Why Are There Coffee Grounds in My Espresso? What's Wrong with the Espresso Extraction Process?

With the recent sudden drop in temperature, customers visiting the café have been choosing hot coffee options. After tasting a hot Americano, one customer recalled noticing small particles at the bottom of their cup after drinking hot Americano before, and asked FrontStreet Coffee: "Are those coffee grounds at the bottom of the cup? Why have I never seen them when drinking iced coffee?"

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In response, FrontStreet Coffee would like to discuss today why espresso sometimes leaves sediment at the bottom of the cup, and what methods can be used to reduce this occurrence.

Is it normal to have coffee grounds at the bottom of the cup?

These black particles settling at the bottom of the cup are actually fine powders that fall into the cup along with hot water during espresso extraction. This is similar to how soy milk might have bean dregs at the bottom, or how fresh juice contains fruit pulp.

Under normal circumstances, it's normal for espresso to contain trace amounts of fine powder particles. If you're not drinking espresso straight, you might not even notice their presence. When adding a certain proportion of water or milk to make other espresso-based drinks, they become even harder to detect. Therefore, these minute amounts of fine powder don't affect the coffee's taste.

However, when you can clearly see black particles mixed in your coffee with the naked eye, it means there's an "unusual" amount of powder, which is highly likely due to a problem in some stage of the extraction process.

Where do these fine powders come from?

It's important to know that coffee beans for espresso need to be ground to a consistency similar to fine sand, with particle sizes ranging approximately from 200 to 300 micrometers. What we commonly call "fine powders" are created when coffee beans are cut and squeezed during grinding. These particles are smaller than our target particle size range and, due to static electricity, adhere to the coffee grounds. This type of fine powder cannot be completely avoided during the grinding process. (Just like when we break open a coffee bean, some powder will scatter to varying degrees.) Some commercial-grade grinders produce more uniform particle sizes, which can reduce the烦恼 caused by fine powders to some extent.

The portafilter basket used for espresso extraction consists of a mesh made up of tiny holes that act as a filter. If you hold the portafilter basket toward a light source, the light passing through the mesh indicates the hole size. When we load coffee grounds into the portafilter basket and attach the portafilter to begin extraction, those fine powder particles smaller than the holes will be washed into the coffee by the high-pressure hot water. These fine powders carried along with the coffee liquid usually don't immediately sink to the bottom of the cup; they often settle after a few minutes of sitting.

Returning to the customer's question, FrontStreet Coffee uses shorter white coffee cups for hot Americanos, so when drinking from top to bottom, you would naturally see some fine powder settled at the bottom. For iced Americanos, taller glasses are used, and straws are typically provided, allowing you to drink from bottom to top. That's why you don't notice coffee fine powder sediment at the bottom when drinking iced Americanos—it's not that there aren't any fine powders.

Of course, besides grinding, certain details overlooked before and after extraction can also lead to unusual amounts of coffee powder in your drink. For example, if the portafilter ring isn't cleaned thoroughly and still has residue from previous uses, situations like these can cause unusual coffee grounds to appear in your cup.

How to avoid this situation?

1. First, check if it's caused by technical issues. If so, you need to develop the habit of cleaning the group head and portafilter regularly, which not only prevents coffee contamination but also ensures hygiene.

2. Portafilter baskets are affected by long-term high-temperature, high-pressure extraction. With prolonged use, the holes in the portafilter basket can deform, allowing more fine powders to pass through. However, this phenomenon isn't common and typically only occurs after 1-2 years of intensive use. To check, simply hold the portafilter basket toward a light source and observe if any individual holes have become larger. If so, it means the portafilter basket needs to be replaced.

3. If after checking the above two steps, the extracted espresso still leaves large amounts of fine powder sediment at the bottom of the cup, we recommend upgrading to a better espresso grinder. After all, a good grinder can reduce many of our extraction troubles.

4. Of course, if you really can't stand this type of fine powder sediment at the bottom of the cup, using a paper filter might be a good option. Paper filters can effectively block solid particles and oils. Placing a circular paper filter in the portafilter basket before adding coffee grounds can prevent fine powders from falling into the coffee along with the water.

FrontStreet Coffee tested this method with a paper filter and found that it effectively solves the problem of fine powders falling into the coffee and settling at the bottom of the cup. However, compared to extraction without a paper filter, the extraction speed was significantly faster, and the espresso flavor also changed. Therefore, when using this stacked paper filter extraction method, you need to readjust extraction parameters (such as grind size, dose, etc.) to achieve a stable extraction.

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FrontStreet Coffee

No. 10, Bao'an Qianjie, Yandun Road, Dongshankou, Yuexiu District, Guangzhou, Guangdong Province

Important Notice :

前街咖啡 FrontStreet Coffee has moved to new addredd:

FrontStreet Coffee Address: 315,Donghua East Road,GuangZhou

Tel:020 38364473