The Cold Brew Mistake That's Leaving You With A Bitter Batch

Compared to regular brewed coffee, cold brew can be more refreshing in a few different ways: beyond being cold (obviously), cold brew has more caffeine than iced coffee, and it tastes much smoother. Unlike regular black coffee, pure cold brew shouldn't taste bitter or sour at all, unless you're adding lemonade to your cold brew. So you don't need to fill it with milk and sweeteners to make it go down easy (I don't add anything to coffee, but I don't mind bitter flavors). That said, if you make a mistake while brewing cold brew, it can absolutely turn out bitter — and not in any sort of pleasant way.

For advice on avoiding that, we spoke to Darren Spicer, the co-founder of Clutch Coffee Bar, a popular coffee chain in the Carolinas. Spicer explained that the amount of time you let cold brew steep is critical for determining flavor. If you let it sit too long, it'll slowly become bitter tasting. According to Spicer, "Cold brew should be steeped for 16 to 20 hours to achieve proper extraction and avoid bitterness. The exact time of steeping really is about personal taste and the beans so you may need to experiment." Beyond that, he's found from personal experience that cold brew made in the fridge (rather than, say, on the kitchen counter) tends to taste much less bitter once it's ready.

So, where does the bitterness come from? That involves another term for steeping coffee grounds: extraction. The cold brew process involves cold or room temperature water instead of hot water, which takes longer but follows the same basic steps. The water extracts flavor (or acids, sugars, and plant fiber, specifically) from the ground coffee beans. If you steep the grounds for too little time, it tastes mild because it didn't pull out much flavor. But, if you steep for too long, it extracts too much of the plant and tastes off. 

Darren Spicer did note that "bitter" can be a tricky word, because too often, people use it as a catch-all term for coffee that tastes bad. According to Spicer, "Often people not trained to be professional tasters will say something tastes 'bitter' when in reality it could be sour, astringent, stale, rancid, or bitter. Each of these different negative flavor characteristics could be caused at many different stages of the process and could also be compounding." Besides the steeping time, unpleasant cold brew flavors can also come from undersaturated or stale coffee grounds, an incorrect ratio of coffee and water, poorly filtered water, or too-finely ground coffee (Grind size also impacts coffee flavor). Steeping time is easiest to control, but there's a lot to look out for to avoid a bitter cold brew — or an astringent or rancid cold brew.