Quality of coffee
The quality of your coffee depends on the following factors (in no particular order):
1. Time since grinding the beans.
2. Time since roasting.
3. Cleanliness with brewing equipment.
4. Bean quality (what crop, etc.).
5. Water quality.
Fact: A coffee can in the supermarket often contains major debris, so be careful when you choose. (See note below).
Fact: Once you have freshly roasted and ground coffee, filtered water and equipment free of oil residues from the last brew, quality of beans makes a huge difference.
Arabica beans are usually flavor rich, while robusta beans have more caffeine, less flavor and are cheaper to produce. When you buy coffee, whether in a coffee house or in a supermarket, you want to get 100% arabica, except for espresso blends, which may be a combination of both.
My personal experience says that a 100% arabica espresso blend is better.
Ιt should be mentioned that coffee is at its best after 12-24 hours of roasting.
Buy only fresh roasted coffee and grind your coffee at the time you want it.