Many coffee enthusiasts can rattle off latte art and equipment knowledge, yet when it comes to extracting espresso, they pay insufficient attention to distribution, dose control, and tasting judgment. In fact, dose control is just as critical as grind adjustment—fluctuations in dose mean that even the most beautiful latte art cannot mask an imbalanced coffee. This article starts from the TDS and extraction yield formulas, combines a 2.3-gram dose difference measured on a Mazzer Robur grinder, and uses chart data to illustrate the specific effects of dose on concentration, extraction yield, and the acid-bitter balance, while also exploring approaches to dosing for light-roast espresso. Front Street Coffee also emphasizes the importance of dose consistency in daily production, and we hope this article provides practical reference for your extraction adjustments.
Based on my personal observations, here in China I have seen stunning latte art, many players who can talk at length about espresso machine equipment, and seasoned enthusiasts who know every major growing region like the back of their hand.
However, when I discovered that quite a few people neither distribute their grounds nor control their dose when extracting espresso—and don't even taste to judge—I genuinely found it hard to understand.
If something goes wrong in the extraction, then no matter how exquisite the latte art, the coffee itself is outwardly splendid but inwardly hollow.
If the dose cannot be controlled consistently, then production and quality control are out of the question.
And once quality control is lost, so-called flavor descriptions and explorations of coffee varieties essentially become castles in the air.
From a sensory perspective, the acid-bitter balance is the key thing to grasp. To achieve acid-bitter balance—or even extract sufficient sweetness—you need to know how to adjust the grind setting on one hand, and how to adjust the dose accordingly on the other. There is of course also extraction time as a variable, but that is not the focus of today's discussion.
Regarding grind adjustment, any basic coffee course—whether pour-over or espresso—lists it as required content.
But the problem is that we don't talk much about dose control, or we merely stop at fairly mechanical standards, such as 14 grams for a double, or filling the hopper and giving it two "smack-smack" leveling taps. In reality, dose adjustment is just as important as grind adjustment. Today, I will use considerable space to explain the importance of dose control.
In past extraction diaries, we have already learned:
1. Concentration determines how intense the coffee is, and what determines concentration is the soluble material. It's worth mentioning that XLW007 from the Common Sense Group once noted that insoluble material can also enhance coffee's body—I completely agree, but this time I will focus only on soluble material as the main factor. Its calculation can be measured with a refractometer:
TDS% = TDS/Coffee Weight, that is, the percentage of soluble material equals the grams of soluble material divided by the total weight of the coffee.
2. This portion of soluble material comes from the dose of coffee grounds. Therefore we can derive the extraction yield:
EY = TDS/DOSE, that is, grams of soluble material divided by the dose used, which tells us what proportion has been extracted. In the vast majority of cases, whether espresso or pour-over, a reasonable extraction yield falls between 18–21%.
After this brief review, let's now focus on dose as the core and look at how dose affects coffee flavor. Before that, let's take the high-end Mazzer Robur electronic grinder on the market as an example. In my previous diary, if you don't distribute the grounds, there is roughly a 2.3-gram difference between the lowest and highest dose. Let's simply use this as our example—2.3 grams, seemingly only a "10%" difference in dose. What kind of difference does it make in actual production?
Let me make another assumption here: following the traditional method, extraction stops when a 60 ml double espresso is reached. Also, for ease of calculation, assume that 60 ml of coffee always weighs the same. This is a limiting condition, only for ease of understanding.
The parameters we assume are as follows:
Dose 1: 17.7 grams
Dose 2: 19 grams
The weight of 60 ml of extracted coffee is both: 38 grams
The coffee beans are relatively fresh, and a fairly standard medium roast. At the same time, tamping is fine and extraction is even.
We can obtain the following parameters, as shown in the figure:
Chart
Corresponding figure
This chart tells us:
The green area represents the reasonable extraction range.
For example, with a 19-gram dose, when the concentration is 9%, the corresponding extraction yield is 18% (38×0.09/19). At the same concentration, the extraction yield of 17.7 grams of grounds would be higher, namely 19.3%. The reason is obvious: with the same coffee weight and the same concentration, one is extracted with 19 grams of grounds and the other with 17.7 grams—clearly the 17.7 grams has a higher utilization rate.
But this chart also clearly shows that if you use 17.7 grams of grounds while ensuring a 38-gram coffee weight, the concentration cannot exceed 10.25%, even though espresso concentration can reach 11%.
Perhaps the data needs time to digest, but I can offer a few summaries and insights:
------Summary of dose consistency-------------------------------
1. When all other parameters are consistent for each extraction, if the dose cannot be guaranteed consistent each time and the error reaches 10%, then the extraction with the higher dose will be noticeably more under-extracted than the one with less.
2. This under-extracted one will very likely make the coffee much more sour.
-------Summary of fine-tuning the dose
3. If, when dialing in the machine, we judge whether the acid-bitter balance is right (of course, I'm assuming you are a serious barista), it doesn't necessarily have to start with adjusting the grind, because every grind adjustment requires purging the previously retained grounds.
4. From the chart, we can see that if changing the dose makes the EBF line (17.7 grams to 19 grams) steeper (greater angle), then at the same concentration, you can lower the extraction yield, which may make the sourness more prominent and reduce the bitterness. Note, this is only one possibility—many factors determine the acid-bitter sensory experience. But from the perspective of extraction yield, this is a common approach. I also want to emphasize that it's not about whether sourness or bitterness is better, but about controlling the dose to achieve acid-bitter balance.
As shown in the figure, increasing the dose turns a previously over-extracted coffee into a normal extraction.
Insights:
There is also a very important insight here: generally, for the same coffee bean, the darker the roast, the higher the body will be under the same extraction parameters. Conversely, in today's era where light roasts dominate, although light-roast espresso can express intense floral, citrus, and other fruity flavors, acid-bitter balance and full body are a tremendous challenge. Compared to dark-roast coffee beans, light roasts have lower extraction efficiency—that is, with the same dose and the same extraction time, the concentration of light roasts tends to be lower, and lower concentration makes the body of light-roast coffee a real weak point.
From this chart we can see that if you only use 17.7 grams of grounds, reaching 11% already means over-extraction. Therefore, this more or less explains why machines with small filter baskets that can't hold much grounds are not recommended for trying light-roast coffee beans. This also explains why Axil in Melbourne, where light roasts dominate, uses a 22-gram VST basket for a single double espresso! And a 22-gram basket can actually hold a full 25 grams of grounds!
As a barista, you must first know how to taste and judge, and then make corresponding adjustments based on the acid-bitter-sweet balance and body you taste. And the dose, at least as can be seen in this chapter, is an important tool.
Of course, today I used a 10% error to illustrate this issue. In reality, a 0.5-gram error is enough to change the flow rate, and if you can keep your dose error below 0.3 grams, you may be able to:
1. Achieve stable consistency in every cup of coffee you make.
2. Learn to fine-tune accordingly, thereby adjusting its flavor.
3. By combining dose adjustment with an understanding of how grind and extraction time affect coffee flavor, you can gain more control over your coffee making.
In the next chapter, I will use the development of specialty coffee making in Australia as a thread to briefly discuss how they control dose.
The scraper Scottie invented 4 years ago also gave rise to later research on dose control.
The above content is compiled by CoffeeHunters, a coffee news website.
