Effect of drying methods on the physico-chemical properties of soyflour

Abstract

This study investigated the relationship between the drying methods and the physicochemical properties of soybean during drying prior to converting it into flour. Three samples were prepared for each of Tax 1485 and mixed varieties. A sample for each variety was subjected to a drying method. The three drying methods used are roasting, oven and sun drying. The dried samples were converted to flour in attrition mill. Supplemented breads (5% soy + 95% wheat) were prepared from the flour for organoleptic evaluation; proximate analysis was also carried on the flour samples. The analyses were replicated thrice. The result of this study showed that oven drying method has highest acceptability levels when compared to the other two methods in both Tax 1485 and mixed variety; showing 58 and 64%, respectively. It was also established that oven drying method retained highest protein content of 40.54 and 33.7% for Tax 1485 and mixed variety, respectively, though there was no significant difference in the protein values. The results show that drying for a long period (as observed in sun drying) and with high temperature (as observed in roasting), to achieve safe moisture content, will defeat the purpose of using soy flour as supplement due to a significant reduction in the protein content and acceptability. Moderately high temperature of 60°C in oven as being investigated is therefore recommended.

Key words: Roasting, boiling, oven drying, sun drying, quality.