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Author ORCID Identifier

https://orcid.org/0000-0003-1846-8480

Document Type

Open Access Dissertation

Degree Name

Doctor of Philosophy (PhD)

Degree Program

Food Science

Year Degree Awarded

2020

Month Degree Awarded

May

First Advisor

David Julian McClements

Subject Categories

Food Chemistry | Food Science

Abstract

Curcumin is a polyphenolic compound found in Turmeric (Curcuma longa) rhizome that has excellent biological benefits such as antioxidant, anti-inflammatory, and anti-cancer properties to name a few. However, its incorporation in food and pharmaceuticals is difficult due to low water solubility and chemical instability. This study focuses on developing colloidal delivery systems for efficient encapsulation and increased protection of curcumin for maximizing the proposed health benefits of curcumin.

It was found that the physical and chemical stability of pure curcumin is impacted by pH, storage temperature, and molecular environment both in aqueous solutions and in oil-in-water emulsions. Pure curcumin was highly unstable to chemical degradation in neutral and alkaline aqueous solutions (pH ≥ 7.0) and it was most stable in acidic oil-in-water emulsions. Curcumin stability in emulsions depended on the emulsifier type, and the extent of curcumin degradation decreased in the following order: saponins > > gum arabic ≈ caseinate ≈ Tween 80. These results suggest that saponin accelerated curcumin degradation, which may be due to their ability to promote peroxidation reactions or it may be due to the presence of impurities in them, e.g. metals. The kinetics of curcumin degradation was significantly impacted by the mean droplet diameters (d32). The more rapid chemical degradation of the curcumin in the smaller droplets can be attributed to the fact that curcumin exchange between the interior and exterior of the droplets occurs more rapidly as the droplet dimensions decrease. Antioxidants were incorporated to protect curcumin in an emulsion having small droplets. The water-soluble antioxidants were more effective at protecting curcumin from degradation than the oil-soluble ones, which may have been because curcumin degrades faster in water than in oil, while the oil-soluble antioxidant actually slightly promoted curcumin degradation. Finally, the formation of nanostructured lipid carriers (NLCs) was optimized which, unlike O/W emulsion, consists of a solidified fat phase. NLCs were formulated using a hot-homogenization approach using fully hydrogenated soybean oil as the lipid phase and quillaja saponins as a natural surfactant. Characterization and stability studies revealed that NLCs have the potential to replace oil-in-water emulsions in commercial foods. Future studies are needed to establish their functional performance for curcumin encapsulation and protection. In summary, this study showed that the stability of curcumin in emulsions depends on various physicochemical parameters. This knowledge is important in designing and fabrication of colloidal systems for curcumin delivery.

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