Coconut sugar is a food ingredient obtained from the thermal processed coconut sap. The browning rate during the thermal processing of coconut sap is related to the intensity of the Maillard reaction which can be observed through changes in pH and browning intensity. The increase in browning intensity is related to the formation of melanoidin which is reported to have an antioxidant activity. This study aimed to determine changes of antioxidant activity during the thermal processing of coconut sap into coconut sugar. The experimental design of this study was two factors randomized block design (RBD). The first factor was the type of preservative consisting of yellow gum from the mangosteen fruit (w/v) (P1) and sodium metabisulphite (w/v) (P2). The second factor was heating process time (0, 15, 30, 45, 60, and 75 minutes). The results showed that during the heating, the pH increased in the first 15 minutes and then decreased from the 30 to the 75 minutes in both treatments (P1 and P2). The browning intensity of coconut sap during heating showed an insignificant increase during heating process at 0, 15, 30, 45, and 60 minutes and then increased significantly at 45 and 60 minutes in both treatments (P1 and P2). The increase in total phenolic components during heating of coconut sap started at 30 minutes and increased significantly at 60 and 75 minutes in both treatments (P1 and P2). Changes in the antioxidant activity (% Radical Scavenging Activity) in coconut sap decreased in the first 15 minutes of heating but increased significantly at 60 to 75 minutes in both treatments (P1 and P2).

Keywords: coconut sap, preservatives, browning rate, antioxidant.