GC-IMS Detects Early Mold Warning Signs in Cigar Tobacco

Cigar tobacco leaves are packed with nutrients, which unfortunately also makes them a good target for mold growth during fermentation and storage. A joint research team from the Zhengzhou Tobacco Research Institute and Huazhong Agricultural University in China set out to study the specific smells given off by the main types of molds that grow on these leaves, with the goal of creating a smell-based early warning system to catch mold outbreaks before they get out of hand. To do this, they used gas chromatography-ion mobility spectrometry (GC-IMS) to detect telltale odor compounds as soon as mold first becomes visible. A paper based on their research was published in the journal Frontiers in Microbiology.¹

What Causes Mold Spoilage in Tobacco Products?

Molds that cause spoilage come in many different forms, but they tend to share a few things in common: they multiply quickly and can reproduce in several different ways. Research has documented 130 genera and 231 species of mold known to spoil various goods. When it comes to tobacco products specifically, the most common culprits are Aspergillus and Penicillium, with Trichoderma and Rhizoctonia showing up less often. Figuring out exactly which mold species are the main troublemakers is an important first step in preventing and controlling mold problems.^2,3

How Has Technology Evolved to Detect and Identify Mold Through the Compounds It Produces?

As chromatography and spectroscopy technology have advanced, identifying molds has increasingly relied on analyzing the scent compounds they give off as they grow and go about their metabolic processes.^4,5 Currently, methods like solid phase microextraction combined with gas chromatography-mass spectrometry (HS-SPME-GC-MS) and electronic "sniffer" devices are commonly used to detect these compounds,^6,7 but they typically require complicated sample preparation steps or specialized sensors. GC-IMS has therefore become a strong alternative option by separating out gas components using chromatography, then ionizing them and measuring how quickly they drift, which generates a unique signal for identification.⁸

How Did Researchers Test Different Mold Types on Cigar Tobacco Leaves?

The researchers isolated eight common mold types found naturally growing on cigar tobacco leaves, then deliberately introduced these molds' spores onto clean, sterile leaves to see how each one behaved. They used a combination of visual inspection and mold counting to score how aggressively each mold type grew. To make sense of the odor data from GC-IMS, they also used statistical tools that help identify patterns and pick out the most meaningful differences between samples. Based on how aggressively each mold grew, they sorted the eight types into two groups: "high-risk" molds (Aspergillus montevidensis, Penicillium chrysogenum, Aspergillus pseudoglaucus, and Aspergillus versicolor) and "low-risk" molds (Talaromyces funiculosus, Trichoderma longibrachiatum, Aspergillus chevalieri, and Aspergillus sydowii).¹

What Odor Compounds Did the Researchers Identify as Early Warning Signs of Mold Contamination?

In total, 66 different odor compounds were detected. The statistical analysis clearly separated the mold-contaminated leaves from the clean, uncontaminated ones, and it also grouped the mold strains in a way that matched how aggressively they grew. After carefully narrowing down the list to the most reliable and meaningful compounds, three stood out as strong, universal early-warning signs of mold contamination: 3-octanone, 2-pentanol, and 2-methyl-1-butanol. On top of that, 2-pentanol was found in notably higher amounts when the more aggressive, high-risk molds were present, suggesting it could also be used to gauge just how severe a mold infection is.¹

“GC-IMS,” write the authors of the paper,¹ “serves as a rapid and effective analytical tool for profiling dynamic VOC changes during fungal infection. The newly identified broad-spectrum markers and the quantitative classification model offer a promising targeted monitoring strategy to ensure safe cigar tobacco production.”

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References

1. Huang, K.; Zhang, G.; Liu, M. et al. Moldogenicity of Dominant Culturable Molds in Cigar Tobacco Leaves and GC-IMS-based Analysis of Volatile Organic Compounds. Front Microbiol. 2026, 17, 1843382. DOI: 10.3389/fmicb.2026.1843382
2. Zhang, C. X.; Wei, F.; Zhang, G. H. et al. Insight into the Characteristic Components of Cigar Tobacco. J Agric Food Chem. 2025, 73 (4), 2364-2372. DOI: 10.1021/acs.jafc.4c12094
3. Wei, M.; Shi, Y.; Song Z. et al. Microbial Community Analysis of Mildewed Cigar Tobacco Leaves from High-throughput Sequencing data. Ann. Microbiol. 2024, 74, 38. DOI: 10.1186/s13213-024-01783-6
4. Anfossi, L.; Giovannoli, C.; Baggiani C. Mycotoxin Detection. Curr Opin Biotechnol. 2016, 37, 120-126. DOI: 10.1016/j.copbio.2015.11.005
5. Chauhan, R.; Singh, J.; Sachdev, T. et al. Recent Advances in Mycotoxins Detection. Biosens Bioelectron. 2016, 81, 532-545. DOI: 10.1016/j.bios.2016.03.004
6. Zeng, S.; Zeng, F.; Guo, Y. et al. Characterization of Odors and Volatile Organic Compounds Changes to Recycled High-density Polyethylene Through Mechanical Recycling. Polym. Degradation Stability 2023, 208, 110263. DOI: 10.1016/j.polymdegradstab.2023.110263
7. Yin, X.; Fu, L.; Chen, W. J. et al. GC-MS-based Untargeted Metabolomics Reveals the Key Volatile Organic Compounds for Discriminating Grades of Yichang Big-leaf Green Tea. LWT 2022, 171, 114148. DOI: 10.1016/j.lwt.2022.114148
8. Christmann, J.; Weber, M.; Rohn, S. et al. Nontargeted Volatile Metabolite Screening and Microbial Contamination Detection in Fermentation Processes by Headspace GC-IMS. Anal Chem. 2024, 96 (9), 3794-3801. DOI: 10.1021/acs.analchem.3c04857