Effect of heat treatment on wheat protein changes and dough rheological properties
L. VÁZQUEZ CHÁVEZ1, I. Guerrero Legarreta1, M. Vizcarra Mendoza2, A. Salazar Zazueta3, and A. Castillo Morales4. (1) Departamento de Biotecnologia, Universidad Autonoma Metropolitana-Iztapalapa, Ap. Postal 55-535, Mexico City, 09340, Mexico, (2) Departamento de Ingeniería de Procesos e Hidráulica, Universidad Autónoma Metropolitana-Iztapalapa, Av. Michoacán y Purísima s/n, Mexico City, 09340, Mexico, (3) INIFAP, Chapingo, Edo. de Mexico, Chapingo, 56230, Mexico, (4) Departamento de Matemáticas, Universidad Autonoma Metropolitana-Iztapalapa, Av. Michoacán y Purísima s/n, Mexico City, 09340, Mexico
Wheat gluten is the main flour component responsible of bread quality. Initial heat treatment is usually applied to the wheat grain in order to decrease humidity and increase its storage life. However, if no adequate conditions are applied during heat treatment, wheat proteins are thoroughly altered therefore affecting the wheat industrial quality. The objective of these work was to study the effect of heat treatment during initial drying on protein solubility and electrophoretical patters of wheat gluten proteins, and on rheological properties of the dough.
Triticum aestivum samples were dried at 40, 60 and 80oC during 30 to 360 min. The response variables were: protein solubility loss in saline solutions as measured by the Bradford colorimetric test at 590nm. Dough rheological properties were evaluated using a Brabender farinograph. Bread making tests were carried out by the direct method reported by the AACC. SDS-PAGE electrophoresis was carried out using a Mini Protean II system (Bio Rad) in a discontinuous system. Proteins were extracted using SDS with and without mercaptoethanol. The gels were scanned using a Gel Doc equipment.
Results showed a direct relationship between solubility loss, and dough extensibility and strength. Loaf volume was also decreased when high temperatures were used during drying. Electrophoretic patterns showed degradation in bands corresponding to glutenin. Glutenin and gliadin degradation due to denaturation and further crosslinking via disulphur bonds resulted in a strong gel which did not developed into a suitable loaf during the breadmaking process, especially when mixed. Glutenin showed more intense modifications involving changes in disulphur bridges, forming aggregates. The net effect was an increase in the glutenin molecular weight
The studies on the effects of drying in protein configuration helps to define the most suitable conditions for heat treatment without altering wheat quality.
Session 44B, Food Engineering: Rheology and Texture