How Does Coffee Extraction Affect a Weak Espresso Shot?

Espresso tastes weak when the brew ratio and extraction yield are off, not simply because too little liquid was pulled. In Front Street Coffee's tests, a 20g dose ground and extracted for 30 seconds to 40g of liquid was split into three 10-second cups: the first was thick and caramel-sweet, the second nutty and balanced, and the third thin and pale. Concentration falls as extraction continues, so pulling more liquid dilutes the shot rather than strengthening it.

The fix depends on roast level. For darker roasts, a shorter ratio around 1:1.5 to 1:2 keeps body and sweetness; for lighter roasts, a slightly longer ratio and finer grind help reach a higher extraction yield without going watery. Front Street Coffee recommends adjusting grind size and dose before extending time, then tasting the start, middle, and end segments to judge where flavor drops off.

Many home coffee enthusiasts often encounter the problem of weak coffee flavor and lack of aroma when making espresso. Among the factors that affect whether a cup of espresso tastes good, the flavor and concentration of the espresso are key. This article starts from Front Street Coffee's extraction experiments, analyzing the relationship between concentration and extraction yield by tasting the beginning, middle, and end segments of espresso, answering whether concentration can be improved by extracting more, and providing concentration improvement plans for coffee beans of different roast levels, helping you find the appropriate brew ratio and extraction strategy.

From an extraction perspective, whether a cup of espresso tastes good first depends on the choice of coffee beans, followed by the flavor and concentration of the espresso, and finally details such as the ratio of accompanying ingredients and temperature. Among these, making espresso troubles many home coffee enthusiasts due to various unexpected situations.

For example, when the concentration of the espresso is insufficient, the coffee tastes weak or "watery" and has almost no aroma. When facing this situation, some people asked Front Street Coffee: without changing the grind size, if I want to increase coffee concentration, can I extract more coffee liquid? Or should I extend the espresso extraction time?

What factors are related to the concentration of espresso?

Let's first observe the complete extraction process of espresso. Here, using the parameters debugged today for Front Street Coffee's classic espresso blend, we extracted a shot of espresso (20g grounds, 30 seconds, 40g coffee liquid), then used three cups to capture the beginning, middle, and end segments of the espresso in 10-second intervals, and tasted the three parts in order.

It can be seen that the color of the coffee liquid goes from dark to light, and the texture goes from viscous to thin. The first cup has the highest aroma and concentration, with a rich caramel aroma and a slightly salty taste; the second cup has a moderate mouthfeel, with nutty flavors, relatively balanced; the third cup has the lowest concentration, and the crema begins to turn white. This means that the concentration of the coffee liquid gradually decreases as the extraction amount increases, the aroma fades from strong to weak, and the mouthfeel goes from thick to thin.

Can coffee be extracted a bit more?

Theoretically, the substances in coffee that can be brought out by water account for about 30% of the bean's weight. Among these 30%, some are pleasant and delicious, while others are less appealing negative flavors. The Golden Cup standard believes that when the coffee extraction yield is in the range of 18–22%, the dissolvable aromatic substances obtained are relatively delicious.

From the above observation of espresso, when the crema completely turns from yellow to white, it actually indicates that most of the good flavor substances in the coffee have already been released, and we need to stop extraction. If hot water continues to wash through the coffee bed, the remaining negative flavor substances, such as woody notes and bitterness, will fall into the coffee cup with the liquid. Therefore, just like pour-over, if you want espresso to taste good, you need to properly control the extraction yield of the espresso, that is, while obtaining good flavor substances, you must also avoid as much as possible the negative mouthfeel brought by excessive substances.

Unlike pour-over coffee, because the water output of an espresso machine is difficult to measure directly, we are more accustomed to using the "brew ratio" as the main parameter for controlling espresso extraction.

The brew ratio depends on two factors: one is the amount of coffee grounds, and the other is the weight of the coffee liquid. Generally speaking, the industry-recommended brew ratio is between 1:1.5 and 1:2.5, among which 1:2 is the most common. For example, Front Street Coffee suggests that beginners making espresso for the first time should first extract at 1:2, then adjust up or down according to needs, because espresso made at this ratio often has a sufficiently high concentration without losing the coffee flavor it should have.

Front Street Coffee once did a simple little experiment: while keeping water temperature (94°C), pressure (10 Pa), grind size (Galileo Q18 setting 2), and dose (20g) and other parameters unchanged, Front Street Coffee extracted three espressos with different liquid weights in sequence: 40g, 46g, and 55g, corresponding to ratios of 1:2, 1:2.3, and 1:2.75, then tested the concentration of each cup and tasted its flavor.

The compiled data shows that the more coffee extracted, the lower the concentration, and the coffee's flavor also begins to deteriorate as the liquid volume increases, showing signs of over-extraction. Combining this with the extraction rules of espresso, Front Street Coffee found that when the grind size and dose remain unchanged, an increase in espresso yield (longer time) means more hot water passes through the coffee grounds, extracting more dissolvable substances, so the extraction yield is higher. At the same time, more water means the coffee is more diluted, so the concentration is instead lower.

What should be done to make coffee stronger?

1. When we use medium-dark roasted coffee beans, the aromatic substances are usually concentrated in the beginning and middle segments, while the tail end often "dilutes" the espresso. To increase coffee concentration, Front Street Coffee recommends using a high-concentration, low-extraction approach by discarding the tail end, turning it into a Ristretto.

Taking 20g of coffee grounds as an example, the original 1:2 brew ratio requires extracting 40g, while the adjusted plan of 1:1.5 requires extracting 30g. This way, the coffee flavor will be richer and the mouthfeel more substantial.

2. If the coffee beans you use are fruity SOE or medium-light roast blends, with an overall sour taste and light aroma, and you want the coffee to show high concentration, you can appropriately extend the extraction time to increase the extraction yield.

For example, when Front Street Coffee applied the "basic formula" to make Huakui SOE flat white, the coffee flavor was overall weak, and even the aroma was covered by the milk, so an additional 0.5g of grounds was added to extend the extraction time to 33–35 seconds, thereby releasing more flavor substances and giving the milk coffee a richer fruity aroma.

The above content is compiled by CoffeeHunters, a coffee news website.