How to Tell if Coffee Beans Are Fresh? What's the Relationship Between Coffee Bean "Oily" Appearance and Freshness?

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Many coffee enthusiasts place great importance on coffee freshness, which refers to the freshness of coffee beans after roasting. It's generally believed that the longer the time, the lower the freshness, resulting in diminished coffee flavors or the emergence of negative flavors. For coffee lovers who are just starting out, learning to avoid buying stale coffee beans is very important. FrontStreet Coffee will teach everyone how to identify the freshness of coffee.

What is Coffee's Flavor Window?

Generally, coffee's optimal flavor window appears after the roasting is completed, experiencing a 3-7 day bean resting period before reaching its flavor peak. Afterward, flavors will gradually diminish over time, eventually leaving only woody notes. The first flavor compounds to dissipate are mainly volatile compounds like floral and fruit aromas, while water-soluble compounds like sugars, nuts, and chocolate are relatively less volatile.

Therefore, the general recommended flavor window for coffee is from the 4th to the 30th day after the roasting date. When the flavor window passes, it doesn't mean the coffee is undrinkable, just that the flavor will be somewhat inferior. This should be distinguished from the shelf life of coffee, which is generally between six months to a year for roasted beans.

How to Determine Coffee's Flavor Window

Freshly roasted coffee is in a very active state, where coffee beans slowly release gases and volatile compounds, gradually stabilizing. This is why coffee beans need about a week of resting period for their flavors to fully emerge.

When the gases are completely released, most aromatic compounds within the coffee also dissipate, leaving only woody flavors. Additionally, when the coffee particles lose their "activity" during brewing, it indicates that the flavor window for this coffee has ended. Generally, the flavor window for medium-light roast coffee is about a month after roasting, and if stored properly (cool, dark, sealed, and dry), it can be extended to about 45 days.

Ground coffee will lose its flavor faster than when stored as whole beans, so its flavor window will be relatively shorter.

Many people believe that when coffee shows oil, it means it's not fresh. This viewpoint is not entirely correct.

The "oil" evenly distributed on the surface of coffee beans is actually not "oil" in the true sense, but a water-soluble organic substance that appears oil-like. "Coffee oil" itself contains many aromatic components of coffee and can dissolve in water, which is why your brewed coffee doesn't have a greasy layer of oil floating on the surface.

Two Reasons for Oily Beans:

1. Stale Light Roast Beans

Light roast beans, which have lighter roasting degrees and appear in light brown tones, have dry surfaces after roasting and do not show oil. About five days after roasting (this may shorten to one or two days during hot summer), they begin to show "spotting oil" phenomenon (oil droplets appear on certain sides of the coffee beans). Please note: a small amount of "spotting oil" does not indicate staleness; sometimes it actually represents the peak flavor state of light roast coffee beans. If they continue to be stored, after more than two weeks from roasting, the surface of light roast beans will gradually develop a uniform, thin, bright oily sheen. The aroma will not be sweet but rather have a rancid smell. At this point, the flavor of "light roast beans" has declined, and you should avoid purchasing them.

2. Fresh Dark Roast Beans

Dark roast beans, which have deeper roasting degrees and appear in deep brown tones, show a slight oily sheen immediately after roasting, and their surfaces begin to show significant "oiling" from the first to the second day after roasting. The shiny appearance of "dark roast beans" does not indicate staleness at all. On the contrary, after three weeks from roasting, the oily sheen on dark roast beans will gradually dry out, eventually becoming dried, flavorless beans. Therefore, if you see coffee beans that are dry and not oily but appear in deep brown color, please pay special attention to whether they are marked with a roasting date, as they are very likely already spoiled, flavorless beans.

Even if they are no longer fresh, the surface-oily "light roast beans" will gradually dry out after long-term storage (such as three months), eventually returning to a dry, non-oily appearance. This shows that whether the surface is oily or not is just a reference for judging coffee bean freshness, not an absolute indicator.

How to Brew Coffee Past Its Flavor Window

First, when we say the flavor window has passed, we mean that most aromatic compounds have dissipated, and the gases inside the coffee beans have been mostly released, not that there are no flavors left and only sawdust-like taste remains.

In this state, adjusting the parameters can still "save" these coffee beans. Below, I'll share one method:

The star of this demonstration is Colombia San Jose Finca Castillo, which FrontStreet Coffee intentionally preserved for this demonstration. The specific information is as follows:

Region: Caldas, Colombia

Finca: San Jose Finca

Variety: Castillo

Processing: Fine Washed & Rum Barrel Fermented

Roast Level: Medium-Light Roast

Flavor Notes: Rum, liquor-filled chocolate, tropical fruits

Storage: 70 days, sealed, cool, dark, and dry storage

1. Parameter Recommendations:

This time, we'll still use 15 grams of coffee powder with a coffee-to-water ratio of 1:15, water temperature of 91°C, and a grind size slightly coarser than normal (to prevent too many fine particles from blocking the drainage, with a 75% pass rate through a #20 standard sieve).

2. Start with the first water pour for blooming:

Pour 25 grams of water and bloom for 18 seconds. You can see that after water contacts the coffee powder, it doesn't form a "hamburger shape," and water easily penetrates into the coffee particles. This is because the coffee beans have almost completely released their gases during storage, so they don't require excessive blooming time for degassing.

3. Second water pour:

Start from the center and pour in small circles to push up the powder bed, allowing fine particles to adhere to the filter cup wall, preventing them from settling at the bottom and blocking the drainage. You can see tiny foam being washed out. Pour this section until reaching 150 grams.

4. Final water pour:

When the water level drops to 1/2, pour the final section. Use medium water flow to quickly circle and create a vortex to "activate" the powder bed, forcing out flavor compounds. Pour until reaching 225 grams, then stop pouring. Remove the filter cup after the coffee liquid flows into the lower pot. The total extraction time is 1 minute and 44 seconds.

After brewing, you can feel a slight rum aroma. Although it lacks some tropical fruit aroma and acidity, it brings a very rich rum fermentation sensation. The liquor-filled chocolate flavor at entry is still intense, and the sweetness in the finish is also pleasing.

Of course, coffee should still be enjoyed while fresh, but if you happen to have beans that aren't very fresh, you can also use this method to brew them.

For more specialty coffee beans, please add the private WeChat FrontStreet Coffee (FrontStreet Coffee), WeChat ID: kaixinguoguo0925

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