Antioxidant activity of milk and polyphenol-rich beverages during simulated gastrointestinal digestion of linseed oil emulsions

Polyunsaturated fatty acids (PUFA) are associated with health benefits. However, high PUFA intake increases the risk of lipid oxidation and formation of potentially toxic lipid oxidation species. The objective of this study was to determine the antioxidant activity of milk fractions (whole milk, skim milk, acid whey, ultrafiltration (UF) permeate) and polyphenol-rich beverages (green tea, grape juice) during simulated gastrointestinal digestion. We also determined the effect of milk and polyphenol-rich beverages on the formation of advanced oxidation species during in vitro digestion of PUFA-rich emulsion. Antioxidant activity during digestion of milk fractions emphasized the important role of proteins (more specifically caseins) and the contribution of fat to the antioxidant capacity of milk. In comparison to milk, the antioxidant activity of polyphenol-rich beverages was at least four times higher. During digestion of a PUFA-rich emulsion, the formation of 4-hydroxyhexanal (4-HHE) and 4-hydroxynonenal (4-HNE) in the intestinal phase were respectively reduced by 60% and 75%, in the presence of milk or polyphenol-rich beverages. Further reduction was observed when the emulsion was co-digested with both, milk and polyphenol-rich beverages (89% for 4-HHE and 93% for 4-HNE). These results suggest that the combination of milk and polyphenol-rich beverages increases the antioxidant activity and synergistically reduces the formation of toxic lipid oxidation species during simulated digestion of PUFA-rich foods.