ASSAY ON EXTRACTION AND COMPLEXATION OF ANTHOCYANINS FROM MOLASSES GRASS (Melinis minutiflora P. Beauv ) AND STUDY OF ITS STABILITY

Anthocyanins are water-soluble pigments with a high potential for use as natural dyes. The modifications on anthocyanins structures, such as copigmentantion, can increase the stability. Molasses grass (Melinis minutiflora) is a perennial species with a high concentration of anthocyanins in their fluorescence, among them cyanidin-3-glycoside and acyl-derivatives. The jabuticaba (Plinia sp) is a typical Brazilian fruit species with hydrolyzable tannins in seeds, specially castalagin and vescalagin. This work aimed to extract anthocyanins from molasses grass, promoting its complexation and stability evaluation. Four extracts were prepared from molasses grass anthocyanins using a hydroalcoholic solution (30%) as an extractor at pH 2.7, being i. molasses grass (MG); ii. molasses grass with dried jabuticaba seeds (MGJS); iii. molasses grass and calcium sulfate (MGCa); iv. molasses and magnesium sulfate (MGMg). The extracts obtained were characterized by color intensity, hue, anthocyanin concentration, color composition and study of stability at 30, 60 and 90°C for 30 to 300 minutes. The anthocyanin contents in the extracts ranged from 52.76±3,66 mg/L (MG) to 71.30±5,67 mg/L (MGCA). Differences in concentrations may be associated with the hyperchromic effect of the co-pigmented extracts. Lower values of color intensity (1,69±0,08) and hue (0,545±0,01) were found in the MG, which also presented higher values for the red brightness parameter (39,35±2,03). This fact suggests the lack of association with the anthocyanins of this extract. As for the stability study, at room temperature and dark, the extracts were maintained at 300 minutes from 86.06 (MGS) to 92.43% (MG) of the initial concentration of anthocyanins. However, at 60°C, the final concentration ranged from 31.50 (MGCa) to 47.66% (MGMg). The MGJS and MGMg assays were the ones that contributed to the maintenance of anthocyanins under these conditions, which could increase the stability of natural dyes.