1 Evaluation of the colour of pears dried using different methods

Pears of the variety S. Bartolomeu (Pyrus communis L.) have been used over the years in Portugal to produce a traditional dried pear known as “pera passa”. It is a very much appreciated dried fruit, despite the drop in the production that has occurred during the past years. The processing comprehends a solar drying performed at open air, with obvious disadvantages, either concerning the drying efficiency or the sanitary quality of the final product, taking into account that the products are exposed to multiple contamination agents. Obviously, these handicaps do not guarantee the necessary quality and sanitary standards for commercialization. Therefore, in the past years some work has been done in order to encounter alternative reliable drying methods that can replace the traditional drying. These include the use of solar stoves, either with forced air convection or with natural convection, and a drying tunnel with air heated though a solar collector. However, not only the drying efficiency and economic or sanitary aspects matter in the present case, since this particular product is very much appreciated for its unique colour. In fact, these pears in particular, when dried by the traditional method, develop a reddish colour that is not found in other varieties of pears, and this aspect constitutes one of the quality parameters for their acceptability by the consumers