Post-harvest retention of apple fruit firmness by 1-methylcyclopropene (1-MCP) treatment or dynamic CA storage with chlorophyll fluorescence (DCA-CF)

Over a period of 6 years, fruits of the six most commonly grown apple cultivars in Europe ('Braeburn', 'Cripps Pink', 'Fuji', 'Gala', 'Golden Delicious', 'Red Delicious') were harvested at the same site on 3 successive dates, at beginning, mid and end of the optimal harvest window (OHW), and stored in controlled atmosphere for 5 to 7.5 months under ULO (at 1 kPa O-2 and 1 or 1.5 kPa CO2) and/or CA (at 1.5 kPa O-2 and 1 or 1.3 kPa CO2) storage conditions with and without prior exposure to 1-MCP (SmartFresh (TM)). In addition, fruit samples were exposed to the novel DCA-CF storage technique with dynamic O-2 < 0.7 kPa level guided by chlorophyll fluorescence sensing. The fruit firmness differences obtained by means of 1-MCP or DCA-CF were compared using untreated ULO and/or CA-stored fruits as reference, directly after storage and also after a subsequent 'shelf-life' period of 7 days, at 20 degrees C. At the end of the storage period, results varied depending on the cultivar and the reference conditions. The highest efficacy of the more advanced storage techniques (1-MCP or DCA-CF), compared to ULO, in increasing fruit firmness was observed on the cultivar 'Golden Delicious'. Both techniques resulted in increased fruit firmness also on 'Braeburn', but on this cultivar DCA-CF storage proved to be more effective than the 1-MCP treatment. 1-MCP-treated and untreated 'Red Delicious' fruits were exposed to both reference storage conditions, CA and ULO. Only when fruits were compared to the sub-optimal CA storage condition, noticeable differences emerged, with both the innovative techniques providing a considerable increase in fruit firmness. On 'Cripps Pink', both, the 1-MCP treatment and DCA-CF storage, increased fruit firmness, while on 'Fuji' and 'Gala' firmness got only slightly increased in comparison to the reference storage condition (ULO). Among fruits harvested at different ripening stages no considerable differences in the gain of fruit firmness obtained by the means of the novel storage methods emerged, for none of the cultivars.