Effect of ion exchange resin weight and extract flow rate on the properties of starfruit (Averrhoa carambola L.) extract
This research was carried out to determine the effect of resin weight and extract flow rate during deacidification on the oxalic acid content, physicochemical and antioxidative properties of starfruit extract. Nine treatments which consisted of different combinations of resin weight (3, 5 and 8 g) and flow rate (6, 9, and 12 ml/min) were carried out. Parameters measured were oxalic acid content, pH, total polyphenol content, vitamin C and free radical scavenging activity (DPPH). Increasing the weight of resin and decreasing the flow rate increased the pH of starfruit juice. The pH of starfruit juice increased from 3.6 for control to 9.9 for sample deacidified with 8 g of resin at flow rate of 6 ml/min. Oxalic acid content of starfruit juice showed a significant (p<0.05) reduction with deacidification. Deacidified samples showed significant decrease (p<0.05) in total polyphenol content, vitamin C and free radical scavenging activity compared to control. However, different combinations of resin weight and flow rate during deacidification did not have any significant effect (p>0.05) on total polyphenol content, vitamin C content and free radical scavenging activity of starfruit juice.