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Evaluating antimicrobial efficacy of GS-2 on reusable food packaging materials
Title
Evaluating antimicrobial efficacy of GS-2 on reusable food packaging materials
Creator
Birje, Nupoor Prasad
Date
2024
Description
Packaging plays an important role in maintaining the quality and safety of fresh produce throughout storage, transportation and end-use by...
Show morePackaging plays an important role in maintaining the quality and safety of fresh produce throughout storage, transportation and end-use by consumers. Single-use packaging poses several environmental impacts; therefore use of reusable packaging is being encouraged in the fresh produce supply chain. However, the utilization of harmful chemicals and inadequate sanitation standards limit the reuse of packaging materials. To overcome these limitations, this study focuses on testing a non-toxic, water-soluble antimicrobial; GS-2 coating to facilitate the reuse of food packaging and reduce the risk of microbial contamination. In this study, the antimicrobial activity of GS-2 was evaluated against foodborne pathogens; Escherichia coli, Listeria monocytogenes and Salmonella enterica on plastic and cardboard coupons at 1 h and 15 min treatment times and 0.3%, 1% and 3% concentration. These coupons were also stored at 4℃ and 90% R.H. and 18℃ and 45% R.H. inoculated on different days up to 42 d with E. coli or L. monocytogenes to study retention of activity of GS-2. Additionally, the efficacy of GS-2 to reduce transfer of bacteria from cardboard and plastic to tomato was investigated. The initial level of inoculum was 9 log CFU/surface for all experiments. Cardboard and plastic without GS-2 were used to compare the reduction of bacteria on the treated surfaces. The differences in the population of bacteria were evaluated using Student’s T-Test and ANOVA; p <0.05 was considered significant. With 3% GS-2 concentration on plastic, there was > 4.50 log CFU/surface reduction of all three bacteria in 1 h. There was a lower reduction of the population on cardboard as compared to plastic for all bacteria, the reduction obtained was 1.83, 2.65 and 3.42 log CFU/surface for E. coli, L. monocytogenes and S. enterica, respectively, in 1 h. There was no significant difference between 15 min and 1 h treatments for cardboard. Further, the highest reduction of bacteria was obtained with 3% GS-2 on plastic. For cardboard, no significant difference in population reduction was obtained for E. coli or S. enterica, with 1% or 3% GS-2. However, for L. monocytogenes there was a higher reduction with 3%. GS-2 remained active on the surface of plastic and cardboard for a period of six weeks. For cardboard, there was a lower reduction of bacteria and there was no trend in the population reduction from 0 to 42 d, with the populations remaining within a range of 4-5 log CFU/surface. There was a significant transfer of E. coli or L. monocytogenes from plastic surfaces without GS-2 to tomato at 5-6 log CFU/tomato. However, the transfer of bacteria from the GS-2-coated plastic to the tomato was below the limit of enumeration. For cardboard, the population was below the limit of enumeration, irrespective of the GS-2 coating. Based on the results, GS-2 is a promising antimicrobial that reduces the microbial load on packaging surfaces and prevents cross-contamination of fresh produce. The retention of GS-2 activity makes it suitable for reusable packaging applications.
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Efficacy and Mechanisms of Power Ultrasound-Based Hurdle Technology for Reduction of Pathogens in Fresh Produce
Title
Efficacy and Mechanisms of Power Ultrasound-Based Hurdle Technology for Reduction of Pathogens in Fresh Produce
Creator
Zhou, Xinyi
Date
2023
Description
Minimally processed produce is frequently contaminated with foodborne bacterial pathogens. Power ultrasound is a non-thermal and cost...
Show moreMinimally processed produce is frequently contaminated with foodborne bacterial pathogens. Power ultrasound is a non-thermal and cost-effective technology that can be combined with other chemical sanitization methods. This study investigated the reduction of Listeria monocytogenes and Salmonella Newport on grape tomato, romaine lettuce, and spinach washed with water, chlorine, or peroxyacetic acid alone or in combination with 25 or 40 kHz power ultrasound for 1, 2, or 5 min. Produce items were inoculated with selected pathogens at approximately 10 log CFU/g, air dried for 2 h, and then treated. Combined treatment of ultrasound and sanitizers resulted in 1.44-3.99 log CFU/g reduction of L. monocytogenes and 1.35-3.62 log CFU/g reduction of S. Newport on washed produce items, with significantly higher reductions observed on grape tomato. Synergistic effects were achieved with the combined treatment of power ultrasound coupled with the chemical sanitizers when compared to the single treatments. An additional 0.48-1.40 log CFU/g reduction of S. Newport was obtained with the combined treatment on grape tomato. In general, no significant differences (p<0.05) were observed in pathogen reductions between the selected ultrasound frequencies, sanitizers, or treatment lengths. Results from this study suggest that incorporation of power ultrasound to current treatment can enhance bacterial pathogen reduction on fresh produce surface, but cannot completely eliminate bacterial pathogens. Transcriptomic study revealed significant (|Log2 fold change|<1 and false discovery rate < 0.05) transcriptional changes in L. monocytogenes LS810 in response to the 2 min power ultrasound treatment. The up-regulation of genes encoding TPI, LLO, and PTS indicates increased energy requirements, enhanced virulence, and demand for sugar sources in bacteria. On the other hand, the down-regulation of genes involved in cyclic dimeric GMP hydrolysis and transcriptional regulation suggests a modulation of intracellular signaling, cellular processes, and metabolisms to enhance survival and recovery. The GO and KEGG analysis demonstrated defense mechanisms against ultrasound stress more comprehensively. L. monocytogenes adjusts its metabolism, repairs cell membranes, and conserves energy for survival. These findings enhance our understanding of its adaptation to environmental stress. Results of this study can be used as a start point for optimizing the efficacy of ultrasound-based hurdle treatments for fresh produce disinfection.
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