Optimization of apple drying conditions with multi- shelf solar powered dryer

Apple is one of the fruits with high production rate in our country. In addition to its fresh consumption, it is also frequently used as processed product such as apple juice, cider vinegar, marmalade and apple chips in the food sector. Drying process is one of the methods that commonly used to obtain long product shelf life by processing foods. In this thesis, the Starking Delicious which is the most produced apple kind in Turkey has been dried by using solar powered multi-shelf dryer. The dryer consisting of five shelves, weight and volume measurements were carried out every 30 minutes during the drying period determined as 300 minutes per shelf. According to the preliminary data, the shelf where the experiments will be carried out was determined. In addition to drying in a multi-shelf solar dryer, the results were compared by drying under shade and direct sunlight. Optimization of drying conditions in a multi-shelf solar dryer was determined by using Response Surface Methodology (RSM). Slice thickness, drying time and amount of fresh product were selected as a drying parameter. The responses to be optimized were determined as moisture loss, drying rate and shrinkage ratio. Considering seasonal conditions drying was done in June, July and August. At the end of the preliminary test, three-factor central composite design (CCRD) was used. The drying time, the amount of fresh apple slices and the apple slice thickness were determined as 58.6- 361 minutes (min), 32.7- 167 grams (g) and 3.98- 9.04 millimeters (mm), respectively. Experiments were conducted by creating experimental design. As a result of variance analysis (ANOVA) of the obtained data, second order models were formed and analytical solutions of these models and optimum drying conditions were found. The maximum moisture loss and shrinkage rate, the drying time for minimum drying rate is 159.042- 274 min, the fresh product quantity is 92.86- 105.72 g and the apple slicing thickness is 6.48- 6.667 mm.