Understanding Astringency in Coffee: A Practical Guide
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Specialty Batch
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15.05.24

Understanding Astringency in Coffee: A Practical Guide

Astringency in coffee is often confusing. Many may not recognise it as a trait in their coffee or are not able to easily describe it. It’s a perplexing and relatively undesirable quality, leading to a less enjoyable coffee experience. So how can we identify, manage and eliminate it? This blog post delves a bit into the science of astringency, its causes, and practical tips to help you achieve a smoother, more enjoyable cup of coffee.

If you frequent coffee bars across the city and stumble upon an espresso grinder filled with light roasted coffee, it may be wise to brace yourself for a kick of astringency, especially once you’ve learned how to identify it. Light roasted coffee, while offering a delicate and complex flavour profile, is highly sensitive and prone to astringency if not handled with care. Inexperienced roasting or brewing protocols and poorly maintained or inadequate equipment can exacerbate this issue. These factors combined make light roasted coffee particularly tricky to perfect.

While this visual cue may just offer coffee drinkers a quick reference or trigger warning, it only scratches the surface in explaining the concept of astringency and its various causes.


What is Astringency in Coffee?

Astringency is a dry, puckering sensation in the mouth, similar to the feeling after eating an unripe fruit. It differs from bitterness, which is a sharp, harsh taste primarily caused by compounds such as caffeine and certain types of polyphenols. It is much easier to identify bitterness because it directly affects the taste buds on the tongue, creating an immediate and distinct harsh taste. In contrast, astringency affects the mouth’s texture, causing a dry, rough feeling that is less about taste and more about mouthfeel. Astringency in coffee is mainly caused by polyphenols, including chlorogenic acids (CGAs) and tannins.


Common Causes of Astringency

Common Causes of Astringency

  1. Underripe Coffee Cherries: This often results from poor harvesting practices. Farmers may pick cherries before they are fully ripe to speed up the harvesting process. Beans from underripe cherries have higher levels of CGAs, which contribute to astringency.
  2. Farm-Level Processing Techniques: Certain processing methods at the farm level can increase the potential for astringency. For example, experimental processing methods that involve fermentation can lead to the formation of ethanol and acetone-related acetic compounds, which act as dehydrating agents and cause astringency. Additionally, inadequate drying techniques can also contribute to higher astringency levels.
  3. Underdeveloped Roasts: Coffee that isn’t roasted properly retains more CGAs, leading to an astringent taste. Roasters may aim for a specific roast colour rather than focusing on adequate development. Underdeveloped roasts often result from inadequate roasting times or temperatures, leaving the coffee with high astringency potential.
  4. Quakers: Quakers are underdeveloped or immature beans that fail to roast properly and retain a higher level of astringent compounds. These beans are often pale and can be visually identified post-roast. If not removed, quakers can impart a significant level of astringency to the final cup.
  5. Channelling During Brewing: Inconsistent water flow through the coffee grounds can cause uneven extraction, pulling out more astringent compounds. This is common in percolation methods like pour-overs. In espresso brewing, channelling can occur if the coffee bed is not evenly tamped or if the grind size is inadequate, leading to uneven extraction.


How to Identify Astringency in Coffee

  • Taste Test: Astringency feels dry and rough on your tongue and inner cheeks. Take small sips and let the coffee sit in your mouth for a few seconds to fully experience the texture.
  • Comparative Tasting: Brew multiple cups using different methods or grind sizes. The cup with higher astringency will feel much drier. For espresso, compare shots pulled with different grind sizes and distribution and tamp techniques to identify astringency caused by channelling.
  • Brewing Method: Astringency can be more common in percolation brews like pour-overs due to potential channelling. Immersion brews like French press usually have less astringency. In espresso, pay attention to the crema and the overall texture of the shot. An extremely thin, pale crema and a dry mouthfeel can indicate astringency.


Tips to Reduce Astringency

  1. Use Properly Roasted Coffee: Ensure your coffee is well-roasted to minimise CGAs and reduce astringency potential. Source coffee from roasters who prioritise developing the coffee better, rather than just achieving a specific roast colour.
  2. Adjust Grind Size: Experiment with grind size. Too fine a grind can cause channelling and partial over-extraction, while too coarse can lead to under-extraction. Aim for a balanced grind. For espresso, finding the right grind size is crucial to avoid channelling.
  3. Improve Brewing Technique: Use consistent pouring techniques to avoid channelling. A steady, even pour when using a V60, for example, can help minimise astringency. For espresso, consider using a distribution and/or WDT tool and ensure even, level tamping to avoid channelling.
  4. Lower Brew Temperature: Reducing the brewing temperature can help minimise the extraction of astringent compounds. For espresso, try lowering the brew temperature slightly to see if it reduces astringency.
  5. Use Quality Water: Filtered water with a neutral pH helps minimise the extraction of astringent compounds. Highly acidic or alkaline water can increase astringency. Ensure your espresso machine is properly maintained and the water filters are regularly changed.


Final Words..

With a more informed understanding of the negative aspects that astringency adds to your cup, you can adjust your coffee brewing to create a smoother, flavourful more enjoyable cup.


Keywords: Astringency in coffee, coffee brewing tips, reduce astringency, coffee taste issues, chlorogenic acids in coffee, coffee brewing methods.
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