On a chilly day, a warm cup of coffee offers an enticing aroma that invigorates the spirit. Coffee consumption offers numerous benefits—such as boosting metabolism, alleviating fatigue, and promoting relaxation—which is why many people make a habit of enjoying a cup in the morning or afternoon. However, if the quality of the coffee beans is poor, the resulting aroma and health benefits will be diminished.
Next time you buy coffee beans, remember to pay attention to details like packaging and roast dates so you can enjoy a truly high-quality cup of coffee!
Aging Coffee Beans?
Freshly roasted coffee contains carbon dioxide amounting to approximately 2% of its total weight. Internal pressure causes this gas to slowly desorb (release) over the weeks following the roast.
For about 12 hours after roasting, the internal pressure is sufficient to prevent significant amounts of oxygen from penetrating the bean’s structure. Beyond this point, oxidation causes the beans to age, leading to a decline in flavor.
Factors such as gas composition, internal pressure, and the rate of gas release are all influenced by the roasting method. Roasting at higher temperatures or to a darker roast level results in higher gas content and greater internal pressure; the cellular structure expands more significantly, creating larger pores.
These factors accelerate gas desorption and the aging process after roasting. While I do not advocate altering one’s roasting style solely to extend shelf life, it is important to understand that darker-roasted beans lose gas and age more rapidly than light-roasted ones.
Roast development also affects gas release in roasted beans. If development is incomplete, parts of the bean’s fibrous structure remain tough and non-porous, trapping gas within the internal cavities. If packaged roasted beans show no signs of gas release, it may indicate incomplete roast development.
Methods of Storing Roasted Beans: Pros and Cons
- Non-sealed packaging.
- Bags with degassing valves.
- Vacuum-sealed bags with degassing valves.
- Nitrogen-flushed bags with degassing valves.
- Vacuum-compressed bags.
- Nitrogen-flushed pressurized packaging.
- Frozen packaging. Non-sealed packaging
When roasted coffee beans are stored in non-sealed packaging or other air-filled containers (such as lidded buckets), they age rapidly. Ideally, beans stored this way should be consumed within 2 to 3 days of roasting.
Valve bags
One-way valve bags are the industry standard for specialty coffee. This type of packaging allows gases to escape from the bag while preventing fresh air from entering. Beans stored in these bags can remain fresh for several weeks. After a few weeks, the most noticeable changes in valve-bagged beans are the loss of carbon dioxide and aroma. The loss of carbon dioxide is particularly evident during espresso extraction, as the resulting coffee produces significantly less crema*.
*Translator’s note: Crema is the thick layer of foam that floats on the surface of an espresso shot.
Vacuum-sealed valve bags
Vacuum sealing significantly reduces the oxidation of roasted beans within the valve bag, delaying flavor degradation.
Nitrogen-flushed valve bags
Flushing the valve bag with nitrogen reduces the potential for oxidation to near-zero levels. Although valve bags limit oxidation, the loss of internal gases and pressure still has a minor impact.
If a nitrogen-flushed valve bag containing roasted beans is opened days or weeks after roasting, the beans will age much faster than freshly roasted ones because they lack the internal pressure that previously inhibited oxygen ingress. For instance, coffee stored in a valve bag for a week might still taste fresh, but if the seal is left open for a full day, the degree of aging will match that of beans stored in non-sealed packaging for the entire week.
Vacuum-compressed bags
Today, few roasters still use vacuum-compressed bags. While this packaging reduces oxidation, gases released by the beans cause the bag to expand, making storage and handling inconvenient.
Nitrogen-pressurized packaging
This is the most effective packaging method. Nitrogen flushing prevents oxidation, while pressurizing the package (usually a canister) prevents the escape of gases from within the beans. Additionally, storing packaged coffee beans in a low-temperature environment (the lower, the better) can delay the aging process; when stored this way, beans can remain fresh for months after roasting.
Freezer Storage
Although some remain skeptical about this method, freezing is indeed highly effective for long-term storage. It reduces the rate of oxidation by over 90% and slows down the loss of volatile compounds.
You need not worry about the moisture inside freshly roasted beans actually freezing solid; because the water is bound to the fibrous matrix of the bean, it does not reach a frozen state. The best approach is to place a single portion of beans (enough for a pot or a cup) into a vacuum-sealable bag (such as a Ziploc) and freeze it. When you are ready to use them, simply remove the package from the freezer and let it sit until it reaches room temperature before opening the bag and grinding the beans.
How do you evaluate coffee quality?
Tasting while warm
When slurping coffee, forget about polite manners. In a cupping session, a loud slurp is actually a sign of respect (at one public cupping event, my loud slurping inadvertently revealed me as a coffee professional).
Forcefully spraying the coffee into your mouth enhances retronasal olfaction—the sense of smell experienced from within the mouth—by increasing both the volume and speed of aromas reaching the nose.
Even when the coffee is in your mouth, the vast majority of what you perceive comes from the nasal cavity. The tongue can only detect five basic tastes: bitterness, acidity, sweetness, saltiness, and umami. The nose, however, can distinguish between thousands of aroma molecules, often at concentrations as low as one part per billion.
Every cup of coffee possesses a unique aromatic signature composed of hundreds of volatile aroma compounds. It is this distinct composition of volatile substances that allows a cupper to distinguish between two similar samples with just a single sniff. Ultimately, it is retronasal olfaction—not the taste sensations on the tongue—that plays the leading role in shaping our perception of flavor during cupping. Tasting as it Cools
Coffee exhibits higher perceived acidity when warm than when cool. Cupping while the coffee is warm is the ideal time to evaluate various characteristics such as acidity, brightness, sweetness, and balance.
However, acidity acts much like a thick fog, obscuring our view of many subtler qualities. Once the coffee cools and the acidity begins to subside, other characteristics—particularly green bean defects and certain effects of the roasting process—gradually become distinct.