Quality preservation of orange concentrate by using hybrid ohmic - Vacuum heating.

The effect of ohmic-vacuum heating conditions (OHVC) was evaluated on quality parameters during concentration process of orange juice and compared with ohmic heating process under atmospheric conditions (OHAC) and conventional vacuum heating (CVH). The decline of vitamin C in OHVC treatments (10-29.2%) was lower than the OHAC (18.0-38.8%) and CVH (47.4%). Changes of pH for OHVC were lower than OHAC and CVH. The difference in total phenol content of fresh and concentrated juice was 8.0-21.3% for OHVC and 18.5-42.8% for OHAC and 49.6% for CHV. Antioxidant capacity of treatments was lower than the fresh sample at same water content. Increasing of voltage gradient had a positive effect on the saving of vitamin C and total phenol and processing time. Finally, it can be resulted that the combine of vacuum treatment with ohmic heating (as hybrid ohmic-vacuum heating) could maintain food quality parameters.