Effect of drying on physicochemical properties and antioxidant activities of bilimbi (Averrhoa bilimbi L.) slices / Zai Suhairah Arshad @ Arshah

In this study, drying rate of bilimbi slices is investigated using syrup blanching as pre-treatment method under three different temperatures. Experiments were conducted using convection oven at temperature from 40, 50 to 60 °C. The value of the moisture was recorded at one hour interval until achieving 20% moisture content. The effect of drying temperature on the water activity, moisture content, colour, texture, total ash, vitamin C and antioxidant properties of the bilimbi slices were also determined. The result showed that the treatment of bilimbi slices with syrup increase the rate of drying as compared to those untreated slices. As the temperature increase, significant (p<0.05) decrease in drying period was obtained. The application of syrup treatment to the slices gave low water activity value (0.61±0.00) and also reduced moisture content percentage (20.13±0.03), vitamin C content percentage (4.43±0.03) and shrinkage percentage (89.30±0.06). However, in contrast, it helps retained the bilimbi slices colour (45.72 for L* value, -1.09 for a* value and 24.15 for b* value) and also the total percentage of ash content (65.42±0.88), and contribute to the firmness of the bilimbi slices’ texture (10.26 ± 0.81). Decreasing in total phenolic content of dried bilimbi slices was reported as the drying temperature increase. The antioxidant activity of the bilimbi slices after syrup blanched was significantly lowers (56.27±0.11) percent as compared with the control at 40 oC.