Manipulation of zein structure with co-protein addition for application in dough systems
Abstract
Gluten, wheat storage protein, exhibits unique ability of forming a viscoelastic dough upon hydration and mixing. It is composed of alcohol soluble proteins, gliadins, and polymeric glutenins. The interactions between gluten proteins, gliadins and glutenins, are responsible for the formation of viscoelastic protein network. Gliadins are recognized as the protein fractions responsible for viscous nature of gluten and, glutenins for the elasticity. High molecular weight subunits of glutenin (HMW-GS) have been found particularly important in imposing elasticity to gluten structure. The mechanism involves the structural transitions between β-sheet and β-turns and is related to the long repeat regions of HMW-GS and their interactions. On the other hand, corn protein, zein, is relatively small protein and does not demonstrate viscoelastic properties at room temperature. However, α-zein was shown to form viscoelastic dough at moisture contents larger than 20% when hold and mixed at 35°C, which is above its glass transition temperature. Here, it is speculated that gliadin, which comprises significant portion of wheat gluten, is not only simply a filler imparting viscosity to wheat gluten, but also an important functional protein fraction that goes through structural transformation with addition of HMW-GS to the system. Therefore, it is hypothesized that, zein, which shows similarities to wheat gliadin in number of aspects, can attain viscoelastic properties at room temperature with addition of co-protein similar to that of HMW-GS in wheat gluten. Wheat and corn proteins were utilized in this study to investigate and compare their viscoelastic properties. Fundamental rheological techniques and Fourier Transform InfraRed (FT-IR) spectroscopic studies were performed to understand the structure-function relationship in these proteins. Improved viscoelastic properties were obtained for zein with addition of co-protein at room temperature. The transformation of gliadin with the addition of HMW-GS and glutenin was also shown. However, gliadin and zein were found to gain structural functionality through different mechanisms. In gliadin, structural transformation took place through transitions between β-sheet and β-turns. On the other hand, main transition in zein was found to be from α-helix to β-sheet.
Degree
Ph.D.
Advisors
Hamaker, Purdue University.
Subject Area
Food Science|Agricultural engineering
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