Changes in the Composition and Content of Volatile Constituents in Peach Fruits in Relation to Maturity at Harvest and Artificial Ripening.

Abstract

Changes in the composition and amounts of volatile constituents in white peach cv. Hakuho before and after artificial ripening, were investigated in fruits picked at three different maturity stages, in order to determine the optimum time for harvest in relation to some quality attributes. 1. Based on the color-chart value, firmness, Brix degree and titratable acidity, it was found that the eating quality of the fruits picked at the stages referred to as •ghard mature•h and firm mature•h was acceptable after fruit had been ripened for 4 days at ambient tempera- •g ture. After the same time, fruits of the •gsoft mature•h stage were considered to be overripe. 2. Typically, for peaches of all three maturities the volatile concentrates were separated into 89 or more peaks by capillary gas chromatography, of which 33 were identified by gas chromatography-mass spectrometry, The most abundant constituents were C6 aldehydes, C6 alcohols and C6~C12 lactones. 3. The total amounts of the 33 volatile constituents, which were identified at harvest and at all stages of fruit maturity, decreased rapidly after ripening for 4 days at ambient temperature. This decrease in the total amount of these volatile constituents was mainly a result of the reduction in the amount of aldehydes and alcohols which generated the •ggreen aroma•h. 4. Eleven kinds of C6~C12 lactonic compounds were detected at all the stages of maturity, and ƒÁ-decalactone was a major constituent accounting for about 40% of the total lactonic compounds. The content of almost all the lactones increased with advancing fruit maturity and during ripening. 5. Based on the evaluation of the odor threshold, it was calculated that the increase in odor units of ƒÁ-lactones made an important contribution to the •gfruity aroma•h with advancing maturity, in contrast to the decrease of the C6 compounds which were responsible for the •ggreen aroma•h. 6. The most suitable picking time based on the changes in the composition and amount of volatile constituents corresponded to the firm mature stages followed by artificial ripening for 4 days including postharvest handling.