Citation:
Abstract:
This paper presents an experimental study of the shrinkage phenomenon of apple slices during two types of drying, namely: static drying (in an electric regulated oven) and open sun drying (naturally, on one tray) under the meteorological conditions of Ouargla city in the south east of Algeria. In the oven, the experiments are performed with three different temperatures (50, 60 and 70 °C). The effect of the water content loss of the fruit samples on the dimensions (thickness and diameter) and on the volume are considered. During the static and sun drying, the results show that the volume decreases by 80% and 86% of its initial values, respectively. During the static drying, the diameter of each apple slice shrinks by 20% and the thickness by 70 % of the initial values. Not far from these values, the diameter decreases by 25% and the thickness by 76% of the initial values during the open sun drying. In addition, the drying of apple slices shows an anisotropic shrinkage independently of temperature and therefore a unique shrinkage equation is proposed for each of both methods of drying. Finally, the importance of considering the phenomenon of shrinkage of the apple fruit during drying is shown in the Krischer curves.
Keywords: Apple slices, Experimentation, Shrinkage. Static drying, Open sun drying.