Comment by denton-scratch | Hacker News Reader

Comment by denton-scratch | Hacker News Reader

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I've never drunk cold-brewed coffee. According to the article, cold-brew has "less acidity and bitterness".

I happen to like coffee with fruit and citrus tones. I'm not a coffee bore, but I have understood that coffee bores refer to that fruitiness as "acidity". Does that mean that cold-brew would be less fruity? The authors take "acidity" to mean "pH", which is obviously easier to measure than "fruitiness", but I wouldn't describe the taste of e.g. spirit vinegar as "fruity".

Supplementary question: why's it got to be a picosecond laser? They say that a nanosecond laser's pulses are too long, and cause heating. How hot does it have to get for that to be a problem? Can't you just cool the brewing vessel?

Supplementary supplementary: can apparatus for doing this be built at home? How much ps-laser power needs to be delivered to the brew? At what wavelength? You can get handheld picosecond lasers for things like mole and tattoo removal, for under $100; would one of those do the trick?

You cannot get picosecond lasers for under $100, not even under $1000. Those devices that you see are dangerous diode lasers that do not work for the advertised application, lie about their specs and are supplied without adequate eye protection. Youtuber Styropyro made a video about them here https://youtu.be/DbzbIGkPW-o

Thanks for that! So those devices on Amazon are just powerful diode lasers that switch on and off ten times a second - they're not even millisecond pulsed lasers.

That powerful beam looks like (dangerous) fun; I've always wanted a laser that can burn things. My inner arsonist would like to be able to set things on fire from 100m. But I'm sure the device must be illegal here.

Styropyro says you can damage your eyes just by looking at the projected laser spot. I wonder whether he's exaggerating his warning a bit.

OK, so no homemade picosecond-laser coffee for me any time soon.

The warning is *NOT* exaggerated. It is incredibly easy to damage your eyes with these tools.

I bought a cheap cat toy laser on amazon that was so powerful our eyes hurt just from testing the thing on our light gray walls etc. Some things are not worth messing around with.

Not sure what you’re being downvoted but Styropyro is correct. There’s one other aspect that people don’t talk about and that’s Q-pulsing. When you turn on 10W diode, the room gets pretty bright from the stray light. The moment you turn on Q-pulsing, the room glows uncomfortably bright, even with eye protection

Besides just diodes, there’s also the Q-pulsing aspect (hence the pico and fempto part of laser nomenclature)

> I happen to like coffee with fruit and citrus tones.

That would likely be seeds of Coffea arabica - one of three coffee plants. Those tones come from a specific plant rather than a brewing method or temperature.

The other popular is C. canephora (robusta coffee) which is almost globally (outside espresso world) considered as inferior to arabica and cheaper. Robusta has some chocolate and nut aromas but some people would say that it resembles burned rubber stench.

The third plant - C. liberica - is very rare in comparison. To me it has a somewhat woody/smoky/fruity aftertaste but I have only tasted beans from two roasters so far.

Most of store-bought ground coffee are arabica/robusta blends so people can enjoy full taste spectrum but aren't discouraged by the burned rubber thing.

I, on the other hand, LOVE robusta and my morning ritual of throwing mainly robusta roast (currently from Harley Estate in India) with 5-25% arabica seeds of choice into coffee blender is the best and most benefiting first decision making process I can imagine in the early morning.

When people talk about the flavor of "third wave" specialty coffee, they are talking about C. arabica.

The current US Barista Champion (Morgan Eckroth) did use C. eugenioides in one of her beverages, but that is still priced out of reach for all but the most dedicated enthusiasts.

Robusta is only used in "traditional" espresso blends (meaning the original Italian style) or, stereotypically lower quality products. (Edit: not to denigrate anyone's choice of using Robusta in their morning cup - please do whatever you enjoy the most.)

The thing about arabica is that there are many different varieties, from Ethiopian heirlooms to Typica, Bourbon, Pacamara, Gesha, etc. They are grown in varied soils, elevations, and climates. And as a sibling comment points out, the "natural process" and experimental fermentations are becoming popular because of the secondary flavors imparted. (Though my view of the scene is that most snobs still scorn natural process coffees for lacking cleanliness).

The brewing method and temperature will ABSOLUTELY alter the flavor tones of the cup. And the quality of grinder is the most important factor by far. Tweaking grind size can take you from a flat, mediocre cup to something with distinctive flavors and sweetness.

I've noticed that espresso barristas seem to favour robusta.

> Those tones come from a specific plant

No doubt; but I'm sure that "terroir" and growing conditions are also important.

Also, from what I can tell there are two ways of separating the berry-pulp from the bean: mechanical separation and wet fermentation, which create different flavour profiles.

The two I'm alternating at the moment are both pure arabica, both from East Africa, and both high-grown; but they seem to be processed differently.

You might enjoy Japanese iced coffee.

I find that cold brew tastes the same no matter the quality of coffee (therefore great for lower quality coffees) where as Japanese iced coffee retains the original notes of the coffee.

Is it any different from espresso fredo? In South Korea they drink iced americano, which is espresso dilluted with water and then dilluted with ice. In Greece I always drink espresso fredo as most shops will make a good cup and frappe is just not my cup of coffee.

What’s the recipe?

PS: ofc I could google that. But then again google results these days are…

It's a pour over method [1]

You can also use a regular drip machine though. Use half the normal water. Add the equivalent ice (by weight) to the flask. Brew as normal, but turn it off as soon as it's finished. The slow drip of hot coffee is cooled immediately as it hits the ice.

Since the brewed coffee is cold, you can add extra ice to your cup without it melting and diluting the taste too much.

Adjust the water / ice ratio as desired.

[1] https://www.youtube.com/watch?v=Y3jxJv5UiPg

I wonder if extracting the coffee with half the water and then diluting it gives a different result than just brewing at normal strength?

It is different but still tastes fresh and robust

It really depends what coffee beans you are starting with, and the roast, just as it does with "regular", hot brewed coffee.

I also like lighter-roasted fruity beans, and cold-brewed tends to reduce the "sourness". IMO cold brew really shines for non-fruity beans though, greatly reducing the bitterness.

You should try it!

Hmmm. I've been alternating Ethiopian Harrar with Kenya AA. I buy them ready-roasted - I don't know how to characterise the roast other than "medium" (the beans don't glisten with oil). I alternate specifically to catch the fruity aroma, which seems to my jaded old palate to fade after a week of the same bean.

Fruity varieties are almost always a light or medium roast - often you can see this in the colour of the roasted beans, which will be much lighter; I'm colour blind, but I think they're more brown/tan than black.

Earlier this year I had a cold-brewed coffee from a local coffee shop that tasted more like lemonade (unsweetened) than coffee. It was bad, and I'm not sure if the cold-brew was the exact trigger or just the final nail but I haven't had any other coffee in the months since then despite drinking coffee multiple times per day for years and years.

I'm so sorry that this happened to you. It legitimately sounds like you were either pranked or offered a product that contained something humans are not intended to drink.

There's absolutely nothing about cold brew coffee that is anything like unsweetened lemonade. I'm cringing just reading this.

What it does taste like is super-strong coffee, with none of the burnt note that comes with heated coffee. It could very easily be considered "too strong" by supertasters... but unsweetened lemonade sounds like dishwater.

The "burnt note" doesn't typically come from the brew method, but rather how darkly the beans have been roasted.

Light roasted (aka "Nordic" or "third wave") beans will produce more acidic cups because of their different chemical components. They are also less likely to taste burnt or astringent.

Lots of coffee shops think that tannic, acidic coffee is good coffee.

For those in the bay area, Red Rock in Mountain View has this issue with their brewed coffee. It's often downright sour.

Yeah it's going to tone down the fruitiness, though some may remain depending on how fruit-forward your coffee is.

A lot of people say cold brew is fruitier. I'd give it a shot if I were you

It depends on the cold brew, they all have different tastes.

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