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 (rho > 0.994), which gave the possibility for estimation of initial rate and extent of solid-liquid extraction. (c) 2006 Elsevier Ltd. All rights reserved.