What Are the Differences in Coffee Freshness? How to Determine if Coffee Beans Are Fresh?

Understanding Coffee Freshness: Beyond Roast Date and Flavor

As coffee culture gradually becomes more widespread, more and more people are beginning to realize that coffee also requires attention to "freshness." This is because fresh coffee always contains more aromatic compounds, which can bring us a richer drinking experience. However, since most aromatic compounds are volatile, they gradually dissipate over time, causing coffee freshness to decline accordingly.

Generally, our main criteria for determining whether a cup of coffee is fresh are its roast date and its flavor. Because these two are relatively direct and accurate ways to know the freshness of the coffee itself, FrontStreet Coffee has emphasized them in previous articles. Those interested can learn more by searching through previous articles. In addition to these two judgment methods, we can also observe other aspects to determine if coffee is fresh. While these methods are relatively less direct and require judgment combined with flavor, they are still valuable techniques for preliminary understanding of coffee freshness. So today, FrontStreet Coffee will share what other aspects can reveal coffee "freshness."

1. Coffee Aroma

First, we can preliminarily judge coffee freshness through aroma, because as FrontStreet Coffee mentioned, the fresher the beans, the more aromatic compounds they contain. Therefore, after coffee beans are ground into powder, we can make a simple judgment through smelling.

Fresh coffee beans will emit extremely rich aromas after being ground, from which we can capture some concrete flavor characteristics. Coffee beans that have been stored for longer periods, however, have mostly lost their aromatic compounds through dissipation, so what they emit is more of a roasted flavor, making their flavors relatively less easy to capture.

2. Foam Richness

If you can't smell the aroma due to nasal congestion or other reasons, that's okay, because coffee also shows many obvious characteristics during brewing that reflect its freshness. For example, in the blooming stage of pour-over coffee, the degree of swelling in the coffee bed is a good observation point.

With normal extraction parameters, fresh coffee will swell significantly during blooming due to abundant carbon dioxide. The fresher the coffee, the more carbon dioxide it contains, and the larger the swelling. Conversely, relatively less fresh coffee beans won't swell as much because they don't have as much carbon dioxide. Besides swelling, the "water retention" of the coffee bed during blooming can also serve as an indicator of freshness. Because carbon dioxide acts as a barrier, it impedes the penetration of hot water. When coffee contains more carbon dioxide, there's more resistance, and water flows through more slowly. At this point, we can observe the moisture level of the coffee bed—whether it remains moist after blooming ends or has already dried out by the 20-second mark. This is another small characteristic for judging coffee bean freshness.

However, it's important to note that these two characteristics (swelling degree and water retention) can only indicate a general range of how long it has been since roasting. They cannot serve as a basis for judging whether coffee tastes good. This is because most light-roast coffees still taste delicious even after being stored for a considerable period of time, which is related to their density. Therefore, we can only use these two characteristics to judge how long it has been since coffee beans were roasted, with final determination still requiring flavor assessment.

Now let's talk about espresso, since many friends consume espresso as their daily coffee. Similarly, espresso can also be judged for freshness through aroma and the state of the coffee during extraction. For espresso, the main indicator of coffee bean freshness during preparation is its crema—the richness and fineness of which are both observable characteristics.

Because the main components of espresso crema are carbon dioxide and lipids from coffee beans, when coffee beans are fresher, they contain more carbon dioxide, and the crema produced during extraction will be richer but simultaneously coarser. This is mainly because espresso crema is essentially countless tiny bubbles filled with carbon dioxide. When more bubbles are generated, they break more easily because their structure is less stable, resulting in relatively poorer quality that breaks more easily.

When coffee beans have been stored for a period of time (starting from the 7th day after roasting), the amount of carbon dioxide decreases. At this point, although the extracted crema may not be as rich as before, its fineness is much higher. This is because the bubble structure is more stable and less likely to break. As coffee beans continue to age and their carbon dioxide content decreases further, the extracted coffee crema will become progressively thinner. Therefore, we can understand that both the richness and fineness of crema can serve as standards for measuring coffee bean freshness. However, similarly, they cannot serve as standards for judging whether coffee tastes good. Additionally, we need to note that there will be significant differences in crema thickness between dark-roast and light-roast coffee beans during extraction, because their capacity to contain carbon dioxide is completely different. Therefore, do not apply the standards of dark-roast espresso to light-roast espresso extraction, as this will lead to misunderstandings.

Important Notice :

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