How CO2 Monitoring Is Revolutionizing Food Safety
A simple gas sensor is now the most powerful weapon against invisible grain contaminants.
Imagine a world where millions of tons of food become contaminated before ever reaching a plate. This isn't a hypothetical scenario—it's a persistent global challenge in grain storage. Now, scientists have discovered an unlikely ally in this battle: carbon dioxide. In storage silos worldwide, real-time CO2 monitoring is emerging as an early-warning system against grain spoilage and dangerous mycotoxin contamination, offering a powerful tool to safeguard our food supply and reduce waste.
Mycotoxins are toxic compounds produced by moulds that commonly grow on staple cereals like wheat, maize, and oats. These heat-stable molecules are difficult to remove or inactivate once formed in a food product. Exposure through consumption can lead to serious health issues including immunotoxicity, teratogenicity, mutagenicity, and carcinogenicity. Their presence has prompted strict international regulations, particularly in the European Union/UK where maximum legal limits exist for aflatoxins, ochratoxin A, deoxynivalenol, and other mycotoxins in cereals2 .
The post-harvest phase represents a critical vulnerability point in our food system. Poor storage management can result in significant quality losses due to either pest activity or mould spoilage with associated mycotoxin contamination.
Developed Countries
Lower Middle-Income Countries
Estimated grain loss percentages in different economic contexts2
All living grains respire, naturally producing CO2 as they break down stored carbohydrates. However, when moulds and fungi begin to grow, this respiration increases dramatically. Elevated CO2 levels thus serve as an early indicator of biological activity from spoilage microorganisms long before visible damage or temperature changes occur2 7 .
Grain's insulating properties mean temperature changes often lag significantly behind actual spoilage. By the time a temperature cable detects a "hotspot," significant damage may have already occurred.
As one industry expert notes, "CO₂ levels move more rapidly through air currents than heat conducts through grain"4 . This makes CO2 monitoring a faster and more sensitive approach to spoilage detection.
A groundbreaking study published in the Journal of the Science of Food and Agriculture provides compelling evidence for CO2 monitoring's effectiveness. Researchers designed a comprehensive experiment to compare real-time CO2, temperature, and relative humidity sensors as indicators of stored grain quality1 2 .
Used mini-silos containing naturally contaminated wheat grain stored at different moisture contents (15-30%) to evaluate effects on grain respiration1 .
Utilized two pilot-scale silos holding 2.5 tonnes of wheat each, equipped with ATEX-compliant CO2/RH/T sensors. To simulate a real-world storage problem, researchers created a 'wet pocket' by introducing water to a localized area, mimicking the water ingress that might occur through a leak or condensation1 2 .
The findings were striking. The simulated wet pocket triggered a rapid rise in CO2 levels while temperature remained relatively stable1 . This demonstrated CO2's superior sensitivity as an early warning indicator.
Comparison of CO2 and temperature responses to spoilage conditions
The affected wet pocket area showed a clear increase in the concentration and diversity of mycotoxins, particularly aflatoxin B1, aflatoxin B2, deoxynivalenol, deoxynivaenol-3-glucoside, and moniliformin1 . The unaffected regions maintained significantly lower contamination levels.
| Mycotoxin | Affected Region | Unaffected Region |
|---|---|---|
| Aflatoxin B1 | Significantly Elevated | Lower |
| Aflatoxin B2 | Significantly Elevated | Lower |
| Deoxynivalenol | Significantly Elevated | Lower |
| Deoxynivalenol-3-glucoside | Significantly Elevated | Lower |
| Moniliformin | Significantly Elevated | Lower |
Table 1: Comparison of mycotoxin levels in grain samples from affected and unaffected regions of storage silos1
| Water Activity (a_w) | Temperature | Respiration Rate (μg CO₂ kg⁻¹ h⁻¹) |
|---|---|---|
| 0.70 | 15°C | Low |
| 0.70 | 20°C | Low |
| 0.90 | 15°C | Moderate |
| 0.90 | 20°C | Moderate |
| 0.95 | 15°C | High (≥25) |
| 0.95 | 20°C | High (≥25) |
Table 2: Respiration rates increase with higher water activity and temperature, with mycotoxins exceeding legal limits when respiration rates reached ≥25 μg CO₂ kg⁻¹ h⁻¹ at water activity levels ≥0.906
Implementing an effective CO2 monitoring system requires specific equipment and technologies. Here are the key components used in the featured research:
Precisely detects CO₂ concentrations and temperature. Used in mini-silo experiments (0–15% ±0.2% accuracy)2 .
Small-scale controlled environment for initial testing. Contained naturally contaminated grain at varying moisture levels2 .
Intermediate-sized storage systems for realistic trials. Held 2.5 tonnes of grain to bridge lab findings with real-world conditions1 .
Measures available water in grain samples. Confirmed moisture content and water activity levels in grain samples2 .
Identifies and quantifies multiple mycotoxins. Analyzed grain samples for precise mycotoxin contamination levels6 .
Table 3: Essential research equipment for CO2 monitoring studies in grain storage research
The implications of this research extend far beyond laboratory settings. Companies are already developing commercial applications based on these principles. As one industry provider explains: "Carbon dioxide monitoring provides a real-time indicator of grain spoilage by detecting changes in CO2 levels, which move more rapidly through air currents than heat conducts through grain"4 .
Practical installation typically involves placing CO2 sensors in either the headspace above the grain or the plenum below it, connected to monitoring nodes that transmit data for analysis4 .
This technology integrates with existing temperature cable systems, significantly enhancing grain storage management without requiring complete infrastructure overhaul.
Research continues to refine our understanding of the relationship between CO2 levels and grain quality. Recent studies have examined how different grains produce varying CO2 signatures under comparable conditions, potentially allowing for grain-specific monitoring protocols6 .
The integration of predictive modelling with real-time CO2 data represents another frontier, potentially enabling silo managers to anticipate contamination risks before they materialize2 .
As climate change alters storage conditions and increases contamination risks in major grain-producing regions, the importance of effective monitoring technologies becomes even more pronounced2 .
What begins as a simple CO2 sensor in a silo ultimately contributes to a more resilient, efficient, and safe global food system—proof that sometimes the most powerful solutions emerge from watching the invisible signs nature provides.
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