Application of cold plasma technology for reduction of pathogenic and spoilage bacteria in meat processing

Abstract

Cold plasma is categorized as a novel nonthermal technologies which is applied in food processing for microbial inactivation purpose. This research aims to study 1) the reduction efficacy of pathogenic and spoilage bacteria on pork and chicken meat with skin 2) the changes of pH-value, water activity and color when immersed in cold plasma in liquid form (liquid plasma) with 60 ppm H2O2 for 15 min at 25°C and compared with water immersion and control group. The artificial contaminated meat samples were inoculated with ca. 4.0 log CFU/ ml of Salmonella Enteritidis nalidixic acid resistant strain, Salmonella Typhimurium M6-S1CMU61/17, Campylobacter jejuni ATCC 33560, Campylobacter coli DMST 15190, Escherichia coli ATCC 25922, Staphylococcus aureus ATCC 25923 and Pseudomonas aeruginosa ATCC 27853. The mean±sd (log CFU/g) of reduction of S. Enteritidis, S. Typhimurium, E. coli, C. jejuni and C. coli on pork were 0.37±0.25, 0.08±0.19, 0.08±0.43, 1.03±0.99 and 0.72±0.71 on pork surface, respectively and the mean±sd (log CFU/g) of reduction of S. Enteritidis, S. Typhimurium, E. coli and C. jejuni on chicken meat were 1.11±0.52, 0.49±1.30, 0.72±0.80 and 1.39±1.10, respectively. The meat immersed in liquid plasma shows the significant reduction of C. jejuni and C. coli. However, after day 3 S. aureus in all groups were increased. Besides, the number of P. aeruginosa on day 10 was found overgrowth on meat. Results suggested that the liquid plasma could not inhibit bacterial growth on pork and chicken surfaces particularly with S. aureus after day 3 of this experimental condition. According to the pH-value of pork and chicken samples treated with liquid plasma when compared with control group in each time points were significantly different (P ≤ 0.05) which was downward trend similar to control and water groups. In addition, the water activity of pork in liquid plasma group significantly decreased, however, the water activity of chicken meat treated with liquid plasma was not significantly different in each time points compared with control and water groups. Likewise, a* (redness) and b* (yellowness) value (CIELAB) from pork and chicken samples were decrease. However, liquid plasma resulted in increased L* (lightness) value of pork sample but not significantly changed in chicken sample compared with control. This study demonstrates the efficacy of liquid plasma in the experimental condition could reduce pathogenic and spoilage bacteria on surface of pork and chicken samples within 3 days of storage under the refrigerator temperature (4 – 6 °C) with less effects on meat characteristics.