Changes of the free and bound volatile compounds in Rubus corchorifolius L. f. fruit during ripening

The changes of free and bound volatile compounds in Rubus corchorifolius fruit during ripening were determined with a headspace SPME-GC-MS method. The results suggest that the free aldehydes, alcohols, esters and phenols increases, while that of free terpenoids decreases, with the ripening of the fruit. The bound aldehydes, alcohols, terpenoids, esters and phenols gradually decreases during ripening because these bound compounds are hydrolyzed to their free form. The characteristic free aroma compounds of ripened red fruit were found to be hexanal, 2-heptanone, ethyl hexanoate, 4-terpineol, geranial and methyleugenol. The free aroma compounds in red and yellow fruits exhibit similar odor profiles, and both of them are much sweeter, more floral and greener than the green fruit. The overall aroma of the fruits all ripening stages are mainly attributed to the free aroma compounds including beta-damascenone, hexanal, 2-hexenal and linalool. The formation mechanisms of some volatile compounds were proposed.