88E-23 |
Air relative humidity effect on drying kinetics of Lambertin apricots |
I. N. RAMOS, Escola Superior de Biotecnologia, Universidade Católica Portuguesa, Rua dr. António Bernardino de Almeida, Porto, 4200-072, Portugal and C. L. M. Silva. Air drying of fruits is widely used all over the world, although it has been loosing importance due to the development of new technologies. There are many factors affecting fruit drying, and consequently the quality of the final dried product. Air temperature and velocity are the most studied parameters, that influence drying kinetics, and air relative humidity is usually neglected. However, air humidity is also a very important parameter. Nevertheless, there is lack of information about the effect of this parameter on drying kinetics. Therefore, the main objective of this work was to study the effect of air relative humidity on drying kinetics of Lambertin apricots. This study was carried out with a pilot plant tray drier, with forced air, and control of air temperature, velocity and humidity. Lambertin apricots (Prunus Armeniaca) were cut in half and pre-treated with sodium metabisulfite 5%, to avoid darkening. Air drying was performed at 40C, 0.60 m/s and different relative humidities: 25.3%, 32.6%, 42.1% and 51.6% (mean values). Experimental data was fitted to the Exponential model. It was verified that, besides influencing the final equilibrium moisture content, air relative humidity also affects the drying rate constant. For instance, decreasing air humidity from 51.6% to 25.3% originates a rise of 47% on drying rate constant, and a 41% decrease on total drying time. The humidity effect on drying rate is usually neglected, because it is obscured in the temperature effect. Although air relative humidity affects drying rate to a lesser extent than air temperature, it has a great influence on total drying time. This is extremely important in terms of economical aspects. For instance, during solar drying it is essential to keep a low air humidity level in order to accelerate production.
Session 88E, Fruit & Vegetable Products: Processing
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