The use of HPLC for quality prediction of South African wheat cultivars

English: The primary aim of this study was to determine whether size-exclusion high performance liquid chromatography (SE-HPLC) could be used for quality prediction of South African wheat cultivars. · A bread cultivar, a cracker cultivar and two soft wheat cultivars were used in this two-year experiment. · Protein extracts of wheat flour were analysed by SE-HPLC. · SDS was used for the first protein extraction step, and the rest of the proteins were extracted by sonication. · The SE-HPLC method fractionated the storage proteins (both SDS-soluble and SDS-insoluble) into four distinct peaks of decreasing molecular size range, representing mainly larger polymeric proteins (mainly HMW-glutenins), smaller polymeric proteins (mainly LMW-glutenins), larger monomeric proteins (mainly gliadins), and smaller monomeric proteins (mainly albumins and globulins). · The wheat samples were also analysed for a total of 11 important quality characteristics. · Relationships between the amount and size-distribution of polymeric and monomeric proteins and flour quality properties were established. · The influence of different nitrogen (N) treatments on protein fractions and quality characteristics was also determined by SE-HPLC.The results showed that both the genotype and N-treatments had a significant influence on quality characteristics. · However, the genotype (cultivar effect) had a more significant influence on the protein fractions and quality characteristics than the N-treatments. · The total amounts of N applied during the treatments had a more significant eff ect on protein fractions and quality characteristics than later N-applications (N applied during the flag leave stage). · The SDS-soluble and SDS-insoluble polymeric proteins were found to be equally important in quality prediction. · The hard wheat cultivars were characterised by an increase of polymeric protein as opposed to monomeric protein. · The polymeric proteins (glutenins) were strongly positively correlated with dough strength properties, such as alveograph P/L ratio and alveograph strength. · The large monomeric proteins, which are mainly gliadins, were positively associated with the soft wheat cultivars, and had a consistently significant negative effect on quality characteristics, such as falling number (FLN), vitreous kernels (VK), alveograph P/L ratio and alveograph strength. · The large monomeric proteins showed positive correlations with single kernel weight (SK weight), single kernel diameter (SK diameter) and breakflour yield (BFLY). · SE-HPLC provided a simple and an objective test for measuring the relative size-distributions of wheat storage proteins. · SE-HPLC also proved to be very usefull in predicting quality.