Evaporation of Spearmint (Mentha spicata var. viridis L.) Herb Oil during One Year of Storage under Semi-Arid Condition

Abstract

The experiment investigated evaporation of essential oil of stored spearmint herb under ambient temperature during one year of storage, in Sudan semi-arid conditions to study oil content per year months, seasons and evaporation rate. Spearmint herb samples were dried under shade for seven days and kept in polyethylene bags and stored at ambient room temperature. Spearmint oil was extracted by water distillation using the technique of British Pharmacopoeia; the oil determined initially after seven days of drying before storage and then every month for 12 months. Losses of oils under Sudan semi-arid seasons recorded and the rate of evaporation calculated with respect to changes per month. The results showed that the essential oil content progressively decreased during storage of spearmint herbs from 1.3 ml/100g initially and end by 0.1 ml/100 g after 12 months of storage. The oil content rate show a decreased by 0.1 ml/100 g every month during the first five months (January-May) of winter season; then decreased by 0.2 ml/100 g per month during hot summer (May-June); and negligible decease during rainy autumn season (July-August), after which the oil decreased by 0.1 at late hot dry summer (September – October) and the experiment end by a decreased of 0.05 ml/100g every month during the last storage period at beginning of winter (November -December).