hotter temps on fresh coffee

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hotter temps on fresh coffee

Postby Emily Oak on Thu Mar 05, 2009 12:40 am

I've been told a number of times at various stages that with fresh coffee you tend to get a better taste and more 'controlled' performance when a machine is typically hotter (204'F or more).

Has anyone heard this theory - and if so why would heat have this effect on fresh coffee? I haven't really done any experiments myself, but we're talking here about nitrogen flushed and sealed/packed and flushed coffee - fresh being within the first 5 days, and stable (generally used) between 10-17 days after roasting, generally being brewed around 203 or 203.5'F.

Thoughts? Experiences?
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Re: hotter temps on fresh coffee

Postby Jason Haeger on Thu Mar 05, 2009 11:07 pm

Interesting theory.

I can almost imagine the link, but the mental bridge is incomplete.

Is a higher amount of gas the only difference between "too-fresh" and "just right" coffee?

I've always assumed that this is NOT the case, however, that doesn't mean I have any idea whatsoever on the details of what else is entailed in that.

I'll have to pay attention to this. Interesting.
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Re: hotter temps on fresh coffee

Postby Matthew P. Williams on Mon Mar 09, 2009 6:13 pm

Jumping in with a quick hypothesis...

Fresh coffee = more CO2 in grounds

more CO2 in grounds = more CO2 in solution

more CO2 in solution = reduced solvency of H2O [higher concentrations of CO2 interferes with solubles extraction]

water's solvency increases as temperature increases

therefore - higher water temperature mitigates the interference of CO2 on solubles extraction
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Re: hotter temps on fresh coffee

Postby Matthew P. Williams on Mon Mar 09, 2009 9:28 pm

Nick makes reference to this gassy behavior. In that thread, fining of grind (increased surface area = more available solubles) is discussed as the method used to mitigate interference of CO2 on solubles extraction... there is more than one way to skin a gassy cat.
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Re: hotter temps on fresh coffee

Postby Jason Haeger on Mon Mar 09, 2009 10:04 pm

Well, grinding finer also means releasing more CO2 before initial water contact, which is what I assumed made up for the difference.

I had assumed (potentially falsely so) that not all aromatics carried by CO2 were desirable, and that degassing allowed for some of those more readily released components to.. well.. be released.

I can understand the higher temperature relating to higher extraction rate, but it also affects what is being extracted, does it not?

Are some of these more volatile components "killed" (for lack of a better word) by the higher temperature?

So many questions, so little sense made of it all (to me).
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Re: hotter temps on fresh coffee

Postby Matthew P. Williams on Mon Mar 09, 2009 10:32 pm

Jason Haeger wrote:Well, grinding finer also means releasing more CO2 before initial water contact, which is what I assumed made up for the difference.


Does a slightly finer grind have such a drastic effect on dissipation of aromatics? Basically... I don't think that fining the grind is employed as a strategy to encourage CO2 dissipation, but rather to increase availability of soluble material.

Jason Haeger wrote:I had assumed (potentially falsely so) that not all aromatics carried by CO2 were desirable, and that degassing allowed for some of those more readily released components to.. well.. be released.


I don't think this is what we are really talking about here... CO2 soluble aromatics?? No, I should have been more clear; I am not talking about extraction of aromatics. I have attempted to give an account of carbonic acid and how it affects the extraction of solids: sugars, oligosaccharides, lipids, etc.

Jason Haeger wrote:I can understand the higher temperature relating to higher extraction rate, but it also affects what is being extracted, does it not?


Yes, but that is the point - in this model, the higher temperature is compensating for a deficiency in solvency due to higher concentrations of carbonic acid.

In other, less terse, words: you've got a very fresh coffee with lots of residual carbon dioxide. The CO2 dissolves in water under pressure to create a carbonic acid solution. For whatever reason - pH, difference is concentration gradients, something else? - the solvent (water) is less capable of extracting solids from the puck, compared to a model with older, less CO2-laden coffee... soluble extraction depends on this balance of concentration gradients. To compensate for this hindered dissolving power, you've got to do something: alter the solute, i.e. fining the grind, or make the solvent MORE solvent, i.e. increase the temperature.

Jason Haeger wrote:Are some of these more volatile components "killed" (for lack of a better word) by the higher temperature?


Maybe? I'm not sure how delicate aromatic compounds are in solution, but again, I think what we are really talking about is extraction of organic solids.
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Re: hotter temps on fresh coffee

Postby Emily Oak on Tue Mar 10, 2009 12:39 am

thanks guys - this is helping my non scientific mind! What you are saying certainly makes sense Matthew!
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Re: hotter temps on fresh coffee

Postby Jason Haeger on Tue Mar 10, 2009 8:22 am

In case my ignorance was not made blatantly clear, let me reemphasize it now.

I am only guessing, and I don't really know what I'm talking about.

That having been said, that doesn't mean I'm not going to try. Here we go.

When inhaled at concentrations much higher than usual atmospheric levels, it can produce a sour taste in the mouth and a stinging sensation in the nose and throat. These effects result from the gas dissolving in the mucous membranes and saliva, forming a weak solution of carbonic acid.(source)

Forget "inhaled", and go with "consumed".. or skip the dissolving in mucus membranes or saliva altogether, and just consider the higher concentration of carbon dioxide in contact with water under pressure at a high temperature.

From the same wiki page, "Liquid carbon dioxide is a good solvent for many lipophilic organic compounds,"... and I have no idea if this holes true for gaseous carbon dioxide or not. (but it might offer another clue)

It seems we are clear on one thing, and one thing only thus far. The problem is an excess of CO2. (and again, it is possible that this assumption is also wrong)

How strong is the solvent action of carbonic acid compared to water? How might temperature affect this? (if at all)

Does the dose change for this temperature-based "fix"?
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Re: hotter temps on fresh coffee

Postby Matthew P. Williams on Tue Mar 10, 2009 9:27 am

That gave me some insight into your point of view - I think you are looking at excess CO2 as a detriment in the cup itself, perhaps as an agent that interferes with taste perception. My view is quite different, taking carbon dioxide as an agent that interferes with extraction itself.

WRT the properties of CO2 you cite from wikipedia, there are a few things to be said about that. The physical properties of CO2 the article describes do not refer to CO2 in solution, but rather molecular CO2 and the phases it assumes within a range of temperature and pressure. We are not talking about liquid carbon dioxide, but rather carbonic acid.

Solubility of CO2 in water increases as pressure increases, but decreases as temperature increases. This property gives us fizzy water (the colder the water, the fizzier it stays), and gaseous crema. As the espresso leaves the portafilter, it moves from a high pressure environment where CO2 is quite soluble, to a low pressure environment where CO2 is no longer very soluble, so it is driven out of solution very quickly, where it is trapped in bubbles by lipids, starches, etc. that form the crema. This was kind of a tangent, but I just wanted to illustrate why I don't believe that excess CO2 is present in the cup itself. There may be more CO2 in the crema (but not in the cup), but how much? There is a physical limit to how much it can hold. High levels of CO2 in the crema MAY influence taste perception, but - once the crema has dissipated, that harsh edge of fresh espresso remains in the liquid, and CO2 is not the culprit there because hot liquid cannot keep carbonic acid dissolved - think of how soda gets flat as it warms.

I wish I knew wore about the properties of CO2 and how carbonic acid behaves as a solvent. Whether we are compensating for a lower pH or solvency of carbonic acid, I don't know - but I am quite convinced that excess carbonic acid decreases solubles extraction as I have described.

As for dose - a higher dose would necessitate a coarser grind, effectively reducing the proportion of available solids (to a point). Additionally, you are enlarging the heat-sink, counteracting the desired increase in extraction temperature.
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Re: hotter temps on fresh coffee

Postby Jason Haeger on Tue Mar 10, 2009 9:35 am

My intuition tells me that the dose should be reduced, not increased (and ground finer). This was what I was intending when I asked the question.

I could not find any free articles on solvency of carbonic acid when I made the earlier post, or I would have read through it and responded in turn.

I'm inclined to think that you are mostly right about dissolved CO2 not remaining so at higher temperatures, much less under natural atmospheric pressure.

But...

Anyone who's worked a shift with coffee that is too fresh will tell you. Bubbles always appear after a drink is poured more plentifully than with coffee that is not too fresh.

While I concede to the fact that the concentration is not as high as it would be at a lower temperature, but simple observation causes me to suspect that the concentration of dissolved CO2 is still higher than in espresso pulled from "rested" coffee.

I don't think this can be solved by pointing to any singular problem either way. I suspect it's a combination between the two.

Of course, we can discuss it on coffeed all day long and still end up with no hard evidence either way.

Has anyone done any work with this?
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Re: hotter temps on fresh coffee

Postby Matthew P. Williams on Tue Mar 10, 2009 10:42 am

Fining the grind is one way to deal with fresh coffee - see the post I referenced earlier. I'm not sure why I got on the track of updosing - that's how I read your post, probably because I was still in bed.

Downdosing not only increases solubility by necessitating a finer grind and consequently increasing surface area, but it also increases extraction temperature simultaneously. Just food for thought.

Of course the fresh coffee will be gassier. I was pointing to several things. I was suggesting that crema can only hold so much gas - there is a physical limit. A lot of CO2 escapes rapidly in superfresh coffee - voluminous, but not persistent crema. Whether "rested coffee" saturates this holding capacity and dissipates excess CO2, I don't know. My main point was this: the flavor profile of superfresh coffee is indicative of extraction rather than residual CO2. Try an Americano, or a shot after the crema has dissipated - that fresh edge remains in an environment where residual CO2 is negligible. Sure, we can talk about it all day long, but try it.

I'm not denying that excess CO2 can have a negative impact in the cup - superfresh coffee crema is edgy as hell - I just question that that is the primary culprit.
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Re: hotter temps on fresh coffee

Postby Klaus on Tue Mar 10, 2009 11:34 pm

Great post Matthew and interesting discussion to follow.

Matthew P. Williams wrote:High levels of CO2 in the crema MAY influence taste perception, but - once the crema has dissipated, that harsh edge of fresh espresso remains in the liquid, and CO2 is not the culprit there because hot liquid cannot keep carbonic acid dissolved - think of how soda gets flat as it warms.


This really got my attention. We've often talked about how really fresh coffee also has that kind of bitterness you find in a soda gone flat. So what is it in the soda that accounts for the bitterness once it's flat? Would it be the same thing (some by-product or result of the CO2) that we see in espresso?

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Re: hotter temps on fresh coffee

Postby Matthew P. Williams on Wed Mar 11, 2009 12:47 pm

Klaus wrote:We've often talked about how really fresh coffee also has that kind of bitterness you find in a soda gone flat. So what is it in the soda that accounts for the bitterness once it's flat? Would it be the same thing (some by-product or result of the CO2) that we see in espresso?


My impression is that in this comparison, there is not a direct analog between taste phenomena. In soda/pop/cola, carbonic acid plays a significant role in the taste profile. As I mentioned earlier, solubility of carbon dioxide decreases as temperature increases. Conversely, solubility of CO2 increases as temperature decreases, which is why carbonated beverages are produced at low temperatures and high pressures.

Up to this point, I have used dissolved CO2 and carbonic acid interchangeably, which may cause some confusion. Wikipedia explains the chemical composition of H2C03 and how it relates to carbon dioxide. It's fairly technical, and admittedly, much of it is over my head. Simply put, what I want to emphasize and simplify, is that when carbon dioxide is dissolved in water, a portion of CO2 bonds to H2O and forms carbonic acid, which is not very stable, but imparts a lower pH (more acidic) to the solution. Increase in temperature, decrease in pressure, agitation (shaking a can of soda), etc. dissociates the CO2+H2O bond and drives CO2 back out of solution.

Back on point, the comparison of flat soda to fresh coffee:

The carbonic acid in cold, fizzy soda acts as an acidifier. It imparts a tartness that balances the bitterness of caffeine and caramel color, and the sweetness of HFCS, aspartame, etc. When soda goes flat, the pH raises closer to neutral (though not completely - phosphoric acid is also used as an acidifier), changing the taste balance of the cola; it is not only more bitter, but it is sweeter. This does not describe a change in taste perception - a shift in sensation of present compounds - but rather a change in taste composition.

In speaking of espresso, I am speaking (typing) in broad, qualitative terms, but... I am highly skeptical of this phenomenon in espresso. I can't imagine carbonic acid concentrations at 60C-80C (serving temperature) high enough to impart such an effect. The bulk of the CO2 present in espresso is gaseous and trapped within the crema. A portion of this may dissolve in the mouth - how much/how significant, I don't know - but this tempts me to return to my original too/fresh comparison...

Even if CO2/carbonic acid is elevated in a cup of too-fresh espresso, again consider (and do try) the following scenario: Taste a shot of too fresh coffee at room temperature, after the crema has dissipated, and compare it with an acceptably aged coffee, also at room temperature with the crema dissipated. Or try them as an Americano. I point to these conditions because they greatly diminish the possibility of significant concentrations of carbonic acid, and the effect it imparts on the perception of taste balance... in the absence of carbonic acid in the cup, the too-fresh coffee STILL exhibits its characteristic edgy taste and flavor profile. This leads me back to my assertion that too fresh coffee presents a problem with extraction, rather than perception, and the methods we employ to combat freshness are modes of compensating for compromised solubility caused by high concentrations of carbonic acid.
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Re: hotter temps on fresh coffee

Postby fleck on Fri Mar 20, 2009 9:28 pm

i personally think that the best way to figure out the temperature at which your coffee should be brewed is to taste your coffee. don't make things so complicated.

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Re: hotter temps on fresh coffee

Postby Deferio on Sun Mar 22, 2009 8:00 am

Grinding finer makes sense but wouldn't that effect the brew time of the shot as well?
Increase the chances of over extraction?
I wonder if there really is no detriment to flavor delivered to the cup but instead...
Perhaps the presence of CO2 in the cup, whether much or little, simply delivers the flavors in varying intensities that change as the co2 dissipates.
The varying taste profiles due to the way co2 interprets the extraction (much the same as how milk in a mach, cap, latte interpret and uniquely deliver the flavor but do not "destroy" flavor)
becomes a matter of personal taste.
So then we are back to ...how does it taste? But knowing why is important so you can make it taste that way again.
-cd
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Re: hotter temps on fresh coffee

Postby Matthew P. Williams on Sun Mar 22, 2009 2:46 pm

In referring to fining the grind, I was also implying a reduction of dose, as it was discussed in this thread. Fining of the grind necessitates a smaller dose to yield the same extraction volume and time. This reduction of dose is justified by the fact that smaller particle size increases the surface area to volume ratio of the coffee particles. Ideal extraction parameters are in actuality more a function of surface area/volume than actual mass; in espresso, unlike other brewing methods, coffee solids are extracted strictly by washing/eroding rather than by diffusion. Essentially, fining of the grind and reducing the dose incrementally is an attempt to increase available soluble material while maintaining an "ideal" surface area/volume ratio. Again, this is a tactic to mitigate deficiency in solubility by increasing the solubility of the solute; increasing brew temperature is a method of mitigating diminished solubility by increasing the solvency of the solvent.

Chris, this CO2 flavor delivery point is what Jason had previously proposed, and what I have argued against is favor of a diminished solubility model. Please refer back to my previous posts about how too fresh espresso maintains its harsh qualities in environments where quantities of dissolved CO2 approach irrelevance.

I have never said that taste is not the ultimate arbiter of extraction parameters. When we are armed with a greater understanding of espresso mechanics, we are much better equipped to handle the fluidity and elusiveness of espresso. I'd much rather shoot a moving target with the lights on than in the dark.
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Re: hotter temps on fresh coffee

Postby Deferio on Sun Mar 22, 2009 3:40 pm

So here is a question...
Who did you used to work for or where do you work(ed)in the specialty coffee industry?
You have a great deal of eloquence high speaking when discussing these things...just wondering cause I only know your name from this thread.
As for your view on taste please don't think I am calling it into question. But rather, I agree with you in that we need more understanding to effect taste.
I need to work on understanding the scientific aspects more thoroughly for sure.
-cd
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Re: hotter temps on fresh coffee

Postby nick on Sun Mar 22, 2009 8:27 pm

Deferio wrote:So here is a question...
Who did you used to work for or where do you work(ed)in the specialty coffee industry?
You have a great deal of eloquence high speaking when discussing these things...just wondering cause I only know your name from this thread.
As for your view on taste please don't think I am calling it into question. But rather, I agree with you in that we need more understanding to effect taste.
I need to work on understanding the scientific aspects more thoroughly for sure.
-cd

Chris, be careful here, bro.

This comes across as very snobby, like you're saying that because he's not "known" by you, that he doesn't have the right to make his points. I know that's not what you meant, but this reads in a way that makes you look elitist big-time.

Hope Muncie's treating you well! See you in Atlanta?

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Re: hotter temps on fresh coffee

Postby Edwin Martinez on Sun Mar 22, 2009 9:50 pm

Interesting question Emily.

I like Matthew's quick hypothesis. CO2 does get in the way of water and hotter water extracts more than cold.

In many producing countries it is standard to cup right after sample roasting. I generally always preferred cupping the next day. As you know once coffee's ground it will stale faster... but if you wait 15 minutes before pouring water it is the same as waiting until the next day and pouring a couple minutes after grinding. Try it! Compare blooms. Dark roasts seem to stale and degas much faster.... 5 minutes.

Probably doesn't make sense to be waiting 10 minutes when you're messing with espresso and having to adjust a grinder.
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Re: hotter temps on fresh coffee

Postby Jason Haeger on Sun Mar 22, 2009 11:33 pm

Deferio wrote:So here is a question...
Who did you used to work for or where do you work(ed)in the specialty coffee industry?
You have a great deal of eloquence high speaking when discussing these things...just wondering cause I only know your name from this thread.
As for your view on taste please don't think I am calling it into question. But rather, I agree with you in that we need more understanding to effect taste.
I need to work on understanding the scientific aspects more thoroughly for sure.
-cd

He worked for Verve for awhile.

He's also been doing it up at home for years, including some pretty heavy mods to a hot air popper for roasting. He was also known on the web(coffeegeek, hb, et al) under the sn cpl593h, or something like that.
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Re: hotter temps on fresh coffee

Postby Deferio on Mon Mar 23, 2009 4:43 am

Sorry, coffeed if I sounded snobby.

I find that, knowing myself better than anyone...because I am always around me...is a great deterrent from snobbery or elitism. Trust me.
So thanks, Nick, for the benefit of the doubt.
My intent was pure.

And yes, Nick, I will be in ATL and Muncie is going great.

Blessings,
-cd
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Re: hotter temps on fresh coffee

Postby Matthew P. Williams on Mon Mar 23, 2009 8:37 am

I PMed Chris, since I am transitioning into another company.
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Re: hotter temps on fresh coffee

Postby gscace on Mon Mar 23, 2009 9:28 am

Just curious, what has been your experience been with doing this. Did it work for you tastewise? Dunno if I have the faintest clue about the chemistry, but I can hazard a guess on the "controlled behaviour" part - If the coffee leaving the horizontal hole in the spouts is gassy (as in new coffee), the hole will fill completely up with coffee and entrained gas bubbles. Gas gets liberated from the coffee upstream of the hole, pressurizing the stream, and making the coffee appear to "burp", which makes the pour look bad. It's pretty easy to see. I bet in addition to using less gassy coffee you get "controlled behaviour" from spouts in which the horizontal run is a sluice, rather than a hole, like the La Spaziale spouts. Now I'm gonna have to check this out, since my coffee is periodically just out of the roaster and I have a couple of La Spaz spouts.

-Greg


Emily Oak wrote:I've been told a number of times at various stages that with fresh coffee you tend to get a better taste and more 'controlled' performance when a machine is typically hotter (204'F or more).

Has anyone heard this theory - and if so why would heat have this effect on fresh coffee? I haven't really done any experiments myself, but we're talking here about nitrogen flushed and sealed/packed and flushed coffee - fresh being within the first 5 days, and stable (generally used) between 10-17 days after roasting, generally being brewed around 203 or 203.5'F.

Thoughts? Experiences?
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Re: hotter temps on fresh coffee

Postby Emily Oak on Tue Mar 24, 2009 3:53 am

Edwin - we wait 24 hours between sample roasts and cupping otherwise we find the coffee does not seem to exhibit as much lateral flavour (does that make sense?!) as it does straight off the roaster, same with the espresso machine.

I often have to taste espresso coffees with in 3 or 4 hours of being roasted as part of the QA work I do, and when comparing the same coffee 4, 7 or 10 days later there is a world of difference (obviously) in the taste.

From my very limited experiments (based purely on taste - I was a history student and failed chem) working with super fresh coffee sweetness and balance seem to be heightened if the temperature is raised slightly (1-4 days off roast and up by 0.5 or 1'F). I really was looking for a reason why this might happen. The same coffee tasted 7+ days after roast performs better when the temp is back closer to our 'usual' brew temperature of 203.5 (Synesso Sabre.)

I could throw in here for further discussion ageing the coffee at different times of the year - in summer we tend to go for 7-10 days after roast. In winter, we find that the coffee needs 14-17 days to peak....

:-)

maybe we can continue this in person in Atlanta....
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Re: hotter temps on fresh coffee

Postby Dan Streetman on Tue Mar 24, 2009 1:26 pm

Matt,

I am inclined to believe you about the effects of CO2 in coffee during extraction. Assuming that CO2 would be one of the first elements of the coffee to extract, and forming H2CO3 in the extraction process, that you change the pH of the brew water, and thus change the solubility of all the other compounds in the coffee itself. I don't know if this effect is inhibiting extraction or increasing it, but if it was inhibiting it then increasing our target percent of extraction would certainly make sense. Although in my experience "too fresh" coffee seems to blond more rapidly, than "properly rested" coffee.

However part of me is wondering how this can be established into a broader principle of espresso extraction. Why is it that we want a certain amount of gas in our coffee. Is resting the coffee helping us to reach a gas to oils(X) ratio? I say oils, because perhaps the presence of oils in the coffee (or some other compound) give the CO2 something other to bond with than the water and help to preserve the integrity of volatile nature of espresso. That and the fact the bubbles in "too fresh" coffee seem to be larger, and more volatile similar to when milk is overstretched or there is not enough fat content... my point being that the lipids in the coffee that are being extracted could be trapping the gas, and preventing it from being in solution with the water, But are more properly "suspended". If I remember right, this is the reason Illy calls espresso polyphasic... i.e. it is a solution, suspension, etc etc.

Again I also am a History major, so the chemistry here is based only on my understanding of espresso, but there is definitely something working here.
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