Improvement of color stability using a chelating agent in model soft beverages subjected to Fenton reaction

The colorants found in beverages are sensitive to degradation resulting in a loss of color, which can affect the perception of the product quality by the consumer. The Fenton reaction is one of the possible degradation pathways. The Fenton oxidation process is a catalytic reaction of hydrogen peroxide (H2O2) with ferrous ions (Fe2+) that generates hydroxyl radicals able to degrade the organic molecules present in the solution. In this work, the effect of the Fenton reaction in colored model soft beverages was studied using UV-visible spectrometry. The naphtol blue black was selected as a benchmark dye because it can be easily followed to probe the Fenton process. The percent degradation of this synthetic dye in an aqueous solution at pH = 3.4, simulating conditions in beverages, was monitored in the presence of FeSO4 and H2O2. Other pHs (pH = 2.7, 6.1, and 10) were also tested to obtain a full picture of the phenomenon. In an attempt to prevent the dye degradation by the Fenton reaction occurring in beverages, the effect of the addition of EDTA, a chelating metal agent able to form complexes with iron ions, was evaluated, as a model. The effect of the EDTA concentration and the influence of the pH were also explored.