OLD_S294: Postharvest Quality and Safety in Fresh-cut Vegetables and Fruits
(Multistate Research Project)
Status: Inactive/Terminating
OLD_S294: Postharvest Quality and Safety in Fresh-cut Vegetables and Fruits
Duration: 10/01/2005 to 09/30/2011
Administrative Advisor(s):
NIFA Reps:
Non-Technical Summary
Statement of Issues and Justification
Project's Primary Website is at http://postharvest.ucdavis.edu/S294/index.shtm
Consumption of fresh-cut produce has increased at an annual rate of approximately 10% since 1995 and the market for fresh-cut vegetables and fruits is estimated at $10-12 billion annually (IFPA, 2004). The International Fresh-cut Produce Association (IFPA) estimates that fresh-cut products currently make up more than 15% of all fresh produce marketed in the U.S. Postharvest losses of fresh-cut produce are difficult to estimate but given the highly perishable nature of fresh-cuts compared to intact produce, the retail value of fresh-cut produce losses may exceed $1 billion annually.
The appearance, convenience, and generally high nutritive value of fresh-cut vegetables and fruits are bringing about increased sales of fresh produce, but repeat sales of the fresh-cuts is dependent upon assurance of its safety and the products having pleasing texture and flavor. To date, the industry has relied on established technologies derived mainly from practical experience to maintain visual quality and shelf-life with less consideration of the quality characteristics that drive repeat sales such as good flavor retention, maintenance of an appealing texture (crispness, crunchiness), package labeling underscoring the high nutritive value of the product, and increased microbial quality leading to extended shelf stability and food safety. Through interaction with the IFPA we know that current technologies, especially for fresh-cut fruits, do not provide the shelf stability needed to supply long distance domestic markets.
Unfortunately, as produce consumption has increased in the U.S. in recent years, so has the number of produce-related outbreaks of foodborne illness (Beuchat, 2002; National Advisory Committee on Microbiological Criteria for Foods, 1999; Nguyen-the and Carlin, 2000). Produce-related outbreaks accounted for 6% of all reported foodborne outbreaks in the 1990s compared to only 0.7% in the 1970s (FDA, 2004, Sivapalasingam et al., 2004). The CDC reported that foodborne outbreaks associated with fresh produce doubled between the period 1973-87 and 1988-92 (Buck et al., 2003). The conditions on the cut surface of fresh-cut products, with the presence of water and compounds that microbes can use for nutrition, provide ideal conditions for growth, however, it is difficult to compare the results of studies on survival and growth of pathogens done in different laboratories because substantial variations exist in methods for inoculation, treatment, or storage, and in procedures used to detect, recover, or enumerate pathogens on raw produce. The continuing nature of such produce-related outbreaks represents a threat to further increases in per capita consumption due to lowered confidence in the microbial safety of the product by the consuming public. Such outbreaks can also be very costly to growers, processors, shippers and restaurants.
Integration of physiological, pathological, food safety, and instrumental and sensory quality measurement concepts is essential for developing the most effective handling procedures and innovative, new technologies for maintaining quality and shelf stability of fresh-cut products. Much experimental work will be needed to optimize and integrate new and emerging treatments in diverse fresh-cut products. This fact supports the proposed integrated approach of having parallel projects in different states and of focusing the research into specific areas of importance. Alternative and emerging technologies for maintaining the quality and shelf stability of fresh-cut produce are being introduced at a rate that often precludes thorough evaluation of instrumental and sensory quality attributes, and their impact on product nutritional value, microbial quality and food safety. To do so, a multidisciplinary approach as proposed herein also will be needed to optimize the new and emerging treatments.
Related, Current and Previous Work
As a result of physiological and microbial deterioration occurring during storage and marketing of fresh produce, and especially fresh-cut produce, there is an urgent need to develop effective, non-damaging treatments for maintaining the quality (appearance, flavor, texture, nutritional value) and food safety of fresh harvested produce (How, 1990). Most of the sales of fresh-cut produce have been in the vegetable (salad, carrot slice) area (Garrett, 2002) and current handling practices for fresh-cut vegetables have been described (Barth et al., 2002). More recent research and commercial interest is focusing on fresh-cut fruits and melons (Bai et al., 2003; 2004; Beaulieu et al., 2004; Beaulieu and Gorny, 2002; Bett-Garber et al., 2003; Saftner et al., 2003a,b; Soliva-Fortuny and Martin-Belloso, 2003). With over 200 different vegetable and fruit crops with potential for development as fresh-cut products, each with unique physiology and handling requirements, an integrated, scientific approach to research and development including microbiological interactions with these products is critically needed.
A search of the CRIS database revealed no other multistate projects or coordinating committees dealing with fresh-cut vegetables and fruits, and also none with plant physiologists, food scientists and microbiologists working together. The proposed multistate project is needed in order to provide coordination and collaboration among the scientists working in this field if duplication of effort is to be avoided and the available time and resources are to be effectively applied. In this way, more effective approaches that are more widely applicable to different fresh-cut products may be more quickly developed. This research broadly supports the goals of the Food Safety and Quality National Initiative. It also is in line with the current SAAESD Programmatic Plan approved in 2000 (http://www.cals.ncsu.edu:8050/saaesd/progplan.htm) in the areas of food safety, plant food processing systems, and functional foods.
Critical Review of Previous Project Accomplishments
This proposal is for a replacement project to S-294, Postharvest Quality and Safety in Fresh-cut Vegetables and Fruits. S-294 resulted in numerous collaborative activities including NRI, IFAFS and NIFSI grants with multistate collaboration. The project members developed information on preharvest and postharvest treatment and storage effects on the nutritional value of fresh-cut products; developed or evaluated new tools, treatments and cultivars to improve the quality and safety of fresh-cut vegetables and fruits; developed new information on the contamination and attachment of microbes to fresh-cut product as well as developing novel approaches to microbial control; and elucidated the physiological processes underlying both positive and negative quality changes associated with fresh-cut processing.
With this new project, we plan to move more strongly in the direction of standardization among the members of microbiological procedures and instrumental and subjective methods for sensory quality analysis. We have identified the newly emerging treatments and techniques for assuring fresh-cut quality that need to be tested and evaluated and applied to new fresh-cut products as replacements or supplements to existing procedures; similarly, we have identified physiological processes that may control many of the observed quality changes during storage of fresh-cut products. We see a need to develop standard protocols for evaluation of the efficacy of sanitizers and the appropriateness of experimental protocols for microbiological challenge studies with fresh-cut produce. Surrogate organisms for human pathogens are needed to allow larger scale evaluation of intervention treatments. New sanitizers and natural product antimicrobials and also physical treatments to control microbes have been identified for testing. Because of the potential for treatment interactions between vegetable and fruit tissues and microbes, we plan on close coordination between microbiologists and plant/food scientists in all of the above activities.
For a review of the literature related to fresh-cut product quality, technologies for maintaining quality and shelf stability, physiology of fresh-cut products, and microbiology and food Safety of fresh-cut products, see the attachment.
Objectives
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Develop, evaluate, and standardize subjective and objective quality evaluation methods in intact and fresh-cut vegetables and fruits.
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Develop new strategies to maintain fresh-cut product quality
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Improve understanding of biochemical, physiological and molecular mechanisms that affect fresh-cut product quality.
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Standardize methods for recovering pathogenic and spoilage microorganisms from intact and fresh-cut produce including tree nuts.
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Evaluate and control unintentional and intentional microbial contamination of intact and fresh-cut produce.
Methods
Objective 1: We propose to 1) compile existing methods used for sensory analysis and write guidelines for testing horticultural crops, 2) compare techniques for product profiling and difference testing, and 3) continue relating instrumental with sensory measurements by using newly developed instruments and statistical techniques. Quality rating scales were compiled as a first-step towards standardization of quality evaluation procedures (Kader and Cantwell, 2005). All S-294 participants will review the rating scales. Sensory evaluation methods and objective methods of measuring color, firmness, and composition will be proposed. These will be discussed, agreed-upon revisions made, and the procedures finalized and distributed within and outside the multistate project. The updated sensory analysis guide will be a collaborative effort between, and not exclusive to, participants from CA, FL, ARS-FL, ARS-LA, ARS-MD, ARS-PA, and BC. For comparison of techniques between laboratories, fresh-cut carrots will be shipped between CA ARS-FL, and ARS-PA and quantitative descriptive analysis, ranking, or discrimination analysis will be used, depending on respective resources. Additionally, different melon cultivars will be shipped between CA, ARS-FL, ARS-LA and ARS-PA. The same protocol for cutting the melons will be used, and comparison between laboratories made for descriptive analyses. The FL and ARS-FL laboratories will also compare sensory methods using the same raw materials. Quality evaluation comparing sensory data with physicochemical analysis will continue with novel instrumentation such as the SBSE (stir bar sorptive extraction) technology combined with olfactometry (ARS-FL), electronic nose technology (FL, ARS-FL); also, interactions between volatile and non-volatile components of flavor (ARS-FL). 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 orange juice, fresh-cut tomato and melon, or other tropical fruits/fruit products (ARS-FL, ARS-LA). Objective 2: We will evaluate MAP and new/emerging MAP-alternatives and the means to integrate these studies into a hurdle strategy to maintain the appearance, texture, flavor and nutritional quality of diverse fresh-cut products. Treatments also will be evaluated for their ability to maintain microbial quality and food safety. Proposed treatments may be done before and/or after fresh-cut processing. Fresh-cut apples, melons and other fruits will receive the most emphasis, but fresh-cut vegetable products, especially those related to or potentially related to the salad bar industry will also be tested. Fresh-cut produce that will be studied include cut apples/pears (AL, BC, ARS-FL, IA, LA, ARS-MD, MI, NY, OR, ARS-PA), melons (AL, CA, FL, IA, ARS-LA, ARS-MD, ARS-PA), subtropical and tropical fruits (CA, FL, ARS-FL, ARS-LA), cut lettuce and other leafy vegetables (AL, CA, IA, ARS-MD), tomatoes (CA, FL, ARS-FL, ARS-MD, ARS-PA, Spain), broccoli, carrots, cauliflower and other salad vegetables (CA, ARS-MD, MI, ARS-PA), and sweetcorn kernels (FL), and sweetpotato (LA). Selection of varieties with enhanced shelf stability and initial product quality will be based on reduced or delayed ripening (physiological, genetic) characteristics, greater resistance to plant pathogens and microbial contamination, better appearance and flavor, enhanced texture retention, and higher nutritional value. The work will be conducted in BC, ARS-FL, ARS-LA, ARS-MD, MI, and Spain. Fresh-cut fruit will be ripe or nearly ripe and vegetables will be fresh and showing no signs of senescence. Initial product quality including optimal fruit maturity, preconditioning, trait targeting, and microbial quality will be studied. Non-destructive instrumental measurements of vegetable and fruit quality will be conducted in CA, FL, ARS-FL, MI, OK, and Spain. Preharvest and pre-cutting 1-MCP treatments and pre-cutting heat treatments, ethanol, reduced O2 (0-2 kPa) and elevated CO2 (10-30 kPa) or O2 (40-100 kPa) atmospheres, hot water brushing, and new and emerging sanitizers will be tested. To develop basic information on the effects of cutting apparatus and blade designs of apple/pear corer/wedgers, the influence of cutting surface angles, forces required to make the cut, and blade edge characteristics will be evaluated. Evaluations will be benchmarked relative to quality and rates of deterioration after cutting. Proposed post-cutting treatments to slow physiological and pathologically induced deterioration of the fresh-cut products will include MAP, treatments with 1-MCP, natural products (antimicrobials, antioxidants, Ca-containing and GRAS substances), enhanced post-cutting washing/sanitizing steps, newer sanitizers such as ozone, electrolyzed water and organic acids, edible coatings (carboxymethylcellulose, chitosan, lecithin, etc.) with or without food additives, antimicrobials and preservatives, novel microbial antagonists that out compete pathogens, and non-chemical treatments such as high hydrostatic pressure, UV-C and ionizing irradiation. Pectinesterase application with and without calcium in order to firm the tissue by creating pectin crosslinking will be evaluated for its effect on fresh-cut fruit tissue softening and watersoaking development during storage. Rinsing the cut fruit with buffered alkaline solution will also be tested to determine if hyper-acidification of the cut surface due to vacuole rupture might play a role in the development of watersoaking and softening due to activation of hydrolases in the cell wall and membrane. Novel packaging technologies also will be studied to avoid tissue injury during storage and to maintain fresh-like quality for an extended duration. Post-cutting chemical and physical interventions will be integrated with MAP. Adverse effects on quality and nutrients induced by an intervention technology, and means to reduce or minimize the effects will be investigated. The effects of various pre- and post-cutting treatments on fresh-cut vegetable and fruit quality attributes including microbe levels is an area that will involve interaction between the physiologists and microbiologists in the project. Work in those areas described above will be conducted in AL, BC, CA, ARS-FL, FL, GA, IA, LA, ARS-LA, MI, ARS-MD, OR, PA, ARS-PA, and TX. Objective 3: Lettuce will be used as a model system by investigators in CA to characterize and identify the wound signal. Treatments will then be devised to perturb the signal so as to lessen its deleterious effects. Compounds known to signal the occurrence of injuries to non-injured tissue will be measured in different fresh-cut products. The respiratory response and recovery or re-equilibration of fresh-cut vegetables and fruits to wounding and to fluctuating temperatures will be investigated in FL and TX. Aerobic and anaerobic respiratory metabolism in fresh-cut tissues, including the basis for tolerances of fresh-cut vegetables and fruits to low O2 and elevated CO2 levels will be studied in MD and MI. The apparent lack of chilling injury symptom development in fresh-cut tropical and subtropical species in terms of more basic physiological responses of the tissues to chilling stress such as textural alterations and aroma volatile production will be investigated in more detail in AL, CA, FL, ARS-FL, and ARS-LA. Respiration (CO2 and O2) and fermentative volatiles (ethanol and acetaldehyde) will be measured using standard gas chromatographic (GC) techniques and respiratory metabolism by standard enzymological methods. Textural changes will be evaluated using mechanical measurements of tissue firmness as well as enzyme assay and compositional analysis of cell wall polymers according to Huber and ODonoghue (1993). Ethylene-dependent and ethylene-independent wound responses in fresh-cut lettuce and fruits will be investigated in CA and FL by utilizing inhibitors of ethylene binding such as 1-MCP. The role of membrane deterioration in terms of electrolyte efflux (FL) and analysis of lipoxygenase and phospholipase action (FL and ARS-MD) will also be investigated. The role of free radicals in fresh-cut product deterioration will be investigated in BC. Ethylene will be measured by standard GC technique. Several participants will investigate the physiological and biochemical causes of quality changes, especially undesirable color (browning) and textural changes. Activation and inactivation of key enzymes involved in color, texture, nutritional and flavor changes in fresh-cut products will be the focus of work in CA, ARS-LA and ARS-MD. Initial maturity and quality effects on subsequent quality changes in fresh-cut vegetables and fruits will be evaluated in CA, FL, and ARS-LA. Other participants will focus on understanding the biochemical pathways involved in softening (AL, CA, FL, ARS-MD, and OK) and browning (CA). The role of phospholipase activation upon wounding in limiting the shelf-life of fresh-cut fruits will be investigated in FL and ARS-MD. Sensory and instrumental measures of flavor quality will be correlated by project members in CA, ARS-FL, and ARS-LA. Since apparent responses to temperature, ethylene, etc. can be strongly affected by different fresh-cut preparation procedures, certain basic preparation procedures such as slicing procedures, slice or chunk sizes, and sanitation methods will need to be agreed upon, especially by those participants working with the same or similar types of products. Similarly, standard hedonic scoring systems and physical measurement methods for color and texture for each common product will be used as much as possible. Objective 4: The overall objective of this project will be to develop, using an inter-laboratory collaborative approach, a basic protocol for inoculation and recovery that could be modified according to various groups of fruits, vegetables, and tree nuts, but used in a standard way to test for the presence and/or populations of foodborne pathogens and for the effectiveness of sanitizers in killing these microorganisms. The method would be recommended as a standard protocol for use by USDA, FDA, EPA, and researchers to determine the efficacy of sanitizers in killing pathogens such as Escherichia coli O157:H7, Salmonella, and Listeria monocytogenes. Adoption of the method would facilitate comparison of the relative effectiveness of sanitizers for raw vegetables and fruits, regardless of the laboratory conducting the test. The basic protocol could also be used in challenge studies to determine survival and growth characteristics of pathogens on raw produce and tree nuts subjected to various processing and storage conditions. This work will be conducted by project members in CA, FL, GA, IA, ARS-MD, ARS-PA, and TX. The goals of the research to be performed under this objective are: 1. To develop a standard method(s) for inoculating the surface of fresh and fresh-cut vegetables and fruits, and tree nuts with bacteria capable of causing illness. 2. To determine the effects of time between inoculation and retrieval on viability and recoverability of foodborne pathogens. 3. To develop a standard method(s) for evaluating the effectiveness of sanitizers to remove or kill foodborne pathogenic bacteria on the surface of fresh and fresh-cut vegetables and fruits, and tree nuts. 4. To validate these methods in independent laboratories. Objective 5: Types of produce that will be evaluated initially include apples, lemons, lettuce, melons, mangoes, oranges, peppers, sprout seed, and tomatoes. A variety of intervention technologies will be tested alone and in combination. Common microbiological methods will be used for enumeration of native microbes and pathogens that survive the intervention treatments. Appropriate controls will be included in each experiment and experiments will be replicated at least two times. The attachment and survival traits of possible surrogates on produce will be compared to their respective pathogens in order to allow evaluation of intervention on a larger scale and in a safer environment (GA). The likelihood of unintentional or intentional contamination of produce via ice will be investigated by preparing crushed ice from inoculated water and applying to fresh-cut products (GA). The efficacy of treating produce with sanitizers in killing foodborne pathogens and/or their respective surrogates attached to the surfaces and within tissues of produce will also be evaluated (GA and TX). Possible intervention steps to reduce hazards posed by foodborne pathogens or microbial toxins would have emphasis on simple, economical methods (e.g., increased or modified washes and treatments with chlorine, chlorine dioxide, and/or ozone water treatment). Comparing the initial population levels to those that survive on the product after treatment will give a level of success. The fate of Clostridium botulinum neurotoxin on fresh and fresh-cut produce will be investigated (GA). Contamination of produce with botulinum toxin by terrorists is possible. Stability of the toxin on fresh foods has not been fully investigated. The stability of the toxin will be studied on a limited number of types of fresh and fresh-cut produce items. Produce will be spiked with the toxin and then levels over time determined using an AOAC approved ELISA method. Commodity tolerance at different maturity stages to hot water immersion over a range of temperatures and effects on pathogen populations will be determined (FL, ARS-PA). Whole produce (initially melons and tomatoes) will be inoculated with the appropriate pathogen of interest or its surrogate to give an initial microbial load of 106 CFU/gm or cm2 as previously described (Annous et al. 2004). The potential for reducing the transfer of microorganisms of interest from the peel to the flesh of produce during fresh-cut preparation will be evaluated by testing of fresh-cut pieces for pathogen contamination. The potential for injured cells of interest to grow following storage will be also evaluated after 1-21 days in storage by plating to selective and nonselective media. Subtracting populations enumerated on selective media from those on nonselective media gives an estimate of the number of injured cells present. The impact of hot water immersion on the produce quality will be evaluated using sensory evaluation such as taste panels and/or sophisticated chemical and flavor analyses. For sanitizing produce that cannot withstand hot water treatments, application of gaseous chlorine dioxide (ClO2) is an alternative. Recently, in initial experiments we demonstrated that reductions of e 5 log CFU/cm2 in Salmonella Poona populations on cantaloupe surfaces following ClO2 gas treatment (Annous and Fett, unpublished). Further studies will be conducted with whole cantaloupe melons, tomatoes, grapes, and other commodities including sprout seed (FL, ARS-PA). Whole produce (initially melons and tomatoes) will be inoculated as described above. Gas treatment will be conducted in specially designed fumigation chambers (recently designed and constructed at ARS-PA) for produce or sprout seeds. Various times of exposure and ClO2 gas concentrations will first be tested for the effect on produce sensory qualities and shelf-life. Exposure times and concentrations will be optimized at 4 or 20°C at varying relative humidities for reduction or elimination of pathogens on inoculated fresh produce. Chlorine dioxide gas will be generated on-site using different available generation technologies. Residual microbial populations will be enumerated as described above. The effect of ClO2 gas treatment on product quality will be evaluated by methods as described below. Organic acids, including acetic, lactic, proprionic, citric, malic, benzoic, and ascorbic acids, will be tested in IA, ARS-PA, and TX. Fresh-cut apple or bell pepper prepared as previously described (Liao and Sapers 2000, Liao and Cooke 2001) will be inoculated with a Salmonella cocktail mixture and washed once with pure water to remove the unattached bacteria. After varying lengths of storage, apple or bell pepper disks will be prepared and washed with varying concentrations of one or a combination of organic acids to determine efficacy. The organic acid(s) most effective in removing attached bacteria from fresh-cut pepper or apple disks will be applied in combination with another sanitizer (chlorine, ozone, hydrogen peroxide, or heat). Acid injured cells that survive the initial treatment with organic acid may be more susceptible to the secondary treatments leading to synergistic activity. The total number of viable and injured bacteria will be determined by plating the samples on non-selective media such as brain heart infusion agar and selective media such as XLT-4 agar. Antimicrobial activity of each organic acid at various concentrations against Salmonella cells in suspension or on apple or pepper disks will be determined by a method we previously described (Liao and Shollenberger 2003). Salmonella mutants resistant to acetic acid will be isolated using transposon mutagenesis. The effect of acid-tolerance on the attachment and survival of these mutants to apple or bell pepper disks will be determined. The disks containing acid-tolerant bacteria will be treated with acetic acid or other organic acid at the concentration lethal to the wild-type of Salmonella. The number of viable Salmonella remaining on the disk and the number of bacteria washed off in the acid solution will be enumerated to determine the efficiency of organic acid wash for removing Salmonella from the surfaces of fresh-cut apple or bell pepper slices A number of natural products with broad-spectrum antimicrobial activities, newer sanitizers such as ozone, electrolyzed water and organic acids, edible coatings with or without food additives and preservatives, novel microbial antagonists, and non-chemical treatments such as short-term, minimal exposure to high hydrostatic pressure, UV-C and ionizing irradiation will be tested for antimicrobial effects in conjunction with Objective 2 activities with interaction between the physiologists and microbiologists in the project (see above for participating locations). Application of antimicrobial compounds in conjunction with edible coatings will be done in ARS-FL. This will be done in a two-part study. First essential oils or phytoalexins with antimicrobial activity will be screened in vitro for effectiveness against common pathogens of citrus and tropical fruits. To test spoilage organism sensitivity to experimental treatments with essential oils or phytoalexins, methods traditionally employed will be initially used. Essential oil components such as thymol, carvacrol, trans-2-hexenal, citral, etc., known to have a broad spectrum of antimicrobial activity and also resveratrol and stilbene or their derivatives will be first tested on the target microorganisms. The specific organisms used for study will be those (primarily fungal) that are problematic on harvested subtropical/ tropical fruit. Diplodia natalensis, Colletotrichum gloeosporioides and Penicillium digitatum, have been recently isolated from diseased fruit to ensure virulence of the organisms as sub-culturing of fungi can cause a reduction in their pathogenic abilities. Methods to assist determining efficacy of the treatments are the agar diffusion method and the microdilution plate method. To evaluate the inhibitory effects of experimental solutions on organisms, the minimum inhibitory concentration (minimum level of experimental solution that produces an approximate 90% reduction in growth) and the minimum level of solution concentration which produces an approximate 99% reduction in populations will be measured (Ponce et al., 2003; Sparado et al., 2002; Wilson, 1997). Once the in vitro evaluation has been done, the second in vivo phase of the study with fruit will commence. Fresh-cut fruit will be treated by either spraying or dipping in a solution containing the natural compounds described above that were effective in inhibiting pathogen growth in vitro, or by incorporating the compound(s) into fruit coatings. The active material must be made available to the target organism by choosing the right solvent or carrier, and, at the same time, making sure it does not impart phytotoxicity to the commodity. To this end, the antimicrobial compounds will be tested without coatings on fresh-cut fruits for toxicity and then incorporated into different coating formulations to find optimum conditions wherein the coating is compatible with the essential oil or phytoalexin, but does not bind it to the extent it is no longer available to the fruit or the pathogen. Coatings will be initially chosen based on the solubility characteristics of the antimicrobial compound. In some cases it may be necessary to first dip or spray with the antimicrobial substance, then coat the fruit. It is to be expected that any successful antimicrobial action will be fairly specific for types of microorganisms inhibited. Therefore, much experimental work will be needed to optimize treatments for different microorganisms. Fresh-cuts will be assessed for % decay and size of lesions as well as % damage due to phytotoxicity. Details regarding the methods to be used are in the Attachments.Measurement of Progress and Results
Outputs
- The S-294 Technical Committee will issue annual project reports highlighting the results for the previous year, which will be made generally available on a website. As deemed appropriate, participants will submit research findings for publication in peer reviewed and nonrefereed journals and trade publications. A final report will be issued at the conclusion of the project.
Outcomes or Projected Impacts
- Results from this proposal will be available for use by fresh-cut growers and processors through the relationship between the S-294 project and the IFPA. The S-294 annual meeting has been held in conjunction with the IFPA convention since 1999. The results of this research will also contribute detailed scientific information relating physiology in diverse plant tissues to their quality and shelf stability and provide alternative strategies to the U.S. fresh-cut industry to control deterioration. These will be reported in refereed and other scientific journals. Improved appearance, taste and other quality characteristics combined with increased shelf-life will likely result in improved nutritional benefits to consumers and decreased postharvest losses to the U.S. fresh-cut industry.
- A compilation of quality rating scales (an update of the one by Kader and Cantwell, 2005), recommended compositional analysis methods, and a practical guide of sensory analysis for horticulturists will be completed and distributed to interested S-294 participants and fresh-cut produce industrys R&D and QA personnel. Other research projects will be more effective through the use of these new objective methods of quality assessment. Comparison of methods between laboratories will allow standardization of protocols to answer specific questions in future research, such as sample size and preparation for a sensory panel, and develop lexicons for descriptive analysis of fresh-cut products that may be used in future research. This project will contribute to a better understanding of the physical and chemical properties of fresh-cut products. Outcomes will include procedures for new fresh-cut products and extended shelf life with enhanced quality for existing products.
- Microbiology work in this project will result in the development of standard methods to determine survival and growth characteristics and test the efficacy of sanitizers to remove or kill bacterial pathogens on fresh and fresh-cut vegetables and fruits, and tree nuts. These methods, with minor variations, can then be widely used by researchers and regulatory agencies to determine the presence and numbers of Salmonella, E. coli O157:H7, and L. monocytogenes on produce and to demonstrate the effectiveness of sanitizers. The process for authorizing the use of safe, highly efficacious treatments to reduce the risk of infections associated with consuming potentially contaminated fresh-cut vegetables and fruits, and tree nuts can then more expeditiously proceed. Outcomes will include safer chemical and sustainable non-chemical strategies to reduce postharvest use of potentially hazardous chemicals to inhibit spoilage and decay that will benefit the environment and the consumer.
Milestones
(2005): Compile and circulate existing methods used for quality analysis of horticultural crops. Establish optimal quality criteria, preparation and storage procedures for fresh-cut processing for produce being studied at multiple project locations. Establish collaborative agreements between laboratories for comparison of sensory evaluation techniques. Determine whether different economically important fresh-cut vegetables and fruits utilize a common wound signal. Establish collaborative agreements between laboratories for development of a basic protocol for microbiological inoculation and recovery.(2007): Publish guidelines for fresh-cut product quality measurements. Compare techniques for product sensory quality profiling and difference testing. Identify the most useful pre-cutting treatments for maintaining fresh-cut product quality. Develop information on the physiological and biochemical causes of undesirable color (browning) and textural changes in order to identify remedial treatments. Develop standard method(s) for inoculating and recovering microbes on the surface of fresh and fresh-cut vegetables and fruits. Develop procedures for use of surrogate microorganisms for evaluation of large scale interventions.
(2008): Relate instrumental with subjective sensory quality measurements using newly developed (in 2006-07) instruments and statistical techniques. Identify the most useful post-cutting treatments for fresh-cut products from among MAP, 1-MCP, sanitizers and antimicrobials, antioxidants, Ca-containing compounds and edible coatings. Describe the respiratory response and recovery or re-equilibration of fresh-cut vegetables and fruits. Determine best method(s) for evaluating the effectiveness of sanitizers to remove or kill foodborne pathogenic bacteria on the surface of fresh and fresh-cut products.
(2009): Publish guidelines for fresh-cut product sensory evaluation techniques. Identify or develop novel packaging technologies to avoid tissue injury during storage and to maintain fresh-like quality for an extended duration. Identify ethylene-dependent and ethylene-independent wound responses in fresh-cut products. Determine if the apparent lack of chilling injury symptom development in fresh-cut tropical and subtropical species extends to textural alterations and aroma volatile production. Validate in independent laboratories methods for microbe inoculation and recovery for evaluating sanitizer effectiveness.
(2010): Delineate interactions between pre- and post-cutting treatments and packaging technologies and optimize fresh-cut processing and packaging procedures for selected products. Recommended a standard protocol for use by USDA, FDA, EPA, and researchers to determine the efficacy of sanitizers in killing microbial pathogens on produce.
Projected Participation
View Appendix E: ParticipationOutreach Plan
Results from the proposed research activities will be disseminated via presentations at scientific and industry meetings and conventions (especially the International Fresh-cut Produce Association), and will be published as project reports posted to the S-294 web site, as well as in peer-reviewed and nonrefereed (popular) publications. Participation by project members involved in undergraduate teaching, graduate student advisement, and extension activities associated with Land Grant Universities will promote the general dissemination of knowledge developed in the proposed project.
Organization/Governance
The offices of the Technical Committee will be the chair, vice-chair, secretary, and past-chair and will serve as the Executive Committee. The first three officers will be elected for two-year terms at the organizational meeting for the Technical Committee. Thereafter, a secretary will be elected biennially at the annual Technical Committee meeting. All voting members of the Technical Committee will be eligible for office. The officers will be promoted biennially in the following sequence: secretary to vice-chair, vice-chair to chair, chair to past-chair. These four officers will then constitute the Executive Committee to provide leadership and continuity and/or immediate action. The duties of the chair, vice-chair, and secretary will be as prescribed in the Guidelines for Multistate Research Activities; that of the past-chair will be to serve as a resource for the other committee members in carrying out their duties.
The project will have two subcommittees with chairs appointed by the Executive Committee chair. These will be the Quality and Physiology Subcommittee and the Microbiology Subcommittee. Members of each subcommittee will be those Technical Committee members whose research falls under the subcommittee area. The purpose of the subcommittees is to coordinate research activities within each research area, foster grant-writing activities, and create reports as directed by the Executive Committee.
Literature Cited
Abbott, J.A., Watada, A.E., Massie, D.R. 1984. Sensory and instrument measurement of apple texture. J. Amer. Soc. Hort. Sci. 109: 221-228.
Abe, K., Watada, A.E. 1991. Ethylene absorbent to maintain quality of lightly processed fruits and vegetables. J. Food Sci. 56: 1589-1592.
Abeles, F.B., Morgan, P.W., Saltveit, M.E. 1992. Ethylene in plant biology. 2nd ed. Academic Press, San Diego, CA USA.
Abreu, M., Beirao-da-Costa, S., Goncalves, E.M., Beirao-da-Costa, M.L., Moldao-Martins, M. 2003. Use of mild heat pre-treatments for quality retention of freshcut 'Rocha' pear. Postharvest Biol. Technol. 30: 153-160.
Annous, B.A., Burke, A., Sites, J.E. 2004. Surface pasteurization of whole fresh cantaloupes inoculated with Salmonella Poona or Escherichia coli. J. Food Prot. 67: 1876-1885.
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