Controlling the taste receptor accessible structure of rebaudioside A via binding to bovine serum albumin

• Rebaudioside A—bovine serum albumin binding was characterized.
• Presence of BSA alters the orientation of Reb A in water and orange juice.
• Bitter aglycone of Reb A (steviol) binds to the hydrophobic cavities of BSA.
• Method could be used to moderate bitterness of Reb A.

We illustrate a method that uses bovine serum albumin (BSA) to control the receptor-accessible part of rebaudioside A (Reb A). The critical micelle concentration (CMC) of Reb A was found to be 4.5 mM and 5 mM at pH 3 and 6.7 respectively. NMR studies show that below its CMC, Reb A binds weakly to BSA to generate a Reb A-protein complex (“RPC”), which is only modestly stable under varying conditions of pH (3.0–6.7) and temperature (4–40 °C) with its binding affinities determined to be in the range of 5–280 mM. Furthermore, saturation transfer difference (STD) NMR experiments confirm that the RPC has fast exchange of the bitterness-instigating diterpene of Reb A into the binding sites of BSA. Our method can be used to alter the strength of Reb A-receptor interaction, as a result of binding of Reb A to BSA, which may ultimately lead to moderation of its taste.