Did you know this?

1. Rotten or low-grade tuna is the starting point

Tuna that is old, improperly refrigerated, or beginning to spoil turns brown/gray as myoglobin oxidizes.

This discoloration makes it unsellable at full price, especially for sashimi or “ahi” marketing.

2. Chemical treatment restores the red color

The fish is exposed to carbon monoxide (CO) or nitrites / nitrates.

These chemicals bind to myoglobin, locking in an artificial bright cherry-red color.

The color remains even as the fish continues to spoil internally.

3. The color masks danger

Normally, browning is a natural spoilage signal.

CO-treated tuna looks “fresh” while:

Histamine levels may be high

Bacterial load may be elevated

Texture and smell cues are muted or delayed

This increases risk of scombroid (histamine) poisoning.

4. Sold as “ahi,” “sushi-grade,” or “fresh”

The treated fish is often:

Labeled vaguely (no CO disclosure)

Frozen, thawed, and re-frozen

Sold to restaurants, poke shops, and grocery stores

Consumers assume red = fresh. That assumption is exploited.

5. Legal loopholes, not transparency

In many regions:

CO treatment is technically legal

Disclosure is not required

This makes it a marketing trick, not food safety innovation.

Key takeaway

Bright red tuna is not a freshness indicator.

In many cases, it’s:

Old fish

Chemically “cosmetically fixed”

Sold on appearance rather than quality

True fresh tuna ranges from deep red to burgundy, and naturally darkens with time.

We have a grocery scanner app that allows you to scan ingredient labels to see if what you're buying contains harmful ingredients.

Comment "SCAN" and we'll send you access.

https://blossom.primal.net/57ab69439998cd4be335fd6a482545494205c1b7a7371fc198aae2409571b01f.mp4