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Better Espresso thru Freezing

Postby Ken Fox on Mon Aug 24, 2009 11:31 am

I mentioned this idea to Jim Schulman in one of our regular emails recently, and perhaps others will consider it interesting enough to comment upon.

I can't speak to anyone else's experience with fresh coffee used for espresso, however my own experience with carefully home roasted high end Single Origins shows a very obvious pattern. My coffees tend to really "shine" during a relatively short period, which on average would be, counted from the roast date, from days 3-4 to days 7 or 8. Various factors could effect when this period of peak freshness occurs in the "degassing cycle," but I doubt very many coffees have a peak time period of more than 3-4 days in total.

It isn't that the coffee really and truly sucks just before and after that, rather it is that there is a period when my espresso's are at their best, and a period of time before or after that when they are "ok" but seldom spectacular. Perhaps other types of coffees (blends) dosed differently (I use around 14g per double shot) produce different results and a longer period of peak freshness, but I have my doubts and think that any quality coffee probably behaves more or less like this.

Being a home roaster, I have more control over this time and usage period than many. Like most here, I generally don't start using freshly roasted coffee for espresso until it has degassed somewhat; seldom do I start using a just-roasted coffee until it has degassed for 3 or 4 days. That part is the easy part. Generally some of what I roast will not get consumed until as much as 10-12 days after roasting, although generally the older the coffee the more likely it is to go into a milk drink.

As a proponent of freezing, I freeze quite a bit of coffee in a cold freezer, immediately after roasting.
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Up until now, I've used freezing "passively," e.g. in a way that reduces the frequency of my roast sessions, and to deal with situations where I have more freshly roasted coffee than can be consumed before it goes stale. But what about another approach, the intentional use of freezing to enhance espresso quality?

My experience, both through blind taste testing and through normal use is that freezing preserves the fine qualities of fresh coffee, at least when done immediately after roasting, using a very cold freezer (others here can comment on their experiences with partially degassed coffee, such as what they get through mail order, or a less cold freezer such as one attached to a refrigerator).

So here's the question: Wouldn't it make more sense in regular use, for those who don't either buy or roast coffee extremely often, to only leave out enough coffee at one time that it can all be consumed within this 3-4 day "peak" time window, and to rely on the freezer, on a regular basis, defrosting only what can be consumed, each time, within a similarly short time window? For me, this would mean freezing a greater percentage of what I produce in a roast session, and drinking a lot higher percentage of previously frozen coffee than is my normal practice. For others, this could mean putting more of their mail order or other commercially purchased coffees into the freezer on receipt, and consuming less when it is "fresh" and not previously frozen. I have not observed a shortening of the "peak" period in previously frozen coffee, but even if you thought that this was the case, you could just adjust the approach by reducing the quantity size of frozen coffee that you take out of the freezer at any one time.

Does this make sense as an overall strategy for maximizing espresso quality in a home environment?

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Postby JohnB. on Mon Aug 24, 2009 12:03 pm

This is exactly what I have been doing with both commercial blends & my home roasted coffee for quite some time. I normally let it degas 3-4 days before I break it down, vac bag & freeze in 1 of our storage freezers. I package my Vac Pot/Cold Brew/Press coffee in 1 use bags ranging from 24g-84g & my espresso in 4-5 shot (14-15g) bags.

As far as my home roast goes I find it comes into it's prime around day 5 although some, like the Yemen Sana'ani, take until day 7-8. Some of the commercial blends like Black Cat need 8-10 days rest. From my experience it does seem that frozen roasted coffee does age faster once out of the freezer then roasted beans that have never been frozen. Anyone else notice this?
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Postby timo888 on Mon Aug 24, 2009 12:21 pm

Ken Fox wrote:Wouldn't it make more sense in regular use ... [to defrost] only what can be consumed ... within a ... short time window?


I dose from the freezer directly into the grinder and directly from the grinder into the basket or french press. I don't allow the beans to come to room temperature before grinding them. There's no time for [significant] condensation to form. Some here are concerned about the alleged bad effects of condensation. I say "alleged" not because I'm disputing the claim; but my approach hasn't let me discover first hand what the bad effects might be. How much condensation is too much? When and how do the bad effects begin? What are they?
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Postby DavidMLewis on Mon Aug 24, 2009 12:36 pm

Timo, do I assume from this that you package and remove from the freezer only what you are going to use? Moisture would clearly condense on beans at freezer temperature almost immediately when exposed to room temperature/humidity air, and while that might not affect coffee ground then, you would expect it to affect coffee repeatedly removed from the freezer and replaced, or coffee allowed to come up to room temperature with the condensation on it.

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Postby shadowfax on Mon Aug 24, 2009 12:39 pm

Hmm, I'm thinking, why bother with the coffee when there's Ben & Jerry's Chocolate Fudge Brownie to be had? :mrgreen:

But seriously, using a "thawing window" to keep the coffee that you're using for any given day in its peak window seemed like the natural step from the results Jim and Ken got from their freezing experiments. I do this, and since I don't have the space, really, for a deep freezer, I've also just used the freezer part of my refrigerator. I haven't noticed any reduction in shot quality since I've been doing this, but I also haven't done any methodical testing of that, so I can't say for sure if it's 100% safe. I enjoy my espresso at home a lot, and for the moment that's enough for me.

Timo, I'm also curious about grinding froze coffee. I would think it'd be more brittle and result in a higher proportion of fines in the grind. That might be a good thing, though...
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Postby timo888 on Mon Aug 24, 2009 12:42 pm

DavidMLewis wrote:Moisture would clearly condense on beans at freezer temperature almost immediately when exposed to room temperature/humidity air, and while that might not affect coffee ground then, you would expect it to affect coffee repeatedly removed from the freezer and replaced, or coffee allowed to come up to room temperature with the condensation on it.


I remove from the container only the dose required, turn on the grinder, and return the container to the freezer while the beans are being ground. I haven't noticed any problems from the container being opened briefly and quickly closed again and returned to the freezer. Don't know how to measure that incidental condensation and compare it to the condensation that would form on, say, a few days worth of beans that have been removed en masse from the freezer and allowed to thaw.

P.S. There would have to be an air-exchange for condensation to form on the beans in the container: the warm-moist air from the room would have to displace the cold air in the container. But that takes time and/or significant air currents, right? The cold air would tend to remain trapped in the container, insulated by the beans that fill it.
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Postby timo888 on Mon Aug 24, 2009 12:45 pm

shadowfax wrote:Timo, I'm also curious about grinding froze coffee. I would think it'd be more brittle and result in a higher proportion of fines in the grind. That might be a good thing, though...


I don't know about the beans developing brittleness, and fracturing when ground. They're oily. And mine are not being kept in the deep freeze in the basement but in the refrigerator's freezer compartment. They're there only for two-three weeks as a general rule, though sometimes longer.

But maybe it's time for some electron microscopy.
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Postby shadowfax on Mon Aug 24, 2009 12:55 pm

timo888 wrote:Don't know how to measure that incidental condensation and compare it to the condensation that would form on, say, a few days worth of beans that have been removed en masse from the freezer and allowed to thaw.


For my part, I use a brake bleeding pump and a food saver attachment to draw a significant amount of the air (and moisture in the air) from the mason jars that I store my coffee in prior to storage. I also allow my jars to come fully to room temperature before opening them. Since they are sealed, there is a minimal amount of condensation that they can be exposed to. I don't think there's any condensation that forms on the beans, at least from what I can tell. I've glanced at jars as they are thawing, and when I wipe the heavy condensation off the outside of the jar, there's no evidence of any on the inside, either on the jar walls or the beans.

With that said, I could believe what you're doing is perfectly safe... the beans never thaw, so I'd imagine that makes it 'safer.' Still, it's not my style at all (I usually pull my coffee out of the jar a day in advance of (or right at the beginning of) when it will be in its peak and put it in the hopper, using it to weigh down today's coffee, which was in turn taken out the day before--usually. I get great shots this way, to my palate, and the method fits well with my grinder--I'm allergic to popcorning. Part of my personal psychosis.

Of course, anyone whose methodology is more lax than mine is suffering through crappy coffee, and they just don't know it. Anyone whose methodology is more strict than mine is putting themselves through undue stress for a complete lack of improvement in the cup. Your method, Timo... I think you need to lay off the hallucinogens, bro! :wink:

timo888 wrote:But maybe it's time for some electron microscopy.

Any time is a good time for that on Home-Barista.
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Postby malachi on Mon Aug 24, 2009 2:20 pm

so... not "better" in the sense that freezing inherently improves espresso, but "better" in the sense that you don't have to consume espresso made from "past their prime" beans? (just want to be clear on this)
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Postby another_jim on Mon Aug 24, 2009 2:27 pm

The top cafes all make a point of using their espresso blends inside a two to three day window, so staggered freezing and unfreezing is a natural.

However, my experience has been more varied, and I'm also far less organized than Ken. Some coffees clearly do peak inside a narrow time window; but others just change, showing different aspects over time, with none clearly better than the others. Finally, some coffees are just plain jittery, like Yemens, showing arbitrary and sometimes bizarre or unrepeatable tastes on any day from roasting to three weeks out.
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