a few thoughts on stale coffee

[Ken Gargett]

came across this. harold mcgee is perhaps the pre-eminent food scientist/writer of this generation (his book, 'on food and cooking' is revered), so unlike our 'tea' bloke, at least here we have an authority.

The Science of Stale Coffee

The science behind your daily cup.

By Harold McGee January 8, 2016

It was a dazzlingly bright and blue morning—the kind of day that makes me think San Francisco has better weather than it does—when I met up with Harold McGee. McGee had agreed to let me poke and prod him to see what sort of breakfast-y food-science facts I could squeeze out of the giant brain in his remarkably normal-sized head.

We attempted to convene at a diner, but the place we’d picked had a line around the corner. We retreated to Swan Oyster Depot, where we figured we could conjure thoughts about eggs while slurping melon-sweet Kusshis and amber glasses of Anchor Steam. But the line there was twice as long, stretching ever so gently uphill, toward Oregon. So we walked a few blocks and took a table at the Belcampo Butcher Shop & Restaurant on Polk Street, where our conversation turned to coffee, which we were not drinking, as we chatted through half an hour, waiting for lunch service to start. —Peter Meehan

My taste in coffee has changed a lot over my lifetime. I began with basic percolator coffee after graduating from tea, which is what my parents drank. I discovered dark roasts in college, bought my first grinder, and then moved to the West Coast, where I discovered Peet’s. Years later, Peet’s gave way to Blue Bottle, Four Barrel, and so on. And for years, those coffees were what I really loved, but lately I’ve found them to be too acidic, too tart. I’ve moved back in the direction of the darker beans. There’s a coffee roaster here in San Francisco named Andrew Barnett, who has a place called Linea Caffe, where he roasts darker than the other guys, and that’s where I usually go for coffee these days.

Sometimes, when I come back from a trip, I’ll find that I didn’t think ahead and put my coffee in an airtight container in the freezer. I’ll open my kitchen cabinet, and find that all I have to work with is a bag of maybe two-cups-of-coffee’s worth of beans that have been sitting there for three weeks. I’ll make a cup of coffee with it, and you know what? I’ve come to enjoy that cup of coffee, that “bad” cup of coffee.

So now I do it on purpose. I don’t bother making a special point of putting coffee in a jar to put in the freezer to preserve the beans, because I’ve come to appreciate stale coffee. It’s a flavor I recognize from the not-so-good old percolator days that gives me a certain amount of pleasure.

While I’ve had eye-opening revelations with coffee—an Ethiopian coffee from Blue Bottle that tasted like blueberries comes to mind—I’ve never really become a nerd, which I guess is another way of saying I’m a dilettante about coffee.

It reminds me of a conversation I once had with Jeffrey Steingarten about a melon I’d tasted. It was wonderful, I told him, and really interesting because there was a hint of the squash family to its taste, a pumpkin-y note. (Melons and cucumbers and squashes are all in the same family.) Jeff said, “So what you’re saying is that it was a bad melon, McGee. Have you never heard of connoisseurship?”

I’m not a connoisseur; I dabble. To the extent that I can make connections for myself that create bridges between my experiences, I do. I think there’s a lot of “geeking out” on the details that go beyond what we can actually taste. I am most interested in the actual experience of consuming coffee. Sometimes you have the connoisseurs’ perfect melon, and sometimes you have a cup of stale coffee.

And because I know a little bit about what’s going on in food and why you end up with different flavors, I find that that cup of coffee is a good chance to refresh the circuits in my brain that ask, Why does it have that stale flavor?

Well, the more volatile and unstable molecules in the coffee have dispersed and disappeared, and some of the not-so-volatile things have stayed behind and reacted with each other and with oxygen. It’s a more complicated version of what happens to old cooking oil. You’ll know what I’m talking about if you’ve ever bought a too-big bottle of canola oil that ends up in the back of your pantry for a few months. When you dig it out to cook with it, it smells different. Instead of being neutral, it has this very distinct oily flavor and aroma.

What’s happened is that the oil has oxidized from the action of air and light—two sources of energy that transform the oil. They break the fat molecules apart into smaller molecules and then break those fragments into even smaller ones. The oils themselves are so large that they don’t volatilize—they cling onto each other, because they’re long and they can’t escape. What you’re smelling are the pieces that are light enough to float away. That’s a big part of why storing your coffee in a vacuum bag in the freezer keeps it freshest: you’re preventing its more volatile aromas from escaping, and you’re keeping heat, light, and oxygen away from the beans, so they can’t start breaking up their more sensitive molecules.

Now, the exact chemicals volatizing from your staling beans are different from what comes out of the Mazola—coffee beans have many hundreds of molecules in them that can present a wide spectrum of smells. But food chemists (and people like me who try to understand what the food chemists catalog) try to simplify things. We get the major categories right, understand the processes at work, and then try to construct a plausible story for why things smell like they do. The story of why you taste and smell the things you do is always a story that someone made up based on the information available to them.

Other aspects of the flavor experience of coffee can be more easily quantified. Take acidity—you can actually notice the difference from one coffee to the next, not only by taste, but also by what it does to the milk you pour into it. Elli, my companion, likes to put soy milk or soy creamer into her coffee, and with Four Barrel and Blue Bottle, the soy milk curdles as it goes into the cup, due to the higher acidity in those brews.

Acids are readily available in all coffee beans. Coffee beans are, reductively, made of two different kinds of material. One part is nourishment for the seed. The coffee plant normally grows in the understory of the forest with a lot of competition for light, so it has to have enough energy stored up in its seed to push out its leaves and make chlorophyll. The other part is defensive chemicals, so when an insect or a fungus begins to nibble on the outside of the bean, it gets a hint of astringency or bitterness, and it leaves the bean alone.

The sugars in the nourishment part of the package break down into familiar food-like acids during roasting—acetic acid, for example, which is the main acid in vinegar, or lactic acid, which might add a buttery note. They are liberated in the early stages of the roasting process, so when you halt a coffee at a light or medium roast, you maximize its acidity.

Later in the roasting process, when the beans go shiny and dark, you begin to destroy those acids, and that’s why darker roasts can seem milder, even though they’ve actually been heated in a more extreme way.

Sorting all these flavors and how they come to the cup is what interests me, and why it can be just as interesting to untangle the hows and whys of a stale cup as it is to explore the floral and fruity notes of a really fine cup. Staleness is a part of life and part of what happens to all foods. I’m catching the coffee at a different stage in its lifetime, and I think it’s good to have the whole spectrum available to think about and experience…

A waitress interrupts Harold to take our order.

Actually, I haven’t looked at the menu. But I’d like the bone broth. I’ve never had bone broth. Have you?

This interview was edited and condensed, but we did just talk about coffee until the waitress arrived. We never even got to eggs. Maybe in the future!

[suggs]

This was a nice read, Ken! Thanks for sharing! Usually I try to stick to the "Rule of Fifteen" (that green coffee is fresh for 15 months, roasted is fresh for 15 days, ground for drip is fresh for 15 minutes) but I think McGee's point of tasting things that are past their prime is definitely spot-on.

[Fugu]

Thanks for posting this one, Ken. “After graduating from tea”… . Nice article indeed and certainly on a different level as the tea-one. The guy appears not only knowledgeable, his writing is also of a more enjoyable stile (at least more appealing to me, not like the slightly red-top-ish stile of the other).

Some thoughts (as usual… haha), on the aspect bean freezing/storage:

I guess most half-decent coffee drinkers have made that experience as well. But I wouldn’t call it necessarily “staleness”, I’d rather call it micro-oxidation. But that’s certainly a matter of gradation. Can be the same, intentionally done and then rather beneficial process that takes place in wine (I mean making), in certain teas, whisky & Co. and of course also in tobacco. We wouldn’t call that stale, would we? In coffee, three weeks might be quite at the tipping point, true…

Although most coffee-geeks and in particular the espresso-nerds and the home-roasters get stoked about “as freshly roasted as possible”, I for one like my brews and espressos done from beans of about 4 to 8 days post-roasting. I feel, they start out harsher when very fresh (in the main due to the CO2-content), rounding out nicely in taste after a couple of days of rest, and then begin slowly descending after about 8 to 15 days (depending on variety, roast, room temp. etc.), while they can usually still be fully enjoyed at that time. So there is a certain optimum curve, and – I discussed this aspect with my roaster before – he says, similar takes place in his raw beans, which are showing a clear optimum in their development in the storage, but that is measured in months. Freshest is clearly not best.

I always keep my beans in airtight bags and boxes with very limited air access, but at normal room temperature.

My take: You may freeze your cigars – but: never freeze your beans!

There are different “schools” when it comes to the discussion on freezing of beans. The author is right of course in his analysis of the chemical reactions being stopped during freezing (oxidation and breaking up of oils and their further decay products). But that can and will, to some extent, be part of the positive development post-roasting. And in addition, from my experience (I stand not alone with that), freezing in itself has a noticeable direct effect on the taste. Think of deep-frozen strawberries as an example! Even when stored in the fridge, strawberries unquestionably loose aroma compared to fresh ones left uncooled. The very same seems to go on in coffee beans. The subtle changes are perhaps less noticeable in coffee due to overlying stronger flavours, in particular in darker roasts.

So there is certainly a trade-off in freezing beans between the effect of conserving oil’s freshness/virginity and avoiding staleness on one side and losing some of the original flavour components and the halting of a positive post-roasting maturing on the other side.

Well, if you buy several pounds online, you will probably have no other choice than freezing part of it. But in the short-term, up to perhaps two to even three or four weeks, non-freezing and even non-cooling is to be preferred in my view, while keeping beans as airtight as possible (the outgassing of CO2 from the beans provides a kind of protective atmosphere against O2 for some time, as long as packaging is kept untouched). There are different opinions, but that’s my personal ‘operating’ experience. Therefore, instead of freezing in quantities, personally I go for regularly purchasing smaller quants (my local roaster roasts his different batches on a daily to weekly schedule) for immediate consumption, to be used up within 7 to 14 days.

[Fugu]

This was a nice read, Ken! Thanks for sharing! Usually I try to stick to the "Rule of Fifteen" (that green coffee is fresh for 15 months, roasted is fresh for 15 days, ground for drip is fresh for 15 minutes) but I think McGee's point of tasting things that are past their prime is definitely spot-on.

Agreed, that's indeed a very pracitcal rule.

[squizz]

Good read, I'm in the habit of grind before brew. Keep all my coffee whole bean and sealed up tight. I've been a french-press type drinker for awhile. Lately, Ive been digging the pour over method.

[suggs]

Although most coffee-geeks and in particular the espresso-nerds and the home-roasters get stoked about “as freshly roasted as possible”, I for one like my brews and espressos done from beans of about 4 to 8 days post-roasting. I feel, they start out harsher when very fresh (in the main due to the CO2-content), rounding out nicely in taste after a couple of days of rest, and then begin slowly descending after about 8 to 15 days (depending on variety, roast, room temp. etc.), while they can usually still be fully enjoyed at that time. So there is a certain optimum curve, and – I discussed this aspect with my roaster before – he says, similar takes place in his raw beans, which are showing a clear optimum in their development in the storage, but that is measured in months. Freshest is clearly not best.

Great points, Fugu! I've been a home-roaster for two years now and I think our preferences and experiences are pretty similar. I'll try to roast two or three days in advance of when my recent batch runs out because the first few days of the CO2 de-gassing gives a lot of grassy/vegetal harshness to me. I fully agree with the 4-8 day mark being the plateau of the coffee's taste/freshness for drip, even though we'd probably get some grief from the espresso geeks!

[Ken Gargett]

the bloke who made the best coffee i ever had, used to buy little coffee shops on the coast and quickly build up a serious clientele and then sell them to people who, for reasons unknown, always thought they could improve them (the number of times he ended up buying back the shop he'd sold for a fraction of the price would stagger you).

he'd keep blends in his fridge at home and from memory, had 2-3 days as the peak. had amazing knowledge. love to know what happened to him.

[NapaNolan]

Good read, I'm in the habit of grind before brew. Keep all my coffee whole bean and sealed up tight. I've been a french-press type drinker for awhile. Lately, Ive been digging the pour over method.

I always liked the richness of French Press but hate the gunk at the bottom of my cup. I've been doing a FP/pour-over hybrid where I let the grinds brew for 4 minutes (stirring occasionally) then pour that through a pour-over with a filter. I still get great, rich, flavorful coffee but with none of the sediment.

[suggs]

I always liked the richness of French Press but hate the gunk at the bottom of my cup. I've been doing a FP/pour-over hybrid where I let the grinds brew for 4 minutes (stirring occasionally) then pour that through a pour-over with a filter. I still get great, rich, flavorful coffee but with none of the sediment.

You might want to try a Clever Coffee Dripper. Best of both worlds for you!

http://www.amazon.com/Clever-Coffee-Dripper-Large-Ounces/dp/B00EOM5RN0

[NapaNolan]

You might want to try a Clever Coffee Dripper. Best of both worlds for you!

http://www.amazon.com/Clever-Coffee-Dripper-Large-Ounces/dp/B00EOM5RN0

Yeah I use this http://www.amazon.com/Melitta-64008-Ready-Filter-Cone/dp/B000YA7OUK/ref=sr_1_2?s=hpc&ie=UTF8&qid=1452741006&sr=1-2&keywords=melitta+pour+over

But find that without letting the grounds steep for several minutes I don't achieve the body and mouthfeel I like.

Edit: Okay I really looked at the link...looks nifty!

[fabes]

That was a cool article. Like our cigars, the taste and journey is unique to everyone.

I do think the tasting of coffee: fresh, stale over/under extracted is helps to appreciating it for when it's grown, harvested, roasted and brewed well. Same as cigars. Try em young and as they age. See the progression. See the variety within a box. It helps to appreciate the "ON" we all desire. Light up in a thunderstorm to see how humidity affects the smoke. Have fun along the way.

[Fugu]

I fully agree with the 4-8 day mark being the plateau of the coffee's taste/freshness for drip, even though we'd probably get some grief from the espresso geeks!

Perhaps, but we'll brave that