2006 Annual Report
1.What major problem or issue is being resolved and how are you resolving it (summarize project aims and objectives)? How serious is the problem? Why does it matter?
Major postharvest losses of fresh produce occur during cold storage. Additional losses result from processing and marketing of fresh-cut produce. Deterioration of fresh and fresh-cut produce during cold storage can be prevented, or at least diminished. Major problems of fresh-cut products are physiological deterioration, browning and microbial decay at the cut surfaces. We are using several natural products and antioxidants such as methyl jasmonate, amino acids, organic acids, and calcium salts and chelates to alleviate temperature stress and to inhibit enzymatic browning and texture deterioration. This results in a slowdown of microbial growth as well as decreasing the rate of physiological deterioration of cold temperature-sensitive produce. Texture is a critical quality factor for fresh fruits and vegetables because it relates to consumer acceptability, microbial contamination, and senescence. Most existing instrumental texture measurements were developed for intact fruits or vegetables and are not readily adaptable to fresh-cut sliced or diced products, so new methods must be developed. The changes in texture of fresh-cut produce in response to preparation and storage are not well documented. We are investigating the mechanical properties that change after a fruit or vegetable is cut and stored and how those changes relate to sensory assessments of quality and consumer acceptability. Based on changes in those characteristics, effective instrumental measurements can be developed for routine inspection and for physiological studies. We are also investigating the impact of changes in volatile aroma compounds during storage on sensory acceptability of fresh-cut fruit.
Postharvest losses of fresh produce range from 10 to 50% depending upon commodity and storage facilities. Further losses result from fresh-cut processing and marketing where shelf-life of various items will range from three days to three weeks. Extension of shelf-life would be beneficial with some fresh-cut products as would development of methods to allow use of other produce now considered too sensitive for current processing and storage procedures. As an example, the application of natural antioxidants could open up a market for fresh-cut fruit slices allowing development of new value-added products. One specific problem area being addressed is the prevention of tissue browning that detracts from appearance and reduces market value of fresh-cut produce. Microbial growth on fresh and fresh-cut produce not only affects quality, but also reduces shelf-life of the products. Better methods of preventing browning and reducing decay are urgently needed if postharvest quality of fresh and fresh-cut fruits and vegetables is to be improved. Texture is frequently the quality attribute limiting the acceptability of fresh fruits and vegetables by the consumer. Cutting and packaging of produce can cause texture breakdown and cause certain quality-related volatiles to either decrease or increase, and these changes may alter consumer acceptability. Because it is such a new industry, there are no established, traditional measurements of quality of fresh-cut products other than sensory (appearance, feel, and taste). Rapid, accurate, and reproducible grading methods will systematize the measurement of quality of these value-added products.
The proposed research falls within Component 1 of NP-306 on "Quality Characterization, Preservation, and Enhancement." The project focuses on Category 1 (Fruits, Vegetables, Tree Nuts, and Sugar Crops) and addresses Problem Area 1a, "Definition and Basis for Quality" and Problem Area 1d, "Preservation and/or Enhancement of Quality and Marketability."
2.List by year the currently approved milestones (indicators of research progress)
Milestones are from a project approved by OSQR and having a start date of 09/25/04.
Year 1 (FY 2005)
Better tasting fresh-cut apple cultivars selected.
Orange-fleshed fresh-cut honeydew evaluated.
Approximately ten GRAS substances evaluated.
Texture panel trained.
Crispness and crunchiness defined.
Year 2-3 (FY 2006-2007)
Alternative processing protocols formulated.
Food-safe product developed.
Alternative sanitation technologies developed.
Effective antimicrobial substances and dosages identified.
MAP technologies optimized for fresh-cut apples.
Sensory and instrumental texture of ~30 commodities measured.
Sensory and instrumental measurements made on fresh-cut apple and melon products.
Year 4-5 (FY 2008-2009)
GRAS treatments optimized.
Combination processing and MAP strategies established.
Statistical models for hardness, crispness, crunchiness, and toughness in high-moisture products developed and validated.
Instrumental texture measurement methods for fresh-cuts recommended.
Models proposed for predicting sweetness, sourness, and acceptability of fresh-cut apple and melon from instrumental measurements.
4a.List the single most significant research accomplishment during FY 2006.
New treatment extends shelf-life of fresh-cut apples. Sliced apples are particularly in demand by retail food-service operators and school food-service directors--current treatments allow a shelf-life of up to about 3 weeks. An optimized, in-house dip, or wash treatment, named PQSL2.0 effectively maintained the quality of apple slices. Formula PQSL2.0 also reduced microflora that accelerate spoilage over time and completely inhibited two pathogens—Listeria and Salmonella—on apple slices themselves during three weeks of storage. These results are a significant development in keeping sliced apples both fresh and safe. NP 306, component 1d.
4b.List other significant research accomplishment(s), if any.
Reduction of decay in berry f ruits using essential oils. Decay is a main problem during the postharvest life of berry fruits. Several natural essential oils with antomicrobial property were found to be effective in reducing decay of berry fruits during storage. Treatment with these essential oils (notably eugenol, menthol, and thymol) also maintained high amounts of sugars and organic acids and increased the contents of total phenolics, anthocyanins, and antioxidants in strawberries, blueberries, and blackberries. This information is useful to other scientists and is beneficial to the berry industry. NP 306, component 1d.
4c.List significant activities that support special target populations.
5.Describe the major accomplishments to date and their predicted or actual impact.
This project is in its second year, significant accomplishments have been achieved in identifying the best apple and melon cultivars for fresh-cut processing. In addition, alternative processing aids have been developed and cultivars selected that maintain the analytical, sensory and microbial quality and/or food safety of these fresh-cut fruit products better than that attained using current commercial practices.
Many GRAS substances have been evaluated for their effectiveness in reducing decay, alleviating chilling injury, and extending storage life. Several of these naturally occurring compounds, including methyl jasmonate, methyl salicylate, tea tree oil, allyl isothiocyanate, acetic acid, and ethanol have been identified to be effective in maintaining the quality of various commodities. The mechanisms of how these compounds exert their effects and their potential benefits to the produce industry will be investigated.
The optimal times to treat whole apples, watermelons and tomatoes with 1-methylcyclopropene (1-MCP), a gas used commercially to maintain fruit quality during storage, has been determined along with recommended dosages for each fruit type. Appropriately timed 1-MCP application(s) of whole fruit maintain quality and shelf-life of fresh-cuts processed from the treated fruit. Modified atmosphere packaging inhibits weight loss during storage of fresh-cut fruits but risks unacceptable carbon dioxide accumulation, tissue breakdown and off-odor development. NP306, component 1d.
6.What science and/or technologies have been transferred and to whom? When is the science and/or technology likely to become available to the end-user (industry, farmer, other scientists)? What are the constraints, if known, to the adoption and durability of the technology products?
Confidentiality Agreements have been made with a Vegetable Seed Co. and its Research Partners regarding quality and shelf-life evaluations of orange-fleshed hybrid melons specifically being developed for the fresh-cut fruit industry. Reports have been made to AgroFresh Inc., manufacturer of 1-MCP, regarding efficacy of treating whole fruit with 1-MCP to maintain the quality and shelf stability of fresh-cuts processed from the 1-MCP-treated fruit.
7.List your most important publications in the popular press and presentations to organizations and articles written about your work. (NOTE: List your peer reviewed publications below).
Article for Agricultural Research/July 2006 "Fresh-cuts are popular, any way you slice them."
Invited presentations at Annual Meeting of the International Fresh-cut Produce Association entitled "Creating Tomorrow' Fresh-cuts", "Maintaining the Microbial Quality and Food Safety of Fresh-cut Apple Products using a Hot Water Pretreatment and a Low pH Wash Treatment" and "Development of a New Orange-fleshed Melon Genotype for Fresh Cutting."
Co-organized ARS/BA Produce Quality and Safety Laboratory Tour and Research Briefing for members of International Fresh-cut Produce Association.
Liu, Y., Chen, Y.R., Wang, C.Y., Chan, D.E., Kim, M.S. 2005. Development of hyperspectral imaging technique for the detection of chilling injury in cucumbers: Part I. Spectral Analysis. Applied Engineering in Agriculture. 22:101-111.
Zhou, B., McEvoy, J.L., Luo, Y., Saftner, R.A., Feng, H., Beltran, T. 2006. Application of 1- methylcyclopropene reverses the deleterious effect of exogenous ethylene on fresh-cut watermelon and controls microbial growth. Journal of Food Science. 71:1-5.
Chanjirakul, K., Wang, C.Y., Wang, S.Y., Siriphanich, J. 2006. Effect of natural volatile compounds on antioxidant capacity and antioxidant enzymes in raspberries. Postharvest Biology and Technology. 40:106-115.
Gonzalez-Aguilar, G., Tiznado-Hernandez, M., Wang, C.Y. 2006. Physiological and biochemical responses of horticultural products to methyl jasmonate. Stewart Postharvest Review. 2:1-9.
Wang, C.Y. 2006. The use of essential oils as natural preservatives for berry fruits. [abstract]. HortScience. 41:1042-1043.