Curcumin was extracted from Curcuma Longa employing a green, bio-based, and food-agreed surfactant-free microemulsion (SFME) consisting of water, ethanol, and triacetin. Concerning the high solubility of curcumin in the examined ternary mixtures, it was attempted to produce highly concentrated tinctures of up to a total of ~130 mg/mL curcuminoids in the solvent by repeatedly extracting fresh rhizomes in the same extraction mixture. The amount of water had a significant influence on the number of cycles that could be performed as well as on the extraction of the different curcuminoids. In addition, the purity of single extracts was enhanced to 94% by investigating several purification steps, e.g. vacuum distillation and lyophilization. Through purification before extraction, the water insoluble curcumin extract could be solubilized indefinitely in an aqueous environment. Additional stability tests showed that solutions of curcumin can be stable up to five months when concealed from natural light.

The food additive polyvinylpolypyrrolidone is approved for use as a filter aid. The water-soluble substances test of polyvinylpolypyrrolidone often shows poor reproducibility. The instruction 'boil gently while stirring using a stirrer' was considered critical, and so this issue was examined. The results showed that the use of a combination of both an oil bath and a stirrer provided good reproducibility without decomposition or other problems.