With coffee, it’s hard to tell what’s right or wrong and what’s opinion or fact. Some will say buying pre-ground coffee is better, whilst others prefer whole beans (ground themselves). Pre-ground coffee is easy to use and convenient, however, fresh ground coffee is ultimately the best option if you’re after the best brew possible.
As soon as you grind your coffee beans, you start the ticking clock of their freshness. Grinding coffee brings out the flavour and aroma of your coffee, but if left for too long, ground coffee will fall victim to the elements and turn stale. In fact, ground coffee can only stay ‘fresh’ for just over a week after grinding – something to think about! Even with vacuum packed coffee grounds, they lack the freshness obtained when grinding coffee beans yourself.
There are a number of factors that contribute to this degradation: oxidisation, moisture, CO2 depletion and contamination.
Oxidation
During the oxidisation process, compounds present in coffee beans interact with air molecules to create different molecules. It’s this process that creates those desirable aromas and flavours, often associated with freshly ground coffee.
The oxidisation process starts as soon as you begin grinding the coffee beans. Great news if you intend to brew your coffee within the next 10 minutes. Not such great news if you’re leaving it for longer.
As oxidisation is what releases these unique flavours and aromas, by brewing with a fresh grind, you ensure you extract everything your coffee has to offer.
Moisture
Moisture plays a key role when it comes to the quality of your coffee. Atmospheric moisture can begin to dilute your coffee beans, creating a loss of natural oils (which is where those lovely flavours and aromas come from!). The oils in coffee beans are extremely sensitive. Moisture in the air or from an air conditioning unit is enough to weaken the quality of your coffee beans. Pre-ground coffee beans are exposed to moisture for longer (even if air-sealed), so experience a faster loss of precious oils.
Every time you grind your coffee beans, you increase the surface area which fastens the dilution process. Pre-ground coffee will lose most of its associated oils on the shelves of the supermarket. If you freshly grind your coffee beans at home, instead, you’ll be able to enjoy a greater concentration of those oils.
CO2 depletion
Carbon dioxide is the main compound that transfers the oils present in the beans, into your brew. Every time you grind the beans, you increase the surface area for carbon dioxide to escape from.
However, if you are brewing immediately after grinding, your coffee grounds will have enough CO2 to transfer the oils into your coffee. This creates a higher concentration of these oils in your coffee, therefore enhancing its flavour and aroma.
If you’re not going to consume your ground coffee straight away, it’s important to consider proper storage to retain CO2 content.
Contamination
Within your busy kitchen, odours can move around freely. These odours can infuse themselves to your pre-ground coffee, contaminating it and ultimately affecting its flavour (onion flavoured coffee anyone?). Buying whole beans is the better way to enjoy the full flavour of coffee, without the risk of contamination.
Can we keep pre-ground coffee tasting fresh?
Can we stop the degradation process? Sadly not, but we can slow it down significantly.
The most important component to minimising coffee degradation is to keep it in the correct environment. Exposure to oxygen, extreme temperatures and light will all have an impact on the degradation process. It is best to store pre-ground coffee in a vacuum-sealed, opaque container. Avoiding the fridge and considering the temperature and moisture of the environment the ground coffee is kept in is paramount to keeping your coffee tasting fresh.
When pre-ground coffee could be the better option
When you don’t have a quality grinder, it may be more convenient to buy it pre-ground. A local roaster or coffee shop may have a high-quality grinder on site though, so consider getting your beans ground there when you purchase them.
It may be common knowledge that freshly ground coffee tastes better than pre-ground (have you been reading this article…?), but this assumes that the two are ground in the same way. The best way to see which tastes best is to purchase the same coffee, one in whole bean form and one pre-ground. You can then make your own decision.