Extraction of brown dye from Eucalyptus bark and its applications in food storage

摘要

The importance of plant pigments as natural food colourants has been increasing globally in order to avoid from environmental problems and health hazards associated with synthetic colours. The current consumer prefers the naturally derived food colourants due to their health promoting properties. The present investigations were carried out to establish the safety and nutritional value of natural dye produced from the bark of Eucalyptus globules. A brown fine powder was obtained by aqueous extraction of finally ground Eucalyptus bark. This brown dye contained tannins, reducing sugar, alkaloids, glycosides, saponins, various antioxidants, antimicrobial agents and antiradical compounds. Total phenolic contents were ranging from 66.83 to 534.80 μg of gallic acid equivalents per 100 grams dry weight of the dye. In 2,2-diphenyl-1-picrylhydrazyl assay, IC_(50) value was observed to be 77.20 μg/ml with respect to butylated hydroxytoluene (9.96 μg/ml) as a standard control. The earlier investigations on the coloured candies of various brands suggest that the synthetic dyes used in the production of candies are a very big jeopardy for human health. In the current studies, the natural brown dye obtained from the Eucalyptus bark was applied for the production of candies and then the stability of dye in the candies was measured in terms of caffeic acid content. The Eucalyptus bark dye has shown an excellent nutritional value with no toxicity against the tested mice looking its possible safe use as a food colorant in future. None of the aflatoxins were detected in the dye.