where D is the diffusivity, Ea is the energy of activation
for diffusion, R is the universal gas constant, and T is the
absolute temperature. Natural logarithms of anthocyanin
and total phenolic diffusivities obtained at 6, 17, and
30 C were plotted against the inverse of absolute temperature
(1=T ) and the energies of activation for phenolic
diffusion were calculated from the slope (Ea=R) of the
straight lines. Diffusivities obtained at 40 and 74 C were
not considered for calculation of the energy of activation.
At 74 C, evaporation of a large volume of ethanol
and reduction of SO2 concentration by effect of high
temperature might have impaired the beneficial effect of
the solvent on the diffusivity during extraction. Furthermore,
anthocyanins degradation with temperatures
higher than 40 C (Cacace & Mazza, 2003) and membrane
denaturation over 55 C (Schwartzberg & Chao,
1982) could have modified anthocyanin diffusivity and
yield at 74 C