Phantom Potato

We cupped a few coffees today, and in there were a few from Rwanda.  Whenever Rwandan coffees are on the table the conversation inevitably turns at some point to potato.

For those who have no idea what I am talking about I should explain.  There is a defect in coffee that is referred to as potato.  It is the result of a bacterial infection of the seed, usually after being bitten by an insect carrying that bacteria.  Once roasted that particular bean carrys very, very strong aromas of freshly peeled potato skins that is incredibly potent when you grind the coffee and when you brew it.

Unlike many other defects you can’t tell if a green or roasted bean has potato in it until it is too late.  The solution to the problem is very labour intensive.  When the cherries are picked any cherries that show signs of damage are discarded, and this process is usually done by hand.  After the washing process, when the parchment coffees are still very wet it is also apparently possible to see the damage and discard the beans at that point.  However if a bean has been missed and is dried then it is undetectable until ground.

The potato defect is a problem in several countries, but has become more of a talking point as Rwanda has risen to prominence as producing country capable of stellar coffees, but also a producing country that has problems with potato.  I don’t want to rattle on too much about it – I highly recommend reading this thread if you want to know more about the potato defect.

The real point of this thread is to talk about the weird psychological effect that potato had on me, and ask if anyone else suffers this.  Once you smell potato a few times in a coffee you are using you become hyper sensitive and a bit paranoid.  Cautiously sniffing for even the faintest sign of potato.  The Nyamagabe lot we used in Stephen’s WBC espresso suffered from potato, and we went to ludicrous efforts to prevent it a

It snuck up again in Copenhagen – during the Cupping competition I was stood near the prep area, next to Edwin from Finca Vista Hermosa, and we both caught the distinct potato peelings smell in the air.  That cup was pretty easy to pick out!

After the lot of Nyamagabe was finished I thought I would be able to relax, but still the smell haunted me.  Every now and again I’d find myself sitting bolt upright in the roastery, sniffing the air thinking “Is that potato?? IS THAT POTATO??” before remembering that it couldn’t be, and that I was loosing my mind.

Am I the only one?  Does anyone else who has experienced potato a bit get somewhat paranoid about tuberous smells?  Am I making quite a public fool of myself?  You decide…..

  1. We packed all the Nyamagabe component seperately in 500g bags that were sealed.  Before use we’d carefully open each bag and elimate any that showed even the slightest waft of potato before blending with the El Bosque.  Regardless of this – the final practise shot on stage before the finals there was a clear and terrifying *poof* of potato flavour that filled the stage.  We hoped lightening didn’t strike twice!  (back)

31 Comments Phantom Potato

  1. hugo

    I had it today, mingled with the distinct aroma of chocolate brownie as I wandered through the kitchen to the deli…. Tristan was there and may have smelt it too…
    Turns out it probably was potato, Cornish Potato. Going into the tortilla. Delicious.

    On a more sensible note, we have Rwandan Misozi Co-op in our current shop blend and I’ve yet to notice the potato smell from it… but we do get plenty of quakers that I get phantom smells of, since you pointed them out at Origin’s offices. There again, we sell lots of peanut butter cookies that smell amazing when they come out of the oven…

    I guess the problem if working in a cafe & delicatessen is you’re constantly bombarded with smells that shout coffee problem but are nothing of the sort… mix that with too much caffeine to heighten your paranoia and you’re doomed.

  2. Bea

    Okay so if I ever need to prank a coffee geek, remind me to hide bags of potato peelings around their espresso machine….

  3. Sarah Wilson-Jones

    Yes! I have found that, too, and wondered what the heck it was. Some of my fellow Phoenixers will remember a triangulation test that we did last Fall where we had a cup or two with potato in it and it was quite perplexing. Thanks for digging around and reporting about it!

  4. Tim Styles

    I must admit that in our cupping on Wednesday, even just hearing you say the word ‘potato’ made me sniff and re-sniff things thinking… “Was that…?”. But thinking back to the Nyamagabe, and remembering just how clear the potato smell was, I figure that if I ever have to even ask, it isn’t.

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  6. David LaMont

    I absolutely agree with you. To be perfectly honest, I’ve been scared away from Rwandas lately due to phantom spuddiness. Some of the instances have been so potent that it really sticks negatively in my memory. Now, I fear that the positive aromas of a Rwanda are almost inextricably tied to potato defect smells.

    Reading your post felt like finding a support group for a little-known illness–sort of a “I’m ok. I’m not alone.” moment. Ridiculous, but relieving nonetheless.


  7. michael P

    Certainly. We Have a Rwanda right now and currently brew coffee to order on the clover. If it is the main selection that day we end up brewing around 200 plus cups… Once you find that first cup, perpetual fear sets in. I am actually debating using a lovely Rwanda micro-lot right now for competition but the spud-effect makes me nervous…

  8. Anette Moldvaer

    The potato defect is not only found in Rwanda, neighbouring countries like Burundi also suffer from the problem. Our choosing to buy Rwanda (and use it in competition) was/is perhaps a risk, but the coffees coming out of this country can be so, so lovely, and I see no reason to NOT buy them because you’re worried about potato, your customers finding it offensive and it not selling. If you try to hide it from them you’ll have a problem on your hands, if you use it as a chance to talk about coffee and it’s wonderful, frustrating, rewarding nature- you’ve got customers almost HOPING for potato, just so they can experience the bizarreness of it!

    Some of the guys who were using the WBC blend in their shops before we created our first seasonal blend would indeed get the odd waft of potato in the grinder, but when you’re aware of it, and care enough to fix it, you dump those grinds and go again. And some did find it a really interesting piece of conversation to have with their customers! Yes, the potato can be so frequent in some lots that it seems unmanageable and a waste of time and money, and every other cup would have to be dumped. But it can also be ONE bean in 10 kg’s worth of beans, and if you don’t already notice it through the valve when squeezing the bag, it’ll be obvious when you grind. And then you deal with it. A tiny bit of waste to gain a luscious cup of coffee, now we can all cope with that considering how much perfectly good coffee gets spilled and wasted even in the most careful coffeeshops.

    Finding a specialty market to sell their best coffee to has played a huge part in Rwanda putting itself back together after the genocide, and the dedication to raising the game on their production has been evident in the last few years. They are the first country to hold a Cup of Excellence competition, and will continue to strengthen their resources financially and technologically in order to combat the potato defect at their stage. NOT buying Rwanda won’t make potato go away, it’ll only cheat you out of some of the most delicious coffees you’ll ever taste. I can’t wait for our new Rwanda to get to the roastery next week!

  9. jason

    the problem I have with potato in coffee is the problem I have with corked wine. the problem isn’t so much how easy it is to identify, but rather the effect on the cup when it isn’t pointed out. Is the defect really just “on” and “off”, or are there beans which are just mildly affected – enough to flatten off a cup?

    In wine, and with trichloranisole, this is certainly the case.

  10. Gary

    Interesting stuff. I’ve heard about the potato problem but have yet to experience it. As an aside I have just sat down at my computer with a lovely press pot from the Copabakagi co-op. No spuds to report yet just a lovely fruitiness with a hint of chocolate. Got a whiff of tobacco too when I ground it, but not shown up in the cup.

  11. Stephen

    I remember the paranoia quite clearly, and the extra labour James and Anette went through to try avoid it while I practiced.

    When Anette first told me about it I immeadietly doubted my palate’s ability to pick it up and was worried I’d serve it to the judges on the day oblivious of the odour. She quite rightly assured me I’d get it just fine, as I did, and as we all did on my practice run the morning of the finals.

    The odd thing is that I think we quietly hoped it would happen in my performance, allowing the chance to highlight the problem and our willingness to work with the coffee regardless.

  12. Anette Moldvaer

    Jason, I find the potato to be pretty much just ‘on’ or ‘off’, and when it’s there it’s no mistaking. Some cups can have milder potato than others, but still it’s potato, not just flatness. That type of unevenness btw several cups would be more down to a general poorer sorting of the coffee.

    Gaz, I’ll send you a bag if I find one with potato in it!

  13. Gary

    Thanks Anette. And thank you both again for the coffee. It arrived today, loved the personalised labels.

  14. Mike

    I totally know what you mean. I become totally paranoid when we have a Rwanda in the shop. Once I smell it, it’s all I can smell in the coffee. Even drinking a filter towards the end just tasted like potato. It made me wonder with Jason whether it was as ‘on’ or ‘off’ as we think. I could grind off a filter without that strong smell but then taste it in the drink a little. Is this just paranoia? maybe.

  15. Bombcup

    Funny. I agree with Anette that the odd wasted cup should not deter people from Rwandan coffee. When Rwandan coffee gets mentioned I start a count in my head. Rarely does it get much past 10 before potato gets mentioned. Seems sad that it gets blighted for its very occasional blotting of its copybook. Much like Michael Phelps the incredible stoner olympian.

  16. adibben

    this might sound a little strange, but it really helps. if you smell the inside of your wrist (like a lady trying on perfume) your natural odor can help reset your nose. this has helped me in the past identifying cork taint in wine.

  17. triptogenetica

    Thanks Jim! A fascinating post!

    I have some Rwandan greens waiting for me when I get home – Hasbean’s Mugombwa – so I’ll have to roast the next batch with extra vigilance.

    So far I haven’t heard of ‘potato’, or experienced it, so maybe I’ve been lucky with the Mugombwa I have.

  18. aaron ultimo

    Is it just me or is this even more prevalent this year than last? I guess at least it’s encouraging to know it’s not just happening to you. In fact, potato popped up at least once at the MARBC/NERBC this weekend on one of the pour over brewing stations. I agree with Annette that it’s a small price to pay to dump a cup here or there (unfortunately more often here AND there) if it means a beautiful cup of Rwanda in the end. It’s the beauty that keeps me coming back. However, I am becoming increasingly discouraged with our Humure and have even toyed with the idea of no longer carrying this coffee until the problem can be solved. This sort of thing on a grand scale would be a travesty for the producers of this coffee and for that reason I think the voices of support here are spot on. I am absolutely just as paranoid James and am filled with foreboding every time I’m about to open a bag.

  19. Thompson Owen

    If memory serves, I don’t believe insects “carry” the bacteria that leads to potato defect. It is a fungal infection that is endemic to the Lake Kivu area, and damaged coffee is susceptible. Coffee damaged by other means that CBB can be the cause of potato taste. I seem to remember that the acutal taste comes from the plants reaction to the fungus, but I am not 100% sure. I can say for sure that the taste is not specific to CBB insect damage.

  20. drew

    I’ve heard the same as Tom, that the plant reacts to the fungus to cause the flavor. Man, I painfully recall making espresso on a very busy bar with a good Rwandan coffee (MIG Buremera). Working with it trained me to hover directly over the grinder so as to discard the grounds of a fetid bean before clearing the whole room (or, at least, my fellow baristas). The potato funk seemed to turn up with more regularity as the days went on, and eventually I felt like I was playing Russian Roulette with a losing streak. Can anyone comment on “potato” spreading through bags of green coffee?

  21. David Pier

    Is there perhaps something besides the potato flavor that always comes along with the potato flavor? That is, it is reminiscent of potato but really much worse than added potato juice. I had a bag with this problem once, and while I wouldn’t choose to add potato flavoring to my coffee, it doesn’t seem that it would be so objectionable, and yet it was/is.

  22. Atniz

    I never tried Rwanda coffee before. I should try it too but the place where I’m living, I couldn’t get it in any stores. Maybe, should search in online.

  23. Classifieds

    That would be horrible to find after such hard work, that you have coffee beans that have potatoes in them and from the looks of it, it looks very hard to fix the problem

  24. Trevor

    Damn it!
    If not for this post I would have been blissfully ignorant, just thinking
    *what the hell’s that?* now my imagination’s running wild!
    After reading this, I was curious as I am using a few KG of some Copabakagi coop at the moment, but was dubious as to whether I would actually be able to notice any
    potato or not. Then today I got a really distinct waft of potato at one point when grinding, which I think must have been it. I poured the shots, while asking the staff if they could smell it too – and when they agreed (collective power of suggestion?!) – I then remade them, to be safe. Whilst I didn’t notice it again as strong, I kept thinking I could smell it on and off all afternoon – but that was probably just my imagination! I wish I’d kept the shots, so I could have tried them to see what the taste was like, but I
    ditched them as it was busy. Interesting…

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  26. caglar keskin

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