Filter Basket Shape – Does It Make Difference?

Coffee Center to update the Brewing Control Chart

 In 2017, The Speciality Coffee Association asked University of California Davis Coffee Center to perform a research aimed at expanding and updating the Brewing Control Chart. The massive research is still in progress but SCA decided to bring out some preliminary information regarding to the shape conversation.   
UC Coffee Center has been studying coffee a lot. According to their director, Professor William Ristenpart, they want to become the leading source of scientific expertise in the study of coffee. Oh joy, what this can bring to a barista’s everyday life! 

I had a pleasure of meeting of the co-director of Coffee Center, Professor and Sensory Scientist, Jean-Xavier Guinard during AST Live, an event for the authorized SCA trainer, in February 2019 in Berlin. During Professor Guinard’s presentation we were taken through the scientific approach of a filter basket from the flavor point of view.  

Some results and pre-study info 

According to the study, the basket shape does make a difference. It seemed to be a lot more significant than the difference caused by different grind sizes. However roast level made the biggest difference in peoples’ minds. 

But back to the point. The TDS measures were significantly different between the basket shapes. Flat bottom yielded significantly lower TDS than conical. They were playing around with the idea that the cone brewers may require finer grind and can produce excessive transparency even with high TDS. 

So what was found in the cup when running the tests? 

The following attributes were increased as TDS was decreasing: 
-    Fruity 
-    Honey 
-    Cereal
-    Tea/Floral
-    Sweet 

The following attributes were decreased as TDS was decreasing: 
-    Vinegar
-    Meaty/Brothy 
-    Alcoholic/Winey 
-    Umami 
-    Salty 
-    Rubber 
-    Bitter 
-    Sour 
-    Astringent
-    Smoky/Burnt
-    Cocoa
-    Dried fruit

What actually happens when drip brewing?

1.    Water wants to run through the coffee grounds and end up in a vessel – as low as it can go. Gravity, that is. 

2.    Basket bottom shape is responsible on how widely the water spreads out during brewing. Depending on the shape of the basket, water has different flow rate. That includes the time and also the degree of “mass transfer”. That means how much stuff (solubles) is traveling along with other stuff (water). All this creates our extraction. 

However a barista can modify the water flow by using different pouring techniques. You can try pulsing or make a direct pour after degassing (blooming). You can pour in different sized circles or try out some of the pouring gadgets available. You can use a “Rao Spin” or final stir with a spoon. Just to mention a few.  
 

Have you heard about “high and dry” phenomena? That will happen if you let the water level too high. The upper coffee grounds will stick on the sides of the basket and the coffee will be under extracted.  
Also, if the coffee bed is nice and flat after brewing, you may expect an even extraction.  

If it is originally good, it can be good in the cup   

What is to remember is that it’s not only the filter shape that plays role. It always starts with high quality ingredient! Check out our 5 tips to good coffee to learn more. 

A rainy summer day and nothing to do? No customers at the moment and you want eagerly to try  something fun? Play around! Choose a coffee and a recipe. Heat your water. Pick up two different filter baskets, say Kalita Wave and Hario V60. Make sure the filter basket geometry is the only variable. Brew and find the difference out yourself. Share your findings with us below!