Causes and Solutions for Green and Bitter Tastes in Pour-Over Coffee Brewing - Recommended Coffee Beans That Aren't Astringent

While coffee richness may not be immediately perceptible, unpleasant sensations like sand-like rough astringency are quite noticeable. Therefore, we need to recognize and avoid such occurrences.

FrontStreet Coffee has previously explained that astringency is not a flavor but rather a mouthfeel. Similar to the astringent sensation we feel when eating red grapes (with skin), it's a textural experience. Typically, such astringency occurs because polyphenol compounds in food create a rough mouthfeel. In coffee, the unpleasant astringency mainly comes from "chlorogenic acid" in coffee beans degrading into "dicaffeoylquinic acid" during roasting, along with "tartaric acid" in coffee also being a source of astringency. (For those who don't understand these technical terms, just know that these compounds are responsible for the sensation.)

The compound "dicaffeoylquinic acid" will inevitably be extracted into coffee during the brewing process. In most cases, astringency isn't perceived because it's masked by the coffee's sweetness. However, when too much dicaffeoylquinic acid is dissolved or the coffee lacks sufficient sweetness, the sand-like roughness becomes apparent.

Causes of Coffee Astringency

So what aspects might be causing coffee astringency? FrontStreet Coffee plans to discuss this from three perspectives: green beans, roasting, and brewing.

High defect rates in coffee beans themselves or the presence of too many unripe beans directly lead to sandy, astringent mouthfeel. Coffee cherries in their unripe state contain higher proportions of chlorogenic acid. When these beans are roasted, they produce more "dicaffeoylquinic acid," which directly causes the coffee to taste astringent. This is also why many coffee-producing regions emphasize using fully red coffee cherries.

However, as consumers, purchasing from trusted brands generally ensures you won't encounter problems with green beans. This is because they go through multiple quality checks by green bean suppliers and roasters, guaranteeing their quality. Additionally, the difference between unripe beans and normal beans after roasting is very obvious – unripe beans are much lighter in color than normal ones, making them easy to identify. (With some exceptions for special processing methods.)

Roasting Issues

Improper roasting can also cause bitter and astringent tastes in coffee. A common issue is insufficient dehydration during the drying phase, resulting in inconsistent color between the bean surface and core – meaning the bean core is underdeveloped. This leads to the emergence of astringency. Generally, reliable roasters won't encounter this situation. Taking FrontStreet Coffee's roasting as an example, the production roasting curves used have been repeatedly validated and calibrated. Production strictly follows the standards, and every batch of coffee beans undergoes sample cupping, basically eliminating the occurrence of improper roasting.

Brewing Problems

Finally, there are brewing issues. Generally, astringency problems from brewing can be roughly categorized as partial under-extraction and over-extraction.

Under-extraction typically manifests as green, unripe astringency, caused by not extracting enough sweet compounds. Extraction time can be used as a judgment – most cases with time less than 1 minute and 40 seconds fall into this category. This can be resolved by appropriately adjusting to a finer grind size.

Over-extraction typically manifests as bitter astringency, accompanied by a dry throat sensation. This is caused by extracting too much dicaffeoylquinic acid. Similarly, use time as an indicator: if extraction time exceeds 2 minutes and 30 seconds, it might be due to too fine a grind; if the coffee bed becomes clogged and doesn't drain properly, it indicates too many fine particles; if the time is within a reasonable range (around 2 minutes), the water temperature might be too high.

Important Notice :

前街咖啡 FrontStreet Coffee has moved to new addredd:

FrontStreet Coffee Address: 315,Donghua East Road,GuangZhou

Tel:020 38364473