The chemistry of cold-brew coffee is so hot (2020) | Hacker News Reader

The chemistry of cold-brew coffee is so hot (2020)

arstechnica.com

89 pointsTomte60 comments

Before you go to bed tonight: put a bunch of big spoonfuls of coffee grounds into a French press, add water, and stir. Into the fridge. Then put some oats into a big cup. Pour in milk til they’re “swimming”. Put that in the fridge.

When you wake up, press the coffee grounds out and pour that into a thermos. Put some honey in the big cup of oats and throw a spoon in there. Now you have the best breakfast and coffee to go, and it’s so easy it feels like cheating.

Shouldn't you use scale for anything coffee related? Spoon is cursed word in coffee world as well as preground

As someone with a scale for coffee: cold brew is very uncritical in terms of amount. Use more and you end up with a more concentrated liquid, use less and you get a more watery thing. Many people also make a concentrated cold brew and then add water to taste.

These are all things that come close to a sin with hot brewed coffee, but cold brewing is different.

> These are all things that come close to a sin with hot brewed coffee, but cold brewing is different.

I’d say French Press brewing is also very forgiving regarding the amount and quality of the grind. A lot of people forget that not everyone uses an espresso machine for their coffee (probably the least forgiving method of making coffee)

Sure it is, what I said is that most other hot brewing methods are more critical to differences in coffee amount than cold brew methods, not that all of them are totally critical.

I didn’t mean to contradict you. Only to add ;)

I used to be able to tell the difference between pre- and freshly-ground. These days I really don't care that much; you can still get decent results. Similarly weighing the coffee is going to be more accurate, but it's not as crucial as in espresso or moka where you the amounts are small and significantly affect the resistance to the flow.

What matters far more than freshly ground is freshly roasted (<1 month, > a few days) and grind size for the type of coffee

Not all of us coffee drinkers are that OCD about it.

For espresso it’s vitally important. One extra gram of coffee takes it from smooth, sweet and acidic to being extremely bitter and unpleasant. It’s not just people being snobs, it’s just espresso is very sensitive to tiny changes.

Obsessive compulsive disorder isn’t like that. Obsessive would have worked, but OCD is a very poor way to describe this.

I mean the colloquial usage of OCD.

In that case, I’d likely suggest you don’t use medical diagnoses in that way. OCD sucks dude. Its kind of like having your nervous system set on fire.

Sorry if I've offended you.

I dump the cheapest grounds I can find into a mesh bag and put it into a gallon of water overnight, tastes completely fine

Scale? Spoon?

I just grab a handful of beans and chuck them in my hand grinder. The amount I can hold without dropping any beans seems to be just right for one cup of cafetiere coffee.

Never tried cold-brew; maybe I'll make some this evening, and try it tomorrow.

People like what they like. It’s likely your grinder isn’t up to my standard. But I’m not going to put it down for no reason.

Are graduated spoons allowed ?

I like to use mason jars instead of a french press, I'll make a week's worth of cold brew on a weekend night. You do need to drain it through a coffee filter though. I just dump them into a pourover coffee pot with a re-usable metal filter.

I have a mason jar with a sealing metal filter insert. Very low effort, you simply remove the filter, rinse the lid, and close the jar again :)

You may have just changed my life. Or at least my Sunday afternoons.

If you are more into tea, cold brew tea is also a thing and very nice. This actually works with most varieties of tea but is especially nice with white or green tea. Rooibos is also a nice one to try. Simply steep a jug of cold water with some tea in the fridge and leave it for 12 hours or so. Very refreshing and it typically has a sweeter/less bitter taste than normal tea. I don't add any sugar/honey so it's healthy too. But of course you can if you want.

I also drink coffee sometimes but mostly green tea these days. I get my tea from a Pakistani supermarket in Berlin that sells it in bricks of half a kilo. I drink about a liter of that in the morning. When I drink coffee, it's mostly at nice coffee shops. We're very spoiled with those in Berlin.

I've always seen it done at room temp and called sun tea.

My French Canadian grandmother made:

- Sun tea (room temperature and during the day).

- Moon tea (room temperature and during the night).

- Fridge tea (refrigerated).

She passed away over thirty years ago so do with this what you will, but I’m convinced I could tell the difference. Who knows though.

I make sun tea too, but it involves.. the sun, on my back porch.

Aren’t you concerned about the high fluoride and heavy metal content?

https://www.researchgate.net/publication/322924754_Green_Tea...

No? To be honest this is the first I'm hearing of this. This paper reads like a loose collection of tea-adjacent statements vaguely cited - doesn't particularly inspire confidence in any kind of 'conclusion'.

A cursory glance at a few other sources suggests you'd have to consume on the order of 10,000 times the amount in a glass of tea to get adverse effects. Seems about as toxic as caffeine.

> ...drinking of the studied green teas cannot make a significant contribution to the daily dietary intake of F for consumers.

https://www.ncbi.nlm.nih.gov/labs/pmc/articles/PMC4811265/ https://pubmed.ncbi.nlm.nih.gov/33350950/

"Fluoride is a chemical castration agent..."

Yeah, gonna guess that's not a reputable publication.

The paper you've linked seems to be written by a crackpot with no training in biology, nor was the paper published in any journal, much less a reputable biology/medical one.

You have to drink a lot of older tea leaves from specific areas to have any real concerns about this.

Gunpowder green tea is a common version that carries more F than others but most casual drinkers will never come near levels to cause physical concerns.

Yes, fluoride and acrylamide are the reasons I avoid tea and coffee. You can replace tea with water and lemon, and coffee with modafinil.

What brand do you buy from the supermarket?

The Hario bottle has been my go to method for cold brew last couple years. It’s incredibly easy to use. Cold brew is so much easier on an empty stomach when I want to get some caffeine before my long runs.

I tried for years to make cold brew taste like Starbucks - going for black and unadulterated by milk/cream. Tried french press and all sorts of ways hot and cold, overnights in the fridge, etc.

The closest i've gotten is with an espresso machine making a 'Lungo' which is more or less an espresso pull with far more water through it than what you'd do for a shot. No ice on this while making. Just put the glass/mug in a freezer for 30-60 minutes (if you can plan ahead) and then pour over ice.

https://en.wikipedia.org/wiki/Lungo

Unfortunately Starbucks doesn't package their cold brew blend as a bean, so I'm not sure how to replicate that, but otherwise here's the recipe:

5lbs of Coffee steeped in 14 liters of water for 20 hours at room temp. Remove grounds and you have concentrate good for about a week. Cut that 1:1 with cold filtered water and serve over ice.

They use a big tub with a giant paper filter, but you can scale it down and do it in a French press or a mason jar and cheesecloth or whatever is handy for you as long as the grounds are submerged in the water and easy to remove.

No, this is an Americano, stretched coffee. For cold brewed coffee put the grounded coffee into cold water, let it rest (over night or even longer), filter the coffee, enjoy.

Coffee tastes differently when done this way. You might want to use a different type of coffee than for your espresso - or not.

It's not an Americano. An Americano is a shot (or two or more) into a cup and then hot water poured on top.

After reading the above comment again, I have to admit I misunderstood what he/she was doing.

A very different drink, but I can recommend a big cup of ice cubes, an espresso over that and top it up with oat milk.

Is so good on a hot day.

I changed from pour over to cold brew around a year ago thanks to a recommendation of my co-worker. Can't go back to hot coffee now, I enjoy it way too much. Somehow it's much more forgiving than pour over coffee and super easy, too. Hario (and many others) sells some glass pitchers with filter. You put them in the fridge overnight and have great coffee in the morning.

I tried cold brew a couple of times, but for some reason didn't like it. It tasted different.

But, I had had it cold, when I generally drink hot coffee. Does it taste similar, but better, than hot coffee when cold brewed coffee is heated?

Also, how do you heat it? I'm assuming microwave is the best option..

Curious before trying it again :)

A local coffee roaster with a coffee shop offered cold brew a few summers ago, one of those when it was really hot. They stopped because it was too much work.

I drank it like whisk[e]y - in a similar glass and on ice (okay okay, ice and whiskey may not be a valid combination for everybody, but let's not get distracted, I used the image only for illustration). It was much more concentrated than normal coffee, and it tasted great! Very different from usual coffee and espresso. It also was a perfect drink during those hot summer weeks. I deeply regretted the apparent incompatibility of the commercial needs of the shop with this drink.

Going by the taste I experienced, and since they are a small roaster they always have new types of beans so I had several very different ones, I see no reason to heat this even if you don't drink it in a hot summer.

EDIT: [German] Looks like they sell it in bottles prepared in batches from their main store now, instead of day (night) in small daily batches: https://www.facebook.com/roesttrommel/photos/a.1510286749418... -- They write "Schmeckt am besten eisgekühlt." which translates to "Tastes best ice cold."

I reheated cold brew with a microwave and liked it. I think you can get some very tasty coffee with cold brew even with cheaper beans.

I heat just the water in a mug in the microwave then pour in the cold brew coffee and stir.

FYI - French presses raise Ldl in humans.

https://www.healthline.com/health/high-cholesterol/coffee-li...

"...raised cholesterol levels shouldn’t be much of a concern..."

"There’s no significant connection between coffee and increased risks of heart disease and cancer."

And, by far the most important quote: "Talk to your doctor to about any concerns you have."

Before your first quote is "Unless you’re drinking significant amounts of unfiltered or French press coffee on a daily basis"

And considering I drink about 1 liter of French press coffee every day, it might actually be of concern to me.

I'm in the same boat and switched to Aeropress. It has marginally reduced my cholesterol in 3 months. My diet didn't change significantly in that time except that I started eating oatmeal regularly in the morning instead of granola. So totally unscientific, but I'm going to continue with the change.

Just be sure to use the paper filters and not the reusable metal ones. Only the paper filters remove the oils responsible for raised LDL.

A side benefit is that Aeropress coffee tastes great! I highly recommend it.

The thing is, I fear I like the coffee oils I get more of with no paper-filter. I assume it’s one of the reasons French press is my favorite method of making coffee.

You can test this hypothesis pretty easily since coffee oil is a surfactant. Get freshly roasted beans (ideally less than 2 weeks) and make your French press. Once the brew is ready, skim off the foam on the top and you will have removed a significant amount of the oils from the coffee. Be sure to taste blind, ideally using the triangle method.

Edit: see also the studies about cafestol being strongly correlated with lower risk of renal cancer. This is a very complicated subject and the analysis of it should be done in concert with real medical professionals.

https://pubmed.ncbi.nlm.nih.gov/34677742/

If, like me, you'd never heard of LDL, read this:

https://www.healthline.com/health/high-cholesterol/why-is-ch...

https://youtu.be/nsISdNl2tWo

This is a part 4 vid. Parts 1-3 are linked below it.

https://youtu.be/GC9V1TWYLo4

Yes I've also heard the paper filter removes some toxin from the bean (which has very small amounts). Is this related?

Yes

I’ve tried cold brew from a few different sources and it’s awful, I had to throw it out. I must have different genetics or something affecting my taste.

Who’d have thought that drip coffee that’s been sitting around for hours and hours is not as good as fresh.

Do you warm the cold brew coffee up or drink it cold?

Either or? Sometimes I drink it cold and other times I’ll heat it up. It depends on my mood.

Heated up is when I think I taste the biggest difference but sometimes I wonder if I just think it tastes good because I spent a whole day waiting for it…:)

Depends on the season. In the summer months, I like to add it to milk and, maybe, ice. In the winter, I add hot water. Cold brew coffee is often stronger, so drinking it straight (heated or cold) is a good way to end up jittery.

I drink cold brew everyday winter and summer!

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