How do you take your coffee? This question usually refers to someone taking cream or sugar in their coffee. But what about the temperature at which we drink the coffee? The amount of variation in flavour that can be obtained by drinking the same cup of coffee at different temperatures can be eye opening.
There are several times when people will comment that the only way they can drink coffee is if it's piping hot. When asked why they don't like it when it's cold they say it's because it only tastes good hot. So we decided to do some research into this.
The Science
There have been many studies over the past 100 years that have tried to see the effect of temperature on how we perceive taste. These studies have generally focused on foods in the range of 20C to 37C and in this range as temperature rises the perception of sweetness and bitterness tend to intensify (1). The sweetness in coffee comes from the sugars that are developed in the roasting process whereas the bitterness comes from the caffeine. Coffee is usually drunk at temperatures much above the 37C range so what's happening to our taste buds in hot coffee temperature range? Well it turns out our taste buds are muted when consuming foods that are either really hot or really cold and our taste buds are especially limiting the amount of bitterness we're tasting at these temperature extremities (2). So based on this really hot coffee should taste less bitter than colder coffee.
Results
So we did a little very unofficial experiment. We brewed up some of our Ethiopia Konga coffee and tasted it at four different temperatures; right after brewing, when the coffee was mildly warm, when the coffee was at room temperature and when the coffee was cold (we put in the fridge). Here are the tasting notes for each of the temperatures:
Right after brewing - Dark chocolate, caramel, medium body, medium acidity. The coffee at this temperature didn't taste very "clear" (could be due to the muting of the taste buds from the high temperature liquid)
When coffee was mildly warm - Lots of berry fruit flavours, higher acidity (coffee tasted "fresh" and "crisp"), more flavour/clarity, smoother and more mellow than when it was hot, sweet caramel, medium body
When coffee was at room temperature - Very smooth and mellow, creamy/heavy caramel, acidity mellowed out a bit and body increased significantly
When coffee was taken out of the fridge - The berry tastes we had when the coffee was mildly warm became more citrusy, very nice sweetness (not like the caramel sweetness that we had before but more like white sugar), body became thin, acidity reminded me of drinking cold brewed ice tea made from black tea leaves.
Conclusions
At no point did the coffee taste bitter or even "bad" but the taste did change a lot throughout the temperature range! The one thing that we found very interesting for the mildly warm coffee was that instead of the bitterness increasing we found that the sweetness increased.
There are several reasons why people consume higher quality coffee but one of those is the lack of bitterness that you usually taste in cheaper mass consumer coffees (especially in the after taste). Our informal experiment here showed that instead of the bitterness increasing as the coffee cooled it was the sweetness that increased. Maybe the people that don't like to drink their coffee at temperatures other than piping hot just need to drink better coffee :)
Footnotes:
(1) Nutritional Needs in Hot Environments: Applications for Military Personnel in Field Operations.
(2) Think Room-Temperature Coffee Tastes Bad? Blame Cavemen