Anybody else have trouble telling sour from bitter apart?

Want to talk espresso but not sure which forum? If so, this is the right one.
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Postby pavman » Nov 05, 2010, 1:38 pm

(Espresso-wise, specifically, of course).

For me, if the shot is clearly over extracted, i.e. the pull is close to choked, the coffee dribbles out instead of streams, the shot is extra bubbly and globules make it look like an oil slick (forgive me if my description may be mashing up different problems...), then, yes, it tastes bitter to me.

Conversely, when the shot ones fast, the stream thin and watery, then I "get" the sourness.

But when the extraction seems good, yet the taste is still bitter/sour, often I have trouble telling which is which. Being surer of the taste would obviously help me diagnose the problem.

Anybody else ever have this conundrum, or should I get out of the race? :)

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Postby wookie » Nov 05, 2010, 2:30 pm

A lot of people confuse bitter and sour and don't have a clear idea of the distinction. I think that most of us start out being uncertain about this. But of course you can train your palate with practice whether we are talking about espresso, wine or fine foods. As your palate becomes more refined, it is easier to distinguish more subtle sour or bitter notes in coffee. So don't give up yet.

As a start, you could take a grapefruit and taste it. The grapefruit will be sour. Now try a small piece of the rind, which will be bitter. Try this several times and notice the difference. Here are a few other sour & bitter foods.

sour: grapefruit, lemon, lime, sour-flavored candy, fermented dairy products
bitter: citrus peel, unsweetened chocolate, uncured olives, dandelion greens

As you pay more attention to espresso or food in general, the better you will get at discerning the differences. There is a great, if expensive aid to honing your sense of smell called Le Nez du Cafe. This is a set of 36 distinctive aromas that you can compare to the espresso that you are tasting. Smell and taste are closely related. A lot of people will find the price extravagant, but you could do something similar at home by taking the time to taste or smell some common items such as vanilla, caramel, butter, roasted peanuts, freshly roasted coffee beans, cinnamon, garden peas, caraway seeds, etc. It sounds simple but if you pay attention and repeat it a few times it really does improve your ability to discern aromas and tastes. Take a look at a coffee tasting "wheel" if you haven't seen one before.

Another exercise that is sometimes done in culinary schools is blindfolded tasting. Have someone feed you samples of various foods such as apple, onion, cream, etc. Try to identify what you are tasting. It's harder than you might think when you can't see the food and don't know what it is in advance. Even if the foods are not directly related to coffee, the exercise will improve your palate in general.

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Postby another_jim » Nov 05, 2010, 2:45 pm

This is a common question, and the usual answer by cuppers and other taste mavens is that the person asking lacks experience. I've given this answer many times before; but now I believe it is wrong. Instead, I think us mavens are using a taste theory that is about as accurate as phlogiston.

Suppose you taste a 4.5pH solution of citric acid (lemon juice) and tartaric acid (white grape juice). Can you tell them apart? Obviously. The tingly, effervescent feel in both is a the acidity. The actual taste, slightly cutting for the citric, slightly astringent for the tartaric, are bitter flavors.

There is only one acidity receptor and it responds to simple H+ ions, nothing else. This registers as a tingly feeling, nothing more. There is only one salt receptor, responding to negative ions, giving a salt taste, and nothing else. There is on sweet receptor, which is more complicated and not fully understood. Inferrring from responses to artificial sweeteners, researchers think it responds to three separate molecule shapes, and compines these into a single signal.

There is no bitter receptor. There are instead, at least 20 different receptors responding to various proteins, signalling bad things like toxicity and rottenness, and good things like meat and rarer nutrients. Classification these into bitter and umami or whatever is a remnant of Galen's four element or Taoist five element theory, ancient superstitions and nothing more.

When you distinguish citric acid and tartaric acid, you do it because they stimulate these twenty so called bitter receptors in different ways. These different receptor signatures, in conjunction with retronasal aroma receptor signatures combine to create all tastes.

I'm now inclined to to regard acidity as strictly indicated by a lively and effervescent mouthfeel, while the distinct taste of all the fruit acids: citrus, wine, vinegar, berries, peach, etc, are like every other taste -- distinct signatures created by the twenty odd bitter receptors.

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Postby TrlstanC » Nov 05, 2010, 3:56 pm

For me sour and bitter have just become short hand ways of saying over extracted and under extracted. When I'm trying to explain sour and bitter to someone who doesn't drink much espresso (or at least hasn't thought much about the espresso they drink) it's tough for them to determine what's sour and what's bitter, but when I describe it as under extracted then they can taste it.

When I first started trying to make good espresso I couldn't really tell what was over or under extracted, so it was tough to figure out how to fix my shots. Things got easier the first time I pulled apart my grinder to give it a good cleaning (months over due at that point), and I had to get it dialed back in. I got some shots that were 10 second gushers and some that gave a couple drips after a minute before getting back to normalcy, but I took a taste of all the shots (whereas usually I would've just tossed anything that looked that bad). This gave me a much better frame of reference, and it was easier to pick out the same tastes in shots that were just a little off in the future.

The other big thing I learned was what a big impact stale grinds can have on taste. I was always good about sweeping it out as much as I could, but until I got in there and cleaned out the built up gunk hidden in the corners I didn't realize how much funkiness was ending up in the cup. Now I'm religious about thurough cleanings (grinder, machine, baskets, everything) and it's night and day. Getting rid of a little bit of funkiness makes it that much easier to pick out, and enjoy, all the other flavors.

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Postby kton25 » Nov 05, 2010, 4:22 pm

pavman, I'm glad you brought this up; I've been reluctant to since it seems so trivial. I've been tasting what I'm sure is sour in my shots. The extraction time/flow/etc. have been spot on. Common wisdom tells me that my temp is too low. I gradually kicked up the pressurestat, let the machine stabilize, pull a shot, rinse, repeat. Still sour. I have a 1gp Brasilia Firenze (4L boiler) and ended up at 1.2 on the pressurestat. I've been reluctant to go any higher. I guess I'll keep experimenting and following this thread :)

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Postby ethiopie » Nov 05, 2010, 5:43 pm

another_jim wrote:There is no bitter receptor. There are instead, at least 20 different receptors responding to various proteins

When you distinguish citric acid and tartaric acid, you do it because they stimulate these twenty so called bitter receptors in different ways. These different receptor signatures, in conjunction with retronasal aroma receptor signatures combine to create all tastes.

This is fascinating. Could this be the reason why I personally feel bitter is a more complex taste than either salt, sour or sweet? With these three, I can taste (to a certain extent) a difference in intensity, but that's it. Some things seem to be sweeter than others, etc. However, there are some bitters I dislike (raw Belgian chicory) and others I appreciate (espresso, beer). The sensation of bitterness is remarkably sensitive to other tastes as well; add enough salt to raw Belgian chicory (or is it endive?) and it becomes edible.

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Postby wookie » Nov 05, 2010, 7:45 pm

ethiopie wrote:Could this be the reason why I personally feel bitter is a more complex taste

This may be the case. It has been claimed that we have a greater sensitivity to bitter compounds. There are about two dozen receptors that can detect thousands of different bitter substances. Usually lower concentrations of bitters enhance foods and add complexity, while strong concentrations are aversive (probably perceived as toxins or poisons).

Here are a few abstracts, if you want to read more about this
Bitter taste receptors and their cells
The science and complexity of bitter taste
Nestlé Scientists Uncover the Complexity of Taste

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Postby Dogshot » Nov 05, 2010, 9:41 pm

You should also make sure your machine is really clean. As soon as I taste a shot and can tell there's something wrong, but can't tell if it's bitter, sour, or both, I know it's time to get out the Cafiza.

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Postby michaelbenis » Nov 06, 2010, 4:38 am

I'm stating the obvious in starting out by pointing out that it would be a mistake to put the whole bitter/sour balance down to over/under-extraction.

Sours and bitters don't just indicate whether we've got our extraction on the mark, they're a characteristic of the bean/blend and/or of the roast, including how it's cooled.

In other words, what you do with the machine for the extraction ratio will alter the balance of what you taste, but can't change what you are working with.

So some beans can taste sour even when overextracted, for example. And as a result there's only a fade not a cross-over point on this imaginary sour -> bitter scale, making it more difficult to tell them apart.

Which is why (and this, finally, is my point) we also need to look for other indicators to gauge our shot extraction, including the emergence of other flavour nuances and the suspension of fat/creaminess/body as someone mentioned.

It's more of a three-dimensional balancing act than a simple left to right. Which is why I don't think the terms over/undextraction are always that helpful. They can suggest that a godshot somehow lives flat bang in the centre of the line when.... there ain't no line, there's a playing field.


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Postby cafeIKE » Nov 06, 2010, 10:02 am