A shipment arrives. Someone on the receiving team opens a box, sees dark spots forming near the shell on a portion of the shrimp, and now has to make a call — often within minutes, often without a lab. Do you accept it, ask for a price adjustment, or reject the lot outright?

This is a decision guide for that exact moment, not a chemistry lesson. If you want the science behind why this happens, we’ve covered that separately — this piece is about what to actually do when it’s in front of you.

First: is it melanosis, or is it spoilage?

These get confused constantly, and they call for completely different responses.

Melanosis (black spot) is a cosmetic enzymatic reaction — dark spots, usually starting near the head and joints, that don’t affect food safety. On its own, it is not a sign the product is bad.

Actual spoilage shows up differently, and usually alongside other signs, not black spots alone:

  • An ammonia-like or sour odor, not the clean, mild ocean smell fresh shrimp should have
  • A soft, mushy, or slimy texture rather than firm flesh
  • Discoloration beyond localized black spots — yellowing, overall dulling, or a grayish cast to the flesh itself, not just the shell

If you’re only seeing dark spotting with none of the above, you’re most likely looking at melanosis, not spoilage. If you’re seeing spotting and any of the spoilage signs, treat it as a spoilage issue, not a cosmetic one — and escalate accordingly.

The practical decision framework

Accept. Light, localized spotting on a small share of the lot, with no odor or texture issues, is common and generally doesn’t affect the product’s safety or eating quality. Many buyers accept this without any adjustment, particularly for product headed to further processing rather than retail display.

Discount. Moderate spotting across a meaningful portion of the lot — enough to affect retail presentation or trigger customer complaints, but still isolated to appearance — is the most common case for a negotiated price adjustment rather than a full rejection. This is where documenting the percentage of the lot affected, with photos, matters most for the conversation with your supplier.

Reject. Heavy, widespread spotting combined with any spoilage indicator (odor, texture, non-localized discoloration) is a rejection, not a negotiation. At that point you’re not assessing a cosmetic issue anymore — you’re assessing whether the product is fit to sell at all.

What to ask your supplier before you decide

Before escalating a shipment issue, ask:

  • Was a sulfite treatment (like sodium metabisulfite) applied, and when relative to harvest? Melanosis suppression has a limited window — typically a few days — after which the reaction can resume even on correctly treated product. Spotting on a shipment that’s been in transit longer than that window isn’t necessarily a processing failure.
  • What’s the documented cold-chain history for this lot? Temperature excursions accelerate both melanosis and genuine spoilage — knowing whether the cold chain held tells you which one you’re more likely dealing with.
  • Can they provide comparison photos from pre-shipment inspection? A supplier doing real quality control should have their own documentation of what the lot looked like before it left, which helps establish whether spotting developed in transit or was already present.

How KATUNA handles this before it reaches you

KATUNA documents metabisulfite application timing and pre-shipment condition as standard practice — not something assembled after a complaint. If a shipment issue does come up, that documentation is what turns “he-said-she-said” into a fast, evidence-based resolution instead of a drawn-out dispute.

See our full shrimp sourcing and quality standards for more on how KATUNA ships white shrimp from Ecuador.