RESTORATION OF THE RED COLOR OF PHOTO-BLEACHED CARTHAMINE IN CALCIUM ALGINATE GEL MEMBRANES

The restoration of the red colour of carthamine (photo-bleached in polymeric heterosaccharide gels) was investigated using sodium salts, potassium salts, and alkali. Ca-alginate gel was stained with carthamine, and the red-dish membranes were exposed to fluorescent light for 2.5, 4.0 and 20 h (at 28 degrees C). The resulting orange-yellow gel membranes were treated with Na- or K-citrate solution and the restoration of the red colouration was followed spectrophotometrically. The results indicate that the red colour of carthamine can be retained within the gel membranes, while yellow-coloured compounds were removed and/or transformed by the alkaline salt solutions.