Characterization of different annatto extracts based on antioxidant and colour properties

Annatto seeds are known as the only natural source of bixin, a carotenoid widely used in the food industry as colourant. Thus, the aim of this study was to obtain annatto extracts with different solvents and use statistical multivariate analysis to correlate the antioxidant and colourant properties of these extracts. According to the Principal Component Analysis, PC1 was associated to colour and PC2 to antioxidant capacity. Extracts with similar polarities were joined together by Cluster Analysis. The annatto extracts obtained with methanol/water and ethanol/water were characterized by their low bixin levels and a soft yellowish colour, whilst those obtained with methanol, ethanol and ethyl acetate showed red colour and higher bixin contents. The best solvent for bixin extraction was ethyl acetate (4.9 mg bixin/g seeds), whereas the highest total phenolic levels were verified in the most polar extracts, achieving maximum of 1.84 gallic acid equivalent/g seeds in the methanol/water extract. On the other hand, the hexane extract showed both low phenolic and bixin contents, as well as low free radical scavenging activity. Taking into consideration the antioxidant and colourant properties, solvents with medium polarity, especially methanol, should be used to obtain functional annatto extracts.