A four factors three level Box-Behnken response surface design was employed in this study to investigate and optimize the effect of process variables (osmotic solution concentration, fruit to liquid ratio, temperature and dehydration time) on mass transfer properties such as weight reduction, solute gain, water loss, rehydration ratio, shrinkage and overall acceptability of the osmotically dehydrated amla cubes. The cubes of uniform size (10 mm ? 10 mm ? 10 mm) were impregnated into sugar solution of different solution concentration (30-50? Brix), temperature (30-50?C), fruit to liquid ratio (1:5 - 1:15 g/ml) and time (30-180 min). It was observed from the results that the process variables have significant effect on osmotic dehydration process. The optimum condition was found to be: sugar concentration of 50? Brix, solution temperature of 30?C, fruit to liquid ratio of 1:5 g/ml and immersion time of 133 min. respectively. The microstructural changes during osmotic dehydration were also investigated using scanning electron microscopy (SEM).

Keywords: M. acuminata slice, Osmotic dehydration, Mass transfer, OptimizationThe mass transfer characters were quantitatively investigated during osmotic dehydration of Musa acuminata slices using response surface methodology with sugar concentration of 30-50 o Brix, temperature of 30-50℃, osmotic dehydration time of 30-180 minutes and sample to solution ratio of 1:5-1:15 g/ml as the independent process variables. Quadratic regression equations were obtained to describe the effects of independent process variables on the weight reduction (WR), solid gain (SG) and water loss (WL). From the results, it was found that, all the independent variables had significant effect on mass transfer characteristics during osmotic dehydration of banana slices. The optimal condition for osmotic dehydration of M.acuminata slices was found to be: osmotic solution concentration of 43 o Brix, sample to solution ratio of 1:10 g/ml, osmotic solution temperature of 50℃ and osmotic dehydration time of 164 minutes respectively. ARTICLE INFO

The objective of this present study is to evaluate the effect of process parameters, such as salt concentration (1-5%), sample to solution (SS) ratio (1:5-1:15 g/mL), osmotic solution temperature (30-50C) and osmotic treatment time (30-180 min), on the mass transfer parameters (weight reduction, solid gain and water loss) during osmotic dehydration of Momordica charantia slices. A three-level, four-factor Box-Behnken response surface design was used for the study and the process was optimized using regressional-desirability method. The results exhibited that process variables hold considerable effect on the osmotic dehydration process. Based on the method of desirability, the most favorable optimal conditions were found to be osmotic solution concentration of 3.5%, SS ratio of 1:13 g/ mL, osmotic solution temperature of 46C and osmotic dehydration time of 138 min. The microstructural changes during osmotic dehydration were also investigated using scanning electron microscopy. PRACTICAL APPLICATIONSThe process of osmotic dehydration can be used for the preparation of shelf-stable products for the purpose of obtaining a more physicochemically and microbiologically stable final product. Momordica charantia (bitter gourd) is one of the popular vegetables because of its high nutrition and medicinal value. However, the shelf life of bitter gourd is very short, and hence, it cannot be stored for a long time. Osmotic drying of bitter gourd helps preserve its nutrition for a long time. The quality of pre-osmosed bitter gourd is superior than the one obtained from conventional dehydration. The osmotically dehydrated bitter gourd can be used for cooking as vegetables after rehydration. This study puts forward some practical references for further research efforts and also for commercial applications of osmotic dehydration.

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