Lesson 4 - Types of Microorganisms
In this lesson we cover organisms that occur in beer besides pitching yeast. Firstly, we look at speciality organisms involved in making traditional Belgian and wild beer styles. We then cover the spoilage bacteria, classified as Gram-positive and Gram-negative. Finally, we cover the wild yeasts as contaminants of beer processing and finished product.
Preface
We can find many microorganisms within the brewery. They come from the environment and raw materials or, in some instances, are deliberately introduced. In this lesson, we take a close look at them.
Microorganisms are literally everywhere in the brewery; in the water, in the air, on surfaces, on our raw materials, and on our people. Many are innocuous, finding the environment of the brewing process too hostile for proliferation. But some can and do cause spoilage at various stages in the process, sometimes leading to the point where the product is deemed unacceptable and we need to destroy it. Even worse, some products may spoil in trade, resulting in expensive recalls and serious damage to corporate reputation. In this lesson we look at the types of microorganisms found in the brewing process, categorise them, and understand how they can grow and what damage they can cause.
However, increasing consumer interest in beer with unusual characteristics has led some brewers to use some of these organisms – conventionally known as beer spoilers – to create new beers described as, for example, funky, wild, barnyard, horsey, sour, and indole (described as faecal). Although we would not normally associate these terms with mainstream brands, we might use them to describe some of the traditional beers produced in Belgium. We therefore begin this lesson with a look at the positive role that these microorganisms can play, as well as their usual negative connotations.