Total Phenolic Content Yield and Stability Of Vanilla Planifolia In Natural Deep Eutectic Solvent Using Ultrasonic Assisted Extraction

Abstract

Vanilla (Vanilla planifolia) is prized for its unique flavor, typically consumed as vanilla extract, which requires substantial extraction time using volatile ethanol. Natural deep eutectic solvents (NADES), abundant and non-volatile, have shown solvating ability for bioactive compounds. This study examines the yield of phenolics from vanilla beans based on total phenolic content (TPC), using NADES in thermal and ultrasonic-assisted extraction (UAE). The solvents used were 40% ethanol, an equimolar combination of lactic acid-propylene glycol (LA-PG) NADES, and choline chloride-glycerol (ChoCl-Gly) NADES. Solvents were measured for pH, followed by extraction under thermal and UAE methods, and TPC assay quantified phenolics concentration. Ethanol had the highest pH (10.57 ±1.37), followed by ChoCl-Gly (6.91 ±1.37), and LA-PG (1.45 ±1.62). Thermal extraction yielded the highest phenolics with LA-PG (427.330 ±2.03 μg GAE/ml), followed by ChoCl-Gly (279.943 ±10.39 μg GAE/ml), and ethanol (258.771 ±8.64 μg GAE/ml). In contrast, UAE gave ethanol the highest yield (894.205 ±6.91 μg GAE/ml), followed by LA-PG (695.488 ±12.7 μg GAE/ml), and ChoCl-Gly (448.567 ±18.94 μg GAE/ml). Significant differences were observed (p=0.001) between the TPC of NADES and ethanol, alongside between the TPC of vanilla beans extracted with UAE and thermal extraction (p<0.001). Findings confirm NADES procures higher yields than ethanol, especially LA-PG due to phenolics' affinity in acidic environments. UAE is more effective than thermal extraction, enhancing phenolics mass transfer by disrupting cell matrices. However, the high viscosity of NADES impedes ultrasonication compared to non-viscous ethanol.