Thermodynamic sorption properties, water plasticizing effect and particle characteristics of blueberry powders produced from juices, fruits and pomaces

•Water sorption isotherms of different blueberry powders were fitted to GAB model.•Water sorption process of blueberry juice powders containing WPI was spontaneous.•Blueberry pomace powders had the weakest affinity with water molecules.•Water had the weakest plasticizing effect on blueberry pomace powders.•Water sorption properties were affected by chemical composition and particle size.

Fresh blueberries were processed into three powder forms through freeze drying, namely juice powders containing 8% whey protein isolate (WPI), fruit powders and pomace powders. The water binding behaviors of these blueberry powders were studied through thermodynamic sorption analysis, quantification of water plasticizing effect and characterization of particle properties. The GAB model was successful in fitting the water sorption isotherms of blueberry powders at 20, 35 and 50 °C. Thermodynamic studies revealed that the sorption processes of all the samples were enthalpy-driven and only the sorption process of blueberry juice powders containing WPI was spontaneous (ΔG < 0). Meanwhile, the highest absolute integral entropy values for blueberry juice powders containing 8% WPI, fruit powders and pomace powders were obtained at the moisture contents of 0.011, 0.013 and 0.024 kg H2O/kg dried matter, respectively. Furthermore, the plasticizing effect of water on blueberry pomace powders was the weakest, since its k value of Gordon-Taylor model was lower than that of other samples. These results implied that blueberry pomace powders had the weakest affinity with water molecules. Thus, blueberry juice powders containing 8% WPI and fruit powders were suggested to be stored at a lower relative humidity than pomace powders. Besides, it was temporarily found that the difference in water binding capacity among blueberry powders was associated with the distribution of functional groups derived from sugars and acids, as well as the particle size. All the results can be a reference for drying, packaging, storage and distribution of blueberry powders in practical applications.

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