Lacto and Pedio, not a new fad diet


Sour beer has been a burgeoning star in the world of craft beer, but the details of how it is made, or even what causes different flavors in sour beer is widely unknown to the drinking public.

There was a time in the long distant past (say, 20 years ago) when the average drinker didn’t know that hops were a plant, much less an ingredient in beer. Now I have to listen to some stockbroker at the local 50+ tap beer bar tell me all about how Cascade hops give a beer that grapefruit flavor (really? you don’t say).

I guess I really shouldn’t complain, the average beer consumer is as educated now as the geekiest of beer geeks was back in the day. It’s a victory for the craft that so many people have this knowledge now, but it also makes me appreciate the eye rolling people gave me when I first learned about beer, and wanted to tell every person I met.

However sour beer is a new frontier. Governed by forces that are as mysterious as they are fundamental, these beers defy any traditional  definition of what beer is (in America anyway). Funky, tart, fruity, tannic, champagne-like, these beers are clearly miles away from the IPAs everyone has come to know and love. And what makes these beers what they are is as misunderstood as much as it is unknown by Joe Six-pack.


One of the major contributors to making sour beer sour is brettanomyces, which I touched on here. But there are two other players that are often along for the ride with brett, and those are lactobacillus and pediococcus. Lacto and Pedio for short.

Both pedio and lacto are bacteria that, in sour beer, produce acidity. This is typically what most drinkers refer to as “sour,” but should more specifically be defined as “acidic” or “tart.” Pedio is a slow metabolizer, and can produce some harsher types of acidity in beer. It can also produce some off flavor compounds, such as diacetyl, which has a buttery/butterscotch note. Pedio, like brett, can continue to develop more complex acidity and flavors over time (6-12 months). Pedio is almost always found in conjunction with brett and lacto, and rarely on it’s own.

Lacto produces a much cleaner acidity, leaving very few off flavors when used on it’s own. It’s very fast working but is not alcohol tolerant, so when the beer gets above 3% to 4% alcohol by volume, the bacteria tends to die off. Lacto is also extremely sensitive to hops, so typically a lacto beer will have little to no hops at all in it. This is the bacteria primarily used in the production of gose or berlinerweisse, which are very tart and low in alcohol. Unlike pedio and brett, lacto doesn’t usually develop over time.


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