Effects of Tea Polyphenols on Emulsification of Olive Oil in a Small Intestine Model System

Tea catechins have been shown to reduce plasma cholesterol and suppress hypertriacylglycerolemia by reducing triglyceride absorption. However, the mechanism is not yet clear. One of the possible mechanisms is that tea polyphenols may modify dietary fat emulsification in the gastrointestinal tract. The digestive enzyme (lipase) acts on specific emulsion interface properties (droplet size and surface area). Therefore, changes in these properties may modify emulsification and lead to changes in dietary fat digestion and absorption. In this study, the effect of both green and black tea on the changes of emulsification was examined by measuring the droplet size and the surface area. A model emulsion system containing olive oil, phosphatidylcholine (PC), and bile salt was developed to simulate small intestinal conditions. Initial changes in droplet size (from 1.4 to 52.8 μm and from 1.4 to 25.9 μm) of the emulsion were observed in the presence of 1.04 mg/mL and 0.10 mg/mL of total catechins prepared from green and black tea, respectively. Both teas caused similar changes on the emulsion properties; however, black tea was more effective than green tea. The underlying mechanisms of actions of tea polyphenols are discussed.

Keywords: Olive oil; emulsion; tea; droplet size; surface area; catechin; caffeine; small intestine