engleski

Glycosides content and mineral composition of stevia (Stevia rebaudiana Bertoni) leaves

Stevia belongs to the family Asteracae and the intensive sweet taste of its leaves provided the name „new age sugar“. The reason for such an intensive sweetness lies in chemical compounds called glycosides whose main characteristics are thermostability and the fact that it has zero calories. The subject of this research was to determine the glycosides (stevioside and steviol) content, and the mineral composition of stevia leaves. Plants were grown on acid soil type (pH 5.0) and fertilized with five doses (from 0 to 1.6 g per plant) of mineral fertilizer. Harvest was done on September 7th and samples of plant material were obtained. The content of total nitrogen was determined by CHNS-analyzer. The amount of H2PO42- as well as SO42-, K+, Ca2+ and Mg2+ was determined by ion chromatography, while the glycosides content was determined by electroanalytical method. Average stevioside content was 45.7 steviol equivalents (SE) per g of dry leaves and average steviol content was 115.4 SE per g of dry leaves. Average amount of total nitrogen was 15.93 g per kg of dry matter (DM). The amount of phosphate was between 1.98 and 2.88 g per kg DM, while sulphate had values between 3.18 and 5.64 g per kg DM. The amount of potassium ranged from 5.32 to 10.09 g per kg DM, calcium from 11.36 to 12.99 g per kg DM, while magnesium was between 8.61 and 10.75 g per kg DM. Content of stevioside and steviol as well as mineral composition of stevia leaves were affected by fertilization rate. The best quality of stevia leaves with the highest glycoside content was achieved by fertilization rate between 40 and 60 kg per ha.

stevioside; steviol; mineral content; total nitrogen; fertilization rate

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