Effect on orange juice of batch pasteurization in an improved pilot-scale microwave oven.
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 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. 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 1 min. Total of 7 carotenoid compounds were quantified during MW heating: zeaxanthin 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. Results showed that MW heating with a fine temperature control could result in promising stabilization treatments.
Cinquanta
L
L
Dipt. di Scienze e Tecnologie Agro-Alimentari Ambientali e Microbiologiche, Univ. del Molise, Via F. De Sanctis, Campobasso, Italy. cinquant@unimol.it
Albanese
D
D
Cuccurullo
G
G
Di Matteo
M
M
D001205:Ascorbic Acid / Q000032:analysis; D001628:Beverages; D032084:Citrus sinensis / Q000737:chemistry* / Q000528:radiation effects; D065366:Cryptoxanthins; D005519:Food Preservation / Q000379:methods*; D006801:Humans; D008872:Microwaves; D009753:Nutritive Value; D010865:Pilot Projects; D013649:Taste; D024341:Xanthophylls / Q000032:analysis; D065146:Zeaxanthins; D019207:beta Carotene / Q000032:analysis
D065366:Cryptoxanthins; D024341:Xanthophylls; D065146:Zeaxanthins; D019207:beta Carotene; D001205:Ascorbic Acid