Color, Chlorophyll Fluorescence and Volatile Production In Banana Fruit Ripened at High Temperature

Banana fruit (Musa AAA group) is the most consumed fruit in the world. Banana fruit quality is depended on color, flavour (aroma and taste), sweetness and nutritional compounds. The physiological and biochemical changes that occur in both peel and pulp tissues during ripening have been described. The peel tissue of banana plays an important role in banana fruit ripening including coloring, softening, starch degradation and volatile biosynthesis. It has been reported that color formation and chlorophyll breakdown I banana is inhibited by ripening temperatures above 24°C due to the possible retention of thylakoid membrane at a higher temperature that results in reduced chlorophyll degradation. In this study, green, untreated fruit were obtained from a local whole-sale market and half of the fruit were subjected to ethylene treatment at 10 µl/L for 24 hours. After ethylene treatment, fruit were stored at 20 or 31°C for 7 days. During this period, fruit were sampled at 0, 1, 4 and 7 days and evaluated for color, chlorophyll fluorescence, volatile production and gene expression. The investigation was repeated four times. Significant reduction of coloring from green to yellow at high temperature was shown. High temperature storage at 31C reduced yellow color development. Chlorophyll fluorescence of high temperature treated fruit has the highest of Fo and lowest Fv/Fm, indicating a possible heat stress of the fruit. The rapid decline of Fo and Fm in ethylene treated fruit stored at 20°C showed their close relationship with peel yellowing. A total of 22 volatile compounds were identified using SPME/GC/MS. Total volatile production increased at high temperature but was not affected by ethylene treatment. Production of 3-methylbutyl butanoate, butyl 3-methylbutanaote and heptyl 2-methylbutanoate increased similarly to total volatile production in response to ethylene treatment and high temperature,  whereas ethyl acetate, 2-methylpropyl acetate and 3-methylbutyl acetate were induced by high temperature. Expression of four ripening and senescence related genes are also shown.