Why filter espresso?

…I like what a paper filter at the bottom of the espresso basket does to shot, to the extraction, to the whole process.

— James Hoffman, coffee pioneer and former World Barista Champion

 

Filter papers are not part of traditional espresso brewing, so why are coffee experts now using them? We summarise the reasons here.

 

Coffee quality

 

Firstly, the theory is that filter papers can improve the quality of espresso through the following process:

 

  1. Improved flow of water through the coffee puck, resulting in…
  2. More even extraction, resulting in…
  3. Better tasting espresso, with more sweetness

 

How does this theory work in detail?

 

When pulling an espresso shot without a paper filter, the smallest grinds in the dose migrate towards the holes in the filter basket, which can partially obstruct the flow of water.

A paper filter prevents this obstruction, resulting in a higher flow of water for a given grind size. Additionally, the filter presents a more even resistance across the whole surface of the basket floor, minimising variations in the flow across the puck. This results in more even extraction, with fewer of the bitter compounds like tannins that can dissolve when the water is in contact with the coffee for too long. The result is a sweeter, more delicious espresso that truly expresses the complex flavours of the roasted coffee beans.

In addition to these primary benefits, coffee experts report some secondary benefits:

 

  • No bitter-tasting coffee grinds at the bottom of the cup, as the paper filters them out
  • A denser and thicker crema, as the paper "bursts" all the larger bubbles
  • A cleaner basket, with no grinds caught in the holes thanks to the paper filter.

 

Using a filter on top of the puck

 

There are also some advantages to using a filter paper on top of the coffee puck reported by coffee experts:

 

  • Better-tasting espresso due to less channeling. Channeling causes local over-extraction and leads to a bitter taste in the coffee.
  • A cleaner brewing process with less mess. The filter paper on top of the puck throughout the brewing process keeps the shower screen cleaner for longer.

 

Cafestol and kahweol

 

While we are not claiming that our filter papers can improve your health, there have been several scientific studies which concluded that coffee filtered through paper has a smaller impact on blood cholesterol than unfiltered coffee or coffee filtered through metal alone*.

 

Research has shown that the natural oils present in unfiltered and metal-filtered coffee contain substances called cafestol and kahweol, which increase the levels of both total and LDL (“bad”) cholesterol in your blood, as well as impairing liver function. Researchers have also demonstrated that the “fines” (smaller grinds) that make it into the final brew contribute significantly to the levels of cafestol and kahweol in coffee.

 

It has been shown in various studies that, as the coffee flows through the paper filters when used in brewing techniques such as drip filtering, these compounds are reduced or even removed, and so the impact on blood cholesterol is significantly reduced. The effect is not seen with a metal filter.*

 

Although some of the original investigation into espresso filter papers by the coffee community was motivated by the desire to reduce levels of cafestol and kahweol, there is no peer-reviewed academic research on the impact of paper filters in espresso. 

 

Take a look at the “Further reading and references” section below if you’d like to investigate further.

  

So there you have it, now you know why coffee experts claim that paper filters can improve your espresso!

 

Check out some of the links below to find out more, or head to the Esspero store to pick up some filter papers.

 

Further reading and references

 

Here’s James Hoffman talking about using paper filters in his video “How I make espresso”.
Here’s a link to a US patent from 1997 (now expired) on using paper filters for espresso.

 

Coffee quality

 

Coffee, cafestol, kahweol and cholesterol

 

* An individual's levels of blood cholesterol are dependent on many factors. Reducing or eliminating the presence of cafestol and kahweol in the coffee an individual drinks may or may not have a significant impact on his or her blood cholesterol. The results referred to here are from peer-reviewed academic papers, in the experimental design and review of which we were not involved, and their results are for non-espresso coffee brewing techniques. We have no way of knowing for sure if similar reductions of cafestol and kahweol will occur when using a paper filter for espresso, as there is no relevant scientific research on this to date. Always consult a medical professional before making any changes to your healthcare routine, diet or consumption patterns, starting any new treatment, or if you have any concerns or questions regarding your health.

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