Kinetics of thermal degradation of beet dyes (beta vulgares l) in aqueous medium
Resumo
The betacyanin dyes present in beets (Beta vulgaris L) were extracted with water from lyophilized and pulverized beets, with a ratio of 50 g/1000 mL/10 minutes, at room temperature. The extract was separated by centrifugation at 3000 rpm/20 minutes. From the stock solution, dye solutions corresponding to the proportion of 5×10-3 gbeetroot mL-1 were prepared for the thermal degradation tests, in the temperature range of 30°C to 80°C, in a thermostatized bath, being monitored by absorption analysis in the ultraviolet-visible region, wavelength, , 480 nm for betaxanthins and 537 nm for betakinanins, for 180 minutes. The degradation of the dye follows a kinetic of 1st order for homogeneous reactions, with 1 reagent and the constant reaction rate was 1.4×10-4 mg/h, the half-life time, t1/2, was 8.25 hours, at a temperature of 30°C for the betacyanin dye. The degradation process has an activation energy of 55.39 kJ/mol for betacyanin dye and 56.06 kJmol-1 for betaxanthin. After the time of the degradation test, the solution assumes a yellowish color associated with betalamic acid, the degradation product of betacyanin.
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