Some people might wonder why coffee experts only use freshly ground beans in their brew; and the main reason for that is that, when coffee is ground, the oils that give it its unique taste and aroma start to degrade immediately after. This is due to three main factors: moisture, oxidation, and CO2 depletion.
Oxygen plays a crucial role in the flavour and aroma of roasted coffee beans. These are rich in volatile compounds that are responsible for the complex flavours and aromas that we associate with our precious brew. However, once ground, these volatile compounds are exposed to oxygen in the air, which causes them to start to oxidize and degrade.
The role of moisture is also quite significant in the quality and consistency of a coffee brew. In the case of ground coffee, because there is more exposed surface area coming in contact with the air, more moisture is absorbed. This can affect flavour and quality as it causes the grounds to become stale more rapidly by diluting
The third factor that comes into play when coffee is ground is CO2 depletion. When coffee beans are roasted, they produce carbon dioxide which is then retained within the cells of the beans. The gas is released slowly over time and helps to preserve the freshness and quality of the coffee plus it is an essential component in coffee extraction as it helps to dissolve the coffee oils and other soluble compounds during brewing.
However, when coffee beans are ground, the increased surface area causes a rapid release of carbon dioxide. Within 60 seconds of grinding, up to 80% of the carbon dioxide is lost. This loss of carbon dioxide will have a significant impact on the quality of the cup. When carbon dioxide is depleted, the coffee oils and other soluble compounds are no longer dissolved effectively, resulting in a weaker and less flavourful brew.
Brewing coffee immediately after grinding ensures that your coffee grounds will have enough CO2 to transfer the oils into your brew. This results in a higher concentration of oils and therefore more flavour, sweetness, and aroma. Improper storage of coffee grounds can lead to a quick loss of CO2, and grinding the beans worsens the situation. If you allow coffee grounds to sit for many hours or days, you are simply wasting this key component.
In addition to these three major factors, coffee oils are very delicate, which makes them an easy victim of contamination. Whatever odours are close by will taint your coffee and will not contribute to your coffee tasting experience.
I hope you enjoy it, next week we'll be posting about ideal grind grades for different brewing methods.
Have a great weekend,