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 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.