The Caffeinated Astrophysicist | The Press

The image of the geek of coffee” which weighs everything, measures everything, has all the latest and most efficient gadgets to achieve the most “perfect” infusion possible, Jonathan Gagné embodies it more than anyone. The astrophysics researcher has a very specialized blog on coffee, entitled Coffee Ad Astra (“Coffee to the stars”). He also published the book The Physics of Filter Coffeein 2020.

Eve Dumas
The Press

Jonathan is therefore not geek to be geek ! The researcher at the Rio Tinto Alcan Planetarium and assistant professor at the University of Montreal wants to advance the science of coffee and he has amassed a loyal readership over time, all over the world.

“The blog first became known in the United States, where the culture is more developed,” he says. It’s more mainstream to be a little manic with your coffee in the United States. The community here is quite small. If you go to random people, you’re not often going to find super expensive big grinders. People think I’m pretty weird with my water concentrates and my telescope grinder! »

The passion was gradual. It began in the first specialty cafes in the metropolis.

On exchange in Pasadena, east of Los Angeles, during his doctorate, he continued his quest for the best infusions. That was in 2014. “I discovered Copa Vida, where a different single origin espresso was served every day and the variety fascinated me. »

During his postdoc in Washington, at the Carnegie Institution for Science, he became even more interested in the different microroasters and saw how much the quality varied. Today, his favorites are: Regalia (New York), Luna (British Columbia), the Colorful range (coming soon!) from the Canadian Roastery Company (Montreal), Escape (Montreal) and Standout (Sweden), among others.

Jonathan likes to think back to his time at NASA’s Infrared Telescope Facilities (IRTF) in Hawaii in 2014. “There was just an old, stale can of Folgers. So I decided to buy myself a V60 infuser and a manual grinder and I started making filters. One day out of five, the coffee was good. Other days he was okay or really terrible. I had a little frustration with that. »

After three years in Washington, the astrophysicist returned to Montreal. And there, his coffee really took a bad turn. Finally released from his intensive studies, Jonathan was able to look into what was wrong with his morning pick-me-up.

Having not yet installed a reverse osmosis system at his home, as many Montreal cafés do, Jonathan prepares his own water. “The easiest way is to buy water like Volvic or Smart, which are reputed to be the best for making coffee, but it’s not a very ecological solution. Another quick fix would be to cut tap water with distilled water, since Montreal water contains twice as much bicarbonate. »

Even more experiences

Jonathan’s next stage of “geekification” was triggered by reading the works of Scott Rao, American authority on coffee, who is also a partner of the Canadian Roasting Company, where no less than 25 Montreal microroasters “roast” their Coffee.

“I wrote an entry about water on my science blog for my coffee-loving co-workers in astrophysics. Then the VST company offered me a refractometer, to measure the concentration of coffee. It left me on other experiences, which led to other posts. So I separated coffee from astrophysics on my site, then circled around filter coffee. I told Scott that I was tempted to do a book. He helped me. »

Father of a 2-year-old daughter and spouse of a tea drinker, Jonathan has slowed down his research a little since the publication of the dense book. However, he seems to have put his finger back in the gears, that of espresso this time, an even more complex subject, says the researcher. Can we expect a volume 2 by Jonathan Gagné on the physics of espresso? “Maybe, haha! he replies.

What physics tells us about brewing coffee

By Jonathan Gagne

water temperature

A higher temperature speeds up the extraction and changes the profile of what is extracted. It also speeds up the flow of water a little because it is less viscous at higher temperatures.

The coffee grind

Grinding has several effects on the extraction and flow of water. A finer grind speeds up extraction (much like a hotter water temperature) and it also allows the water to access a greater fraction of the solubles that hide in the coffee particles, given the greater contact surface with water. However, a finer grind will tend to create more coffee dust, which can interfere with even water flow, clog paper filters, and even partially pass through filters and end up in the coffee cup. Coffee. This last aspect is not necessarily a bad thing, the impact will be to increase the perceived “body” of the coffee and to somewhat mask the tasting notes which are specific to each origin.

Flow

Water flow is very important. It affects the extraction time. The uniformity of this flow through the coffee has a great impact on the taste of the resulting coffee. When the flow is not uniform, the perception of astringency will increase; it’s a feeling of constriction on the tongue caused by long molecules that are cousins ​​of tannins. It turns out that astringency doesn’t mesh very well with the taste profile of most coffees and significantly reduces the sweetness sensation and perceived complexity. We generally try to avoid it.

Extraction

The degree of extraction has a big impact on the flavor profile you get. About 30% of the coffee particles can be extracted into water, the rest being made up of insoluble cellulose (it’s a bit like wood). If you extract only a small fraction of a coffee with a light roast, for example 15% or half of the solubles in the particles, you will obtain a relatively acidic cup of coffee, with a lower perception of sweetness. Pushing the extraction a little further towards 20-25% typically results in a cup with greater complexity, with greater sweetness that combines with the acidity to give the impression of a juicy and juicy cup. more fruity. Going over 26-27% (depending on the equipment) often results in a less pleasant taste profile. This obviously depends very heavily on the coffee used, the degree of roasting and the equipment used; darker roasts tend to be enjoyed with generally lower degrees of extraction, and higher performance grinders will typically allow higher degrees of extraction to be achieved before running into the less appealing tastes and other problems due to uneven water flow.

Restlessness

The agitation helps to ensure that each coffee particle makes good contact with the water and allows for a more even extraction. However, it can also interfere with effective filtration, as the coffee itself is an important part of the filter (one paper alone does not filter everything). Too much agitation can also allow more coffee dust to reach the paper filter and may risk clogging it. Stirring is therefore a tool to be used with care, but which can be very beneficial when preparing a for over, manual filter coffee.