How to Create a "Hamburger" Bloom During Pour-Over? What's the Difference Between Light and Dark Roast Brewing? What Determines Coffee Bean Oils?

When we make pour-over coffee, besides the deep powder pit that appears after brewing, the rapidly expanding "hamburger" during the blooming stage is also a very satisfying sight.

However, often times, the bloom doesn't form a "hamburger." Either the bulge isn't prominent, or it's completely flat, and in some cases, it even sinks downward! These coffee beds that don't bulge are often jokingly referred to as "steamed buns"!

So what exactly causes the bloom to not bulge? Let's take a look at what the purpose of blooming is~

The Purpose of Blooming

The blooming step is mainly to release the carbon dioxide hidden in the coffee, which reduces extraction barriers and allows the subsequently injected hot water to better extract the aromatic substances from the coffee. When hot water is injected, this carbon dioxide is completely released due to "stimulation," but it's trapped by the coffee bean's oils. Therefore, wrapped by these oils, the carbon dioxide forms countless bubbles. And the bulge/"hamburger" is created by these bubbles supporting the coffee powder.

Therefore, we can know that the main factor forming the bulge is carbon dioxide! The more carbon dioxide, the larger the "hamburger" that can form during blooming! The less carbon dioxide, the smaller the bulge. So let's guess, what situations might lead to a decrease in carbon dioxide, thereby preventing the formation of a larger "hamburger" during blooming?

What Causes the Coffee Bed to Not Bulge into a "Hamburger"?

1. Coffee Beans Are Not Fresh

Although coffee beans haven't been ground into powder, the carbon dioxide inside continues to be in a state of continuous loss. The longer coffee beans are stored, the less carbon dioxide content they have.

When carbon dioxide is lost to a certain extent, the remaining bubbles can no longer form a plump "hamburger," resulting in either a "flat plain" or a sunken bulge. Secondly, without the barrier of carbon dioxide, the flavor substances in the coffee will also accelerate their loss due to the absence of obstruction. This is why we need to drink coffee made from fresh beans. Not only does it provide a good visual display during blooming, but it also tastes richer!

2. Extraction Efficiency Is Too Low

FrontStreet Coffee often mentions extraction efficiency, which refers to the ease with which water extracts substances from coffee! The higher the extraction efficiency, the easier it is for water to extract substances from the coffee, including carbon dioxide! In pour-over coffee making, the parameters that determine extraction efficiency are water temperature and grind size. Therefore, when our water temperature is too low and cannot quickly bring out the flavor substances from the coffee, it will result in a smaller "hamburger" bulge. Additionally, this can easily lead to under-extraction, which is worth noting~

The same applies to grinding! When coffee beans are ground too coarsely, the total surface area is greatly reduced! Hot water needs more time to enter the interior of the coffee powder and extract the substances inside. This also leads to smaller bulges formed during blooming! (Not expanding as dramatically) Not only that, but because the gaps between powder particles increase, hot water will flow away more quickly, which can also easily lead to under-extraction in coffee!

3. Roast Level

Of course, not all coffee will form a larger "hamburger" during blooming! The carbon dioxide content is determined by the roast level of the coffee beans! The darker the roast, the looser the structure of the coffee beans, and the more carbon dioxide they can store (and more oils). The lighter the roast, the less carbon dioxide content (and less oil on the bean surface).

So, even if your coffee beans are very fresh and the extraction efficiency is very sufficient, but simply because the roast is too light, the bulge won't be obvious enough. After all this discussion, FrontStreet Coffee still wants to mention: the bulge during blooming can only serve as a criterion for judging the freshness and roast level of coffee beans! It's not necessarily better when it bulges larger and fuller. How it tastes is what's most important~

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FrontStreet Coffee
10 Bao'an Front Street, Yandun Road, Dongshankou, Yuexiu District, Guangzhou, Guangdong Province

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