Study on the drying kinetics and quality parameters of osmotic pre-treated dried Satkara (Citrus macroptera) fruits

Thin layer drying of the Citrus macroptera samples pretreated with 2% NaCl, 10% sucrose, and 10% glucose solution was accomplished in a humidity chamber to evaluate the effects of drying temperatures (45, 50, and 55 degrees C) on drying kinetics and check the relative biochemical properties, and the microbial load. The drying data were fitted using the moisture ratio (MR) to predict the drying kinetics. The fitness was measured for the Newton, Henderson and Pabis, and Page model. The changes in water loss were fitted to Peleg model and Weibull distribution model to predict the water loss distribution during drying. Page's mathematical model was selected as the best-fitted model for explaining drying kinetics based on the highest R-2 and the lowest Root Mean Square Error (RMSE) values. The Peleg's model was found to fit well for equilibrium moisture content at different temperatures. Drying of the Satkara samples at 45 degrees C showed better results in the retention of color, total flavonoid content, total phenolic content (TPC), vitamin C, citric acid, vitamin B-1, and B-6 at different pre-treatment conditions. Antioxidant activity was significantly higher (p < 0.05) in the dried Satkara slices dried at 55 degrees C. Among the B-vitamins, vitamin B-3 was comparatively stable during the drying process. Sucrose pre-treated samples showed better results in the retention of color, TPC, citric acid, ascorbic acid, and antioxidant activity. The microbial load (bacterial load: 3.4 x 10(3) to 1.5 x 10(3) CFU/g and fungal load < 10(4) CFU/g) was at an acceptable level in all the dried samples. According to the findings, drying of the Satkara at 55 degrees C pretreated with 10% sucrose was comparatively better while considering the minimum time required for drying and considerable loss of nutritional factors.