Cross contamination! Is your cupping routine up to scratch?

28 Sep

After our previous experiment with unripes we got a comment suggesting that the lack of a clear result might be due to cross contamination of the coffees. Even though we feel we have a good cupping routine, cleaning the spoons between each cup and so forth, we thought it might be interesting to check for ourselves what the effect of a really bad cross contamination would be and if our current cupping procedure is up to scratch.

For those of you who don’t know what a cross contamination is I’ll try to explain: Imagine that on a cupping table you have several cups of coffee and one of these contains a stinker bean or another defect which is really apparent. During the cupping process some bozo isn’t cleaning his spoon between each cup, or that during the breaking of the cups that same clown is just going from cup to cup breaking the crust without rinsing the spoon in between. This can lead to the taste of that defect being brought to the other cups and consequently affecting their taste. There are several other scenarios where you might get cross contamination, but this was just an example.

So to our experiment:

We found the worst defect we could come across, which in this case was a really past-crop Harrar from Ethiopia we’ve been using to roast. We picked the worst looking beans of them all and put them in a cup.

We then picked two coffees we know are nice and clean. A Kenyan coffee from Eeagads Estate and a Rwandan coffee from Bukonya Estate.

We set up three groups of the two coffees. One to be thoroughly cross contaminated with the defect cup, one being treated to our normal cupping routine and one not being cupped with the defect cup at all. The three groups were cupped with different spoons cleaned in seperate cups to make absolutely sure there were no cross contamination between the groups.

The defect beans were ground last to make sure that no cross contamination occured in the grinding process.

Then we started cupping. One by one we tasted Bukonya from the first group, the Bukonya from the second group and from the third. Then we did the same with the Eeagads. We were four people cupping but I wont mention the names save to say it was the usual suspects. (We had another comment saying that mentioning who the people cupping were might influence how the readers would interpret the results.)

The overall conclusion was that even though we over contaminated the first group, the defect wasn’t as apparent as one might expect. The second and third group (the control group) dispalyed no apparent differences thus proving that our normal cupping procedure is thorough enough and doesn’t produce cross contamination.

What we found interesting though was the low degree of defect taste in our overly cross contaminated group. The cup with defected beans tasted really horrid of ferment and unripe beans, but very little of this taste made it over to the cross contaminated cup. We found this strenghtening the concusion of our last experiment that the actual type of defect (say a stinker) has a lot more to say with whether or not it stands out (and cross contaminates) than it just being a nasty tasting bean. We also feel it strengthens the theory that cross contamination between two “fresh” coffees will be hard to taste.

All this being said, we feel strongly that for hygenic reasons it’s important to have a quite strict regime, and it also helps ruling out all eventualities when production cupping.


9 Responses to “Cross contamination! Is your cupping routine up to scratch?”

  1. emily Friday, September 28, 2007 at 11:46 #

    very interesting… will definately try the experiment myself.
    Do you usually cup one origin all together, or mix them up?

  2. Olings Friday, September 28, 2007 at 12:15 #

    We have an open cupping every day at 16.00 (4 pm) so that our customers can join in, but we also cup our production and to decide what coffee to import.

    In the first type of cupping we often cup our whole range of coffees, whilst in the second type we cup less different coffees and often cup only several cups of the same coffee.

    We also try to do at least one experimental cupping each week to educate ourselves further by trying things for ourselves not just taking what we read in books and on the internet for granted.

    I’m glad you found the experiment interesting. We at least got a lot out of it ourselves.

  3. aaron Saturday, September 29, 2007 at 1:27 #

    Excellently done! It’s so refreshing to see your experiments and how committed you all are to continuing to learn and grow. Well done.

  4. Ben Kaminsky Saturday, September 29, 2007 at 1:43 #

    At the barismo cupping sessions, we were previously using a Mazzer super jolly for grinding our comparative roast cuppings as we continue towards our goal of roast perfection. We were consistently noticing that certain cups would taste similar. For instance, when cupping in pairs, 2 and 3, 4 and 5, 6 and 7, etc. all had slightly similar attributes that made conclusions about the roast less precise. We have recently started using the Hario Ceramic hand mill (burr grinder) for our cupping purposes and we all think its fantastic. We notice almost zero contamination during the grind and there it literally a ten fold increase in dry aroma. Its really amazing and quite shocking at first. For about $25 US with shipping, its a bargain. Thought you guys might like to know.

    The one I recommend is the “skeleton”:

  5. Olings Saturday, September 29, 2007 at 21:14 #

    Thanks for the tip, Ben! Will definately check it out.

    We appreciate all of your comments. It’s nice to see that there are more people out there that care about these things as much as we do.

  6. Olings Saturday, September 29, 2007 at 21:33 #

    Hmmm… Ben, I don’t think your link is correct. I couldn’t find the grinder there, but I found it through your website. Could you explain to me why you think it made this difference in your cupping. Have you tried it head to head to the Mazzer? I thought we’d try one of our hand grinders with burrs from Zassenhaus.

    Maybe next weeks experiment will be the comparing of different grinders for use in cupping. Not a showdown like on , mind you. I’d like to do it only to maybe improve further on our cupping.

  7. phil Thursday, October 18, 2007 at 20:48 #

    Thanks for the blog. I love it!

    Is there any way you might be able to link to our site?

    Phil at Maestro Coffee Roasters

  8. Olings Thursday, October 18, 2007 at 21:22 #

    Sure Phil.

    With a link back perhaps many things can be fixed. He he.

    I don’t want things to turn too commercial though…

    E-mail me, and we’ll work things out.

  9. phil Friday, October 26, 2007 at 23:14 #

    Cool… I just linked back to you from our blog. Thanks for the consideration! –Phil

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