Can Everything Be Extracted as Concentrate? Do Different Ingredients Taste Good When Extracted with Coffee? What is Coffee's Channel Effect?

If we want to add some extra aroma or flavor to coffee, we might incorporate other ingredients to allow the coffee to absorb their fragrance and taste. This is a very common practice. For example, if we want coffee to have a certain floral aroma, we could steep dried flowers in the coffee; if we want to add some sweetness to the coffee, we would add sugar or syrup...

However, this approach is usually troublesome and time-consuming (relatively speaking). The soaking time, stirring motions - all these add significant workload to the coffee-making process. Therefore, many clever people might wonder: if we add ingredients directly into the coffee extraction process, couldn't we just have these ingredients' aromas and flavors extracted along with the coffee substances by hot water? This approach not only saves time and effort but also allows the flavors to blend more completely and naturally.

For most coffee-making methods, this approach can indeed effectively streamline the preparation process. However, when it comes to espresso, FrontStreet Coffee does not recommend this practice! Why? Because coffee made this way rarely tastes good.

Why Doesn't FrontStreet Coffee Recommend Adding Ingredients to Espresso Pucks?

In the article "Can You Taste the Difference Between Coffees Made with 0.5g Less Coffee?" published a couple of days ago, FrontStreet Coffee shared that the average pressure used during espresso extraction is about 9 bar. This 9 bar of pressure applied to a 58mm diameter puck equals approximately 240 kilograms of force - about the weight of three adults. Such high pressure allows substances in the coffee grounds to be extracted quickly, but it also makes extraction more difficult to control. Two seconds more or less in extraction time, a slight variation in coffee dosage - all these factors can cause significant differences in the extracted substances.

Additionally, this highly efficient extraction can easily lead to water "channeling," preventing the coffee from being extracted evenly. As we know, water follows the path of least resistance, flowing preferentially to areas where it can move more easily. This phenomenon is particularly amplified in the espresso extraction environment. This is precisely why we need to level and tamp the coffee grounds properly. Espresso requires pressure-assisted extraction because we want to quickly extract substances from coffee to make a good cup in a short amount of time. According to Fick's law, the rate of substance release is directly proportional to the contact area. Therefore, we need to increase the contact area by grinding coffee beans finer to enhance the rate of substance release.

Fine grinding reduces the gaps between coffee particles. After tamping, this forms a densely packed, water-resistant puck. This is why pressure assistance is needed to allow hot water to pass through the coffee layer and quickly extract coffee substances. However, if several easily flowing channels suddenly appear in this "impermeable" puck, then during extraction, hot water will concentrate its flow through these channels. This ultimately causes over-extraction of coffee grounds within the channels and under-extraction of grounds outside the channels - this is what we call "channeling effect." For espresso which relies on pressure-assisted extraction, this is a very common phenomenon.

The Connection Between Channeling and Added Ingredients

Why did FrontStreet Coffee take such a roundabout way to introduce the channeling effect? It might seem unrelated to our topic, right? (Please first dismiss any thoughts about this being filler content)

But in reality, the connection between these two is closely intertwined! The reason why channeling occurs in a puck is simply because the coffee grounds are not distributed evenly - some areas have more coffee, others less. Or, some areas have higher density while others have lower density. There are many reasons for these situations: uneven distribution, imperfect tamping, or the addition of foreign materials that disrupt the puck's structure. What FrontStreet Coffee mentioned at the beginning belongs to this third category!

Whether adding flower fragments to coffee grounds, or sugar, salt, or other seasonings, even with perfect distribution and tamping, the puck's structure will be disrupted during extraction due to the presence and dissolution of these materials, resulting in channeling. FrontStreet Coffee conducted experiments last year by adding 5g of sugar to the puck for extraction. The result was not only frequent splattering during extraction, but the coffee's taste became indescribable due to uneven extraction - all consequences of channeling. Most importantly, the sugar and coffee didn't blend well together, resulting in a very jarring taste sensation.

Furthermore, if you add ingredients with oils or other hard-to-clean substances like butter, then congratulations - you'll have plenty to do after brewing. Last year, it was very popular to place a piece of butter at the bottom of the portafilter to create "butter coffee waterfall effects." A friend of FrontStreet Coffee tried this and not only failed to make delicious butter coffee but also spent a long time cleaning the espresso machine - a truly unrewarding experience.

Conclusion

In summary, you now understand why it's best not to add other materials during espresso extraction. This approach neither allows the ingredients to blend perfectly with the coffee nor disrupts the even extraction, making the coffee taste unpleasant. It also tends to create additional work. Therefore, if you want to add other flavors to espresso, it's best to mix them in after the extraction is complete. This way, you won't introduce too many unstable factors into the process.

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