Stirring Coffee Effectively

  • Thread starter Thread starter Hornbein
  • Start date Start date
Join the discussion
Registration is free. Ask a follow-up in this thread, or start your own.
Sign up Log in
37 replies · 5K views
Hornbein
Gold Member
Messages
4,138
Reaction score
3,300
I noticed that the stirring of coffee was ineffective. There's always a layer of too-sugared liquid near the bottom. So...stir it vertically instead of swirling the coffee horizontally.
 

Discussion

Physics news on Phys.org
There is a whole discussion in coffee media if one should swirl or stir (but is mostly related to getting an homogeneous espresso and is it not about sugar).
 
Hornbein said:
So...stir it vertically instead of swirling the coffee horizontally.
Maybe, you need a semicircular plate, attached to a rod that is on the axis of the circle. Push it down, rotate the stick and lift it up to generate an efficient vertical circulation.
 
See?! Another contender for the geeky trophy! :woot:
 
Hmm. No. Admittedly not. I retract my opnion.
 
And technically it is a physics problem.
 
sbrothy said:
And technically it is a physics problem.
Altough even if the problem is technically a valid STEM problem I’m sure you’ll agree it can get out if hand!
 
Still my geeky trophy is just a joke
 
Hornbein said:
I noticed that the stirring of coffee was ineffective. There's always a layer of too-sugared liquid near the bottom. So...stir it vertically instead of swirling the coffee horizontally.
Incomplete premise.
Even if you stir the coffee until it is completely homogenous, it will still end up with sugar on the bottom. The sugar does not always completely dissolve, so it settles on the bottom over time.

Sugar in liquid is more typically a suspension, rather than a solution.
 
martinbn said:
Why do you put sugar in your coffee!
Because coffee is objectively disgusting-tasting (caffeine-rush-notwithstanding), and it is simply a matter of how much sugar and milk one need to put in it to make it tolerable.
 
Reply
  • Like
Likes   Reactions: phyzguy, Office_Shredder and Hornbein
In a cafe, James Bond is always asked if he would like his coffee stirred or shaken.
 
Reply
  • Like
Likes   Reactions: Office_Shredder
martinbn said:
Why do you put sugar in your coffee!
Because it is an inferior coffee. Adding and dissolving sugar in the brewed coffee just makes this brew sweeter in an often/sometimes ineffective attempt to cover the poorer flavor. But this is at least in part my opinion.
 
DaveC426913 said:
Because coffee is objectively disgusting-tasting (caffeine-rush-notwithstanding), and it is simply a matter of how much sugar and milk one need to put in it to make it tolerable.
That kind of understanding may change once you learn to roast high quality coffees yourself and to brew it. NO sugar needed.
 
symbolipoint said:
That is difficult to believe.
Why?
To get all the sugar dissolved in a liquid requires a sufficient stirring time as well as making sure you don't oversaturate it (in which case it may never fully dissolve) - neither of which are guaranteed in a real-world scenario.
 
symbolipoint said:
That kind of understanding may change once you learn to roast high quality coffees yourself and to brew it. NO sugar needed.
I never drink hot liquids.
OK, once a year, in Cuba, I have a Spanish Coffee.
I do drink iced coffee occasionally, but it's so sweet and milky it might as well be a milkshake.

But even high quality coffees are still at the far end of my scale of tasty.

I think it may be a genetic thing - like Brussel's Sprouts and coriander.
 
DaveC426913 said:
Why?
To get all the sugar dissolved in a liquid requires a sufficient stirring time as well as making sure you don't oversaturate it (in which case it may never fully dissolve) - neither of which are guaranteed in a real-world scenario.
A coffee drinker typically will not oversaturate his coffee with sugar. As we were taught, sugar is a compound (or two compounds) soluble in water, or close enough, hot brewed coffee. Must we try to dissolve one teaspoon of sugar (sucrose which we can buy from a grocery store in bags) into one cup of water with mixing for two or three minutes until clear, and cover this and watch for undissolved settled material over some few number of hours?

Borek, do you have something to say about this?
 
DaveC426913 said:
I never drink hot liquids.
OK, once a year, in Cuba, I have a Spanish Coffee.
I do drink iced coffee occasionally, but it's so sweet and milky it might as well be a milkshake.

But even high quality coffees are still at the far end of my scale of tasty.

I think it may be a genetic thing - like Brussel's Sprouts and coriander.
OK it could be genetic. In case you know somebody locally to you who buys and roasts green unroasted beans at home and brews and drinks what he roasts, check for yourself about how the brewed coffee tastes and smells.
 
symbolipoint said:
Must we try to dissolve one teaspoon of sugar (sucrose which we can buy from a grocery store in bags) into one cup of water with mixing for two or three minutes until clear, and cover this and watch for undissolved settled material over some few number of hours?
Depends on what criteria you want to satisfy.

Hornbein's verdict is that the last sips are more sugary. So in a real world scenario - yes - it is entirely plausible that a true solution is not achieved in a realistic timeframe.
 
DaveC426913 said:
Depends on what criteria you want to satisfy.

Hornbein's verdict is that the last sips are more sugary. So in a real world scenario - yes - it is entirely plausible that a true solution is not achieved in a realistic timeframe.
I am still hoping Borek will tell us what we want to know and understand.

Something I very clearly notice is that HOT coffee (what I brew , at least) has less flavor and the flavor level and quality improves as it cools. When I am half way through, flavor becomes richer, and sweeter. I really do not believe this observation supports what Hornbein said how you explain it about it. I believe that the brew's resting and temperature drop affects how we find it.

I should also add, I never add any sweetener to the coffee I drink.

edit: Rewording for compositional reliability
 
DaveC426913 said:
I never drink hot liquids.
Ginger tea is best served hot.
 
symbolipoint said:
I am still hoping Borek will tell us what we want to know and understand.

Something I very clearly notice is that HOT coffee (what I brew , at least) has less flavor and the flavor level and quality improves as it cools. When I am half way through, flavor becomes richer, and sweeter. I really do not believe this observation supports what Hornbein said about it. I believe that the brew's resting and temperature drop affects how we find it.
Definitely true. It has been found* that, objectively, the best temperature for tasting things is luke warm. (But that does not mean it is subjectively the most enjoyable).

Regardless, the two phenomena - optimum temp and adequate stirring are not mutally exclusive factors.

I'm not sure I get your stance. Are you asserting that - in a real word scenario, such as the OP's - it is implausible that sugar may settle to the bottom of a coffee cup? You won't be convinced unless that is proven to your satisfaction ?

*citation needed
 
256bits said:
Ginger tea is best served hot.
Yes. And I don't drink ginger tea. Because it is hot.

As I type this, I am out in my Dave Cave smoking a stogie. The temp is below zero (Celsius). I have three heaters pointing directly at me, so it's warm enough for me. And I am still drinking an iced beverage. In a double-walled thermos so it doesn't warm up.

1000010651.webp


The only time I am ever caught drinking a hot liquid is if I am out in the snow for hours at some winter event, and then I will partake of the occasional hot chocky.

Also, I'm not fond of soup for the same reasons.
 
symbolipoint said:
A coffee drinker typically will not oversaturate his coffee with sugar. As we were taught, sugar is a compound (or two compounds) soluble in water, or close enough, hot brewed coffee. Must we try to dissolve one teaspoon of sugar (sucrose which we can buy from a grocery store in bags) into one cup of water with mixing for two or three minutes until clear, and cover this and watch for undissolved settled material over some few number of hours?
Water can take up to about twice its volume in dissolves sugar to saturation. Syrups are quite much just about saturated sugar in water.
Honey may develop crystals as the sugars come out of solution, but that is most likely some other chemistry as the water has not evaporated from the jar.

Surface area is important. A cube of sugar presents less surface area to the water than a powdered form. From the sugar cube surface, there is a gradient of concentration of dissolved sugar molecules to far away fresh water. Stirring will bring fresh water to the sugar cube surface enhancing the rate of dissolving, but a gradient nevertheless still exists.
A few stirs of the coffee will not be enough to dissolve all of the sugar cubes, which will then settle to the bottom of the vessel, where upon the gradient of dissolution is from bottom to top, leaving the bottom more sweeter than the top.
 
If you stir in sufficient sugar, to saturate hot coffee, then you must expect to initially add more solid sugar than is needed, or it will not achieve saturation while stirring.

As the coffee then cools, and the Ksp falls, sugar will continuously precipitate out of solution, adding to the initial excess of solid sugar.

I feel sorry for those unfortunate people, who add sugar to make their poor quality coffee drinkable. Visitors to Australia are often surprised by, and comment on, the higher quality of the coffee available. I guess that partially explains why tourists, when they first arrive here, are in the habit of adding sugar to their coffee. It also suggests that Australia competes on taste and smell, while the rest of the world is competing on profit margin. I have never attended a "Star-bucks", but it seems like an excellent name, for selling shares to US investors.
 
If you must for some reason sweeten your coffee with sugar then either make simple syrup like bartenders do (much harder to dissolve sugar in a cold drink) or warm up the crème/milk and dissolve it there first

Or if you use a French press like any one with self respect does, dissolve it in the hot water before pouring on the grounds