Research NoteNovel 1-methylcyclopropene immersion formulation extends shelf life of advanced maturity ‘Joanna Red’ plums (Prunus salicina Lindell)
Introduction
Plum cultivars are highly perishable, characterized by short postharvest life when exposed to room temperature (shelf life) after cold storage due to decay, incidence of chilling injury (CI) symptoms and fast softening. Furthermore, sensory evaluation studies in plums recommended that in order to increase fruit flavor, and therefore consumption, plums should be harvested at more advanced maturity, when better quality characteristics have developed (Crisosto et al., 2004). So, reduction of fast softening should be avoided during postharvest handling to protect fruit quality and increase shelf life of delayed harvested fruit.
1-Methylcyclopropene (1-MCP), a strong blocker of ethylene receptor, is being used as a tool to further investigate the role of ethylene in ripening and senescence, and as a potential commercial tool to maintain product quality (Sisler and Serek, 2003; reviewed in Blankenship and Dole, 2003 and Watkins, 2006). 1-MCP has been reported to be particularly effective in delaying plum softening. However, its efficacy and dose is related to plum cultivar (suppressed-climacteric versus climacteric fruit types), as well as to temperature treatment (reviewed in Watkins, 2006).
1-MCP is being distributed commercially as a cyclodextrin powder formulation that needs to be mixed in enclosed areas with warm water or a buffer solution that releases 1-MCP into the air of the storage room, making it quite complicated to apply. The need to explore nonvolatile and nontoxic compounds that will counteract ethylene without a closed system in order for ethylene inhibitors to become a much more versatile tool has been pointed out (Sisler and Serek, 2003, Sisler, 2006) and recently some data regarding the efficacy of sprayable 1-MCP on maturity and quality of apple fruit at harvest and after storage have been reported (Watkins et al., 2006).
In this study, a range of concentrations of a novel 1-methylcyclopropene immersion formulation was tested on ‘Joanna Red’ plums at an advanced stage of maturity. Ripening related changes were determined in fruit after immersion and immediate ripening, and also in fruit ripened after a cold storage period that simulated standard domestic distribution. The selected cultivar represents a group of plums with low susceptibility to CI, but a short shelf life (fast ripening).
Section snippets
Materials and methods
Plum fruit (Prunus salicina Lindell, cv. Joanna Red) were harvested at advanced maturity (∼30 N firmness) from a commercial orchard in the Fresno area (Central California, USA). Treatments included immersion for 5 m in water at 20 °C (control) and in water solutions of the formulation AFxRD-038 (Rohm & Haas Co., Spring House, PA) at four 1-MCP concentrations (10, 100, 1000 and 10,000 ng kg−1) with a wetting agent (Nu-Film P, 0.1%, Miller Chemical & Fertilizer Corp., Hanover, PA, USA) for maximum
Results and discussion
Skin color change from red to dark black during ripening was delayed in all fruit treated with 1-MCP concentrations equal or higher to 100 ng kg−1 (Table 1), as has been previously reported by other researchers in plums (Martínez-Romero et al., 2003, Valero et al., 2003). A similar situation occurred on fruit cold stored prior to ripening. However, in this case all fruit were darker than fruit immediately ripened, indicating some fruit darkening occurred during the 10 d cold storage period prior
Conclusions
Concentrations of 100–1000 ng kg−1 1-MCP were sufficient for extending the shelf life of advanced maturity ‘Joanna Red’ up to 5 d, whereas 1000–10,000 ng kg−1 1-MCP may extend it even longer including cold storage without inducing CI symptoms. Delayed harvest (tree ripened) combined with immersion in 1-MCP is suggested as an excellent technique to assure tasty fruit and extend plum shelf life. As cold storage period did not affect 1-MCP performance, this 1-MCP immersion formulation treatment in
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