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Document Type

Open Access Dissertation

Degree Name

Doctor of Philosophy (PhD)

Degree Program

Food Science

Year Degree Awarded

2017

Month Degree Awarded

May

First Advisor

David Julian McClements

Second Advisor

Eric Andrew Decker

Subject Categories

Food Science

Abstract

There is increasing consumer demand for food products that are more natural, sustainable, and environmentally friendly. Industry has responded by trying to identify natural alternatives to synthetic functional ingredients within these products. In this study, the ability of Maillard conjugation products, and several legume proteins were investigated to act as nature-derived or natural emulsifiers in oil-in-water emulsions fortified with hydrophobic nutraceuticals.

Casein-coated oil droplets enriched with lutein were highly unstable to flocculation near their isoelectric point due to the reduction in electrostatic repulsion. However, casein-dextran-coated droplets were stable, which was attributed to strong steric repulsion by the dextran moiety. The casein-coated droplets were unstable to aggregation in the gastric phase of a simulated gastrointestinal tract (GIT), whereas the casein-dextran-coated ones were still stable, which was again attributed to increased steric repulsion. Emulsifier type did not strongly influence lutein bioaccessibility.

Pea, lentil, and faba bean protein concentrates all proved to be effective emulsifiers for forming and stabilizing 10 wt% oil-in-water emulsions produced by high-pressure homogenization. The droplet size decreased with increasing emulsifier concentration, and relatively small oil droplets (d < 0.3 mm) could be formed. Lentil protein-coated droplets were the most stable to environmental stresses such as pH, ionic strength and temperature changes. Our results showed that there were no significant differences in the free fatty acid release in the small intestine phase among these systems and a whey protein-stabilized emulsion, with the emulsified lipids being rapidly and fully digested in all cases. Overall the emulsions formed using whey protein, that had smaller particle sizes than the others, were slightly more stable to lipid oxidation during the period of storage. Blocking the free sulfhydryl groups of proteins did not affect their ability to inhibit lipid oxidation in emulsion systems.

These results have important implications for the production of functional foods and beverages from natural plant-based ingredients and Maillard conjugates that can improve the stability of emulsions without adversely affecting the bioaccessibility of the bioactive agent.

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