Theses and Dissertations

Date of Award

7-2021

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Biochemistry and Molecular Biology

First Advisor

Dr. Veerachandra K. Yemmireddy

Second Advisor

Dr. Debasish Bandyopadhyay

Third Advisor

Dr. Daniele Provenzano

Abstract

Contamination of low-moisture foods (LMFs) with foodborne pathogens such as Salmonella and Shiga-toxin producing Escherichia coli (STEC) has been rising over the last couple of years. Commodity groups such as peanuts, tree nuts, and their products are frequently recalled when associated with illness outbreaks resulting from these pathogens. In this project, two major challenges related to understanding the survival kinetics of pathogens and the efficacy of novel antimicrobial treatments in mitigating their risk in LMFs were systematically investigated. Studies were conducted for determining the survival kinetics of three Salmonella spp. strains in three different tree nut flours (i.e., almond, chestnut, and hazelnut flours). The effect of storage relative humidity (RH): 25, 45, and 70% on the survival kinetics was determined over a period of 120 days at 21±2ºC. Results indicate that the type of tree nut flour and storage RH has a significant (P≤0.05) effect on survival. Salmonella survived better at lower RH (25 or 45%) compared to higher RH (70%) conditions. The effect of flour composition on the survival of Salmonella needs to be further investigated. In another study, the efficacy of UVC treatment in comparison to heat treatment to mitigate the risk of Salmonella and STEC was determined using peanut flour as a model food. Hot-water treatment resulted in a 3 to 4 log CFU/g reduction of tested pathogens. Raising the treatment temperature from 60 to 80°C and increasing the treatment time from 1 to 30 min increased the log reductions. UV-C treatment was found to be equally (if not more) efficacious in reducing pathogen CFUs. A reduction from 2 to 3 log CFU/g was observed after a 60 min treatment time. Weibull model best predicted the thermal death and UV inactivation kinetics of tested pathogens in peanut flour. Further studies should be focused on increasing the UV-C efficacy on par with heat treatment and determining the effect of these treatments on quality characteristics of tested LMFs.

Comments

Copyright 2021 Rajat Sharma. All Rights Reserved.

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