Browsing by Author "Kakani, Grihalakshmi"
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Item Interventions for ensuring food safety in mangoes during phytosanitary treatments(2009-05-15) Kakani, GrihalakshmiIncreased consumption combined with increasing risk to foodborne illnesses makes it necessary to identify potential sources of contamination in the food chain and apply intervention processes that prevent/minimize the risk of contamination. The current study investigated the effect of the decontamination treatments with chlorine and lactic acid on the survival of Salmonella on the rind and stem scar portions of inoculated mangoes. The presence of the pathogen in the treatment water, internalization and the effect of the treatments on the quality of the fruit were also determined. For scar (hydrothermal), a 3.0 log reduction was obtained for control and additional reductions of approximately 2.2 and 1.3 log cycles were obtained with lactic acid and chlorine respectively. Data indicates reduction in pathogen population in cooling for all the treatments except two (Control ? increase of 0.3 logs, LA-LA ? increase of 0.3 logs). A 0.5 log reduction was obtained for the control (initial - 4.4 log10 CFU/10 cm2) and additional reductions of approximately 1.7 and 1.3 log cycles were obtained for treatments with lactic acid and chlorine respectively during hydrothermal treatment on the rind. For cooling, lactic acid and chlorine gave an overall reduction of approximately 1.3 and 1.4 logs respectively compared to control. Although Salmonella was not detected in the core stem tissue by direct plating method for most of the samples, it was detected after the enrichment method. The pathogen was detected on the rind, stem scar and the stem tissue for most of the samples for as long as 12 days. Salmonella was detected in treatment water with and without sanitizers after dipping mangoes. Lactic acid was found to be more effective in reducing pathogen population compared to chlorine in all the treatment combinations; however, the sensory aspects (color and texture) of the fruit were compromised.Item Selected genomic and phenotypic responses of Salmonella serovars to chlorine, chlorine dioxide, and cetylpyridinium chloride(2012-07-11) Kakani, GrihalakshmiNon-typhoidal Salmonella enterica serovars continue to be the leading cause of foodborne illnesses in United States. Chlorine, chlorine related, and quaternary compounds are generally used for disinfecting carcasses and equipment in processing industries. The current study was aimed at understanding the inactivation kinetics of four Salmonella serovars to chlorine, chlorine dioxide and cetylpyridinium chloride (CPC). The transcriptomic responses to oxidative stress was investigated in stationary and log phase cells of S. Typhimurium. The study was also aimed at understanding the effect of the chemicals on the expression of virulence genes associated with the Salmonella Pathogenecity Island 1 (SPI1). The possible induction of the viable but nonculturable (VBNC) state in Salmonella due to CPC was also investigated. The inactivation parameters for each serovar and the chemical were estimated based on the Hom's model, ln (N/N0) = -k C^n T^m and it appeared that while disinfectant contact time was significant, biocide concentration in the overall disinfection was insignificant. This was true especially for chlorine and CPC with subtle differences observed between the serovars. The inactivation efficacy was, however, dependent on both concentration and the exposure time for chlorine dioxide. The highest degree of inactivation was obtained with chlorine followed by chlorine dioxide and CPC. Transcriptomic responses of S. Typhimurium revealed significant downregulation of several metabolic processes such as tricarboxylic acid cycle, oxidative phosphorylation, and amino acid biosynthesis in both log and stationary phase cells. Several stress related genes such as usp, rpoS and ompR were upregulated in the stationary phase cells. Majority of the virulence genes associated with the SPI1 were found to be downregulated for all the treatments. While treatment with chlorine and CPC caused downregulation of all the virulence genes, treatment with chlorine dioxide caused significant upregulation of few (hilC, invC, sipA and sipB) genes associated with the SPI1. Finally, the induction of VBNC state was not concluded as a result of treatment with CPC. However, significant percentage of cells (45 percent) with intact membrane was established based on the BacLight assayTM.