Investigation with the biochemical variation of stevia leaves affected by cultivation location and packing type.

Stevia is a valuable medicinal plant. However, after the introduction of this plant as a natural sweetener without calories, rose to fame in the world. Recent years with the increasing number of patients with diabetes and obesity problems in Iran as well as favorable conditions for growing this plant in the country, demand for use of the plant has been increased. Important step after medicinal plant cultivation is proper planning for its processing and packaging. The aim of this study was to evaluate the effect of growing region and type of packaging on the biochemical compounds is Stevia plant.

A research was designed concerning the effect of growing region and the type of packaging, on the stevia dried leaves quality, based on the completely randomized factorial design with four replications. For this purpose, leaf samples collected from both Gorgan and Aghghala, two wet and semiarid lands, respectively. The harvested leaves were dried under shad conditions. Dried leaves were kept for three months in different packages including glass, plastic, paper and foam materials. Finally, the visual quality of samples and the variation of chemical compounds were investigated and the measured traits including total phenol (Folin Ciocalteau), total flavonoids the colorimetric method using aluminum chloride, antioxidant activity (DPPH), total sugar and reduced sugar (Fehling).

Analysis of variance showed that the highest antioxidant activity as well as the highest total sugar content was observed in the leaves of Aghghala area. This difference was statistically significant compared to Gorgan. Total phenols, flavonoids and reduced sugar were not affected by growing region. The highest antioxidant activity was observed in the samples stored in glass. The highest reducing sugar accumulation was observed in the samples which were stored in paper and plastic bags. The amount of reducing sugar in the paper and plastic packages was in the in its highest value. The investigated packages did not show significant difference in the total phenol and flavonoid contents as well as total sugar. The interaction effect between growing region and packaging type on the antioxidant activity, total sugar and reduced sugar showed a significant difference. As the plant samples collected from Aghghala region in which packaged in glass showed the highest antioxidant activity.

According to the results, stevia which gathered from Aghghala region biochemically was more potent than the plants which were cultivated in Gorgan. It has been showed that dried leaves of stevia which were stored in glass had the highest antioxidant activity. Thus it recommended that, for long term storage especially for home usage, the dried leaves of stevia stored in glass containers.