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CTI: Coffee t&i
Chris: Dr. Christopher H. Hendon

Q&
Q&A

CTI: “At a coffee shop, freezing beans is especially CTI: Any advice for distinguishing relevant and
impractical. Baristas cope with the morning rush by qualitative data and instruments?
having a hopper full of beans ready to grind at the Chris: Sure. You need to first determine what you are
flip of a switch. Making coffee from individually trying to measure and why. For example, I might want to
frozen packets of beans would take too long. In this measure how much coffee by mass I have extracted. But
sense, the current study may be tantalizing as much why? The answer I will leave for you to discuss, but I can
as anything else — after all, lots of folks need coffee tell you that the ‘why’ to this question does not provide
to wake up, but it’s only going to be the early risers insight towards our end goal: tasty coffee.
who get the best cups.”How do you see this com- The most valuable method for distinguishing if a
ment? Do you agree? device is proving valuable data is if it is reporting in SI
Chris:Freezing coffee is certainly more challenging than units. For example if you want to measure a flow rate the
a typical workflow in a cafe… but the benefits might out- device would need to report in units of volume per time
weigh the cost of training the staff to efficiently work with (e.g. 3 mL/s). A device that reports in some arbitrary unit
a single dose grinder and a freezer. If you are a typical café is not flawed, but does require further inquisition. I trust
with high volume peaks throughout the day, you might thermometers, pressure gauges and time.
actually find the freezing allows you to achieve higher
quality consistently, because you don’t have those ‘hot’ CTI: Did you collaborate with Kyle, expand your
periods as the grinder cools. findings to specific beans and grind level?
I don’t think that the study is intended to change the Chris:I have known Kyle for many years. He contacted me
way we make coffee in cafes. In fact, quite the opposite. to tell me he wanted to use this cold coffee idea in his
I think that the study explains and clearly shows that routine. I was excited, I like competition. He asked for
temperature affects the physics of the grinder. Whether the same graph that we published, but a little bit less com-
you then go and start monitoring burr and bean tempera- plex (we removed the freezer and liquid nitrogen tem-
tures is up to you, but it should have emphasized the im- perature traces). Note that in the Sci. Rep. paper, we
portance of this knowledge. showed that all beans ground the same, independent of
I do believe, however, that the ‘early riser gets the the origin, processing method, roast or roaster… so we
best cup’ is a terrible business model. Because this is didn’t need to expand the study beyond our as reported
simply not true. Once the grinder cools after the rush, the data. I just tell you what happens relative to room tem-
coffee should be the same as before the rush. It is just the perature, and you – the barista – then has to work out how
period during high volume grinding. to make it taste good.

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