Abstract

Stevia plants are a good source of carbohydrates (61.93% d.w.), protein (11.41% d.w.), crude fiber (15.52% d.w.), minerals (K, 21.15; Ca, 17.7; Na, 14.93 and Mg, 3.26 mg/100 g d.w. and Cu, 0.73; Mn, 2.89; Fe, 5.89 and Zn, 1.26 mg/100 g d.w.) also essential amino acids were found in amounts higher than those recommended by FAO and WHO for adults as well as non- essential amino acids. Stevioside was extracted and purified from the dried Stevia leaves by three methods. The first one, extraction by hot water (65°C) at different ratios of leaves to water (1:15 - 1:75). The optimum ratio was 1:35 in which the maximum stevioside content was obtained (7.53%), recovery of stevioside was 80.21% and purity related to depigmentation was 97.56%. The second method, extraction by methanol at ratio 4:1 methanol/leaves and purification, recovery of stevioside was 94.90% and purity was 81.53%. The third method, extraction by mixture of methanol/water (4:1) and purification, recovery of stevioside and purity were 92.34 and 79.81%, respectively. Physical and chemical characteristics of the extracted stevioside were studied. Stevioside extractions were analyzed by HPLC in which the highest amount of stevioside (23.20%) was obtained in methanol extract. Also, organolyptic characteristics of extractions indicate that this sweetener has been applied as substitutes for sucrose in different drinks and baking products.

Key words: Stevia, stevioside, physico-chemical properties, extraction, natural sweeteners.