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Non-thermal food processing technologies have demonstrated potential to inactive pathogens in food systems while maintaining the nutritional and quality attributes of the food and achieving significant efficiency in energy consumption. Among various non-thermal technologies, UV based technologies have made a significant impact on decontamination of processing equipment, process waste water and packaging materials with annual sale of UV decontamination equipment nearing 1 billion dollars. Although UV technology has significant potential for reducing microbial load in food systems, particularly beverage products and fresh produce, its application has been limited due to challenges of low penetration depth of UV light in a food matrix (0.1- 1 cm depending upon nature of food matrix). This research proposal aims to address this significant limitation by evaluating the synergistic combination of novel, food-grade photosensitizers (fructose and gallic acid) and UV-C light (254 nm) to improve the microbial (bacterial and viral) inactivation rate in wash water and fresh produce. The underlying hypothesis of the proposed research is that photosensitizers dissolved in aqueous media will produce free radicals when exposed to UV-C (254 nm). These free radicals will act synergistically along with the UV light to enhance the rate of microbial inactivation in wash water and on surface and within fresh produce. This hypothesis is supported by the current literature, our previous studies and preliminary data that demonstrate that exposure of photosensitizers to UV light results in generation of oxidizing free radicals. Extensive prior work shows that microorganisms are susceptible to death by interaction with free radicals such as hydroxyl, acyl, peroxyl, hydroxyalkyl and superoxide radicals through diverse mechanisms such as damage to nucleic acid, proteins and lipids. In our preliminary study, we showed that fructose accelerated quenching of fluorescein, a free radical sensitive fluorescent dye, in presence of UV light (254 nm) indicating generation of free radicals. Prior studies show that these free radicals could be hydroxyalkyl, acyl, or peroxyl radicals. Another study showed that gallic acid exhibited strong antimicrobial activity exclusively in the presence of UV light, possibly through formation of oxidizing free radicals. Therefore, it is expected that generation of oxidizing free radicals coupled with antimicrobial action of UV itself will increase the rate of microbial inactivation compared to UV processing alone. The specific objectives of this proposed research are-Investigate free radicals generation from novel photosensitizers (fructose and gallic acid) upon exposure to UV light in aqueous solutions and a model 3-dimensional solid system evaluate efficacy of simultaneous action of photosensitizers and UV exposure on bacterial and viral inactivation in aqueous medium and fresh produce (surface and internalized)Measure the impact of proposed approach on quality of fresh produce
The overall goal of the proposed research is to investigate synergistic combination of novel, food-grade photosensitizers (fructose and gallic acid) and Ultraviolet light (UV) to improve the bacterial and viral inactivation rate in wash water and fresh produce. The underlying hypothesis of the proposed research is that photosensitizers dissolved in wash water will produce free radicals when exposed to UV (254 nm) light. These free radicals will act synergistically with the UV to enhance microbial inactivation rate. This hypothesis is based on literature and our prior studies. UV processing is an attractive technology for bacterial and viral inactivation. However, its limited depth of penetration and non-homogeneous treatment due to rough and contoured shape of produce has impeded its use in produce industry. Conventional chlorine and hydrogen peroxide based sanitizers used for washing produce have significant limitations such as limited microbial inactivation and ineffectiveness in destroying internalized bacteria and viruses. The proposed approach addresses these limitations. The specific objectives are- (1) Investigate the chemical nature of free radicals generated from UV exposure of fructose and gallic acid and determine the factors that impact their rate of generation, (2) Investigate the efficacy of proposed approach in inactivating bacteria and viruses in liquid medium, produce surface and internalized within produce using novel imaging based approaches and (3) identify the impact of proposed technology on quality of fresh produce. Successful development of this novel technology will lead to a cost effective method for improved sanitation of fresh produce with extended shelf-life.