Extração de corante natural do resíduo da uva isabel (vitis vinifera) via solvente hidroalcoólico

Abstract

Lately, the production of synthetic dyes increased significantly, mainly due to the great growth of the food industries. Its function is to make food more attractive. However, the major problem is the possible harmful effects on human health and to the environment. As a result, the demand for healthy food is increasing in the face of a demanding public. In this scenario, the natural dyes gain great prominence. These are obtained from plant or animal materials. This article proposed to extract natural dye from the residue of the Isabel grape (Vitis Vinífera), which is produced in large quantities by wine, fruit pulp and other derivatives industries. For the development of these work, the residue was dried at 60ºC in an air circulating oven and the kinetic curves were determined for the loss of moisture. Dye extraction was obtained by solid-liquid extraction, varying the solvent concentration: 5 and 10% ethanol / water m / v solution. In addition, the extraction in presence / absence of light was tested. The extraction was carried out in a shaker at room temperature with extraction time of 1 hour, mass of 10.5 g for the residue, volume of the solvent of 150 ml and stirring at 130 rpm. 1% w / v acetic acid was added in all solvents to maintain the pH in acid medium. The absorbance reading (UV / Visible spectrophotometer) at the 408 nm and 560 nm wavelengths for flavonoids and anthocyanins, respectively, was used to evaluate the extraction effectiveness. In addition, the quantification of anthocyanins was performed by means of differential pH. The powder dye was obtained by drying in the spray dryer and the color test in a colorless gelatin. The results of the kinetic curves showed that the optimal drying time for the residue was 5 hours, with dry basis moisture of 0.0285 g H 2 O / g solid. The absorbance reading indicated that the pure ethanol solvent (99.5%) obtained the highest absorbance value at the wavelength of 408 nm, of 4,695 Abs ± 0.194 and the hydroalcoholic 5% at 560 nm, 2,602 Abs ± 0.176 . It was also noticed that the light influenced the extraction of the natural dye, being necessary to conserve the extraction under the absence of light. The 5% hydroalcoholic solvent was effective at absorbance and color values. The quantification of anthocyanins was 83.179 mg / 100g ± 1.597. The dye powder obtained a coloration within the expected and with light violet tones. In the gelatin staining test, the liquid extracts presented satisfactory color, however, for the powdered dye, the result was not effective.