Accelerated Drying of Sun Flower Seeds

Abstract

A study was carried out to test and evaluate the effect of accelerated drying of sunflower seeds on seeds moisture content, fungal load on seeds surface and stabilization of the extracted oil using a conduction heating rotary dryer. The drying temperatures were set at approximately 75, 85, 95,105, 115, 125, 135 and 145 o C and the drying times were set at 3, 6, 9, 12 and 15 min. The results showed that all the drying process occurred at the falling rate period in which the rate of evaporation tends to fall as the moisture content decreases and the drying curve decays exponentially towards the final moisture content. Rapid moisture removal from seeds was obvious in all experiments particularly at higher heating surface temperature and longer exposure time. The results also showed that the simple equation was satisfactorily described the drying behavior of sunflower seeds and predicted the change in seeds moisture content as indicated by the higher coefficient of determination (R 2). Meanwhile, high temperature conduction heating reduced the fungal load in sunflower seeds in an effective manner. Also, the extracted sunflower oil was stabilized at certain combinations of heating surface temperature and exposure time as indicated from the lower values of free fatty acids of the these samples. It can be said that, the accelerated drying and heat stabilization of sunflower seeds using the conduction heating rotary dryer may be considered as an effective procedure for moisture reduction, fungal inactivation and oil stabilization. In general, heating surface temperature of 145 o C and the exposure time of 15 min are recommended to decrease the moisture content of sunflower seeds to the safe level of 5.8% (w.b), the fungal load to 102 colonies/g. and the percentages of free fatty acids to1.97 %.