Targeted quantitation of 48 basic taste-active compounds in commercial meatlike process flavors, calculation of dose-overthreshold factors, and basic taste re-engineering, followed by activity-guided fractionation, revealed, next to l-glutamate and 5′-ribonucleotides, a series of N-acetylated amino acids and S-((4-amino-2-methylpyrimidin-5-yl)­methyl)-l-cysteine as taste-modulating compounds. The N-acetylated amino acids imparted kokumi enhancement with rather high taste thresholds ranging up to 1800 μmol/L (N-acetylmethionine) in model broth. In comparison, S-((4-amino-2-methylpyrimidin-5-yl)­methyl)-l-cysteine, found to be formed by a Maillard-type reaction of thiamine and cysteine, is reported for the first time to exhibit strong kokumi enhancement above a low threshold concentration of 120 μmol/L (model broth). These results will open new avenues toward a knowledge-based optimization of thiamine-containing process flavors.

Increasing the thiamine concentration in a respective process flavor yields a product with a significant higher kokumi activity. S-plot analysis of the mass spectrometric data revealed beside thiamine itself, 4-methyl-5-thiazoleethanol, (S)-((4-amino-2-methylpyrimidin-5-yl)­methyl)-l-cysteine, N-((4-amino-2-methylpyrimidin-5-yl)­methyl)­formamide, 3-(((4-amino-2-methylpyrimidin-5-yl)­methyl)­thio)-5-hydroxypentan-2-one, and 2-methyl-5-(((2-methylfuran-3-yl)­thio)­methyl)­pyrimidin-4-amine as marker molecules for a process flavor with higher thiamine concentration. Sensory-based targeted isolation revealed that (S)-((4-amino-2-methylpyrimidin-5-yl)­methyl)-l-cysteine, 3-(((4-amino-2-methylpyrimidin-5-yl)­methyl)­thio)-5-hydroxypentan-2-one, and 2-methyl-5-(((2-methylfuran-3-yl)­thio)­methyl)­pyrimidin-4-amine showed an influence on the kokumi taste activity with taste threshold concentrations between 35 and 120 μmol/L. An adapted mass spectrometric-based carbon module labeling experiment as well as quantitative studies clearly demonstrated thiamine as the only precursor and an intermolecular formation pathway for the compounds (S)-(((4-amino-2-methylpyrimidin-5-yl)­methyl)­thio)-5-hydroxypentan-2-one and 2-methyl-5-(((2-methylfuran-3-yl)­thio)­methyl)­pyrimidin-4-amine. On the basis of the knowledge that several thiamine derivatives showed taste-modulating activity, selected thiamine-based binary model reactions and synthesis were carried out. This resulted in the isolation of further thiamine-derived taste modulators like (S)-((4-amino-2-methylpyrimidin-5-yl)­methyl)-l-cysteinylglycine, (S)-3-((((4-amino-2-methylpyrimidin-5-yl)­methyl)­thio)­methyl)­piperazine-2,5-dione, 3-(((4-amino-2-methylpyrimidin-5-yl)­methyl)­thio)­pentan-2-one, 5-(((furan-2-ylmethyl)­thio)­methyl)-2-methylpyrimidin-4-amine, and (4-amino-2-methylpyrimidin-5-yl)­methanethiol, 2-methyl-5-((methylthio)­methyl)­pyrimidin-4-amine with taste thresholds ranging from 35 to 880 μmol/L.

Soy sauce, one of the most common Asian fermented foods, exhibits a distinctive savory taste profile. In the present study, targeted quantitation of literature-known taste compounds, calculation of dose-over-threshold factors, and taste re-engineering experiments enabled the identification of 34 key tastants. Following the sensoproteomics approach, 14 umami-, kokumi-, and saltenhancing peptides were identified for the first time, with intrinsic taste threshold concentrations in the range of 166−939 μmol/L and taste-modulating threshold concentrations ranging from 42 to 420 μmol/L. The lowest taste-modulating threshold concentrations were found for the leucyl peptide LDYY with an umami-and salt-enhancing threshold of 42 μmol/L. Addition of the 14 newly identified peptides to the taste recombinate (aRec Dipeptides ) increased the overall taste intensity and mouthfulness of the recombinate, and comparison with the authentic soy sauce confirmed the identification of all key tastants. Finally, these data as well as the quantitative profiling of several (non)-fermented foods highlight the importance of fermentation with respect to taste formation. On the basis of this knowledge, microorganisms with specific digestion patterns may be used to tailor the taste profile and especially the salt taste sensation of soy sauces.