Macronutrient digestion and polyphenol bioaccessibility in oat milk tea products: an in vitro gastrointestinal tract study†

People are increasingly preparing milk tea using plant-based milks rather than cow's milk, e.g., vegans, those with lactose intolerance, and those with flavor preferences. However, adding plant-based milks to tea may impact the digestion, release, and bioaccessibility of nutrients and nutraceuticals in both the tea and milk. In this study, oat milk tea model systems (OMTMSs) containing different fat and tea polyphenol concentrations were used to explore the impact of tea on macronutrient digestion in oat milk, as well as the impact of oat milk matrix on the polyphenol bioaccessibility in the tea. An in vitro gastrointestinal model that mimics the mouth, stomach, and small intestine was used. Tea polyphenols (>0.25%) significantly reduced the glucose and free fatty acids released from oat milk after intestinal digestion. Tea polyphenols (>0.10%) also inhibited protein digestion in oat milk during gastric digestion but not during intestinal digestion. The bioaccessibility of the polyphenols in the tea depended on the fat content of oat milk, being higher for medium-fat (3.0%) and high-fat (5.8%) oat milk than low-fat (1.5%) oat milk. Liquid chromatography-tandem mass spectrometry (UPLC-ESI-MS/MS) analysis showed that lipids improved the tea polyphenol bioaccessibility by influencing the release of flavonoids and phenolic acids from the food matrices. These results provide important information about the impact of tea on the gastrointestinal fate of oat milk, and vice versa, which may be important for enhancing the healthiness of plant-based beverages.