STUDY ON THE PARAMETERS’ VARIATION IN FRUITS DRYING PROCESS

The aim of the study was the pursuing of the parameters’ variation of fruits drying process.As materials  we use fruits with hard texture (apple, pear, quince) and as methods  we used the conventional drying (with air convection) and unconventional drying (with microwave and infrared radiation). We determined the variation of the following parameters : mass, product’s core temperature, humidity, drying time. We used  hydration as an estimation method of the drying products’ texture modification. The conventional drying one was done at 100°C for 120 minute. The microwave treatment was performed at 30% from oven maximum power – 900 W, in this case the drying period depending on each kind of fruit, so the thermic treatment lasted different intervals (30 minutes -  apple, 36 minutes - pear and 20 minutes - quince). The IR drying depends also on fruit type, as at  70°C the drying time for fruits was variable (apple - 49 minutes, quince - 25 minutes and 73 minutes for pear). The experimental determinations pointed out that the drying duration is sensitivly  decreasing as compared to the conventional drying process (~1/3) for the same content of moisture. Also, we found out that the quince texture is the hardest one leading to an easier drying and hydration process. The pear had very high water content and is a very rich source of carbohydrates, which are the principal responsible for the changes happened during the drying treatment, resulting in some colour transformation.