CHANGES OF LEMON FLAVOR COMPONENTS IN AN AQUEOUS-SOLUTION DURING UV IRRADIATION

A lemon flavor composed of lemon oil, water (pH 6 phosphate buffer), a nd ethanol, and the lemon-flavored drink were irradiated with UV light . Citral (1 and 2), which is one of the most important components expr essing the typical lemon-like odor, significantly decreased with Z-E i somerization and there appeared 2-(3-methyl-2-cyclopenten-1-yl)-2-meth yl (6), 3,3-trimethylbicyclo[3.1.0]hexane-1-carboxaldehyde (7), 3,3-tr imethylbicyclo[3.1.0]hexane-1-carboxaldehyde (8), (1,2,2-trimethyl-3-c yclopenten-1-yl)acetaldehyde (9), alpha-campholenealdehyde (10), photo citral A (3), epiphotocitral A (4), and photocitral B (5). New compoun ds of aldehyde 9, 6 and 10, were newly identified as photoreaction pro ducts of citral. Limonene, terpinolene, and nonanal decreased, while p -cymene increased after UV irradiation. Other components, such as sesq uiterpene hydrocarbons, citronellal, linalool, and terpineols, were on ly slightly changed. These results suggested that citral is a more UV- unstable component in lemon flavor and the photolysis of citral could affect other components in lemon flavor during UV irradiation.