When you start to get into specialty coffee you learn a few golden rules. One is that you should always use freshly ground coffee and that pre-ground coffee is stale. But is this true?
Let’s take a look at when it makes sense to reach for a bag of pre-ground coffee instead of grinding your own.
Reasons To Avoid Pre-Ground Coffee
Why do we grind coffee at all? To increase the surface area of the roasted coffee bean and allow better extraction of the flavors and aromas within the coffee. If we placed whole roasted coffee beans in water, they might eventually extract into a weak brew, but it would probably take a long time and lack the flavor notes we enjoy.
Grinding coffee means that more of the bean is exposed to the water. This allows the compounds to dissolve into the water more quickly and more compounds can be extracted. Understanding the basics of extraction is important for understanding the pros and cons of pre-ground coffee.
When coffee is ground, this same increase in the surface area leaves the coffee more open to environmental exposure.
Coffee open to oxygen degasses – meaning that it releases the gases built up during roasting. Degassing is important to avoid your coffee being under-extracted and tasting bad. Carbon dioxide creates carbonic acid in the cup, which is unpleasantly astringent.
But grinding increases degassing. If you grind coffee and leave it open to the air, more flavors and aromas will be lost. When coffee loses all of the gases, it can create a flat brew and taste stale.
Similarly, ground coffee is more vulnerable to moisture. When roasted coffee gets damp, it affects the oils that contribute to flavor.
And the relative amount of surface area is also why a finely ground coffee will get stale more quickly than a coarse grind.
Coffee that has lost its gases and oils doesn’t taste great. That’s why pre-ground coffee has a bad reputation. Why take the time to source quality beans, roast them to the perfect level, grind, and then just let them sit there losing flavors?
Ken Selby, is the 2018 winner of the US Cup Tasters Competition. He tells me that “the experiential difference that you’re going to find [using pre-ground coffee] is two things. Aroma and acidity will be very minimized compared to if it was ground fresh”.
Can We Keep Pre-Ground Coffee Tasting Fresh?
So, what can we do to stop the degradation process? Nothing. But we can slow it down considerably.
The same recommendations we make for storing whole beans can be scaled down for ground coffee. The important part is to minimize the coffee’s exposure to environmental factors including oxygen, extreme temperatures, and light.
This could be as simple as a mason jar inside a cupboard. Ken tells me that the ideal way to store pre-ground coffee is in vacuum-sealed, opaque containers. And avoid the fridge. The extreme temperature and moisture aren’t good for maintaining flavor.
But Isn’t Freshly Ground Always Better?
It’s one thing to minimize deterioration of flavor, but isn’t it always better to grind your beans freshly for each cup of coffee? Normally yes, but not in every case.
When we grind the coffee, we are reducing it into lots of tiny fragments. If you use a blade grinder or low-quality burr grinder, you will create an inconsistent grind made of differently sized and shaped fragments.
Inconsistently ground coffee means inconsistently extracted coffee. Let’s go back to extraction. Compounds from your coffee beans dissolve into the water at different rates. First, you get acidity, then sweetness, then bitterness. When brewing coffee, the goal is to get the right balance of all of these compounds.
With consistently ground coffee, you know that every particle is extracting in the same way. This allows you more control over the flavor and aroma.
With inconsistently ground coffee, some particles will extract more quickly than others and you could get a muddy or over-extracted cup. It’s impossible to control the parameters and reproduce a technique when you use these randomly sized particles.
A low-quality grinder will produce tiny coffee fragments known as fines. They will extract very quickly and cause bitter flavors through over-extraction. It may also leave you with boulders, large pieces that won’t fully extract and will introduce sour flavors.
Alex Choppin is a Support Specialist at Baratza, which manufactures burr coffee grinders. He tells me about the importance of a reliable grinder in making a great cup of coffee. “The first big step is quality coffee, the second big step is a grinder that can do the right job for that coffee,” he says.
So if you’re looking to improve your cup, take a look at your grinder. Is it producing consistently ground coffee? If it isn’t and you can’t afford to invest in a new one, consider using coffee sieves to separate the fragments.
When Pre-Ground Coffee Could Be Better
When you don’t have a quality grinder, it may be better to use pre-ground coffee. Your local roaster or coffee shop may have a high-quality grinder. Why not consider getting your beans ground there when you buy them?
If you buy in small amounts and store the pre-ground coffee well, you could get a better cup of coffee than if you had ground the beans yourself.
Alex compared a week old pre-ground coffee against beans that were freshly ground using a cheap blade grinder. He found that the pre-ground coffee was better than the blade-ground one.
“I think that was the most surprising to me, I was so sure that even badly fresh ground coffee would beat pre-ground. But up to a week, it was still solid. It held its own,” he says.
“In my experience, pre-ground coffee, if it’s not too old, is probably going to out-perform blade ground coffee”.
Ken says, “It might sound counter-intuitive, but I would prefer pre-ground from a nice grinder than using a blade chopper”.
But remember that finely ground coffee deteriorates more quickly. So if you’re using pre-ground coffee and storing it, it’s better to choose a coarse grind.
It may be an established rule that freshly ground coffee is better than pre-ground, but this assumes that the two are both ground in the same way. If you don’t have a good-quality grinder, you may be better off asking your roaster to grind for you.
Why not try comparing cups made with freshly ground beans that you ground yourself and some pre-ground ones? You might be surprised.