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 l 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 1011 and 12:3 1011 m2 s1 and mass transfer coefficients of 3:85 105 and 2:36 105
ms1 were obtained for extraction of anthocyanins at 40 C using 700 ppm SO2 and 67% ethanol, respectively.
2003 Elsevier Science Ltd. All rights reserved.
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