Mass transfer process during extraction of phenolic compounds from milled berries

Optimization of the extraction of phenolic compounds from milled berries has been studied and the effective diffusivity and mass transfer coefficient have been measured during solid-liquid extraction in an agitated vessel. Optimization was carried out by a surface response methodology, using ethanol or sulfured water concentration, temperature, and solvent-to-solid ratio as independent variables. Maximum yields of total phenolics and anthocyanins were obtained at 19 1 of solvent per kg of milled frozen berries with 1000-1200 ppm SO2, or 60% ethanol concentration. The increase of the extraction temperature increased the rate of extraction and reduced the extraction time by increasing the diffusivity. The higher the SO2 concentration in the solvent mixture, the higher the diffusivity, however ethanol concentration increased diffusivity up to a maximum and decreased it with further increase of ethanol concentration. Diffusivities of 24.3 x 10(-11) and 12.3 x 10(-11) m(2) s(-1) and mass transfer coefficients of 3.85 x 10(-5) and 2.36 x 10-5 ms(-1) were obtained for extraction of anthocyanins at 40 degreesC using 700 ppm, SO2 and 67% ethanol, respectively. (C) 2003 Elsevier Science Ltd. All rights reserved.