Influence of Ultrasound Intensification on the Continuous and Pulsed Microwave during Convective Drying of Apple

ABSTRACT

Drying is an essential unit operation in the food industry, with novel technologies introduced day after day. This study aimed to investigate different drying methods of apple using the continuous microwave, pulsed microwave (PM), and convective hot-air (CH) with and without ultrasound (U) pretreatment. Results showed that simultaneous U – PM – CH drying significantly reduced drying time. Shrinkage of the samples decreased when microwave power and pulse ratio were increased. Bulk density reduced by increasing the U duration and pulse ratio. The maximum raise in rehydration (39.35%) was seen in the dried samples pretreated at a higher U duration (30 min). By raising the U time and microwave power, specific energy consumption reduced by 30.05 and 41.36%, respectively. Overall, the U – PM – CH drying enhanced the quality of the dried apples and could be suggested for commercial drying industries.

KEYWORDS:

• Drying kinetics
• energy consumption
• hybrid drying
• rehydration
• shrinkage