低温等离子体活化水与介质阻挡放电联合处理对草莓冷杀菌效果及品质的影响

草莓采后微生物污染目前已成为物流过程中安全品质控制的研究热点，本研究以菌落总数为响应值，在等离子体活化水（plasma activated water，PAW）制备时间、水杨酸浓度、浸泡时间，介质阻挡放电（dielectric barrier discharge，DBD）低温等离子体工作电压、处理时间和工作频率的单因素试验基础上，采用Plackett-Burman试验筛选出对草莓菌落总数影响高度显著的因素，并通过Box-Behnken试验探究PAW及DBD联合处理对草莓冷杀菌效果及感官品质的影响。结果表明：草莓表面菌落总数随PAW制备时间的延长及水杨酸浓度的增大呈先减少后趋于平缓的趋势；随DBD工作电压的增大及处理时间的延长呈逐渐减少的趋势，但超过60 kV或150 s时草莓出现褪色甚至表观破损；浸泡时间及DBD工作频率对菌落总数无显著影响（P＞0.05）；对草莓菌落总数影响高度显著的因素主次顺序为水杨酸浓度＞PAW制备时间＞DBD工作电压（P＜0.001），且水杨酸浓度和DBD工作电压的临界值均随PAW制备时间延长呈线性下降的趋势；回归优化结果为PAW制备时间96 s、水杨酸浓度1.1 mmol/L、DBD工作电压46 kV，此条件下草莓表面的菌落总数由3.64（lg（CFU/g））降至0.83（lg（CFU/g）），杀菌率达99.8%，在20 ℃贮藏8 d内明显抑制表面微生物生长，有效维持生鲜品质，延长保鲜期。

Effect of Combined Cold Plasma-Activated Water and Dielectric Barrier Discharge Treatment on the Sterilization and Quality of Strawberry

Postharvest microbial contamination of strawberries has become a topical issue for safety and quality control in the logistics process. In this study, the effect of combined cold plasma-activated water (PAW) and dielectric barrier discharge (DBD) treatment on the sterilization and quality of strawberries was explored. One-factor-at-a-time experiments were carried out to investigate the effect of PAW preparation time, salicylic acid concentration, and soaking time as well as DBD working voltage, time and frequency on the total bacterial count (TBC) on the surface of strawberries. The significant variables affecting the response variable were determined using Plackett-Burman (PB) design and were optimized using Box-Behnken design. Results showed that the TBC on the surface of strawberries decreased first and then leveled off with increasing PAW preparation time and salicylic acid concentration, while it continuously decreased with increasing DBD working voltage and time. Nevertheless, when DBD working voltage and time exceeded 60 kV and 150 s, respectively, the appearance of fruit color was faded and even damaged. Soaking time and working frequency had no significant effect on the TBC (P > 0.05). Besides, salicylic acid concentration, PAW preparation time and DBD working voltage were the significant variables affecting the TBC (P < 0.001), ranked in decreasing order of importance. The critical values of salicylic acid concentration and DBD working voltage both showed a linear downward trend with PAW preparation time. The optimum values of PAW preparation time, salicylic acid concentration and DBD working voltage were found to be 96 s, 1.1 mmol/L and 46 kV, respectively. Under these conditions, the TBC decreased from 3.64 (lg (CFU/g)) to 0.83 (lg (CFU/g)) and the sterilization rate was 99.8%. The combined treatment could obviously inhibit the growth of microorganisms at 20 ℃ for 8 days, effectively maintain the quality and extend the shelf life of strawberries .