Good Fruit Grower

June 1

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MCP results influenced by temperature "CA provides another brake on the system." —Jim Mattheis M Conditioning at a higher temperature after storage helps improve ripening of MCP-treated pears. by Geraldine Warner any factors influence how SmartFresh (1- methylcyclopropene) works, which means that there are several potential tools that packers can use that will result in more pre- dictable ripening of pears at different points in the season, says Dr. Jim Mattheis, postharvest physiol- ogist with the U.S. Department of Agriculture in Wenatchee, Washington. How pears respond to an MCP treatment depends on: maturity of the fruit at harvest, the interval between har- vest and treatment, the MCP concentration, the tempera- ture of the fruit when treated, storage conditions, storage duration, and poststorage conditions. Mattheis has done research on the effects of tempera- ture during storage and afterwards. Some years ago, he did experiments in which he stored MCP-treated pears in the lower, mid-, and upper 30s, and found that the warmer the storage temperature, the sooner the pears' ability to ripen was regained. He's also done experiments with both Bartlett and d'Anjou that showed that conditioning the fruit at 68°F after storage enhanced ripening. In pilot tests with Bartlett pears in bins, the fruit was treated with MCP at 300 parts per billion and stored in regular atmosphere for two months. Most of the fruit reached a firmness of four pounds or less after being held at 68°F for five days after storage, then stored at 32°F for two weeks to simulate transit, and then being held at room temperature for one or two weeks to ripen. In similar tests, d'Anjou pears were stored for four months in controlled-atmosphere storage before the conditioning treatment. After two weeks of ripening at room temperature, the pears were all less than six pounds pressure. Mattheis said the amount of conditioning needed tends to decrease the longer the fruit is in storage. CA storage Controlled atmosphere storage presents its own set of challenges because both the chemical and the low-oxygen atmosphere inhibit eth- ylene, Mattheis observed. In the same experiments, fruit held for as long as eight months in CA, that was not subject to the higher conditioning temperatures, never did get below six pounds pressure. "CA provides another brake on the system," he said. "Particularly if you're not going to be storing for long term—or even if you are—you have to ask yourself how much is this going to be a factor in what you're going to get later." Because CA adds to the effects of MCP, it might not be necessary to store treated fruit in CA, he believes. Alternatively, a higher oxygen level could be used in the CA atmosphere. • DOES MCP affect flavor? A Your Agricultural Water Quality Specialists • Irrigation Water Quality for optimum irrigation system efficiency and delivery • Irrigation Water Microbiology for Good Agricultural Practices (GAP) • Warehouse Process Water Quality for wastewater discharge compliance • Warehouse Water Microbiology for food safety verification program • Drinking Water Potability Tests for worker housing requirement 3019 GS Center Road Wenatchee, WA 98801 509-662-1888 38 JUNE 2012 GOOD FRUIT GROWER • 800-545-4206 • 1008 W. Ahtanum Road, #2 Union Gap, WA 98903 509-452-7707 www.cascadeanalytical.com question that scientists say needs to be researched further is whether MCP (1-methylcyclopropene) affects the flavor and aroma of fruit after storage. Dr. Enrique Sanchez, researcher with the National Institute of Agricultural Technology in General Roca, Argentina, said Argentine fruit producers are concerned about whether MCP, sold under the brand name Smart- Fresh, reduces the aroma of the pears. "Some people believe that the production of esters is modified with the use of SmartFresh," Sanchez said. "We need to run some consumer tests to verify that." Dr. Jim Mattheis, postharvest physiologist with the U.S. Depart- ment of Agriculture in Wenatchee, Washington, said that in tests he conducted, MCP-treated d'Anjous tasted like ripe pears. "Whether they're equivalent to a piece of fruit that's never seen SmartFresh, that's another story which perhaps needs to have more research done," he added. Mattheis has analyzed the effects of storage on fruit flavor and he suspects the flavor of MCP-treated pears is similar to that of pears held in CA storage without MCP. Low oxygen tends to delay or inhibit the capacity of climacteric fruit to produce ripe flavors when it comes out of storage. —G. Warner www.goodfruit.com Jim Mattheis

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