A guide to coffee processing and how It affects flavour

There are several factors which affect the taste of your coffee before you brew: origin of the bean, terroir (the microclimate and soil), varietal, and roast. But one of the most significant is processing, the fermentation and drying of the coffee after the cherry is picked. This article walks you through the main processing methods and how each one shapes the flavour in your cup.

How green coffee processing affects flavour in your cup

There are several factors which affect the taste of your coffee before you brew. Origin of the bean, ‘terroir’ (the microclimate and soil), varietal (significant), roast and the topic of this newsletter the processing (fermentation and drying of the coffee).

The coffee bush produces a cherry with two seeds inside. Peaberry being the exception. Processing can involve removing the skin and flesh or leaving part of the flesh or mucilage on and then fermenting and drying.

There are broadly two processes which lead to different flavour profiles, washed and dry.

Washed process

Washed coffees have the cherry pulp removed and then fermentation for 24-36 hours. This produces brighter flavours has more acidity. The fermentation is ended by washing the green coffee in fresh water & the bean is then dried in an air dryer or on concrete pads. This process tends to produce a cleaner coffee.

Three vastly different examples include.

• New Guinea    

• Colombia Gesha        

• Guatemala

Giling Basah (wet hulled) process

Indonesia growers use a hybrid washed process called giling basah which produces sweeter and sometimes earthy flavours while maintaining intense acidity.

Sumatra Blue Bianca - This is wet and dry process. Grapefruit acidity, grapefruit, guava, and sweet biscuit. (like a milk arrowroot)

Natural or dry process

Dry or Natural processed coffees can be left on the bush to concentrate flavours, the cherry is harvested hole or partially pulped and left to ferment and dry in the open on concrete pads. They tend to have lower or a softer acidity and tend to have nutty, caramel and chocolate flavours. Some argue the process produces sweeter coffees.

Within the natural process there are various grades of what is called honey process. Different amounts of pulp are left around the seeds (beans) and dried on concrete slabs or raised beds for 7 days to sometimes four weeks. The honey refers to the treacle produced by this fermentation process and does sweeten and add complexity to the coffee.

• Sumatra - NATURAL PROCESS         

• Brasil - NATURAL PROCESS                 

• Bolivia Gesha - HONEY PROCESS

Anaerobic process

Anaerobic coffees are fermented a as whole cherry or pulped and fermented in an anaerobic environment using water or carbonic maceration. Carbonic maceration stems from the wine industry and is used in Beaujolais. I would argue it is significantly more successful in coffee than wine. This process produces florals, intense fruit flavours and all types of acidity. This is the process that produces the widest variation as each grower or processor will do something different.

Two vastly different flavoured coffees with the same process.

• Bolivia Java Anaerobic           

• Ethiopia Gr1 Anaerobic
  

Comparison of coffee processes

If you wish to taste how process affects flavour, there are two wonderful comparisons. Coffees from Indonesia and Ethiopia.

• Sumatra Natural and Sumatra Blue Bianca Giling Basah coffees

• Ethiopia G2 Yirgacheffe washed and Ethiopia G1 Yirgacheffe anaerobic.

All these coffees are roasted light to medium, and the coffee is dropped out of the roaster at various stages within the first crack. Our Baraka is a blend of some of the single origin coffees listed above. It is a medium roast. In contrast, our espresso blends are roasted medium to medium dark.

New coffees at Seventhwave

Colombia Gesha is a washed process.

Indonesia Sumatra is a natural process.

Have Fun!

James Lusty