Drying behavior of two chestnut fruits (Castanea sativa Mill) varieties

Portugal is an important chestnut fruit (Castanea sativa Mill.) producer. However, its preservation represents a critical problem for both producers and industrials. Fruit weight loss and development of moulds during storage, as well as size variability, are some good examples. In this context, the fruit drying can be regarded as a preservation method, allowing its stabilization and subsequent production of other high value chestnuts based products.In Trás-os-Montes region (NE, Portugal), the most important varieties are Longal and Judia. Thus, in the present work, preliminary studies on the drying behavior of these varieties are reported. Upon harvest, the axial dimensions of all fruits were determined. The drying experiments were performed in a forced convection oven at 50 ºC. Moisture ratios, drying rates and apparent diffusivities were determined. Two models, namely the Page and Two-term, were applied. Simultaneously, colour (L*, a*, b*) of both varieties were measured along the drying process.When the calculated moisture ratios curves were regressed against the single-layer drying models, good fits were obtained. Adjusted r-squares higher than 0.90 were determined. Even though no differences were observed in the moisture ratios curves of the two varieties, the drying rates curves and the apparent diffusivities were slightly different. Nevertheless, only the falling rate period was observed. Furthermore, in terms of colour, no differences were observed along the drying time but the mean values of L*, a*, b* of Longal were always lower than those obtained with Judia. These data indicate that convective drying can be regarded as an industrial preservation alternative, with apparently reduced differences between both varieties