CO-Treated vs. Untreated Tuna: Color & Buying Guide
CO-Treated vs. Untreated Tuna: What Buyers Should Check
A bright red tuna steak can look appealing, but color alone cannot tell you how fresh it is. This guide explains how to compare tuna by species, cut, treatment information and handling history before choosing a product.
What does CO treatment mean?
Carbon monoxide (CO) can be used as a color fixative in fish. It is different from carbon dioxide (CO2). The FDA notes that color can be affected by treatments and packaging, as well as other factors, so it should not be used alone to judge freshness. Color retention does not establish a safe storage period.
Compare the same species and cut
Our yellowfin products are also called Ahi. Albacore is a different species; a fresh whole albacore is not an untreated Ahi steak. Compare equivalent cuts and ask about treatment for the specific product or batch. Do not infer treatment from a photograph or from the word “fresh.”
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| Question | What to check |
|---|---|
| Which tuna is it? | Species and cut: yellowfin steak, yellowfin saku block, albacore or bluefin belly. |
| Has it been color-treated? | Product specifications, package information and supplier confirmation. |
| Fresh or frozen? | Shipping condition and storage instructions for the selected item. |
| How much am I buying? | Selected pack weight and portions, rather than the photograph alone. |
| How will I prepare it? | Confirm suitability for the intended preparation before ordering. |
Choose a format for your meal
- Frozen yellowfin Ahi steaks for portioned meals.
- Fresh Ahi tuna steaks for a planned fresh-fish delivery.
- Yellowfin saku blocks when a regular block shape is useful for slicing.
These links compare shopping formats; they do not certify treatment status or suitability for raw consumption. Browse the Tuna collection or the broader Fish catalog.
Receiving, storage and preparation
Check the condition of the delivery and follow the package instructions. Refrigerate promptly at 40°F or below. Do not use a red appearance as a reason to extend storage. Raw or lightly seared tuna carries foodborne-illness risk; a quick surface sear does not cook the center. For a cooked meal, see our Ahi tuna cooking guide. For more detail, read our tuna storage guide.
Video
Source: FDA: Selecting and Serving Fresh and Frozen Seafood Safely.
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