Clarification of aqueous stevia extract using alginate beads-Evaluation by factorial design methodology

摘要

Stevia is used as a sweetener due to its low calorific value and its taste, which is very similar to that of sucrose. Stevia extract is dark in colour and needs to be clarified for better acceptance by consumers. The adsorption processes widely used in clarification do not use organic solvents. Alginate beads have been used as the adsorbent material in the present work. Experiments were carried out in batch mode in which the aqueous stevia extract was mixed with the alginate beads prepared previously by ionotropic gelation. A factorial design was used to study the process of clarification, in which colour removal and the percentage of stevioside adsorbed were evaluated. The studied factors were temperature, pH of the aqueous stevia extract and adsorption time. The results showed that alginate beads are capable of adsorbing both the steviosides and the pigments that give colour to the extract. The experimental design showed that only the pH and contact time were important variables in determining the percentage clarification, in contrast to the other responses which were not affected by the various factors studied. An equation describing the percentage clarification as a function of pH and time is proposed.