9:00 am - 10:00 am
Event details: A graduate exam seminar is a presentation of the student’s final research project for their degree.
This is an ALES PhD Final Exam Seminar by Barun Yadav. This seminar is open to the general public to attend.
Thesis Topic:
Application of Atmospheric Cold Plasma to Improve Microbial Safety of Meat Products
Public Seminar:
https://ualberta-ca.zoom.us/j/97156604872?pwd=azBidWF1c0srSjZvQ21PUTZkSU5xQT09
Meeting ID: 971 5660 4872
Passcode: 994175
PhD with Dr. Roopesh Syamaladevi
Seminar Abstract:
Meat products, including ready-to-eat (RTE) ham, fresh poultry meat, and dry pet foods have been associated with several foodborne outbreaks and recalls, due to the occurrence of microbial pathogens such as Listeria monocytogenes and Salmonella Typhimurium. Elimination of these microbial pathogens on meat products is a challenging task. Atmospherics cold plasma (ACP) is a novel non-thermal technology, that has attracted attention as an effective decontamination technique. The overall objective of this research was to evaluate the microbial inactivation efficacy of ACP for improving the high and low water activity (aw) meat product safety, when it is integrated with other selected methods, and to study the influence of important product and process parameters on the inactivation efficacy of such integrated treatments.
In the first study, irrespective of the product ingredients, ACP treatment showed significant antibacterial effects in a short exposure time against L. innocua on the ham surface. In the second study, ACP treatment was integrated with modified atmospheric packaging to achieve a higher antimicrobial efficacy, and the ham was formulated with preservatives and bacteriocins. The in-package gas composition had a significant influence on the antimicrobial efficacy of ACP. During 7 days of post-ACP treatment storage, the cell counts of L. monocytogenes were reduced to below the detection limit. This study suggested that post-ACP treatment storage time was an important parameter to achieve higher inactivation efficacy. The underlying inactivation mechanisms were investigated in the third study, which revealed that L. monocytogenes cells were under high oxidative stress conditions with permeabilized membranes during post-ACP treatment storage. After 7 days of post-ACP treatment storage, a high percentage of cells lost their esterase activity and membrane integrity. During long-term post-treatment storage, cell membrane permeabilization was one of the major causes of the loss of cell culturability.
The potential applicability of in-package ACP treatment to inactivate Salmonella in low aw pet foods was evaluated in the fourth study. The antimicrobial efficacy of ACP treatment against S. Typhimurium in low aw freeze-dried pet foods was affected by bacterial growth condition, microbial load, treatment time, post-ACP treatment storage time, and aw, with some key interactive effects between these parameters. The extended post-ACP treatment storage reduced the S. Typhimurium cell counts below the detection limit in 0.54 aw pet foods. The final study focused on developing an integrated process, using sequential treatment of selected organic acids and ACP to reduce S. Typhimurium in fresh poultry meat. The sequential treatment of organic acids [lactic acid (LA) or gallic acid (GA)] followed by ACP led to significantly enhanced and rapid inactivation of S. Typhimurium. The probable mechanisms associated with the inactivation of S. Typhimurium were due to the synergistically enhanced cell membrane permeabilization and membrane lipid oxidation. In addition, the sequential treatment of LA or GA with ACP significantly reduced the cell metabolic activity and affected the intracellular reactive oxygen species level of S. Typhimurium. The significantly greater inactivation of S. Typhimurium on poultry meat surface by the sequential combination of organic acids and ACP treatments compared to individual treatments demonstrated the potential application of this method to improve the microbial safety of fresh poultry meat. An ACP integrated organic acid misting and cooling process was designed to evaluate the simultaneous cooling and decontamination efficacy of this process for fresh meat.
This research shows the inactivation efficacy of the ACP integrated processes against foodborne pathogens in high and low aw meat products. The knowledge gained in this research would help in further research and in development of ACP integrated processes for industrial application.
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