Characterization of changes in 'Gala' apple aroma during storage using osme analysis, a gas chromatography-olfactometry technique

Changes in the odor-active volatile compounds produced by 'Gala' apples [Malus >sylvestris (L.) Mill. var. domestica (Borkh.) Mansf, 'Gala'] were measured after 4, 10, and 20 weeks storage at I UC in regular atmosphere (RA) or controlled atmosphere (CA), and 16 weeks in CA followed by 4 weeks in RA, Aroma was evaluated using the gas chromatography-olfactometry method Osme. Production of volatile esters decreased along with corresponding fruity aromas during CA storage. Hexyl acetate, butyl acetate, and 2-methylbutyl acetate were emitted in the largest amounts and perceived with the strongest intensities from RA-stored fruit. While hexyl acetate and butyl acetate concentrations and aroma intensities decreased during CA storage, 2-methylbutyl acetate remained at the RA concentration until apples had been stored 16 weeks in CA. Perception intensities of methylbutyrate esters with apple or berrylike odors decreased less than straight chain esters in CA-stored fruit. 4-Allylanisole, beta -damascenone, and 1-octen-3-ol, as well as an unknown compound with a watermelon descriptor, were perceived more in RA-stored fruit than in CA-stored apples. Factor analysis indicated the importance of these compounds in 'Gala' apples stored 4 weeks in RA. Even though these compounds do not have an apple odor, they contribute to fresh 'Gala' aroma.