Desorption of the Exotic Fruit Jujube (Ziziphus Jujube Mill) of Bulgarian Origin

Abstract

The present study determined the physico-chemical parameters of the exotic fruit jujube (Ziziphus jujube mill) of Bulgarian origin – pH of 4.62, refractometric dry matter of 31.6 %, dry matter (in weight) of 36.78 %, TTA (total titratable acidity) – citric acid – of 0.67 %, 0.70 % malic acid, 65.95 % moisture, 0.78 % fibre, 1.41 % protein, 23.65 % carbohydrate, 0.24 % fat and energy value of 428.44 kJ/102.4 kcal. Equilibrium moisture content and monolayer moisture content were established for desorption concerning eight water activities in the 0.1 0.9 range and the temperatures of 10 °С, 25 °С and 40 °С. The coefficients of the modified Oswin, Chung-Pfost, Halsey and Henderson models were obtained statistically. The modified Halsey model is recommended as a description of the desorption isotherms of jujube (Ziziphus jujube mill) since it corresponds to the criteria for model assessment and suitability. Via BET model linearization, the values of the monolayer moisture content for desorption at the temperatures of 10 °С 5.41 % d.b., 25 °С – 4.65 % d.b. and 40 °С 5.08 % d.b were determined.