Abstract:

This study aimed to develop a continuous operation mode for extracting steviol glycosides from stevia leaves instead of current batch mode by means of three-stage continuous countercurrent extraction technology. Different drying methods of stevia leaves were compared, like insolation, drying in the shade, drying in the oven and microwave drying. The results showed that microwave drying (a rapid drying method) is the best way, which only takes three minutes to dry stevia leaves from the moisture 76.07% to 3.53%, meanwhile, the contents of rebaudioside A and stevioside in the dried leaves are respectively increased by 27% and 22%, respectively. The followed work was comparison of extraction efficiency between the three-stage continuous countercurrent extraction mode and three-stage tandem countercurrent extraction and batch extraction modes. The results demonstrated that the extraction yields of the three methods are closely tied (99.9%, 99.82% and 99.9%), but the whole procedure only takes 20 minutes for the continuous countercurrent extraction, while the other two batch extraction modes take at least 60 minutes respectively. Therefore, the continuous countercurrent extraction is a better and more suitable extraction method for industrial production.

Key words: stevia, steviol glycosides, countercurrent extraction, drying