Quality and Safety of Fresh-Cut Vegetables and Fruits

Non-Technical Summary:<br/>
Iowa State University is committed to the improvement of the quality, nutrition, and microbial stability of intact and fresh cut produce. Our four objectives will include 1) the development of novel sensory methods to improve the quality and flavor profile of fresh cut produce which will increase the culinary attributes of the products; 2) the development of novel strategies to improve the shelf life of fresh cut produce which will increase profitability to companies and improve the length that consumers can enjoy their fresh cut produce; 3) identify critical factors that can increase the food safety risk of microbial contamination; and 4)determine novel strategies to prevent and/or minimize unintentional and intentional contamination on intact and fresh cut produce. Together these four objectives will increase the knowledge about the relationship between phytochemical properties of the product and the quality and the nutritional components as well as the microbial interaction of human pathogens and the fresh cut produce. These research based projects will aid in the development of new guidance documents in regards to fresh cut produce sensory and nutritional analysis as well as good agricultural practices/good manufacturing practices (GAPs/GMPs). These research projects will change methodology currently being utilized by academia and the food industry and will aid in changes within the agricultural and processing practices within the food industry. Relevant information will be available to fresh-cut processors to assist them in making decisions on harvest maturity, processing procedures, handling and packaging conditions to best maintain fresh-cut product quality and safety. Availability of best-practice guidance and standardized methods for food safety risk assessments of fresh-cut product treatments will reduce the likelihood of food safety events by replacing ineffective food safety practices with science-based procedures. Food safety risk will be reduced through availability of new, more efficacious, strategies for controlling human pathogens. Researchers will have standard protocols for quantifying flavor-based shelf life and standard microbiological methods. This research will also aid in increasing the shelf life of fresh cut products, which will aid in the fight to increase the amount of fresh produce consumed by Americans. Consumers will benefit from increased availability of fresh-cut products with improved sensory quality and higher nutritional value through improvements in cultivars and more effective preparation and handling practices. Incidence of fresh-cut products at retail with insufficient shelf life for consumer satisfaction will decrease. Human health will be improved as a result of increased consumption of vegetables and fruits.
<P>
Approach:<br/>
1: Our team will conduct shelf life tests, consumer sensory panels and develop standard procedures for measuring the shelf life of fresh-cut products in terms of retention of acceptable flavor. Shelf life in terms of appearance, texture, nutritional value, and flavor will be compared and, specifically, interactions between volatile and non-volatile components of flavor will be determined. The chemical data for flavor compounds will be combined with sensory data to determine what type of aroma profile and sugar/acid ratios give the highest flavor quality (preference) or off-flavor (low preference) ratings for fresh-cut products. The outcomes of these projects will be new and/or improved standardized sensory methodology for fresh cut produce. Success with be measured by the amount of information gathered to aid to the body of knowledge.
<br/>2: Within this objective we will investigate improved processing and packaging strategies to better maintain fresh-cut product quality as compared to standard commercial practices. Quality evaluations to assess the effects of product selection, pre- and post-cutting treatments, packaging technologies, and changes during storage include physicochemical analyses and sensory evaluations. Physicochemical techniques will include mostly instrumental measurements of surface pH, phytonutrient levels, surface color, firmness, sugar and acid levels, aromatic volatile abundance, microbial loads, and dissolved solid/electrolyte contents. We will conduct experiments with the goal of improving the nutrition, quality, and shelf life of fresh cut produce.
<br/>3: We will evaluate the influence of inoculum production, method of application, rate of drying, potential for sub-lethal injury on quantitative and qualitative recovery of pathogens, duration and condition of storage, biofilm development, and method of viable recovery. New approaches for selective concentration of target pathogens from fresh produce or processing effluents will be developed, including exploration of alternative binders for selective pathogen capture and pre- sample preparation will be developed. Different vectors for contamination of the intact and fresh-cut produce will be evaluated to determine transfer rates and potential risk. Expected outcomes include novel methods for detection of human pathogens on intact or fresh cut produce along with an increased data set for risk based modeling.
<br/>4: We will test novel intervention strategies and compare to standard commercial practices. Common chemical sanitizers will be combined with surfactants and other treatments (hurdle technology). Novel chemical approaches, including potentially synergistic systems containing mixtures of functional food ingredients and natural antimicrobials, will be evaluated for the control of human bacterial pathogens on intact fresh produce. Expected outcomes include methods for controlling unintentional and intentional contamination on the produces as well as strategies to prevent or minimize the potential for contamination.
<P>
Progress:<br/>
2012/01 TO 2012/12<br/>
OUTPUTS: Our team completed a combination of research and extension workshops and activities in 2012 to account for our time. Drs. Shaw and Mendonca completed a survivability study with strawberries and romaine lettuce in the summer of 2012. Within this study, five strains on Escherichia coli non-O157:H7 (O26, O103, O111, O121 and O145) were evaluated for their ability to survive during post-harvest storage. It was discovered during this experiment that there were significant strain difference over the 6 day shelf life study with growth of between 1-4 log cycles depending on the produce type and strain. This study has led to a follow up study that will be completed within 2013. Drs. Shaw and Mendonca also completed a series of studies with wheat grass and the wheat grass juice products for a local grower. The goal for the grower was to determine if there was a post juicing method that could be used to deliver a 5 log Listeria reduction required for bottling. Although this is on-going series of projects with additional ingredient supplements and processes being tested, our preliminary results indicate that the wheat grass and the juice are an excellent media for growth of spoilage organisms and foodborne pathogens when present. Dr. Shaw's lab completed a series of strawberry experiments in 2012. Her lab evaluated the influence of hand hygiene on post-harvest handling along with the survivability of E.coli during the pre-harvest growing. It was concluded during her studies that E.coli O157:H7 has the ability to be transferred from contaminated hands to at least 100 strawberries during normal picking and that the transfer of bacteria can be observed as far as 50 feet from the edge of a field. Another observation was that the workers have the potential to transfer the bacteria onto their clothing and skin during the harvesting process. Within the survivability portion of the project, E.coli was able to survive in the soil, on the leaves, and on the fruit from impact to harvest but the greatest survivability on the strawberry fruit occurred when water contamination happened within the last month of growing. In addition to performing research, Drs. Shaw and Wilson were active with extension and outreach to provide guidance to growers on Good Agricultural Best Practices (GAP). Dr. Shaw and colleagues provided five full-day GAP training courses to growers throughout the state which impacted 113 different farms. Another extension and outreach activity occurred in the summer of 2012 where Drs. Wilson and Shaw travelled to The Ohio State University to participate within a Leafy Greens safety short course hosted by Drs. Gonul Kaletunc and Sudir Sastry. During this training both extensions specialist and growers learned about concerns related to leafy greens and some of the most recent research out of The Ohio State University. A follow-up planning meeting occurred in the fall of 2012 at Iowa State University in which representatives from Iowa State University, The Ohio State University, and New Mexico State University met to discuss their most recent research projects and plans for future collaboration efforts.
<br/>PARTICIPANTS: Dr. Angela Shaw, Principal investigator on survival of non-O157 STEC on strawberries and lettuce (Co-PI's Dr. Aubrey Mendonca). Dr. Angela Shaw, Principal investigator wheat grass surveillance (Co-PI's Dr. Aubrey Mendonca). Dr. Angela Shaw, Principal investigator on Cross contamination of E.coli O157:H7 from handler's hands to strawberries during collection and survivability during growth (Co-PI's Gail Nonnecke). Dr. Angela Shaw, Principal investigator on GAP training (Co-PI Drs. Lester Wilson, Cathy Strohbehn, Paul Domoto, Teresa Wiemerslage and Margaret Smith, Value Added Agriculture, Iowa State University). Drs. Sudir Sastry (Ohio State, PI), Lester Wilson (Iowa State, Co-PI), Aubrey Mendonca (Iowa State, Co-PI), Byron Brehm-Stecher (Iowa State), Gonul Kaletunc (Ohio State), Jeanne Gleason (New Mexico State), Amy Smith Muise (New Mexico State University) on The Physics of Leafy Greens Additional train the trainer activities were provided to Extension and Outreach personnel and local grower organizations to learn more about food safety concerns on farm (228 were in attendance of various webinars and workshops)
<br/>TARGET AUDIENCES: Growers, packers, and processors of fruits and vegetables, extension and outreach specialists, academia, federal food agencies, and consumers.
<br/>PROJECT MODIFICATIONS: No major project modifications in 2012.
<P>
IMPACT: With over 230 farmers markets and 150 registered vegetable growers in Iowa, growers of fruits and vegetables are in need of new food safety intervention strategies and education to ensure the safety of their products. The research experiments completed on strawberries, lettuce, wheatgrass and wheatgrass juice all provided information to fill in gaps within knowledge of foodborne bacteria. Additionally, these studies have highlighted the critical areas with the growing process that can reduce the prevalence of foodborne bacteria thus reducing consumer risk. The Good Agricultural Best Practice workshops reached over 100 growers and educators throughout the state of Iowa. These workshops increased the knowledge required for decision-making, while providing practical suggestions for good agricultural best practices. Educating our farmers about farm management options that impact the risk of a foodborne outbreak is critical for our programing.