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

The Rise of Cold Brew Coffee

Recently, the global coffee market has seen significant growth in demand for cold brew coffee, which has also brought some conceptual ambiguities and unexplored territory. 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? FrontStreet Coffee is here today to answer that question and share our store's exclusive recipe.

Understanding Cold Brew Coffee

Unlike regular hot-water brewing, cold brew mainly involves mixing coffee grounds with cold water or room temperature water and letting them sit for several hours in a low-temperature environment, then filtering out the grounds to obtain an 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 with other extraction methods that demand strict parameters, cold brew is highly forgiving. From bean selection to the sealed container, to the coffee-to-water ratio, grind coarseness, and steeping duration, it all has a wide adjustable range. In other words, as long as you avoid particularly extreme parameter combinations, you can make good-tasting iced coffee.

Some friends have still run into problems during their attempts: they clearly use the same coffee beans and copy the parameters exactly, yet the cold brew they make is just not as rich and sweet as what they drink in the shop. Why is that? FrontStreet Coffee has summarized several key details here. Friends making cold brew at home might want to check against these to see where the problem lies.

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 is the main brewing medium, temperature directly affects extraction efficiency: too high or too low changes the taste, and likewise, too long over-extracts while too short under-extracts. Since cold brew only comes into contact with low-temperature water of 4-10°C throughout the process, extraction efficiency is very slow, so the steeping time must be extended to release more aromatic substances and allow sugars, organic acids, and other compounds to dissolve more completely. The resulting coffee is more balanced in acidity, sweetness, and body. Generally, the steeping time for cold brew is recommended to be kept within 8-18 hours.

FrontStreet Coffee once conducted a time-variable cold brew experiment, grinding equal amounts of "Butterfly" coffee and steeping them for 4 hours, 10 hours, 16 hours, and 24 hours respectively. 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, the former relatively refreshing and the latter richer.

If you're worried about losing track of the time, you can also follow FrontStreet Coffee's lazy approach: start steeping between 7-9 PM the night before, then filter and remove the grounds between 7-9 AM the next morning. That keeps the time within the conservative range of 10-14 hours.

2. Too-Fresh Coffee Beans Can Also Affect Extraction

In many high-temperature brewing methods, freshly roasted beans are often the first choice, because beans outside their optimal tasting window have greatly reduced aroma, a point everyone agrees on. Second, the release of gas lets us visually judge whether beans are fresh, whether that is the crema in espresso or the bloom during a pour-over, both of which indicate that the coffee is at its peak aroma stage.

Coffee beans heat up continuously in the roaster, and freshly roasted beans contain a large amount of carbon dioxide. To extract the internal aromatic compounds, that gas must be released first. Cold brew itself is a relatively static extraction, and low-temperature water to some extent inhibits the release of this gas, so it's easy to see why using "fresh beans" for cold brew can lead to under-extraction. If you're not in a hurry to drink it, FrontStreet Coffee suggests choosing 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, seal the container and put it straight in the refrigerator after adding water. The surface of the coffee grounds may look moistened, but in reality some local areas haven't come into contact with water, so that dry part of the coffee never participates in the extraction. In addition, after a night of standing, most particulate matter settles at the bottom of the container. At that point, if you pour it straight out to filter, you're very likely to get only the light-colored liquid from the upper layer, and the taste probably won't be very good. For this reason, stirring must be part of the cold brew process.

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 grounds and water thoroughly before putting it in the refrigerator, then stir it a few more times after taking it out and before filtering. With 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, including the built-in filter screen of a cold brew pot, metal filters, filter paper, and flannel cloths. Different pore structures naturally block different particulate matter effectively.

Take 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 relatively fine, yet fine powder and ultra-fine powder still precipitate. If the liquid is not filtered again, a layer of flocculent oily sheen floats on the surface. The flavor of the coffee when drunk doesn't differ much from when filtered, but the rough feeling left on the tongue when swallowing is obvious, and some visible powder still settles at the bottom of the cup after drinking.

For a better drinking experience, FrontStreet Coffee uses higher-density filter paper to filter it again, which not only removes ultra-fine powder effectively but also blocks more than 80% of condensed oils. After separating the grounds, FrontStreet Coffee also places the cold brew liquid in the refrigerator for sealed chilling for 3-4 hours, allowing the flavor substances to settle and mature further. Treated this way, the cold brew tastes full in flavor, with a clearer taste and more transparent acidity.

FrontStreet Coffee Recommendation

Cold brew rewards beans with clear fruit and floral character, and FrontStreet Coffee's cold-brew lineup is built for exactly that. FrontStreet's Strawberry Candy, a Gesha blend of Panamanian Gesha and Costa Rican honey-processed coffee, brews into a lively sweet-and-sour cup with rose, orange, grape, dried blueberry, and strawberry gummy notes, and it turns wine-like if left to ferment a little longer. For a floral, low-bitterness option, FrontStreet's Natural Huakui from Ethiopia shows magnolia, cream strawberry, dried mango, guava, and black tea in cold brew, while FrontStreet's Kenya Cherry Tomato brings a fuller juice texture with cherry tomato, snow pear, black plum, and smoked plum acidity.