Mitigation of cross contamination of E.coli TVS 353 using PAW during washing of baby spinach leaves.
Creators: name: Gurav, Yogini Sunil
Publisher: name: No Publisher Supplied
Year: 2024

description: Non thermal plasma is an emerging technology with potential application in microbial decontamination of fresh produce. In this study the mitigation of cross contamination between a spinach leaf contaminated by E. coli TVS 353 and uncontaminated leaves during washing using plasma activated water (PAW) was investigated. The specific objectives of the research were as follows: i.To evaluate the effectiveness of PAW against E. coli TVS 353 in a planktonic system.ii.To study the effectiveness of PAW for a single spinach leaf and a synthetic leaf, spot inoculated with E. coli TVS 353.iii.To investigate the efficacy of PAW in mitigating cross contamination during washing of baby spinach leaves. The PAW was generated by exposing sterile distilled water to the atmospheric pressure plasma jet and was characterized in terms of pH and electrical conductivity. In the planktonic system study, 0.1 mL of the initial inoculum containing 10.28 CFU/ml was added in 500 mL of PAW. Maximum reduction of 1.8 ±0.10 log CFU/ml was observed after 20 min suggesting that some inactivation of E. coli TVS 353 is possible due to the reactive species found in the plasma activated water.When a single leaf inoculated at 9.20 CFU/leaf was immersed in 500 mL of PAW and agitated for 20 min, it resulted in microbial recovery of 4.26 ± 0.03 log CFU/leaf from the synthetic and 4.94 ± 0.60 log CFU/leaf from real baby spinach leaf. Overall, the inactivation of the micro-organism was more difficult in a real baby spinach leaf compared to a synthetic leaf as the synthetic leaf lacked the biological structure and texture of a real spinach leaf. The cross-contamination study involved one inoculated real baby spinach leaf having 9.35 log CFU/leaf and ten baby spinach leaves. After agitation all eleven leaves in PAW for 10 min, bacterial recovery from the inoculated leaf was 4.30 ± 0.15 log CFU/leaf and uninoculated leaves the maximum bacterial recovery was 3.09 ±0.54 log CFU/leaf on average. After increasing the exposure time to 20 min, after agitation in PAW, the bacterial recovery from the inoculated leaf was 4.07 ±0.28 log CFU/leaf whereas from the uninoculated leaves the maximum bacterial recovery was 4.17 ± 0.19 log CFU/leaf on average. When agitation was done in sterile distilled water (SDW) for 10 min, the microbial recovery from the inoculated leaf was 6.37 ±0.07 log CFU/leaf and from the uninoculated leaves were 4.14 ±0.14 log CFU/leaf on average. After increasing the exposure time to 20 min, the microbial recovery from the inoculated leaf was 5.92± 0.55 CFU/leaf and from the uninoculated leaves was 4.48 ±0.54 log CFU/leaf on average. Based on these results, PAW was more effective in inactivating and reducing the bacterial transfer compared to the SDW, thus reducing the cross contamination. But when comparing the results for exposure time of 10 min and 20 min for PAW treatment, the cross contamination in uninoculated leaf was reduced substantially to 3.09 log CFU/ml average leaf whereas for 20 min the uninoculated leaf had a recovery of 4.17 log CFU/ml average leaf, suggesting that at higher exposure time (20 min) microbes were either reattaching or were difficult to inactivate.