The original meaning of cold brew coffee refers to the fact that at low temperatures, small-molecule substances that tend toward aroma and acidity are more easily released in cold water, so the coffee tastes light and mostly presents a sweet-and-sour profile. In addition, since it is not limited by equipment or location, cold brew can be said to be coffee that people can easily get their hands on; at home, as long as you have ingredients, a bottle and water, plus a refrigerator, you can easily achieve caffeine freedom.

At this point, some observant friends have noticed a phenomenon: unlike pour-over coffee, which is almost "unchanging for ten thousand years at 1:15," the coffee-to-water ratio for making cold brew always spans a wide range. Some people like to use 1:8, others advocate 1:13, and there are also those like Qianjie who are used to producing at 1:10. So what kind of taste experience will cold brews made with different ratios have?

What effects does the coffee-to-water ratio have on coffee?

As a typical immersion extraction, cold brew coffee is the process of extracting flavor by keeping low-temperature water and coffee grounds in the same container through long contact. When other parameters remain unchanged, the larger the proportion of water, the lower the concentration of the coffee liquid, the weaker the coffee taste, and the thinner the mouthfeel; conversely, the smaller the proportion of water, the higher the concentration, the stronger the taste, and the thicker the mouthfeel.

Therefore, in order to find a balanced taste and let the coffee present a relatively better flavor, we have to apply an appropriate coffee-to-water ratio.

How long should cold brew be steeped? How fine should the coffee grounds be ground?

We all know that the various parameters involved in any extraction plan are more or less related. For cold brew, the coffee-to-water ratio is not the only factor that determines taste; we also need to look at grind size, steeping time, water quality, and most critically, the coffee beans.

Although low-temperature extraction can reduce the appearance of bitter substances, it is not 100 percent, so if you want to pursue deliciousness, the coffee grounds used for cold brew should not be ground too fine, and even more so should not be steeped too long. For the former, we recommend controlling it within a range of about 80-85% pass rate on a 0.85mm standard sieve, looking with the naked eye like the granular texture of white sugar; for the latter, it is best to keep it within 6 to 16 hours, because this ensures sufficient contact time between grounds and water, and at the same time is not prone to showing negative flavors due to over-extraction.

The reason Qianjie emphasizes water quality is not only because it is the medium of extraction, but also because among all parameters it is the easiest for people to overlook. For example, in Qianjie's backstage there are always friends asking: clearly they purchased our coffee beans and also followed the parameters provided in the article to make cold brew, but the taste is just not as good as expected. After ruling out each "culprit," they discovered that the problem actually came from that colorless and tasteless "water." Friends with similar troubles can refer to Qianjie's past comparative experiment "Making cold brew with different waters, the difference is actually this big!"; we will not elaborate too much here.

Regarding the choice of coffee beans, here Qianjie uses Kenya AA from the bean shelf as an experimental demonstration. It uses the K72 washed processing method, and the varieties are SL28 and SL34. Both SL28 and SL34 are varieties selected after multiple cultivations. SL28 belongs to the Bourbon genetic group, carrying the bright tonality and rich acidity of the original Bourbon, while SL34's bloodline is closer to the Typica gene, with a milder acidity.

Iced coffee made from Kenya AA has an entry that feels like dark berries wrapping around the mouth, while carrying a plump cherry tomato aroma. Drinking it iced is very satisfying, so it is the first bean choice for many friends when making cold brew.

How does cold brew coffee made with different coffee-to-water ratios taste?

Since cold brew is always carried out in an environment of 0 to 10°C, the extraction efficiency is very low. In addition, the coffee grounds and water are in a relatively static state, and there is no external force driving them in the middle, so the speed at which the coffee grounds dissolve flavor substances is very limited. To make the experimental results clearer, Qianjie set up 4 relatively common coffee-to-water ratios, namely 1:8, 1:10, 1:12, and 1:15, with all other parameters kept unchanged.

The production steps were all consistent: pour the coffee grounds and water into the container in sequence, then stir, seal, and place them in the refrigerator one by one. When the time was up, we took them out and filtered them (they can be stirred once midway).

Coffee beans: Qianjie Kenya Little Tomato

Dose: 18g

Steeping time: 6 hours

Grind size: fine sugar / China No. 20 standard sieve pass rate 80% (EK43s setting 9.5)

Coffee-to-water ratio: 1:8, 1:10, 1:12, 1:15

Corresponding water amounts: 144g, 180g, 216g, 270g

The coffee liquid with a coffee-to-water ratio of 1:8 had the darkest color, the strongest and most sour taste, and a mouthfeel that was even a bit salty; the flavor had only a little berry, with a bitter finish;

The coffee liquid with a coffee-to-water ratio of 1:10 smelled of fresh sugarcane, with flavors of red plum, berries, and snow pear tea; the mouthfeel was slightly on the strong side, with high acidity and not obvious sweetness;

The cold brew with a coffee-to-water ratio of 1:12 had the clearest mouthfeel, with flavors of cherry tomato, red plum, smoked plum juice, sugarcane, and the lingering fragrance of preserved plum candy; the concentration was moderate, with balanced acidity, sweetness, and bitterness;

The coffee liquid with a coffee-to-water ratio of 1:15 had the lightest color and a relatively thin body, with only a little acidity from black plum and berries; the taste was bland, but there was almost no bitterness.

From the above comparison, it is easy to see that because the 1:8 ratio uses less water, the coffee flavor does not have enough room to develop, and it also tends to show negative characteristics of being heavy and bitter; the 1:15 ratio, on the other hand, uses more water, so the soluble substances are overly diluted, resulting in insufficient body in the coffee, which naturally tastes thin and bland.

Among the 1:10 and 1:12 groups, the cold brew made with 1:12 clearly had the best flavor and mouthfeel when drunk directly, but Qianjie gives priority to 1:10 in many articles and daily service. Why is that?

For cold brew service, Qianjie mainly considers two points.

First, in order to keep the cold brew at a low-temperature mouthfeel, besides using a chilled glass, we also add 1 to 2 hard ice cubes, so that even if the coffee is diluted, the flavor will not change too much; second, because every customer has different taste preferences, some like it light and some like it strong, when the ice cubes are first added the coffee tastes full and rich, and as they slowly melt into water over time, the coffee gradually becomes lighter. Therefore, using a high-strength version of cold brew plus ice satisfies both the "strong-flavor camp" and the "light-flavor camp."