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United States Department of Agriculture

Agricultural Research Service

2009 Annual Report

1a.Objectives (from AD-416)
Develop novel or alternative postharvest systems to maintain quality of intact and fresh-cut fruits and vegetables with consideration of cultivar selection, physical and sensory characteristics, physiology, pathology, food safety, and produce responses to non-chemical and GRAS (Generally Regarded As Safe) treatments. Apple, melon, pepper, squash, tomato, and potentially other products will be evaluated. Develop new or improved instrumental quality measurements after elucidating the relationships between physical and sensory characteristics of intact and fresh-cut products.

1b.Approach (from AD-416)
The approaches used in this project to reach our objectives will be based on developing and integrating different technologies to achieve the desired levels of quality, stability and safety. We will integrate technologies such as cultivar selection, postharvest non-chemical and chemical treatments to prevent or decrease microbial contamination, fresh-cut processing methods, biocontrol methods, modified atmosphere packaging, and different storage regimes. Microbial assays, sensory evaluations, and a variety of instrumental methodologies will be used or developed to measure changes in produce quality and safety after treatment. Specifically, alternative processing and packaging technologies to improve shelf stability and food safety of fresh-cut products will be combined with the selection of optimal cultivars. Methods for maintaining quality of intact produce with GRAS (generally regarded as safe) substances will be optimized. Instrumental methods that better predict overall quality or specific sensory characteristics will be developed following study of the relationships between physical and sensory properties.

3.Progress Report
Fruit of the worldwide cultivated green bell pepper (Capsicum annuum) often lack the unique flavor qualities of chili peppers. As a result, worldwide production of green bell peppers has stagnated while production of chili peppers has more than doubled over the past decade. While less cultivated than bell peppers, ají chili peppers (C. baccatum) are well known for their fruity flavor qualities. We have selected a fragrant, tasty C. baccatum accession and have identified and quantified flavor-related aromatic volatiles (esters, sesqueterpenoids, C5-C8 aldehydes, ketones and alcohols), sugars and organic acids. Many of these compounds are lacking or occur at significantly lower levels in green bell peppers. This characterization of flavor quality in ají peppers is the first step towards selecting C. baccatum breeding lines for development of C. annuum (bell pepper) stocks with enhanced flavor quality. Improving the flavor quality of green bell peppers will increase consumer demand for this nutritional fruit.

Two of the most serious problems affecting the postharvest quality of litchi fruit are decay and browning or loss of red color on the peel of the fruit. We found that treatment of litchi fruit with acidified calcium sulfate, a GRAS (Generally Recognized As Safe) compound, could inhibit the mold growth, prevent browning and retain red color of the peel. We also showed that this treatment did not have an adverse effect on the internal quality of the litchi fruit including soluble solids, sugar, and organic acid contents. Information obtained in this study is of interest to other scientists and will be useful and beneficial to the litchi fruit industry and consumers.

Apple is one of the most important species of temperate fruits but cultivated varieties are susceptible both pre- and post-harvest to a number of fungal pathogens that most often are controlled by fungicides. Breeding for resistance against decays is limited due, at least in part, to the little variation in resistance in the gene pool currently used in breeding programs. A wild apple germplasm (Malus sieversii) collection from Kazakhstan, maintained in Geneva, NY and representing a much broader gene pool than that used by apple breeders, were evaluated for postharvest physiological characteristics that could affect disease resistance and for resistance against two important postharvest pathogens, Penicillium expansum and Colletotrichum acutatum. Across 170 accessions, appropriate harvest dates for pathological evaluations were identified and little (r < 0.3) to no correlation was found between physiological characteristics (respiration and ethylene production rates, soluble solids content and titratable acidity) and decay incidence caused by the pathogens. In fruit from some accessions, disease resistance against one or both postharvest pathogens was greater than that generally present in domesticated apples. These findings are a first step towards selecting M. sieversii breeding lines for development of domestic apple cultivars with increased postharvest disease resistance. Fruits of these cultivars would require less dependence on use of postharvest fungicides.

1. Postharvest UV-C treatment improves quality of blueberries. Decay of fruits and vegetables is one of the major causes of postharvest losses in fresh produce. Various methods have been used to inhibit decay with most involving the use of fungicides. Increased resistance of many pathogens to fungicides and the concerns over health risks and environmental contamination have resulted in the withdrawal of a number of key fungicides from the market. These developments have stimulated the search for alternative methods of treatment. We have found that by using brief periods of UV-C exposure, better quality of blueberries could be maintained as compared to the control fruit. After 1, 5, 10, and 15 minutes of exposure of blueberries to germicidal UV-C lamps, higher antioxidant values were detected in the treated samples than in the untreated fruit. Results indicate that UV-C treatment is beneficial for maintaining the quality of blueberry fruit. Information presented in this study is of interest to other postharvest researchers and of commercial value to the produce industry.

6.Technology Transfer

Number of Active CRADAs1

Review Publications
Jin, P., Zheng, Y., Tang, S., Rui, H., Wang, C.Y. 2009. Ehancing disease resistance in peach fruit with methyl jasmonate. Journal of the Science of Food and Agriculture. 89:802-808.

Jin, P., Zheng, Y., Tang, S., Rui, H., Wang, C.Y. 2009. A combination of hot air and methyl jasmonate vapor treatment alleviates chilling injury of peach fruit. Postharvest Biology and Technology. 52:24-29.

Saftner, R.A., Lester, G.E. 2009. Sensory and analytical characteristics of a novel hybrid muskmelon fruit intended for the fresh-cut industry. Postharvest Biology and Technology. 51(3):327-333.

Wang, C.Y., Chen, C., Wang, S.Y. 2009. Changes of flavonoid content and antioxidant capacity in blueberries after UV-C illumination. Journal of Food Chemistry. 117:426-431.

Last Modified: 7/12/2014
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