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theses

Encapsulation and controlled-release of active food ingredients, such as oil-soluble flavors, preservatives, vitamins, and nutraceuticals, are important applications in food and nutrition that can be attained with nanotechnologies. Functional foods refer to foods that have a potentially positive effect on health beyond basic nutrition; such as regulating blood glucose and cholesterol level, preventing inflammation and cancer, and cardiovascular protection. Capsaicin (CAP, trans-8-methyl-N-vanillyl-6-nonenamide) and quercetin (QC, 3,3′,4′,5,7-pentahydroxyflavone) are food-grade nutraceuticals with many health-related beneficial functions, including anti-cancer, anti-inflammation, anti-oxidation, cardioprotection and anti-obesity activities. However, as hydrophobic compounds, their low water solubility greatly limits the in-vivo bioavailability. To overcome these problems, novel processing methods and emulsion-based delivery systems were used in my research to enhance the bioavailability of nutraceuticals. In the first part of this work, the wet-milling technologies were used to increase the quercetin (QC) dissolution and bioaccessibility by reducing the particle sizes to around 340 nm with a saturation solubility of 28.78 ± 0.31 μg/mL, about eleven times higher than coarse quercetin. The addition of hydrophobically modified starch could help reduce the particle size by working as a stabilizer to prevent the agglomeration of QC nanosuspensions after wet milling. An in-vitro digestion model-TNO model, which was used to mimic the digestion process in the upper GI tract, had determined an increased bioaccessibility of quercetin for the formulated nanoparticles. In the second part of this study, a lipid-based nanoemulsion system was developed towards the encapsulation of capsaicin (CAP) in order to increase CAP stability, dissolution, bioaccessibility, and reduce the gastric mucosa irritations caused by free unformulated CAP crystals. Oil samples (medium-chain triacylglycerol (MCT), corn oil and canola oil) were used to dissolve the CAP and evaluated by in-vitro lipid digestion test. Lipolysis results showed that MCT system had both the highest bioaccessibility of CAP and the largest extent of lipolysis. Sucrose stearate S-370 was chosen as the gelator to form the CAP-loaded organogel. After the addition of Tween 80 as the emulsifier and processing of ultrasonication, the organogel-derived nanoemulsion was formed with CAP’s loading of 80 mg/ml and emulsion droplet sizes of 168 nm. Animal studies using male rats showed that the acute gastric mucosa irritation caused by CAP was alleviated effectively. Moreover, the CAP-loaded nanoemulsion (C-NE) was further proved to have an enhanced anti-obesity effect compared with free unformulated CAP water suspensions. . C-NE demonstrated an enhanced effect in controlling the HFD-induced weight gain compared to free unformulated CAP water suspensions. MCT, which was contained in the wall material of C-NE, might work synergistically with CAP as a weight-loss agent due to its ability to increase fat oxidation and energy expenditure. Serum biochemical evaluations showed that C-NE had an anti-hyperlipidemic potential with low toxicity for rats. Histological sections of liver and adipose tissues proved the inhibitory activity of C-NE on HFD-induced hepatic steatosis and HFD-induced adipocytes hypertrophy, which was effective in a dose-dependent manner. Gastric mucosa irritation test showed that chronic applications of C-NE alleviated the inflammations in rat stomach tissues caused by CAP.

ETD_8253

Ph.D.

Includes bibliographical references

by Muwen Lu

doi:10.7282/T32B925N

ETD doctoral

The author owns the copyright to this work.