NE1036: Postharvest Biology of Fruits
Statement of Issues and Justification
The Need: Consumption of fruit contributes substantially to human health, and increased fruit consumption is suggested as one means to help curb the alarming rise in obesity and diabetes in the U.S. American markets offer an array of moderately priced fruits of apparent good quality, the result of decades of effort by fruit breeders and postharvest specialists, yet daily consumption continues to fall far short of the recommended 3 to 5 servings. Despite abundance and availability, consumers limit fruit purchases, their foremost complaints being insufficient quality and lack of flavor. Fruit producers often market fruit from cultivars with marginal quality and flavor to maintain market share, or switch to new cultivars with perceived increased value, but for which several years of research are needed to best maintain postharvest quality and shelf life. The key to increasing consumption of fresh fruits, and for maintaining grower income, viable U.S. fruit production, and export opportunities, lies in providing fruit with superior flavor and long shelf life that are also perceived as healthy, both in terms of nutrition and minimal risks from agrichemicals or pathogens.Fresh fruit industries continue to rely heavily on postharvest chemicals to control microbial decay, insects, and physiological disorders during storage. Moreover, some fungal pathogens on stored apples and other fruits produce cancer-causing mycotoxins, thus increasing the need for disease control. While advances have been made in nontoxic alternatives or sustainable systems, changes in the types and amounts of chemicals used have created a need to modify storage technologies. New approaches are needed to minimize losses of fruit during storage and transport, and thereby maintain global market share for domestic producers. A better understanding of relationships between postharvest physiology of fruits and their susceptibility to decay, disorders, and insects is essential for developing improved control measures and reducing chemical use.
Adoption of non-apple production by small acreage growers or by tree fruit growers who wish to expand crop diversity have increased over the last five years. Cultivation of many small fruits and vegetable fruits can easily be adapted to fit organic production or extended harvest (i.e., tunnel and plasticulture) systems, but cultivars and genotypes suitable to these systems often differ from those used in traditional systems. Small fruits also differ from many tree fruits in length and type of storage, ethylene sensitivity, and types of disorders. Hence, postharvest technologies must be developed or modified to extend storage life and maintain quality and safety in small, organically produced, and extended season fruits.
Importance of the Work: Previous (NE103) and current (NE1018) versions of this project have made considerable contributions to the fresh fruit industry. These include adoption by the industry of innovative applied methods developed by the group, and basic research on postharvest problems such as superficial scald in pome fruits, which has led to more effective control measures and knowledge of the genetic and biochemical causes of the disorder. The discovery and commercialization of 1-methylcyclopropene (1-MCP) as a means of controlling fruit ripening, maintaining fruit quality in storage, and reducing storage disorders has developed into a critical area of research for this project. 1-MCP was approved for food use in July 2002 and is currently used commercially on apples in several states. It has very low toxicity and negligible residues, and is effective at low concentrations. Over the past five years, members of NE1018 have conducted extensive research on postharvest quality of apples treated with 1-MCP, and the concerted efforts of NE1018 have been instrumental in providing information to the fresh fruit industry that was essential for successful postharvest utilization of the technology. With new formulations of 1-MCP, preharvest sprays in orchards are now possible. The effects of these sprays on subsequent apple drop, apple quality, decay susceptibility, and shelf life are not known, and our new multistate project will conduct the research required to evaluate, optimize, and implement this new technology.
Technical Feasibility and Value of a Multistate Project: As new fruit crops and cultivars are introduced and production practices are modified, there are continuously emerging postharvest challenges and needs for development of new storage and quality methodologies. Storage protocols for temperate fruits are cultivar- and often region-specific, and must be optimized to reduce postharvest losses. The broad geographical distribution of the team in this project provides a unique situation where responses of cultivars to a wide range of growing conditions can be studied. New apple cultivars such as Honeycrisp have been widely planted in the U.S. and a number of physiological and pathological disorders limit continued expansion and threaten viability of the industry. Information on problems with both older, established and replacement cultivars in regional growing areas has become increasingly important as fossil fuels and food safety issues have made consumers more interested in regionally produced fruit. At least six research stations participating in NE1018 are currently collaborating to establish the best postharvest practices for the prized and profitable Honeycrisp apple in various regions of the U.S. and Canada. Plans for collaboration in the new multistate project include application of neural network analysis, using existing data from orchards in many locations to determine how orchard management regimes influence the incidence of storage disorders in Honeycrisp as well as other apple and pear cultivars.
A group of NE1018 researchers is also on the cusp of elucidating the genetic and biochemical mechanisms involved in the induction of superficial scald, and future combined efforts hold the promise of developing new scald-resistant cultivars that do not require the chemical drench currently used to control the costly disorder. Increasing consumer appeal of U.S. fruit through improvement of texture, flavor, and aroma can best be approached by a broad array of sensory, physiological, biochemical, and molecular genetic techniques. No individual state has the expertise and resources required to address all aspects and issues of fruit quality, but in a multistate project their respective strengths can be synergistically applied in a coordinated effort to solve problems with quality and flavor. A multistate project provides a team approach, rich in ideas and expertise, and therefore is best suited to investigate postharvest issues and problems, and provide much needed recommendations and solutions to the fresh fruit industry, both regionally and nationally.
Impact: The products of the NE1018 project have included extensive evaluation of apple cultivars and development or alteration of methodologies to best enhance storage life, quality, and flavor; the development of effective protocols that can be used by the industry for controlled atmosphere/low oxygen storage; and the elucidation of mechanisms involved in flavor and storage disorder development in fruits. The proposed new project will make similar valuable contributions, continuing to develop and improve methods and technologies for evaluation, maintenance, and genetic enhancement of postharvest quality of fresh fruits. The primary goals of our new research project are to increase competitiveness for domestic fruit production and preserve 'fresh-picked' sensory and nutritional quality, which in turn will encourage more fruit consumption for improved human health. To meet these goals, we will evaluate the storage potential of new cultivars, make better use of existing storage technologies, and develop new, safer technologies requiring minimal use of chemicals. Underpinning this research, we have a group investigating the metabolism of ripening and the biological causes of physiological disorders. Our research emphasis has shifted somewhat, with greater focus on the effects of postharvest handling on fruit nutritional and flavor quality because of their importance to consumers. Specialist skills within this multistate project will foster collaborative activity among regions, enabling broader and more rapid advances in postharvest research. The overall impact of this project will be to improve the long-range health of the American populace via greater consumption of fresh fruits, and to increase profitability of large-scale national as well as small-scale, local and organic fruit production.
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