Selective Recovery of Polyphenols from Discarded Blueberries (Vaccinium corymbosum L.) Using Hot Pressurized Liquid Extraction Combined with Isopropanol as an Environmentally Friendly Solvent

The use of water-ethanol mixtures in hot pressurized liquid extraction (HPLE) to recover phenolic compounds from agro-industrial waste has been successfully investigated. However, the unresolved challenge of reducing solvent costs associated with the process hinders the scaling of this eco-friendly technology. This study evaluated the use of isopropanol as an alternative, lower-cost solvent for recovering polyphenols from discarded blueberries through the HPLE process. HPLE was carried out using water-isopropanol mixtures (0, 15 and 30%) at 70, 100, and 130 degree celsius. The total polyphenol content (TPC), antioxidant capacity (DPPH and ORAC), glucose and fructose contents, and polyphenol profile of the extracts were determined. HPLE extracts obtained using high isopropanol concentrations (30%) and high temperatures (130 degree celsius) presented the highest TPC (13.57 mg GAE/gdw) and antioxidant capacity (IC50: 9.97 mg/mL, ORAC: 246.47 mu mol ET/gdw). Moreover, the use of 30% water-isopropanol resulted in higher yields of polyphenols and removal of reducing sugars compared to atmospheric extraction with water-acetone (60%). The polyphenolic profiles of the extracts showed that flavanols and phenolic acids were more soluble at high concentrations of isopropanol (30%). Contrarily, flavonols and stilbenes were better recovered with 15% isopropanol and pure water. Therefore, isopropanol could be a promising solvent for the selective recovery of different bioactive compounds from discarded blueberries and other agro-industrial residues.

Automated summary

This study evaluates the use of isopropanol as a low-cost solvent for recovering polyphenols from discarded blueberries. The results show that using high concentrations of isopropanol and high temperatures leads to the highest content of polyphenols and antioxidant capacity. Additionally, using 30% water-isopropanol mixture improves the yield and removal of reducing sugars.