Study on the Clarification Process of Stevia Extract by Small-Aperture Ceramic Film

In this paper, the effect of small pore size ceramic membrane clarifying stevia extract was studied. By comparing the filtration flux, decolorization rate and yield of stevia extract with different pore size, the better pore size of ceramic membrane was determined, and the operating parameters of ceramic membrane were optimized. The results showed that the ceramic membrane of 5 nm was better. At 40 ℃, the operating pressure was 5 bar, the flow rate of the membrane surface was 4 m/s, concentrated 10 times, and the filtration effect of 30% raw liquid water was the best. The average filtration flux of ceramic membrane was 102.6 kg/(m²·h) and the yield of stevia was 99.2%. After filtration, the ceramic membrane was cleaned for 1 h by 1%~2% NaOH, and then 0.5%~1% nitric acid was used for 1 h. The recovery rate of ceramic membrane water flux could reach more than 99%, and the regeneration effect was good and could be reused. Compared with the flocculation process, the decolorization rate of ceramic membrane increased by 2.6% and the yield of stevia increased by 6.8%. Therefore, the membrane process can replace the traditional flocculation process to clarify the extract of stevia.