Investigating Alternative Solvents Regarding Extractability of Lipophilic Food Ingredients in Spinach-Tomato Powder and Algae Materials

Extraction of natural products such as carotenoids, vitamin E and chlorophylls is still accompanied with certain challenges. Limitations exist in widespread availability of sophisticated techniques (e.g. supercritical fluid), which are often replaced by conventional approaches such as tissue homogeniser with disperser blades, a sonication bath or vortex mixing. Moreover, an appropriate selection of solvents is a critical step for selective extraction of compounds in complex, severely extractable matrices. The present investigation focussed on a comparison of conventional solvents (e.g. tetrahydrofuran, acetone, hexane) with more sustainable alternatives (e.g. 2-methyl-tetrahydrofuran (2-MeTHF); dimethyl carbonate (DMC); cyclopentyl methyl ether (CPME)) with and without addition of methanol regarding a broad range of analyte polarities. Herein, tetrahydrofuran with methanol resulted in maximum extraction efficiencies for total carotenoids in a spinach tomato powder. 2-MeTHF, DMC and CPME partially combined with MeOH proved to be equivalent alternatives for extraction of xanthophylls and β-carotene isomers. A comparison of renowned and widely available extraction techniques in context of challenging sample matrices (dried, pelletised and fresh microalgae) resulted in preferably powerful approaches such as Ultra-Turrax® homogenisation and sonifier probe application. Necessary pretreatments with methanol combined with powerful extraction techniques were apparently recommendable for dried algae products compared to fresh algae paste, thus reducing the potential extraction repetitions. Finally, a comparison of different syringe filter materials suggested the use of mixed cellulose ester (MCE) membranes for avoiding a significant loss (p < 0.05) of analytes (lutein, β-carotene, lycopene, vitamin E) compared to seven other membrane materials. Overall, these results represent a contribution to routine analysis of lipophilic food ingredients with a high transferability and adaptability across applied research.