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How to Determine if Coffee Beans Are Fresh | Do Fresh Coffee Beans Exude Oil | How to Store Fresh Coffee Beans

Published: 2026-01-27 Author: FrontStreet Coffee

Last Updated: 2026/01/27, Professional coffee knowledge exchange For more coffee bean information please follow Coffee Workshop (WeChat official account cafe_style) Recently due to participating in some coffee events I bought several varieties of beans and they piled up at home resulting in slightly excessive inventory. Today I finally had a rare quiet day at home and decided to consume some of the stock. So I took out a bag of coffee beans that was opened a month ago only to find it exuding

For professional coffee knowledge exchange and more coffee bean information, please follow Coffee Workshop (WeChat official account: cafe_style)

Recently, I participated in some coffee events and bought several varieties of beans that have been piling up at home, resulting in a bit of excess inventory. Today, I难得 had some quiet time at home and decided to use up some of my stock. So I took out a bag of coffee beans that had been opened a month ago, only to find it... oozing oil.

Some people might ask: "The fresh coffee beans I bought are already oily? Does this really mean oiled beans can't be consumed? Then what is the 'crema' you need when extracting espresso? If I buy coffee beans, how can I tell if they're fresh? If I want to extend the shelf life of fresh coffee beans, how should I store them?"

It seems today's knowledge points are quite extensive. Let's go through them one by one.

What causes beans to "ooze oil"?

There are two types of beans that ooze oil: fresh dark-roasted beans and stale light-roasted beans.

Dark-roasted beans, deeply roasted, appear with a slight oily sheen after baking. From the first to the second day out of the oven, they begin to show significant "oily sheen." The glossy "dark-roasted beans" gradually lose their surface sheen after three weeks out of the oven, eventually becoming dry, stale beans that have lost their flavor. At this point, the dark-roasted beans conclude their glorious bean life.

Light-roasted beans, lightly roasted, appear dry after baking. About five days out of the oven, they begin to show "spot-like oiliness." Note that this doesn't necessarily indicate they're stale; in fact, it might be the peak of their bean life. After two weeks, light-roasted beans begin to show an even oily sheen on the surface and smell rancid. It's recommended not to drink these coffee beans anymore, though you could grind them into powder and use them as an exfoliant during bathing.

What exactly is "crema"?

The golden to chocolate-colored liquid that extracts on top of espresso is called crema. It's the emulsification of naturally existing fats and oils in coffee when soluble substances are extracted through high-temperature, high-pressure water, mixed with air to create fine, dense bubbles.

Because freshly roasted coffee releases a certain amount of carbon dioxide, and carbon dioxide also participates in the emulsification process, the fresher the coffee, the more carbon dioxide is released, and larger bubbles can be seen during extraction.

Factors affecting crema include: the roast degree of coffee beans (light-roasted beans have lighter and thinner crema), freshness, processing method of raw beans (sun-dried or honey-processed beans typically have richer crema than washed beans), origin, and extraction equipment.

How to choose coffee beans

"Observation, smelling, questioning, and palpation" are methods used in traditional Chinese medicine diagnosis, and buying coffee beans is somewhat similar to this process.

When selecting coffee beans, observe their appearance. There should be relatively few defective beans. Check if single-origin beans have consistent color, and if the particle size and shape are similar (it's normal for blended beans to vary in size and color). Check if light-roasted beans are oily. Take one or two beans and taste them - if they're crispy, it indicates the beans haven't been exposed to moisture. If they leave a fragrant aftertaste, it indicates the beans are fresh.

If the coffee beans have lost their aroma or even developed stale or rancid smells, they are no longer fresh.

However, there's one type of coffee bean you should absolutely avoid drinking: those with yellowed surfaces. When coffee beans become moldy internally and breed bacteria, chemical changes also occur on the surface, turning the outer shell yellow.

How to store coffee beans?

Some people ask: "Can coffee beans be refrigerated?"

Please look at my horrified expression!

The drastic temperature difference between inside and outside the refrigerator will cause moisture to condense in the coffee storage bag, and the coffee beans will quickly become damp.

"What about freezing?"

That's truly an excellent question!

In 2016, a research team from the University of Bath in the UK, collaborating with local coffee shops, discovered that freezing coffee beans before grinding can result in more uniform coffee powder size and tighter particle arrangement, thereby allowing for more complete coffee extraction and making the coffee more delicious.

The research team found that the lower the external temperature, the tighter and more orderly the arrangement of coffee powder particles. The uniformity of coffee grinding is very important for coffee extraction - the more uniform the grinding, the more complete the extraction.

It's reported that this research has been published in Scientific Reports, and Nature magazine also featured it in a special report.

Wow, as a female PhD in pharmacology, seeing this truly makes me envious. In 2016, Scientific Reports had an impact factor of 5.228 and became highly sought after by Chinese researchers, claiming that everyone doing research must have at least one publication.

Coffee beans should be stored away from light as much as possible, because direct light exposure is extremely damaging to coffee beans, and even non-direct lighting will accelerate the decline of coffee flavor. Therefore, coffee beans should be stored in a dry room temperature environment, away from light and sealed.

Fresh coffee bean brand recommendations

FrontStreet Coffee's freshly roasted single-origin and espresso fresh coffee beans: Yirgacheffe coffee, Brazilian coffee, Mandheling coffee, and others all have sufficient guarantees in terms of brand and quality, suitable for brewing with various equipment. More importantly, they offer extremely high value - a half-pound (227 grams) package costs only around 80-90 yuan. Calculating based on 15 grams of powder per pour-over coffee, one package can make 15 cups of coffee, with each cup of single-origin coffee costing only about 6 yuan. Compared to the normal café price of 30-40 yuan per cup, this represents exceptional value.

FrontStreet Coffee: A roastery in Guangzhou with a small shop but diverse bean varieties, where you can find various famous and lesser-known beans. They also provide online shop services. https://shop104210103.taobao.com