Abstract: In this study, 19 gluten protein traits of 44 wheat varieties were analyzed. Principal component analysis (PCA), correlation analysis (CA), membership function (MF) and stepwise regression (SR) were used for comprehensive evaluation of wheat gluten protein. The results showed that the variations of disulfide bond content ranged from 3.28 to 6.78 μmol/g, and the variations of sulfhydryl group content ranged from 13.30 to 16.66 μmol/g. The variation range of gluten protein traits was 4.74% to 89.46%, with larger variation coefficients being observed for stabilization time and farinograph quality index, indicating huge variation potential for protein quality traits. Three comprehensive factors were converted from the 19 protein traits by PCA, with contribution rates of 40.80%, 19.86% and 15.88%, respectively, and a cumulative contribution rate of 76.54%. PCA classified gluten proteins into three categories including gluten quality traits, aggregation traits and quantitative traits. The comprehensive evaluation value (D-value) of gluten was calculated using the MF method, and the average of the 12 traits with higher PCA loadings were found to be significantly correlated with D-values. Regression equations with seven traits including disulfide bond content, glutenin macropolymer (GMP) content, protein content, dry gluten content, gluten index, tensile area and peak maximum time (PMT) as independent variables were established using SR. There was a good linear relationship between bread quality indexes and D-value, with determination coefficient (R2) between 0.561 4 and 0.771 3, which verified the accuracy and feasibility of D-value. It could be concluded that wheat gluten protein with different gluten strengths exhibited abundant variation potential. It is feasible to comprehensively evaluate gluten protein quality by multivariate statistical analysis. The quantity and quality of gluten protein as well as the content of disulfide bonds in the gluten network could be used as key indexes for the evaluation and improvement of wheat quality.

Key words: wheat; disulfide bond content; gluten protein; principal component analysis; comprehensive evaluation