NMR-Based Tastant Polymer Interaction Studies and the Influence on the Taste Perception of Red Wine

Using a quantitative H-1 NMR-based approach, molecular interactions between key taste active compounds and high-molecular-weight (HMW) polymers were directly investigated in red wine. Analysis of qualitative and quantitative H-1 NMR spectra over time allowed a distinction of three interaction scenarios: (i) no interactions for flavon-3-ol glycosides, ellagitannins, carbohydrates, and amino acids; (ii) changes in the chemical shift to lower frequencies for flavan-3-ols and phenolic acid ethyl esters; and (iii) changes in the chemical shift to higher frequencies for phenolic acids, organic acids, inorganic salts, and alditols. Additionally, using liquid chromatography-tandem mass spectrometry (LC-MS/MS), quantitative H-1 nuclear magnetic resonance (qHNMR), and high-performance ion chromatography (HPIC), a taste reconstitution model of Primitivo red wine was established for the first time. Human sensory experiments with the new taste recombinant and different HMW fractions demonstrated the influence of the tastant polymer interactions on the sour and salty taste perception of red wine and the intrinsic bitter and astringent taste of the polymers. Further, the influence of the molecular weight cutoff (MWCO) of the polymers and the pH value on the tastant polymer interactions was analyzed. Especially, the HMW fractions 30-50 kDa and >50 kDa caused strong shifts to lower and higher frequencies, respectively. NMR-based interaction studies at different pH values revealed a maximum of interactions at pH 4.0. Based on these results, flavor changes in red wine caused by tastant polymer interactions can be predicted on a molecular level in the future.