Interaction of β-lactoglobulin with (−)-epigallocatechin-3-gallate under different processing conditions of pH and temperature by the fluorescence quenching method.

The binding interactions between (−)-epigallocatechin-3-gallate (EGCG) and bovine β-lactoglobulin ( β-LG) during food processing under different temperatures (25-100 °C) and pH levels (3.2-7.4) were investigated using the fluorescence quenching method. The results indicated that temperature and pH had different effects on the structure and EGCG-binding ability of β-LG. At a higher pH (≥6.4) and temperature (≥80 °C), the structure and conformation of β-LG were more open than those of its native state due to the heat-induced denaturation and unfolding of protein, which increased its binding affinity with EGCG through hydrophobic interactions and hydrogen bonds, which in turn promoted its further unfolding. The highest binding constant ( K) and the binding site numbers (n) were 12.50 (±0.60) × 10 M (pH 6.4, 80 °C), and 0.62 (±0.02)~0.97 (±0.16), respectively. However, at 100 °C and a neutral pH, the oxidative loss of EGCG during thermal processing probably led to a decrease in β-LG-EGCG interactions. These results would be helpful to better understand the relevance of the β-LG-EGCG interaction to the bioactivity and bioavailability of EGCG during food processing, and to maintain the health benefits of this type of functional products in the food industry. [ABSTRACT FROM AUTHOR]