Synergistic effects of organic acids and photodynamic treatment against foodborne pathogens | |
| Author | Guragain, Anushuya |
| Call Number | AIT Thesis no.FB-22-05 |
| Subject(s) | Organic acids Electrochemical sensors Foodborne diseases |
| Note | A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Food Engineering and Bioprocess Technology |
| Publisher | Asian Institute of Technology |
| Abstract | Physical or chemical treatment processes have their own limitations for being ineffective and inefficient when used individually and to overcome such limitations, exploration of combinational treatment has been growing recently. This research focuses on the exploration of combinational treatment of readily available organic acids (acetic acid, lactic acid, citric acid, and malic acid) with natural water-soluble photosensitizer Chlorophyllin magnesium sodium salt (Chl-Mg) in the presence of blue LED to obtain enhanced inactivation effect on two pathogenic microorganisms (E. coli and S. aureus) in suspension. With a constant irradiation rate (600W/m2 ) and variation in time of illumination, log CFU/ml was calculated. Within 15 min of illumination, combination of acid and Chl-Mg led to complete inactivation of S. aureus sample whereas individual treatment of organic acids led to only 2-2.5 log CFU/ml reduction. Similarly, 4-5 log reductions was obtained for E. coli sample after 30 min of illumination while individual acid treatment only had 1-2 log CFU/ml reduction. This result supports the research hypothesis regarding synergistic effects. Results showed no valuable effect of type of acid or acid-Chl-Mg combination on inactivation of microbial load however it was obtained that inactivation of microbial sample increases as the time prolongs. Microbial inactivation data were fitted into Weibull model where R 2 value ranging from 0.998-0.963 for different sets of S. aureus, and 0.999-0.906 for different sets of E. coli was obtained. Furthermore, mechanism behind the synergistic effect was validated by nucleic acid leakage assay and SEM images. SEM images showed distinct shriveled images of synergistic combination of AA, Chl-Mg, and blue LED associating to membrane damage as a possible mechanism behind synergy. Moreover, enhanced wash treatment was applied in fresh romaine lettuce leaf where synergistic combination led to a reduction in bacterial count from 6.28±0.08 log CFU/leaf to 3.10±0.08 log CFU/leaf for S. aureus in 15 min of exposure, and from 6.39±0.08 log CFU/leaf to 3.25±0.11 log CFU/leaf for E. coli in 30 min of exposure suggesting that combinational effect is efficient to apply in fresh fruits and vegetables. In conclusion, combinational treatment of organic acids and Chl-Mg along with LED illumination presents an effective and/or efficient approach to reduce microbial load. |
| Year | 2022 |
| Type | Thesis |
| School | School of Environment, Resources, and Development (SERD) |
| Department | Department of Food, Agriculture and Natural Resources (Former title: Department of Food Agriculture, and BioResources (DFAB)) |
| Academic Program/FoS | Food Engineering and Bioprocess Technology (FB) |
| Chairperson(s) | Loc Thai Nguyen |
| Examination Committee(s) | Anal, Anil Kumar;Datta, Avishek |
| Scholarship Donor(s) | Bangchak Petroleum Public Company Limited, Thailand;Asian Institute of Technology Scholarships |
| Degree | Thesis (M. Sc.) - Asian Institute of Technology, 2022 |