OPTIMIZATION OF VACUUM OVEN DRYER FOR APPLE DRYING

Abstract

Apple slices were dried in a vacuum oven at temperature 90 o C and 100 o C respectively. Samples dried had thickness 4mm, 5mm and 6mm of two varieties of apples viz. red delicious and golden delicious. Drying shrinkage was measured by means of a measuring cylinder with the help of distilled water. Color assessment was conducted based on the results obtained with the use of a reflective colorimeter. The kinetics of apple slices drying with vacuum oven dryer was described using exponential functions. The vacuum oven method considerably shortened total time of dying and decreased drying shrinkage. Apple slices dried with vacuum oven method demonstrated better by rehydrating properties manifested by absorption capacity, dry matter holding capacity and rehydration ability. Vacuum method drying, results in the browning of apples slices was found more in red delicious as compared to golden delicious. Experiments were conducted to categorize the effect of drying behavior of apple slices having thickness 4mm, 5mm and 6 mm were evaluated at two air temperatures viz. 90°C and 100°C and response variables namely Shrinkage, Rehydration Ratio, Colour change, Bulk Density and Over All Acceptability were determined and the detailed result and their variety are different. The authors have obtained, for apple cylinders (approximately 2.10-2 m diameter and 1.10-2 m height) vacuum dried and air dried (70 ° C), values for bulk density around 20 to 50% lower, suggesting that thin slices could make shrinkage easier. The results are in agreement with the findings of Maria Aparecida [2014] for “Vacuum drying of osmotic dehydrated apple slices” which suggests that the vacuum dried samples, presented higher densities and higher volume reduction, reflecting the collapsing of the solid matrix. The vacuum dried samples remained wet for longer time.