Simultaneous Study of the Combined Effect of Gliding Arc Plasma and Zataria multiflora Essential Oil on Pathogens Inactivation and Quality Changes in Sliced Iranian White Cheese

Abstract

This study aimed to inactivate Escherichia coli O₁₁₁, Listeria monocytogenes, and Aspergillus flavus on sliced Iranian white cheese by using the combination of gliding arc nonthermal plasma (GAP) and Zataria multiflora essential oil (ZEO). The cheese samples were exposed to different levels of GAP (0, 2, and 5 min) and ZEO (0 and 100 ppm) and stored at 4°C for 60 days. The extraction yield of ZEO based on dry weight was 1.66%. Carvacrol (33.85%) was the most important compound in ZEO. During the storage period, E. coli and L. monocytogenes counts increased in all samples. However, the most effective inhibition of E. coli and L. monocytogenes was observed in samples treated with 100 ppm ZEO combined with 2 min of GAP, and 100 ppm ZEO combined with 5 min of GAP, respectively, resulting in increases of only 1.35 and 1.8 log CFU/g over the storage period. In terms of the growth inhibition percentage of A. flavus, the lowest inhibition was detected in the presence of essential oil alone, while the highest inhibitory effect resulted from 5 min of plasma treatment combined with essential oil. GAP treatment also reduced the pH value of the cheese while increasing thiobarbituric acid reactive substances (TBARS). The control sample showed the lowest pH and the highest TBARS during storage. The highest overall acceptance sensory properties score was observed in cheese samples treated with 2 min of GAP and 100 ppm ZEO. According to the results of microbial, chemical, and sensory tests, Iranian white cheese samples treated with 2 min of GAP and 100 ppm ZEO can be used as a novel technique for sterilization and extending the shelf life of white cheese.