Calcium treatment extends melon shelf life and its markets.

Fresh honeydew melons are no longer just seasonal delights. They can be eaten year-round, and USDA/ARS efforts to improve their postharvest life may increase their appeal even more. Scientists at the ARS Subtropical Agricultural Research Center (Crop Quality and Fruit Insect Research Unit, 2301 S. International Blvd., Weslaco, TX 78596) and at the Children's Nutrition Research Center (Houston, TX) have found a way to extend the marketable life of melons.

The researchers soak the melons in a special calcium solution during the time it takes to cool them right after harvest. The treatment could allow growers to provide sweet and tasty, vine-ripened melons in greater quantities and to more distant markets. In laboratory and preliminary field tests, the treatment prolonged market life by at least two weeks. It also increased calcium levels in the melons. Even without the treatment, honeydews and cantaloupes are rich sources of calcium, with a one-cup serving providing about 10% of an adult's daily calcium needs.

This melon research started with plant physiologists who previously developed techniques for studying the movement of calcium from roots to edible portions of vegetable plants. They found that certain calcium solutions reduced tissue aging. Aging melons, especially the tissue associated with the rind, need calcium to maintain a certain degree of firmness that protects against spoilage. But in ripe melons, calcium steadily migrates from the rind to the seeds, depleting the rind of calcium needed for maintaining cellular functions.

In experiments, the scientists treated freshly-harvested melons for 20 min in a 40-millimolar calcium solution (1.6 g of calcium/L) chelated with amino acid. Within 24 hr, the calcium in honeydew rind tissue measured about 24% of the calcium that was applied. In cantaloupes, the amount of calcium was less: up to 12%.

The shelf life of vine-ripened honeydew and cantaloupe is generally about seven to 12 days. Increased calcium in treated greenhouse-grown honeydews at least doubled their shelf life. The scientists found an application of amino acid-calcium chelate solution with at least 80 millimolar of calcium (3.2g of calcium/L) was needed to appreciably extend the shelf life of whole honeydews or cantaloupes grown in the greenhouse. Up to 100-millimolar calcium solutions are now included in ongoing experiments with field-grown melons, which tend to have thicker rinds.

The research has led to industry interest. A major U.S. melon grower/shipper, Starr Produce Co. (Rio Grande City, TX), is providing vine-ripened melons for the research.

Further information. Gene Lester; phone: [phone]; fax: [phone]; email: [e-mail].