Variation of essential oil yield and composition of Citrus aurantium var. amara

A study on the yield and the composition of bitter orange essential oils (Citrus aurantium L.), was carried out to point out possible variations related to provenance and collection time. Fruits and leaves were sampled monthly from trees of four bitter orange provenances which were Chanian, Brazilian, Corsican, and Roxani. Flower oil samples were obtained in April from open blossoms and were analysed by GC and GC/MS. Regarding the oil yield, quantitative variations among the different sampling periods and the examined provenances were recorded: highest leaf and peel yields were obtained in November and January, respectively. Roxani provenance showed the highest and lowest mean yield in peel (1.09) and leaf oil (0.68) respectively. Brazilian and Corsican provenance showed nearly the same yield. Twenty-seven compounds were identified in the essential oils analysed. Both qualitative and quantitative differences were observed between peel, leaf, and flower essential oils. Considering the quantitative differences, bitter orange oil was characterised by high limonene content (reaching 93 in Brazilian provenance), while petitgrain was characterised by high linalool and linalyl acetate content (reaching 26.32 and 37.40 respectively, in Roxani provenance); neroli oil was also characterised by a high concentration of b-pinene, limonene linalool, farnesol, and linalyl acetate (reaching 11.08, 8.18, 30.07, 7.43 and 12.51 respectively, in Brazilian provenance). Concerning seasonal variation of the quantitative composition of peel bitter orange and petitgrain oils, the maximum concentration of limonene was registered in mature fruits. The highest quantity of esters was observed in November and December while the lowest was recorded in April and May. In order to examine the variation in the essential oils, a comparison between the Greek and the Tunisian neroli and petitgrain oil was carried out. The latter was characterised by a high percentage of linalool (38.81) and a-terpineol (11.67).