Transglutaminase polymerisation of buckwheat (Fagopyrum esculentum Moench) proteins

Recently, screening of transglutaminase (TGase) treatment on several gluten-free cereals revealed significant improvements on the baking performances of buckwheat flour by promoting protein networks. In this study, the impact of TGase on the protein fractions of buckwheat flour was investigated in order to better understand the activity and specificity of the enzyme. Albumin, globulin, prolamin and glutelin fractions were extracted from the flour and incubated with TGase. Capillary electrophoresis, two dimensional (2D) gel electrophoresis and size exclusion chromatography (SEC) were performed on each fraction. Capillary electrophoresis and 2D gel electrophoresis revealed that buckwheat main storage proteins, i.e. 2S albumin, 13S and 8S globulin, were cross-linked after TGase treatment. SEC showed the presence of high molecular weight (HMW) protein polymers in the TGase-treated albumin and globulin fraction. Analysis of the amino acid composition of the fractions revealed high amounts of glutamine and lysine residues in all fractions. In conclusion, the increase in the average molecular weight of buckwheat proteins and the formation of HMW protein polymers after TGase treatment are responsible for the improved functionality of buckwheat flour in terms of breadmaking potential. The enzyme was revealed to be not fraction specific as all fractions were TGase-reactive.