Investigating the Effect of Roasting Time on Some Physicochemical, Technological, Flowability, Antioxidant and Sensory Properties of Roasted Soybean Flours as Cocoa Substitute

Abstract

Considering the importance of finding suitable substitute for cocoa powder, the effect of roasting process on physicochemical characteristics (pH, aw, WHC, OHC and colour parameters), compositional properties, some physical and thermal features (particle size, bulk & tapped densities, porosity, Hausner ratio, Carr index, repose angle and DSC); antioxidant characteristics and sensory properties of roasted soybean were investigated. The soybean samples roasted at 165 ○C for 4, 6, 8, 10 and 12 min, then milled and sieved (No.40). Nutritional elements, Mg, Na, Ca, Zn, Cu and Fe increased during roasting. Repose angle, aw and moisture content decreased by increasing roasting time. Hausner ratio and Carr index of raw soybean flour were 33.3 and 1.51 respectively, they decreased to 28.73 and 1.40 after roasting for 12min. Study showed that raw soybean flour had a weak flowability. L* as a time-temperature index at roasting process of foods (like coffee and cocoa) decreased by increasing time. Antioxidant activity results suggested that antiradical activity and total phenol content of roasted soybean flours increased by roasting time and a significant correlation between these two items were observed (P<0.05). DSC analysis showed that flours had a high thermal resistance. Sensory properties evaluation showed that soybean flour roasted for 8 min, had a comparable total acceptance to cocoa powder.

Keywords

• cocoa substitute
• physical properties
• roasting
• sensory properties
• soy flour