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It’s that time of year again where we start to look forward to new crop Rwandan coffees hitting the UK following the harvest there earlier this year. Rwandan coffees are amongst the most versatile in the world with fantastic sweetness, body and flavours of plums/cherries/orange which make them perfect for espresso or for filter. However, they also come with an element of risk attached and we thought now would be a good time to shine a spotlight on one of coffee’s most famous defects….the potato!!

What is the potato defect?

Coffee is an agricultural product and as such, is very easily defected through the interference of pests or problems during the wet/dry process. The potato is one such defect which has such a dramatic effect on the taste and aroma of coffee that it has made quite a name for itself in the industry. Interestingly, this defect is most commonly isolated to the producing countries of Rwanda and Burundi due to a certain type of micro flora that exists here. This micro flora makes its way into a coffee cherry once it has been perforated by an insect known as the ‘antestia fly’ and manifests itself in the cup as a strong starchy smell of raw potato!

The issue with the potato defect is that it is completely random and cannot, be picked out or detected once it has been roasted. If you have purchased a speciality grade Rwandan coffee, it is most likely that the only point you will become aware of a potato cup is when you grind the coffee and the room is filled with the aroma of raw potato. Occasionally you can come across insect damaged green beans like you can do with any coffee origin. There are some who suggest it is the insect damaged beans in Rwandan coffee which cause the defect, however most people accept it is completely random and can strike at any point! During my first experience of the Rwanda Cup of Excellence competition, the winning lot from the Vunga washing station threw up a potato cup during the cupping!

What can we do about it?

Understandably this causes us some problems in the speciality coffee industry as many businesses are put off this fantastic origin due to the threat of the unseen potato! However, at North Star, we feel it is a great example of how coffee is an agricultural product and no matter whether it is speciality or commercial grade, there are some occasions where this has to be taken into account. It is certainly not worth missing out on this fantastic coffee origin for fear of the dreaded potato.

It is, however, of vital importance that businesses understand how to react if a spud does crop up amongst their batch of freshly roasted Rwanda coffee. A fellow Q grader and friend of mine recently visited a shop and detected a fairly strong potato defect in the coffee he had been served. Taking it back, the staff working that day were confused and believed he was accusing them of adding potato to his coffee! This just demonstrates the need to educate baristas about this potential trap so that they are well armed should the situation ever arise. If it does happen to you and you become aware of the smell of potato having ground a shot, the best thing to do is to simply throw it away and grind another. The defect is isolated to a single bean and will usually affect one shot randomly making the chances of coming it across it in freshly ground coffee slim.

The future of the spud

Last year, the Alliance for Coffee Excellence (ACE) announced it was investing in research to try and learn how to prevent this defect from occurring and is currently working alongside exporters/importers and roasters to try and collect data. The problem is being tackled through the use of organic pesticide on the antestia fly at selected washing stations and we have been asked to pass back any information about potato affected lots so the problem can be isolated to an area/washing station. The results from last year alone have been really encouraging and we are looking forward to our lots this year to see how they have been affected further. You can read more about the potato defect and the work that is currently being done to try and get rid of it on the links below:

http://www.coffeed.com/viewtopic.php?f=19&t=1402

http://www.jimseven.com/2009/02/05/phantom-potato/

http://dailycoffeenews.com/2014/06/24/rwandan-research-team-to-launch-20000-potato-taste-defect-study/

http://www.scaa.org/chronicle/2014/07/07/risk-responsibility-and-potatoes-a-rwandan-coffee-story/

As always, get in touch if you have any further questions!