Patent ID: 7923552

Claim:
A method of purifying rebaudioside A from Stevia starting material comprising: (i) formulating a selected EtOH solvent consisting of water and ethanol, (ii) performing a first reflux stage by refluxing the Stevia starting material in the selected EtOH solvent and optionally performing additional reflux stages using retentate isolated from a refluxed mixture or from a stirred wash mixture, (iii) optionally, performing one or more stirred wash stages, and (iv) performing an ethanol purge and drying stage, wherein formulating a selected EtOH solvent comprises either (A) a reflux solvent approximation, wherein, based on the asserted or labeled purity of a batch of Stevia starting material, for a Stevia starting material labeled or asserted to be 90% rebaudioside A purity, the reflux solvent is formulated as ethanol and water, and for every 5% decrease in rebaudioside A purity below 90% rebaudioside A purity in the Stevia starting material, based on the asserted or labeled purity of a batch of Stevia starting material, increasing the water content of reflux solvent 1% above a baseline of 6% water, and the remaining volume of the reflux solvent is ethanol, or (B) preparing a series of test mixtures in which the water content is uniformly incremented from 0.5% to 15%, or within a subset of that 0.5% to 15% range, and the balance of solvent in each such test mixture is ethanol, assaying the retentate of a reflux of the Stevia starting material in each test mixture for rebaudioside A purity, and selecting as the selected EtOH solvent the test mixture that produces a retentate with the highest purity rebaudioside A.