Modification of structure and mixing properties of wheat flour through high-pressure processing

Controlling the inter-season impact on the quality of wheat flour has been a challenge for wheat growers. High-pressure processing (HPP) can alter protein and starch structures, which in turn may be used to modify the structure and properties of the starch-gluten matrix in flour post milling. To test this hypothesis, HPP for 5 min at 0.1 to 600 MPa (room temperature) was applied on wheat flours (8% and 11% protein) conditioned to two moisture contents (33% and 56%, w/w, total flour base). Changes in the microstructure and mixing properties of the dough prepared from the HPP-treated flour were investigated, which was then related to the changes in the starch and the gluten protein. Partial or complete loss of starch crystalline structure in the 56% moisture flour was induced at 400 to 600 MPa whilst no changes were found in the 33% moisture flour. Aggregation of gluten protein occurred at 400 MPa or above for both moisture levels. At 500 and 600 MPa and 56% moisture, changes in starch granule structure in combination with protein aggregation have resulted in the formation of dough with broken protein network. However, protein aggregation after HPP at 33% moisture promoted formation of a fibril protein network in dough structure, leading to increased dough strength and prolonged development time and stability time during dough mixing. Therefore, modification of protein structure by HPP (e.g. at 500 or 600 MPa for 5 min) at sufficiently low moisture (e.g. 33%) while maintaining the starch granule integrity could enhance the mixing properties of low graded wheat flour in food applications.