Enabling technologies for the extraction of grape-pomace anthocyanins using natural deep eutectic solvents in up-to-half-litre batches extraction of grape-pomace anthocyanins using NADES

Bioactive compounds should be extracted using alternative solvents and enabling technologies, in accordance with green extraction principles. The aim of this study is to develop an eco-friendly extraction method for grapepomace anthocyanins on a larger scale. From a preliminary screening of 8 different natural deep eutectic solvents (NADES), a combination of choline chloride:citric acid was selected because of its price, physicochemical properties, and anthocyanin recovery and stability. The effects of multimode-microwave (MW), and low-frequency-ultrasound (US) irradiation (used alone or simultaneously), as well as that of process parameters on extraction efficiency have been investigated in order to maximise anthocyanin extraction yield. The best conditions were found to be: simultaneous ultrasound/microwave-assisted extraction (UMAE) (MW power at 300 W, US power 50 W), for 10 min with 30% (v/v) of water. This gave 1.77 mg g(dw)(-1) of anthocyanins. Anthocyanins were efficiently recovered from NADES, which were recycled. The optimised procedure was scaled up to a half-litre batch.