Improving and Maintaining Postharvest Attributes of Fresh Produce to Promote Consumer Consumption and Improved Health

<p>NON-TECHNICAL SUMMARY:<br/> Fruits and vegetables continue to respire and change, often in undesirable ways, after harvest. Fresh produce undergoes continuous physiological changes from two to 200 days, depending on the commodity. Despite aggressive changes in handling and storage practices, it is estimated that at least 20% of fresh produce never reaches consumers in the U.S. This figure can be as high as 80% in parts of the world where only minimal refrigeration and transportation systems are in place. U.S. consumers are encouraged to eat 5 to 10 servings of fruits and vegetables each day, yet the average intake is closer to 3 servings daily. There are a number of chronic diseases shown to be directly affected by diet, and the importance of fruits and vegetables in a healthy diet is encouraged as a means of decreasing the incidence of obesity, diabetes, cardiovascular
disease, osteoporosis, and cancer. Fruits and vegetables, whether used fresh or processed, must be of optimal maturity and quality to ensure appealing and nutritious products for consumers. Consumers are interested in the health benefits of consumption whole foods, rather than extracts of single compounds, as a means to slow onset or progression of chronic diseases. For instance, dietary changes for consumption of specific berries for preventing cancer recurrence or for inflammation, or of vegetables high in xanthophylls to help overcome or slow macular degeneration has been put forward as a way to extend quality of life. While much work has been focused on identification of genetic and environmental effects on plant compounds, little has been done to look at ways to enhance compounds of interest after harvest. In order to preserve quality, shelf life strategies have to be devised for
each commodity that are based on certain indicators, such as rates of respiration and water loss, response to presence or absence of ethylene, and sensitivity to low or warm temperature storage. As the successful engagement of these strategies has been accomplished, the definition of quality has also changed. High quality product, once expected only to be free of injury, decay, and of attractive appearance, is now also expected to be safe (free of food borne pathogens or pesticides), of appealing aroma and taste, and have elevated levels of vitamins, minerals, and phytochemicals. Further, development of niche markets for functional foods tailored for at-risk individuals has driven interest in high quality produced with enhanced and specific phytochemicals. A marketed example of this is tocopherol-enhanced broccoli (Beneforte TM). And, as techniques expand in metabolomics and
proteonomics, it has become simpler to determine the effects that breeding techniques or production changes have on biochemical events in plants, and which specific phytochemicals trigger desirable changes in human metabolism.
<p>APPROACH:<br/> PROCEDURES: Objective 1. Enhancing quality of fruits and vegetables, including breeding selections and those grown in protected environment systems Investigate treatments to extend small fruit shelf life Compare postharvest quality in advanced selections of breeding trials in strawberry, raspberry, and blackberry Develop rapid screening systems for physical and biochemical composition of small fruits Protocols for raspberry quality ratings have been established. High tunnel production effects on quality and productivity continue to be challenging, and application of new types of production systems, such as long cane, require additional evaluation. Muscadine grape production for fresh market is currently an emerging crop in NC and the southern US, with evaluation of suitable selections needed to establish shelf life limits. Protocols for muscadine shelf
life and ratings have been developed and will be used to further evaluate new selections. Fruit quality parameters and issues in small fruit are well defined. Ability to withstand decay, leakage and weight loss over time in the value chain are the primary limitations of small fruit marketability. Spotted Wing Drosophila (SWD) has become a major invasive pest for small fruits, especially blackberry and raspberry. Fruit will be harvested directly into clamshells (plastic boxes) and held at 5 or 20 C for 3 days to 3 weeks at relative humidities of 50 to 95%. Preliminary data indicate that fruit decay in tunnel-grown strawberries begins at 6 days postharvest at ambient temperature (20 C) while decay at 5 C takes 3 weeks to develop early in the harvest season. Amount of decay (0 (none) to 3 (completely covered)) will be noted as well. For raspberries, firmness will be estimated using a
firmness tester (FDIX 20 kg (Wagner Instruments), drill press mounted) and measuring resistance to closing of the fruit opening. Blackberries will be rated for firmness with a subjective system of 1 to 5 (firm to mush), decay, and leakiness using the protocol developed by Perkins-Veazie (1996). Strawberry firmness will be monitored by resistance to compression using a FDK10 fruit gauge (Wagner instruments, Greenwich, CT). Preharvest applications of waxes will be tested to determine their effectiveness in deterring SWD and the effects of such applications on yield and postharvest quality. Objective 2. Identification and quantification of compounds affecting shelf life and phytochemical importance in fruits and vegetables Screen Rubus germplasm for carotenoids Determine complete phenolic profile in watermelon fruit Breeding lines of raspberry, blackberry, strawberry, tomato, and
watermelon will be evaluated for nutritional and phytochemical compounds of interest. In watermelon, a number of heirloom and seedless types will be used to determine total lycopene and citrulline using spectrophotometric, Perkins-Veazie et al., 2001) and complete carotenoid profile screening will be done using hexane and methanol extracts (Craft, 2001) and mass spectrometry. Tomatoes of a number of lines developed over the past three decades by Dr. Randy Gardner will be grown at Mills River, NC by Dr. Panthee and harvested and frozen for total lycopene and soluble solids content determinations. At least 2 harvests per selection, consisting of 4 fruits per harvest, will be used. Total lycopene content will be determined by Hunter colorimeter and soluble solids will be measured with digital refractometer (Perkins-Veazie et al., 2007). For small fruits (blackberry, raspberry, black
raspberry, strawberry), total phenolic and anthocyanin content will be determined using the methods of Sinwoharn et al. (2004). Specific anthocyanin glucosides and aroma volatiles of strawberry will be determined using QTOF (Quadrupole Time-of-Flight) mass spectrometry, adapting methods of Qian et al. (2005) and Wang et al. (2005).. Vitamin C will be monitored in strawberry using the spectrophotometric method of Hodges and Forney (2003) Carotenoids, including lycopene, beta carotene, and lutein of tomato, watermelon, and other crops as needed, will be determined using HPLC, spectrophotometric, and ultrascan methods (Craft, 2001; Sadler et al., 1990; Davis et al., 2003). Chlorophyll will be determined as needed in crops using 80/20% acetone:water extracts (Lichtenthaler, 2001). Objective 3. Develop technologies and tools for small growers for postharvest use Adaptation of Pack N Cool
trailer for small grower uses Postharvest Internet portal A 5x8 cargo trailer was insulated and fitted with cool bot technology, which creates refrigerated storage to 34 F utilizing a home air conditioning unit. Initial tests with the trailer proved highly successful, and numerous requests and interest in this mobile system has been expressed. Continuing work will be done to test limits and possible alternate uses of the system, as well as gathering temperature stability data and possible changes to the unit for better lighting and air movement. Considerable field testing of the unit by growers or other parties (farm to school programs, food pantries) will be coordinated and documented to gather application ideas and possible barriers to use. A postharvest website is needed within horticulture to link to multiple websites (such as those from UC Davis, University of Florida, Cornell) on
postharvest type storage recommendations or practical advice. Current research in postharvest at NCSU also needs a direct home. A portal has been initiated and will be populated. Facilities Facilities at the North Carolina Research Campus include individual laboratories of 1150 square feet and offices of 300 square feet, and access to cold rooms, dishwashing and storage areas located on each of 4 floors. Greenhouse and field space is available at the Piedmont Research Station in Salisbury, about 20 miles from the campus, and other locations in the state, including coastal and mountain locations. Facilities for highly specialized work are available in the adjacent building operated by the University of North Carolina, or on the NCSU main campus at Raleigh. Such facilities include controlled environment growth chambers, pilot food processing equipment, near infrared spectrophotometer.
Statistical design and methods of data analysis For large data sets with genotype only, a general linear means model will be used with mean separation tests such as LSD or Bonferroni. For data sets having genotype x environment components, a proc mixed model will be used and mean separations made using a robust analysis, such as that suggested for GXE studies in broccoli by Brown et al. (1999). In experiments where sensory components will be compared, principal component analysis will be used and consultation with an NCSU statistician will be done to interpret results.