Functionality and characteristic changes of orange juice concentrates due to heat treatment

Fresh orange (Citrus sinensis (L.) Osbeck) juice was concentrated at 98±2°C for 0-24 hr, and periodically sampled concentrates of orange juice (COJs) were evaluated to investigate the changes in functionalities and characteristics during the heating process. Phenolic acids and flavonoids at T_(24) (after 24 h heating) were significantly higher than at T_0, (at time 0) except for rutin. The hesperidin content at T_(24) was 1.67 times that at T_0, and the sinensetin content increased 16.36 times over the 24-hour concentration period. EC_(50) values of reducing power at T_(20) and T_(24) were 2.13 and 5.67 times those at T_0 (p ＜ 0.05) respectively. The 2% and 3% COJs significantly inhibited the growths of Escherichia coli O157:H7 and Listeria monocytogenes, and the survival potential of E. coli in COJs was higher than that of L. monocytogenes. Moreover, COJs (at 100 μg/mL level) significantly suppressed TNF-α (1 ng/ml)- induced ICAM-l protein expression.