The goal of this page is to welcome the new brewer to the world of sour beer and get started! This page looks at sour beer basics and what flavor progressions to expect along the fermentation timeline. We will (1) go over a few basics about sour beer, (2) look at how time affects wild beers, and (3) analyze some strategies for attaining certain flavor profiles. This page is targeted at the “beginner sour brewer", who shall be assumed as someone who has the basic “standard” brewing processes down and is interested in diversifying their fermentation process. Because this is an introductory page and links directly to the rest of the wiki, citations will be omitted.
Definitions within the sour beer world are difficult and complicated, but we will try and cover the basics here.
Sour beer is any beer inoculated with lactic acid bacteria, as well as any fermentative yeast such as ale or lager yeast or even Brettanomyces. Sour beer is most distinguished by the presence of lactic acid, which makes the beer taste sour. The yeast and bacteria can be sourced from many places, including lab cultures, microbes that come from nature or the environment around you, or bottle dregs from commercial sour beers.
A clean beer is any beer that is not sour, funky, or wild beer; in other words your typical ale or lager.
A funky beer is a term generally used by brewers to refer to beer that is fermented with Brettanomyces, but not lactic acid bacteria. There is a common misconception that Brettanomyces makes beer sour, but under normal brewing conditions it should not make beer sour. Brettanomyces does not make lactic acid, but it does make acetic acid, which tastes like vinegar. Brewers do their best to limit the amount of acetic acid that is made by Brettanomyces, which is controlled by limiting its exposure to oxygen.
A kettle sour beer is a beer that has been soured for a short time in a sanitary vessel (usually the boil kettle) and then boiled to kill the lactic acid bacteria, and then finally fermented as a normal beer. These types of beers generally do not contain Brettanomyces. This process has the benefits of creating a sour beer very quickly and greatly reducing any risk of infecting one's cold side brewing equipment (fermenters, hoses, packaging equipment, etc.). Kettle soured beer has the reputation of being less complex than other forms of sour beer.
A spontaneously fermented beer is a type of sour beer that has not been inoculated by any lab cultures but only by the yeast and bacteria present in the environment. This is the typical method used by the Belgian lambic brewers, but there are also many brewers in the rest of the world that have successfully created sour beer this way.
Other terms have been used by brewers and can refer to different things or have different definitions depending on who you're talking to. For example, the term wild beer is used by some to refer to spontaneously fermented beer, and others to refer to any sour beer or funky beer that isn't kettle soured.
A Brief Background of Yeast/Microbes
When brewing sour beer, there are a few more players to the “yeast” side of the ingredients list. In addition to Saccharomyces or “Sacch”, in wild beer brewing the brewer is often dealing with Brettanomyces, which is another genus of yeast, and Lactobacillus and Pediococcus, which are both bacteria. Acetobacter and enterobacter do play a part in some sour fermentations, however they are not often intentionally added.
There are two major species of Brettanomycesused in brewing: B. Bruxellensis and B. Anomala. Despite other strains mentioned, there are only five species of Brett, with these two being the species most commonly used in brewing. Brettanomyces produces what we will later refer to as the “funk” when it comes to wild beers. While it is capable of producing some acetic acid when in the presence of oxygen (think vinegar), funk is what is typically described. Despite providing desired funk and acetic acid, it is important to note that Brettanomyces can also be responsible for less desired flavors: feet, hard boiled egg, and some solvent-like nail polish flavors. Pure commercial cultures of Brettanomyces are available at most yeast suppliers. Brettanomycesdoes NOT provide a universal flavor. Just like the various Saccharomyces strains most brewers are familiar with, each Brettanomyces strain can produce a vast array of different flavors, depending on the particular strain, temperature and time.
Lactobacillus is a rod shaped bacteria that can grow with or without oxygen and produces lactic acid - most people are familiar with the sourness found in yogurt, sauerkraut , pickles, and so on. Lactobacillus converts sugars to lactic acid (and sometimes CO2 and ethanol). It can produce varying complexities of sourness from the one dimensional to the more complex, depending on which type is used.
Pediococcus is a bacteria that also produces lactic acid, although generally slower than lactobacillus. The sourness tends to be thought of as more aggressive than Lactobacillusand is often thought to produce more of a complex sourness. It also produces off flavors (diacetyl) so it needs to have something to help clean up any unwanted flavors – like Brettanomyces, which converts it to other compounds with less aggressive flavors. There is some discussion that Pediococcus thought of “complexity” is merely perceived by brewers because it works longer than Lactobacillusdoes. This “complexity” could be simply because Pediococcus can lower the pH more than Lactobacillus.
Sourness vs. Funk
The flavors produced by some wild beers when using non-souring mechanisms are described as ‘funk’. Keep in mind that if you are choosing to use a wild yeast or bacteria, you want to have an idea of whether you’re looking for sourness or funk, and how much of each.
“Funk”, isn’t a common term for most of us in the food we eat. Descriptors of funk can be found in stinky blue/green cheeses, dank basements, some molds, and “on the farm.” When looking to achieve the funk, we’re going to be including Brettanomyces. When using Brettanomyces, we have two main species to pick from currently, and two very generalized flavor categories. B. Bruxellensis tends to produce a more funky beer, with emphasis on the “barnyard” characteristics Brett is commonly known for. Some flavor descriptors include horsey, smoky, spicy, barnyard, and the classic “sweaty horse blanket.” B. Anomala, on the other hand tends to lend fruity characteristics – pineapple, mango, and a low intensity “funk.” (although with time this can be more aggressive.) It is important to note Brettanomyces is capable of producing fruitier notes without the typical funk as well. However it can produce a lighter, fruitier funk that comes out as a delicate barnyard flavor with some varying notes of overripe tropical fruit.
Higher acid levels will give you sourness. Sourness is pretty easy to describe, as it is a flavor common to most of us in the acidic foods you keep in your fridge or pantry – lemons, limes, yogurt, sour patch kids, vinegar, etc. Most of us have probably tried sour foods with different levels of sourness and complexity from acidic fruit to lactic fermented vegetables. When we say complex, we're talking about layered acidity. Imagine drinking lime juice as simple sourness. A complex sourness would be lemon, lime, grapefruit, and pineapple juice combined.