Experimental investigation of the relationship between the core temperature of hazelnuts and ambient conditions in the drying process

Abstract

Hazelnut, which is one of the major export products in Turkey, can be generally evaluated and preserved in dried form. There are difficulties encountered in keeping its internal temperature and humidity constant at desired values because it is commonly exposed to solar energy and dried in outdoor environment. Especially due to rainy and variable weather conditions, it is possible to decay and decompose the inner hazelnut without full drying. Because of improper drying, hazelnuts are known to lose their nutritional value. In this study, the attitude of hazelnut was observed in different ambient conditions and the drying temperatures in hazelnut drying processes performed under laboratory conditions. For this purpose, insulated drying booths for experimental setup were created and air circulation was provided for forced convection by fans. Approximately equal sized hazelnuts were placed in the cabin. The main properties of hazelnuts before and after conditioning were recorded for each experiment. The internal temperature, surface temperature and mass loss of the hazelnut were evaluated together. Drying attitudes were recorded for different types of hazelnuts (round, pointed and long). The optimum ambient conditions and drying temperatures were determined during hazelnut drying process. Drying times at 25-50 0C temperature were determined for hazelnuts with 60% relative humidity under ambient air conditions at 3 m/s rate. It has been understood that keeping the drying speed and temperature high or low causes uncontrolled and insufficient drying. It has been observed that different drying conditions can be applied depending on hazelnut storage properties.