Influence of block freeze concentration and evaporation on physicochemical properties, bioactive compounds and antioxidant activity in blueberry juice

This study investigated the impacts of centrifugal block freeze concentration (CBFC) and evaporation processes on physicochemical properties, bioactive compounds and antioxidant activity applied to fresh blueberry juice. After three concentration cycles, the solutes were approximately 3.6 times to the initial condition (12 degrees Brix) and the final color (Delta E*>4.7) was darker than the fresh juice. In all cycles, CBFC obtained higher bioactive compound concentration than evaporation, with values, in the last cycle, close to 610 mg GAE/100 mL, 57 mg M3G/100 mL and 279 mg CEQ/100 mL for total polyphenol, anthocyanin and flavonoid content, respectively, causing a retention over 70%. Similarly, as the cycles progressed, DPPH assay presented values from 1916 to 5700 mu mol Trolox equivalents/L, which were higher than those reported by the treatment at high temperatures (1916 to 4600 mu mol Trolox equivalents/L), resulting in good antioxidant activity in the cryoconcentrates achieved at low temperatures. Moreover, a significant correlations between CIELab parameters, bioactive compounds and antioxidant activity were observed. Thus, CBFC is an interesting and novel technique to preserve important quality properties from fresh fruit juices.