Effect of diurnal variability and storage conditions on essential oil content and quality of damask rose (Rosa damascena Mill.) flowers in north western Himalayas

Field experiments were conducted at CSIR-Institute of Himalayan Bioresource Technology, Palampur, India to study the effect of diurnal variability and storage conditions of flower on oil content and composition of damask rose (Rosa damascena Mill.) during 2011. In this study, the rose oil was obtained by hydrodistillation in Clevenger type apparatus and the components in the oil were analyzed by GC/MS. The essential oil content and composition were affected by harvest time and storage conditions. The highest essential oil content (0.043%, v/w) was obtained from the rose flowers which were harvested at 04:00 am and the lowest (0.017%, v/w) from the flowers harvested at 02:00 pm. The percentage of citronellol+nerol, main components of rose oil, increased with delay in harvesting. Geraniol content (26.3%) was maximum when the flowers were harvested at 10:00 am, but after that there was significant reduction in its concentration upto 06:00 pm. Storage duration of flowers at different temperature also affected the oil content and composition. There was 8.5% and 27.6% reduction in oil content when the flowers were stored for 24h at 4°C, and 18±1°C or 25±1°C, respectively. Parallel to the increase of the storage time citronellol+nerol content increased. The rates of hexadecane, nonadecane and methyl eugenol in the flowers distilled immediately were determined to be lower than the stored flowers. The percentage of geraniol in the flowers distilled immediately were between 27.4% and declined to 4.4%, 6.9% and 18.1% after 24h of storage at 25±1°C, 18±1°C and at 4°C temperature, respectively. The optimal results in terms of its oil content and components were obtained from the rose flowers distilled immediately after the harvest compared to the flowers stored at 25±1°C, 18±1°C. However, at 4°C the flowers can be stored for 16h without much effect in oil content and composition.