Chemistry Reference
In-Depth Information
8
Brewing with enzymes
Eoin Lalor and Declan Goode
8.1
INTRODUCTION
The principal raw materials that are needed to brew beer are water, malted barley, adjuncts
(barley, maize, rice, wheat and sorghum), hops and yeast. The brewing process involves
extracting and breaking down the carbohydrate and protein from malted barley and adjunct
sources. This results in a carbohydrate/protein-rich solution that can be used as a source of
nutrients for yeast fermentation.
The major biological changes that occur in this process are catalyzed by naturally produced
enzymes from the barley and yeast, respectively. Barley that has been malted has all the
necessary enzymes needed to degrade starch, β-glucans, pentosans, lipids and proteins,
which are the major components of interest to the brewer.
When poor quality malt or high levels of adjunct material are used in the process, then
the addition of commercial enzymes is necessary. Commercial enzymes give the brewer
the freedom to use cheaper, poorer quality raw materials, to enhance process yields and to
enhance the quality characteristics of the final beer.
The aim of this chapter is to provide the reader with a step-by-step overview of the main
enzyme-dictated steps involved in the beer production process (Table 8.1) from the malting
of barley grain through to the final stabilization of the beer in the package. The reader is
referred to broader brewing texts
1-3
for further explanations of the science and technology
behind each step.
8.2
MALTING: THE TRANSFORMATION OF RAW BARLEY
TO AN ENZYME-RICH PACKAGE
Raw barley cannot be used for brewing in its native form without (1) malting (the controlled
germination of the grain, to stimulate endogenous enzyme production) or (2) the intervention
of added exogenous enzymes. This section will focus primarily on the malting processes.
The malting process mimics the natural germination of barleycorns which would otherwise
happen in the field but with two significant differences (1) growing conditions are manipulated
to encourage enzyme production by the aleurone, while minimizing yield losses due to
respiration and growth of the embryo and (2) the germinated corn is gently kilned to preserve
enzymatic activities where possible.
The purpose of malting is to activate the endogenous phytohormones and enzymes of the
barley to make it more amenable to starch/carbohydrate extraction, which is further facilitated
