How is the freshness of coffee measured?
When we buy a food product, in general, we prefer to buy it as fresh as possible, unless this product requires some kind of aging/refinement/maturation.
For many foods, freshness is a must to fully enjoy their organoleptic properties, but for others, immediate consumption could represent a limit to the maximum organoleptic expression, as in the case of aged wines or cheeses and, if we want, partly roasted coffee.
Premise:
Two years ago I had the pleasure of meeting in Zurich Samo Smrke, Chahan Yeretzian, and Marco Wellinger from the Zurich University of Applied Sciences Institute of Chemistry & Biotechnology in Switzerland. I have known them for a few years and we have had several opportunities to exchange opinions and views (I was obviously the one listening to them).
They conducted a 2-year research on The Coffee Freshness published by SCA. (here an excerpt)
Let's begin…
Freshness, in fact, allows the potential of the food to be expressed, but the term freshness takes on different meanings whether we are talking about mozzarella, meat, oil, wine, or coffee (I could continue with an endless list).
In the coffee world, there are different schools of thought, almost all right or wrong depending on the perspective.
The phases of freshness:
What all these different schools of thought have in common is that roasted coffee has 4 phases:
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Maturation (of the aromatic part)
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Degassing (usually begins with Maturation) (inevitable loss of the barrier effect)
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Oxidation (attack by oxygen)
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Rancidity (mutation into an unpleasant sensory experience)
As already mentioned, phases 1 and 2 start at the same time (perhaps Degassing starts a little earlier since, already during roasting, the Gas is created and begins to "push to escape from the bean").
Why is Degassing (the Gas) so important?
It is the unit of measurement for coffee freshness, like a meter, it measures how much time has passed since that coffee was roasted, this is roughly speaking, approximately.
We said that the roasting process creates important chemical changes (in addition to the physical ones that are evident like changes in color, size, and weight) when the Maillard reaction occurs (as I have already explained here), among these are the Strecker degradations.
These very degradations create gases, mostly Carbon Dioxide. Carbon Dioxide can be measured to determine the freshness (or lack thereof) of that coffee, knowing how much was initially present, considering that it is trapped between the cells of the roasted coffee and escapes over a few weeks (degassing).
Therefore: less CO2, less freshness.
What is CO2?
CO2 is the substance that allows espresso to form crema on the surface (if there’s no CO2, there’s no emulsion), or the blooming during pre-infusion in filter coffee.
The loss of Carbon Dioxide depends on several factors that influence its rate:
Packaging (material and quality, but also atmospheric conditions, internal and external)
Roasting (fast or slow, light or dark... and all the nuances in between)
Type of coffee (its chemical composition)
Time (obviously)
So, to not go beyond, how do I properly store my coffee?
One answer above all others is to buy a freshly roasted product and let it mature for the necessary time (usually at least 3-4 days for Filter roasting, at least 7 days for roasts suitable for espresso), but remember it depends on many variables as we have just seen.
Conclusion:
Make sure not to buy (and especially not to open!) packages you won’t finish within about ten days or at most a few weeks. Help keep coffee fresh by avoiding risky behaviors (heat, air, humidity).
But remember: Our coffees are vacuum-packed and then sealed in a protective atmosphere to minimize oxygen contamination inside the closed package, in the coffee shop you can find our current offerings.
To enjoy coffee at its freshest, order our specialty coffees roasted to order: shipped within 24 working hours from roasting. Also discover our coffee storage containers to preserve its aroma longer.
