Effect of Ethyl Acetate on the Defatting of Leaves in the Extraction of Stevia rebaudiana Bertoni.

Research background: The process for producing purified steviol glycosides from Stevia rebaudiana leaves (stevia) generally involves pretreatments, extraction, purification and crystallization. Pre-extraction or defatting can sometimes be a part of this process. It can remove impurities of low polarity, such as chlorophyll and fatty compounds. Nonpolar solvents can be used to defat stevia leaves.

Experimental approach: In this study, we investigated ethyl acetate as a pre-extraction solvent for the defatting of dried and crushed stevia leaves. We compared pure ethyl acetate and water-saturated ethyl acetate as pre-extraction solvents in percolation extraction. We then evaluated the effects of pre-extraction on the concentration and purity of the extracts obtained with ethanol/water solvents.

Results and conclusions: The recovery of nonpolar solvents was 2.3-3.9 % in pure ethyl acetate and 3.4-4.5 % in water-saturated ethyl acetate (from 40 to 60 °C). A low steviol glycoside loss can occur only with water-saturated ethyl acetate (on dry mass basis <0.5 %). In the Soxhlet extraction, the obtained yields were 8.43 with pure ethyl acetate and 10.44 % with water-saturated ethyl acetate. The steviol glycoside loss in the Soxhlet extraction was 10.70 % with water-saturated ethyl acetate. Defatted and non-defatted leaves were extracted with two ethanol/water solvents. Comparison of the results showed higher concentrations of glycoside in the pretreated leaves.

Novelty and scientific contribution: The pre-extraction with ethyl acetate followed by the extraction with ethanol/water solvent lead to a higher concentration of steviol glycosides and a higher purity of the extracts. Ethyl acetate can be used as a pre-extraction solvent for the defatting of stevia leaves in the industrial production of this sweetener.