Many people who visit a coffee shop or make themselves a coffee at home often have a coffee that is bitter or does not highlight many of the possible flavours that they could have experienced had the person making it understood the importance of their grinder in making the "foundation" of the coffee.
A coffee is not designed to be bitter, a roaster generally does not think "Awesome, today I'm going to make the most bitter coffee I possibly can." They set out to highlight the many flavours that can be achieved from the wonderful origins that are now readily available to them.
So this rules out the roasters from making a bitter coffee right? Hmm now that must mean "the machine is dirty", this is another possibility but, less likely to make an espresso shot taste heavily bitter, (it is important to keep it clean) it can taint a coffee if the machine is not flushed and cleaned properly but, generally not make the entire shot taste bitter.
Get to the point! All right, so when we look at ground coffee in a filter handle (a filter handle is the part that goes into the espresso machine) there are usually fine particles of coffee in there. If you can imagine these coffee particles as large marbles the water would whizz past the coffee not spending very much time in contact with the coffee and would be unable to pick up the flavours that the coffee has locked in the coffee ground, you may get a little taste of it but the result would be a sweet/ no body or depth of flavour.
Then take this to the other extreme and imagine the finest gain of sand, (like sifted flour) this would mean that the water would be in contact with the coffee for a lot longer as it tries to force its way past all of the coffee grounds in its path to the exit.
If the water spends too long in contact the coffee will become bitter to taste and if it is too short then the taste is sweet with no body. So what we are after is a blend of both to give the coffee enough contact time with the water and not too much to make it bitter.
This is a tricky task and it takes practice to learn where the coffee should sit in your mouth (but it is worth the effort, as it is the foundation of any coffee and you will really impress your friends once you know how to dial in a coffee machine), as you want the right mix of Sweet, Sour, Salty and sometimes a little bitterness maybe desired (for this you will need to learn where your taste buds lie in your mouth).
When your shot is just right the taste should be on the front half of you tongue and the shots should run from a beautiful chocolate to a really nice caramel colour and the water should shut off before that caramel turns to a milky white colour.
So now its up to you, get into the latest coffee you bought and experiment with your grinder taste each shot and what happens when you make the coffee finer or coarser? What feeling do you get on your tongue? Does it make the sides zing? the front tingle or does it sit right in the back of your mouth?
Keep practicing this and I will be back with an brief description on where the tongue tastes (I know it sounds stupid but you will be surprised at just where the tongue tastes, what each area does, who has more taste buds (women, men or children) and once you find out about these areas the wonders of eating and drinking does become enhanced.
On a side note, if you cannot make your coffee change no matter how many times you change the grind, then you may need to look at your grinders blades. A commercial grinders blades will only grind between 600-1000kg as the blades like everything do wear down and need to be replaced to ensure that the coffee can be cut not ground into a paste like peanut butter.
I hope this helps you with your coffee enjoyment. If you need more help pop into one of our stores and our staff will be more than happy to assist you in understanding how to adjust a grinder to get the best from your machine.
All the best, Nathan