| In the recent past, ohmic heating has been used as a method to deliver potentially higher quality products in aseptic processing. Peeling is one of the important operations in the tomato industry to ensure good final product quality. Any enhancement would be desirable, especially the improvement of lye peeling to reduce environmental impact. Therefore, one of our aims is to determine if ohmic treatment might be an alternative method for tomato peeling. We find that in terms of quality of peeling, the best conditions of ohmic peeling are: 0.01% NaCl with 8060 and 9680 V/m, and 0.03% NaCl with 6450 and 8060 V/m. Next objective is to investigate a possibility of using a combination of lye peeling and ohmic heating. We find that 0.01/0.5% NaCl/KOH at 2020 V/m is the best condition, which is not significantly different from conventional lye peeling at 7% NaOH and 7% KOH, in terms of quality, weight loss, and peel cracking time. However, we find that there is no improvement using NaCl/CaCl2 and NaCl/NaOH/CaCl2 mixtures. Next objective is to investigate the temperature distribution inside the tomato via a computational simulation at the best and worst peeling quality conditions in terms of thermal damage of tomato flesh. We find that, at the flesh just underneath the skin, the temperature of the worst condition is higher with a deeper thermal damage expected in the interior flesh than that of the best condition. Finally, we investigate whether the use of a rotating electric field could be used to improve weight loss and peeling quality. We find that the rotating electric field is ineffective compared with the fixed orientation electric field. The results suggest that at 25% duty cycle (822-watt power input), a 6 kHz fixed orientation field yields the best peeling quality and less weight loss than the corresponding rotating electric field. Further, at 25% duty cycle with a fixed orientation field, the weight loss of the 6 kHz field is significantly less than that of the 2 kHz field. |
