EFFECT OF PRE-TREATMENT ON THE DRYING KINETICS AND PRODUCT QUALITY OF STAR FRUIT SLICES

Start fruit (Avverhoa carambola) is rich in nutrients and contains dietary antioxidants which are beneficial to human health. Currently, the commercial potential of this fruit has not been fully explored especially in its dried form. The objectives of this research were to investigate the effect of pre-treatment on the drying kinetics and product quality of star fruit slices. The various pre-treatment methods investigated were hot water blanching and dipping in sugar solution. The star fruit was cut into thin slices (5 mm) for drying (60 degrees C-80 degrees C) using a hot air ventilated oven. Mathematical modelling showed that the Page model was able to describe the moisture diffusion process during drying. Effective diffusivity values were found within the order reported for most food materials (10(-8)-10(-12) m(2)/s). A decreasing trend in shrinkage ratios was observed with decreasing moisture ratios which corresponds to the greater rate of moisture removal especially at the falling rate period. Overall colour changes were more significant in the blanched samples which could be due to the non-enzymatic browning.