Effect of oxidative deterioration on flavour and aroma components of lemon oil

Reactions of five major components (citral, alpha- and beta-pinene, limonene and gamma-terpinene) of lemon oil in the presence of Cu catalysts and air have been shown to lead to significant oxidation of alpha- and beta-pinene and gamma-terpinene, even when the catalyst concentration was comparable to that present in copper-plumbed tap water. Addition of commercial antioxidants (BHA and tocopherol) generally led to suppression of oxidation. UV degradation of these compounds in the presence of air was most significant for gamma-terpinene and limonene which gave products similar to those obtained from the Cu-catalysed thermal reactions. Citral gave different products, mainly photocitrals, in contrast to the thermal reactions. The sensitivity of lemon oil to temperature and the presence of air was confirmed. (C) 2008 Elsevier Ltd. All rights reserved.