Binding Mechanism and Taste-Masking Effect of Milk Proteins with Flavonoids from Pandan Revealed by Spectroscopic and Electronic Tongue Analysis

With the growing interest in pandan-based products, bitterness and astringency associated with flavonoids may limit their sensory acceptance. This study investigated the interactions and taste-modulating effects of two milk proteins, β-casein (β-CN) and β-lactoglobulin (β-LG), with two representative bitter flavonoids, catechin (C) and naringin (NAR), in aqueous model systems. Fluorescence spectroscopy showed that both flavonoids produced concentration-dependent quenching of the milk proteins. β-CN exhibited more pronounced interaction-related spectroscopic responses than β-LG, which may be associated with its flexible and intrinsically disordered structure. Molecular docking predicted hydrogen-bonding and hydrophobic interactions in all four protein–flavonoid systems, with catechin and naringin interacting mainly with the internal hydrophobic cavity of β-LG and surface-exposed regions of the β-CN model. Circular dichroism and Fourier-transform infrared spectroscopy indicated ligand-dependent structural changes. For β-LG, catechin slightly decreased the estimated antiparallel and total β-sheet fractions, whereas naringin produced a modest increase. For β-CN, catechin produced a more apparent redistribution between the estimated α-helix and β-sheet fractions, while naringin caused comparatively smaller changes. Electronic tongue measurements showed that the addition of the milk proteins reduced the bitterness- and astringency-related sensor responses of catechin and naringin. Under the tested conditions, β-CN produced greater attenuation of these responses than β-LG, while the umami-related response remained comparatively high. These findings support the potential application of milk proteins as taste-modulating components in flavonoid-containing dairy formulations, although validation in real food matrices is required.