In vitro digestion of apple tissue using a dynamic stomach model: grinding and crushing effects on polyphenol bioaccessibility

Food structure is a key determinant for the release of phenolic compounds during gastric and intestinal digestion. We evaluated the bioaccessibility of polyphenols from apple tissue during gastric digestion in vitro from bio-mechanical perspectives including the effects of gastric juice and mucin on the apple tissue matrix under simulated stomach peristalsis. The gastric model system was effective in releasing polyphenols because of simultaneous compression and extrusion, with 3 times higher release from coarse than from fine particles. However, bioaccessibility of polyphenols was reduced up to 44% in the presence of both cell walls and gastric mucin. Most individual phenolic molecules were gradually released and were stable in the gastric environment, except for procyanidin B2. The study suggests that the bioaccessibility of polyphenols from apples in the upper digestive tract is dependent on mechanical disintegration and the residual matrix present in the swallowed bolus.