Accelerated processing of beer

This chapter provides an overview of accelerated processing of beer. Lagering is the most time-consuming part of the brewing process; it consists of secondary fermentation, maturation and stabilization. Secondary fermentation refers to the process following the main fermentation in which most of the yeast is removed from the beer. At this stage, there are some fermentable carbohydrates present and the aim is to reduce undesirable flavor compounds to acceptable levels. Maturation is a process in which no utilization of carbohydrates occurs. During stabilization, haze-forming materials are removed from beer so that it has the desired shelf-life. In a modern cylindroconical fermentation vessel brewery, the distinction between these processes is somewhat difficult to determine. The chapter presents the properties of beer after the main fermentation and after the secondary fermentation. The aims of traditional lagering are natural carbonation of beer, precipitation of haze-forming complexes, sedimentation of yeast, stripping of unwanted volatiles, reduction of aldehydes and ketones, release of amino acids, phosphates, fatty acids and sulfur compounds from yeast and “marriage” of all remaining components to create a good mouth feel. During lagering, many undesirable flavor and aroma compounds are reduced to acceptable levels. The most critical of these compounds is diacetyl. There are many reactions known to take place during lagering other than those related to diacetyl reduction.