Abstract: The effectiveness of the four solvents distilled water, ethanol, acetone and petroleum ether in extracting pigment from purple cabbage was compared, and ethanol was found to be the best solvent for purple cabbage pigment according to the color of the resulting extracts and residues. Further, 25% ethanol was the best solvent for the extraction of the pigment by comparison of absorbance of extracts from it and higher or lower concentrations of ethanol. In the following investigations, the extraction of purple cabbage pigment was conducted by the traditional water bath extraction alone or in combination with either ultrasonic or microwave using 25% ethanol as the extraction solvent, and the extraction conditions were investigated. The optimum conditions for the single water bath extraction were 4 h extraction time, 55 ℃ water bath temperature and pH 2. With the assistance of ultrasonic, the optimum extraction duration was 45 min and the optimum pH and temperature were kept unchanged. In the microwave-assisted extraction, the optimum power was 300 W, the optimum length of extraction time was 3 min, and the optimum water bath temperature and pH were still 55 ℃ and 2, respectively. Obviously, the traditional water bath extraction in combination with either ultrasonic or microwave was superior to it alone in terms of required extraction time.

Key words: purple cabbage, naturally occurring pigment, extraction method