Why should the grind change with the seasons?
Preparing the perfect coffee is a subtle alchemy where every detail counts. Among these details, the grind size plays a fundamental role. Yet, what many ignore is that the optimal setting varies with the seasons. In autumn, the air becomes cooler, drier, or sometimes more humid depending on the region, and this directly influences the coffee extraction. The bean reacts to its environment, absorbing more or less moisture, which changes its density and behavior during extraction.
Adjusting the grind is not a whim, but a logical response to environmental changes.
Understanding the link between grind and bitterness
L’bitterness in coffee comes mainly from a over-extraction : l’water stays too long in contact with the grind, dissolving the driest and most aggressive compounds. À l’inverse, a grind too coarse can lead to a under-extraction, giving a coffee acidic or watery.
In autumn, variations in temperature and humidity change the flow rate of water through the ground coffee. If these parameters are not corrected, the cup can turn bitter without warning.
Autumn: a fragile balance to find
When the days get shorter, the air is often drier indoors due to heating, while it can be humid outside on cool mornings. This duality disrupts coffee beans. They can lose some moisture, becoming more brittle, which favors a slightly finer grind than usual. But if left uncorrected, the risk is over-tamping the coffee and slowing down extraction.
That's where grinding a bit coarser in autumn can be the key: it frees up the water, speeds up the flow, and avoids bitter over-extraction.
Signs that your coffee is too bitter
How to know if your settings are not adapted to the season? Here are a few clues:
- A sensation of dryness in the palate.
- A bitterness that persists several seconds after the sip.
- A dark, almost opaque cup, without aromatic complexity.
- Notes of coal, rubber or medicine.
If you observe these defects, it's time to review the grind before accusing the coffee itself.
Adjust the grind: the step-by-step method
To correct bitterness, start by slightly widening your grind:
- Note your current setting (on manual or electric grinder).
- Increase by one notch towards a coarser grind.
- Test the extraction on your usual method (espresso, filter, piston...).
- Taste by comparing the fluidity, acidity and bitterness.
The idea is not to completely transform the grind, but to adapt it with small touches. In general, one or two notches are enough in autumn to regain balance.
Special case: espresso in autumn
Espresso is the method most sensitive to grind variations. A few microns are enough to disrupt the flow. In autumn, if your shot flows too slowly and releases a dark crema, it's probably because the grind has become too fine for the current conditions.
Grinding slightly coarser then allows you to obtain:
- A more regular flow.
- A more golden crema.
- A sweeter cup, with chocolate notes brought to the fore.
Filter and Chemex: beware of under-extraction
Conversely, in gentle methods like V60 or Chemex, the danger in autumn is under-extraction. Dry air can accelerate the flow of water, resulting in a cup that is too light, acidic, and lacking body. Here, grinding coarser should not be systematic: sometimes, it is necessary to slow down a bit instead.
The tip is to play on two levers: the grind and the water temperature. If you grind coarser but the flow is too fast, increase the temperature slightly (93–94 °C) to compensate.
The role of coffee storage
Another crucial factor in autumn is grain storage. Coffee absorbs ambient humidity like a sponge. If stored in a cupboard near the heating or in a humid kitchen, its density changes. This disrupts the consistency of the grind.
To limit this problem:
- Store your beans in an airtight, opaque container placed in a temperate area.
- Avoid sudden temperature variations.
- Grind always on demand, just before brewing.
Thus, your grinder settings will remain stable for longer.
Barista tip: taste with tap water AND filtered water
In autumn, water distribution networks also experience variations (works, rains, dead leaves in the basins). Testing your coffee with filtered water can reveal whether the bitterness comes from the coffee or the water used. If the bitterness disappears with softer water, there's no need to grind coarser: change the water rather than sacrificing the flavors.
Coffee in capsules or beans: should it also be adjusted?
Even with capsules, seasonal bitterness can be felt. Automatic machines are calibrated for a consistent result, but if the local water changes or the capsule has absorbed moisture, the cup may seem more bitter in autumn. In this case, rinsing the machine, using filtered water, and preheating the cup can reduce the defect, even if you can't adjust the grind.
With a built-in grinder (automatic bean-to-cup machines), consider adjusting the setting at least twice a year: in summer and autumn.
When to keep a fine grind despite autumn?
Grinding coarser is not an absolute rule. Some coffees work very well with a fine grind, even in autumn. This is the case with very fruity or floral coffees (Ethiopia, Kenya), where a slightly longer extraction can enhance the complex notes.
The secret is therefore to taste, observe and decide based on your specific coffee rather than following a fixed rule.
The art of comparative tasting
To fine-tune your settings, nothing beats a comparative tasting. Prepare two identical coffees, with only the grind size changed: one slightly finer, the other coarser. Taste blind, noting the differences in acidity, bitterness and body.
This exercise teaches you to feel the subtleties and understand how your grinder influences the cup according to the season.
In summary: autumn, a season to rediscover your coffee
Grinding coarser in autumn is not just a technical adjustment, it's an opportunity. It's the ideal time to explore new flavors, tame bitterness and enjoy rounder, more balanced coffees. Each season is an invitation to rediscover your beans, and autumn, with its contrasts of temperature and humidity, encourages you to be attentive, curious and attuned to your cup.
A well-adjusted coffee in autumn is a promise of warmth and softness in every sip.
You will also like to read: Preserve your coffee longer without losing the aroma.
