A Plum Assignment

New Storage Methods Extend Life of Japanese Plums

Wickson, a Japanese plum released by Luther Burbank and named after E.J. Wickson, friend and dean of agriculture at the University of California, Berkeley. Click here for more information.

PERTH, AUSTRALIA — Plums: they’re sweet, juicy, and packed with beneficial antioxidants and dietary fiber. Although there are many varieties available to consumers, there are two main types of the small, purple fruit: Japanese plums and European plums. Japanese plums are the most widely grown type and are round, while oval European plums are commonly used for making dried plums, or prunes.

Getting fresh plums to the marketplace has been a challenge for fruit producers. The short shelf life of Japanese and European plums limits export and shipping options—Japanese plums can typically be stored for only three to five weeks after harvesting. For years, researchers have tested a variety of techniques to extend the storage life of Japanese and European plums, including preharvest calcium application, postharvest heat treatment, application of an edible coating, cold storage, and “modified atmosphere storage”. Results of the tests have been inconclusive and sporadic.

Ahmad Sattar Khan, a PhD student, and Dr. Zora Singh, Associate Professor of Horticulture at the Muresk Institute, University of Technology in Perth, Western Australia, recently carried out a research project attempting to extend the postharvest storage life of Japanese plums (Prunus salicina Lindl. cv. Tegan Blue). The study, published in the Journal of the American Society of Horticultural Science, tested the effects of modified atmosphere packaging (MAP), and the application of 1-methylcyclopropene (1-MCP), a fumigant, on Japanese plums, including the effects on the fruit’s dietary antioxidants and overall quality.

According to the report, a combination of modified atmosphere packaging and 1-MCP had been shown to extend the storage life of plums with varying results, depending on storage conditions and type of polyethylene film used under MA storage.

The long-term storage study garnered important new information that will allow fruit producers and exporters to extend the storage life of Japanese plums for up to seven weeks. The researchers concluded that “1-MCP application in combination with MAP can be used effectively to reduce the ethylene biosynthesis and fruit softening during cold storage and to extend the storage life up to seven weeks followed by eight days of ripening without any adverse effects on the quality of the fruit.”

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The complete study and abstract are available on the ASHS Journal of the American Society of Horticultural Science electronic journal web site: http://journal.ashspublications.org/cgi/content/abstract/133/2/290

Founded in 1903, the American Society for Horticultural Science (ASHS) is the largest organization dedicated to advancing all facets of horticultural research, education, and application. More information at ashs.org.

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This press release also available on EurekAlert!

Original Article:

1-Methylcyclopropene Application and Modified Atmosphere Packaging Affect Ethylene Biosynthesis, Fruit Softening, and Quality of ‘Tegan Blue’ Japanese Plum During Cold Storage
Ahmad Sattar Khan and Zora Singh
J. Amer. Soc. Hort. Sci. 2008 133: 290-299. [Abstract] [Full Text] [PDF]

Corresponding author. E-mail Z.Singh@curtin.edu.au

Good Breeding Increases Shelf Life

Packaged salad-cut lettuce studied for stability, freshness

Salinas iceberg lettuce. Click here for more information.

SALINAS, CA – The lettuce cut and packaged for food service and salad mixes is an increasingly important component of the produce industry. Lettuce is highly perishable, and the cutting required in processing further shortens its shelf life.

Packaging cut lettuce and other fresh produce in semipermeable plastic films extends shelf life via a technique called “modified-atmosphere packaging”. The success of modified-atmosphere (MA) packaging for lettuce and certain salad greens has led to innovative products, marketing strategies, and enhanced sales to consumers.

Increased demand for the convenient, pre-cut salads and lettuce has led to scientists to search for ways to select lettuce cultivars that stay fresh, colorful, and crisp. Shelf life and visual quality of salad-cut lettuce are affected by many things, including production environment, vegetative maturity, and type of lettuce chosen. Although an increasing variety of lettuce types are being grown, romaine and “crisphead” (such as iceberg) are the most widely produced for salad-cut products

Ryan J. Hayes, a research geneticist, and Yong-Biao Liu, research entomologist at the U.S. Department of Agriculture’s Agricultural Research Service, published the results of a study that should give lettuce breeders and producers enhanced product information and a market edge. During the two-year study, lettuce was processed from field-grown plants of 33 romaine and three “crisphead” cultivars. Shelf life of each cultivar was evaluated after storage in modified-atmosphere bags and in CO₂-free controlled-atmosphere chambers.

Lettuce cultivars ‘Clemente’, ‘Darkland’, and ‘Green Forest’ performed consistently well, ranking in the top 10 in every experiment. ‘Alpi’, ‘Dark Green Romaine’, and ‘Queen of Hearts’ showed clearly unstable shelf life. Hayes noted, “cultivars that performed well in our MA environments will likely be useful as parents in breeding programs to develop new romaine cultivars with an acceptable shelf life. It is also clear that not all crisphead cultivars have good shelf life. Wide variation was observed between the crisphead cultivars Pacific, Salinas 88, and La Brillante.”

In concluding the impact of the study outcomes, Hayes stated; “Breeders can use these methods to characterize or identify breeding lines that are suitable for salad-cut markets before release, and to select for increased shelf life within breeding populations. These practices should facilitate a consistent release of germplasm with high quality in MA environments.”

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The complete study and abstract are available on the ASHS Journal of the American Society for Horticultural Science electronic journal web site: http://journal.ashspublications.org/cgi/content/abstract/133/2/228

Founded in 1903, the American Society for Horticultural Science (ASHS) is the largest organization dedicated to advancing all facets of horticultural research, education and application. More information at ashs.org

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This press release also available on EurekAlert!

Original Article:

Genetic Variation for Shelf-life of Salad-cut Lettuce in Modified-atmosphere Environments
Ryan J. Hayes and Yong-Biao Liu
J. Amer. Soc. Hort. Sci. March 2008 133:228-233. [Abstract] [Full Text] [PDF]

Corresponding author. E-mail rhayes@pw.ars.usda.gov