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Plant proteins are increasingly focused upon as alternatives to animal-derived macromolecules for the encapsulation of bioactives. The rational design of encapsulation carriers should be based on a solid understanding of the interactions between the proteins and bioactives. Encapsulation technology for food applications has focused predominantly on the protection and controlled release of hydrophobic bioactives. For hydrophilic molecules, although not less important from a nutritional and health perspective, significantly fewer encapsulation systems have been explored, designed and described. As hydrophilic molecules tend to partition into the aqueous food matrix, it is even more crucial to understand and to be able to modulate the interactions between the hydrophilic bioactive and the encapsulating matrix material in food relevant conditions. Therefore, examining the nature of the interactions between anthocyanins (ACNs), a hydrophilic bioactive, and prolamin plant proteins (gliadin, hordein, secalin, and avenin) is timely. These interactions were examined using steady-state and time-resolved luminescence spectroscopy techniques. The ACN-induced quenching of the prolamins intrinsic fluorescence emission did not follow a linear Stern-Volmer relationship, but rather displayed an upward curvature for all the prolamins tested. Hence, both static and dynamic quenching likely occurred in the prolamin-ACN systems. The quenching mechanism was further explored based on the changes in fluorescence lifetime as ACN concentration increased. As the independent lifetimes of the prolamin-ACN combinations did not decrease discernibly as a function of ACN concentration, static quenching is presumably the predominant quenching mechanism. The thermodynamic parameters revealed that the interactions between secalin- and avenin-ACN are mainly driven by the hydrophobic effect, while those between gliadin- and hordein-ACN are dominated by ionic interactions. Zeta-potential measurements support the dominant ionic interactions found for gliadin and hordein. The insights gained in this research will serve as a sound basis for further studies focusing on matrix selection with regard to creating performant encapsulation systems for ACNs.

This thesis examines the structure and functionality of zein in bakery products. Particular emphasis was laid on the optimization and application of vibrational and luminescence spectroscopy techniques to study complex zein and gluten dough systems. In this context, the molecular and sub-molecular structure of zein-gluten dough systems was investigated by fluorescence, Fourier transform (FT)-Raman, and Fourier transform infrared (FTIR) spectroscopy as well as confocal Raman microscopy (CRM). Formation of β-sheet-rich fibrils in zein dough was derived from the FTIR and FT-Raman protein secondary structure analyses, and the extrinsic Thioflavin T fluorescent probe results. In addition, the Raman scatter data reported on the dominant β-sheet type and the ratio of fully solvent-exposed and buried tyrosine residues in the zein and gluten network structures. Small and large deformation rheological behavior of the zein-gluten dough samples revealed that in addition to differences in protein structural units, weaker starch-protein interactions also contribute to the lower elasticity of zein dough compared with gluten dough. However, zein-rich dough samples showed high extensibility and resistance to extension, which were attributed to the formation of highly structured (β-sheet rich) fibrils as observed using cryo-scanning electron microscopy (Cryo-SEM) and CRM. Based on the gathered insights, a model was proposed for zein structure in a viscoelastic dough system. The in-depth information on the zein dough structure led to the development of gluten-free breads made with zein. The effect of addition of different hydrocolloids (hydroxypropyl methylcellulose (HPMC), guar and xanthan gum) and the inclusion of pregelatinized starch on zein dough and bread properties was examined. Small amplitude oscillatory and creep-recovery tests showed a notable increase in the viscous nature of the zein dough by addition of HPMC, likely due to the lubricating effect of HPMC on the zein fibrils. SEM images also revealed a continuous (foam-like) fine network structure of zein strands in the zein dough made with HPMC, presumably responsible for the higher specific volume of the bread. Therefore, this research has advanced the understanding of zein structure and functionality in bakery systems and provides a sound basis for the development of zein-based gluten-free breads. Ontario Trillium Scholarship

Purple and blue coloured wheats contain significant amounts of anthocyanins. There is a linear relationship between the ash and anthocyanin content of milling fractions, confirming the localization of anthocyanins in the bran layers. Purple wheats contained predominantly cyanidin-3-glucoside, and pelargonidin-3-glucoside, and had an overall complex anthocyanin composition. Blue wheats were enriched in delphinidin-3-glucoside, and a had simpler composition than purple varieties. Sprouting was not a suitable treatment to increase anthocyanin extractability, since it significantly decreased the anthocyanin content. In processed wholemeal products (i.e., crackers and bread), mixing and baking steps significantly decreased anthocyanin content, while resting/fermentation did not. Dough systems with decreased pH were more protective of anthocyanins during intermediate processing steps, as were high-temperature, short-time baking procedures. Purple wheat anthocyanin composition was more affected by mixing, while blue wheat composition was thermally affected. Therefore, bread and cracker procedures can be designed to optimize anthocyanin retention in the final product.