The Borlaug Institute Takes on the Potato Defect

Original post found at | Tim Schilling is assistant director for enterprise development in the Borlaug Institute and interim director of the Global Coffee Quality Research Initiative.

My supply of stolen and free coffee samples from the SCAE Coffee show in London ran out on Wednesday, so I went shopping for fine coffees in our local French supermarket chain yesterday.  After being amazed by the filled-to-the-brim shelves with various coffee pods, I found a pack of ground Rwandan coffee from a big European coffee company and bought it.  I cut open the bag this morning and BAM! there it was, like a dark, pungent cloud of napalm, THE POTATO TASTE, gagging me and reminding me of the urgent need to rid Rwanda and Burundi of this abomination afflicting mankind.

What causes it? Research conducted by CIRAD and OCIBU over a six year period in Burundi has shown this off-flavor to be caused by a yet unidentified bacterial agent that enters the cherry skin and produces a pyrazine chemical toxin that binds to the forming “green” beans.  They first thought it was caused by a bacterial transmission via an insect vector, the Antestia bug (see photo)


that pierces the coffee cherry wall and sucks sugars; but later they concluded that anything that pierces the cherry wall can allow the bacteria to enter and eventually release the the nasty ‘pyrazine-based’ toxin.  Because you can’t detect it until you roast it, this defect is a real bummer for roasting companies and a real challenge for research. The photo below shows the hole in the green coffee bean caused by the antestia bug.

So what are we doing? Last year, I had the pleasure of meeting an incredibly enterprising Agricultural Engineering student, Ms. Shraddha Waikar, who is partially supported and supervised by Borlaug’s Research Director, Dr. Bill Payne.  We talked about the incredible impact that could be had if we could figure out how to detect the potato defect in green coffee before it is roasted.  Both Bill and Shraddha were excited and decided to work with Rwanda’s National University and National Coffee Board to try and figure out how we can identify the presence of the ‘pyrazine-based toxin’ in the green bean before it is roasted.

We then started cupping sorted defected parchment and green coffee in Rwanda from different coffee washing stations to see if we couldn’t get samples with a high frequency of potato defect to use in Shraddha’s laboratory experiments.  We were able to identify and send several samples that will yield a minimum of 10% potato and a 30% max.  That was good enough for Shraddha to pursue her study.

A few weeks ago in Rwanda, Shraddha informed me that she was having some pretty positive results at identifying the green samples with high potato.  We took some more samples and she returned to Texas A&M to continue the experiment. I will have her write a brief summary of her findings so far to me that I will post early next week.  Should be interesting.  She was excited with the progress.

Here is Shraddha (far left) with Dr. Bill Payne and SPREAD’s Jean Marie Irakabaho at a cooperative in Maraba taking samples of suspect parchment.

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