does anyone out there have an explanation for exactly what happens to a shot of epresso poured directly over ice? i feel a little lost because i've tasted both ways and sometimes there is a huge difference, sometimes there isn't. it seems to correlate more with the barrista and the particular blend they are using rather than a hard and fast rule that pouring directly over ice "shocks" it. i haven't been able to find anything to truly(scientifically) back up either way. is there anything to back either one up?

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Excellent question. I'd love to get some science on this as well.

One thing I do know is that when I make an iced latte, I put foam over the ice before adding espresso on top of that, and it makes a massive difference. I never thought that it would be so definitive, but I done multiple taste tests and each time the difference is marked.
The real trick is cold brewing a concentrate for iced coffees. Lower acidity and smoother taste really make a difference in an iced drink. The acids and essential oils that are released when espresso is extracted under pressure and temperature taste great in a hot drink but can become unpleasant in a cold drink where the milk isnt steamed either. Cold-brewing allows for a long shelf life, smoother taste and a totally different flavor profile that is great.

Just my two cents...
what happens when you pour melted butter or chocolate onto ice? something similar probably happens to espresso. at least to the parts that are oils.
I have no proven explanation, just some musings. I'll say first that I no longer agree with the idea that you are "shocking" the espresso when pouring over ice, but am open to discussion on this.

As I understand it, our perception of sweetness drops as something cools. I believe that when a shot is cooled the sweetness we perceive (that would ordinarily balance a shot out) is reduced - not a physical change in the espresso itself. So it makes no difference how fast you cool it, only that its now cold. I think that what we are actually seeing here is that the window for producing a shot that will taste good cold (regardless of how gently it was cooled) is just much narrower than for a regular (hot) shot. You'd have to have a shot of a certain acidity, loads of sweetness, and no perceptible defects for it to taste really good cold. It probably would taste terrible hot.

The test I've done to see what the "shock" amounts to was to make a pair of iced americanos:

Split a double, pouring one shot over ice, then strain out the ice and pour into a measuring cup, noting the level. Pour the other shot into another cup and add ice-cold water to it to reach the same level (and same dilution). Then pour them both over ice to make a pair of drinks of the same temperature and concentration. The "shock" theory would suggest that you'd have damaged the shot poured over ice. So you should be able to taste the difference, right? If you taste both drinks, you'd be hard-pressed to tell them apart (at least in my experience).

I'd say before we look for the reason why espresso is "shocked", first we need to prove that this actually happens. I've tried and can't, so am accepting the other possibility (that there is no shock) until I taste otherwise.

Looking forward to other thoughts on this... anyone?
jon stovall said:
what happens when you pour melted butter or chocolate onto ice? something similar probably happens to espresso. at least to the parts that are oils.

Ummm... they solidify. Ever had that happen to a shot?
I think what he is saying is that the coffee oils in the espresso do solidify. So in that sense, yes, I have had that happen.

One theory about the difference in flavor concerns the C02. It may be that reason seltzer water tastes funny after the C02 leaves is the same reason that espresso takes on a certain flavor when it hits directly on the ice. Again, there is no test data other than anecdotal. I can't explain the theory much beyond that, just that the presence of C02 in water can taste pleasant under certain conditions, and have a negative effects under other conditions within the same beverage.

If you are getting inconsistent results while taste testing different iced drink procedures, it is probably due to inconstant preparation. Those who profess a distinct and unpleasant result from pouring espresso on ice are those with extreme consistency.

In any case, what's the big fuss? If you don't want to pour your espresso in the cold milk or chilled water first, and you only want to pull shots onto ice, and you can't tell the difference in quality from one drink to another, then just do it.

James Bond always wants his Martini shaken, not stirred. Did you know that some bartenders refuse to shake a Martini? It is said to "bruise" the ice. That is a little misleading. The ice chips a little bit and leaves small ice bits in the Martini, which will melt and water down the flavor. So a proper Martini is stirred, not shaken. But hey, if you want it shaken, who's gonna stop you?
Not a big deal, just seems like an opportunity to discuss a common problem. At very least maybe we'll all better understand what is going on... at best maybe we'd figure out a way to have an iced espresso that wasn't so disappointing.

For the record, I don't happen to like a shot poured over ice. I just don't think its because the shot was damaged in the process of being cooled so rapidly. I kinda think its maybe just the way fresh, cold espresso tastes. I'd love to find out that it was just that I was doing something wrong though...
The process I currently use and train my fellow baristi to use is to add the shot to the milk or water first, in a tumbler, give it a good stir, add the ice slowly, shake momentarily in the tumbler (sorta like a "shakeretto") and proceed to serve. Never had any complaints and I've personally never been dissatisfied, although I don't really drink iced espresso drinks on any sort of regular basis any more. Iced drinks are rather sketchy considering that it's simply adding another variable to the brewing process that could be hindering the quality of a given espresso.

I'm super curious to see if this thread carries on, some supporting science one way or the other would be super sweet. I'm not really sure how to go about developing a scientific theory on the subject though, seeing as it is truly by taste test that one determines whether or not the drink is worthwhile.
I've never noticed a difference with iced espresso drink, but blended (like in a smoothie, frappe, or whatever you call yours) I have always added the shot post-blend.
that doesn't work if you're just doing a shake with pure ice cream, espresso, and chocolate haha. you'll break your blender.

Branden said:
I've never noticed a difference with iced espresso drink, but blended (like in a smoothie, frappe, or whatever you call yours) I have always added the shot post-blend.
I've done the same thing and gotten the same conclusion. No difference when poured directly over ice.

Brady said:
I have no proven explanation, just some musings. I'll say first that I no longer agree with the idea that you are "shocking" the espresso when pouring over ice, but am open to discussion on this.

As I understand it, our perception of sweetness drops as something cools. I believe that when a shot is cooled the sweetness we perceive (that would ordinarily balance a shot out) is reduced - not a physical change in the espresso itself. So it makes no difference how fast you cool it, only that its now cold. I think that what we are actually seeing here is that the window for producing a shot that will taste good cold (regardless of how gently it was cooled) is just much narrower than for a regular (hot) shot. You'd have to have a shot of a certain acidity, loads of sweetness, and no perceptible defects for it to taste really good cold. It probably would taste terrible hot.

The test I've done to see what the "shock" amounts to was to make a pair of iced americanos:

Split a double, pouring one shot over ice, then strain out the ice and pour into a measuring cup, noting the level. Pour the other shot into another cup and add ice-cold water to it to reach the same level (and same dilution). Then pour them both over ice to make a pair of drinks of the same temperature and concentration. The "shock" theory would suggest that you'd have damaged the shot poured over ice. So you should be able to taste the difference, right? If you taste both drinks, you'd be hard-pressed to tell them apart (at least in my experience).

I'd say before we look for the reason why espresso is "shocked", first we need to prove that this actually happens. I've tried and can't, so am accepting the other possibility (that there is no shock) until I taste otherwise.

Looking forward to other thoughts on this... anyone?
The difference here is that the oils in coffee are water soluable. While most times oil and water don't mix, this is not so with the oils in coffee.

jon stovall said:
what happens when you pour melted butter or chocolate onto ice? something similar probably happens to espresso. at least to the parts that are oils.

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