Assessment of mass exchange during osmotic dehydration of dragon fruit

Abstract

Water loss, weight reduction, solute gain and water activity were investigated during osmotic dehydration of dragon fruit in binary solution of sucrose and sodium chloride using Response Surface Methodology. Experiments were designed according to Central Composite Rotatable Design (CCRD) with four factors Temperature (30°C to 50°C), sucrose concentration (45% to 55%w/w), NaCl concentration (2.5% to7.5% w/w) and time (150 to 390 min).  Experiments were conducted in a temperature controlled environmental chamber with solution to sample ratio of 10/1 (w/w).

       Analysis of variance (ANOVA) was performed to check the adequacy of the fitted models.  The response surface plots showing the interaction of variables were developed in Design-Expert 9.0.1.  For every response linear variables were found more significant than quadratic variables.  Optimum conditions for maximum water loss and weight reduction and minimum solid gain and water activity corresponds to temperature of 30°C, sucrose concentration of 55%, NaCl concentration of 6% and time of 270 min.  Desirability was 0.81. At this condition, water loss, solid gain, weight reduction and water activity were recorded as 46.35 g/100 g, 5.48 g/100 g, 40.87 g/100g and 0.843 respectively.