The effect of atmospheric cold plasma processing on microbial and organoleptic properties of Mazafati dates

Microbial contamination of date fruit, as one of the important and strategic agricultural products of Iran, is one of the important causes of waste of this product. Therefore, in this research, the effect of cold plasma as one of the new technologies for maintaining the quality and durability of Mazafati date using a sliding rotary arc discharge device, in two treatments of plasma application time in 5 levels (30, 60, 120, 180, and 240 s), with the aim of achieving the optimal time and different gases at 3 levels (air, argon and oxygen), with the aim of determining the best type of gas, was investigated. Microbial load evaluation by microbial counting method on 0, 3, 6 and 9 days after plasma treatment were performed. Sensory evaluation of date samples was performed after 9 days of plasma treatment by 5-point hedonic method. The results of microbial analysis showed a reduction of 0.48 logarithmic cycles of aerobic mesophilic bacteria in air-plasma samples and also a reduction of 0.35 logarithmic cycles of aerobic mesophilic bacteria in oxygen-plasma samples compared to the control sample. The lowest mean growth of aerobic mesophilic bacteria was observed in the sample with plasma treated time of 240 s. Plasma treatment with arc discharge device significantly reduced the microbial load, so air and oxygen with duration of plasma treatment of 240 s had the highest effect in reducing the total count of aerobic mesophilic bacteria. Also, storage time had a significant effect on microbial load and the total number of aerobic mesophilic bacteria on the last day of storage was significantly (p <0.05) higher than other days. Sensory evaluation also showed a significant difference between the sensory characteristics of plasma-treated samples and the control sample. Based on the scores of the evaluators, plasma-treated samples with air in the characteristics of flavor, texture, color and overall acceptance had 59, 45, 8 and 39% more scores than the control sample, respectively, which indicates the effectiveness of the plasma-treatment method in maintaining the quality of Mazafati dates.