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Swelling Index of Glutenin Test for Prediction of Durum Wheat Quality¹

¹Agriculture and Agri-Food Canada, Cereal Research Centre, 195 Dafoe Road, Winnipeg, MB, Canada R3T 2M9. Contribution No. 1795. ²Agriculture and Agri-Food Canada, Cereal Research Centre, 195 Dafoe Road, Winnipeg, MB, Canada R3T 2M9. ³Corresponding author. E-mail: mkovacs@em.agr.ca Phone: 204/983-1385. Fax: 204/983-4604.

The swelling index of glutenin (SIG) was assessed for suitability as a screening procedure for durum wheat gluten strength. Five sets of samples with a wide range of gluten strength values were collected according to gluten strength parameters and characterized for SIG. Statistical analysis revealed that the SIG and SDS sedimentation tests were both able to satisfactorily account for variations in gluten strength in all sets of samples. However, for most samples, the SIG test was more reliable than the SDS sedimentation test for predicting gluten strength. Furthermore, the SIG test can differentiate samples with glutenin swelling properties that could not be accounted for by intercultivar variation of SDS sedimentation volumes. The percentage of insoluble glutenin in protein is usually a better predictor for gluten strength than the percentage of insoluble glutenin in flour. Similarly, when the SIG values were divided by the protein content of the samples, the resulting proportions were better predictors of gluten strength than the absolute values. Analysis of protein fractions revealed that the insoluble glutenin was the protein fraction most responsible for the SIG value and gluten strength. Extensibility of dough was significantly related to the soluble glutenin content, while the alveograph G index was related to monomeric protein content. The results suggest that screening based on the SIG test would be valuable for comparing durum wheat lines and cultivars for gluten strength and pasta-making quality.