Influence of Physical States (Crystalized Versus Solubilized) of Bioactive Components And Oil Composition on Bioaccessibility And Bioavailability

DEDICATION I would like to dedicate this work to my lovely and supportive parents. I am very appreciative of their love and support. Without their guidance, I would not be able to achieve this. iv ACKNOWLEDGMENTS I would like to acknowledge all of those associated with the Food Science Department at the University of Massachusetts Amherst. I would like to give my special thanks to Dr. Xiao and Dr. McClements for the instructions and knowledge they gave to me. β-carotene, a precursor to Vitamin A, is considered as a potent nutraceutical in foods and beverages due to its ability of reducing the incidences of certain chronic diseases. However, because of its lipophilicity, its use is certainly limited. In this study, we investigated the bioaccessibilities of solubilized β-carotene and β-carotene crystals through a simulated gastrointestinal digestion model. Three systems were compared in the first case study: (1). pre-dissolved β-carotene nanoemulsion (d< 200nm); (2). corn oil emulsion (d< 200nm) with β-carotene crystals being added before digestion; (3). phosphate buffer saline with β-carotene being added before digestion. Oil-in-water nanoemulsions were formed by high-pressure homogenization using Tween 20 as emulsifier and corn oil as carrier oil and then they were subjected to a simulated mouth, stomach and small intestine digestion. The rate and extent of free fatty acid production in small intestine decreased in the order (2)>(1)>(3); whereas the β-carotene bioaccessibility decreased in the order (1)>>(2)>(3). In system (3), even without any fat content, there is still noticeable consumption of NaOH, which is due to vi the ester bonds existing in the non-ionic surfactant (Tween 20). In the second case study, we developed two comparing groups by differentiating their oil concentration (20%, 4% respectively). The bioaccessibility of the high fat group is only half of the low fat group due to the insufficient digestion of fat in the former group. In the third case study, the bioaccessibility of nobiletin with different physical states (crystalized vs solubilized) and in different delivery system (conventional emulsion vs nanoemulsion) was compared. Not like β-carotene, the bioaccessibility of nobiletin as crystals in slightly lower than it is as solubilized state. Meanwhile, in conventional emulsion, the bioaccessibility is slightly lower than in nanoemulsion. This study provides important information for developing effective delivery systems for lipophilic bioactive components in food and beverage applications.