus: a key to achieve complete inactivation

Objectives:The aim of this study was to provide a comprehensive understanding of the nonthermal plasma(NTP)-induced inactivated behaviors on a multiple antibiotic-resistant(MAR)Staphylococcus aureus(S.aureus).Materials and Methods:A dielectric barrier discharge(DBD)NTP system was employed for the inactivation of a MAR S.aureus under various applied powers of 35,45,and 55 W,and gas distances of 4,6,and 8 mm.The inactivation kinetics of S.aureus were estimated with linear and nonlinear predictive models.In addition,degradation of carotenoid pigment,peroxidation of fatty acids,oxidation of nucleic acids and proteins,and alteration in gene expression were analyzed after NTP treatment.Results and Discussion:The computationally simulated results indicated that the densities of various reactive species increased with enhanced applied powers and decreased discharge distances.These species were further transformed into reactive oxidative and nitrogen species in the gas-liquid interphase and liquid phase.The oxidative and nitrosative stress of NTP resulted in severe damage to cellular components and the morphological structure of S.aureus.On the other hand,the plasma reactive species could also induce the sublethal injury of S.aureus through upregulating the general stress response,antioxidative and antinitrosative defensive systems.Once the cumulative damages overrode the stress tolerance of S.aureus,the completed cell death was finally achieved by NTP.Conclusions:This work infers the possible risk of inducing the repair and resistant capacity of pathogens when the applied NTP parameters are inappropriate,which helps the optimization of NTP process to achieve sufficient inactivation.