ABSTRACT Protein-protein interactions in wheat dough as affected by mixing conditions (temperature and time) and kernel hardness and their impact on dough rheology were investigated. The effect of mixing temperature was different at the molecular level between hard and soft wheat flours. Regardless of the type of flour, non-covalent interactions appeared to drive protein network at low temperatures (4°C and 15°C), while covalent interactions were important at standard mixing (30°C). Protein features of hard wheat did not change as mixing temperature decreased, except an increase in SDS-accessible thiols. Whereas, decreasing mixing temperature from 30 to 4°C significantly affected protein interactions in soft wheat, evident in the high levels of SDS-soluble proteins and β-turn structures. Of flours from grains of different kernel hardness (Branson<Emmit<TW301020<Glenn), soft wheat (Branson and Emmit) showed lower water absorption, development time, and stability than hard wheat (TW301020 and Glenn). Despite kernel texture similarities, Branson and Glenn showed an overall stronger gluten network than Emmit and TW301020, respectively, as evidenced in gluten kinetics. On the other hand, Emmit and TW301020 tolerated mixing beyond dough development time better than Branson and Glenn in regard of protein features. Protein structural characteristics showed Branson and TW301020 doughs had more compact and ordered protein than Emmit and Glenn doughs. Further investigation of the role of kernel hardness in dough rheology and protein interactions was undertaken in durum wheat (Svevo cv), soft wheat (Alpowa cv), Soft Svevo (PIN expression) and Hard Alpowa (5DS distal end deletion). Presence of PINs affected flour particle size and damaged starch content, decreasing water absorption, dough development time, stability and the overall gluten strength. PINs affected dough extensibility only in common wheat where 5DS distal end deletion increased resistance to extension. As regards starch, PINs increased the pasting temperature and breakdown viscosity. PINs in flour favored protein-protein interactions, resulting in a compact network demonstrated by decrease in protein solubility and thiols accessibility. In dough samples, the effect of PINs on protein features were strongly dependent on the species. In particular, PINs promoted hydrophobic interactions in T. turgidum ssp. durum, and hydrogen bond related interactions in T. aestivum.
University of Minnesota Ph.D. dissertation. June 2016. Major: Food Science. Advisor: Alessandra Marti. 1 computer file (PDF); xi, 166 pages.
Structural modification of gluten proteins in wheat dough: the role of mixing conditions and kernel texture.
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