Response Surface Optimization of Combination Drying (Osmotic-Hot Air Drying) of Apple Fruit Slices

Drying is one of the oldest methods for increasing the shelf life of foods. Nutritional value and water rehydration ability are two important quality parameters of dried products and so production of a product with the highest organoleptic and nutritional quality is the main purpose of osmotic dehydration process. In order to determine the effect of combination drying process (osmotic-hot air drying) on the quality attributes of golden delicious apple slices, the apple fruits were cut in the form of 5 mm thickness slices and immersed in different concentrations (0, 30 and 60 %w/w) of sucrose solution with the temperature of 500C. After removal of the apple slices from the osmotic solution in different processing times (60, 120 and 180 minutes), their surface was cleaned, dried and weighted. Water loss, solid (sugar) giant, moisture content and the total soluble solid (Brix) of the samples were calculated and analyzed with response surface method. The results showed that osmotic solution concentration, temperature and duration of osmotic process had significant effect on the moisture content, Brix, and the weight of the samples after osmotic process, and on the sensory attributes of the final product. Osmotic dehydration improved different quality attributes including color, taste and texture of the final product. During the osmotic dehydration process, moisture content and Brix of the samples were reduced and increased, respectively by increase of the osmotic solution's concentration and temperature. Osmotic solution concentration, temperature and duration of osmotic process had significant effect on the moisture content, Brix, and the weight of the samples after osmotic process, and on the sensory attributes of the final product