Can you get parasitic worm infections from packaged Smoked Salmon?

September 23, 2014 8:47 PM

I'm a lover of seafood. So much so that I eat fish almost daily. Lately, I've been consuming a lot of smoked salmon -- the packaged ("ready-to-eat") kind that you find in the frozen food section of grocery stores. However, today as I was going through one package of smoked trout, I spotted several white dots buried in the flesh of several of the slices. These small white dots (approx. 1mm in diameter) were mostly concentrated on the edge of the trout slices, although there were a few white dots in the middle of the slices too.

Unfortunately, I ate most of the slices before I found out about the white dots. It grossed me out when I saw them, so I put the leftover bits in a plastic bag in the freezer and tried to induce vomiting. (I hate to throw food out, but if I get confirmation that the white dots are parasites, I'll certainly toss it.)

This is all "cold-smoked" fish, by the way. I'm wondering: what are these white dots? Parasitic larvae of infectious worms (e.g. Anisakis)? And if they potentially ARE parasitic larvae, can I be sure they are dead (and therefore non-infectious and safe to eat) from the commercial "cold-smoking" process?

I've always thought that the packaged, cold-smoked fish you buy from grocery stores were completely free from the risk of parasites, but now that I saw those white dots, I'm starting to doubt it.

Here is a link to a picture of the white dots.

posted by vanizorc to Food & Drink (15 answers total)

Meyers says that although the white spots in an infected salmon’s meat are unsightly, and can make the fish difficult to freeze, that the salminicola parasite can only live in a cold-blooded animal, and is harmless to humans and bears. - from an Alaskan community radio station
posted by GuyZero at 8:54 PM on September 23, 2014 [1 favorite]

I'm not so sure about the first link, when I google image search salminicola, the white spots appear to be much larger than the ones in your fish. Doing the same search for anisakis turns up results that look nothing like what you posted, and I also see that the infection is extremely rare.

I do see many suggestions that white spots on smoked salmon can be caused by fat globules being brought to the surface during the smoking process.
posted by treehorn+bunny at 9:06 PM on September 23, 2014 [5 favorites]

I should post the disclaimer that I don't recommend image searching anisakis for the weak of stomach.
posted by treehorn+bunny at 9:07 PM on September 23, 2014 [3 favorites]

Although cold-smoking isn't enough to kill some parasites (like fish tapeworm), ready-to-eat cold smoked salmon is processed with a variety of controls to reduce risk. I don't have any data but based on watching the Discovery Channel, I think most mass-produced smoked salmon is flash-frozen at sea and kept at -20F or lower until it arrives at the smoking plant (which will meet the seven-day requirement for -20F freezing; since the faster it's frozen the better the texture, they might even flash-freeze at -30F or below, which will kill parasites in 15 hours.) Regardless of which risk controls are used, although you might plausibly see parasites in your properly processed cold-smoked salmon (urgh), they are no longer capable of hurting you.

Recognizing that sometimes manufacturers make mistakes, I checked and there haven't been any recent recalls of cold-smoked salmon (the last one I found was a 2013 voluntary recall for the potential of Listeria).

(I know that freezing things faster maintains their texture better from personal experience in the lab and the kitchen. The faster you can get whatever through that 4-degree point, the smaller the ice crystals you'll get. For fish and meat, that means less mushiness on thawing.)
posted by gingerest at 9:27 PM on September 23, 2014 [2 favorites]

It seems most trout in the US is hot smoked, but salmon is still sometimes cold smoked. If you bought this at the grocery store and it's not a local specialty, it's probably hot smoked and farm raised. Or, If you bought this from a guy/lady with a shack/ smoking fridge/etcetera, talk to him/her directly.

I would suspect the white spots are yellow grub, the same spots I've been cutting out of the fish fillets I have caught since I was a child. Like it or not, all fish have some parasites, some are just more visible than others. Parasites are also seasonal so you may not see them next month or next season.

This link talks about yellow grub and confirms they are completely safe to ingest. http://www.seagrant.umn.edu/fisheries/parasites
posted by littlewater at 9:36 PM on September 23, 2014

Dammit, I have no idea how I got fixated on salmon instead of trout. Some of my response still holds, but forget the whole frozen-at-sea thing. Last recall of trout was in 2012 for potential Clostridium botulinum, and the relevant control might be lengthy high-concentration brining.
posted by gingerest at 9:54 PM on September 23, 2014

Response by poster: After some searching around, I think the white dots are the "Kudoa" parasite. This picture of Kudoa seems to match perfectly to the picture I linked in my OP: http://alexandramorton.typepad.com/.a/6a0120a56ab882970c017742c1f7f2970d-pi

@treehorn+bunny: I agree that Salminicola is unlikely because of the size difference of the dots. I also thought for a while that the white dots in my smoked trout may be fat globules, but after touching them with my fingers, they are firm to the touch and do not "disintegrate" like congealed fat would.

@gingerest: Let's hope that Smoked Fish is flash-frozen like Sashimi is! It's such a commonsensical protocol to reduce risk of infection. Until today, I always thought that packaged, cold-smoked fish was as "safe" to eat as canned fish (in terms of parasites), but now this idea is out the window. I'm just not confident that the "cold-smoking process" is enough to kill and render inert parasites...there seems to be such a lack of information regarding this specific question out on the internet. (By the way, I live in Canada, not the US, so the FDA regulation might be different for us.)

@littlewater: The smoked trout in question is most definitely cold-smoked, not hot-smoked. Interesting regarding "yellow grubs"...they look a lot bigger in Google pics, but accordingly they can also be tiny. Good that they can't infect humans, even if consumed raw.
posted by vanizorc at 10:16 PM on September 23, 2014

I feel like you don't know how this works.

- All trout is farmed (unless your friend catches you some) so OF COURSE parasites are a big big concern.

You should report this to the manufacturer ASAP.

Also think about contacting the store & provide the link to your pics.

- Cold smoking is a curing process, so it cooks nothing. By design, it does not ever get hot enough to kill bacteria, parasites, and the like.

Only the manufacturer can tell you if the fish is flash frozen before smoking. My guess is: nope on farmed fish, possibly yes on wild catch. You'll have to research individual brands by calling them or searching their websites.

This sucks and I'm really really sorry. OTOH, it is the reason I try not to eat farmed fish, but especially Trout.

Trout aquaculture really lends itself to these kinds of problems. Again, I'm sorry.
posted by jbenben at 10:36 PM on September 23, 2014 [1 favorite]

Dr. Google tells me the brining process coaxes some parasites out of the fish before hot or cold smoking. I don't think cold smoked fish is brined long enough to really accomplish much in terms of parasites. I'm certain the brine deals with at least some surface bacteria, tho.
posted by jbenben at 11:23 PM on September 23, 2014

Between your title and your question it's completely unclear if you ate salmon or trout. They are different types of fish.
posted by yohko at 11:43 PM on September 23, 2014 [1 favorite]

IANAD but kudoa does not appear to be a human pathogen, it just affects the quality of the salmon.
posted by en forme de poire at 1:47 AM on September 24, 2014

I eat a lot of fish too (whatever happens to be on sale) so reading this thread is making me a little... hesitant about my planned perch dinner. Is there a website that gives a solid, non-inflammatory or exaggerated overview of determining if store-bought fish is safe?
posted by rebent at 7:22 AM on September 24, 2014

I have no idea if you have parasites in your fish, but I prepare a lot of cold smoked fish and you and treehorn+bunny have misconnected a bit on the white substance that forms on the surface of smoked fish. It is actually coagulated protein (albumin), not fat, and you should not expect the blobs to "disintegrate like congealed fat." Their texture on smoked fish is firm, almost rubbery and these blogs are extremely common with smoked fish. It is especially suggestive of denatured protein when you say that it clusters on the edge of the fish -- it is caused by heating the fish too fast and it is much more common where the fish is thinnest. Given how very common this is and how very rare kudoa is, I think this is by far the more likely explanation.

FWIW, salmon is required to be flash frozen in all instances, including prior to cold smoking, which would kill any parasitic infection. I have no idea what the FDA standards are for trout.
posted by Lame_username at 7:40 AM on September 24, 2014 [7 favorites]

vanizorc: After some searching around, I think the white dots are the "Kudoa" parasite.

Sorry, but it's simply not possible to ID parasites by comparing pictures of dot-sized spots in meat. Not even if you were a biologist or food inspector, specializing in such matters - which you are not.

You really are beginning to sound like a hypochondriac. You've decided you have been exposed to [something], and as soon as we say, "No, it's not a risk," you switch to an even more certain diagnosis of [something else].

The meat is almost undoubtedly safe. If you doubt that at all, throw it out. If you've eaten it, you're almost undoubtedly safe. If you don't believe that 100%, schedule a doctor's appointment immediately.

Nothing else matters. Asking us just gives you the chance to feed your fears and doubts, which is satisfying in a perverse way, but not helpful.
posted by IAmBroom at 9:25 AM on September 24, 2014 [2 favorites]

Response by poster: @lame_username: Thanks for the heads up about the "coagulated protein" -- its common occurrence combined with (I'm assuming) the fact that all salmon, farmed or wild, is flash-frozen to kill off parasites prior to any kind of consumption is very comforting, to say the least.

@yohko: I should have clarified that; my question should have addressed packaged, cold-smoked "fish" in general rather than just smoked "Salmon". As for the particular package I was consuming, it was cold-smoked Trout.

@IAmBroom: Your derisive and condescending personal attack adds nothing to this conversation. So I ask a useful question such as this (which seemed to have very few straight-forward answers on the internet), and I'm suddenly a "hypochondriac"? Really? In case you haven't noticed, I asked my question because I want to know WHY consuming those white spots is -- or isn't -- a risk. I needed more than a non-answer like "The fish is safe to consume; now shut up." I wanted an explanation of *why* this is the case, which the other answers adequately addressed. Thanks for your concern, though.
posted by vanizorc at 4:02 PM on September 24, 2014