The Sound of Science - "Coffee"

Aug 10, 2018

Kate: Welcome to the Sound of Science on WNIJ. I’m Kate Powers, and today’s question comes from Alex who wants to know why coffee tastes so weird. With me is STEM Outreach’s resident coffee enthusiast Sam Watt. Sam loves his coffee so much, he even went out of his way to pick and roast his own coffee in a coffee grove in Cambodia!

Sam: That’s right! And, yes, coffee can taste a bit strange to some people. There is a whole lot of chemistry in a mug of my favorite wake up juice. Coffee is about 98 percent water, but the other 2 percent is what gives coffee it’s taste and properties. The most well-known and most appreciated compound is Methyltheobromine. You might know it as caffeine. Another compound is acetoin, which gives it a rich buttery aroma.

Kate: And the taste? What about the taste? It’s bitter and it can taste burnt, but sometimes it tastes pretty good by itself.

NIU STEM Outreach

Sam: The bitter taste mostly comes from caffeine, which is why most energy drinks have a lot of sugar. It’s also bitter because of a compound called trigonelline. However, with just the right amount heat, trigonelline breaks into dozens of other compounds, and each one of these contributes to the overall taste. The compounds that come out all depend on the Maillard reaction.

Kate: The Maillard reaction? Is that like the coffee brewing process?

Sam: Nope, the Maillard reaction is probably your favorite chemical reaction. It occurs in most foods when cooking or brewing. The resulting browning and charring comes from the breaking down of proteins and sugars to give a savory flavor. Cookies, s’mores, and seared steaks all become super tasty with the Maillard reaction.

Kate: Stop, you’re making me hungry! And what does that have to do with coffee?

Sam: The different coffee beans and how they’re roasted results in different proportions of proteins and sugars. Different beans and different roasting methods result in different proportions and types of proteins and sugars. These different proportions cause coffees to taste differently. But bad coffee is bad coffee. If the coffee is too hot, the Maillard reaction continues and produces bitter and unpleasant compounds.

Kate: Well there you have it! You just need a little basic chemistry every morning to get you going! I’m Kate

Sam: and I’m Sam. This is the Sound of Science on WNIJ

Kate: Where you learn something new every day.