This study reports the effectiveness of various concentrations of ascorbic acid, citric acid and oxalic acid used as acidulants to regulate activities of antioxidant, polygalacturonase, pectin methylesterase and polyphenol oxidase of fresh-cut wax apple (Syzygium samarangense). The samples of fresh-cut wax apple, cut in wedges (1/8), were dipped into ascorbic acid, citric acid and oxalic acid at four different concentrations (0, 0.5, 1.0, 1.5 and 2.0%) for 1 min. The changes in the parameters were monitored for nine days while they are in storage at 4�C. Fruit treated with oxalic acid contained the highest antioxidant activity, followed by those treated with citric acid and ascorbic acid. The activity of antioxidant increased with the increasing storage period. Similar effects of acid treatments were detected for total phenolic contents. There was no effect of types of organic acids on polygalacturonase activity but acid dipping reduced the activity of the enzyme. In contrast, types of acids and acid concentration did not alter the activity of pectin methylesterase activity. Activity of pectin methylesterase in fruit sampled on day 6 and 9 were higher than those of the earlier dates. Similar pattern of effects of acid treatment were observed for polyphenol oxidase activity. � 2015 Asian Network for Scientific Information.