Optimization of Fenton Oxidation Process for the Degradation of Color Precursors in Raw Sugar Beet Juice

The degradation of tyrosine and ferulic acid, via the Fenton process, was investigated in sucrose solution and raw sugar beet juice. Central composite design and response surface methodology were used to evaluate the relationships between degradation of the color precursors and the process parameters (i.e., initial concentration of the color precursors, solution pH, dosages of Fenton's reagent, and reaction time). According to the statistical analysis, the optimized conditions for each variable in aqueous sucrose solutions including an initial concentration of the color precursors equal to 45.0 mg L-1 were as follows: reaction time: 30 min, pH 5.8, Fe2+ dosage: 1.34 mM, and H2O2 dosage: 53.6 mM. Under these conditions, 61.8 % of the color precursors and less than 2.5 % of sucrose were degraded after 30 min of reaction. The highest decolorization efficiency of the raw juice was obtained about 55 % with the addition of 1.34 mM Fe2+ and 53.6 mM H2O2 at an initial pH of 6.2. Using the same conditions, approximately 50 % of tyrosine was degraded in treated juice with Fenton's reagent. Gel permeation chromatography analysis confirmed that the concentration of low molecular weight impurities in decolorized juice was considerably reduced. According to the results, Fenton oxidation process can be considered as a promising method for degradation of the color precursors and preparation of raw sugar beet juice with low color content.