How Does Cold Brew Coffee Extraction Turn Bitter?

Cold brew uses cold water and a long low-temperature steep, which draws out the sweet and acidic compounds in coffee while limiting the bitter ones. Bitterness at home usually comes from two things: a dark roast brewed at a high concentration, or steeping past roughly 12 hours, when harsh and astringent compounds start to appear.

As coffee bean seeds, beans carry more oils than other parts of the plant, and the darker the roast, the more those oils show on the surface and in the cup. The usual steep runs 8 to 12 hours, so filter the grounds out completely once that window closes.

Cold brew coffee, with its low-temperature slow extraction process, can better preserve the sweet and sour flavors in coffee beans while inhibiting the release of bitter substances, delivering a clean, mellow taste. However, many people encounter unbearably bitter cold brew when making it at home. This article will start with the flavor characteristics of cold brew coffee, thoroughly analyze the common causes of bitterness, and share the correct brewing method recommended by Front Street Coffee. Whether you prefer light-roasted beans with bright fruity acidity or dark-roasted beans with rich intensity, you'll find a cold brew solution that suits you here, making every cup of cold brew showcase its best flavor.

Cold brew coffee is a coffee extraction method. Through cold water and prolonged low-temperature immersion, the sweet and sour substances in coffee beans are fully released, while the unpleasant bitter and astringent flavors are prevented from emerging. This not only gives the coffee a fuller body but also maintains its overall cleanliness.

Reasons Why Cold Brew Coffee Tastes Bitter/Unpleasant

Since coffee beans are seeds, and seeds contain more oils than other parts of the plant, regardless of the variety, the darker the roast, the more the oils will manifest on the bean surface and in the mouthfeel.

According to the brewing experience of Front Street Coffee, light-roasted coffee beans typically produce a lighter body, more juice-like quality, more pronounced fruity acidity, and uplifting floral and fruity aromas—smelling unlike the coffee you'd expect; while dark-roasted coffee beans produce a heavier, richer body, deeper aromas, and a smell closer to the conventional "coffee scent."

If your cold brew coffee is very bitter, it may have been made with dark-roasted coffee beans at a high concentration. In this case, Front Street Coffee recommends adding an appropriate amount of cold water or ice cubes to dilute it.

If light-roasted coffee beans were used, the bitterness may be caused by steeping for too long. Generally, cold brew coffee is steeped for 8–12 hours. Steeping for too long causes the coffee grounds to release all the pleasant flavor compounds, and then the bitter and astringent substances that wouldn't otherwise be released will also gradually emerge. So after steeping for 12 hours, be sure to filter out the coffee grounds completely before sealing and storing.

The Correct Way to Make Cold Brew Coffee

Due to its extraction characteristics, cold brew coffee can highlight the wine-like notes, fruity fermentation, and fruity aromas in coffee. Therefore, for the coffee beans used in cold brew, Front Street Coffee recommends using medium-light to medium-roasted coffee beans with rich fruity flavors, or beans with particularly prominent aromas. For example, "Front Street Costa Rica Mozart coffee beans, with the aroma of dried grapes," "Front Street Ethiopia Rose Valley coffee beans, with rich mixed berry acidity and aroma," "Front Street Honduras Sherry coffee beans, with whisky-like aroma."

Regardless of which coffee beans you use, the prerequisite is to choose freshly roasted ones. After roasting, coffee goes through a 4–7 day resting period and then enters its optimal flavor window. After this period, the coffee's aroma accelerates its dissipation, and the flavor and mouthfeel deteriorate significantly. To ensure everyone enjoys coffee at its best flavor period, Front Street ships beans freshly roasted within 5 days, so the coffee beans you receive are at peak aroma.

For daily cold brew coffee making, Front Street Coffee tends to use medium-light roasted coffee beans. As for the container, all you need is a clean, sealable one. Prepare 40 grams of coffee grounds, grind to a fine grind (85% passing through a No. 20 sieve), pour into the container, then add 480 milliliters of cold water. Stir evenly with a wooden stick and cover with the lid.

Place in the refrigerator and refrigerate for about 12 hours. After filtering out the coffee grounds, the coffee liquid is ready to drink immediately. You can also pour the filtered coffee liquid into a bottle and continue refrigerating for 4 hours for an even better flavor and mouthfeel~

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