| Summary: | It was studied parameters that influence the solid-liquid extraction of natural dye from annatto and the ultraviolet protection (UV) conferred by its application in a natural fiber. Annato is one of the natural dyes most used worldwide and its main pigment is the carotenoid bixin, which is converted by alkaline hydrolysis into norbixin. Different organic solvents and alkaline solutions were studied for extraction: acetone, ethyl acetate, KOH in solution and ethanol. It was analyzed the effect of the parameters: temperature, solid particle size, extraction time and solid/solvent mass ratio. The results obtained revealed that an ideal extraction was verified using ethanol:acetone 50% (v/v), 55ºC and particle size of 100 MESH. It was observed that the solvent saturated in 20 minutes of extraction, meaning that the solid can be used for more than one extraction cycle. The dye conferred an ultraviolet protection in bleached cotton of about 89% of the absorbed ultraviolet radiation
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