This study added stevia leaf powder at ratios of 0.5, 1.0, 1.5, and 2.0 percent to Omija-pyun (Schisandra chinensis Jelly) as a natural low-calorie sweetener instead of sugar which is added to Omija-pyun in considerable amounts to evaluate quality characteristics and antioxidant activities compared to the control group with the addition of sugar. Moisture content of Omija-pyun expanded by increasing the measurement of stevia leaf powder (p<0.001), pH (p<0.01) and sugar content (p<0.001) decreased. L-values and b-values revealed a tendency to increase by adding more stevia leaf powder, but a-value revealed a tendency to decrease (p<0.001). Hardness (p<0.001) and chewiness (p<0.05) decreased by adding more stevia leaf powder. Based on the consumer preference evaluation, Omija-pyun with the addition of 0.5 percent stevia leaf powder was the most preferable in terms of color and flavor (p<0.001). The control group and Omija-pyun with the addition of 0.5 percent stevia leaf powder was the most preferable in terms of taste and texture (p<0.001). There were significant differences in the organoleptic properties except hardness between the samples by quantitative descriptive analysis. The control group revealed the highest preference in terms of redness and transparency, and redness and transparency tended to decrease by adding more stevia leaf powder (p<0.001). Organoleptic properties on bitterness and sourness were enhanced by adding more stevia leaf powder in the principal component analysis (PCA). Regarding antioxidant properties, total phenol compounds and flavonoid contents of Omija-pyun increased by adding more stevia leaf powder, and DPPH radical scavenging capacity also increased (p<0.001). Based on results, it is preferable to serve Omija-pyun with the addition of 1.0 percent stevia leaf powder instead of sugar within the context of quality and antioxidant activity.

In order to develop tea by using the leaves of stevia, which is a herbal plant, and to solve the disadvantages of stevia dried leaf tea, we have manufactured the steamed tea, stir-fried tea and fermented tea by changing the manufacturing processes. As a result of the sensory tests, the steamed tea, stir-fried tea and fermented tea received higher evaluations than the dried leaf tea. In terms of efficiency, it is desired that the total number of steaming and stir-frying is only once, but the fermentation is found to be the most desirable for 2 days. There are no trends for changes in the general ingredients, mineral and free amino acid contents of stevia leaf teas by different manufacturing processes. As a result for the measurement of antioxidant activities, the steamed tea and dried leaf tea did not show significant differences, but the stir-fried tea and the fermented tea show significantly low antioxidant activities as compared to the steamed tea. The contents of stevioside in both the stir-fried tea and the fermented tea were less than that in the dried leaf tea, but in the steamed tea, there was no significant difference in the content of stevioside. Base on the present observations, this study supports high potentials of steaming process in order to produce new stevia leaf tea.