The extraction and purification of anthocyanin pigments from calyx of Hibiscus sabdariffa, and its use as potential rapid indicator paper for detecting the borax in food were investigated. By using the colour comparison and the differential pH methods, the optimal conditions for pigment extraction were identified as follows: ethanol solvent to water is 50:50 with supplement 1 percent HCl
the ratio of solvent per raw-material is 14 ml/1g
extracting duration is 6 days. By fractional extraction method, the crude anthocyanin pigments are isolated from extracts of Hibiscus calyx. The concentration of pigments in the dry and fresh material was 15.2 percent and 1.06 percent, respectively. The acidity of the dry ingredients is 3.37 mld++ /1 g of raw material, the acidity of the dry pigment is 3.83 mld++/1 g of colour substance, respectively 0.58 mld++/1g dry material and the acid reduced 83 percent. By surveying several conditions for production of the indicator paper, the appropriate parameters are selected with color dilution of 1gram of dry colour substance to 400ml distilled water ratio
duration of color impregnated on paper is 120 seconds
the duration of indicator paper exposure to food (or food fluid) is 90 seconds. A minimum level of the indicator paper for detecting the borax is identified as 40 mg/1 kg of food. This result has shown that the minimum detectable limit is equivalent to turmeric paper. As for sensitivity, when testing on a number of food materials, the similar results were also been obtained.