Changes of lemon flavor components in an aqueous solution during UV irradiation
1997
Iwanami, Y. | Tateba, H. | Kodama, N. | Kishino, K.
A lemon flavor composed of lemon oil, water (pH 6 phosphate buffer), and ethanol, and the lemon-flavored drink were irradiated with UV light. Citral (1 and 2), which is one of the most important components expressing the typical lemon-like odor, significantly decreased with Z-E isomerization and there appeared 2-(3-methyl-2-cyclopenten-1-yl)-2 methylpropionaldehyde (6), trans-1,3,3-trimethylbicyclo [3.1.0]hexane-1-carboxaldehyde (7), cis-1,3,3-trimethylbicyclo [3.1.0]hexane-1-carboxaldehyde (8), (1,2,2-trimethyl-3-cyclopenten-1-yl) acetaldehyde (9), alpha-campholenealdehyde (10), photocitral A (3), epiphotocitral A (4), and photocitral B (5). New compounds of aldehyde 9, 6 and 10, were newly identified as photoreaction products of citral. Limonene, terpinolene, and nonanal decreased, while p-cymene increased after UV irradiation. Other components, such as sesquiterpene hydrocarbons, citronellal, linalool, and terpineols, were only 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.
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