Beer School: What Makes a Sour Beer Sour?

Sours are one of my favorite beer styles by far. Growing up, I loved sour candy and as an adult I’m a big fan of fruit flavor in beer, especially in the summertime. Plus, I think sour beers just feel fun. One of my big beer wonderings has always been about how sour beer gets such a distinct taste, so I did some investigating, AKA I asked my friends at Craft-A-Brew. They know a thing or two about the brewing process. They also helped me through my very first homebrewing process! I still feel like a proud mom thinking about that chocolate milk stout I made all by myself! But I digress. Here’s a quick beer school primer on what makes a sour beer sour.

First, the answer to the big question, what makes a sour beer sour? Answer: lactic acid. So these bacteria called lactobacillus produce lactic acid. Just like how yeast converts sugar to alcohol during fermentation, lactobacillus converts sugar into lactic acid.

You may have heard of kettle souring. This is a great way to make sour beer in a controlled environment. With kettle souring, you introduce lactobacillus after the malts but before the hops and yeast. Hops are a natural preservative so it could impede the souring process. Adding them after lets the lactobacillus more effectively create lactic acid. So, the lactobacillus takes about four days to do that, and then the hops are added and the brewing process continues.

Well there you have it. That’s what makes a sour beer sour. What sour beers are you sipping on this summer?

Beer SchoolNora Nolden