Why Your Coffee Tastes Sour


Coffee is among the most popular drinks in the world. Brewing coffee from jars is fascinating to people. Millions of people drink it daily, with an estimation of 2.25 billion cups consumed every day. People want to know what causes bitterness and sourness in a cup of coffee.
In this article, we will explore what causes coffee to taste bad. We will also look at what causes coffee to taste sour and bitter and discuss ways to improve its taste so you can enjoy that perfect cup of java.

Taste of Coffee

The taste and flavor of the coffee are because of the aromatic compounds present in roasted coffee beans. More than 400 aromatic substances have been identified so far; however, the two most important for determining overall flavor are furans, which give a sweet taste to coffee, and 5-hydroxymethylfurfural (5-HMF), which provides it with a more sour and bitter taste. The exact amount of 5-HMF in each brew depends on various factors, but it is widely agreed that higher amounts can produce more bitter and acidic coffee.

The taste of coffee depends on the amount of water (regardless of the freshwater or bottled water) used and how it is brewed. For example, coffee can be brewed using a French press or drip. The French press makes it possible to extract more oils from the coffee beans than the drip process because each brewing method exposes different strands of plastic to the coffee beans. There are two ways bottled water may affect your understanding of what a cup of good coffee should taste. Firstly, if you use bottled water that has not been consumed for any length of time, some oxygen will have entered the bottle, affecting the coffee flavor. Your coffee’s taste will also be affected if you use bottled water treated with a polymer like MgSO4 or CaCl2.

Differences Between Sour vs. Bitter Coffee

Bitter Coffee

When it comes to bitter flavor, it’s pretty hard to pick a definite culprit, but one factor contributing the most is caffeine. Another big player is pH, and coffee contains many acids in its oils, responsible for the acidic bite. A sugar molecule called quinic acid can also contribute to the bitterness of coffee. This acid combines with proteins in a person’s mouth and teeth to form insoluble compounds that make the pits feel worse than they are.

Reasons for a Bitter Cup of Coffee
  • Poor brewing.
  • Exposed (to Oxygen) coffee beans.
  • Unfamiliar or bad coffee variety.
  • Acidic water (bottled) or mineral water (tap) where the pH is moderate. If you drink bottled water with its pH adjusted and added minerals (neutralized acidity), it may not affect the taste, unlike tap water. If the tap water has a pH level of less than 7, meaning it has a low amount of alkalinity, minerals in the water can make your coffee cup taste bitter. Using a carbon filter or boiling the water can adjust the pH of your tap water.

Sour Coffee

As mentioned above, as coffee ages, it becomes more acidic. When it reaches a pH level of 5.0 or lower, the coffee turns sour and has a bad smell. When the drink goes stale, its delicious characteristics diminish, and its taste becomes bitter while still retaining a bad aftertaste. The presence of 5-HMF mainly contributes to the acidic taste.

Reasons for a Sour Coffee

The reasons for sour taste are:

  • Poor brewing technique.
  • Well-roasted coffee that gets mold in the storage bin and on the beans.
  • Coffee beans are exposed to Oxygen in storage.
  • Stale coffee that has begun to go bad, either through overgrowth or mold growth. The latter will reek of dampness, as well as a wet dog smell. This smell can be detected when the bag is opened. Or it could have started to rot internally, and you can catch a sour smell at this stage. Sometimes it can be seen by looking at the beans in daylight, with brown or black spots showing up as part of a more prominent splotch.
  • Stale coffee beans that have been ground or brewed before then stored again.

Tips for a Good Cup of Coffee

Of course, all of these factors are not necessarily bad in themselves, but they may alter the way you drink your cold or hot coffee.

To maintain a decent taste of coffee, try one of these tips:

  • Brewing time should be shorter than it initially takes to brew. This time will ensure that a more fresh flavor stays with it until it is enjoyed. Suppose you have stored bottled water in the refrigerator. Use only a quarter to a third of the actual amount after opening it because it stales quickly and changes the water’s pH level.
  • When using bottled water, use the same amount as you would with tap water. This way, the taste of the coffee won’t be different after adding it to the cup.
  • If you are brewing coffee with a French press, use filtered water instead of tap water that has been in storage for some time. You’ll also need to buy new filters regularly.
  • Avoid buying coffee in bulk because this will change your options regarding how much coffee you can drink at once.
  • Every type of coffee has a particular brewing time. Just like espresso must be brewed for 20 to 30 seconds in the espresso machine. Moreover, the French press must be brewed for 2 to 4 minutes and so on. On the other hand, cold brews take a longer time to prepare.


Coffee is a popular beverage. However, we need to be very careful about the brewing process and the recommended brew time. Brewing coffee in the wrong way can make your entire cup taste extraordinarily bitter or sour. So, always remember to follow the proper brewing process if you want to enjoy good coffee.


Q. How to make a sour-tasting coffee?

A. There are a few ways to make sour-tasting coffee.

First, it is possible to roast your beans for too long. The flavor of the beans changes after roasting. That is why you need to be careful not to roast your coffee for too long.
Second, if you keep changing the water or brewing the coffee for an adequately long time, you will extract all the bitterness from the beans and make it taste bad-tasting.

Lastly, if you use old beans for brewing the coffee, it will also taste bad.

Q. What makes coffee taste bitter?

A. It is crucial to know the reason behind bitter-tasting coffee and reduce those effects when serving guests or drinking alone. The bitter flavor comes from the coffee beans themselves-these are the ones that grow on the trees; they are green when they’re freshly picked but turn brown and harden up as time passes. Caffeine is another ingredient that can create sour flavors, especially if the cup is brewed for longer than recommended.

Q. Does brewing coffee in a paper filter make it taste bitter?

A. Brewing bitter coffee can be caused by many factors, such as using paper filters, not rinsing the scoop and using the wrong kind of water. Paper filters are used to keep grounds out of your cup of coffee; they are made from bleached white wood pulp or cellulose, which is edible. That means that they will absorb some of the oils in your coffee during the brewing process, which will create a bitter taste in the cup.