الفهرس 
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Abstract
A study was carried out to test and evaluate the use of infra-red radiation as heat energy source for drying sliced and whole lemon fruits. A laboratory scale dryer was constructed 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, and 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 compared for fitting the obtained drying data and the most suitable model for predicting the change in lemon moisture content during the drying process was assessed. Final quality of both the dried whole lemons and the sliced lemons were also determined. The results show that, both studied models could describe the drying behavior of lemons satisfactorily. However, the 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 sliced and whole dried lemons showed that, radiation intensity of (0.973 kW/m2) and (1.093 kW/m2) with drying air temperature of 50°C recorded the best dried lemon quality for the sliced and whole dried lemons respectively, in terms of higher retention of ascorbic acid (Vitamin C), citric acid and total soluble sugars.