Green Method Comparison and Optimization of Anthocyanin Recovery from “Sangiovese” Grape Pomace: A Critical Evaluation of the Design of Experiments Approach

Wine production leaves behind a treasure trove of bioactive compounds—if we know how to unlock them. This study pits green extraction methods against conventional ones to recover anthocyanins from grape pomace, revealing surprising trade-offs between yield and antioxidant activity.

Grape pomace, the main by-product of winemaking, is far from waste—it's packed with bioactive compounds. In this work, scientists tested several green methods to recover anthocyanins from Sangiovese grape pomace, using ultrasound-assisted extraction (UAE) and microwave-assisted extraction (MAE) paired with eco-friendly solvents like acidified water, an ethanol/water mix, and Natural Deep Eutectic Solvents (NaDES). These were compared to a conventional methanol-based method.

The results were striking: UAE yielded total anthocyanin indices from 36.9 to 75.2 mg/g dry weight, while MAE outperformed it with values between 54.4 and 99.6 mg/g. The conventional method landed at 47.1 mg/g. MAE emerged as the winner, so the team applied a Design of Experiments (DoE) approach to fine-tune it, varying temperature, time, and solid-to-liquid ratio.

Using malvidin-3-O-glucoside content and antioxidant activity as response variables, they found a fascinating split: higher temperature and time boosted antioxidant activity but lowered the concentration of the main anthocyanin. This means the optimal extraction conditions depend entirely on what you're targeting—a critical insight for anyone using response surface methodology.

Key Points

• MAE outperformed UAE and conventional extraction for anthocyanin recovery.
• Optimal conditions vary: temperature/time boost antioxidants but reduce malvidin-3-O-glucoside.
• DoE reveals critical need for selecting accurate response variables.