If you've ever taken a sip of coffee and felt a sour taste on your tongue, you know it's not a pleasant experience. Sour coffee is often the result of a short brew time, leaving sweet flavors not fully extracted from the bean. It can also be caused by old or under-roasted beans, or an improper grind size. Fortunately, there are ways to avoid sour coffee and make sure you get the perfect cup every time. A common cause of sour coffee is insufficient extraction during the brewing process.
This occurs when not enough flavor is extracted from the coffee grounds while brewing. The longer the coffee is brewed, the more sugars will be extracted from the grounds, which will make the coffee taste sweeter. But if you spend too much time, you'll end up with a bitter taste (overextraction).Before going into details, it must be said that within the world of coffee there are two opposite extremes of what we would call “bad coffee”, the first is “bitter” and the second is “acidic”. Both of these problems are often the result of poor roasting techniques.
In the case of sour coffee, this will result in a cup of grass-flavored coffee, while bitter coffee will taste bitter and sour. As long as you've chosen the right beans, insufficient extraction is the biggest reason your coffee tastes sour. If you can address that problem, you should reduce acidity considerably. One way to do this is to use a coarser grind size for your brewing method. With coarse-ground coffee, there's more surface area for the water to penetrate and extract all of the flavors present in the bean during the brew time. Another way to avoid sour coffee is to use freshly roasted beans.
From about a week after roasting, your coffee will have settled and will look beautiful for espresso based coffees. Unfortunately, sometimes people confuse light roasted coffee with sour coffee if that flavor feels herbaceous or underdeveloped. No matter how aromatic your coffee grounds are or how good the coffee bean looks, they don't have an infinite shelf life. If you tend to use dark roasted beans, light roasted coffee may taste sour even when the coffee is perfectly extracted. Finally, it's important to remember that there is a difference in the way coffee is produced to create a cup of coffee with a sour taste and one that is bitter. Wet processed coffee (washed coffee) generally emphasizes the quality of coffee beans, making it the more reliable of the two methods for producing increased acidity or shine. By following these tips and using freshly roasted beans with a coarse grind size for your brewing method, you should be able to avoid sour tasting coffee and enjoy a delicious cup every time.