Changes

Beer or wort can be inoculated with commercial sour beer that is not pasteurized. Generally, only the last half inch of a bottle's contents, including the sediment, is used. This portion of the beer is often referred to as "the bottle dregs". It is recommended that the microbes in this the beer are first reinvigorated with a small starter wort of around 1.030 gravity before it is added to the fermentation vessel. Using commercial sour beers to ferment is generally a good idea because the microbes are often stronger and more aggressive from commercial breweries as compared to mixed cultures from yeast companies (this is a generalization). It is generally advised to use as fresh of a bottle of commercial sour beer as possible, however older bottles can be used as well depending on the brewery, beer, and how the bottle was stored.