Effects of transglutaminase (TG) on de Gluten Macro-polymer (GMP) and the characteristics of wheat dough

STEFFOLANI, ME; RIBOTTA, PD; PEREZ, GT; LEÓN, AE

Nantes, Francia

Congreso; 13th World Congress of Food Science & Technology; 2006

The aim of this study was to get a further insight into the effects of transglutaminase on glutenin macro polymer (GMP) fraction and their relation to wheat dough properties. Protein content of GMP dough decreased and volume surface average particle diameters (D3.2) of GMP dispersion increased with TG dose. SDS-PAGE patterns from GMP dispersion with TG showed a dark zone at the top of stacking gel and lower number of bands in agreement to the protein content. These results indicated that large molecules formed when treated with TG coincident with D3.2 increase. The resistance to deformation and energy needed for deformation until rupture increased as the level of TG increased. Gas retention capacity decreased when TG was added. Bread volume decreased with the addition of TG at the levels of 0.1 and 0.5 %. TG not only changed the size of protein molecules, also seemed to modify their solubility in SDS. The increase of the particle size of glutenin macro-polymer provoked by TG could improve the protein interactions between aggregates; which in turn could explain the considerable dough reinforcement found. The enzyme transglutaminase (TG; protein-glutamine: amine γ-glutamyltransferase) catalyzes an acyl- transfer reaction between γ-carboxiamide group of peptide-bound glutamine residues (acyl donor) and primary amines (acyl acceptor) including the -amino group of lysine residues in certain proteins (Motoki and Seguro 1998). Intermolecular cross-links introduced by TG change the protein structure and can improve the functional properties of proteins. Rheological properties of wheat dough and bread volume are improved by adding TG during mixing process (Basman et al 2002). Gluten is the main functional component of the wheat and is the responsible of dough viscoelasticity, it is composed of gliadins and glutenins. A glutenin fraction can be isolated from flour and dough as a gel known as glutenin macropolymer, GMP (Graveland et al 1982) which is insoluble en SDS. GMP has been related to quality parameters such as loaf volume and physical dough properties. The aim of this study was to get a further insight into the effects of transglutaminase on glutenin macro polymer (GMP) fraction and their relation to wheat dough properties. Transglutaminase Activa WM (100 TG U/g) from Ajinomoto was added to the base flour at the levels of 0.01, 0.1 and 0.5 %. Each dough sample was mixed and separated in two lots: i) immediately freeze-dried (not rested, NR), ii) was rested for 1 h (1hR) and freeze-dried. GMP was obtained as described by Skerrit et al. (1999). Protein content and particle size distribution by light scattering of GMP dispersions were determined. Protein aggregates from GMP were analyzed by SDS-PAGE. Dough was characterized by biaxial extension parameters as measured by texturometer (TAXT2i Texture Analyzer), gas retention capacity and breadmaking test. Protein content of GMP from NR and 1hR dough decreased drastically and significantly when TG was added at 0.1 and 0.5 % although lower dose increased the GMP content after resting (Table 1). Volume surface average particle diameters (D3.2) of GMP dispersion from TG-dough were larger than control dough. SDS-PAGE patterns from GMP dispersion with TG showed additional dark zones at the top of stacking gel. Also a significant reduction of band areas was found in samples treated with the higher level of TG in agreement to the protein content. These results indicated that large molecules formed when doughs were prepared with TG coincident with D3.2 increase. Biaxial extension tests showed that the resistance to deformation and energy needed for deformation until rupture increased as the level of TG increased. Control dough had the lowest values, indicating that TG strengthened dough, but extensibility did not change with TG addition (Table 1). TG added at the levels of 0.1 and 0.5 % decreased gas retention capacity. Dough surfaces did not presented small pores, as it was expected in a weaken dough; consequently it is probably that the resistance to deformation was high enough to prevent fully development of the dough during fermentation. Bread volume decreased significantly with the addition of TG at the levels of 0.1 and 0.5 %. More protein was extracted by SDS which was not able to form GMP, but the average particle diameters of GMP dispersion were larger, showing that TG not only changed the size of protein molecules, also seemed to modify their solubility in SDS. The increase of the particle size of glutenin macro-polymer provoked by TG could improve the protein interactions between aggregates; which in turn could explain the considerable dough reinforcement found. Table 1: Effect of TG doses on protein content of GMP and biaxial parameters of dough Acknowledgments The authors would like to thank both the Agencia Nacional de Promoción Científica y Tecnológica (ANPCyT) and the Agencia Córdoba Ciencia SE (ACC-SE) for financial support. References Basman et al 2002 Graveland et al 1982 Motoki and Seguro 1998 Skerrit J, Hac L, Bekes F (1999) Cereal Chem 76:395-401