Mechanism of sweetening effect of 2-methylbutyric acid and other 9 acids from sweet orange investigated by sensory evaluation, electronic tongue, and molecular simulation

This study investigates the sweetening effect of ten acids from sweet orange on 5% sucrose solution. It was discovered that trans-2-hexenoic acid, 2-methylbutyric acid and 3-methylbutyric acid notably enhanced sweetness, whereas decanoic acid significantly reduced sweetness. Acetic acid, propionic acid and butyric acid sweetened slightly at low concentration, but inhibited sweetness at high concentration. Hexanoic acid, octanoic acid were also sweetened, but the comfort level was declining. Nonanoic acid did not significantly sweeten or inhibit sweetness. The results of molecular docking revealed that hydrogen bonding and hydrophobic interactions were crucial for the binding of sucrose to the sweet taste receptor T1R2/T1R3. It has also found that LYS65, ASP278, SER165, GLU302, ASP142, and SER303 were key amino acids for sweetness. A 100 ns molecular dynamic simulation indicated that the addition of propionic acid reduced the equilibrium time from 60 ns to 10 ns to improve the combination of sucrose and T1R2/T1R3. This findings pave the way for developing low-sugar orange juice beverages by leveraging aroma substances to augment sweetness.