PJB-2018-771
Statistical evaluation of shelf stability of Dhakki dates utilizing equilibrium moisture contents and water activity isotherms
Young Jae Jeon
Abstract
This study was designed to estimate the water sorption isotherms for date fruits of Dhakki cultivar. The sorption isotherms were evaluated using static method of saturated salt solutions at 15°- 40°C whereas Tg determined applying differential scanning calorimetry (DSC) and correlated to figure into a state diagram. Net isosteric heat of water sorption was calculated using Clausius–Clapeyron equation. Equilibrium moisture contents increased nonlinearly with water activity at a constant temperature however given a cross-over with temperature rise. The experimental data fitted well with GAB sorption model reported for high sugar foods. The Tg is linearly related with Emc (% dry mass) given a high value of coefficient of regression. The Tg value at 25°C corresponded to 0.077 Aw and 5% equilibrium moisture contents. The isosteric heat and Tg decreased with increase in water activity validating the moisture acted as plasticizer. Freshly cured dates holding 0.6 Aw with 25% moisture are considered microbiologically safe for distribution at room temperature and consumption.
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