بررسی عوامل مؤثر بر رسوب پودر آب پرتقال بر دیواره خشک‌کن پاششی

The difficulties in the storage of fruit juice and the use of juice powder in various food processing industries has made the juice powder attractive to consumers and producers. Making powder from fruit juice is one of the most complex methods of fruit processing.The hygroscopic nature of fruit juice component and its thermoplastic properties has caused the drying time control and the transportation of the product from the drying zone to the next stage to become very difficult. In this investigation with laboratory spray dryer, the effective parameters on orange juice powder deposit on the wall of the spray dryer was studied. The results indicate that the powder can not be made without the use of additives. Using liquid glucose as an additive to orange juice concentration increased the dryer performance and reduced the wall deposit considerably. With the help of liquid glucose additive, spray dryer optimum conditions were obtained with a feed flow rate of 15 ml/min, inlet air temperature of 130oC and outlet air temperature of 85oC. The results from the statistical analysis of the experimental data show that the parameters of inlet air temperature and feed flow rate have significant effects on the dryer yield and wall deposit both individually and jointly. By increasing inlet air temperature and feed flow rate, the dryer yield decreased but wall deposit increased. In spite of using suitable additives, the wall deposit was still in the range of 14 to 65 %. The results of experiments indicate that the main cause of wall deposit can be attributed to the wall high temperature. It is, therefore, necessary to keep the wall temperature below the orange powder sticky point temperature to prevent rising temperature in wall deposit. For the orange powder containing 2% moisture, the sticky point temperature is 44oC. To control the wall temperature, a dryer with double partition wall chamber and a cooling system is proposed.