Reaction mechanisms for volatiles responsible of off-odors of fresh cut melons

The aim of this study was to identify the main volatiles responsible of odor imbalance of fresh-cut melons stored in modified atmosphere packaging at different temperature and to propose reaction mechanisms to model the effect of temperature on the changes on some of them. Fresh harvested melons were cut and packaged in PP-PE PP+PE bags in passive modified atmosphere (MAP) and stored over 9 days at 3 different temperatures 0, 5 and 15°C. Sensorial evaluation of off-odor and volatile analysis were carried out. As concerns volatile compounds, 48 volatile organic compounds (VOC) were identified in the headspace of all homogenized samples, including 16 acetates and 18 non-acetate esters, 4 sulfur-containing compounds, 5 alcohols, 4 aldehydes, and 1 ketone. Beyond a general volatile compound depletion, greater under MAP at 5 and 15°C, the increase of some VOCs were observed with the time, which did not concern only fermentation related compound, such as ethanol and ethyl acetate, but also flavor-related compounds as the ethyl(methylthio)acetate. For these compounds, consecutive reaction mechanisms were proposed, which were capable to model the changes of ethyl(methylthio)acetate, and ethanol and ethyl-acetate, with R2adj.=93.29 and 96.02%, respectively.