The Impact of Temperature and Ethanol Concentration on the Global Recovery of Specific Polyphenols in an Integrated HPLE/RP Process on Carménère Pomace Extracts.

Sequential extraction and purification stages are required to obtain extracts rich in specific polyphenols. However, both separation processes are often optimized independently and the effect of the integrated process on the global recovery of polyphenols has not been fully elucidated yet. We assessed the impact of hot-pressurized liquid extraction (HPLE) conditions (temperature: 90-150 °C; ethanol concentration: 15%-50%) on the global recovery of specific phenolic acids, flavanols, flavonols and stilbenes from grape pomace in an integrated HPLE/resin purification (RP) process. HPLE of phenolic acids, flavanols and stilbenes were favored when temperature and ethanol concentration increased, except for chlorogenic acid which showed an increment of its Gibbs free energy of solvation at higher ethanol contents. Ethanol concentration significantly impacted the global yield of the integrated HPLE/RP process. The lower the ethanol content of the HPLE extracts, the higher the recovery of phenolic acids, flavanols and stilbenes after RP, except for flavonols which present more polar functional groups. The best specific recovery conditions were 150 °C and ethanol concentrations of 15%, 32.5% and 50% for phenolic acids, flavanols and stilbenes, and flavonols, respectively. At 150 °C and 32.5% of ethanol, the extracts presented the highest total polyphenol content and antioxidant capacity. The integrated HPLE/RP process allows a selective separation of specific polyphenols and eliminates the interfering compounds, ensuring the safety of the extracts at all evaluated conditions.