Kettle Sours: A Debate

There’s a debate around kettle sours.

Lattobacilli kettle sours

Image courtesy of Wikipedia, used under Creative Commons licence. Adapted for size.

Simply, kettle souring is a process of making sour beers that’s quicker and cheaper than some traditional souring methods.

Most of the debate centres around two points; the tradition of brewing sour beers and the labelling and marketing of kettle sours.

I’ll dig into the arguments for and against below but first, some background…

Kettle Souring: A Brief & Basic Overview

There are various methods of producing sour beers but here I’ll focus just on kettle souring. For more information, I recommend reading the Sour Beer Blog.

To produce sours beers, brewers will often turn to the bacteria Lactobacillus. This bacteria produces lactic acid which contributes acidity and sour flavours to beer.

Often Lactobacillus is combined in the brewing process with traditional brewers yeast, Sacchoramyces. In kettle soured beers, the former is used to create a base level of lactic acid in the unfermented beer while the latter is used to ferment the beer as you normally would.

The contrast with more traditional methods of souring being that bacteria is added before the boil, whereas in many older sour styles, this is done after the boil and left to ferment, age and mature.

Traditional sour beers are often blended to achieve the right combination of pH and flavours.

Benefits of Kettle Souring

The benefit of the kettle souring process is that a brewer can produce a controlled level of acidity in the wort before boiling and killing off the Lactobacillus to prevent the bacteria from further souring the beer. Boiling also acts as a step in sanitising the beer, and to some extent the equipment.

Further benefits have already been mentioned and should be fairly obvious. This is a relative quick and affordable way of brewing a sour beer that differs only slightly from the typical process.

It doesn’t require extensive investment of time, money or additional equipment. And while the brewer’s skill is going to play a massive part in the end product, the process itself allows for a good amount of control and limits potential off-flavours or contamination.

Criticism of Kettle Sours

The criticism of the process often comes from purists. And while I’ll say now that I don’t agree with many of the arguments against kettle sours, I understand where they’re coming from.

A Romantic Tradition

Critics focus on notions of the artistry and craft of traditional sour beers, of spontaneous or open fermentation, or of wood-aging beers.

Inoculating a beer with Lactobacillus in the kettle before the boil doesn’t quite have the same romanticism as the image of large wooden koelschips in a Belgian monastery. A fair point but one which I think misses the fundamental difference in what the brewer is trying to achieve.


Another point some critics come up with is that, because of the cost and efficiency involved in kettle souring, brewers can create beers cheaply but price them in line with more expensive sours.

This is something I’ve yet to witness but if it started happening in Australia, it’s obviously something I’d be against.

Labelling and Marketing

Finally, labelling can be an issue. Sour beer enthusiasts rightly want to know if their beer has been kettle soured. When the labelling or marketing of the beer is misleading, consumers have some right to be critical.

Luke Robertson of Ale of a Time wrote an interesting two part piece on the categorisation and naming of beer. It included mentions of Dr. Funk, and the Spontaneously Fermented series, which were both kettle soured.

Despite the criticism of some purists, it seems it’s less the process that’s now most controversial than how the beer is labelled and marketed.

It’s in this case that some have raised questions over the naming of the Spontaneously Fermented series.

Kettle Sours: Good or Bad?

As for kettle souring as a process? For me, it’s just another tool in the brewer’s arsenal.

As for kettle souring as a process? It’s just another tool in the brewer’s arsenal. Click To Tweet

Kettle souring is a legitimate process but some, me included, would argue for more clarity in the labelling of the beer. This can only be a good thing for consumers and for the wider adoption of sour beers.

Where do you stand on kettle souring? Is it cheating or just another way of making beer? And should it be made clear on the packaging or tap handle?

Leave a comment and let me know what you think.

Also, I don’t consider myself an expert on brewing sour beers so if you think I’ve made a mistake let me know.