Development and characterization of natural deep eutectic solvents for optimized extraction of olive pomace phenolics

Olive oil production leaves behind a mountain of waste—about 80% of the olive's weight—but that 'waste' may hold the key to unlocking valuable bioactive compounds.

The golden oil we drizzle over salads comes at a hidden cost: for every olive pressed, a hefty by-product called pomace is left behind. This underutilized residue, however, is packed with phenolic compounds—natural antioxidants with promising health benefits. The challenge? Efficiently extracting them without harsh, toxic solvents.

Enter Natural Deep Eutectic Solvents (NADES). In this study, researchers synthesized 16 different NADES using 8 solvent types at two water concentrations. They then characterized these green solvents' physicochemical, spectroscopic, and thermal properties, and tested their ability to extract phenolics from olive pomace—while also tallying production costs.

The results were revealing. The NADES displayed a wide range of pH values (from 0.26 to 12.23) and shear viscosities (7.06 to 492.30 mPa·s), yet all fell within a low polarity range. Sugar-based NADES emerged as the most cost-effective option, but the real star was a choline chloride-urea blend, which showed the best extractive potential. This work turns a waste problem into a sustainable opportunity.

Key Points

• 16 NADES synthesized from 8 solvents at two water levels.
• Physicochemical, spectroscopic, and thermal properties characterized.
• Choline chloride-urea NADES showed best phenolic extraction.