Journal of Food Engineering, Vol.210, 91-97, 2017
Effects of water and maltodextrin on the glass transition temperature of freeze-dried mango pulp and an empirical model to predict plasticizing effect of water on dried fruits
Effects of water and maltodextrin on the glass transition temperature (T-g) of freeze-dried mango pulp were investigated systematically using differential scanning calorimetry. The T-g of anhydrous mango pulp increased with maltodextrin content, but an abrupt T-g-change was observed between 0.6 and 0.7 maltodextrin weight fraction. The T-g of mango pulp-maltodextrin mixtures decreased with an increase in water content, and water content and water activity at T-g = 25 C-omicron were increased by the addition of maltodextrin. The effect of water content on the T-g was analyzed with the Gordon-Taylor equation, and a fitting parameter (k) was obtained. By investigating the relationship between the anhydrous T-g and k for the mango pulp-maltodextrin mixtures, and many other kinds of dried fruits reported previously, it was found that the relationship could be described by two linear equations. This result will be useful for predicting the T-g-depression of dried fruits induced by water plasticizing. (C) 2017 Elsevier Ltd. All rights reserved.
Keywords:Water sorption isotherm;Glass transition temperature;Water plasticizing;Freeze-drying;Differential scanning calorimetry