Identification of hydroxymethylpyrazines using mass spectrometry

Identification of 2-Hydroxymethyl-3,6-diethyl-5-methylpyrazine as a Key Retronasal Burnt Flavor Compound in Soy Sauce Aroma Type Baijiu Using Sensory-Guided Isolation Assisted by Multivariate Data Analysis

The burnt flavor (overcooked rice flavor) is often retronasally perceived during the soy sauce aroma type Chinese Baijiu (Chinese distilled spirit) tasting and regarded as an important quality marker of the Baijiu. The sensory-guided isolation approach assisted by multivariate data analysis was applied to identify the compounds responsible for the retronasal burnt flavor in the Baijiu. Using two-dimensional offline high performance liquid chromatography separation and taste dilution analysis, a subfraction with the highest burnt flavor intensity was isolated from the Baijiu sample. In the subfraction, six potential flavor compounds were detected by ultra performance liquid chromatography-mass spectrometry. The most probable burnt flavor compound was screened by projection to latent structure regression analysis of the correlation between the potential compounds and their impact on burnt flavor. The target compound was identified as 2-hydroxymethyl-3,6-diethyl-5-methylpyrazine by means of high-resolution mass spectrometry and chemical synthesis. Sensory evaluation revealed a relatively low burnt flavor threshold of 2.89 μmol/L in 53% ethanol aqueous solution. On the basis of the dose-overthreshold factor and addition experiment, this compound was confirmed as the key contributor to the burnt flavor of soy sauce aroma type Baijiu.