Lysophosphatidylethanolamine Accelerates Color Development and Promotes Shelf Life of Cranberries

Highly colored cranberries are desired for both fresh and juice markets. Berries accumulate more color when allowed to stay on the vines longer. However, early fall frosts often force growers to harvest before the fruit has reached its optimal color. This is especially true for the berries under the canopy. No product is currently available for grower to accelerate the color development in cranberries. Result from recent studies suggests that a natural lipid, lysophosphatidylethanolamine (LPE), can accelerate color production in fruit and, at the same time, promote shelf life. LPE is a natural lipid and is commercially derived from egg and soy lecithin. The influence of LPE on anthocyanin accumulation and storage quality of cranberry fruit (Vaccinium macrocarpon Ait. ‘Stevens’) was studied. Cranberry plants were sprayed with LPE at about 4 weeks before commercial harvest at multiple locations. Experiments were conducted in 1997, 1998 and 1999. Fruit samples were taken at 2 and 4 weeks after spray application to determine the changes in the fruit color. Plots were wet harvested using a standard commercial method and stored in a commercial cold storage facility. Marketable fruit were evaluated at 1 and 2 months after cold storage to determine effect of LPE on shelf life of cranberries. In general, a preharvest application of LPE resulted in a 9% to 27% increase in fruit anthocyanin concentration compared to the control. LPE treatments also resulted in 8% to 12% increase in marketable fruit compared to the control following cold storage. Influence of LPE on fruit quality was more apparent after 1 month of storage. These results are consistent with the observed effects of LPE on tomatoes. Interestingly ethanol application also enhanced storage quality. Our results suggest that a preharvest application of LPE may have the potential to enhance color and prolong shelf life of cranberry fruit. The commercial value of cranberries is directly related to anthocyanin development in the fruit since growers are paid a bonus by the processor for better fruit color. Also, berries with poor color are rejected for the fresh market. Berries accumulate more color when allowed to stay on the vines longer. However, early fall frosts often force growers to harvest before the fruit has reached its optimal color. This is especially true for the berries under the canopy. Thus, acceleration of color is important to cranberry growers. In addition to the fruit color, the value of fresh-market cranberries is also related to quality and shelf life of the berries. This is especially true for Wisconsin-grown berries where harvest is done more efficiently in flooded beds. Waterraked berries deteriorate much more rapidly in storage and have a shorter shelf life than dry-raked berries (Bergman, 1922; Ceponis and Stretch, 1983; Chaney, 1940). Recently we have found that fully colored berries store better than the white and blush colored berries (Ozgen et al., 2002). Thus, improving fruit color can be expected to enhance growers’ profit by improving shelf life. Several early studies showed that spray application of ethephon (Ethrel) was effective in improving fruit color (Bramlage et al., 1972; Devlin and Demoranville, 1970; Eck, 1972; Rigby et al. 1972). However field application of Ethrel had inconsistent results (Shawa, 1979), which were later explained by the lack of penetration of Ethrel across thick cranberry cuticle (Farag et al., 1992). Some studies have shown that the insecticide malathion (Devlin et al., 1969; Eck, 1968), and herbicide dichlobenil (Devlin and Demoranville, 1968) when applied as spray can induce fruit color in cranberries. However, at present these compounds, including Ethrel are not labeled for use on cranberries for color enhancement. Furthermore, growers are reluctant to use these products because of environmental concerns. Thus, currently no product is available to enhance color in cranberries. Recent studies from our laboratory indicate that lysophosphatidylethanolamine (LPE), natural phospholipids (derived from egg and soy lecithin), can accelerate ripening and prolong shelf life of tomato fruit (Farag and Palta, 1993a). LPE application has been found to enhance ethylene production in the fruit tissues (Farag and Palta, 1989a; Hong et al., 2001). More recently Hong et al. (2002) demonstrated that LPE can enhance the activity of ACC oxidase in mature green (ready to ripen) tomato fruit. Taken together these studies show that LPE can enhance ACC oxidase activity and enhance fruit ripening. Also, LPE has been found to retard senescence in attached and detached leaves and fruit of tomato (Farag and Palta, 1993b). In another study, the vaselife of LPE-treated cut flowers was extended by three days compare to the control (Kaur and Palta, 1997). LPE inhibited the activity of phospholipase D (PLD), a membrane degrading enzyme, whose activity is increased during plant senescence (Ryu et al., 1997). These results suggest a specific role of LPE in both ripening and storage quality of fruit. In the present study we investigated the use of LPE for accelerating ripening and prolonging shelf life of cranberry fruit. Materials and Methods Field trials were conducted over a three years period. For this purpose experimental plots were established in commercial cranberry (‘Stevens’) beds at seven locations near Wisconsin Rapids in central Wisconsin. Plots, 2 × 1 m in size, were sprayed with 1000 mL solutions by a hand sprayer when the top berries on the canopy were in the blush stage about 4 weeks before final harvest. Each experimental plot was separated by 2 × 1-m guard area to prevent mixing of the treatments during harvesting. To facilitate machine harvest plots were laid out in a row following the length of the bed. The width of harvester exceeded the plot (2m). The spray solution included LPE (200 mg·L), and Sylgard 309 (Abbott Laboratories, Abbott Park, Ill.) a silicone based nonionic surfactant (0.05% v/v). Ethanol (5% v/v) was included in the spray solution to enhance penetration of solution into the fruit (Farag et al., 1989). LPE derived from egg lecithin was used in our experiments and was obtained either from Avanti Lipids, Alabaster Ala., or from Doosan Serdary Research Lab., Englewood, N.J.. LPE was suspended in water by using a sonicator (sonic dismembrator model 550; Fisher Scientific, Pittsburgh Pa.). Experimental design was a randomized complete block with four replications for each treatment at each location. Experiment 1: Effect of LPE on fruit anthocyanin concentration. Experiments were conducted at East Nekoosa and Yellow River in 1997, East Nekoosa and Mather in 1998, and in Yellow River in 1999. Applications were made on 25, 19, and 24 Sept. 1997, 1998, and 1999 respectively. Fruit samples were hand raked from a part of the plot at 2 weeks after applications to determine the changes in fruit anthocyanin concentration. Additional samples HORTSCIENCE 40(1):127–130. 2004. Received for publication 17 Nov. 2003. Accepted for publication 23 Feb. 2004. This work was supported, in part, by Wisconsin Cranberry Board, Inc. and by the College of agricultural and Life Sciences, University of Wisconsin, Madison. We also thank Turkish Ministry of Education for their support of Dr. Mustafa Özgen for graduate training. Former graduate research assistant. Currently at University of Gaziosmanpasa, Department of Horticulture, Tasliciftlik Tokat, 60240, Turkey. Former graduate research assistant. Currently at Department of Horticulture, Faculty of Agriculture, University of Alexandria, Damanhour, P.O. Box 22516, Egypt. Graduate research assistant. Campbell-Bascom professor of horticulture. To whom reprint request should be addressed; e-mail [email protected].