Author(s): Aytolgn Melese*, Getachew Abebe, Abedella Befa, Girma Moges, Basazinew Degu
Rosemary (Rosmarinus officinalis L.) is an attractive, evergreen, highly branched aromatic medicinal plant. It is used to roast meats, fish, potato salads to prevent food poisoning, spice for the preparation of food ingredients for pea mash, and pepper powders, traditional medicines and cosmetics in Ethiopia. Information about proper harvesting age and drying methods of this international valuable plant is essential. The objective of this study was evaluating the effect harvesting age and drying method on the essential oil content of rosemary leaves. The experiment consisted of three levels of harvesting ages (6, 12, and 18 MAT and four levels of drying methods (fresh, sun, shad, and oven) in a randomized complete design with three replications. The data were statistically analyzed using analysis of variance and values of least significant difference at 5% using SAS. The highest essential oil contents (0.959%, 2.289%, 0.84%, 2.01%; 0.8392%, 2.138%, 0.741%, 1.88%); while the lowest (0.5517%, 1.34%, 0.5017%, 1.2167%) obtained from 6, 12 and 18 MAT respectively. Therefore, harvesting age had a significant effect on the percentage change (53.94%, 52.3%, 50.42%, 49.05%; 41.34%, 45.86%, 38.48%, 43.05%) essential oil content increments were observed from 12 and 18 MAT when compared to 6 MAT, respectively. Drying methods has significant effects on essential oil contents (0.899%, 2.25%, 0.807%, 2.02%; 0.848%, 2.09%, 0.74%, 1.82%), while the lowest (0.689%, 1.702%, 0.6144%, 1.46%, 0.698%, 1.646%, 0.6156%, 1.504%) was obtained from fresh, shade, sun and dried leaves respectively. Therefore, drying methods had significant effects on the percentage change in essential oil content during the drying when compared with fresh (26.45%, 27.72%, 27.119%,31.94%; 25.19%, 30.22%, 26.87%, 29.31%, and 5.85%, 7.32%, 8.62%, and 10.41%) from oven, sun and shade-dried leaves respectively. The interaction of harvesting age and drying methods had a highly significant (p 0.05) influence on the essential oil content.
