Interaction of green tea polyphenols with dairy matrices in a simulated gastrointestinal environment

Abstract

The consumption of polyphenols in green tea has been associated with beneficial health effects. Although polyphenols are unstable in the intestinal environment, they may be protected by interactions with dairy proteins during digestion. The objectives of this study were to evaluate the effect of a green tea extract on the digestibility of different dairy matrices and to monitor the antioxidant activity of these matrices with or without the green tea extract during digestion in a simulated gastrointestinal environment. Milk, yogurt and cheese with similar fat-to-protein ratios were subjected to simulated digestion. Matrix degradation, protein and fat hydrolysis, polyphenol concentration and radical scavenging activity were analyzed during gastric and intestinal digestion phases. Cheese was the matrix most resistant to protein and fat digestion. The addition of the green tea extract significantly decreased proteolysis in the gastric phase but had no effect in the intestinal phase. The kinetics of fatty acid release was reduced by the presence of the green tea extract. Transition from the gastric phase to the intestinal phase induced a 50% decrease in the antioxidant activity of the control (tea extract dispersed in water) due to the degradation of polyphenols. The presence of dairy matrices significantly improved polyphenol stability in the intestinal phase and increased the antioxidant activity by 29% (cheese) to 42% (milk) compared to the control. These results suggest that simultaneous consumption of green tea and dairy products helps to maintain the integrity and antioxidant activity of polyphenols during digestion.

Effect of In Vitro Digestion on the Total Antioxidant Capacity and Phenolic Content of 3 Species of Oregano (Hedeoma patens, Lippia graveolens, Lippia palmeri)

“…Herein, conjugated non‐phenolic acids such as trans‐cinnamic acid, as well as ferulic acid, are stable at a high pH. It is important to mention that the loss of individual phenolics after the GI process has been attributed, in addition to the pH changes, to the possible interactions between polyphenols and other components of the digestive juices, such as enzymes and electrolytes, which needs to be studied further (Friedman and Jürgens ; Lamothe and others ). Additionally, the structural transformation that occurs as a result of the conjugation of polyphenols with proteins might render them undetectable in the individual chromatographic analysis by UPLC‐PDA.…”

Interaction of Whey Proteins with Phenolic Derivatives Under Neutral and Acidic pH Conditions

“…Complex phenolic compounds, such as tannins, are well known for binding to proteins to reduce protein digestibility (Bravo ). When incorporated into a dairy protein matrix, green tea extract was found to have a significantly improved phenolic stability in gastrointestinal tract during in vitro digestion, and the protein digest would sustain a higher antioxidant activity (Lamothe and others ). However, for the specific phenolic compounds, including the ubiquitous gallic acid (GA) and its derivative epigallocatechin gallate (EGCG), the relationship between protein binding and digestion is not always clear, especially after the protein has been preexposed to phenolics in different pH environments.…”

The behaviour of green tea catechins in a full-fat milk system under conditions mimicking the cheesemaking process

“…In addition, the TPC values of recovered subnatants for either C or EGCG showed less than an additive trend compared to the standard curve (data not shown), indicating that the added catechins could not be fully recovered in filtrates and hence show phenolic activity. Losing phenolic activity can result from the possible well-known interactions between milk proteins, especially caseins, and catechins (Yuksel et al 2010;Ye et al 2013;Lamothe et al 2014). Notwithstanding, some of the interactions might be reversible and can be counteracted by the Folin-Ciocalteu reagent and hence be counted as a part of the TPC results.…”