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Mar 14, 2009 05:13 PM

What is "sashimi grade" fish?

So I was defrosting some ahi steaks that are going to get seared up for dinner, and noticed that the package says "sashimi grade." But as far as I can figure out, there's no USDA or other grading system in place for fish.

I suppose if I had batches of tuna of wildly varying quality, I might label some "cat food grade" and other "sashimi grade" just to let people know which is the good stuff. But does this designation actually mean anything, or is it just marketing hype?

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  1. I believe it's pretty much marketing - but as you say, this doesn't mean it's not informative. For example, if the same supplier has sashimi and not-sashimi grade, then the sashimi grade is probably better.

    I believe for restaurants in the US, certain kinds of fish to be served raw has to be freezer-cured down to a certain temperature, to kill or weaken parasites. But as far as I know, this doesn't have anything to do with labeling on fish sold at retail.

    1. I would like to think that aside from having been chilled closer to zero kelvin than "the frozen dead guy" in Nederland, Colorado, that it would apply to the cut and trimming, so as not to include the fish eqivalent of silverskin, which is common with tuna.
      But in reality, I think the term is essentially meaningless.

      1 Reply
      1. re: Veggo

        veggo, i think the "silverskin theorem" is a good one, because who wants to admit some of the fresh tuna is "fresher" (sashimi grade) than the other fresh tuna.

        BUT here seems to be the right answer from fourunder that addresses this matter specifically, namely the freezing of the fish (also as nfo alludes):

      2. I'm relatively new to Hawaii, but to the best of my limited knowledge, sashimi grade ahi/tuna means a piece, either fresh or freshly thawed, that is fatter than average and that you will enjoy eating raw, whether or not the skin will need to be removed before you eat it. Lesser tuna is marinated and served raw as different flavors of poke.

        3 Replies
        1. re: Joebob

          My husband is a buyer at Tsukiji Market and in Japan "sashimi grade" means that it can be safely eaten raw. He has sold Tsukiji fish in the states and I don't think that there were any USDA standards regarding the term "sashimi grade". As a retailer, he and the other fishmongers just had to be sure to tell the customer if they had to cook the fish or not.

          For example, a piece of fish could be considered "sashimi grade" for a few days, but after some point, the fish is still edible but needs to be cooked. In Japan, they just slap on a sticker that says "for cooking" vs. the "sashimi grade" sticker.

          In the end, your fishmonger needs to tell you if at the time of purchase it is sashimi grade or not. However, at that point you should consume it immediately, not freeze it with the intention of eating it in the future.

          I know that some Whole Foods Market on the east coast sells "super-frozen" tuna, salmon and hamachi that you can defrost at home that is sashimi grade. The same product is sold to high end sushi restaurants in the city.

          The photo is a sashimi dinner we had at home. All the seafood came from Tsukiji.

          1. re: Yukari

            yukari, that plate of sashimi is a work of beauty!

            1. re: Yukari

              holy shmoly...that is beautiful...yukari, can you enlighten me as to how to cut and prepare in that way? tonight, my wife and i are going to have a super-frozen salmon from whole foods that i bought yesterday. i am defrosting it in the fridge right now (although that is not what it says to do) - is that OK?

          2. Around here, I take the term to ostensibly mean that the fish can safely be eaten raw - as in it's been held for at least 48 hours at below-zero temps to kill any possible parasites.

            It should NOT be just "marketing hype".

            45 Replies
            1. re: Breezychow

              Whether you think it should or shouldn't, it simply *is* hype. There is no standard for grading.

              1. re: Breezychow

                Well, since this thread has been revived...

                From a safety standpoint, there's no need to freeze tuna to kill parasites. That's much more of a concern with freshwater and anadromous species.

                As far as quality goes, the ahi that inspired the original question almost two years ago was TERRIBLE. Long on connective tissue and short on flavor. If I were served that fish as sashimi, I wouldn't just reject the dish, but would walk out of the restaurant.

                So regardless of what "sashimi grade" **should** mean, or what we'd like it to mean, or what we're told it means, the fact of the matter is that it means nothing at all.

                1. re: alanbarnes

                  Yeah, I think "sashimi/sushi grade" means it's gonna cost you an extra buck or two per pound.

                  1. re: ricepad

                    I notice differences between sashimi quality (grade, if you'd like) and tuna not labeled as such.

                  2. re: alanbarnes

                    My rule of thumb is that when salt water fish is frozen it is an immediate deduct of 2 points on a 10 scale, in some cases more. Tuna included. Hamachi is a tough one, as yellowtail is a warm water fish, and sea-to-table is almost impossible without freezing.
                    Only fresh water fish must be frozen, to avoid parasite risk, including but not limited to salmon and unagi (which additionally is almost always cooked).
                    And my comment above from 2 years ago that "sashimi grade" is without meaning is still the case, and I'll add angus beef as another worthless piece of marketing jargon.

                    1. re: Veggo

                      Where do you find tuna for sushi that hasn't been frozen?

                      Angus is a breed of cattle. CAB is a brand with a specific set of standards. If you don't care for the standards or don't feel they add anything, then I suppose it's meaningless.

                      1. re: tommy

                        Fresh tuna - from Mazatlan to the Nicoya peninsula in Costa Rica has been a real treat for me, where pelagic blue water fishing is a day trip. I learned to bring my own wasabi and soy sauce.
                        Also on the central Florida gulf where I am now, some of the boats keep their tuna on ice if they will dock within one or two days (most are out for 5-6 days because of fuel and time to reach blue water in the shallow gulf). I used to have a fish monger who called me when he had a fresh one and I would leap at the opportunity. It is scarlet gelatinous ambrosia.

                        1. re: Veggo

                          Ditto with the Hawai'ian commercial fleet. Handliners bring in tons of yellowfin on short trips out of Kona. For a few days, it's far more cost-effective to just ice the carcasses. And fresh tuna is readily available anyplace that sells fish.

                          1. re: Veggo

                            I've never had such a treat, but would you say there's a big difference between this fish and what one might get at Sushi Yasuda, Nobu, or Morimoto?

                            I think it's a rule that fish sold in the US has to be frozen. If the fresh stuff is that much different I'd be surprised if there weren't more places where it was accessible, on the DL of course.

                            1. re: tommy

                              Your itamae is responsible for the freshness of what you are served, regardless of whether or not is has previously been frozen - whatever it takes. I have not had the privilege of dining in your benchmark locations so I can't compare. I expect that in nice places you are eating more fresh, never frozen than you suspect. The hurdles and expenses of transportation are invisible to the consumer but real to the establishment, and the level of quality they want to offer. Check out to begin to appreciate the magnitude of the task from the source.
                              I think it would be an interesting and fair topic of discussion with your chef, learning what is available fresh and what is all but impossible in a matter of fact way, and how the chef feels about the difference.

                              1. re: Veggo

                                But my understanding is that all tuna is previously frozen. On the boat.

                                If you haven't had sushi at top restaurants (and I assume you have), how can you deduct points for fish that has been previously frozen? Unless your understanding is that tuna at top places in the US has not been previously frozen.

                                1. re: tommy

                                  Your understanding is incorrect. Not all tuna is frozen on the boat.

                                  That said, I disagree with Veggo's premise that freezing tuna has a significant adverse impact on its flavor or texture. IMO fish that's flash-frozen and properly thawed is (nearly?) indistinguishable from fresh. And I know that some of the best sushi places in the country have specially-designed freezers they use to keep the frozen fish at near-cryogenic temperatures.

                                  But there are a few itamae who focus on seasonality and refuse to serve any fish that has been frozen. There's something to be said for that approach, too. For me the appeal isn't that non-frozen fish is inherently superior, it's the chef's desire to serve things at the height of their tastiness. That's bound to lead to good results.

                                  1. re: alanbarnes

                                    I see that tuna species are an exception from the FDA regulations as I understand them:

                                    "3-402.11 Parasite Destruction.*
                                    (A) Except as specified in ¶ (B) of this section, before service or sale in ready-to-eat form, raw, raw-marinated, partially cooked, or marinated-partially cooked fish other than molluscan shellfish shall be frozen throughout to a temperature of:
                                    (1) -20°C (-4°F) or below for 168 hours (7 days) in a freezer; or
                                    (2) -35°C (-31°F) or below for 15 hours in a blast freezer.
                                    (B) If the fish are tuna of the species Thunnus alalunga, Thunnus albacares (Yellowfin tuna), Thunnus atlanticus, Thunnus maccoyii (Bluefin tuna, Southern), Thunnus obesus (Bigeye tuna), or Thunnus thynnus (Bluefin tuna, Northern), the fish may be served or sold in a raw, raw-marinated, or partially cooked ready-to-eat form without freezing as specified under ¶ (A) of this section."


                                    I won't pretend to understand the FDA's regulations on frozen fish served as sushi to be consumed raw, but it does come as a surprise that some have never heard of such a thing. Unless the issue revolves simply around tuna species, but the deduction of points included all salt water fish.

                                    I'm also not convinced that never-flash-frozen tuna is inherently better than flash frozen fish, like alanbarnes, or, that there is much of a compromise; the challenge and realites of getting a fresh (not as in "never flash frozen"), quality, product to the consumer likely trumps the desire to serve never flash frozen tuna.

                                    Also interesting:

                                    I can just see someone asking a restaurant if their fish is "fresh" or "frozen". Of course the answer will be "fresh, never frozen," regardless of the reality. I suspect some top restaurants are serving flash frozen sushi, and the average person, or even the above average person, wouldn't know the difference.

                                    Regardless, when I have the opportunity, I'll definitely try never-flash-frozen tuna. I wasn't aware it existed until tonight's googling. If I can't find it, I'll stick with whatever is being served at Nobu and Yasuda.

                                    1. re: tommy

                                      And respectfully to Alan, I would bet my ranchette that I could distinguish between previously frozen and same-day tuna catch in a blind test.
                                      There are clear advantages to going to the source for some foods. And sometimes that is the only way you can enjoy the best. It is half the reason I still travel.
                                      I am not the expert on the subject that you and Alan are, but I carry wasabi and soy sauce in my zip-lock bag of 3 ounce toiletries as I toil through airports. I like eatin' good, and I know good, because I'm bad.

                                      1. re: Veggo

                                        But I don't even like same-day-caught tuna. Yes, it's outstanding for a very short time (an hour? maybe longer) after the fish bleeds out, but then it starts to get kind of tough. Flavor and texture are better the second day, and the third day better yet. Depending on the fish and how it's stored, it peaks sometime between Day 3 and Day 5.

                                        The changes that happen over the course of a few days are dramatic. And I have no doubt that flash-frozen fish will behave differently over that time. But trying to differentiate the changes caused by aging from those caused by freezing is beyond my ken. And never mind differences between tuna species or individuals within a species - I'm talking about meat from a single fish.

                                        So I'm all for gunwale sashimi. But a trick that a commercial skipper taught me is that if you want to eat tuna for dinner on the day it's caught, you should pop it in the freezer for the afternoon to **improve** its quality.

                                  2. re: tommy

                                    I think you posted while I did an edit to suggest it is a good question for your itamae. Sure, I have had good sushi, a great distance from the sea sometimes. I'm not aware of any "rule" that tuna *must* be frozen. If I'm dealing with lawbreakers, I'm living, happy proof that the rule is without merit. The fishmonger I mentioned above who would call when he had a fresh one was not even here in Florida, but in jfood's neck of the woods when I lived in New Canaan, CT.

                          2. re: Veggo

                            Veggo: I beg to differ. While the term "sashimi grade" is very imprecise, tuna is in fact quality-graded in the marketplace. Fishermen and charter operators in Hawai'i know that ahi that are hooked, landed, bled, iced and brought to market in the shortest possible time command much higher prices. Good fishmongers can discern subtle differences other than smell (e.g., the eye clarity), and they pay less for any fish that is "off" in any direction. In the better fish markets in Hawai'i, it is not uncommon to find FOUR different grades tagged "sashimi", and another 2 of perfectly edible, delicious, fresh cooking fish. And it is not the presence of bloodline, either.

                            Line-caught tuna can fight hard, and in doing so, they generate heat. The fisherman therefore wants the fish landed ASAP, because the heat degrades the quality. They want the blood out wikiwiki, and the fish covered in masses of crushed ice. If they quickly land, bleed and ice an especially nice, large fish, they may race back to port because they know that one such fish might be worth more than three more fish if they wait and the quality isn't there.

                            Now then, I am no sushi expert, but there is a difference in clarity and texture between sashimi/non. I learned this lesson the hard way, because I foolishly kept buying the best sashimi grade ahi for grilling, and it was a big waste of money--cooked, it's pretty much all the same. BUT, if you're going to flash sear and serve it up center-raw, you can see a difference. Sliced thin by a skilled sushi chef, the best ahi is translucent--most of the rest is not.

                            1. re: Veggo

                              "Veggo" I agree with what you said 100%....there is a huge difference between fresh and frozen...tuna/fish...anything...
                              I had a chance to spend some time in Pago Pago (American Samoa) and only then I realized what I was missing when it comes to "fresh" (as in less than 12 hrs.) tuna....

                              Couple of other comments: (1) "aging" fish to be eaten raw is a does not get "better", (2) almost all tuna coughtt for the "raw" market is blast frozen and not flash frozen and that's if the fishing vessel is big enough to have blast freezing equipment. Most tuna we get in the US is probably 5-8 days out of the water BEFORE it is frozen.

                              1. re: Pollo

                                We chickens of a feather shall stick together. "aging" a fresh caught tuna? NOT!
                                Foregive them, for what they don't know but can learn here.

                                1. re: Pollo

                                  >>""aging" fish to be eaten raw is a does not get "better""<<

                                  I'll be sure to tell my favorite tuna boat captain he's wrong the next time I see him. Oh, and the itamae at my local sushi place, too. But what do they know, anyway?

                                  But never mind training or industry experience. Anybody with a palate who's actually eaten sashimi from the same fresh-caught tuna loin over a period of time knows that the flavor and texture improve over the first few days.

                                  1. re: alanbarnes

                                    In my experiences, the deliciousness of tuna and billfish, wahoo, dorado, permit, oysters, et al, while still on the open water, is pretty good then and there, and four days later I'll likely be somewhere else up the sea or down the road.
                                    Y'all can enjoy the leftovers.

                                    1. re: alanbarnes

                                      We are talking about tuna....not lutefish or picked herring...but anyway...

                                      FYI - Samoans consider sashimi/poke made from tuna that is not fresh (as in caught that morning) to be garbage and will not eat it (they will eat it cooked/grilled). On two occasions when the see was rough and boats did no go out to fish I had to plead with a restaurant owner to make me poke from what was considered "old" fish (i.e. 2 days - refridgerated).

                                      1. re: Pollo

                                        Yes, we're talking about raw tuna. That's why I mentioned a **tuna** boat captain who was the first one to point out to me that the stuff is better on the third day than the first. When I talked to the classically-trained sushi chef at the place where I'm a regular, he agreed. And others on these boards who actually know a little bit about Japanese culinary traditions concur, too.

                                        But then again, everybody knows that the Japanese are completely clueless when it comes to preparing and serving raw fish. Go to any major metropolitan area and all the most highly-regarded sashimi places are owned and operated by Samoans.


                                        1. re: alanbarnes

                                          True what you said BUT Samoans don't eat sushi....they eat tuna (and few other species)...either sashimi style or as poke (or OKA) and they have been eating it (I am going to hesitate a "guess" here) longer than the Japanese.

                                          The argument that Japanese have the "monopoly" (i.e. are superior) on serving/preparing "raw" seafood is not true in my opinion. I had more interesting presentation/variety of "raw" seafood preparations in South America than in Japan...but that's another story....

                                          1. re: alanbarnes

                                            Do you happen to know how this varies from species to species? I have no practical reason to know, but am finding the idea fascinating now that I'm thinking about it. Rigor mortis in humans averages about 3 days, but can be gone in less than a day if the body is sitting in the heat, and can persist for over a week if the body is in a refrigerated morgue. Other mammals can go through the whole rigor mortis cycle in a matter or hours, and others can take a week even in warm conditions.

                                            There are a number of competing schools of thought on dealing with this in the slaughter industry, and I'm wondering if the same is true for the fishing industry. I guess I've always pictured sushi quality fish being iced immediately on capture, but, with beef, immediate refrigeration after slaughter will cause tissue stiffening that will not dissipate without cooking, unless preventive measures are taken.

                                            Are fishermen, or sushi chefs, trained to handle each type of fish differently, such as the optimal amount of time for aging by species? I guess to an extent they would be able to tell when the tissue has relaxed enough though a simple touch test, but it seems like they would have to know that if I buy this sweetfish today it will be ready to serve in two days, and if I buy this tuna today it will be ready in three.

                                            1. re: gadfly

                                              My experience with the fish I've caught myself is that rigor is gone within a day, even on ice. I haven't paid enough attention to notice whether it varies by species; my interest is less academic and more oriented toward when they're going to lay flat enough to be filleted.

                                              For the best quality big tuna, standard practice is to destroy the brain with a spike, run a stiff wire or piece of monofilament down the spinal canal, and open up cuts behind the pectoral fins so that the fish will bleed out. Once the fish is bled, it's gilled and gutted, the cavity filled with crushed ice, and the carcass packed in ice.

                                              Most other fish aren't handled so carefully. With salmon, for example, it's whack 'em and stack 'em - knock the fish on top of the head and pitch it in the chill chest. But AFAIK it's always advisable to immediately get any fish on ice.

                                              1. re: alanbarnes

                                                Interesting, thanks. Maybe you've already answered this and I'm just not seeing it, but if rigor mortis is gone within a day, then what is gained from the 2nd and 3rd day?

                                                I don't know how this fits in, but before we had quality sushi in the Northeast (and still at many of the sushi bars, since most around these parts still aren't very good) just about every piece of tuna I was served was still in rigor mortis. I was never sure if this was because it was too fresh, or if it was what meatpackers call cold shortening, which is the irreversible tissue stiffening due to cold storage I refer to above.

                                                1. re: alanbarnes

                                                  alanbarnes: "...destroy the brain with a spike, run a stiff wire or piece of monofilament down the spinal canal..."

                                                  This is the ike jime technique, which was discussed and linked to at another site here:

                                                  The idea seems to be to "make the fish forget it's dead", thereby avoiding rigor mortis. I'm not sure this technique would be preferable to simply letting the rigor pass naturally, but the fish can be brought to shore, marketed and served faster. Maybe a good idea if you're a restauranteur who charges big $ for having a live tank of little fishies.

                                                  I'm with you on the sticking and bleeding thing.

                                                  1. re: kaleokahu

                                                    The central nervous system is not involved in rigor mortis. There are ways to avoid it, but they involve direct action on the muscle tissue with anything from electricity to a variety of chemicals. No direct physical action can stop the chemical processes behind rigor mortis.

                                                    What destroying the central nervous system would accomplish would be twofold. It would stop muscle flexing so that when rigor mortis did set in, the fish was lying flat. It would also cause the rigor mortis to set in faster, and thus pass faster, by immediately stopping all cardio-pulmonary processes. Well, maybe that second part doesn't apply to fish, but it works with land animals. I'm sure there are also other reasons this is done that I can't divine.

                                                    And you don't need to worry about rigor mortis with freshly killed meat, such as that from a restaurant with a tank of live fish. The fastest I can think of rigor mortis setting in is with small gamebirds, and that's still over an hour. I don't think it's possible, without outside intervention, for the necessary chemical processes to occur in under an hour.

                                                    1. re: gadfly

                                                      AFAIK the point of destroying the central nervous isn't to prevent rigor, it's to minimize damage to the fish. Tuna do not take kindly to being removed from the water and will flop around violently while bleeding out, which can bruise the flesh. Stunning helps, but running a bit of mono down the spinal canal completely immobilizes the fish and prevents bruising.

                                                      Spiking the brain also eliminates any further adrenaline release, although I'm not sure how much effect it's going to have. Given that you've just fought the fish to the boat, gaffed it, and hauled it over the gunwale, adrenaline levels may be as high as they're going to get.

                                                      1. re: alanbarnes

                                                        Ah, I hadn't thought about bruising, good point.

                                                        My knowledge of perciforme anatomical functions is woefully bad to even speculate on the adrenaline issue. With many chordates, the brain isn't necessary to stimulate adrenaline production. With others, the brain is a vital element to stimulating this process. With others still, severing the brain would not stop adrenaline production, but destroying the spinal chord would.

                                                        In any of these types, you can never have adrenaline levels at some maximum level. Adrenaline receptors and other adrenaline receptive tissues (and in many animals, nearly all body tissues are adrenaline receptive) use up and cycle out adrenaline very quickly. Continuous production is required to keep the adrenaline response going, so if destroying the central nervous system of the tuna stops adrenaline production, then all the more reason to do so. Though I'll admit that I'm not especially sure how the adrenaline levels effect the end product.

                                                      2. re: gadfly

                                                        gadfly: "The central nervous system is not involved in rigor mortis." "[Y]ou don't need to worry about rigor mortis with freshly killed meat, such as that from a restaurant with a tank of live fish."

                                                        alanbarnes: "...the point of destroying the central nervous isn't to prevent rigor"

                                                        If the Cooks Issues article linked here can be believed, I think the CNS IS involved in rigor mortis, and there is a definite culinary textural betterment. At least Dave Arnold and the Japanese Fisheries Science Journal believe so (See, the 4 scientific studies cited at the end of the linked article).

                                                        This is above my pay grade, but it has to do with the CNS cellular function of the spinal cord (which varies between species). Without ike jime, the fish "knows it's dead" and the residual function of the spinal cord--even after severing the head--will induce a harder rigor in the flesh.

                                                        1. re: kaleokahu

                                                          Great reading - thanks for the link. There's more interesting discussion here:

                                                          1. re: alanbarnes

                                                            alanbarnes: Aha! Yes, this was the article i remembered, and the cells are CPGs (Central Pattern Generators). Arnold explains it better than I can:

                                                            "So then, when you destroy the spinal cord, you destroy the swim reflex, which helps reduce ATP loss, delaying and softening rigor, increasing the quality of the fish."

                                                            But as he goes on to say, that may not be ALL that's at work.

                                                          2. re: kaleokahu

                                                            I'll take a look at their reference articles, but the information on the cooking issues site is very clearly conflating normal muscle contraction with rigor mortis. There is essentially no relationship between the two.

                                                            Think of it this way. If you cut your leg off, it is no longer connected to your central nervous system. Yet, it will still undergo the exact same rigor mortis process that you whole body would if you were to die. Similarly, filleting a fish immediately on catching it will cut the fillets off from the central nervous system, but it will not stop the rigor mortis process.

                                                            I'm sure that ike jime technique has an effect, even a very substantial effect, on the textural end result. That does not mean it is connected to rigor mortis, which is a specific process mostly unrelated to what cooking issues is addressing.

                                                            1. re: gadfly

                                                              gadfly: "it will not stop the rigor mortis process."

                                                              Again, not my area of expertise, but here's another source (internal citations unfortunately omitted) that seems to say ike jime delays rigor mortis and improves table quality.:

                                                              If, indeed, the intact spinal cord causes even a headless fish to "want to swim" (I read somewhere--I thought in a CooksIssues article--that Arnold talked with a neuro buddy of his who ID'd the specific cell type that causes this action), wouldn't the muscular ATP be depleted faster without ike jime and rigor's onset be faster if not stronger? Wouldn't THAT speed the decomposition enzyme process, and increase the likelihood of drip loss and mushier flesh?

                                                              1. re: kaleokahu

                                                                To put it simply, no, but that's serious hair splitting given that the point of ike jime is to produce a superior textural result. It's clear from the evidence given that it does this. Why and how it does this, regardless of its relationship to rigor mortis.

                                                                The cooking issues analysis in both cases shows a lack of understanding of the biochemical processes which lead to rigor mortis, and ATP's role in these. The most relevant of the sources they cite on the issue of ATP is the 1996 Masahi Ando article. Now, as I noted in a previous post, the onset of rigor mortis can be hastened, and the converse is also true. So, their claim that this process delays the onset of rigor mortis is perfectly reasonable. This is a function of ATP, with onset coming faster as ATP is more quickly depleted, or slower as ATP is more slowly depleted.

                                                                What they have failed to do is clearly demonstrate that the ike jime process is slowing the depletion of ATP. There are two primary factors to keep in mind here. The first is oxygen depletion. Cutting off the supply of oxygen to cells by destroying the central nervous system and bleeding the animal out will immediately rob the cells of the animal of their ability to produce ATP. ATP production does not normally cease immediately at the instant of "death" (roughly corresponding to what we would call brain death, which is not related to the popular notion of being "brain dead", ie a persistent vegetative state, but means really and truly irreversibly dead). ATP production stops at what is called cellular death, which, depending on the organism, can come anywhere from seconds to hours after brain death, or even never.

                                                                Ike jime will substantially hasten cellular death, therefore substantially reducing available ATP. Of course, it will also stop reflexive muscle action, substantially reducing the rate of consumption of ATP. So, the question becomes, which of these two forces is greater. The research presented provides no satisfactory answer to this question. Honestly, I very much doubt any research can provide a satisfactory answer to this question, not just because this is a notoriously difficult thing to measure, but because the circumstances are going to vary enough each time that a hard and fast rule probably can't be established. But, let's continue in our examination as if it can, and ike jime will absolutely have a net result of more ATP. Rigor mortis will definitely set in more slowly, in this case.

                                                                Where does this leave us? Not where these articles want us to be. Think of it this way. The forces causing rigor mortis are a river that is being held back by a concrete dam, the dam being life. ATP is a damn slightly upriver from this constructed out of sugar cubes. Death is the destruction of the concrete dam, and, in order to make the metaphor work, let's pretend there is no surge of water to smash the sugar cube dam. The sugar dissolving into the water is the only force that is going to destroy our sugar cube dam. If you have more sugar cubes, more ATP, it will take longer for the river to break through, for rigor mortis to set in. But, whether you have a giant sugar cube dam or a rather small one, you end up with the same result: an uninterrupted river, or, rigor mortis. The ATP will eventually be entirely depleted, causing the cycle of chemical reactions that causes muscle flexing to occur to begin, but not run its course, so that the muscle does not relax.

                                                                The analysis of the samples in the 1996 Masahi Ando study suggests that based on the evidence collected, some of the fish had more or less severe rigor mortis, or that it lasted more or less time. This isn't really how rigor mortis works at all. The data is not presented in a manner that I find to be completely sound (but that's nitpicking) and the methodology really just isn't great (and that's not nitpicking at all). Still, from the data presented, it's fairly clear to me that what's happening is that the rigor mortis is simply setting in to individual cells are very different rates. Carcasses, after all, do not suffer from rigor mortis. Individual cells do.

                                                                This differing rate of rigor mortis between individual cells is not at all uncommon in the case of violent death, and is more or less a given with rapid asphyxiation. If you touch a muscle with less than half of its cells in rigor mortis, you probably won't think it is in rigor mortis at all. But once a cell dies, unless it is electrically or chemically altered by substantial outside forces, it is going to go through rigor mortis. How much ATP it had at the time of death will not effect how long it is in rigor mortis. Cellular death is cellular death. There's no other way to paint that picture.

                                                                And really, what would be the point of delaying or weakening rigor mortis exactly? None of those suggesting this ATP explanation make much of an attempt at explaining this. Rigor mortis does not cause any kind of scarring. It leaves behind no traces (or at least, none that are detectable without serious lab equipment). Though I've never worked on any matters dealing with fish slaughter, I've spent a whole lot more time than I would have wanted to over the last two and half decades focused on turning land animals into consumable meat products. And, I can tell you, with those, you want rigor mortis to come on as quickly as possible.

                                                                This is, as you note, related to the enzymic breakdown of the muscle tissue. However, this doesn't function the way you're thinking. The decomposition starts before the body is cold, so to speak. It's beginning is unrelated to the onset of rigor mortis, and the speed at which the decomposition occurs is similarly unaffected by ATP or rigor mortis. Temperature is the biggest factor in how fast this happens. And the faster rigor mortis set in, the faster those chemical bonds that cause it are created, the sooner the enzymic reactions that break them down can get to work. With meat, this means the faster rigor mortis sets in, the fresher the meat will be when it has passed. I would have to assume the same is true of fish, but I'm not 100% confident in that assumption. Still, delaying the onset of rigor mortis is definitely not going to create for less decomposed flesh. Not in any scenario with any animal.

                                                                But, again, all of that basically just amounts to hair splitting and nitpicking. Ike jime is clearly doing what they want it to do. That is, it's resulting in a better texture for the fish. The explanations posited might not hold water, but sometimes you've just got to say to hell with the science and do what works. I hope they figure out the science behind it eventually, and I'm fairly sure they will They're definitely not there yet, based on what I'm seeing, however. And I'm still way more interested in knowing why the three day aging makes for better tuna.

                                                                1. re: gadfly

                                                                  gadfly: Thanks for the interesting analysis. You are obviously very knowledgeable. And thanks especially for the recognition that sometimes explaining WHY something is happening can be less important than accepting the fact that it IS happening. We also have the issue here of what differences there are in "rigor" between mammals and fish.

                                                                  "And really, what would be the point of delaying or weakening rigor mortis exactly?"

                                                                  Whether or not it's explainable in terms of ATP depletion, it seems common sense to me that, ceteris paribus, the longer the fish struggles and has muscular contractions, the lower the culinary grade it will be. Isn't this analogous to the old (and wrong) European theory that a beef with it's "blood up" because of being hounded will be better? And isn't it also why the best graded tuna, again ceteris paribus, is that which is landed and bled out the fastest and with the least struggle? Does the production of lactic acid stop at the instant of brain death?

                                                                  Now then, I think I read somewhere that ATP is required not only to contract muscles, but also to RELAX them. If ike jime conserves ATP by preventing the CPGs from continuing to reflexively contract muscle, isn't it more likely that all the tissue will be relaxed sooner (and perhaps genrerate less lactic acid or other byproducts)? And isn't ATP stored in the muscle cells themselves?

                                                                  "Honestly, I very much doubt any research can provide a satisfactory answer to this question, not just because this is a notoriously difficult thing to measure, but because the circumstances are going to vary enough each time that a hard and fast rule probably can't be established." LOL, I'm envisioning a labful of Japanese seafood biologists giving Bigeye tuna IV infusions of d-Ribose pre-and post-workout, pre- and post-kill to try to find explanations.

                                                                  Hey, thanks for the education.

                                                  2. re: alanbarnes

                                                    Cant speak to the "aging process" for different species, but this has been told to me by more than one sushi chef, including Yasuda. Not sure about tuna, but some fish have little or very mild flavor if served right away.

                                                    1. re: AdamD

                                                      Are we not confusing "aging process" with "quick kill and bleed"???....the two are not interchangeable.

                                                  3. re: Pollo

                                                    Pollo: LOL And other Polynesians like to throw their fish on their roof for a couple of days before cooking, a la a high-aged duck or pheasant. Certainly different, hardly kapu.

                                                    1. re: kaleokahu

                                                      The south pacific precursor to pescatarian sous vide...?
                                                      Nah. Dead fish get deader, and the gulls would laugh at you.

                                                        1. re: kaleokahu

                                                          I don't know. The truth is in the heavens.

                                                          1. re: Veggo

                                                            Veggo: The truth may be in ra'i, but the noanoa is on the roof.

                                        2. As others have mentioned, I suspect sashimi grade just means previously frozen therefore OK to serve raw, but since ahi doesn't need to be frozen it's meaningless. Maybe it's just a label they automatically put on frozen fish. The times I bought "sashimi" fish here in Canada it was nicely cut into long blocks of the appropriate size that you just needed to slice up, not steak-shaped, very convenient.

                                          2 Replies
                                          1. re: hsk

                                            Similarly, hockey pucks are frozen to improve their performance. I don't want to eat one of those, either.

                                            1. re: hsk

                                              but since ahi doesn't need to be frozen it's meaningless...

                                              I know restaurants that were forced to discontinue offering Sushi/Sashimi by the local health departments because they did not purchase their fish from an approved fish supplier that specializes and has documentation of their fish products origins and processing......It's not meaningless to an ethical restaurant or food service operator. Even frozen/fresh fish is supposed to go through inspection before it could be sold in markets.