Revealing Volatile Odor Compounds in Watermelon Juice to Enhance Fructose Sweetness Perception: Sensory Evaluation and Molecular Docking Techniques

Odor-induced sweetness enhancement (OISE) is an effective approach to lower sugar intake. In this study, static and dynamic sensory evaluations, combined with molecular docking, were used to explore the mechanism underlying sweetness enhancement in fructose solutions induced by watermelon juice odor compounds. Sensory evaluation results showed that the seven volatile odor compounds (VOCs) (ethyl acetate, ethyl propionate, octanal, (E,E)-2,4-hexadienal, (E)-2-octenal, methyl heptenone, and geranyl acetone) from watermelon juice could significantly increase the sweetness intensity of a 2.5% fructose solution, and the potency of OISE was significantly enhanced within 10 s. (E,E)-2,4-hexadienal, ethyl propionate, and methylheptenone showed the most significant OISE effects, which aligned with the sensory preference results. Further, molecular docking was used to explore the interactions between VOCs, fructose, and sweet receptors. The results showed that T1R2 was the main receptor for binding fructose and VOCs, and the interaction forces were primarily hydrogen bonds and hydrophobic interactions. In the presence of VOCs, the amino acid residues that formed hydrogen bonds with fructose were highly repetitive, with the main difference being the bond length, indicating the important role of flavor-sweetener receptor interactions in lowering fructose content and enhancing sweetness perception. Thus, this study provides a scientific basis for developing sugar-reduction technology based on aroma, in addition to enhancing sweetness.