February 17/Campobasso, Italy/Electronics Business Journal -- "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 compunds and vitamin C content Trials were performed on stirred orange juice heated at different temperatures (60, 70, 75 and 85 degrees 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," scientists in Campobasso, Italy, report.
"The inactivation of heat sensitive fraction of PME, that verifies orange juice pasteurization, showed a z-value of 22.1 degrees C. Carotenoid content, responsible for sensorial and nutritional quality in fresh juices, decreased by about 13% after MW pasteurization at 70 degrees C for one minute. Total of seven carotenoid compounds were quantified during MW heating: zeazanthin and beta-carotene content decreased by about 26%, while no differences (P<0.05) were found for beta-cryptoxanthin in the same trial. A slight decrease in vitamin C content was monitored after MW heating," wrote L. Cinquanta and colleagues, University of Molise.
The researchers concluded, "MW heating with a fine temperature control could result in promising stabilization treatments."
Cinquanta and colleagues published their study in the Journal of Food Science ("Effect on Orange Juice of Batch Pasteurization in an Improved Pilot-Scale Microwave Oven." Journal of Food Science, 2010;75(1):E46-E50).
For more information, contact L. Cinquanta, University of Molise, Dipt Sci & Tecnol Agroalimentari Ambientali & Mic, Via F De Sanctis, I-86100 Campobasso, Italy.
From the March 1, 2010, Prepared Foods E-dition