Antioxidant activity and recovery of green tea catechins in full-fat cheese following gastrointestinal simulated digestion

• There was no effect of green tea extract (GTE) addition on the composition of hard full-fat cheese.
• GTE increased total phenolic content and antioxidant activity of the hard full-fat cheese.
• Catechins from GTE partitioned selectively into the cheese curd and whey.
• The green-tea catechins were recovered differently from full-fat cheese digesta.
• Hydrophobic associations between milk fat and green-tea catechins occur.

Green tea extract (GTE) was incorporated into full-fat cheeses at 250, 500, and 1000 ppm to investigate the effect of green tea catechins on antioxidant properties and microstructure of cheese, and recovery of catechins. Cheeses were ripened for 90 days at 8 °C followed by simulated gastrointestinal digestion. The composition on Day 0, and pH, total phenolic content (TPC), and antioxidant activity (AA) of the cheeses on Days 0, 30, and 90, were determined. The concentrations of the major GTE catechins in the curd and from the digesta of mature cheeses were determined using HPLC. Addition of GTE significantly (p ≤ 0.05) decreased the pH of whey and curd during cheese manufacture and ripening, however there was no significant (p > 0.05) effect on moisture, protein, or fat contents. Addition of GTE increased TPC and AA at all concentrations, but in a non-linear manner. Individual catechins were selectively retained in the curd, whereas different portions were recovered from the cheese digesta. Transmission electron microscopy showed that the ripened control cheese had a regular distribution of milk fat globules entrapped in a homogeneous structure of casein proteins, which was disrupted by GTE. Interactions between green-tea catechins and cheese fat were confirmed by Fourier transform infrared spectroscopy.