Carbon Monoxide Treatment in Tuna: Regulatory Divergence and Trade Risks for Seafood Exporters
What Is CO Treatment?
Carbon monoxide treatment involves exposing fish flesh to CO gas, typically after filleting or portioning. CO binds with myoglobin in the muscle tissue to form carboxymyoglobin, which retains a stable, bright red color even after the fish has lost freshness. In practical terms, CO treatment can make older or lower-grade tuna look fresh and premium.
The practice is used primarily in tuna loins and steaks destined for foodservice and retail, as well as in some tilapia and smoked fish products. Its commercial appeal is obvious: it extends visual shelf life and reduces discoloration-related markdowns.
Why Regulators Disagree
The core issue is transparency. CO treatment does not preserve freshness - it only masks signs of deterioration. This creates a fundamental conflict between commercial interests and consumer protection.
European Union
CO treatment of fishery products is prohibited under EU food law. Products treated with CO are considered to have misleading appearance and are refused entry. This is a hard ban, not a labeling issue.
United States
CO treatment is permitted for certain fishery products, but the FDA requires that the process be disclosed. Treated products must be labeled to indicate that CO has been used. Undisclosed treatment is considered misbranding.
Japan
CO treatment is generally permitted for tuna, but industry practice varies, and some retailers require disclosure. Regulatory oversight has tightened in recent years.
China and Southeast Asia
Regulations vary by market. Some countries permit CO treatment with labeling, while others have no specific framework. This regulatory patchwork creates significant compliance risk for exporters shipping to multiple destinations.
How CO Treatment Is Detected
Import authorities use several methods to screen for undisclosed CO treatment:
Visual inspection
An unusually uniform, bright red color in tuna that has been thawed or stored for extended periods is a red flag.
Spectrophotometric analysis
Measures the ratio of carboxymyoglobin to total myoglobin in tissue samples.
Gas chromatography
Detects residual CO in fish tissue with high sensitivity.
DNA and freshness markers
Combined with ATP degradation indicators (K-value), CO-treated fish can be identified by the mismatch between visual freshness and biochemical freshness.
Practical Guidance for Exporters
Competitive advantage
The company conducted a competitive advantage analysis to identify its strengths and weaknesses compared to its rivals.
Know your destination market
Confirm CO regulations before accepting orders. EU-bound shipments should never be CO-treated.
01
Verify supplier practices
If sourcing tuna loins or steaks, audit processing facilities for CO use and labeling compliance.
02
Document everything
For markets where CO is permitted, maintain clear records of treatment, labeling, and buyer acknowledgment.
03
Do not rely on CO to solve freshness problems
The practice is a cosmetic intervention, not a preservation method. Buyers increasingly test for biochemical freshness indicators.
04
Consider alternatives
Modified atmosphere packaging (MAP) and proper cold-chain management achieve shelf-life extension without regulatory controversy.
05
For seafood exporters, CO treatment is a classic example of a practice that offers short-term commercial benefit but carries long-term compliance and reputational risk. In an era of increasing supply chain scrutiny, transparency remains the safest commercial strategy.
