Grind coarser in autumn? Anti-bitterness settings

Why does the grinding have to change according to the seasons?

Preparing the perfect coffee is a subtle alchemy where every detail counts. Among these details, the grind size plays a fundamental role. However, what many people don't know 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 coffee extraction. The bean reacts to its environment, absorbing more or less moisture, which changes its density and extraction behavior.

Adjusting the grind is therefore not a whim, but a logical response to environmental changes.

Understanding the link between grinding and bitterness

Bitterness in coffee comes mainly from over-extraction : the water remains in contact with the grounds for too long, dissolving the driest and most aggressive compounds. Conversely, too coarse a grind can lead to under-extraction , resulting in acidic or watery coffee.

In the fall, temperature and humidity fluctuations change the flow rate of water through ground coffee. If these parameters are not corrected, the cup can turn bitter without warning.

Autumn: a fragile balance to be found

As 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 promotes a slightly finer grind than usual. But if left unchecked, there's a risk of over-tamping the coffee and slowing down extraction.

This is where grinding a little coarser in the fall can be key: it frees up the water, speeds up the passage, and prevents bitter over-extraction.

Signs Your Coffee Is Too Bitter

How do you know if your settings aren't appropriate for the season? Here are some clues:

A feeling of dryness on the palate.
A bitterness that persists for several seconds after the sip.
A dark, almost opaque cup, without aromatic complexity.
Notes of charcoal, rubber or medicine.

If you notice these defects, it is time to review the grind before blaming the coffee itself.

Adjusting 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 one notch to a coarser grind.
Test the extraction using your usual method (espresso, filter, plunger, etc.).
Taste, comparing fluidity, acidity and bitterness.

The idea isn't to completely transform the grind, but to adjust it in small steps. Generally, one or two notches are enough in the fall to restore balance.

Special case: espresso in autumn

Espresso is the method most sensitive to variations in grind. A few microns are enough to disrupt the flow. In the fall, if your shot lengthens 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 cream.
A milder cup, with chocolate notes brought to the fore.

Filter and Chemex: Beware of under-extraction

Conversely, with gentle methods like the V60 or Chemex, the danger in the fall is under-extraction. Dry air can accelerate the flow of water, resulting in a cup that's too thin, acidic, and lacking in body. Here, grinding coarser isn't always necessary; sometimes, on the contrary, you need to slow down a little.

The trick is to play with 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 bean storage. Coffee absorbs ambient moisture like a sponge. If it's stored in a cupboard near a heater or in a humid kitchen, its density changes. This disrupts the consistency of the grind.

To limit this problem:

Store your grains in an airtight, opaque container in a cool place.
Avoid sudden temperature changes.
Always grind to order, just before brewing.

This way, your grinder settings will remain stable longer.

Barista tip: taste with tap water AND filtered water

In autumn, water distribution networks also experience fluctuations (construction, rain, 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 sacrifice the aromas.

Coffee capsules or beans: should you also adapt?

Even with capsules, seasonal bitterness can be noticeable. Automatic machines are calibrated for consistent results, but if the local water level changes or the capsule has absorbed moisture, the cup may seem more bitter in the fall. In this case, rinsing the machine, using filtered water, and preheating the cup can reduce the problem, even if you can't adjust the grind.

With a built-in grinder (automatic grain machines), remember to adjust the setting at least twice a year: in summer and autumn.

When to keep a fine grind despite autumn?

Grinding coarser isn't an absolute rule. Some coffees tolerate a fine grind very well, even in the fall. This is the case for very fruity or floral coffees (Ethiopia, Kenya), where a slightly longer extraction can enhance the complex notes.

So the secret is 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, there's nothing like a comparative tasting. Prepare two identical coffees, with only the grind changing: 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 depending on the season.

In summary: autumn, a season to rediscover your coffee

Grinding coarser in the fall isn't just a technical adjustment; it's an opportunity. It's the perfect time to explore new flavors, tame bitterness, and enjoy rounder, more balanced coffees. Every season is an invitation to rediscover your beans, and fall, with its contrasting temperatures and humidity, encourages you to be attentive, curious, and attentive to your cup.

A well-adjusted coffee in autumn promises warmth and sweetness in every sip.

You may also like to read: Preserve your coffee longer without losing the aroma.