The study was conducted to investigate the quality characteristics, bioactive compounds composition, and antioxidant activities of yogurt prepared with 0, 1, 3, and 5% bitter melon juice instead of milk. In proportion to the fermentation time of the yogurt and the content of the bitter melon juice, the pH decreased, but acidity increased in both the control and treatment groups. Viscosity increased as the fermentation time increased, irrespective of the amount of bitter melon juice added. Lactic acid bacteria also increased rapidly as the fermentation time increased, and it was confirmed that the level of lactic acid bacteria in the experimental group to which 1∼5% of bitter melon juice was added was higher than that of the control group. The total polyphenol, total flavonoid, and total chlorophyll content of the yogurt increased in proportion to the amount of bitter melon juice added, and the antioxidant activity also tended to increase in proportion to a rise in the content of bitter melon juice. Based on the above results, it is believed that adding bitter melon juice to yogurt increases polyphenol, flavonoid, and chlorophyll content, thereby increasing antioxidant activity. Hence, the addition of bitter melon juice while preparing yogurt is suggested.

Keywords: bitter melon, yogurt, lactic acid bacteria, acidity