Gluten free flour doughs improvement of texture by protein cross-links occurring via microbial transglutaminase from Streptoverticillum mobaraense.

Gluten is the major factor involved in the structural properties of bakery products. Thanks to its ability to create aggregates, it gives dough viscosity, elasticity and cohesion, all features responsible for the baking performance. Gluten is composed of extensible, viscous gliadins and rigid, elastic glutenins. Moreover, the gliadin protein fraction is the main factor responsible for the development of celiac disease (CD) and other non-celiac gluten sensitivities. The only treatment for these people is lifelong adherence to a strict gluten-free diet. Nowadays, the development of new technologies in the food industry aims to both improve products already marketed, and to develop new gluten-free products. Cross-linking enzymes, able to organize and create protein networks, are suitable for the food industry as protein modifiers. Among those enzymes, Transglutaminase (TGase) due to its ability to improve the firmness, viscosity, elasticity and water-binding capacity of food products could be the key factor for manipulation in order to achieve higher food quality. The aim of this study was to evaluate the effects of addition of microbial transglutaminase from Streptoverticillium mobaraense, on protein aggregation in gluten free flours as well as in baked products. In our research we assessed five gluten free flours deriving from different plant sources such as cereals, pseudo-cereals and legumes, in particular corn, rice, amaranth, quinoa and lentil flours have been analyzed. By biochemical tests, flours’ total extracted proteins capacity to act as TGase substrate was evaluated. Since all tested flours showed considerable transamidase activity in microplate colorimetric assay, the possible formation of crosslinked products were analyzed by SDS-PAGE. For this purpose, micro-doughs prepared by adding the water, in 1:2 ratio (w/v), to different flours were treated with different amount of TGase enzyme (0.5; 0.75; 1; 2 Units). To clarify which protein fraction of the flours was the best substrate for the TGase, differential extractions were performed. Therefore, three sequential fractions, corresponding to albumins/globulins, prolamins and glutelins, were analyzed in relation to different enzyme amounts. Results showed that the microbial TGase has capacity to modify gluten free flour proteins and determine protein network formation. In particular, lowest enzyme concentration (0.5 U) was able to cause differences in protein bands between treated samples and their non-treated controls. These preliminary results give a perspective in the gluten-free research and suggest their possible use to create innovative products with improved texture.