Extração e estabilidade de antocianinas do repolho roxo (Brassica oleracea)

Abstract

Anthocyanins make up the largest group of water-soluble pigments in the plant kingdom and it has been studied for being coloring agents natural food. Among the vegetables rich in anthocyanins, cabbage purple (Brassica oleracea) has a high concentration this pigment, and present low cost, making it a suitable raw material for extraction of a natural dye. However, anthocyanins degrade during the extraction vegetable and storage process. So the objective was evaluating the extraction of anthocyanins from cabbage purple, in different conditions of pH, temperature and solvent, besides assessing its stability over time under different conditions of storage. For obtaining dye were used different solvents (alcohol 25%, 96% alcohol and acetone), pH adjusted (4.0; 6.0) and temperatures (25 and 75ºC) and an additional treatment (water, pH 5,0 to 50ºC), the anthocyanins obtained were compared to a red synthetic dye, evaluating the instrumental color. Best extraction efficiency was obtained in 25% alcohol and water, with pH 4.0 to 6.0 exhibited greater red coloration. To evaluate the stability of the pigment during storage, the solvents water and alcohol 25% were selected and performed colorimetric readings chroma parameter (C*) against the standard (sample at time zero) every seven days for four weeks, stored under different conditions such as exposure to light, dark, and the presence or absence of oxygen. The extracts obtained in 25% alcohol under the conditions of pH 6.0 / oxygen / dark obtained better performance, and higher color saturation, remaining stable at 21 days. So the red cabbage was presented as a natural source of red dye in an acid medium.