Drying temperature and storage period and their relation to stevia leaf chemical composition

الملخص EN

Stevia (Stevia Rebaudiana Bertoni) is a herbal plant with increasing attention due to its high potency sweetener worldwide.

Nevertheless, its leaves are highly moisten and are susceptible to rapid degrade.

Therefore, two field experiments were carried out at the experimental farm, Sakha Agric.

Res.

Station in Kafr El-Sheikh-Governorate, Egypt in 2017 and 2018 seasons, to study the effect of drying temperatures (60, 70, 80 and 90 °C) in addition to shade drying and storage period (one, two, three and four months) compared to the control (after harvest directly) on quality of stevia leaves.

All combination treatments were allocated in randomized complete block design (RCBD) in three replications, where one cut (one harvest) was taken after 5 months from planting to determine the i.

e.

stevioside%, rebaudioside% rebaudioside/ stevioside ratio, carbohydrate content and weight loss during storage (storability) as well as correlation coefficient during both seasons of 2017 and 2018.

The most important results showed that Increasing drying temperature to 90 °C positively significantly affected;(p≤0.05) stevioside, rebaudioside and carbohydrate percentages.

However decreased both the ratio between rebaudioside/stevioside and weight loss of leaves was obtained during both seasons.

All storage times, significantly (p≤0.05) decreased values of all studied characters during storage up to four months during the both seasons.

Correlation coefficients indicated significant positive correlation ones among stevioside and rebaudioside and ratio of rebaudioside/ stevioside and carbohydrate%; however, storability recorded negative significant correlation with other characters under study in the both seasons