Performing Department
AGNR-Nutrition and Food Scienc
Non Technical Summary
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.
Animal Health Component
0%
Research Effort Categories
Basic
50%
Applied
50%
Developmental
(N/A)
Goals / Objectives
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 systemEvaluate 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
Project Methods
Objective 1: Investigate generation of free radicals from fructose and gallic acid upon exposure to UV light in aqueous solutions and a model 3 dimensional solid systemUnderstanding the effect of various parameters in wash water such as pH, organic load, presence of metal ions and temperature on generation of free radicals by photosensitizers is critical for translation of optimal sanitation process conditions for fresh produce. This objective addresses following gaps in understanding-(1) what is the chemical nature of free radicals generated by fructose and gallic acid? (b) What factors influence the rate of generation of free radicals in these photosensitizers? and (c) What are the diffusion characteristics of these free radicals in a 3-dimensional matrix to accomplish inactivation of internalized microorganisms?This will be accomplished using a combination of fluorescence and EPR based techniques.Objective 2: Evaluate efficacy of simultaneous action of photosensitizers and UV exposure on bacterial and viral inactivation in aqueous medium and fresh produce.We will investigate synergistic effect of photosensitizers and UV exposure on bacterial and viral inactivation in liquid medium representing wash water and fresh produce. Innovations based on bioluminescence imaging and spectroscopy techniques will be used for rapid enumeration of microorganisms. We propose to use lettuce, basil and parsley as model produce systems. Rationale behind choosing these samples are- (a) These green vegetables and herbs are almost always consumed raw, (b) Basil and parsley are added as seasoning and therefore should not contain any residual off flavors or tastes (as might come from use of hypochlorite in washing) and (c) Significant surface area and delicate structure of leafy greens make removal of microorganism difficult with washing. To chieve this goal conventional microbial techniques such as plate counting and additional fluorescence based novel techniques developed in our lab will be used.Objective 3: Measure the impact of proposed approach on quality of fresh produceSince both UV and free radicals generate oxidative stress in food matrix, it is expected that such oxidative stress can affect product quality as well. This approach will evaluate the extent of impact of proposed approach on product quality. Such understanding will enable optimization of process.Produce will be exposed to their respective fructose concentrations and UV doses capable of accomplishing at least 5-log reduction of surface pathogens and or 3 log reductions in internalized microorganisms. After exposure, the change in these quality parameters of produce immediately after processing and during storage will be evaluated using a combination of chemical anlysis, texture analysis and sensory panel testing