Influence of drying method on density and porosity of pears

In the present work the moisture content and apparent density of pears were measured during the drying of pears under different conditions: peeled uncut pears dried by direct sun exposure (a traditional method used in Portugal) and small slices of pear pulp dried in a ventilated drying chamber at constant temperature of 30 degrees C. Using the experimental results obtained was possible to estimate the parameters of the model proposed by Zogzas et al. (1994), and make previsions of bulk and particle densities as well as porosity variations during drying. It was possible to conclude from this work that, in spite of being substantially different, the two drying procedures used can be considered equivalent with respect to the structure product developed. In fact, the model parameters were very similar in the two situations tested and the evolution of porosity was also very analogous. Furthermore, it was possible to conclude that the pears developed relatively low porosities during drying, as a consequence of the slow drying rates used in both situations, and the high degree of shrinkage observed.