Masters Theses

Date of Award

12-2020

Degree Type

Thesis

Degree Name

Master of Science

Major

Food Science

Major Professor

Mark Thomas Morgan

Committee Members

Jiajia Chen, Tao Wu

Abstract

Food safety is a concern for all individuals involved in the food supply chain. Besides controlling the food product itself to improve safety, washing and sanitizing surfaces and equipment are critical. Chlorine dioxide (ClO2) is a green-yellow gas, known as a strong antimicrobial agent against multiple pathogenic microorganisms and effective on biofilms. Plastics such as polypropylene (PP), polyester (PET), cast nylon, ultra-high-molecular-weight polyethylene (UHMWPE), polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF) and white Acetal; and elastomers like nitrile rubber (Buna-N), ethylene propylene diene monomer (EPDM), and fluoroelastomer (FKM) are widely used in food processing surfaces and equipment. However, few studies have been conducted to address the depletion of gas by materials that might be present during the decontamination procedure nor the change in mechanical properties of plastics and elastomers. The objective of this study was to develop a model to simulate ClO2 transport into stainless steel crevices during surface decontamination. Also, to determine the resistance to ClO2 gas for selected materials. The gas was circulated inside a closed chamber with three different volumes of deionized water (20, 40, and 60 mL), and 0 mL (control). The gas decay was monitored and recorded until the concentration dropped below the detection limit. A physics-based simulation model was developed using COMSOL and validated by previously reported results in the literature, and the data obtained at the first stage of this experiment. A mathematical model was proposed for analyzing the time needed for ClO2 gas to reach the bottom at any possible crevice during equipment surface decontamination, which is depth-dependent. Additionally, selected material were exposed to 3000 ppm [parts per million] for 7 days inside a chamber following ASTM International Standards. This investigation showed an increase in the reaction rate due to water presence at different water volume and exposure surface area. After 7 days’ exposure at 3000 ppm of ClO2 gas, none of the plastics nor elastomers selected showed a significance difference (p<0.05) in the hardness value. This can help the food processing industry in constructing an effective system and establishing optimum sanitizing treatment conditions.

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