Lesson 5 - Types of microorganisms SAQ

**Wild ales refer to mixed fermentation beers that are fermented with microorganisms other than brewing yeast. If you were to brew a wild ale, which microorganisms would you consider using and why?

Response:

Modern wild ales are influenced by European sour ales such as Flanders Red Ale, Oud Bruin, Berliner Weisse, and lambic, and are specific in that microorganisms are deliberately introduced rather than occurring spontaneously.

The organisms used are bacterial or fungal in origin and produce the characteristic sourness and wild yeast flavours.

Bacteria used are genera of the Gram-positive lactic acid bacteria (LAB) Lactobacillus and Pediococcus. Lactobacillus produces lactic acid and can be used in the mash or kettle (kettle souring), or pitched with yeast.

Pediococcus inoculation is carried out in secondary fermentation. Excessive growth can result in ropiness in beer so its use needs to be carefully controlled. It is used to produce sourness and diacetyl.

Wild yeasts, both the Saccharomyces and non-Saccharomyces strains, are used to alter flavour. Brettanomyces is most commonly used for its ability to produce ‘barnyard’ flavour, which includes the volatile phenols 4-ethylguaiacol and 4-ethylphenol. In some strains high ester production is also a characteristic.

Torulaspora delbrueckii, another yeast species sometimes used in mixed-culture wild beer fermentations, is a high ester producer adding fruitiness to the style.