Joe Arsenault: The science of brewing coffee | Behind the Science


Welcome to another episode of
Behind the Science, Rockstar edition. I’m your host,
Jennifer Fournier. Recently, I was at my
favorite coffee shop, and I’ve noticed a new
alternative to my iced coffee– cold brew coffee. In this episode of
Behind the Science, we are going to explore the
difference between hot brew and cold brew coffee… … to find out what all
this brew-ha-ha is about. Hey, Joe, how are you? Hey, good morning, Jen. I am doing great. How you doing today? Great. What are
you drinking there? I am drinking cold brew coffee. Cold brew? I’ve heard of it, but
I haven’t tried it yet. It’s one of my favorite
beverages right now. You’re familiar
with regular coffee? I am. And iced coffee? Love iced coffee. Regular coffee and iced coffee
start at high temperature– Mm-hmm. –when you actually brew the
coffee at high temperature. Ah, so they brew it
and pour it over ice? Correct. OK. Whereas with cold brew, we actually brew it in the refrigerator. Oh, I bet that
takes a lot longer. Yeah, it takes about 10 hours– Wow. –because everything is
coming out more slowly. What we’re going to focus on
is the extraction process, which is actually
something that, in liquid chromatography, when
we’re trying to get samples out of things that are solids, like
meats or vegetables and things like that, how we
extract the chemicals out is very important for
us to do our analysis. So let’s take a look here. The difference in hot
brew versus cold brew is the extraction
temperature of the water. They’re both using water. In cold brew, the water is roughly about 40 degrees centigrade. And in hot brew the water
is roughly close to boiling. The difference in
those temperatures creates a very
significant difference in the amount of compounds
that come out of the coffee. When the temperature is very
high, a lot of compounds can come out that
would normally not, because at high temperature,
a lot of those compounds that are coming out are very bitter. Ah, yes. And because we’re at high
temperature, over time they also oxidize and
get even worse in taste. That’s why a lot of places
will take their coffee and throw it away after
about 30 minutes– That makes sense. –because those
compounds are actually unstable at high temperature. Whereas with cold brew,
they’re very stable, and you can leave it in the
refrigerator for two or three days and it never
changes its flavor. Wow. So you know what this calls for? A taste test! Actually, I have one set up. You want to go try? Let’s do that. All right. OK. Great, it’s still here! They’re still there. Great. So this is a taste
test that I set up. Perfect. Now, as you can see, they
look exactly the same. Exactly. But on this side we have
cold brew iced coffee, and on this side we have
just regular iced coffee that you typically get. So what I’d like to
do is see if anybody can taste the difference. Perfect. Now, let’s see if
we can get anybody– Carol, actually,
can I borrow you– Hey.
–for a minute? Of course. Would you humor me and
do a taste test here? So we have two
ice coffees, and I want to see if you can tell
if there’s any difference. All right. So let’s try with
this one first. What did you think? It’s a little bitter. A little bitter? Just a bit. How about this one? Mmm. It’s a lot smoother and sweeter. Mmhmm. A-ha! See I told you. Science wins. Cold brew coffee actually
will taste sweeter, smoother, and some people
will prefer it even without milk versus
the hot brew coffee, in this case here that’s
been chilled with ice. So what we’re going
to do now, Jen, is go back and take a look
at some of the science behind all of these
differences between how we brew our coffees. Great, let’s do it. OK. Now, when we actually
look at the chemistry from an analytical standpoint,
in a hot brew cup of coffee, you have roughly
1500 compounds physically in that cup of coffee. If we extract that
same coffee ground– so that’s the only
control difference is temperature now of
the water extraction– at cold temperatures,
we only get about 1000. And those 1000
compounds tend to be more sweeter and flavorful. So you see there’s actually
a very big difference in the chemistry
that we’re actually getting when we order either
a hot brew or a cold brew cup of coffee. Joe always has all
this great knowledge about the recent trends
in sample extraction and purification. If you would like to learn more
about what we talked about today, please go to the link below, where we have a similar
application note that describes extraction
techniques for tea. And join us next time
for another episode of Behind the Science,
Rockstar Edition.

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