Fine coffee learns why coffee turns sour.

Most coffees actually have acid in them. For example, in common coffees, we say Colombia has a "bright acid" flavor, some African coffees have a fruity sour flavor, and so on

In fact, most coffees have acid ingredients. For example, in common coffees, we say that Colombia will have a "bright acid" taste, and some African coffees will have a fruity sour taste. If you don't know the sour taste of coffee, think that coffee will not have this taste, then once you taste the sour taste, you will feel very surprised, subjectively magnifying the degree of this acid.

The description of taste will vary from person to person, but the sour taste of good coffee will not be offensive. You said in the problem description that it tastes "sour", which seems to have reached an unacceptable level, so I will take it as a bad sour. There may be several reasons:

1. The degree of baking of beans is too shallow. It may be that the baker's preference for acidity exceeds your tolerance range, or the baking itself fails.

2, coffee beans placed for too long, put a long time before selling or you buy back after a long time, expired beans will have sour performance;

3, grinding too coarse, too coarse grinding degree in the process of follicular coffee production caused by insufficient extraction, taste sour;

4, the water temperature is too low (but you say it is American, American coffee machines generally do not appear too low water temperature phenomenon);

5. After making the coffee, let it cool, and the cold coffee will highlight the sour taste in the coffee;

6, add sugar after cooling, more prominent sour.

1. Coffee beans roasting process is from sweet and sour bitter several stages, if the selection of some of the depth of roasting sweet and bitter will be more obvious, acidity reduced

2. Water temperature, the higher the water temperature, the lower the acidity!

3. Drink it as soon as possible. If the coffee is left for too long, the acidity will be brighter.