Effects of wheat sprouting on starch, gluten, and dough properties

Grain sprouting leads to the development of specific enzymatic pattern (amylases, proteases, cellulases) that may improve both micronutrient bioavailability and sensory characteristics. On the other side, high accumulation in enzymes is usually associated with dough weakening and stickiness. The aim of this study was to evaluate the effects of wheat sprouting under controlled conditions on the technological performance of both wholegrain and refined flours. The sprouting process was conducted for 2-3 days at 20 °C and 90 % relative humidity, in an industrial plant (Molino Quaglia S.p.A., Vighizzolo d’Este, Padova, Italy). The effects of sprouting were assessed on gluten (i.e. visco-elasticity by the Glutograph®), aggregation kinetics by the Glutopeak®), starch (i.e. pasting properties by the MicroViscoAmylograph®) and dough (i.e. water absorption, dough development time and stability by the Farinograph®). In addition, amylase activity was evaluated by measuring a- and b-amylase content and by using the Falling Number. Whole grain and refined flours from unsprouted wheat were used as references. Despite the proteolytic activity developed during sprouting, the gluten proteins were still able to aggregate. However, the decrease in maximum torque, peak maximum time and energy required for gluten aggregation suggested gluten weakening. On the other hand, the sprouting process led to an increase in gluten stretching, suggesting an increase in dough extensibility. As regards starch, sprouting led to drastic decreases in viscosity during both the heating (i.e. peak viscosity and breakdown) and cooling (i.e. final viscosity and setback) phases, due to the increase in amylase activity. Adding silver nitrate – a strong a-amylases inhibitor – peak and final viscosity greatly increased, indicating that the pasting and gelation properties of starch were not significantly affected by sprouting. Dough made with sprouted wheat showed decreasing water absorption, stability and development time compared to the unsprouted control flours, as a consequence of the protease activity developed during sprouting. Further works are ongoing to evaluate the effects of using sprouted wheat on bread characteristics.