Wheat sprouting: lights and shadows

Pre-harvest sprouting is associated with poor bread-making performance due to high accumulation of enzymatic activities that negatively affect dough rheology in terms of strenght and stickiness. Thus, using of sprouted grains in baking has been restricted until now. On the other hand, sprouting has been used for centuries to improve the nutritional and sensory properties of grains. This study addressed the effects of wheat sprouting under controlled conditions (2-3 days; 20 °C; 90 % relative humidity) on gluten (i.e. visco-elasticity; aggregation kinetics), starch (i.e. pasting properties) and dough (i.e. water absorption, dough development time and stability). In addition, enzymatic activities were evaluated. Secondly, the work addressed the possibility of using sprouted wheat flour at low (<2%) or high (>15%) levels to improve the bread-making performance of commercial flours. Controlled sprouting led to small changes in starch viscosity during heating and cooling, indicating that starch pasting and gelation properties were not dramatically affected by sprouting. As regards proteins, despite a certain degree of gluten weakening was observed, gluten proteins were still able to aggregate. Moreover, the sprouting process led to an increase in gluten stretching, suggesting an increase in dough extensibility. Dough made with sprouted wheat (SW) showed decreasing water absorption, stability and development time compared to the unsprouted control flours, as a consequence of the enzymatic activity developed during sprouting. Despite that, bread height, volume, and softness improved when SW was used. Enrichment with 1.5% SW improved the amount of gas production during leavening, resulting in bread with high specific volume and crumb softness even during storage. No significant changes in mixing properties and gluten aggregation kinetics were measured between 25-75% enrichment level. The best result – in terms of bread volume and crumb porosity – was obtained with 50% SW instead of using SW alone. Interestingly, SW positively affected starch digestibility.