Protection of polyphenols in blueberry juice by vacuum-assisted block freeze concentration

Block freeze concentration allows produces high-quality cryoconcentrates with important protection of valuable components from fresh fruit juices. The aim of this study was to investigate the use of vacuum assisted block freeze concentration under different experimental conditions to protect polyphenols in the elaboration of concentrated blueberry juice. Fresh blueberry juice was radial or unidirectional frozen at 20 and -80 degrees C for 12 h and vacuum process was performed at 80 kPa during 120 min. Results showed a significant solute increased in the concentrated fraction in all treatments, and the best treatment was - 20 degrees C/unidirectional with a value of approximate to 63 degrees Brix, equivalent to an increase of 3.8 times in the total polyphenol content (76% of retention). The color of concentrated samples was darker than the initial sample, with Delta E* values of >25 CIELab units in all treatments. The vacuum-assisted block freeze concentrations was an effective technology for protecting polyphenols and obtain a concentrated with a higher concentration of solids from blueberry juice, as well as interesting values of process parameters. (C) 2017 Elsevier Ltd. All rights reserved.