Production, Characterization and Optimization an of Stevia Sweetener from Stevia Leaf
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Date
2014-11
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Addis Ababa University
Abstract
This study has been carried out to extract the stevia sweetener, sugar substitute, from the leaf of
stevia plant. Solvent extraction of the leaf using hot water was investigated. The main and
interaction effects of temperature, extraction time and material ratio (stevia leaf: water) were
examined. In the main effects investigation all the main factors had a significant effects on the
yield of stevia sweetener. But in the interaction effects, only temperature with material ratio and
extraction time with material ratio had a significant effect on the yield of the sweetener. The
interaction effects of temperature with extraction time (residence time) had no any significant
effects on the yield of stevia sweetener. The two factor interaction model was developed. In this
model the term which had no significant effects had been reduced. This term was the interaction
effect of temperature with residence time (τβ)ij. Different analysis of the data such as analysis of
the variance, hypothesis testing and predicted R-squared also enforce this idea. The p-value was
0.1270 which was greater than type one error 0.05. The F-calculate for this term was 1.74 that
was less than F-tabulate 1.90. The predicted R-squared was 60.10% that was far from the
adjusted R-squared 87.49%. These different analysis leads to the reduction of the interaction
effect of temperature with residence time from the model. The model adequacy also investigated
by normal probability plot of residuals and plot of residual verses predicted value. Both normal
probability plot as well as residual verses predicted value plots showed that the model was
acceptable. Optimum conditions for the extraction process were optimized. The optimal
treatments of each factor to maximize the yield were, for the temperature 50oC, three hours for
the extraction time and 1:10 material ratio. The maximum yield that was obtained at these
optimum conditions was 49.90 %. The two methods report form and ramp form of optimization
showed the same result or the same conditions.
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Process Engineering Stream