Screening and Characterization of 1,8-Cineole-Based Solvents as an Alternative to Hexane for Obtaining Nonpolar Compounds from Plant-Based Milk Coproducts

The design of new hydrophobic solvents is essential for replacing the toxic hexane for extracting nonpolar compounds such as fatty acids. On the other hand, the full use of plant matrices seeking to obtain new food and pharmaceutical products from their coproducts has also been the focus of sustainable processes. This study proposed new solvents for replacing hexane to extract fatty acids and hydrophobic bioactive compounds from coproducts obtained from almond- and peanut-based milk processing. The COSMO-RS method was used to select terpene-based mixtures to substitute hexane. Experimentally, four liquid solvents were formed from 1:2 tetradecanol/1,8-cineole (TE/EU), 1:2 camphor/1,8-cineole (CA/EU), 1:1 oleic acid/1,8-cineole (OL/EU), and 1:1 menthol/1,8-cineole (ME/EU). DSC analyses indicated the reduction of the CA/EU, OL/EU, and ME/EU melting points concerning their components. However, the melting point values predicted by the COSMO for obtaining eutectic mixtures differed. CA/EU was the only mixture with a melting point lower than the COSMO-RS-predicted one. In contrast, the FTIR spectra did not provide a clear visualization of the hydrogen bond formation between camphor and 1,8-cineole. This could be due to the formation of weak hydrogen bonds, a phenomenon observed in other studies. Nevertheless, these solvents have the advantage of low viscosity, a promising feature that likely facilitated mass transfer in the extraction of hydrophobic compounds from almond and peanut coproducts. ME/EU provided the same global extraction yield as hexane and higher phytosterol extraction from almond coproducts. On the other hand, CA/EU provided the same global yield and squalene content as hexane from peanut coproducts. The extracts can be directly used in food and pharmaceutical applications since the solvents are usually part of the formulations. However, DSC and TGA-DTA analyses indicated possible ways to separate the solvents.