Last November, we were wondering how vital it is to store our green coffee in airtight bags while they were in production. The vast majority of our coffees arrive in GrainPro - that is, with a plastic lining inside the jute sack to protect the beans from the atmosphere, which keeps them tasting fresher for much longer than traditional sacks. However, once we open the bag to start roasting that coffee, it’s exposed to the atmosphere. We wanted to see if this was impacting our coffees and if we could do anything about it
We decided to take two 100 gram samples from the same bag of coffee. For those interested, the coffee was our Los Pirineos from El Salvador. We took the samples on the 16/11/16 and sealed one in an airtight bag, and left the other out in a sample tray. We roasted them on the 20/06/17. Before roasting them, we recorded their moisture content. Moisture content is very important when it comes to roasting coffee. It affects how we decide to roast, as more moisture allows more heat and vice versa. If the moisture content is too low the coffee can taste dry and hollow, and if it's too high it runs the risk of producing mould. The optimal moisture content is roughly 9.5 - 11.5%. The samples we took both had a moisture content of 9.7% in November, and we recorded the moisture content again before roasting them last week. The sample we kept in the re-sealable bag was 9.3%. Not too bad at all, however the sample we left out in the sample tray had dropped an incredible 2.4% to 6.9%.
After roasting (attempting to roast as similarly as possible), we allowed a day for the coffees to rest and degas, we then cupped them. I set up the cupping and didn't tell the team what we were cupping for. We always cup blind (hiding the info of the coffees) to help minimise bias.
Although the results seem logical, we feel it is always good to carry out these tests for ourselves. You can read or be informed about the effects of something over and over, but seeing it - and tasting it - for yourself is a different story: that's when it really hits home.
After the cupping we got our heads together, we are now working towards repackaging some of our coffees when they arrive into vacuum sealed roast size batches. Although in reality our coffees don't hang around the roastery aslong as in this experiment, so the effect on flavour is likely to be smaller than we tasted here, we are all about marginal gains, and getting the best from our coffee.
Darren Kelly - Head Roaster