1-Methylcyclopropene Increases Storability and Shelf Life in Climacteric and Nonclimacteric Plums DOMINGO MARTI ÄNEZ-ROMERO, ² EVE DUPILLE, § FABIA Ä N GUILLE Ä N, ² JUAN M. VALVERDE, ² MARI ÄA SERRANO, ‡ AND DANIEL VALERO* ,² Department of Food Technology, and Department of Applied Biology, EPSO, University Miguel Herna ´ndez, Ctra. Beniel km. 3.2, 03312, Orihuela, Alicante, Spain, and Bioterra Agroconsulting, S.L. 08010, Barcelona, Spain The effect of 1-methylcyclopropene (1-MCP) at three different doses (0.25, 0.50, and 0.75 μLL -1 ) on the ripening processes of a climacteric, cv. Santa Rosa, and a suppressed climacteric type, cv. Golden Japan, plum was studied. For both cultivars, positive effects were observed in terms of inhibition of ethylene production and delays of the physical, chemical, and biochemical changes associated with ripening. 1-MCP-treated plums were firmer with lower weight loss, reduced °Brix/titratable acidity ratios, and lower color changes during cold storage and subsequent shelf life at 20 °C than controls. For most factors, the effectiveness of 1-MCP was dose-dependent in Santa Rosa but dose- independent for Golden Japan. KEYWORDS: 1-MCP; ethylene; firmness; ripening index; plum ripening; postharvest storage INTRODUCTION The plum has been categorized as climacteric fruit, with increases in both ethylene and respiration rate during ripening. However, this is not a general behavior, since some cultivars such as Golden Japan, Shiro, and Rubyred show a suppressed climacteric pattern, while Santa Rosa, Gulfruby, and BlackStar behave as typical climacteric fruits (1-3). Plums are highly perishable and require special care during handling and storage, although suppressed climacteric cultivars have longer shelf lives than climacteric ones (4). 1-Methylcyclopropene (1-MCP) is a nontoxic antagonist of the ethylene hormone that binds to the ethylene receptor after treatment (5). 1-MCP has been extensively used on fruits at the experimental level in order to understand the mechanisms controlling the physiology and biochemistry of the ripening processes, and the effect of 1-MCP in delaying ripening has been studied on climacteric and nonclimacteric fruits (6, 7). In most of these studies, the treatments were performed at ambient temperature, and most of the times, only delays at the onset of the ethylene production were achieved, but total inhibition was not observed. 1-MCP is commercially used in cut flowers and apples while its use in other fruits and vegetables is still being investigated. The aim of this work was to study the effect of 1-MCP in two plum cultivars: Golden Japan, which is considered as a nonclimacteric phenotype, and Santa Rosa, which behaves as a climacteric fruit. 1-MCP treatments at different doses (0.25, 0.50, and 0.75 μLL -1 ) and at low temperature in already cooled fruits were performed, and ethylene production, respiration rate, firmness, color, and °Brix/ titratable acidity ratio were analyzed during cold storage and further during shelf life. Also, the ethylene dependence on these parameters and the possible application of 1-MCP on delaying the ripening process and increasing storability and shelf life of plums are discussed. MATERIAL AND METHODS Plant Material. Plum fruits (Prunus salicina Lindl., cv. Golden Japan and cv. Santa Rosa) were harvested at the commercial ripening stage from 10 year old trees grown in an orchard in Murcia (Spain). For both cultivars, over 3500 fruits were manually picked, to avoid mechanical damage, and once in the laboratory, they were selected according to size and color, randomized, and divided into 147 lots of 20 plums. Three lots were used to analyze the fruit properties at harvest (day 0). Four groups of 36 lots were used for 1-MCP treatments in triplicate: 0 (control), 0.25, 0.50, and 0.75 μLL -1 (see 1-MCP Treatment). After treatments, plums were stored at 1 ( 0.5 °C, in permanent darkness and with a relative humidity of 90%. The schedule of sampling was as follows: 1 day after treatment and then weekly for 5 weeks. Six lots were sampled for each treatment; three lots were analyzed immediately, and three lots were stored at 20 °C for 4 days to evaluate shelf life and to determine ethylene, respiration rate, weight loss, color, firmness, and °Brix/titratable acidity ratio. 1-MCP Treatment. Fruits were precooled at 1 °C for 6 h before treatments. SmartFresh (0.14%) was supplied by AgroFresh Inc. (Rohm and Haas Inc., Gessate, Italy) as a powder, which after warm water (40 °C) was added, released 1-MCP as a gas. Different amounts of the powder (in triplicate) were weighed, and suitable amounts of warm water were added to obtain stock solutions of 1-MCP in a sealed glass * To whom correspondence should be addressed. Fax: 34-96-6749677. E-mail: daniel.valero@umh.es. ² Department of Food Technology, University Miguel Herna ´ndez. ‡ Department of Applied Biology, University Miguel Herna ´ndez. § Bioterra Agroconsulting. 4680 J. Agric. Food Chem. 2003, 51, 4680-4686 10.1021/jf034338z CCC: $25.00 © 2003 American Chemical Society Published on Web 07/04/2003