Assessment of mass exchange during osmotic dehydration of dragon fruit

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.

Effect of thin layer drying on quality parameters of betel leaf (Piper betle L.)

Betel leaf or “Paan” is contemplated as “a neglected green gold of India” due to its nutritional, financial, medicinal, social and cultural values. However, surplus production of the leaves during the glut season and lack of adequate storage facilities compel the betel leaf growers to sell it at a through away price. Therefore, the current study was taken up to enhance the shelf life of the leaves by four different drying methods like shed drying, hot air oven drying, vacuum drying and freeze drying. Eight different thin layer drying models were studied and compared based on coefficient of determination (R2), root mean square error (RMSE) and chi square. The results showed that Page model was the best fitted model for hot air oven drying and vacuum drying methods, whereas Peleg model and Two Term model were found to be best fitted for shed drying and freeze drying methods, respectively. The results also revealed that both freeze drying and shed drying are the best techniques for retention of essential oil after drying. However, shed dried leaves were found to be most preferable by the panelists during organoleptic evaluation. Therefore, these dried leaves can be used for manufacturing of packaged mouth fresheners, betel leaf flavoured soup, etc.