Effect of sprouting temperature on selected properties of wheat flour and direct expanded extrudates

The effect of the sprouting temperature on wheat sprouting and on the properties of expanded extrudates produced from sprouted wheat flour was studied. Therefore, wheat was sprouted at five different temperatures and subsequently dried, milled, and the resulting flour was used to produce extrudates using a twin-screw extruder. In order to understand the sprouting temperature effect, the degree of sprouting (DoS) of the differently sprouted samples and characteristic properties of flour and extrudates were studied and compared. During sprouting of wheat with increasing temperature and time an increase of the alpha-amylase activity, the vitamin C and reducing sugar content, and a decrease of the peak viscosity was observed. The greatest effect was found at 20 degrees C. Furthermore, the lowering of the viscosity of the flour suspension results in a reduction of the pressure and temperature in the extruder die. The extrudates of sprouted wheat flour were found to be easier to break, had a lower density, an increased longitudinal expansion index, and an improved cold-water solubility. A good correlation between the DoS and other properties of flour and extrudates was found, indicating a good predictive power and applicability of the DoS concept for wheat samples and their product development and specification. Practical Application The use of sprouted wheat flour for the production of extruded, direct expanded breakfast cereals is a promising opportunity to alter extrudate properties. Thereby, the sprouting temperature can be used as a means affecting the sprouted grain and extrudate properties intentionally and developing products being crunchier, and having an improved cold-water solubility, a lower density, and a changed expansion behavior. Moreover, due to an increased amount of reducing sugars in sprouted flour, which is a result of an intense starch degradation during sprouting, less additional sugar is needed to produce sweet breakfast extrudates.