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.