Color analysis and tracking of the reduction of an indigo solution in real-time using LabVIEW and machine vision

A novel detection method, known as RGB-tracking, was utilized to quantify the relative color changes in reactants/products during the dyeing of a solution of indigo as a model compound. The RGB-tracking system consists of a digital camera, a light source, a data acquisition device, a LabVIEW program, and its built-in function (Machine Vision). For the reduction of indigo, two types of reagents were employed: sodium dithionite (Na₂S₂O₄) for the chemical redox process and yeast (Saccharomyces cerevisiae) for the biological fermentation process. As a result, in the case of chemical redox during the reduction of the indigo solution, the progress of the reaction can be described by a color change, that is, the curves of R- and G-pixels, respectively. When the curve for the G-pixels began to increase, this indicated that leuco-indigo is being formed. A dramatic increase in the R-curve indicates that the amount of leuco-indigo has exceeded than that of indigo itself and that the reaction will gradually reach equilibrium. In contrast to this, additional complex behavior was observed in the case of biological fermentation. When the RGB-tracking curves for the R- and G-pixels reach their maximum values, this indicates that the concentration of leuco-indigo was significantly higher than that of indigo itself. The flattening of the RGB-tracking curves indicates that the reaction has reached equilibrium.