Abstract:

The drying process of fresh apple slices with solar energy combined with abundant dry air resource in northwest China was investigated. The effects of apple slices thickness and loadage as well as air flow rate on water loss rate in apple slices were analyzed in single factor experiments. Based on this, the optimal value of three parameters were determined using orthogonal array design for reaching a good compromise between drying rate and productivity. Results indicated that both thickness and loadage of apple slices gave a significant influence on drying rate and productivity, whereas no significant influence of air flow rate was observed. As expected, a good compromise between drying rate and productivity was reached under the optimum drying conditions as follows: apple slice thickness 5 mm, loadage 5 kg/m2, and air flow rate 1.5 m/s. Totally 44.3 kg of dried apple slices containing 15% water were obtained from 500 kg of fresh ones after 84 hours of drying under such conditions. Compared with conventional hot air drying, this method consumed lower energy with 69.2% reduction.

Key words: apple, solar drying, energy saving