I love this, and even though it seems like the experiments were a failure, if one hadn't been it might have saved a lot of people a lot of money. As it is, it's saved at least a few people from trying the experiment themselves. Also there's a list of alternative uses for coffee grounds, and a link to another blogpost that expands on those in detail.
This post took more effort than 99% of blogposts, calling it blogspam is pretty offensive.
I think it’s a pretty easy and informative experiment to take espresso two shots from one puck in to two cups. I did this recently, the first shot was a beautiful, almost thick, sweet and sour coffee. The second one was like burnt dirt water.
Turns out the espresso machine is already set up to stop extracting just at the point where all the good flavours have been removed. (Also reason to be thankful that the good flavours happen to extract first)
Are well designed experiments actually failures? You set out to find out something: “can I extract sufficient caffeine from spent coffee grounds?” The person found out the answer. Sounds like a success.
> If you get all of those variables right, you will end up with the best, well-balanced cup of coffee in your hands.
Those variables were:
- coffee/water ratio
- grind size and consistency
- water temperature
- extraction duration
But there is a fifth element that should be observed that is the water hardness. Having too much or too little magnesium and calcium disolved in the water may result in wildly different cups of coffee. Yes, that is leaning more towards the pedantic side, but if you live in a region with extremely soft water, you have to fix water hardness because it is essential to dissolving coffee compounds in it.
Ew. Glad the article ended on a no. Coffee at home is not expensive enough to justify such madness. A pound of coffee makes about 7 8 "cup" (5oz) pots. I tend to get 4.5 mugs of coffee out of an 8 cup pot.
Even overpriced Starbucks at $10/12oz (~$13/lb) means that each mug of coffee is still only costing me around $0.35.
I'll brew with fresh grounds, thanks. You can _always_ add water if you want warm brown caffeinated water.
Buy cheap grounds in the biggest quantities you can store. I actually prefer Cafe Bustelo from local latino supermarkets (which is inexpensive, but not "cheap", it's really good!). Buy a coffee maker where no hot water touches plastic. Just glass and steel.
You will find that this gets you most of the way to great coffee.
I had this guy, and it lasted about 5 years. But you can do DIY pourover with similar results, electric or stovetop tea kettle + carafe with pourover:
Keep it simple, and good coffee is cheap. No need to re-use grounds.
I do have one use case for grounds re-use: If I want something hot to drink in the afternoon. I have good tolerance for caffeine (I have never become physically dependent), but I just have to keep caffeine consumption to before 3pm, or I might have a hard time sleeping. A re-run of the morning's grounds (usually 3 scoops of grounds), gives me coffee flavor, but without too much caffeine.
I confess that sometimes for a quick coffee I use the same espresso from the morning. I don't always feel like grinding beans, cleaning the portafilter, and tamping again. It's not great but not terrible.
Turn it into compost or leave a bucket of grounds outside long enough and you'll end up with a hearty colony of black soldier fly larvae that will consume up to 5lbs of grounds and organic matter per day.
BSF are fascinating, they prevent deadly pathogens reduce the volume of organic waste quickly and actually produce insect frass more nutrient dense than worm castings. Amazing little creatures!
I generally concur with sibling commenters' criticisms, but I still enjoyed reading this article. To me it's a light-hearted but nevertheless thorough exploration of coffee brewing. I love that the author attempts to answer a question that almost nobody was asking—simply out of sheer curiosity!
I am sorry, but I have to disagree. The stilted, repetitive, one sentence per paragraph style is so obtrusive and so reminiscent of blog spam that I could not focus on the content.
At the end of the day, all the author does is re-brew a cup of coffee with used grounds. Who has not tried that at least once (and went blegh and never tried it again)? To me, the article is as content-free as it is hard to read.
So the answers are about what you'd expect -- it's weak, cold brew is better but still weak, and who even knows if there's any caffeine in there.
But I still can't help but wonder out of sheer curiosity, to take this to the limit -- what about making cold brew but with 3x or even 5x or 10x the normal ratio of grounds to water?
Surely there's a way to get "reused" coffee to a comparable concentration to "first use". And then... would it be even remotely drinkable, or too much bitterness-to-flavor? Sufficiently caffeinated, or would comparable caffeine make it unbearably bitter?
I'm so curious now -- I feel like this blog post got 80% of the way, but is missing the final experiment!
For me, coffee tastes far superior when it is much more diluted than "normal". 1 liter French press with 2 tablespoons of grounds. Then put about 2 tablespoons of this liquid with 32 oz of ice water. It should now look like light tea. It's a refreshing beverage I can drink from 8am to 2pm with no downsides. This drink can be replicated at starbucks as "can I get a shot ... And a venti ice water with light ice". Then combine. Side benefit is they often charge much less than an Americano.
My batches of french press last 2 days, so in this way I suppose I am reusing the grounds.
totally agree with grandma : nothing wrong with a second, decaf brew.
my grandma, in the old times, used the burned crust from the home made bread for the morning coffee. peasants could not afford real coffee. it was similar to chicory coffee, not too bad.
I use a Chemex drip coffee maker and get pretty good results by halving the amount of grounds I use for subsequent cups. No idea about the caffeine content but the taste is not noticeably different.
With my grinder, a 12 second grind gives a good first cup. For the second cup I keep the spent grounds in the filter and add another 6 second grind. If I go for 3, another 6 second grind.
That works out to a 25% or 33% savings depending on number of cups (18/24 seconds vs 24/36). I've never tried carrying them over day to day.
I appreciate the author running these experiments; even though I think the answers were obvious, it does confirm a lot of what we know about coffee extraction.
I do have a few related thoughts on some different points in the article.
> The ideal extraction yield for coffee is between 18% and 22%. An under-extraction of 15% or over-extraction of 25% will cause an imbalance in the components and will result in either acidic or a bitter-sweet coffee drink.
The lower bound of the range is accurate, but the upper bound is outdated. People like Scott Rao and the folks at Barista Hustle have been involved in expereriments to push extractions even higher than that; if I recall correctly, I think they've reached just shy of 30% while improving the taste of the resulting coffee. The key is that bitter flavors don't simply start extracting past 22%, but that above 22%, the _evenness_ of extraction becomes very important. This is the point where factors like the grind size distribution (from the specific combination of beans, grinder machine, and burrs) and technique (e.g. your method of hand pouring to avoid fine particles from clogging the filter) really start to matter. Bitterness can even occur at 18% extraction if the grind size distribution is very uneven.
Another related detail the author mentions is that the second and third re-brews result in more watery cups. This is partly because fines (the tiniest particles) in suspension are major contributors to the texture of the coffee beverage, especially for espresso. Once you've extracted most of them in the first brew, there won't be much left for repeated brews.
My angle on this is that this is not a useful technique unless you're intentionally trying to ration coffee. If your repeated brews seem to extract some additional good flavor, you may want to explore ways to increase the extraction from the first brew instead.
On a related note, there is an old invention that essentially constantly rebrews coffee: the percolator.
Oof. This article is horribly painful to read. Tl;dr: it's exactly what you'd expect. Weak and not as tasty. Cold brewing it might work best. Less than half the caffeine of the first extraction. Don't let wet coffee grounds stay in the counter overnight to gather mold and bacteria before reusing.
I've been on a kick drinking black tea in the morning before I have coffee. Tea is a lot cheaper than coffee and I find a cup of it before coffee kind of primes my taste buds so the coffee tastes even more amazing.
For grocery-store commodity tea I agree. I find loose leaf teas can very quickly get more expensive than your average boutique coffee roast. Personally I usually just get Yorkshire Gold or something, which is not that expensive. I'm interested in trying more loose leaf varieties (particularly Japanese and Chinese) but I'm too cheap right now.
And for as much as I like tea, coffee is irreplaceable.
This is a valid technique if you do cold extraction (e.g. cold brew). I often reuse coffee grounds and mix them with fresh coffee when cold brewing with no particular downsides.
Cold brewed coffee also lasts much longer before going into "tastes like old coffee"-territory, you can have it in the fridge for weeks while hot brewed coffee can taste bad after a few hours already. It is said that the acids in the bean play a role in this, and those acids are not extracted during cold brewing.
There is people experimenting with ultrasonic extraction processes as well.
Yeah, that’s what’s missing here: experimentation on how to make it work.
I’ve tried this by re-using grounds, but also adding fresh grounds on top. (About half as much as i’d normally use.) It still comes out a bit watery, but much closer to normal.
> When reusing coffee grounds to make another coffee the next day you risk ingesting unwanted fungi and bacteria.
> These are attracted by the wet grounds and it’s possible that the microorganisms start establishing their colonies in less than 24 hours.
> Therefore drinking coffee that’s made from yesterday’s grounds could be potentially dangerous while also having an unpleasant taste.
Storing the spent grounds in the fridge would be a good preservation method.
Personally, I think putting boiling water in the grounds as an initial treatment should kill off any initial bacteria.
Fungal spores aren’t killed by boiling, but they might germinate after soaking and then get killed after the second hit. This was an early method of killing fungal spores before pressure vessels: tyndallisation.
Coffee grounds (without any sugar, etc.) isn’t a very nutritive media.
From experience, when it’s a bit humid here the pucks out of my espresso machine start growing visible mould in my knock box extremely quickly.
Sure, refrigerating them and keeping them in an airtight container would slow that but why risk it when all the good flavours of the coffee are already extracted?
The second boil wouldn't really help much with the food safety. The bacteria or fungi aren't themselves toxic, it's the waste they produce that is. And unfortunately those toxins aren't destroyed by boiling water.
But I agree that it should be fine if you put it in the fridge.
[+] [-] pessimizer|3 years ago|reply
This post took more effort than 99% of blogposts, calling it blogspam is pretty offensive.
It reminds me of another favorite article online: https://www.instructables.com/The-Science-of-Biscuits/
Sourced from: https://travisdanielbow.weebly.com/blog/category/cooking-exp...
[+] [-] Gigachad|3 years ago|reply
Turns out the espresso machine is already set up to stop extracting just at the point where all the good flavours have been removed. (Also reason to be thankful that the good flavours happen to extract first)
[+] [-] 2muchcoffeeman|3 years ago|reply
[+] [-] gchamonlive|3 years ago|reply
Those variables were:
- coffee/water ratio
- grind size and consistency
- water temperature
- extraction duration
But there is a fifth element that should be observed that is the water hardness. Having too much or too little magnesium and calcium disolved in the water may result in wildly different cups of coffee. Yes, that is leaning more towards the pedantic side, but if you live in a region with extremely soft water, you have to fix water hardness because it is essential to dissolving coffee compounds in it.
Water hardness graph: https://jgagneastro.files.wordpress.com/2018/12/water_coffee...
I would suggest reading How to make the best coffee at home, from James Hoffmann.
[+] [-] cpfohl|3 years ago|reply
Even overpriced Starbucks at $10/12oz (~$13/lb) means that each mug of coffee is still only costing me around $0.35.
I'll brew with fresh grounds, thanks. You can _always_ add water if you want warm brown caffeinated water.
[+] [-] RajT88|3 years ago|reply
You will find that this gets you most of the way to great coffee.
I had this guy, and it lasted about 5 years. But you can do DIY pourover with similar results, electric or stovetop tea kettle + carafe with pourover:
https://www.amazon.com/gp/product/B076VVTRNM
Keep it simple, and good coffee is cheap. No need to re-use grounds.
I do have one use case for grounds re-use: If I want something hot to drink in the afternoon. I have good tolerance for caffeine (I have never become physically dependent), but I just have to keep caffeine consumption to before 3pm, or I might have a hard time sleeping. A re-run of the morning's grounds (usually 3 scoops of grounds), gives me coffee flavor, but without too much caffeine.
[+] [-] jorgesborges|3 years ago|reply
[+] [-] sigil_my_ev|3 years ago|reply
BSF are fascinating, they prevent deadly pathogens reduce the volume of organic waste quickly and actually produce insect frass more nutrient dense than worm castings. Amazing little creatures!
[+] [-] cardamomo|3 years ago|reply
[+] [-] deepspace|3 years ago|reply
I am sorry, but I have to disagree. The stilted, repetitive, one sentence per paragraph style is so obtrusive and so reminiscent of blog spam that I could not focus on the content.
At the end of the day, all the author does is re-brew a cup of coffee with used grounds. Who has not tried that at least once (and went blegh and never tried it again)? To me, the article is as content-free as it is hard to read.
[+] [-] crazygringo|3 years ago|reply
But I still can't help but wonder out of sheer curiosity, to take this to the limit -- what about making cold brew but with 3x or even 5x or 10x the normal ratio of grounds to water?
Surely there's a way to get "reused" coffee to a comparable concentration to "first use". And then... would it be even remotely drinkable, or too much bitterness-to-flavor? Sufficiently caffeinated, or would comparable caffeine make it unbearably bitter?
I'm so curious now -- I feel like this blog post got 80% of the way, but is missing the final experiment!
[+] [-] ademup|3 years ago|reply
My batches of french press last 2 days, so in this way I suppose I am reusing the grounds.
[+] [-] momirlan|3 years ago|reply
[+] [-] HKH2|3 years ago|reply
[+] [-] ruined|3 years ago|reply
[+] [-] angry_moose|3 years ago|reply
With my grinder, a 12 second grind gives a good first cup. For the second cup I keep the spent grounds in the filter and add another 6 second grind. If I go for 3, another 6 second grind.
That works out to a 25% or 33% savings depending on number of cups (18/24 seconds vs 24/36). I've never tried carrying them over day to day.
[+] [-] vanilla_nut|3 years ago|reply
Considering how expensive and wasteful paper coffee filters can get, it's a nice optimization.
[+] [-] anonuser123456|3 years ago|reply
[+] [-] netfortius|3 years ago|reply
[1] https://en.wikipedia.org/wiki/Nechezol
[+] [-] kibibyte|3 years ago|reply
I do have a few related thoughts on some different points in the article.
> The ideal extraction yield for coffee is between 18% and 22%. An under-extraction of 15% or over-extraction of 25% will cause an imbalance in the components and will result in either acidic or a bitter-sweet coffee drink.
The lower bound of the range is accurate, but the upper bound is outdated. People like Scott Rao and the folks at Barista Hustle have been involved in expereriments to push extractions even higher than that; if I recall correctly, I think they've reached just shy of 30% while improving the taste of the resulting coffee. The key is that bitter flavors don't simply start extracting past 22%, but that above 22%, the _evenness_ of extraction becomes very important. This is the point where factors like the grind size distribution (from the specific combination of beans, grinder machine, and burrs) and technique (e.g. your method of hand pouring to avoid fine particles from clogging the filter) really start to matter. Bitterness can even occur at 18% extraction if the grind size distribution is very uneven.
Another related detail the author mentions is that the second and third re-brews result in more watery cups. This is partly because fines (the tiniest particles) in suspension are major contributors to the texture of the coffee beverage, especially for espresso. Once you've extracted most of them in the first brew, there won't be much left for repeated brews.
My angle on this is that this is not a useful technique unless you're intentionally trying to ration coffee. If your repeated brews seem to extract some additional good flavor, you may want to explore ways to increase the extraction from the first brew instead.
On a related note, there is an old invention that essentially constantly rebrews coffee: the percolator.
[+] [-] dgacmu|3 years ago|reply
[+] [-] qbasic_forever|3 years ago|reply
[+] [-] slothtrop|3 years ago|reply
And for as much as I like tea, coffee is irreplaceable.
[+] [-] kotaKat|3 years ago|reply
https://www.youtube.com/watch?v=39g6utADRzs
They're awful.
[+] [-] atoav|3 years ago|reply
Cold brewed coffee also lasts much longer before going into "tastes like old coffee"-territory, you can have it in the fridge for weeks while hot brewed coffee can taste bad after a few hours already. It is said that the acids in the bean play a role in this, and those acids are not extracted during cold brewing.
There is people experimenting with ultrasonic extraction processes as well.
[+] [-] baxtr|3 years ago|reply
[+] [-] markiannucci|3 years ago|reply
[+] [-] tdeck|3 years ago|reply
[+] [-] ryanwhitney|3 years ago|reply
I’ve tried this by re-using grounds, but also adding fresh grounds on top. (About half as much as i’d normally use.) It still comes out a bit watery, but much closer to normal.
[+] [-] Scoundreller|3 years ago|reply
> These are attracted by the wet grounds and it’s possible that the microorganisms start establishing their colonies in less than 24 hours.
> Therefore drinking coffee that’s made from yesterday’s grounds could be potentially dangerous while also having an unpleasant taste.
Storing the spent grounds in the fridge would be a good preservation method.
Personally, I think putting boiling water in the grounds as an initial treatment should kill off any initial bacteria.
Fungal spores aren’t killed by boiling, but they might germinate after soaking and then get killed after the second hit. This was an early method of killing fungal spores before pressure vessels: tyndallisation.
Coffee grounds (without any sugar, etc.) isn’t a very nutritive media.
[+] [-] stephen_g|3 years ago|reply
Sure, refrigerating them and keeping them in an airtight container would slow that but why risk it when all the good flavours of the coffee are already extracted?
[+] [-] antognini|3 years ago|reply
But I agree that it should be fine if you put it in the fridge.