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Clarification of Stevia rebaudiana (Bert.) Bertoni extract by adsorption in modified zeolites
Élida de Paula Moraes and Nádia Regina Camargo Fernandes Machado*
Departamento de Engenharia Química, Universidade Estadual de Maringá, Av. Colombo, 5790, 87020-900, Maringá, Paraná, Brasil. *Author for correspondence.

ABSTRACT. Selective adsorption on zeolites X and A was studied with Steviarebaudiana (Bert.) Bertoni (Asteraceae) extract clarification. Ionic exchanges were made with calcium and barium ions in zeolites NaX and NaA and the effect of contact of aqueous extract of dry Stevia rebaudiana Bertoni leaves with CaX, BaX, CaA and BaA zeolites was evaluated. Stevia extract in contact with the zeolite CaX showed highest clarification and did not present alterations of initialcharacteristics in concentration, glycosides and flavor. In batch tests at room temperature, the contact of Stevia aqueous extract and CaX zeolite provided 70-80% clarification. Since zeolite may be reused, an approximate clarification of 65-70% is possible in regenerated zeolite.
Key words: clarification, Stevia rebaudiana Bertoni, CaX zeolite, selective adsorption.

RESUMO. Clarificação de extrato deStevia rebaudiana (Bert.) Bertoni por adsorção em zeólitas modificadas. No presente trabalho, foi estudada a adsorção seletiva do extrato de Stevia rebaudiana (Bert.) Bertoni (Asteraceae) nas zeólitas X e A. Foram feitas trocas com íons de cálcio e bário nas zeólitas NaX e NaA. Foi avaliado o efeito do contato do extrato aquoso de Stevia com as zeólitas CaX, BaX, CaA and BaA. Os resultadosmostraram que o extrato que ficou em contato com a zeólita CaX foi o que obteve maior descoloração e não teve as características iniciais alteradas, em termos de concentração, glicosídeos e sabor. Com testes feitos em batelada à temperatura ambiente, o contato entre o extrato aquoso de Stevia e a zeólita CaX, proporcionou uma descoloração entre 70-80%. Os testes mostraram ser possível a regeneração dazeólita, sendo possível a utilização da zeólita por mais de uma vez no processo, sendo alcançada uma descoloração entre 65-70%.
Palavras-chave: clarificação, Stevia rebaudiana (Bert.) Bertoni, zeólita CaX, adsorção seletiva.

The high standards of our technological society have changed the concept of health, while the introduction of new chemical products modified human alimentary habits in theinterests of a more healthy life (Kinghorn et al., 1995). For simple aesthetic or health problems, man is substituting the well-known and popular sugar (sucrose) for products known as sweeteners. These have a flavor similar to that of sucrose, but with little or no caloric value (Angelucci, 1989). Among the sweeteners, there are glycosides extracted from the dry leaves of a native plant calledStevia rebaudiana (Bert.) Bertoni (Asteraceae), or simply Stevia. Its leaf has several sweetener glycosides such as stevioside, rebaudioside A, B, C, D, E and dulcosides A and B. Those present in larger quantity are stevioside (5-10%), rebaudioside A (2-4%), rebaudioside C (1-2%); others are present in smaller concentrations. Figure 1 shows glycoside
Acta Scientiarum

structures in which radicalsR1, R2 and R3 mark their difference. Glycosides are sweeteners of natural origin, stable to a wide range of pH and heat. Since they are non-caloric, non-nutritive, non-fermenting, prevent caries and dental plaques, sweeteners are industrially interesting. Due to these advantages there are many scientific articles and patents published on Stevia and its sweetening glycosides. They include analyticmethods, purification methods, sensorial evaluation and, chief among them, the toxicological aspects. In fact, everybody attests the safety of Stevia extract and its sweetening glycosides for human consumption. Stevioside is used as a nutritious sweetener in many countries of the world. In Japan it has been used since 1970 as a sweetening agent and dominates about 41% of the market. It was...