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The Purge

The Purge – switching between certified and non-certified batches without wasting coffee.

Those that could make it to our Full circle event this year will have heard the talk from Mark Machin about Organic coffee, something we at DRW have been passionate about since its introduction to the UK.

One of the most frequent issues that gets mentioned is that of the purge batch – or the intermediary batch required when switching from non-cert to certified coffee to avoid cross-contamination. This always perplexed me as in my roasting days, we never did this, and never had a problem. So, what has changed?

In short – nothing. Good old word of mouth has got around that this is required but it is not. I checked. This means that the value of one roast of your certified coffee is being wasted for nothing, and this need not be happening.


What absolutely does need to happen though, is that your roaster is provably clean when the coffee goes in. Audits are there to make sure the purity stays intact, coffee is not being artificially increased, and that volumes match. The whole point of using trademarks and logos is to demonstrate to your customers that you are not trying to game the system or bypass the checks. In short, as a roaster, your integrity is as good as you are requiring from the farmer.

Negating the option of using a separate roaster for separate lines (most of us are not in that bracket), how then to avoid the purge?

First to look at is scheduling. If you can build your supply pipeline carefully, then using the first batches of the day as organic means you should not have to worry about batches beforehand contaminating the coffee. If you have the volume to have a full day’s worth of roasting as organic so much the better. This is also an approach I have used with decaf, and is by far the easiest.

The sharp-eyed out there though of course will note that once I have finished, I will switch to non-cert coffee, and at some point need to switch back. Just turning the roaster off doesn’t guarantee that all the beans are out, so let’s look at your cleaning schedule.

Honestly, if there are beans stuck in your roaster after you have finished roasting then there is something wrong with your setup. Perhaps your airflow is just a touch too high and holding beans in the exhaust. Maybe your drum is not aligned properly, or perhaps your destoner has a spot that catches beans. All of these should be rectified anyway, but of course, budget may not quite allow for that or timings might not work. Here, is where an organic clean-out is suited.

A wipe down and clean of the roaster before organic roasting is easy enough to do. A quick drum inspection looking for any trapped beans is quick and easy, and lets you know if there are any problems with your vanes. Pay attention to the green bean funnel/loader, also to the cooling tray, and if you have a destoner, that too. Cleaning off the magnet is also recommended.

Make sure your cleaning spray is suitable for organic use; it’s a good idea just to switch the whole roastery over to this for ease. Draw up a check list and make sure it is followed and marked off before roasting. You can either do this on scheduled down time for a roaster (Friday afternoons was always a good one for me) or before start-up at the beginning of the day. It doesn’t take a long time and can be used as part of your start up checklist.

Once you’ve got all this in place, it’s just a matter of scheduling. Of course, customers don’t always order in nice, neat batches and there is always a chance you will need to roast immediately after non cert, but if you can make it work and it saves you de-certing a batch of certified coffee, it’s got to be worth a look at.