2D-GC Maps Sulfur Compounds in Soy Sauce

Researchers systematically investigating the flavor contribution of sulfur compounds to the soy sauce flavor Baijiu (SSFB) by integrating traditional flavor analysis with machine learning methods identified a total of 88 sulfur compounds through the comprehensive two-dimensional gas chromatography-(2D-GC) hydrogen sulfide chemiluminescence detector. A paper based on this work was published in the journal npj Science of Food.¹

What is Baijiu and Why is Understanding its Flavor Chemistry a Challenge?

Chinese baijiu is one of the most widely consumed distilled spirits in the world, celebrated for its distinctive production methods and complex flavors.² Scientists have extensively studied what gives baijiu its distinctive taste and smell, uncovering the connection between its key aromas and the chemical compounds responsible for them. Remarkably, the flavor of baijiu is largely determined by trace ingredients that make up only a tiny fraction (just 1-2%) of its overall composition.³ By 2023, researchers had identified more than 3400 distinct aromatic compounds in baijiu, spanning hundreds of esters, acids, nitrogen-containing compounds, and sulfur-containing compounds.⁴ Research has shown that esters are largely responsible for baijiu's floral, fruity, and some of its sweeter aromas, while aldehydes and alcohols also play a role in its floral character.^5-7 In addition, acid compounds primarily impart acidic aromas.^8,9 Despite this, the specific compounds behind SSFB's most iconic and distinctive aromas are still not well understood.¹

What Did the Study Find About the Role of Sulfur-Containing Compounds in Shaping the Flavor of Soy Sauce?

The researchers report that the importance of these sulfuric flavor contributors was confirmed through multiple analytical approaches, which also revealed clear links between these compounds and eight distinct aroma characteristics. Eight key sulfur-containing compounds were identified as the most significant, selected using a combination of several advanced data analysis methods. Experiments adding these compounds to the beverage confirmed that they meaningfully enhanced two of its most prized and distinctive aromas.¹

Interestingly, the study also found that the effect of these compounds depended on the age of the product: in younger versions, they boosted a wider range of aromas including floral and fruity notes, while in older, more mature versions, their influence was more focused,intensifying the signature aromas while having less of an effect on the others.¹

“This study,” wrote the authors of the paper,¹ “overcame the limitations of traditional methods in analyzing high contribution flavor data by establishing a research framework integrating traditional analysis, machine learning, and experimental validation. It clarified the pivotal role of sulfur-containing compounds in forming the key aromas of SSFB, providing explicit target compounds and theoretical foundations for directed flavor regulation.”

The researchers suggest that future work focus on deep analysis of the transformation pathways of these key compounds and their interaction networks to unveil the underlying mechanisms of flavor formation in SSFB.¹

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References

1. Yang, S.; Zhang, X.; Shen, Y. et al. Investigating the Flavor Contributions of Sulfur Compounds in Soy Sauce Flavor Baijiu Using Flavoromics and Machine Learning. NPJ Sci Food 2026. DOI: 10.1038/s41538-026-00929-x
2. Liu, H. L.; Sun, B. G. Effect of Fermentation Processing on the Flavor of Baijiu. J. Agr. Food Chem. 2018, 66, 5425-5432. DOI: 10.1021/acs.jafc.8b00692
3. He, F.; Xiao, P.; Yang, S. et al. Separation and Characterization of Sweet Compounds in Baijiu by Molecular Distillation Combined with Molecular Sensory Science. Food Chem. 2025, 465 (Pt 2), 142124. DOI: 10.1016/j.foodchem.2024.142124
4. He, F. et al. Determination of Taste Threshold of Flavor Compounds in Baijiu. J. Chin. Inst. Food Sci. Technol. 2024, 24, 371-383.
5. Zhou, J.; Rao, W.; Hu, S. et al. Unveiling Aroma Evolution in Chinese Te-Flavor Baijiu with Ageing Times using GC-IMS, GC-O-QTOF and Electronic Sensory Techniques. Food Chem. 2025, 491; 145250. DOI: 10.1016/j.foodchem.2025.145250
6. Yang, S.; Lv, S.; Xu, L. et al. Influences of Thioalcohols on the Release of Aromas in Sesame-Flavor Baijiu. Food Res Int.2024, 191, 114733. DOI: 10.1016/j.foodres.2024.114733
7. Du, J.; Li, Y.; Xu, J. et al. Characterization of Key Odorants in Langyatai Baijiu with Jian Flavour by Sensory-Directed Analysis. Food Chem. 2021, 352, 129363.DOI: 10.1016/j.foodchem.2021.129363
8. He, F.; Yang, S.; Shen, Y. et al. Decoding Baijiu Key Sour Compounds: Molecular Distillation-Enhanced Enrichment and Sensory-Guided Identification. LWT-Food Sci. Technol. 2025, 238, 118802. DOI:10.1016/j.lwt.2025.118802
9. Liu, Y. J.; Bai, T. T.; Wu, D. H. et al. Elucidating the Aging Mechanism of Fuyu-Flavor Baijiu Mediated by Metal Ions via GC-MS, Spectroscopy, Electrochemistry, and SEM-EDS. Food Chem. 2026, 502, 147641. DOI: 10.1016/j.foodchem.2025.147641