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Leading Health Letter Asks Us About Gray Matter
4/6/2009
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Vital Choice founder Randy Hartnell answers queries concerning the grayish under-skin layer in wild salmon

Recently, we received a series of queries from a leading university’s high-circulation health letter.

They were answered by Randy Hartnell, Vital Choice founder and former Alaska fisherman.

We often get similar questions, so it seemed smart to offer an edited version of the exchange for our readers’ edification.

The writer’s questions are followed by Randy’s answers:

Question: What is the grayish part closest to the skin in salmon? Is it okay to eat, or should it be trimmed away?

Randy's answer: This brown or grayish meat is a natural layer of fat that lies between the skin and flesh in salmon and other oily fish.

It’s rich in healthy omega-3s and perfectly fine and tasty to eat if the fish has been well cared for.

The gray layer’s mostly unsaturated fats are relatively quick to oxidize (turn rancid), and may have an unpleasant ‘fishy’ smell if exposed to the air too long.

This is why the freshest tasting fish is often that which is flash frozen and vacuum sealed immediately after harvest and remains that way until shortly before preparation.

This fatty layer tends to be thicker along the midlines of the fishes’ sides, where a strip of it may remain after the skinning process.

Removal of the entire fat layer (a process called “deep skinning”) inevitably removes some of the richest flesh, so we strive for a happy medium that removes most, but not all of the dark fat layer.

Question: Is the gray part higher in fat than the skin?

Randy's answer: The gray layer is the fattiest part of salmon, and the skin contains relatively little by comparison.

Question: What causes the outer layer to be gray? Does it have to do with what the fish ate? Or how much it swam in its life?

Randy's answer: Depending upon the particular specie, the flesh of nearly all wild salmon is somewhere between pink and deep reddish-orange.

The exception would be a small percentage of wild king salmon (about 10%) that carry a genetic deviation that seems to alter the way they process carotenoids. These are known as “white” or “ivory” king salmon. (White king is delicious, nutritious, and sought out by fishermen and salmon-savvy Pacific Northwest shoppers.)

Question: Is there a difference in the amount of gray part between farmed and wild salmon? Does farmed salmon have less?

Randy's answer: Farmed salmon are well known to have up to twice as much fat as wild salmon, a higher percentage of which is saturated, and, as you point out in the article, contains more pro-inflammatory omega-6 than anti-inflammatory omega-3s.

As for how much of it resides in the under-skin layer, my guess is that it is probably is thicker in farmed salmon than wild, since the amount of fat in their flesh is markedly higher overall, as signaled by the broad white lines of fat evident in farmed salmon flesh.

This is not surprising given the dramatic difference in the way each feeds and spends their respective lives: wild salmon live on a 100% natural diet and are the “athletes” of the salmon realm, whereas you might say farmed salmon are the junk food eating “couch potatoes”.

Question: Does it reflect the color that farmed salmon would be if they weren’t given carotenoids in their feed?

If so, does a fish with more gray mean it ate fewer carotenoids?

Randy's answer: The pinkish-reddish color of salmon flesh does come from dietary carotenoids. The flesh color of wild salmon varies according to the way the various species eat, and how individual members process the carotenoids … such as with ivory king salmon.

I think it’s safe to say that the intensity of color (or lack thereof) is generally related to the amount consumed. For example, you can have the same specie of wild salmon in one region of Alaska that manifests relatively pale pink flesh, versus those from other regions that are much more intense. This is likely related primarily (but possibly not exclusively) to dietary factors.

Question: On a personal note—do you eat the gray part? Or trim it away?

Randy's answer: I eat it, my wife trims it away. It’s mostly a cosmetic (versus flavor) issue.

Here’s an anecdote that you may find instructive: canned wild salmon is available in both “traditional” pack, with the skin, fat, and bones, and, increasingly, in a skinless & boneless version.

While many consumers initially prefer the latter, I’ve conducted countless side by side taste tests and almost invariably the traditional style is judged more flavorful/desirable.

This is because a great deal of the flavor (and nutritional value) originates from the fat and soft edible bones. In our experience, most people familiar with canned salmon prefer the traditional style, and on our website it outsells the skinless-boneless by a wide margin.

Question: Isn’t it usually trimmed away in smoked salmon? For aesthetic reasons? Do you eat the skin?

Randy's answer: Most smoked salmon is sold with the skin on, and thus the fatty layer beneath it. When I serve smoked salmon I usually peel away the skin and cut or scrape off the gray fatty layer.

I do this is mainly for cosmetic purposes, but also to reduce the risk of oxidation and the fishy flavor that may accompany it if it’s not consumed immediately.

Regarding fish prepared in other ways, with the exception of canned salmon (sardines, mackerel, etc.), I usually I don’t eat the skin, but will on occasion, depending upon how it’s prepared.

Crispy, well-cooked skin is pretty low in fat, which gets driven out by the heat.

Question: Lastly, do you know if other fish have a similar gray layer?

Randy's answer: Most “oily” fish have it to some extent, although ivory-hued sablefish often has very little, despite being one of the richest, fattiest fish of all.

I hope this helps. Try eating a nice red piece with some gray layer. I find the fatty gray layer adds only extra lusciousness, and stronger, deeper, but not at all fishy flavor.

Let me know what you think!

Best regards,
Randy

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