Efficiency of CaO usage as a pre-clarification adsorbent in aqueous stevia extract

Abstract

Stevia extract, when untreated, has a dark brown appearance, mainly because of the presence of impurities. CaO nanoparticles are effectively used as an adsorbent to purify the desired chemical compounds, decolorize the liquids, etc. in the food industry. In this study, the efficiency of CaO nanoparticle as a pre-clarification adsorbent was investigated for the removal of impurities in aqueous stevia extract before the purification process. For this purpose; dry stevia leaves were ground with distilled water (1:25, dry leaf:water, w/w) and kept in a water bath at 40 °C for 30 minutes. After the extraction process, the samples were centrifuged at 2900xg for 25 minutes at 25 °C. Then the extracts were treated with different concentrations of CaO. Steviol glycoside composition of the CaO-treated and untreated samples (control group) were analyzed by HPLC. According to the results, it was observed that the obtained stevia extracts were clearer (had lower turbidity values), especially when treated with CaO at the level of 0.15%, and no concentration loss occurred in terms of the glycosides analyzed in the extracts. Besides, the peak areas of both glycosides increased proportionally when CaO adsorbent was added to the main process. For further studies, investigation of other CaO-related parameters such as contact time, ambient conditions (pH, temperature, etc.) is recommended to be tried to increase the efficiency of this adsorbent in stevia processing.