INFRARED DRYING OF FULL LEMON FRUITS

A study was carried out to test and evaluate the use of infra-red radiation as heat energy source for drying full lemon fruits. 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 (0.973-1.093-1.161 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 com-pared with the obtained drying data, and the most suitable model for predicting the change in lemon moisture during drying process content 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, the Lew-is s model considered more proper in terms of precision and application simplicity for describing the drying behavior and predicting the changes in moisture content. The quality tests of the dried lemons showed that, radiation intensity of 1.093 kW/m^2 with air temperature of 50°C recorded the best dried lemon quality in terms of higher reten-tion of ascorbic acid (Vitamin C), citric acid and total soluble sugars.