Grinding-79 degrees below zero-the most demanding and perfect grinding temperature for coffee!

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Why is the coarse ground coffee powder suitable for trickling filter-the common grinding thickness diagram of coffee powder

On April 23, 2017, an unexpected champion appeared at the Coffee Masters in Seattle, USA. Mr. Kyle Ramage, from North Carolina, stood out from the 36 best baristas in the United States. He doesn't work as a baker or bartender in a cafe. He works for the American arm of Mahlkonig, a bean grinder brand. The year before, Kyle took part in the competition, but screwed up the Italian enrichment program in the regional trials and didn't even make it to the national competition.

In this American race, Kyle used Panamanian rose summer, the same bean sun and honey treatment, but the focus was not on his rose summer, but on the antifreeze gloves he was wearing on the court, which were particularly weird on the court, but absolutely necessary because his coffee beans were kept at minus 79 degrees Celsius (- 79 °C) before being thrown into EK43 grinding.

Why did you lower the coffee beans to such a low temperature? Kyle said: 'when frozen, coffee beans become very fragile, especially below minus 50 degrees Celsius, which has a positive effect on grinding, resulting in a more uniform and uniform grinding, resulting in a sweeter and more delicious flavor.' The idea was not invented by him out of thin air, but from a multinational independent experiment three years ago.

In fact, in the past three or four years, the research on the influence of extraction flavor in boutique coffee industry has entered a new field.

In coffee extraction, there are many factors that affect the flavor: water temperature, pressure or flow rate in Italian brewing, extraction time, interaction of chemical components in coffee and water, etc., these factors are extremely complex. Traditional high-end flavor research and experiment, although baristas have the ability of technology and taste, most of them can not be involved, and the most cutting-edge research can only be carried out in equipment manufacturers. Whether they are Italian coffee machines or bean grinders, they have state-of-the-art and sophisticated instruments that can measure subtle variations under different extraction settings. Ordinary baristas are unarmed and it is extremely difficult to complete rigorous research on their own.

Reflected in the competition, the eye-catching innovations come either from baristas' cooking methods, or from special treatments or raw bean varieties.

The first person to break this situation was Matt Perger of Australia, who became familiar with the use of EK43 when he won the World Cooking Competition (2012). After WBC with the theme of grinding superiority of EK43 in 2013, he released research on grinding and three comparative reports on the diameter distribution of EK43 and other bean grinders, which not only pushed the 30-year-old EK43 to the peak of the bean grinder market, but also led the way. As an independent barista, complete an objective and scientific report.

Of course, we can not but notice that the second research on powder diameter distribution is Perger in October 2013 to the Mahlkonig factory in Hamburg, Germany, using the "laser diffraction powder diameter analyzer" (laser diffraction particle size analysis) to measure the powder diameter of grinding particles and its overall distribution in order to complete, boutique coffee industry for the first time to see a beautiful bimodal powder diameter distribution map, but also the first time to know that equipment manufacturers have this kind of precision instrument.

Matt Perger, a large team of independent baristas and scholars from Britain, Australia and the United States, launched a more objective and in-depth experiment on grinding in 2014, including British Perth chemist Christopher H. Hendon, Perth Cafe owner Maxwell Colonna-Dashwood and his wife Lesley Colonna-Dashwood, Melbourne's Matt Perger. And a number of scholars from the Department of Chemistry of the University of Southern California in Los Angeles, the Department of Physics of the University of Melbourne in Australia, and the Department of Chemistry of Perth University. In this experiment, the cooked beans needed in the experiment were provided by three bakeries such as Has Bean Coffee.

This unprecedented transnational independent study laid the theoretical and experimental foundation for Kyle Ramage to grind beans at low temperature in the competition. In 2015, the study was published in the American journal Nature in the form of a scientific paper entitled "the effect of the origin and temperature of coffee beans on ground ripe beans" (The effect of bean origin and temperature on grinding roasted coffee).

Many people took part in the experiment, but the souls were Maxwell and Christopher Hendon of Perth, England, who studied the chemical composition of water intensively in 2013 and 2014, and published Water for Coffee in 2015. The difference is that in the study of water, they deal with chemistry, that is, the interaction between trace chemicals in water and coffee, as well as the effect on flavor, but when it comes to grinding, they follow in the footsteps of Perger, dealing with physics, studying what factors affect the size and distribution of grinding particles.

They hypothesized that there are two factors that affect the grinding, one is the origin, treatment and roasting degree of the coffee beans, and the other is the temperature of the coffee beans during grinding.

The choice of these two factors actually comes from the tacit or controversial assumption in the boutique coffee industry that different coffee beans behave differently during grinding. for example, some people may think that lightly roasted or dense beans will produce more "fine powder". As for temperature, some equipment will think that heating will make the size of the powder more uniform. For example, the Mythos bean mill holds this theory. But the common sense of the coffee industry (not a consensus) and the debate on different positions, it is difficult to confirm who is right and who is wrong without strict experimental observation.

In order to understand the first set of factors, that is, the influence of origin and treatment, they used four beans in the experiment, including Kaddura and Bourbon in Guatemala, Pacamara in El Salvador, Red Bourbon in Tanzania, and the native species of Sasaba in Ethiopia. Except for Sasaba, the other three beans were washed in water. The baking degree of baking is also different, the first three are semantic baking, the Agtron value is 59 or 62, the last Sasaba is manual baking, the baking degree is 68, relatively shallow.

As for the second set of factors, the team put the roasted coffee beans at four very different temperatures, which were 20 °C at room temperature, cooled to-19 °C in a commercial refrigerator, and cooled to-79 °C in a commercial refrigerator. finally, the temperature of coffee beans is reduced to-196 °C with liquid nitrogen.

How to measure the effect of grinding? Following in the footsteps of Perger, the team also measured the "powder diameter distribution of ground particles" (Particle size distribution), and the bean mill still uses Mahlk ö nig EK43, once again using the laser diffraction powder diameter analyzer provided by the British laboratory. The results were obtained in 2014, but published as a paper, and after strict publishing standards and peer reviews, it took another year, and many people were surprised when the boutique coffee industry saw the results in the journal Nature.

The conclusion is actually very simple. The first group of factors include raw bean producing area, bean seed, treatment method, and baking degree, which have no effect on grinding. Just because different beans have to adjust the bean grinder, or what kind of bean powder is more, are overturned by this experiment, adjusting the bean grinder must come from other considerations.

But the second group of temperature factors have a great impact. Because coffee is a substance without a specific shape, when the temperature of this substance is changed, it will sometimes go into the process of "glass transition", from as soft as rubber to suddenly as hard as glass, and some substances will even go into "shattering transition", so it will become fragmented particles. This is probably what happens to coffee in a bean grinder.

The experimental results show that the colder the temperature of beans is, the more concentrated the powder diameter distribution is, the smaller the difference between size particles is, and the more uniform the extraction is (- 79 °C or even more concentrated than-196 °C). The larger the surface area of the extraction is, the better the extraction rate is.

After earning his doctorate from Perth, Christopher Hendon went to the Massachusetts Institute of Technology in the United States to do postdoctoral research, and two of his studies with Maxwell were shown in the coffee contest. In the grinding of this year's American tournament and the water of the 2014 British trials, Maxwell won the British championship with a different flavor of coffee brewed in water, and then reached the finals at that year's WBC. He spent the first few minutes talking about water, but he didn't even start making coffee, and everyone pinched a cold sweat for him, trying to say whether he came to class or to compete. His final total score lost more than 100 points to the first English Izaki, only the fifth, a fiasco of the century!

Matt Perger participated in the World Coffee Masters WBC in 2013. Ben Kaminsky and Ben Kaminsky designed a set of different coffees around EK43 in order to explain the effect of grinding and different extraction rates on flavor, and was only runner-up by 11 points.

Grind's research made Kyle Ramage win the first place in this year's American trials. In an interview with reporters after the match, he said, "I do not represent the experimental results to participate in the competition, who will represent?" Kyle works in Mahlk ö nig, and the bean grinder used in the experiment is their EK43. Yes, if he doesn't wear those gloves, who will?

If the scientific research or experiments done by independent baristas do not fail, if there are really achievements and discoveries, this discovery also belongs to the world and will not become the patent of the manufacturer. it becomes a mysterious and expensive design that you can't see in a newly listed machine, but a public material that all coffee-loving and speculative people can repeat experiments, tests, and debates. Their greatest application, that is, on the field!

This is why we should pay deep tribute to all the contestants who try to explain the results of their scientific inventions or experiments in the competition, no matter how lax and trivial the experiment is.

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