The effectiveness of a long-term storage of apples is dependent on the term of harvesting. Too early picked fruits do not get appropriate cultivar size, color, taste and aroma, and later picked fruits are not stable due to the aging process and premature loss of firmness during their storage.
Change in ground color (from green to yellow) during ripening of apple fruit takes place as a result of the degradation of chlorophyll in the skin, the intensity of which depends on the level of endogenous ethylene in fruits, synthesis of anthocyanins and carotenoids. Flesh firmness is the main indicator of assessing apples quality, so its maintaining during storage and marketing is a priority issue. The fruits of “hard” cultivars have to be on the market with a flesh firmness of at least 5.5-6.0 kg/cm2. In conditions of higher temperature after the shipment from the cold storage room the firmness will be lost faster, so immediately after the storage the level of this parameter has to be 1.0 kg/cm2 higher.
The design of a fruit orchard (rootstock) considerably influences the color and firmness change during pre-harvest ripening of fruits and during their storage. Maintaining of firmness and inhibition of apple ripening during storage of fruits harvested from orchards of different designs is achieved by a post-harvest treatment with ethylene inhibitor 1-methylcyclopropene (1-MCP).
The changes of flesh firmness and ground color (by means of reflected light) of cv. Reinette Simirenko apples picked in two terms 3 – with the onset of harvest maturity (mass picking) and in a week (late picking) from intensive orchard on dwarf (M.9) and traditional orchard on semi-vigorous (MM.106) rootstocks were investigated. Cooled to 5 °C fruits were treated with 1-MСP and preserved up to seven months at the temperature of 2 ± 1 °C and relative air humidity of 85-90% (control fruits without treatment).
The ground color of the skin was determined with spectro-colorimeter «Spekol» by measuring the reflection of light on the wave of 675 nm, which is typical for chlorophyll absorption. Flesh firmness was determined with penetro-meter FT-327 having plunger diameter of 11mm (peel was removed before the measurement).
It was found that the flesh firmness of cv. Reinette Simirenko apples from orchards on M.9 and MM.106 rootstocks (without 1-MСP treatment) at the end of a seven-month storage period was 5.8-6.2 kg/cm2, regardless of the harvesting time, and it is below the minimum parameter of 6.5 kg/cm2, which is set for supplying apples into supermarkets. Postharvest 1-MCP treatment ensures 2.5-3.1 kg/cm2 higher firmness of fruit harvested from orchards of both types (at the end of a seven-month storage period) regardless of picking time, which is 1.3 times higher than the minimum level specified for shipment. Index for untreated apples of delayed picking from intensive orchard was limited to a six-month storage, and for the fruits of mass picking from intensive orchard (M.9) and two picking periods from traditional orchard (MM.106) was limited to a four-month period of storage.
After seven-month storage the level of light reflection at 675 nm wave length (degree of yellowing) was lower for the untreated fruits from traditional orchard and for 1-MСP treated fruits of mass collection from the intensive orchard. Under postharvest 1-MCP treatment the level of indicator was 9.6-11.7% lower for apples from the intensive orchard and 4.3-5.1% lower for fruits of both picking dates from traditional orchard (compared to untreated fruits).
Key words: Reinette Simirenko, 1-methylcyclopropene, Smart Fresh, rootstock, harvest date, storage, flesh firmness, reflection of light.