Date of Award

Fall 12-18-2020

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Doctor of Philosophy (PhD)

Department

Food Science and Human Nutrition

Advisor

Mary E. Camire

Second Committee Member

Robert C. Causey

Third Committee Member

Carl P. Tripp

Additional Committee Members

Mehdi Tajvidi

Denise I. Skonberg

Abstract

Lipid carriers such as emulsions and liposomes have been widely studied as carriers for different nutraceuticals. However, lipid carriers' physicochemical instability results in the leakage of loaded nutraceuticals and the low solubility into the digestion medium, thus reducing the bioaccessibility. Cellulose nanocrystals (CNC) are nano-sized cellulose derivatives obtained after hydrolysis of cellulosic matrices that possess potential applications in functional foods and nutraceuticals. However, hydrophilicity, anionic surface potential, and poor re-dispersibility limit CNC’s applications. The primary objectives of this research were 1) to modify CNC via adsorbing polyethylene glycol (PEG) to stabilize liposomes and to study its physiochemical stability at different in vitro gastrointestinal tract (GIT) conditions, pH levels (1-11), temperatures (4-100 oC) and illumination periods (4-72 hours); 2) to modify CNC via adsorbing lauric acid to stabilize O/W emulsion and to study its physicochemical stability at different pH (1-11), dilution factors (1-10 times), storage period (up to 30 days) and GIT conditions. Phycobiliprotein and beta-carotene were chosen as model nutraceuticals.

In study 1, particle size and microscopic analysis revealed a better physical/kinetic stability for the liposomes stabilized with PEG-adsorbed CNC than the liposomes stabilized with unmodified CNC, resulting in significantly (p≤0.05) smaller average particle size during the initial and mouth phases of the in vitro GIT study, nonetheless a significant (p≤0.05) increase in the particle size from ~300 nm to ~5500 nm at gastric phase due to lower pH. Moreover, stabilized liposomes retained the attributes of phycobiliprotein against pH, illumination, and a temperature of 60 ̊C. In study 2, lauric acid-adsorbed CNC affirmed the kinetic/physical stability of emulsions throughout the GIT phases. Results exhibited a maximum of 65% beta-carotene bioaccessibility for the emulsion stabilized with modified CNC, and 71% for the emulsion stabilized with unmodified CNC. Moreover, a higher amount of lipid oxidation was recorded for the emulsion with stabilized modified CNC than the emulsion stabilized with gum Arabic.

Although modified CNC retains the kinetic/physical stability of lipid carriers; however, it increases lipid carriers' chemical instability and decreases the loaded nutraceuticals' bioaccessibility. A strategic modification of CNC is needed to ensure the stability of lipid carriers and increased nutraceuticals bioaccessibility.

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