Anthocyanidins and anthocyanins are flavonoids with nutritional, antioxidative and color properties that are present in various food products and biomass, such as food waste. The large chemical diversity amongst these molecules potentially leads to different affinities or activities in food and non-food applications. In order to characterize the extraction profile, advanced analytical techniques along with optimized separation procedures are required. Alternatively, theoretical tools can be applied for predicting the solubility or binding affinity of molecules in various reaction media. In this paper, the solubility of anthocyanidins and anthocyanins was analyzed by various theoretical tools such as group contribution methods (e.g., Hansen solubility parameters and Flory-Huggins interaction parameter (χ12)) and molecular modeling (e.g., static calculations based on Density Functional Theory (DFT) and COSMO-RS). It was found that COSMO-RS was able to give quantitative information on the solubility behavior within various pure solvents and it is able to describe the main intermolecular interactions between colorant and solvent, while Hansen solubility parameters were most appropriate to find the most optimal organic solvent-water mixture ratio. In general, solvents with electron-rich aromatic rings and/or containing electron donors, acting as hydrogen bond acceptors, showed the highest solubilizing power for anthocyanidins and anthocyanins.
Abstract