Physicochemical Properties of Jujube Powder from Air, Vacuum, and Freeze Drying and Their Correlations

Physical and chemical properties of jujube powder with different powder sizes prepared by different drying methods were determined, and correlations of the properties were statistically analyzed. Air-, vacuum-, and freeze-dried (AD, VD, and FD, respectively) jujube were milled and sieved to produce powders. Powder size, morphological characteristics, color, volatile profile, moisture sorption isotherm, water solubility, rehydration, total sugar content, and polyphenol content of the powder were determined. Hunter L, a, and b, degree of browning, and volatile profile varied depending on drying methods. Moisture sorption isotherms exhibited typical Type Ⅱ sigmoidal shape. Polyphenol content was highest in AD powder (2.6±0.1 mg/g). Powder size, morphology, water solubility, and total sugar content were not different by different drying methods. Correlations identified among the properties indicate rehydration of the powder could be maximized by controlling particle size and water activity of the powder. Rehydration and powder size of AD, VD, and FD powder were significantly correlated (p less than 0.001) (R²=0.92, 0.88, and 0.94, respectively). Property correlations determined could be useful in customizing properties of jujube powder and increasing commercial uses of the powder.