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The ultimate goals of this study are to develop methods and procedures for improving the quality and safety of fresh-cut fruits and vegetables. To achieve this, studies will be conducted to understand factors that affect safety and quality and how to manipulate these factors to enhance both safety and quality of fresh and fresh-cut produce. <P>Objectives: 1. Evaluate methods of sampling and measuring flavor and nutrition of fresh-cut products to facilitate comparison to traditional shelf life factors. 2. Develop new strategies to improve and better maintain inherent fresh-cut product quality and nutrition. 3. Improve understanding of physiological mechanisms that affect fresh-cut product quality. 4. Determine critical factors in controlled inoculation studies with human pathogens and surrogates that influence the outcome of quantitative microbial risk assessments. 5. Evaluate and control unintentional and intentional microbial contamination of intact and fresh-cut produce. <P>Expected outputs include peer-reviewed publications, databases for use in risk assessments and recommendations for the fresh-cut industry about implementing best practices and decontamination methods.
Non-Technical Summary:<br/>
This project is focused on developing procedures for enhancing the safety and quality of fresh-cut fruits and vegetables. Quality is being addressed by understanding factors that affect metabolic processes in various products, that lead to changes enhancing nutrient contents as well as color, firmness and other quality attributes. Safety is being addressed by conducting pathogen surveys that will provide data for risk assessments, understanding factors affecting the ability of pathogens to colonize the surface of fruits and vegetables, and developing methods for reducing bacterial pathogens if present in fresh-cut products. To date, we have been exploring the concept of using different levels of stress to maintain quality while enhancing the nutraceutical content of fresh cut products. At the present time we have proven this concept in association with irradiation and other stressors. A model mechanism was described by which wounding stress triggers the biosynthesis of phenolic compounds. This information has been published in a peer-reviewed journal. We showed that reactive oxygen species (ROS) plays a role of secondary signal activating the phenylpropanoid metabolism in a wounded carrot model system. Applying an additional stress such as hyperoxia, increased the response even more by increasing the pool of ROS. In this mechanism model we proposed that ATPs play the key role of primary signal due to wounding stress. Studies on produce safety have indicated that product colonization by bacterial pathogens is affected by physicochemical characteristics of the product surfaces.
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Approach:<br/>
For quality studies: Use different levels of stress as factors affecting the quality of fresh-cut produce. Proximal analysis and specific nutrient composition are conducted separately on selected products of greatest impact in nutrition and greater consumption rates. Physiological role of reactive oxygen in the plant metabolism is a main focus in this investigation. For food safety studies: Surveys of Salmonella and Shiga-toxin Escherichia coli (STEC) in produce are a major focus of this investigation. These surveys involve validation of methods and studies for improving recovery of the pathogens. These surveys should allow gathering o data to support risk assessment. Developing methods for reducing pathogens in fresh and fresh-cut fruits and vegetables involves irradiation of fresh-cut melons, tomatoes and spinach as well as nuts. Other methods under study include chemical sanitizers and hot water/steam. Methodological factors affecting the outcome of these studies are a part of the study to determine the accuracy of challenge studies and therefore their usefulness in the industry. To understand how these decontamination methods operate and being able to improve their efficacy, studies on interactions between pathogens and the surface of these products are under conduction.
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Progress:<br/>
2012/01 TO 2012/12<br/>
OUTPUTS: A tomato packing operation was tested in two consecutive years. For each visit, sampling was conducted on 3 processing days. For each sampling, 20 samples of tomato were collected at 15 minutes interval during work hour at the plant. Each set of sample contains 4 processed tomatoes that were aseptically collected on the conveyor prior to packaging. These tomato samples were rinsed with 250 ml of Universal pre-enrichment broth, shaking and massaging inside a sterile plastic bag for 2 min. These tomato rinse samples were then allowed to stand in the rinse liquid inside the bag at room temperature for 60 minutes. Also, 100 liter of wash water was collected from the tomato wash tank at the end of each shift. This volume was separated in 4 25-liter subsamples and each subsample was sampled by filtering it through a Modified Moore's Swab (MMS) with peristaltic pump. At the end of the sampling, all the MMS were harvested placed in sterile polyethylene bags. All samples were packed in refrigerated containers and shipped to the laboratory in College Station, TX for testing for the presence of Salmonella on both types of samples, and also for E. coli as a fecal indicator for the tomato samples. No Salmonella or E. coli was found in any of the 144 tomato samples or the 600 liters of tomato wash water. The activities resulting form this project included visiting foreign tomato producing facilities and collaborating with scientists from Colorado State University and the University of Guadalajara in Mexico. These results were disseminated as a form of a Thesis and are being prepared for publication in a scientific journal.
<br/>PARTICIPANTS: Alejandro Castillo (Project Director), Ayoola Onafowokan, Mariana Villarreal and Zahra Mohammed (graduate students).
<br/>TARGET AUDIENCES: Nothing significant to report during this reporting period.
<br/>PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
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IMPACT: A graduate student obtained his Master's degree.