Extraction of polyphenols from white distilled grape pomace: optimization and modelling

Area of Science:

• Food Science and Technology
• Chemical Engineering
• Biotechnology

Background:

• Grape pomace, a byproduct of winemaking, is rich in polyphenols with potential health benefits.
• Efficient extraction of these valuable compounds is crucial for valorization.
• Previous studies indicated different solvent efficiencies for polyphenol extraction.

Purpose of the Study:

• To investigate and optimize the continuous extraction of polyphenols from Vitis vinifera var. "Albariño" grape pomace.
• To compare the efficacy of aqueous and ethanolic extraction methods.
• To model the polyphenol extraction process using Fick's second law.

Main Methods:

• Laboratory-scale vertical extractor used for continuous extraction.
• Experimental design to analyze effects of flow rate (2-4 ml/min) and temperature (40-50°C).
• Polyphenol extraction modeled using Fick's second law with spherical particle assumption (0.5 mm diameter).

Main Results:

• Aqueous extraction yielded up to 30-fold higher polyphenolic content compared to ethanolic extraction.
• Effective diffusion coefficients for aqueous extraction ranged from 0.6x10⁻¹¹ to 2.1x10⁻¹¹ m²/s.
• Effective diffusion coefficients for ethanolic extraction were lower, ranging from 0.1x10⁻¹¹ to 0.76x10⁻¹¹ m²/s.
• External mass transfer resistance was found to be negligible.

Conclusions:

• Aqueous extraction is highly effective for recovering polyphenols from "Albariño" grape pomace under the tested conditions.
• Continuous extraction offers a viable method for polyphenol recovery from grape byproducts.
• The diffusion model accurately describes the extraction process, providing key parameters for optimization.