There are billions of coffee drinkers around the world. Whether it’s the comforting routine of brewing a cup at home, or the necessity of the coffee shop next door to the office, it is pervasive in our daily lives.
But with anything as popular as coffee, there comes mystery. Facts, myths and general rules of thumb blend together, leaving some ambiguity on what is actually the correct way to do things.
How should coffee be stored? Am I brewing it correctly? Is decaf coffee fully decaffeinated? We spoke to Dr Christopher Hendon, a computational materials scientist at the University of Oregon, to answer the most pressing questions about your cup of joe.
1. Pre-ground and instant coffee actually have different levels of caffeine
Realistically, one of the best things you can do for your coffee from home is grind the beans yourself. However, that is both time-consuming and – depending on the equipment – a pretty expensive endeavour.
If instead you choose to go for the pre-ground coffee found in a supermarket, are you losing out on a spike in caffeine or is it all the same?
“The grinding process does not lose an appreciable amount of caffeine. However, typically pre-ground coffee from supermarkets has less Robusta in it than Arabica,” says Hendon. As he explains, Robusta and Arabica are the two main types of coffee beans used in commercial coffee production. Of the two, Arabica beans carry less caffeine.
“The problem with this though is it is hard to know exactly what exactly is in a coffee blend. They don’t normally put it on the label, so really the best choice with supermarket coffee is to follow what you like.”
It’s a different story with instant coffee though. Due to how it's processed, it has considerably less caffeine (less than half in many cases) than ground coffee in any of its forms.
2. You shouldn't store your coffee in the fridge
What is the meaning of life? Is free will an illusion? Should coffee be kept in the fridge? Questions philosophers have been asking for decades… probably. While we don’t have the answer to the first two, we can attempt to address the third.
And attempt is the key word here because it is surprisingly unclear. Fiercely debated, the question of where to keep your coffee has many caveats, so let’s just jump straight in.
The key issue with storing your coffee in the fridge, or even the freezer is the dampness. Coffee grounds need to be kept dry, and a fridge isn’t exactly the driest of locations. So, if your coffee is in the fridge, it needs to be kept in an air-tight container to keep away any moisture.
"Coffee is primarily a sort of nasal sensory experience. When you take a sip, a lot of the flavours come through the back of the tongue and nose. The molecules that tend to give you that experience are pretty volatile and can easily evaporate. Coffee stored out in the open will lose those molecules over time. And at higher temperatures, that process accelerates,” says Hendon.
There are a few caveats here. Firstly, this only really applies to people worrying about optimal flavour, most likely from high-quality beans that they plan on grinding at home.
Secondly, your coffee needs to be stored at a low enough temperature to make a difference. In other words, the fridge isn’t cold enough to be worth storing your coffee in. A freezer is necessary for achieving this result.
So is it worth doing? Along with the benefit mentioned above, freezing coffee beans can also help make a coarser grind, fracturing the coffee in a more even way than you would find with room-temperature coffee.
These are somewhat minute details and it is worth mentioning that not all experts agree on this. The advice given by most is to store coffee in the cupboard or a room temperature location. Like most things to do with coffee, it’s all about experimenting for the best result.
3. A cold brew doesn't contain more caffeine
Cold brew, the summer’s day coffee of choice, has a reputation. It is often suggested that cold brew is a far more caffeinated beverage than regular hot coffee, but is that actually true?
“A hot coffee brew has about twice the amount of caffeine in it. The reason is that at low temperatures, the amount of extractable caffeine is limited by temperature. The higher you go, the more you are able to get out,” says Hendon.
“That’s not to say it can’t be high in caffeine, but it isn’t because of the extraction method. It’s because the coffee-to-water ratio is so high when you’re making cold brew concentrate”.
You’ll very rarely be served concentrated cold brew as it is usually watered down or mixed with milk, making the average cold brew less caffeinated than a hot beverage.
4. You can't burn coffee
A common complaint made about coffee is that it has been ‘burnt’. This could be from a coffee shop or a cup that is made from home. So what is causing this taste, is the coffee being overcooked with boiling water?
When coffee is roasted, it is dropped into a heated drum, and over time, the coffee starts to cook turning yellow and then brown. If you cook it for a really long time, it will eventually go black.
These black beans are a dark roast coffee. To get to this point, the beans need to be cooked at around 220°C – well above the boiling point of the water you’re making a cup of coffee with.
“When you are brewing coffee, you are never going to be able to get that coffee back up to the temperature it reached when it was roasting, so it isn’t possible to burn it in the brewing process,” says Hendon.
“However, the coffee may have come out of the roaster with burnt-tasting molecules already contained within the coffee. The brew method allows you to access these, and some coffee shops do prefer these tastes, and it is popular amongst a lot of people”.
If you’re often getting burnt-tasting coffee, and it isn’t a flavour that you enjoy, a lighter roast is less likely to feature these tastes.
5. Decaff does not mean caffeine free
Like non-alcoholic beer, decaffeinated coffee is still coffee, and therefore is still going to include trace samples of one of coffee’s main ingredients – caffeine. But is it a noticeable amount?
“It depends on how the coffee was processed, but the decaffeination process is in principle very close to the 100 per cent removal of caffeine. However, every sample we’ve ever tested still has some amount of it,” says Hendon.
In other words, there is likely to be some caffeine in the coffee, but nowhere near enough to be noticeable or cause any effect on the drinker.
6. Light and dark roast coffees have similar caffeine levels
When browsing the aisles of coffee in the supermarket, or examining your local coffee shop's menu, you’ll likely have to consider the options of light and dark roasts.
For the most intense kick of caffeine, which is the best to go for? Some will tell you that a dark roast is the way to go here, but really, it doesn’t actually matter.
“The scientific literature suggests that even with crop-to-crop variability and differences in the bean, it all comes out in the wash. There isn’t really enough of a difference to note here,” says Hendon.
“It seems like roast profiles and origins do have fluctuations in caffeine, but it is certainly not consistent enough to note.”
The only difference to note with roasts is flavour. A light roast is more often delicate but more complex. Darker roasts, however, are often described as carrying a ‘deeper’ flavour with more simple tones – this can come out tasting like the more bitter of the two.
7. Coffee can taste vastly different depending on the beans
Coffee has a very personal taste, and not everyone is going to like the same flavours. There are darker flavours, fruiter-tasting beans, a good old-fashioned black coffee, and of course, the infamous Frappuccino… but what is scientifically best coffee?
“Coffee associations around the world have score sheets to identify high-quality coffee. Two of the most important parameters are perceived acidity and sweetness,” says Hendon.
“In fact, the ones that tend to score very high every year are those from Columbia Panama and Ethiopia and they taste like a bouquet of acidic flowers. These are the ones that tend to fetch the highest value, and they are quite dissimilar to the average high-street coffee.”
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