by Therese Brøndsted, M.Sc.
Being able to describe what is in the taste is a great help in making great coffee.
Most people don’t feel good at using their taste sense. But it is not that hard to get better at tasting.
Improve your skills – make comparisons
First stemp to improve your tasting skills is to make comparisons. Start with having two different coffees at the same time – and then taste back and forth. This makes the differences stand out. And here everybody can taste the difference.
Then ask yourself questions:
Which one is the most bitter ?
Which one is the most acidic ?
Which one has the most roasted or burnt flavours ?
Which one has the most chocolate flavor ?
By changeling yourself like this you tell your brain that it’s important to notice – and along the way you will develop more neurons on this -> makes you better at noticing what is going on in the taste.
Acidity and bitterness
It is very common that people confuses acidity and bitterness in coffee. I have often tried to served a coffee with no bitterness and a clear acidity to people – and they say its bitter. Then I ask them to notice where it hits you in the mouth:
How to distinguish acidity and bitterness in coffee
Acidity/sour comes right away when you take a sip of the coffee. And typical you taste it more in the front of the mouth.
Bitterness you feel in the back of your mouth – when you take a sip it can come relatively quick or it can be delayed so it doesn’t appear until 15 seconds later.
To really get hold of this the best way is to make water solutions of pure acidity and bitterness. See below. Training this will help you distinguish low levels of acidity and bitterness in coffee.
The basic tastes in the mouth
The four basic tastes are bitter, sour, sweet and salt. Later was umami as number five. In the mouth you also register pungent taste like chili and astringent (dry feeling) and cooling like mint.
Earlier on researchers made a map of the tongue where we taste the different basic tastes. But it turned out that this was NOT the same for everyone.
So you have to investigate for your self. Take something purely acidic and notice where in the mouth you taste it: Is it on sides of the tongue ? Is it on the tip of the tongue ?
Pure acidic is like lemon juice. But it is very strong so disolve it in water. Pure bitter is difficult to get in foods. A grape fruit is bitter, but also acidic and sweet. Tonic water is bitter, but also contains sugar.
To really get hold of this the best way is to make watery solutions of pure acidity and bitterness. And in low concentrations. So you can notice details in how they taste and where you detect them in the mouth.
Acidity: 2 grams citric acid to 1 liter of water.
Find citric acid where you get other ingredients for making jam. If your tap water is hard (high carbonate/chalk) use 3 gram citric acid.
Bitterness: 100 mg quinine to 1 liter of water
Quinine is the same that makes Tonic water bitter. You can buy it in pills at the pharmacy (against nightly leg cramps).
Sweetness: 22 grams of sugar to 1 liter of water
Salt: 3 grams salt to 1 liter of water
People have different thresholds for when to detect each taste. Some detect high threshold for sour, others a low.
You can explore this by making a range of low contrations of each taste and test together with others where you threshold is. Start a the lowest concentration and move up untill you for sure can taste wich basic taste is in it.
This is not a taste but how thick the coffee feels in the mouth: the viscosity, the texture. It’s like the difference in skimmed/low fat milk and whole milk.
Move the sip of coffee around in your mouth and feel the thickness of it.
Aromas are much more complex than the basic tastes in the mouth (sweet, sour, salt, bitter, umami). We got about 500 different receptors in the nose. An ordinary person can distinguish something like 1.-2.000 aromas. A skilled person can distinguish up to 10.000 aromas.
Aromas in coffee can be things like berry or chocolate. When the coffee has bitterness we tend to think of dark chocolate, when there is no bitterness in the coffee we think of milk chocolate.
The Speciality Coffee Association (SCA) has made a flavour wheel with the aromas found in coffee. Here is an interactive version where you can click to get further explanation of each aroma: https://notbadcoffee.com/flavor-wheel-en/
Flavor is how our brains synthesize aromas, taste and texture into an overall experience.
This is an overall impression of how well the flavours balance in the mouth. So if the coffee has a sharp acidity its not balanced. If the coffee has a strong bitterness its not balanced. And so on.
A well-balanced coffee is pleasant in the mouth.
Coffees can also leave you with a dry feeling in the mouth. That is called astringency. You also get that from black tea, red wine, unripe bananas and cucumber.
It is cause by compounds that destroy the saliva that lubricate your mouth and tongue. This takes a while. So when you get something astringent in your mouth it takes 15 seconds to appear.
Astringent is a feeling and not an actual taste.
The chemistry of taste
When we taste sour/acidity is the protons (H+ ions) we detect.
When we taste sweetness it is sucrose (table sugar) and other types of sugars but also artificial sugars.
Over 650 bitter-tasting compounds have been identified.
Humans has 25 different bitter-receptors in the mouth. Some bitter compounds can be detected by only one kind of receptor. Others binds to 9 receptors (like caffeine). Not all humans got all receptors. That is why some kind of bitterness can be taste by some people but not are tasteless to others.
Some compounds taste bitter right away, others take a while, up to 15 seconds.
Bitter tasting compounds can be amino acids, peptides, esters, lactones, phenols and polyphenols, methylxanthines, flavonoids, terpenes, sulfimides, and organic and inorganic salts.
Mainly the Sodium ion (Na+). Table salt is sodium chloride (NaCl).
Other ions can taste salty but are less salty than Sodium. Potasium (K+) taste 60% as salty as Sodium. But in higher concentrations potasium chloride taste metallic bitter.
Proteins are made of long chains of amino acids. Some of these gives umami taste. Most famous is glutamate that you can buy as monosodium glutamate, MSG (notice that the Sodium will give a salty taste).
Other amino acids: guanosine monophosphate (GMP) and inosine monophosphate (IMP) also give the umami taste.
Aroma chemistry is wast and complex. Most food odours consist of hundreds of different aroma compounds but where only a few are very important.
More than 230 different volatile compounds has been identified from butter. A few of them are very dominant, like diacetyl, butanoic acid and lactones. Then a number are very supporting. And then a lot of minor importance. But still they make up the difference in articificial and true butter aroma.
Another complication in aroma chemistry is that the character of the odour depends of the concentration. Some of the nice aroma compounds from coffee smells nice in low concentration but like feces/manure in higher concentrations.
Several aroma compounds present in coffee are unpleasant on their own … but in the mix they contributed with something nice. Like methanethiol that smells of rotten cabage.
On the list below – notice how aroma compounds not are unique to one thing (like butter or roses), but are present in very different foods/beverages/flowers. Like (E)-β-damascenone that is found in coffee, honey, roses, fruit and whiskey (and more).
Examples of aroma compounds in coffee
Only found in roasted coffee
2-furfurylthiol or Furan-2-ylmethanethiol or furfuryl mercaptan
Burnt and bitter
Guaiacol (smoke, spicy) – present in wood smoke; pyrolysis of lignin. Known in whisky and coffee.
Furaneol (strawberry, pineapple, tomato – but also caramel)
Fructone (fruity, apple-like)
Hexyl acetate (apple, floral, fruity)
Nerolin/ 2-methoxynaphthalene (orange)
Limonene (Orange and lemon peel)
Acetaldehyde (ripe fruit but also bread)
3-methylbutanal / isovaleraldehyde (nutty, fruity, cocoa-like)
Benzaldehyde (almonds but also present in cherry)
Diacetyl (also in popcorn, wine, chicken, beer, mango, strawberries)
Acetoin (apples, asparagus, blackcurrants, wheat, mable syrup – also used as an additive to cigarettes)
Caramel, chocolate and honey
4-hydroxy-2,5-dimethyl-3(2H)-furanone (caramel and chocolate)
(E)-β-damascenone (honey, rose, fruit, whiskey)
cis-3-Hexenal (more unstable than cis-3-Hexen-1-ol)
1-Hexanol (herbal, woody. Is believed to be a component of the odour of freshly mown grass)
Indole (jasmin, but in high concentration: feces)
Benzyl acetate (jasmin but also fruity, like apple and pear)
Geraniol (rose and lemon)
Eugenol (Cloves, nutmeg) Eugenol is also present in cinnamon, but the dominant aroma compound here is cinnamaldehyde.
See more aroma molekyles at https://en.wikipedia.org/wiki/Aroma_compound