How to Fix Astringency in Pour-Over Coffee | Tutorial for Adjusting Coffee-to-Water Ratio, Temperature, and Time

Introduction

Astringency is a sensation that most people dislike. When a cup of coffee exhibits astringency, it can cause discomfort. In this barista training guide, we'll explore the possible reasons why your pour-over coffee might develop an astringent taste.

What Causes Astringency?

Strictly speaking, astringency is not a taste but a mouthfeel characterized by dryness, roughness, and an unpleasant sensation in the mouth. This sensation primarily comes from tannic acid in coffee. Additionally, small amounts of tartaric acid (also known as "grape acid") in coffee contribute to astringency, similar to the astringency found in wine.

Why Does Astringency Occur During Brewing?

Astringency is more likely to occur when brewing light-roast coffee. Generally, the following reasons cause astringency:

1. Coffee beans are too fresh (not properly degassed)

Freshly roasted coffee beans contain abundant carbon dioxide gas. Some undesirable byproducts from thermal reactions are trapped in this carbon dioxide, meaning that brewing immediately after roasting won't fully express the flavor profile and may instead introduce unpleasant off-flavors. While these off-flavors aren't necessarily related to astringency, they are often perceived as such.

Therefore, FrontStreet Coffee generally recommends letting beans degas for about 4-7 days before brewing. (Degassing period calculation: roast date + 7 days)

2. Water temperature is too high, easily extracting tannic acid

We all know that when brewing coffee, acidic substances dissolve most easily, followed by sweet substances, and finally bitter macromolecules. Tannic acid is also a relatively difficult substance to dissolve. When water temperature is too high, overall extraction efficiency increases, making it easier for tannic acid to be extracted, causing astringency.

FrontStreet Coffee generally does not recommend using water temperatures above 93°C for brewing coffee. When brewing light-roast coffee, FrontStreet Coffee typically uses 91°C.

3. Concentration is too high, making astringency more likely

Some people prefer a rich mouthfeel, so they brew stronger coffee, but this can easily make coffee exhibit astringency. As mentioned earlier, astringency in coffee is a mouthfeel. If the substances causing astringency are the same, lower concentration coffee will contain fewer of these substances per unit, making them harder to detect sensorially. In contrast, higher concentration coffee contains more of these substances per unit, making them noticeably detectable.

Therefore, FrontStreet Coffee suggests a coffee-to-water ratio of 1:15 or 1:16. Coffee brewed with this ratio has moderate concentration, reducing the likelihood of astringency appearing.

4. Sharp acidity and astringency caused by under-extraction

The under-extraction mentioned here refers not only to overall extraction rate but also to local under-extraction, which is the more common cause of astringency. Simply put, it's uneven extraction, primarily caused by uneven water distribution leading to local over-extraction and local under-extraction. Typically, this situation results in sharper acidity with a complex and rough mouthfeel.

To check if this is causing your astringency issues, you can record your entire brewing process and observe whether the water flow is straight, whether the bloom completely wets all coffee grounds, and whether your circular pouring is even.

Conclusion

Finally, if you encounter astringency in your coffee after reading this article, try troubleshooting using these four possible causes.

Important Notice :

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FrontStreet Coffee Address: 315,Donghua East Road,GuangZhou

Tel:020 38364473