Effect of sucrose on pH and thermal stability of anthocyanin, total phenolic content, and antioxidant activity of senduduk (Melastoma malabathricum) fruit extract

The research to study the effect of sucrose addition to the stability of anthocyanin, total phenolic and antioxidant activity of Melastoma malabathricum fruit extract during storage has conducted. The extraction was done by citric acid solution pH 3 at 60°C for 90 minutes in the dark with continuous shaking. The extract was adjusted to pH 3, 4, and 5 and added with 4, 7, and 10% sucrose, then stored at 7, 25, and 50°C. The total monomeric anthocyanin, phenolic content, and antioxidant activity were analyzed periodically. The total phenolic content and antioxidant activity of the extract were stable at all pH and temperature studied. The anthocyanin at pH 3 was very stable when stored at 7°C (t1/2 > 500 days) and significantly decreased as pH and stored temperature increased. The activation energy of anthocyanin in MM extracts were relatively high (84.99, 72.92, and 68.50 kJ/mol at pH 3, 4, and 5, respectively) indicating its sensitivity to the temperature elevation. The result suggested the MM extract as a potential colorant for cold acidic beverage and as antioxidant drink at pH 3-5 in wide range of storage temperature.