Relationship between kernel hardness and gluten proteins characteristics

This study aimed at investigating gluten structural characteristics in dough from wheat cultivars with various kernel hardness. Flours from Branson, Emmit, and TW301020 cvs. (7, 24, and 69 SKCS, respectively) were analyzed for mixing properties, gluten aggregation kinetics, protein aggregates formation, thiols accessibility and protein conformation. Farinograph profiles were related to the kernel texture, with soft wheats (Branson and Emmit) having lower water absorption, development time, and stability than hard wheat (TW301020). Unlike the farinograph profile, Branson and Emmit exhibited different gluten aggregation kinetics, with Branson having longer aggregation time and higher aggregation energy, suggesting a stronger gluten network than Emmit. Protein structural characteristics highlighted that proteins in dough from Branson and TW301020 were more compact (low SDS-accessible thiols, low exposure of hydrophobic sites on the protein surface) and ordered (low levels in random coils) than in dough from Emmit. In addition, high levels of ß-turns in Emmit dough may account for the fast gluten aggregation kinetics, compared to Branson. Interestingly, Branson resulted in bread with a higher specific volume than Emmit (3.6 and 2.9 ml/g, respectively), with TW301020 having the highest value (5.0 ml/g). In conclusion, wheat samples showing similar mixing profile may have different protein interactions during mixing which will affect product performance. Not all soft wheat would form a weak dough; the ability of flour to produce a dough characterized by a compact protein network is independent of the kernel texture but it is rather related to the nature of inter-protein interactions.