In its most basic form, a barista by definition is one who prepares espresso coffee beverages. However, its meaning is expanding to include what might be called a coffee sommilier, who is highly skilled in espresso preparation, with a comprehensive understanding of coffee, coffee blends, quality, coffee varieties, roast degree, espresso equipment, maintenance, and performance, Latte art, etc.
Tip # 483920 - Freshly ground coffee
We all know that it is important to use freshly ground coffee. Why? Because it goes stale of course.
But do many of us know what this actually means?
Try to think back to sixth form science and remember the definitions of the following words.
Oxidise 1: to combine with oxygen
2: to dehydrogenate especially by the action of oxygen
3: to change (a compound) by increasing the proportion of the
electronegative part or change (an element or ion) from a lower to a
higher positive valence
4: remove one or more electrons from (an atom, ion, or molecule)
Huh? Think of this as the degrading of the molecules that make up the oils and gases within the ground coffee. The same oils and gases that are essential in giving a shot of espresso its crema and body.
The rate of oxidation is relative to the surface area, which we will get to.
Hydrophilic 1:Having an affinity for water; readily absorbing or dissolving in water.
What? Coffee likes to absorb water from the surrounding atmosphere. The more humidity, the faster water will be absorbed. Although the absorption of water will not degrade the coffee, as oxidation will, it will affect your rate of extraction. Generally, the more water that is absorbed, the slower your extraction. Therefore, regular small adjustments of your grind are necessary to maintain optimum quality.
Surface Area: It is difficult to give a mathematically precise definition of surface area.
In fact, it is even fairly difficult to give a precise definition of a surface.
One definition of a surface is that a smooth surface is a subset S of R3
such that each point in S has a neighbourhood which is diffeomorphic
to an open set in R2
Anyway…….. We can think of surface area as the total amount of area that is exposed to the air. The greater the surface area, the faster the preceding effects will take place.
When we grind coffee, we dramatically increase the surface area. While these processes do occur when beans are whole, they happen A LOT faster once the beans are ground.
In conclusion, Oxidation is bad, Hydrophilicity is annoying, and both these processes happen very quickly once coffee has been ground.
Hence it is safe to say that once coffee is ground, it is extremely important to dose, tamp, and extract as quickly as possible, therefore reducing the negative effects that our forever changing atmosphere has on our rich, full-bodied, coffee.
