Exploring deep eutectic solvent extraction's impact on anthocyanin degradation kinetics in various conditions

Abstract

This study evaluated the stability of anthocyanins in red cabbage extracts using deep eutectic solvents (DESs) and acidified methanol under thermal and storage conditions. DESs included combinations of choline chloride with malic acid (Ma), xylitol (Xy), lactic acid (La), and glycerol (Gl). Extracts were heat-treated at 40 °C–100 °C and stored at temperatures of 25 °C, 4 °C, and −18 °C for 35 days. Analysis involved pH differential methodology, browning and polymeric color indexes, antioxidant assays (DPPH• and ABTS•+), HPLC, and FT-IR spectroscopy. Results showed that anthocyanin content in all solvents decreased with increasing temperature. Acidified methanol samples experienced a notable reduction from 304.2 mg/L at 40 °C to 246.5 mg/L at 100 °C. Malic acid, lactic acid, xylitol, and glycerol samples also showed significant declines at higher temperatures. Cold storage effectively preserved anthocyanin levels. Kinetic analysis indicated that ChCl-Xy was the most effective solvent in preserving anthocyanins and minimizing browning, while ChCl-Ma led to the highest anthocyanin degradation and color changes. At 25 °C, Ac-MetOH demonstrated the highest antioxidant activity (DPPH• scavenging rate k of 5.66 ± 0.15), but ChCl-Ma exhibited the highest browning index (k of 3.4 ± 0.13) and polymeric color index (k of 5.54 ± 0.12), suggesting lower stability compared to other solvents.