Analysis of Volatile Components and Phenols from Peels of Two Lemon Cultivars during Fruit Ripening

This study aimed to determine changes in volatile components and phenols from lemon peels at different ripening stages. Volatile components in the peels of two disease-resistant cultivars, ‘Xiangshui’ and ‘Taichui’ during fruit ripening were determined by solid-phase microextraction (SPME) coupled with gas chromatography-mass spectrometry (GC-MS), and phenols by high-performance liquid chromatography (HPLC). Results showed that a total of 86 volatile components were identified, mainly including terpenes, aldehydes and alcohols, with sesquiterpenes and aldehydes being the predominant ones in the peel of ‘Xiangshui’ lemon, and monoterpenes and alcohols being the major ones in the peel of ‘Taichui’ lemon. The contents of monoterpenes and sesquiterpenes in the peel of ‘Xiangshui’ lemon decreased first, then increased and then decreased, whereas the contents of aldehydes gradually increased. The contents of all three aroma compounds in the peel of ‘Taichui’ lemon decreased first and increased subsequently. In addition, 26 and 22 characteristic aroma components were observed in the peels of ‘Xiangshui’ and ‘Taichui’ lemon, respectively, based on their odor activity values (OVA). Decanal, dodecanal, geranial, linalool and neral were the most important contributors to the aroma quality of ‘Xiangshui’ lemon peel. Decanal, linalool, citronellal, β-myrcene and citronellyl acetate were the most important contributors to the aroma quality of ‘Taichui’ lemon peel. Totally 12 and 15 phenolic compounds were detected in the peels of ‘Xiangshui’ lemon and ‘Taichui’ lemon, respectively. The total content of phenolic acids was not obviously different between the two samples, while the total content of flavonoids in the peel of ‘Taichui’ lemon was significantly higher than that in ‘Xiangshui’ lemon, with a 20.94 to 118.75-fold increase being observed in the content of polymethoxylated flavones. The contents of total phenolic acids and total flavonoids in the peels of both cultivars decreased with ripening. The results of this study provides support for the utilization of lemon fruit and the development of new disease-resistant germplasm resources.