What is Cold Brew Coffee? What Factors Affect Cold Brew Coffee?

The Rise of Cold Brew Coffee

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Recently, the global coffee market has seen a significant growth in demand for cold brew coffee, which has also brought some conceptual ambiguities and areas yet to be explored regarding cold brew coffee. So-called cold brew coffee refers to an extraction method, not a type of cold drink. In the industry, cold brew coffee is clearly defined as coffee obtained by extracting flavor molecules with low-temperature water. So what factors affect the taste of such a cup of coffee? FrontStreet Coffee is here today to answer this question and share our store's exclusive recipe.

Understanding Cold Brew Coffee

Unlike regular hot water coffee brewing, cold brew mainly involves mixing coffee grounds with cold water (room temperature water) and letting it sit for several hours in a low-temperature environment, finally filtering out the grounds to obtain iced coffee liquid. With a bag of coffee, a sealed clean container, water, and a refrigerator, you can achieve cold brew freedom at home.

In fact, compared to other extraction methods with strict parameters, cold brew has high compatibility. From coffee bean selection to the sealed container used, and then to the coffee-to-water ratio, grinding coarseness, and steeping duration, it all has a large adjustable range. In other words, as long as you don't use particularly extreme parameter combinations, you can make good-tasting iced coffee.

However, some friends have encountered problems during their attempts:明明采用的是同一款咖啡豆，参数也"照搬照抄"了，做出来的冷萃就是不如店里喝到的浓郁香甜，这是为何呢？Here, FrontStreet Coffee has summarized several key details. Friends making cold brew at home might want to check against these to see if the problem lies here.

1. Steeping Time Should Not Be Less Than 8 Hours or Exceed 18 Hours

In pour-over coffee, we pay special attention to water temperature and time. Because water as the main brewing medium, temperature directly affects the extraction efficiency of coffee—too high or too low will change the taste of coffee; similarly, too long容易过萃，短了则可能萃取不足。However, since cold brew only comes into contact with low-temperature water of 4-10°C throughout the process, the extraction efficiency is very slow, so it needs to extend the steeping time to release more aromatic substances, thereby allowing the dissolution of sugars and organic acids and other compounds to be more complete. The resulting coffee is more balanced in acidity, sweetness, and body. Generally, the steeping time for cold brew coffee is usually recommended to be controlled within 8-18 hours.

FrontStreet Coffee once conducted a time-variable cold brew experiment, grinding equal amounts of "花蝴蝶" coffee and steeping them for 4 hours, 10 hours, 16 hours, and 24 hours respectively. It was found that the 4-hour coffee had almost no aroma and tasted rather watery; the 24-hour cold brew had a slight bitterness on entry, showing signs of over-extraction; the 10-hour and 16-hour groups showed the best flavor performance, with the former being relatively refreshing in taste, while the latter was more rich.

If you're worried about not remembering the time, you can also refer to FrontStreet Coffee's "lazy person" approach: start steeping between 7-9 PM the previous night, and the next morning between 7-9 AM, filter and remove the grounds. This way, the time will be controlled within the conservative range of 10-14 hours.

2. Too Fresh Coffee Beans Can Also Affect Extraction

In many high-temperature brewing forms, freshly roasted beans are often the first consideration for many people, because beans outside their optimal tasting period will have greatly reduced aroma—this is a consensus everyone has reached. Secondly, the release of gas allows us to visually judge whether the coffee beans are fresh, such as the crema in espresso, the blooming during the pour-over, etc., which also indicates that the coffee is in its peak aroma stage.

Coffee beans continuously heat up in the roaster, and freshly roasted beans contain a large amount of carbon dioxide. To extract the internal aromatic compounds, they must be released first. Cold brew itself is a relatively static extraction state, and low-temperature water to some extent inhibits the release of this gas, so it's conceivable that using "fresh beans" for cold brew can easily lead to under-extraction. If you're not in a hurry to drink, FrontStreet Coffee thinks it's best to choose coffee with a roast date of more than 10 days for steeping, which is more conducive to making cold brew with rich aromas.

3. Stir Thoroughly Before and After Extraction

Many beginners, wanting to be quick, directly seal and put it in the refrigerator after adding water. The surface of the coffee grounds may appear moistened, but in reality, some local areas haven't come into contact with water, so obviously this dry part of the coffee hasn't participated in the extraction. Additionally, after a night of standing, most particulate matter settles at the bottom of the container. At this time, if you directly pour it out for filtering, you're very likely to only get the light-colored liquid from the upper layer, and the taste probably won't be very good. Therefore, the action of "stirring" must be added when making cold brew.

From FrontStreet Coffee's experience, if you're using a larger-capacity pot, you can use a stirring stick or a long spoon to mix the coffee grounds and water thoroughly before putting it in the refrigerator. After taking it out, stir it a few more times before filtering. When you're using a sealed water bottle, simply shake it gently up and down after closing the lid.

4. Thoroughly Filter the Grounds for Better Cold Brew Taste

There are many options for filtering coffee grounds, such as the built-in filter screen of a cold brew pot, metal filters, filter paper, flannel filter cloths, etc. Different pore structures naturally block different particulate matter effectively.

Taking FrontStreet Coffee's use of a cold brew pot as an example, the filter screen has a pore size of 245 mesh, which is considered a relatively fine type, but there are still cases of fine powder and ultra-fine powder precipitation. At this time, if not filtered again, a layer of flocculent oily sheen will float on the liquid surface. The flavor of the coffee when drunk doesn't differ much from when filtered, but the rough feeling remaining on the tongue when swallowing will be obvious, and some visible powder will still settle at the bottom of the cup after drinking.

For a better drinking experience, FrontStreet Coffee will use higher-density filter paper to filter it again, which not only effectively filters out ultra-fine powder but also blocks more than 80% of condensed oils. After separating the grounds, FrontStreet Coffee will also place the cold brew coffee liquid in the refrigerator for sealed refrigeration for 3-4 hours, allowing the flavor substances to further precipitate and mature. This way, the cold brew tastes very full in flavor, with a clearer taste and more transparent acidity.

Important Notice :

前街咖啡 FrontStreet Coffee has moved to new addredd:

FrontStreet Coffee Address: 315,Donghua East Road,GuangZhou

Tel:020 38364473