Correlations between gluten aggregation properties and content of quality-related protein fractions of wheat flour

The GlutoPeak Test (GPT) is a rapid small-scale (5 min, 8.5 g flour) technique to determine the gluten aggregation properties of wheat flour. To date, it is largely unknown how the results of the GPT are affected by the quantitative composition of gluten proteins. Therefore, the aim of this study was to establish correlations between the concentrations of quality-related protein fractions of wheat flour and its aggregation behavior. Contents of gliadins (GLIA), glutenins (GLUT), SDS-soluble proteins (SDSS), and glutenin macropolymer (GMP) of 19 winter wheat varieties (12-16% protein) were determined by two extraction/HPLC methods. The results were correlated to gluten aggregation kinetics determined by the GPT. Two groups of samples were distinguished based on the shape of their GPT curves. The curves generated by group A had a slower buildup in torque (measured as aggregation time) and a higher area under the curve at peak (maximum torque), compared to those generated by group B. The overall characterization of protein fractions showed that group A was characterized by lower GLIA (63-89 mg/g flour) and higher GLUT (38.8-47.4 mg/g) and GMP (19.6-30.7 mg/g) contents than group B (GLIA: 55-98 mg/g; GLU: 29.5-41.2 mg/g; GMP: 12.3-22.8 mg/g). GLIA and SDSS concentrations were significantly correlated to peak torque (GLIA: r=0.70, p≤0.001; SDSS: r=0.59, p≤0.01), probably because these fractions contained more than 60% of the crude protein, which is also related to peak (r=0.75, p≤0.001). GLUT and GMP contents were correlated to the aggregation time (GLUT: r = 0.72, p≤0.001; GMP: r = 0.77, p≤0.001) and the area under the curve at peak (GLU: r=0.68, p≤0.01; GMP: r=0.78, p≤0.001), confirming the importance of GMP for gluten strength. The study has shown that the GPT is an alternative to the labor-intensive quantitation of quality related protein fraction of wheat flour.