Abstract: Objective: To investigate the processing of puffed cereal grains with added Cordyceps militaris by twin-screw extrusion and to explore the effects of addition of C. militaris on the starch pasting characteristics of extruded products. Methods: The flours of five cereal grains, rice, glutinous rice, adlay, red mung bean, and soybean were mixed after adding C. militaris powder and then extruded. Using the one-factor-at-a-time method, moisture content, screw rotation speed, feeding rate and extrusion temperature were selected as independent variables for the optimization experiments which were conducted following an orthogonal array design. The responses were radial expansion rate, degree of gelatinization, moisture content, water-absorbing capacity and solubility index. Optimization of the independent variables was done using range analysis. The starch pasting characteristics of the extruded product were assessed. Results: The optimal processing parameters were determined as follows: material moisture, 16%; screw rotation speed, 180 r/min; extrusion temperature, 80-90-120-140-165 ℃; and feeding rate, 15 r/min. Under these conditions, the radial expansion rate, degree of gelatinization, moisture content, water-absorbing capacity and solubility index were 3.015, 84.32%, 6.11%, 26.65%, and 416.39%, respectively. The rapid visco analyzer (RVA) results revealed that peak viscosity, hold viscosity, final viscosity and setback were reduced significantly in the extruded product after adding C. militaris, while peak time was increased significantly. Conclusions: The extrusion technology was feasible. Moreover, addition of C. militaris could significantly decrease starch pasting characteristics and inhibit starch retrogradation and molecular rearrangement in extruded cereal grains.

Key words: Cordyceps militaris, cereal grains, extrusion, retrogradation