Is it normal to have coffee grounds at the bottom of a latte? How to solve the issue of powder residue in espresso extraction?

Have you ever encountered this situation: after finishing your coffee, you notice some fine powder particles settled at the bottom of the cup? Sometimes when you buy an iced latte from a shop, you find black sediment at the bottom as well.

Is this normal? Does it affect the drinking experience?

These black powder particles deposited at the bottom of the coffee cup are actually superfine particles that have passed through the holes in the portafilter basket and fallen with the coffee liquid. This is the same principle as having some soy pulp sediment in soy milk or a small amount of fruit pulp in juice.

If the amount of superfine particles in a single shot is minimal, it's considered normal. It won't affect the coffee's taste profile or harm your health, and can even be negligible. However, when you visually observe black particles obviously mixed in the coffee, it means there's an "unusual" amount of powder, and it's highly likely that something went wrong during the extraction process.

Why do so many fine particles appear?

It's important to know that espresso-ground coffee powder is as fine as powdered sugar, with particle sizes between 150-300 microns. The naked eye cannot observe the degree of fineness and uniformity - you need to judge the correct grind by observing the extraction state of the coffee liquid. The portafilter basket used for espresso extraction consists of a mesh of tiny holes that serves as a filtering device. If you hold the basket up to a light source, the light passing through the mesh reveals the size of the holes.

When coffee is ground very fine, the amount of superfine particles increases. Under high-pressure extraction conditions, particles smaller than these tiny holes are easily pushed through by hot water and fall into the coffee. The fine particles that fall into the coffee generally don't sink to the bottom immediately but gradually settle after a few minutes without stirring. If you drink it in large gulps, most of these fine particles will be consumed along with the coffee liquid.

Besides grinding, careless operations can also cause the finished coffee to contain unusual powder residues. For example, if the coffee machine's group head has residue from the previous shot and hasn't been flushed clean with water. Or if there's some powder on the portafilter handle, it could potentially transfer into the cup.

So, how should this be resolved?

1. First, check if the powder residue is caused by improper operation on your part. If so, you need to develop the good habit of cleaning the group head and portafilter regularly to avoid cloudiness in your coffee.

2. Under long-term exposure to high temperatures and pressure, the mesh holes in the portafilter basket can deform, allowing more fine particles to pass through. However, this situation isn't common and might only occur after 1-2 years of intensive use. Simply hold the basket up to light and observe if any individual holes have become larger. If so, it means the basket needs to be replaced.

3. If the coffee extraction flow rate is slow and there are too many fine particles distributed, FrontStreet Coffee suggests adjusting the grind to be slightly coarser to make the overall particles larger, which will correspondingly reduce the amount of superfine particles. If the coffee flow rate then becomes too fast and the flavor becomes weak, you can compensate by appropriately increasing the dose.

4. Filter paper is currently the best filtering material available, capable of blocking solid particles and oils. Coffee extracted using filter paper has the highest level of cleanliness. If after adjusting to a coarser grind, your coffee still contains a small amount of powder particles that you find unacceptable, try placing a circular filter paper in the portafilter basket during extraction.

FrontStreet Coffee has also tested this method and found it does effectively solve the problem of fine particles falling into the coffee. However, because it blocks most of the fine particles, it speeds up the coffee flow rate while reducing both concentration and extraction yield. Therefore, when using filter paper for espresso extraction, the grind needs to be adjusted (slightly finer), otherwise the espresso's flavor will definitely change.

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