Effect on Orange Juice of Batch Pasteurization in an Improved Pilot-Scale Microwave Oven
2010
Cinquanta, L. | Albanese, D. | Cuccurullo, G. | Di Matteo, M.
The effects on orange juice batch pasteurization in an improved pilot-scale microwave (MW) oven was evaluated by monitoring pectin methyl-esterase (PME) activity, color, carotenoid compounds and vitamin C content. Trials were performed on stirred orange juice heated at different temperatures (60, 70, 75, and 85 °C) during batch process. MW pilot plant allowed real-time temperature control of samples using proportional integrative derivative (PID) techniques based on the infrared thermography temperature read-out. The inactivation of heat sensitive fraction of PME, that verifies orange juice pasteurization, showed a z-value of 22.1 °C. Carotenoid content, responsible for sensorial and nutritional quality in fresh juices, decreased by about 13% after MW pasteurization at 70 °C for 1 min. Total of 7 carotenoid compounds were quantified during MW heating: zeaxanthin and β-carotene content decreased by about 26%, while no differences (P < 0.05) were found for β-cryptoxanthin in the same trial. A slight decrease in vitamin C content was monitored after MW heating. Results showed that MW heating with a fine temperature control could result in promising stabilization treatments.
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