Why Do Coffee Bean Bags Expand? How to Store Packaged Coffee Beans & Recommendations

Will Bagged Coffee Beans Swell After Sitting for a Few Days?

Friends who enjoy red wine know that good red wine needs to be opened an hour in advance to allow oxidation, which helps release aromas. Although the principle differs, coffee indeed has a similar practice, which we call degassing.

The Art of Bean Resting

Speaking of bean resting, coffee beans have what's called a degassing phenomenon after roasting. This means coffee beans expand in volume during roasting, and the expanded space within the beans traps carbon dioxide. Over time, this carbon dioxide gradually escapes from the coffee beans. This is precisely why coffee beans need to be packaged in bags with one-way degassing valves—because coffee beans release gas, and if sealed in an airtight bag, you'd see the bagged coffee beans puff up, potentially even bursting. The one-way degassing valve allows gas to escape while preventing moisture and oxygen from entering.

Some people say that seeing rich foam appear when brewing coffee indicates good coffee, or more specifically, fresh coffee. This is largely correct—coffee is at its most vigorous degassing stage immediately after roasting. If coffee gets damp or comes into contact with oxygen, it accelerates the aging process and the flavor deteriorates. This indeed serves as an indicator for judging coffee quality.

However, when coffee grounds are steeped in water, if left untouched, as the grounds absorb water and release foam, this actually impedes contact between the coffee grounds and water; it can even affect the rate at which coffee extracts into the water. At this point in the coffee brewing process, stirring becomes necessary to accelerate the water absorption and extraction rate. There are various schools of thought and methods regarding this practice.

Even more challenging is brewing espresso—coffee beans that are too vigorously degassing become much harder to control. The compacted puck will expand, and when high-pressure hot water passes through the grounds layer, it becomes very unstable due to degassing. The only solution is bean resting and awakening.

There are many opinions on specific bean resting methods. For example, placing coffee beans in a sealed foil bag with a one-way degassing valve and storing them in a temperature-controlled space for 8 to 24 hours. After opening, they should sit for 30 minutes to several hours to "awaken" through contact with air, aiming for good flavor and moderate degassing. In reality, different coffee varieties and roasting methods require different resting and degassing times, which we need to discover gradually through careful experience.

Recommended Bagged Coffee Bean Brands

FrontStreet Coffee's freshly roasted single-origin bagged coffee beans offer excellent guarantees in both brand and quality, suitable for brewing with various equipment. More importantly, they offer exceptional value—at around 80-90 yuan for a half-pound (227g) bag. Calculating based on 200ml per cup with a 1:15 coffee-to-water ratio, one bag can produce 15 cups of specialty coffee, with each cup costing only about 5-6 yuan. Compared to coffee shops selling single cups for dozens of yuan, this represents extraordinary value.

FrontStreet Coffee: A roastery in Guangzhou with a small storefront but diverse bean varieties, offering both famous and lesser-known beans, plus online services. https://shop104210103.taobao.com

Important Notice :

前街咖啡 FrontStreet Coffee has moved to new addredd:

FrontStreet Coffee Address: 315,Donghua East Road,GuangZhou

Tel:020 38364473