title: Influence of three different concentration techniques on evaporation rate, color and phenolics content of blueberry juice.
abstract: The present study was undertaken to assess the effects of three different concentration processes open-pan, rotary vacuum evaporator and microwave heating on evaporation rate, the color and phenolics content of blueberry juice. Kinetics model study for changes in soluble solids content (°Brix), color parameters and phenolics content during evaporation was also performed. The final juice concentration of 65° Brix was achieved in 12, 15, 45 and 77 min, for microwave at 250 and 200 W, rotary vacuum and open-pan evaporation processes, respectively. Color changes associated with heat treatment were monitored using Hunter colorimeter (L*, a* and b*). All Hunter color parameters decreased with time and dependently studied concentration techniques caused color degradation. It was observed that the severity of color loss was higher in open-pan technique than the others. Evaporation also affected total phenolics content in blueberry juice. Total phenolics loss during concentration was highest in open-pan technique (36.54 %) and lowest in microwave heating at 200 W (34.20 %). So, the use of microwave technique could be advantageous in food industry because of production of blueberry juice concentrate with a better quality and short time of operation. A first-order kinetics model was applied to modeling changes in soluble solids content. A zero-order kinetics model was used to modeling changes in color parameters and phenolics content.
authors.affiliation: Food Engineering Department, Engineering Faculty, University of Gaziantep, 27310 Gaziantep, Turkey.
authors.forename: Aysel
authors.initials: A
authors.lastname: Elik
authors.affiliation: Food Engineering Department, Engineering Faculty, University of Gaziantep, 27310 Gaziantep, Turkey.
authors.forename: Derya Koçak
authors.initials: DK
authors.lastname: Yanık
authors.affiliation: Food Engineering Department, Engineering Faculty, University of Gaziantep, 27310 Gaziantep, Turkey.
authors.forename: Medeni
authors.initials: M
authors.lastname: Maskan
authors.affiliation: Food Engineering Department, Engineering Faculty, University of Gaziantep, 27310 Gaziantep, Turkey.
authors.forename: Fahrettin
authors.initials: F
authors.lastname: Göğüş
keywords: Blueberry juice; Color; Evaporation rate; Microwave; Phenolics content