INFRARED DRYING OF LEMON SLICES

Abstract

A study was carried out to test and evaluate the use of infra-red radiation as heat energy source for drying lemon slices. A laboratory scale dryer was developed and tested at the laboratory of Agric. Eng. Dept. Fac. of Agric. Mansoura Univ. The experimental treatments included three different levels of radiation intensity (0.973, 1.093, and1.161 kW/m2), three different air temperatures (40, 50 and 60°C) and constant air velocity of 1 m/sec. The drying behavior was simulated using two different thin layer models (Lewis's and Henderson, and Pabis's). The studied models were compared with the obtained drying data, and the most suitable model for predicting the change in lemon moisture content during drying process was then assessed. Final quality of the dried lemons was also determined. The results show that, both studied models could describe the drying behavior of lemons satisfactorily. However, Lewis's model considered more proper for describing the drying behavior and predicting the changes in moisture content in terms of precision and application simplicity. The quality tests of the dried lemons showed that, radiation intensity of 0.973 kW/m2 with air temperature of 50°C recorded the best dried lemon quality in terms of higher retention of ascorbic acid (Vitamin C), citric acid and total soluble sugars.