The oxidation process in coffee can mark your coffee as stale. When coffee is roasted, the surrounding conditions will affect its quality. Starting from the influence of temperature, humidity and improper storage.

However, the main contributing factor to the change in coffee flavor (stale) is due to oxidation of the coffee. Stale coffee changes its flavor. This is why roasters wrap coffee beans tightly to prevent them from coming into direct contact with oxygen in the air.

Some roasting experts say that just a few minutes after the grinding process, there is a change in the flavor of the coffee. This change in flavor is why specialty coffee shops grind and brew their coffee in small batches. Let’s find out more information about this oxidation process below.

What is Oxidation in Coffee?

The oxidation process itself is the reaction of chemical compounds when exposed to oxygen. This reaction causes the molecule to release electrons. Finally, there is a change in taste from the reaction.

When coffee beans come into contact with air, their flavor and aroma begin to degrade as the solutes are oxidized. Think of it like iron that rusts over time due to air. Or, like an apple slice that turns brownish after being left for a while. Not only the color, the taste of the apple also changes in contrast to when it was fresh.

This oxidation can generally occur in organic materials such as coffee. The longer the coffee is exposed to light and air, the more the quality deteriorates. Even so, it usually won’t change in appearance, but the flavor and aroma will degrade over time.

When is Coffee Poor Quality?

The deterioration of coffee quality is different in each type, not only in coffee beans or coffee grounds. However, it also occurs in the brewing of coffee whether hot or cold brew.

  • Roasted coffee beans, for this type, the freshest condition is at 3-4 days after the roasting date. While the longest is at 30 days, after that the content of oil, acid, and compounds in it disappears so that it decreases until the loss of taste.
  • Ground coffee, the grinding process can increase the speed of the oxidation process. Thus, it is recommended that the maximum consumption is only 2 weeks after grinding and a maximum of 30 days after roasting. Beyond that, coffee may be considered spoiled due to possible changes in flavor.

In addition to the two types above, brewed coffee can also undergo an oxidation process that affects its lack of flavor and aroma. Manual brew coffee can last a few days in the fridge, although the flavor is different from the first day of brewing.

Meanwhile, the shelf life of Cold Brew Coffee is a maximum of 1 month. However, it is best enjoyed after a maximum of 10 days. The flavor and aroma decreases throughout the day after extraction for 7-12 hours.

The best quality coffee beans can be enjoyed before exposure to air. In brief, the following conclusions can be drawn on the stale life of coffee.

  • Roasted coffee beans: 30 days
  • Ground coffee: 2 weeks or 14 days
  • Hot brew coffee: same day
  • Cold brew coffee: 30 days after extraction
  • Packaged coffee: packaging with normal air (oxygen) usually has a shelf life of 1-3 months. However, if nitrogen or inert gas is used, the shelf life can be up to 6-8 months. Meanwhile, the secondary shelf life (shelf life after the packaging is opened), is a maximum of only 20 days (for dry coffee), if it is moist, it is only 13 days at most.

How to Keep Coffee Fresh?

Proper storage can extend its quality life. As much as possible, keep away from factors that reduce coffee quality such as air, heat, humidity, and light. So it is recommended to store coffee in a cool, dark and dry place. This is the way to keep the freshness of coffee protected.

Store in an Airtight Jar

An airtight jar is an ideal place to store coffee while keeping it fresh. These containers can push out trapped air, creating a vacuum inside. It is recommended to buy a dark-colored jar to block light from interacting with the coffee.

Keeping Coffee in its Original Packaging

Re-wrapping coffee in its packaging can be a solution to keep it fresh. Some coffee packaging has a packaging hook clip that can block air from entering, thus slowing down the oxidation process.

Storing in the Fridge

Not many people think of keeping coffee fresh in the refrigerator. Actually, storing coffee in cold temperatures can cause damage. This is because its dry and porous form can absorb moisture and odors from the refrigerator. The solution is to store it in an airtight container or double bag to keep it moist.

Difference between Oxidation and Degassing

Oxidation is caused by direct contact between coffee and air and oxygen. Meanwhile, degassing is the process of releasing the gas inside the coffee beans.

When roasting beans, gas is formed in the beans. Typically, this process produces carbon dioxide orCO2 gas, which reduces the flavor when the beans are finished roasting.

Roasted coffee beans take some time to release this gas content. Roasters generally recommend not brewing coffee after roasting because it is less delicious.

This off-gassing process occurs up to 14 to 30 days after roasting. Starting when 24 hours after roasting, the off-gassing occurs at about 40% share. However, this depends on the variety of coffee beans and the thickness of the beans.

According to roasting experts, darker roasts degassing faster than lighter roasts. Slow roasting can speed up the degassing process and vice versa.

In addition to the roasting process, the degree of fine and coarse grinding can also affect degassing. The finer the particles of the coffee grind, the higher the release of carbon dioxide gas.

How to Tell if Coffee Has Oxidized?

It’s hard to realize coffee has oxidized just by looking at it. You have to try it, does the coffee taste bad anymore?

Keep the coffee from getting damp as it can grow mold. So, to keep your coffee fresh, make sure to store it in an airtight jar. Cut out the roast date and other label information and stick it on the jar with the coffee beans.

The best indicator that coffee has gone bad is usually that the aromatics start to disappear. If you can’t smell the aroma of the coffee or it starts to smell bad, then the coffee has gone bad. The aromatics of coffee are the first part to disappear when it undergoes oxidation.

The best advice when buying coffee is to stock up for 2-3 weeks only. Do not buy too much so that the freshness can be maintained and avoid the oxidation process. (*)

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