Extração e caracterização óptica de corantes naturais fluorescentes como indicadores de ph em leite

Abstract

There is a growing interest in natural dyes due to their characteristics of non-toxicity, biodegradability, and renewable sources, which meet the trend of using environmentally safe materials. Furthermore, their antioxidant, antibacterial and chemical alterations due to the change in their hydrogen potential (pH) have attracted studies for the application of these substances in different areas of industry. Among these materials, in the flavonoids class, is the anthocyanin, present in leaves and flowers of several plants, which has a red / purple color. This is a well-studied dye due to its color change with pH and its application in films to monitor the quality of several products. On the other hand, in the class of carotenoids, annatto, a dye extracted from the annatto (Bixa Orellana), has a yellow / orange color. Its most common applications are in the food area as a dye for dairy products, such as cheese and butter. In this work, extractions of anthocyanin and annatto dyes were carried out as a function of pH, and the aqueous solutions of the pigments were characterized by absorbance, fluorescence, and the fluorescence lifetime techniques. Annatto dye was extracted from the seeds and anthocyanin from the leaves of the Tradescantia pallida purpurea plant in aqueous solutions with different pH values ~5-11, and 4-8, respectively. Then, after studying the optical behavior of natural dyes extracted in aqueous solutions with different pH values, they were evaluated inserted in adulterated milk, with more acidic as well as more alkaline pH content than natural milk, in the pH range of 4-11. In addition, from these liquid samples (natural dye inserted in milk) the possibilities of using anthocyanin and annatto as colorimetric and/or fluorometric pH indicators in milk were evaluated.