Have you ever wondered what the holes are on certain coffee bags? As from the title of this article you can guess some type of gas is involved and you’d be correct!
An important learning curve for us was understanding the wealth of processes that occur when beans are roasted. They go through a combination of chemical and physical processes as they are heated endothermically and exotermically and move from green bean to yellow bean to golden brown coffee bean (any darker and you get a burnt bitter bean!). Oils and sugars are released from the beans chemically as they darken and the beans harden and shrink physically as they impart water and volatile compounds.
An even bigger discovery for us was that beans continue to develop independently off the roast for up to 5 days after, and a key way in which they do this is by releasing gases. A byproduct of roasting beans is the build up of nitrogen and carbon dioxide gasses within them, which is important to know for 3 reasons:
1) You shouldn’t drink and judge coffee off the roast as it inherits what only can be described as a fizzy carbonated taste.
2) Knowing the roast date can help you understand how fresh it is, hence why we include this on our packaging. As an average benchmark 4 days to 3 weeks off the roast is when coffee beans are generally at their freshest and best.
3) Most importantly…to ensure this bean development doesn’t hinder the flavour of the beans you need to release these gases whilst keeping the beans fresh.
As a veteran coffee buyer I’ve bought my fair share of coffee, and a way in which most good coffee roasteries including ourselves keep beans fresh by using one way gas valve packaging as part of our quality control. This helps by reducing oxidation of the beans in a sealed container to decrease the rate of staleness, but also releases unwanted gases through the one way gas valve to help them develop. Without this valve the beans release these gases to only be surrounded and absorbed back into them, which from experience and tests we carried out flattens their flavour and punch so to speak.