Influence of pulsed microwave on betacyanins, betaxanthins and physical properties during drying of red beetroot

Abstract

This study aimed to investigate the effect of pulse ratio and microwave power during drying of red beetroot using combined intermittent microwave – hot air at low temperature (40˚C). A significant decrease in drying time was observed by increasing the microwave power from 360 to 900 W and decreasing the pulse ratio from 6 to 2. The highest Deff was obtained at a microwave power of 900 W and a pulse ratio of 6. Dried red beetroots at the microwave power of 900 W and a pulse ratio of 6 had the lowest shrinkage and the highest rehydration. Moreover, the apparent density of the dried samples decreased by increasing the microwave power and pulse ratio. The specific energy consumption was reduced by increasing the microwave power and the pulse ratio. By increasing microwave power and pulse ratio, the content of betacyanins and betaxanthins increased up to 79.47 and 44.20%, respectively. Furthermore, the samples dried at the power of 900 W and a pulse ratio of 6 showed the lowest microstructural collapse. In total, the results of this study showed that industrial dried products with good quality could be produced by considering an appropriate pulse ratio and applied power.