Study of solid–liquid extraction kinetics of total polyphenols from grape seeds

Grape seeds are a waste by-product obtained after wine or juice making and present a good source of functional compounds, such as polyphenols. Extraction is a very important step for later use of phenolic components. The effect of different temperatures and solid–liquid ratios on the solid–liquid extraction yield of total polyphenols and the effect of four classes of particle size on the extraction kinetics of total polyphenols with 50% of aqueous ethanol were studied. Temperature, solid–liquid ratio and milling degree had positive influence on extraction rate and extent of extraction. The 1.47–6.68% of total polyphenols per dry matter of grape seeds was extracted during 200 min. Extraction kinetics was estimated using non-experimental two-parameter equation – modified Peleg’s model. Results showed a good prediction of Peleg’s model for extraction kinetics in all experiments (ρ > 0.994), which gave the possibility for estimation of initial rate and extent of solid–liquid extraction.