Abstract: Objectives: To investigate the relationship between color values and antioxidant activity of mung bean clear soup (MBCS) and the effects of water type, granule sugar, table salt and sodium bicarbonate on them. Methods: Phenolic contents (total phenols, total flavonoids and condensed tannins), pH value, color values (L*, a* and b*) and antioxidant properties (DPPH free radical scavenging ability and FRAP value) of MBCS during cooking were tested and the correlations among these parameters were analyzed. Results: The color values and antioxidant activities of MBCS increased with increasing amount of dissolved phenols. Deionized water resulted in increased phenolic contents and antioxidant activity of MBCS compared to tap water. The antioxidant activities of MBCS were decreased by addition of sodium bicarbonate or granule sugar but increased by addition of salt. There was a strong correlation between the b* and antioxidant activities of MBCS. Conclusion: Phenols mainly contribute to the color and antioxidant activities of MBCS and influences the pH. Slightly acidic water is favorable for the preparation of green MBCS with strong antioxidant activity.

Key words: mung bean clear soup, color change, polyphenols, antioxidant capacity