N-(2-furanylmethylene)-3-methyl-1-butanamine as a novel color compound in Jiangxiangxing Baijiu

The color of Baijiu is a critical factor determining its quality and consumer acceptance. Among various color attributes, the intensity of the yellow hue is widely recognized as a reliable indicator of the aging degree of Jiangxiangxing Baijiu. In this study, we adopted a color-guided isolation and purification strategy to identify the key chromophoric yellow compound in Jiangxiangxing Baijiu. The strategy combined two-step high-performance liquid chromatography (HPLC) separation, Sephadex column chromatography for molecular weight estimation, and ultra-performance liquid chromatography-time-of-flight mass spectrometry (UPLC-TOF-MS) for targeted screening. The chemical structure of the target compound was confirmed as N-(2-furanylmethylene)-3-methyl-1-butylamine (NFB) via gas chromatography-electron ionization-Orbitrap mass spectrometry (GC-EI-Orbitrap-MS) analysis and chemical synthesis verification. Quantitative analysis revealed that the average concentration of NFB in soy sauce aroma-type Baijiu was 16.78 mg/L, with a concentration range of 9.58 to 25.80 mg/L in 13 base Baijiu samples. We further determined the content and color contribution of NFB in three sample sets: 12 base Baijiu samples with different aging years, 14 base Baijiu samples from seven production rounds, and 45 commercial Baijiu samples representing three different aroma types. The color contribution of NFB was 25%-37% in 1-5-year aged Baijiu, but it decreased notably to 7%-15% in 6-18-year aged samples. Additionally, NFB remained relatively stable with a slight increase during the early aging stage (1-5 years). It also showed a steady increasing trend in base Baijiu samples produced across different fermentation rounds.