Why Does Coffee Dry Your Mouth?

There is a common misconception that coffee causes dryness in the mouth because caffeine dehydrates the body. However, this is not true in moderate amounts as caffeine does not impact the water-salt balance. Moreover, coffee has the same hydrating properties as water when consumed in moderation. 

The dryness that some people experience in their mouth after drinking coffee is actually caused by the astringent properties of the drink rather than dehydration. It’s worth noting that dryness in the mouth can also be caused by other beverages and products, such as wine, various types of tea, or berries.

Astringency of coffee

The astringency of coffee is caused by a group of polyphenols known as tannins. Similar to tea, coffee is the main source of tannins in our diet. As we consume coffee, tannins react with our saliva, leading to a decrease in its lubricating properties and forming deposits on the tongue. It is worth noting that caffeine has a tendency to decrease the production of saliva. This results in a feeling of dryness or astringency. 

In moderate amounts, astringency adds a unique taste to the drink. However, many people prefer to have coffee with less astringency. Luckily, there are several ways to reduce the astringent taste of coffee.

What affects astringency?

If you want to make your coffee less astringent, there are a few things you can do. Adding milk to your coffee can help reduce its astringency. Additionally, how long you extract the coffee can also affect the level of astringency. For example, cold brew coffee is typically more astringent than pour-over coffee. 

Controlling the extraction time is key to limiting the tannin content in your coffee. A simple rule to keep in mind is that the longer the extraction time, the more astringent your coffee will be. This is because many tannins do not dissolve well in water and therefore only affect the taste of coffee when the extraction is high. In fact, the largest tannins only end up in your cup when the coffee is extracted to around 30%. So, over-extracted coffee will have more tannins, making it more astringent than under-extracted coffee. 

Aside from extraction time, there are other factors that can affect the perception and taste of astringency in your coffee: 

• The acidity and saltiness levels in your drink can make it feel more astringent. 
• The less sugar you add to your coffee, the more pronounced the astringency will be.
• The more finely ground the coffee beans are, the more astringent the resulting drink will be.
• The temperature of your drink can also influence its astringency level. Cold coffee tends to be more astringent, so adding sugar can help balance out the taste. 
• The fat and oil content in your coffee can also impact the level of astringency.