The effect of ohmic heating on vacuum drying rate of sweet potato tissue.

Ohmically heating fruit and vegetable tissue has been shown to increase hot-air drying rate, shift desorption isotherms, and increase juice extraction yields with respect to untreated, conventionally heated, and microwaved samples. The objective of this study was to determine if ohmically heating sweet potato tissue would enhance the vacuum drying rate of these samples with respect to untreated samples. Sweet potato cubes were ohmically heated to three endpoint temperatures using three electrical field strengths and were then placed in a freeze dryer. Moisture content vs. time data were collected and modeled. Results showed that the vacuum drying rates of ohmically heated samples were faster than raw samples for most treatment combinations, and that the maximum reduction of drying time was 24%. Minimal ohmic treatment can result in a significant decrease in vacuum drying time, which could have important economic and product quality implications.