Effect of Drying Method on Spearmint (Mentha spicata var. Viridis L.) Oil Content and Physicochemical Properties

The experiment was investigated the effect of drying method of spearmint oil content and physicochemical properties. Spearmint samples were dried under different conditions till the weight of herb in each reached 20%. The treatments were: (i) shade drying under ambient conditions, (ii) sun drying (iii) forced-air oven drying at 60 o C, (iv) forced-air drying at 70 o C and (v) forced-air oven drying at 80 o C. Oil was extracted by water distillation according to the technique of the British Pharmacopoeia. Physicochemical properties were determined according to British Standards Institute. Spearmint oil content was significantly higher in shade drying than in sun drying and in forced-air oven drying. Oil content decreased with an increase in oven temperature. Refractive index and acid value were significantly higher in shade drying, compared with sun drying and decreased with an increase in oven temperature in forced air drying. Ester value of spearmint oil followed a trend, but opposite to that of acid value.