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Comment by Stratoscope | Hacker News Reader

Pop quiz!

Do you ever buy frozen vacuum-sealed fish? The kind where each piece is sealed in its own plastic pouch? It is convenient and delicious. To me it can taste fresher than some "fresh" fish. One reason is that the sealed pouch keeps oxygen out.

Have you wondered why it says "remove all packaging before defrosting"? And ignored that advice like I did for many years?

After all, the fish seems to defrost just fine in its original vacuum-sealed packaging, whether you defrost it in the refrigerator or in a cold water bath. And it is so convenient to leave it in the pouch while defrosting.

Well, there is a reason to take those instructions seriously. The vacuum-sealed package is an anerobic environment, just right for botulinum and listeria.

So unwrap the fish, let it have that little kiss of oxygen, and then rewrap it for defrosting.

https://www.google.com/search?q=remove+frozen+fish+from+pack...

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Is this really a risk in practice though? I can't find any cases of this actually happening on the CDC's botulism site: https://www.cdc.gov/botulism/surveillance.html

might become a risk if it lies around defrosted for many hours.

I am somewhat skeptical of this as well. It's not uncommon to hear of someone having eaten something "bad", but that can be the result of many pathogens and with regards to botulinum, the article gives a data point:

> In the UK, between 1990 and 2005, there were 5 reported cases affecting 6 people and causing 2 deaths, meaning that you were 15 times more likely to be hit by lightning.

That data is clearly only reporting very serious cases though, since one third of them died.

Food poisoning is much more common than lightning.

> Food poisoning is much more common than lightning.

I said as much. The question is whether botulism is more common than lightning.

Food poisoning is not uncommon, but can be caused by many pathogens, for example E. coli.

Given the fact that we have a common illness but very few confirmations of C. botulinum as the cause, the question stands whether this is really a risk in practice.

it's a risk for certain fish and if you defrost the fish in the fridge for days... but as it stands botulism is not a very common thing to worry about in modern society. there are about 200 poisonings per year in the us. a lot are junkies using shared and dirty needles... babies eating honey is another large one. maybe about 20-50 per year in the us is an adult getting food borne botulism.

in any event yes it is risky to defrost the fish in a vacuum sealed bag but only if you thaw it for a few days or more like that. 50F fridge is about 2 days and 45F fridge is a few more days before there is growth: https://www.riskyornot.co/episodes/34-thawing-frozen-fish-in...

Fwiw i just thaw it the day i use it in cold water for < 1hr and it's almost certainly fine to use that day.

If you put your sealed fish in cold tap water, it will thaw in less than 15 Minutes. 15 Minutes is not enough for the bacteria to produce these toxins.

Right, that was going to be my question. Wouldn't botulism etc need a certain amount of time to grow? Is any normal use case of defrosting in a microwave long enough for that to happen? Is there a safe zone of X minutes, and then an unsafe zone of Y minutes where it gets dangerous?

Fast defrosting in Microwave or sealed, in cold water, is at least better than some of the other suggestions, like poking the seal and slow defrosting over 24 hours in the fridge. In the fridge and without a seal, the effects of exposing fish to other bacteria are really difficult to control.

it takes days for the botulism to grow under a vacuum in your fridge depending on temp.(a proper fridge should be 35-40F but many are much higher than that. 50F takes 2 days or so to form)

https://www.riskyornot.co/episodes/34-thawing-frozen-fish-in...

I know - I was referring to other bacteria in your fridge (such as Listeria etc.)(not in your fridge particularly).

This is similar for red meat. Vacuum sealed at the source will keep it fresh longer.

Here is a great video on what color meat should be to be considered 'fresh' and how to handle it from there: https://youtu.be/82KT_nb26-4

The rest of the channel is great if you are at all into cooking.

Any people from developing countries reading this thread?

What are your thoughts when you hear Westerners talking about the danger of leaving a meat out of the fridge for a couple of hours and stuff like that?

As long as it’s not vacuum sealed, you can leave it on the counter all day. Even in the west we defrost meat this way :)

Ahhh... Don't tell the health department. :)

No "we" don't.

That is expressly against USDA guidelines that say meat left in the danger zone[1] for more than 2 hours should not be consumed.

I don't eat meat, but my husband does, and he defrosts his meat in the fridge.

[1] https://en.wikipedia.org/wiki/Danger_zone_(food_safety)

We are talking about leaving meat out of the fridge in a sealed anaerobic environment, which is quite different.

No thoughts about the fish, but I was recently very surprised to learn that some people exclude my country, Brazil, from “western” culture. Like you did opposing “developing” and “westerners”.

Aside from geographical position, I certainly feel closer in culture to North America and Europe than to Middle-East or East-Asia cultures.

Every time I hear a statement with ”in the western culture…” I always identify myself with it.

So what do you, in your western culture, do with meat?

My wife leaves meat out of the fridge for the practically the whole day...

There are western developing countries.

And those who live there and read HN probably never faced the issues you have in mind for "developing countries".

Huh? In Austrian supermarkets meat just lies in a cool counter and you ask the staff to cut you some pieces. Additionally, there would be some packed meat in a fridge. I think it's the same in most European countries, I guess?

I think it's weird how the US put offloads most of the responsibility for preventing diseases to the supply chain and buyer, and not closer to the source. Lack of refrigerated trucks and unreliable power supply means we cannot rely on temperature being kept below specific temperatures. As a result, the regulations, processing and packaging are all work in tandem for safe food these conditions,e.g. regulations on how animals are reared, transported slaughtered, pasteurization and vacuum packaging. As an example, there are multiple brands of milk that's shelf-stable for months at room temperature.

> What are your thoughts when you hear Westerners talking about the danger of leaving a meat out of the fridge for a couple of hours and stuff like that?

It's not any different from the anywhere in the world, you have to be careful about how you handle food, or you will have a bad time.

Okay, so in the past we've used a sous-vide recirculator set to 30°C to quickly defrost fish which had been vacuum sealed (dodged a bullet apparently). I looked into it and the temperature at which it is safe to hold food without risk of toxin production is 3°C and less.

What high-speed defrosting methods are there to replace this? is it okay to just open the fish for 30 minutes, re-seal it and then put it in the recirculator?

Really I'm just concerned about a reliable method of defrosting which doesn't take a week. Putting food from the freezer into the fridge has been a hit-and-miss endeavour sometimes taking up to a week.

Back when I used to work in hospitality, we'd defrost fish (both vac sealed and loose) in cold running water.

Defrosting vac sealed fish in cold water over 20 minutes and immediately cooking it carries roughly zero risk of botulism, for 2 reasons:

1. The optimal growth temperature for C. botulinum is between 20-45 C [1], exponentially dropping off outside that range. That's why improperly canned food is risky, as it's usually stored in that range for weeks or months.

2. The bacteria is slow growing and doesn't cause illness itself, it also can't grow in the acidic conditions of the adult human gut. Rather, it's the excreted toxin that's dangerous, which takes several days to form [2].

[1] https://www.publish.csiro.au/bi/pdf/bi9530178 (p.p. 182)

[2] https://journals.asm.org/doi/pdf/10.1128/aem.62.8.3069-3072.... (p.p. 3071)

>>I looked into it and the temperature at which it is safe to hold food without risk of toxin production is 3°C and less.

The what now? My fridge at home is uniformly at 4C, surely that can't be dangerous.

quickly defrosting like that is fine wrt botulism but i'm not sure it's great to do that for other bacteria. but you can also just quickly defrost it in a bowl of cool water and use it within a few hours.

I have wondered about this, but even if botulinum or listeria are present, won't they grow very slowly in the refrigerator? I would think that defrosting for 12 hours or so at refrigerator temperatures would still be fairly safe. Or is the quantity that can be dangerous so minute that it doesn't matter?

Perhaps its one of those things where “95% of the time you’ll be fine, but be careful if you do it 20 times, because botulism only needs to happen once.”

The fact that most people don't know to remove the plastic and yet there are virtually no reported cases of people being poisoned by wrapped fish suggests that the danger is remote. It probably helps that if you fish get to the point where the bactera become active again it tends to smell bad and discolour.

I think if the fish was consumed raw there would be a lot more cases. But the toxin is destroyed by cooking even if the spores do grow.

> be careful if you do it 20 times

Probably just a locution, but be careful with that idea about numbers:

The probability of remaining in a safe zone of 95% for 20 consecutive times is ~36%. It ( (1-(1/n))^n ) approximates to 1/e.

The number of tries to reduce that 95% to a 50% coin toss is 13. It is not fully intuitive. One will put his threshold wherever one may think appropriate, but. A chance of tenth, a hundredth, a thousandth etc. for ten, a hundred, thousand etc. times approximates to 63.2%.

...Maybe a locution like 'Maybe 9 out of 10 times you'll be fine, but be careful about doing it 7 times' could work well (as 6.931 approximates the risk to a coin toss).

So that explains the seven lives of cats, who 9 times out of 10 land on their feet. (Also, 85% of statistics are made up on the spot.)

NB: This failure of statistical logic also shows up in "100 year storm" statistics.

The actual measurement is "storm with a 1% likelihood of occurring in any one year". The odds of that storm occurring in a century is actually about 63%, and of occurring in any ten year period, about 10%.

Add to that the fact that the measurement is based on a storm of a given magnitude (usually total rainfall / precipitation, wind speed, storm surge, etc.) occurring, and small changes in the likelihood of such events can dramatically change the rate at which a storm of a given magnitude is observed. If you live in/near flood-prone areas, keep an eye on, e.g., changes in what are considered flood stages (say, as flood control structures are added or removed), or to likelihoods of events of a given precipitation level or stream height.

Yes, defrosting vacuum sealed fish _in the fridge_ is safe, also in the package, for the next day as well, but not beyond. Defrosting on the countertop (or on the heating) is not, for the reasons GP stated.

I cold smoke meat so I need to be especially careful about this. The good news is, even though the spores are very hardy and can survive boiling at sea level atmospheric pressure, the botulism toxin (i.e. the chemical produced by the germs that does the actual damage) is easy to destroy by cooking over 85 degrees C.

Are botulism spores found inside meat or just the surface? 85C in the center will overcook the meats I cook.

Not inside meat, no. I don't think it's a problem for run of the mill hot-smoking or BBQ. For cold-smoked stuff I don't dare eat it raw yet but use the meat in stews. Cold smoked pork ribs add a 3rd dimension to thick soups like pasta fagioli or split pea soup, while sausages are great fried. I don't know how to safely attempt a prosciutto or lox though :-)

cured lox is easy, it's just a salt and sugar brine (cold smoked is something entirely different). If the salinity and sugar are high enough basically nothing can grow. Salt on its own, sugar on its own don't worry very well.

I defrost my fish in the package by putting it in hot tap water.

You, sire, drastically reduced my chance of dying. Thank you very much.

Do not do that. Defrosting should be done slowly in the fridge. Or you can cook frozen food directly. But do not defrost at or about room temperature, this will breed bacteria like crazy.

Wouldn't the food need to warm up to room temperature before bacteria would breed like crazy? If you defrost it from frozen to cold-but-defrosted, shouldn't you be ok, even if the surrounding air is room temperature?

The bacteria on the surface of the meat will hit room temperature in a few minutes, long before the entire piece is thawed all the way through. So it gets an hour head start.

No, it will not. But it depends on the shape of the meat. So if you are not monitoring the surface temperature, go with cold water or the fridge.

By that logic no one could ever safely eat steak tartare, which obviously you can without any issue. There will be bacteria growing in the surface, but unless someone fucked up somewhere along the way, they won't be harmful.

The issue is the timing. If you defrost in the fridge, it will eventually reach ambient temperature, but that's still safe. If you defrost on the counter, it will briefly be cold-but-defrosted, but rapidly progress to room-temperature-petri-dish.

> If you defrost it from frozen to cold-but-defrosted, shouldn't you be ok, even if the surrounding air is room temperature

Yes, that's my point. If you defrost in the fridge it's ok. If you defrost at room temperature then it's dangerous.

It's not extremely dangerous. Many people do it every day and don't die. But it's better not to.

No, what I meant was, if you defrost it at room temperature, it will not instantly warm up to room temperature - it will slowly warm up. You're not forced to leave it on the counter until it reaches room temperature, you can choose to use it before that point (even though it is surrounded by room-temperature air). It's possible to have a less-than-room-temperature fish inside a room that is in room temperature.

defrosting under warm water takes about 5 minutes, if you cook it immediately it's perfectly safe

Very much depends on what you're defrosting. A piece of meat frozeon at -20C will not defrost in 5 minutes under warm water.

It mostly depends on how large (or rather how thick) the chunk is. If you're talking about wafer-thin slices of salmon, then it'll defrost in about 30 seconds in cold water, even if it was frozen at -20C. If you're talking about a whole large turkey, then it'll probably take more than a day.

eep, my girlfriend insists on leaving meat out on the counter top for most of the day to defrost. I mean it feels cold to the touch still when we're ready to cook, and everything is cooked thoroughly, and we've never gotten sick yet but. Still dubious.

Putting it in the fridge to defrost takes 24 hours or so though.

Put it in cold water in the fridge, it goes pretty fast that way. It has saved my bacon a few times (both literally and figuratively).

defrosting in cold tap water also works just fine. I noticed that this keeps the fibres and cells intact which is advantageous for frying afterwards as the filet won't fall apart so easily.

Put it in cold tap water in the fridge and it will also defrost much faster than in the air, while staying at a safe temperature the whole time and it also won't be partly cooked already.

> drastically

If it was that dangerous you'd have heard of dozens of deaths and it would have been banned a while ago. People don't read instructions

> just right for botulinum and listeria

But if it was frozen, wouldn't that kill off any bacteria? Then, as a sealed environment, there wouldn't be anything to grow, even if the environment is just right.

edit: ignore this comment, I just read how the spores are resistant to boiling/freezing...

Freezing doesn't kill bacteria. Reliably, anyway.

I think Douglas Baldwin's sous vide guide is a relevant aside to this discussion of pathogens on food.

https://douglasbaldwin.com/sous-vide.html

So basically, is sous-vide cooking is a very bad idea?

No. Because you are in pasteurized temperatures. Practically always on the outside of the protein. And there are usually no spores inside the muscles

Sous-vide relies on longer time durations instead of higher temperatures. In most cases, a longer time at a lower temperature is equivalent to a shorter time at a higher temperature in the reduction of pathogenic organisms [0]

[0]https://douglasbaldwin.com/sous-vide.html#Safety

> Do you ever buy frozen vacuum-sealed fish? The kind where each piece is sealed in its own plastic pouch? It is convenient and delicious. To me it can taste fresher than some "fresh" fish.

Eeew. No.

Call me old-fashioned but I believe in this thing called seasonality.

I only buy fish that is in season, not farmed, and that is genuinely fresh from reputable suppliers, not supermarket "fresh".

Nice clear bright eyes, clean gills and all that jazz.

There is no substitute for fresh fresh fish. Well, maybe one ... high-quality smoked fish.

>There is no substitute for fresh fresh fish. Well, maybe one ... high-quality smoked fish.

While I take a bit less of a strong stance on this, I definitely agree there's nothing like properly fresh fish. I used to think I didn't really like mackerel but the truth is that supermarket mackerel can be a bit nasty even off the fish counter, mackerel straight out of the sea and cooked right away is absolutely fantastic.

> I used to think I didn't really like mackerel but the truth is that supermarket mackerel can be a bit nasty even off the fish counter

Yes. Oily fish (e.g. mackerel) really doesn't keep well, as you say it has to be eaten as close to "straight out of the sea" as possible. Oily fish certainly is not well suited to supermarket supply chains.

For those in the Bay Area, the Hankook Korean supermarket in Sunnyvale always has good fresh mackerel.

http://www.hankooksupermarket.com/products.htm

Photographers have a saying: The best camera is the one you have with you.

I have a really nice camera with some excellent lenses, but my recent photos that I'm most proud of and enjoy the most were taken with my Galaxy Note 8, a several-year-old smartphone.

Of course the kind of fresh fish you're talking about is far superior to the Costco bag of sockeye salmon I have in the freezer. But sometimes, it's getting near dinner time, and I don't have time to go shopping and just want some fish. Under those circumstances, the frozen fish hits the spot, and it is much better than the "supermarket fresh".

But what do I know? If I'm near a McDonald's and craving a fish sandwich and there isn't a better option nearby, I just might stop in and get a Filet-O-Fish. It's nothing spectacular, but it is line-caught wild Alaskan pollock.

Just be sure to order it without cheese. Because number one, American cheese on fish is gross. And number two, it means they have to make you a fresh sandwich and not give you a premade one.

(Disclosure: I work for McDonald's, at least until the end of this month.)

Isn't practically everything you see in a fish market flash frozen anyway?

Afaik there's very little fresh fish going around, period. It's all frozen on the boat.

A friend told me that he never, ever eats frozen fish, but he does enjoy all varieties of sushi and sashimi, and he explained to me that those are never frozen.

I tried to convince him otherwise, but never got anywhere.

https://www.seriouseats.com/how-to-prepare-raw-fish-at-home-...

In some places it is illegal _not_ to freeze the fish for sushi, to avoid anisakis (I don't know how it is enforced, though).

source: https://elpais.com/sociedad/2006/12/20/actualidad/1166569202...

We hope so! Flash freezing kills parasites

(Sure, it's not an issue if you cook it thoroughly before consumption, but still)

> We hope so! Flash freezing kills parasites

It depends where you are.

If you are in a Western country, then yes, "sashimi grade fish" equals "frozen".

If you are in Japan, then no.

Its all to do with the understanding of fish and its handling.

In the West its all commoditised, quantity over quality.

In Japan, they have a deeply rooted fish culture, a focus on quality and are obsessive over food hygiene.

So in Japan your sushi won't be pre-frozen, but it will have been meticulously inspected and prepared.

Fun fact, salmon sushi/sashimi is a Western thing. The Japanese don't eat it because the parasite risk in Salmon is so much higher than any other fish.

Personally, having visited Japan a number of times, I will not eat sushi or sashimi outside of Japan any more.

I live in Japan and some of this is a bit wrong.

1. All Tuna is frozen immediately after being caught on the boat - go to tsukiji (well now toyosu) at the tuna market. They are frozen and they taste better because of it.

2. There is no sushi / sashimi grade in Japan. High quality fish that you can eat safely is just the default

3. It's true that traditional sushi did not include salmon because of the parasites. If you go to a traditional sushi restaurant (3 star Michelin etc) you won't find salmon nigiri. Other than that salmon sushi is everywhere at sushi restaurants in Japan and tons of Japanese eat salmon nigiri and sushi.

1. Noted, although I would say I didn't say all fish was not frozen.

2. That was kind of the point I was making. ;-)

3. I guess we must frequent different places, because the only places I've seen Salmon is Narita airport and at combinis. I don't go to 3 star Michelin, but I do admit I go to more traditional sushi restaurants when I want sushi in Japan. That said, even when I have had sushi at isakaya and small local restaurants, sashimi omakase rarely contains Salmon.

There are many restaurants in Hokkaido that have the seafood version of oyakodon, Salmon and roe.

https://hokkaido-labo.com/en/otaru-seafood-donburi-14255

> 2. There is no sushi / sashimi grade in Japan. High quality fish that you can eat safely is just the default

Many fishes in supermarket are sold as "for heat cooking" except for sashimi. It's costly to make all salmon raw eatable.

Agree for others.

The hell? Have you been to Tsukiji Fish Market? Its immediately obvious that everything is flash frozen

This reads like some old school weeb shit

> Its immediately obvious that everything is flash frozen

"Everything" is a bit of an exaggeration.

I'm sure like at all fish markets, there is frozen fish available, either because it was imported or because that's the way it was pre-processed on the local boat.

But to say "everything is flash frozen". That's pushing it. You fall flat at shellfish at a start. ;-)

> Personally, having visited Japan a number of times, I will not eat sushi or sashimi outside of Japan any more.

Most of us cannot travel to Japan every time we want to eat sushi, so that's simply not practical.

> Most of us cannot travel to Japan every time we want to eat sushi, so that's simply not practical.

FFS !

Did I ever say I travelled, or that anyone should travel to Japan every time ?

No.

Incase you had not seen, Japanese cuisine goes beyond sushi and sashimi.

The quality of sushi and sahimi in the West is simply so poor compared to Japan I won't waste my money. That is what I am saying.

I simply said I do not eat sushi and sashimi. I can fill my Japanese desires with other culinary aspects and save myself for as and when I might visit Japan.

> Incase you had not seen, Japanese cuisine goes beyond sushi and sashimi.

Well, yes, some of us have visited Japan and tried their cuisine, both in their own country and in Japanese restaurants in other countries.

There are also authentic Japanese sushi bars outside Japan, run by Japanese chefs, and making superb sushi.

I really don't understand what you're trying to say here.

> Fun fact, salmon sushi/sashimi is a Western thing. The Japanese don't eat it because the parasite risk in Salmon is so much higher than any other fish.

All the conveyor belt sushi chains I’ve eaten at definitely had salmon nigiri on the menu. In fact, they had a wider variety of salmon than what is commonly found in the US. It is most definitely a thing Japanese people eat because otherwise there wouldn’t be five menu items dedicated to just salmon at every major conveyorbelt sushi chain.

At least in the US, a significant amount of the fish you eat in high end restaurants, sushi restaurants and fish markets is never frozen.

It is packed in ice and kept very cold, but not frozen.

Supermarkets are more likely to stock frozen/previously frozen. Lots of commodity seafood is frozen when caught.

Source: Spent a season offshore fishing for swordfish/tuna. Worked in the warehouses that unloaded and shipped the same. Drove the truck that delivered the fish.

Ah, the more you know. Fish guy has spoken I guess.

At least for white fish.

> American cheese on fish is gross

American cheese is gross full stop. ;-)

As is American chocolate.

My European friends: “Hersheys tastes like vomit.”

The same people: “So I know it’s Halloween over there and um… can you send us some Reese’s cups?”

> As is American chocolate.

You've been eating the wrong American chocolate. Hershey's isn't the end all and be all. There are plenty of good chocolate makers and even more good chocolatiers in the US, you just need to explore a bit. L.A. Burdick in New Hampshire, for example, makes really great chocolates, and has a nice wide range of single source bars made with beans from plantations all over the world.

true of cheese as well. Tillamook in Oregon produces fantastic cheese (which is widely vended). The way I think about it is that the average american food is poorer than average european quality, but that our best producers make some of the best in the world.

European chocolate tastes dull.

Snark aside, it's about what you grew up with. Fascinating video: https://www.youtube.com/watch?v=J44svaQc5WY

>> American cheese on fish is gross

> American cheese is gross full stop. ;-)

Cheese on fish is gross full stop.

> As is American chocolate.

Particularly on fish, I'd guess.

I don't eat fish, but I have heard that when modern flash freezing is done properly, you cannot tell the difference from actual fresh.

Unless you’re buying your fish every morning in the fish market at the harbor, it’s probably been frozen. Even wild caught is typically frozen as soon as it’s hauled aboard.

This will vary around the world, of course.

Supposedly, flash freezing (which is distinct from your average home freezer unit) preserves quality such that even trained sushi chefs can't tell the difference between fresh and previously flash-frozen fish.

https://www.nytimes.com/2004/04/08/nyregion/sushi-fresh-from...

Indeed, there are some types of fish that are safe for "raw" consumption only after being flash frozen, due to parasites that live in the fish.

Many of those frozen like that were flash frozen on the boat and are fresher than even what you buy at the fish market direct from the boats that landed that night.

It really does depend on your location. Here in Iceland I can get fresh fish that was caught the same day in my local fish store (mind you not all their fish is caught that day, but most if not all inside 2).

Though with the globalized world we live in, I was even able to get fish from Iceland no older than 2 days in Edmonton Canada when I lived there some years ago.

edit; I'll add that there is a massive texture difference in white fish depending on if it has ever been frozen. Flaky fresh never frozen cod becomes like chewing gum after having been frozen.

> I only buy fish that is in season, not farmed, and that is genuinely fresh from reputable suppliers, not supermarket "fresh".

I think everyone wants this, but it's not always practical. Not everyone lives in a coastal area with access to fresh fish of the kind they would like to eat. If you do, more power to you! But if you don't...

Freezing fish also has the benefit that it kills parasites.

The fish you buy even from reputable suppliers was very likely flash frozen on the boat before it ever reached land. Many fishing boats are out for several days or weeks at a time. So just because it's only been on land a short time, that doesn't mean it's recently caught.

This is a good thing because many fish harbor parasites that are killed when flash frozen. Your home freezer doesn't reliably get cold enough to take them out. You can reliably kill them by cooking very thoroughly, but since fish is such a delicate meat, the line between "may still have wriggling worms" and "overcooked, dry, and unpalatable" can be quite fine.

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