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

Abstract

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.