Interaction of β‐casein with (−)‐epigallocatechin‐3‐gallate assayed by fluorescence quenching: effect of thermal processing temperature

Abstract

Summary The interactions between the flavan‐3‐ol (−)‐epigallocatechin‐3‐gallate ( EGCG ) and bovine β‐casein in phosphate‐buffered saline ( PBS ) of pH 6.5 subjected to thermal processing at various temperatures (25–100 °C) were investigated using fluorescence quenching. The results indicated that different temperatures had different effects on the structural changes and EGCG ‐binding ability of β‐casein. At temperatures below 60 °C, the β‐casein– EGCG interaction changed little ( P > 0.05) with increasing temperature. At temperatures above 80 °C, native assemblies of β‐casein in solution dissociated into individual β‐casein molecules and unfolded, as demonstrated by a red shift of the maximum fluorescence emission wavelength (λ max ) of up to 8.8 nm. The highest quenching constant ( K q ) and the number of binding sites ( n ) were 0.92 (±0.01) × 10 13 m −1 s −1 and 0.73 (±0.02) (100 °C), respectively. These results provide insight into the potential of interactions between β‐casein– EGCG that may modulate bioactivity or bioavailability to be altered during thermal process.