CC - There is a lot of confusion out there as to what makes a beer a "wild ale." Can you help clear that up?
MM - Probably not! Brewers and consumers will be disagreeing about this specific terminology for a long time. I like to define wild beers in simpler terms, so to me, a wild ale is a beer that is fermented, at least in part, by yeast that does not belong to the genus Saccharomyces. This definition is more broad and encompassing than what some other brewers ascribe to, but I think the flavor of the beer should be the defining factor that differentiates wild beer from other beer styles. Brettanomyces is the most common type of yeast used in the production of wild beers, but other less common yeast strains are sometimes used as well and bacteria may or may not be included. I think it is important to differentiate wild beers from spontaneous beers. I would argue that all so-called spontaneous beers (particularly those that use a koelschip - like traditional lambic) are wild beer, but not all wild beer is spontaneous. Surprising to some, Lambic is not a product of 100% spontaneous fermentation. Lambic brewers achieve reasonable consistency not just from blending their beers, but also from reusing established barrels that act as an inoculant, delivering some of the same strains of yeast and bacteria into the ferment. Some brewers define a "wild ale" as a beer that is fermented with microbes not cultured in a lab; while I would certainly say that such a beer could be considered a "wild ale", I think the definition is too limiting. I reuse my strains and store them in my 'lab fridge' but I wouldn't say the strains become any less wild after I harvest them, propagate them, and then use them in another ferment. The definition of a "wild ale" with regard to process is something brewers will continue to disagree about - to me it is easier to recognize a wild ale when I taste it. There are a host of flavors produced in wild ales that simply cannot be produced in typical beers that are fermented with Saccharomyces.
CC - What is being referred to as a sour? Is every wild ale a "sour"?
MM - Absolutely not. In my opinion, wild ales do not need to have bacteria, though there are many wild ales that do in addition to non-Saccharomyces yeast. Brettanomyces produces very small amounts of acetic acid, but not typically enough to make a beer taste sour. I make farmhouse IPAs and 100% brettanomyces fermented beers that are usually very hoppy. The hops in these beers prevent any significant amount of acidity from developing, even if Lactobacillus and Pediococcus are present, as is the case for the mixed culture I use in my farmhouse IPAs. These beers typically have a pH of about 4.1-4.2 (4.3-4.8 is more common in normal ales and lagers) and they have a slight amount of tartness, but they are far more bitter than tart.
To me, sour is a tactile quality. Yes, it is one of the four basic tastes, but it has more implications for mouthfeel than flavor. I don't want people to refer to my beers as 'sours'. They are so much more than that. Calling them 'sours' seems to imply that acidity is the end goal. I make beers that highlight the various flavors produced by the non-conventional yeast known as Brettanomyces. Many of my beers have some degree of acidity and some of my beers are quite tart, but the acidity present in my beer plays a supporting role to balance unique flavors and create structure. Making a nuanced, subtle, balanced, and complex beer is always my end goal; making the most sour beer possible is as futile as trying to make the most bitter IPA or the sweetest milk stout.
There are some beers out there that have acidity, usually from Lactobacillus bacteria, yet do not contain any non-saccharomyces yeast. These beers are typically (but not always) produced with a process known as "kettle souring." I think these beers are quite boring and one-dimensional, and I'm not sure what they should be called. Perhaps calling these beers 'sours' would be appropriate, since they are not wild and acidity is often the main goal in producing these styles.
CC - I'd like to clear up the difference between Lacto and Brett. What different flavors are achieved by their use and what effects do they have on the beer?
MM - Lacto and Brett are completely different. Lactobacillus is a type of bacteria, while Brettanomyces is a type of yeast. Genetically speaking, that is very significant because the genome for Brett is about 10 times larger than Lacto. From a fermentation standpoint. that means that Brett can produce far more flavor compounds in the form of esters, phenols, and different types of organic acids. Lax strains differ in their production of types of organic acids and minimal esters, but Lacto mainly produces lactic acid, which is responsible for lowering the pH and increasing the sensation of acidity. Lacto is generally a quick fermenter, prefers simple sugars, and cannot ferment a beer to completion on its own. Brett can be a very slow fermenter and can ferment larger more complex sugars for up to a few years, often consuming all sugar in a beer. If you want to make a low carb beer, Brett would be an excellent yeast and would certainly result in a beer with far more character than the typical American light lager!
There is more genetic diversity among different species and different strains of Brett than among different strains of Lacto. I'm currently working with 16 different strains of Brett, some of them incredibly different. Some produce very fruity, tropical flavors; those tend to be my favorite strains. However, some produce interesting aromatics and flavors like cherry pie, wet hay, musty lemon, barnyard, and smoke - those flavors can work nicely when balanced with less assertive flavors. However, it is important note that there has been limited research on Brett and Lacto with respect to their flavor implications in beer, and my experience is anecdotal. Most research on these microbes has been focused on preventing their inclusion in products from large breweries and wineries where they are viewed as spoilage microorganisms. Coaxing different strains of non-traditional yeast and bacteria to produce unique and unusual flavors is one of my goals at Odd Breed, and it is from that goal that we define our beers as a product of Flavor from Fermentation.