Controlled Sprouting of Durum Wheat: Effects on Starch and Protein Characteristics

Grain sprouting leads to the development of specific enzymatic pattern 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. Thus, a controlled wheat sprouting process could be useful to assess the perfect balance between nutritional advantages and technological performance. The aim of this study was to evaluate the effects of durum wheat sprouting under controlled conditions on both starch and protein characteristics. Durum wheat kernels were sprouted at 20 °C and 90 % relative humidity, and sampled after 24, 36, 48, and 62 hours. After sprouting, samples were dried and milled into semolina flour. The effects of sprouting time were assessed on gluten aggregation kinetics by the Glutopeak® and starch pasting properties by the Rapid Visco Analyzer®. In addition, amylase activity was evaluated by using the Falling Number. Despite the proteolytic activity developed during sprouting, the gluten proteins were still able to aggregate. However, the decrease in maximum torque and energy required for gluten aggregation suggested gluten weakening. Moreover, after sprouting proteins required more time for aggregation (i.e. high peak maximum time). No significant differences were detected between 36 and 48 hours, whereas the worst aggregation properties were measured after 62 h of sprouting. 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 (i.e. decrease in Falling number). Adding silver nitrate – a strong amylase inhibitor – peak and final viscosity greatly increased, indicating that the pasting and gelation properties of starch were not compromised by sprouting. Further works are ongoing to evaluate the effects of using sprouted durum wheat on bread characteristics.