Exploring bioactive compounds in lyophilized grape pomace extracts: comparative analysis of traditional and innovative extraction methods

This research investigates the efficacy of different solvent-based extraction methods in deriving polyphenols from grape pomace. The study evaluates three distinct extraction techniques: Conventional Extraction (CE), Microwave-Assisted Extraction (MAE), and Ultrasound-Assisted Extraction (UAE), using solvents such as ethanol, methanol, and acetone. The study focuses on evaluating the extraction yield, total phenolic content, total flavonoid content and the antioxidant capacity of the extracts. The results demonstrate that MAE, using ethanol as the solvent, achieved the highest extraction efficiency of 34.53%, followed by UAE and CE at 31.37 and 16.86% respectively. In terms of antioxidant capabilities, ethanol extracts obtained via UAE exhibited superior DPPH Radical Scavenging activity (79.84%) in comparison to MAE ethanol extracts (77.18%), and CE ethanol extract (46.74%). The ethanol extract from UAE contained the most significant concentrations of phenolics (290.47 mg GAE/g) and flavonoids (36.95 mg RE/g), along with the highest ABTS scavenging activity (81.24%) as revealed by High-Performance Liquid Chromatography (HPLC). Additionally, the physical examination of the extracts through scanning electron microscopy showed the agglomerated micro-particles with a diameter of 50–100 μm and an average particle size of 753 nm. These findings underscore the potential of grape pomace as an efficient source of antioxidants, particularly when employing UAE with ethanol, for applications in the food industry.