Plants & Human Affairs - Introduction

Plants & Human Affairs (BIOL106) - Stephen G. Saupe, Ph.D.; Biology Department, College of St. Benedict/St. John's University, Collegeville, MN 56321; ssaupe@csbsju.edu; http://www.employees.csbsju.edu/ssaupe

Quick Overview of Beermaking

Step 1. Malting
The function of this step is to induce hydrolytic (digestive) enzymes that breakdown the starches in the grains to fermentable (simple) sugars like glucose.

Steps in the malting process are: barley → cleaned → soak → germinate (rotating drums) → dry in kiln (raise temp to about 180 F) → grind → screen → malt
Malt - gets its name from the maltose (one of products of enzyme breakdown of starch)
Preparation of malt will determine flavor of beer. For example, stouts use malt that is caramelized
barley may be treated with gibberellic acid to insure uniform germination

Step 2. Mashing.
The purpose of this step is to convert starch to simple (fermentable) sugar

Malt + water + adjuncts (other materials, i.e., rice & corn added to US beers) → enzymes continue to convert starch into fermentable sugar → spent grain removed feed to animals; liquid → wort

Step 3. Brewing
The function of this step is to convert sugars into alcohol (and other flavor components)

wort + hops (related to marijuana; use the female flowers; provides flavor, disguises sweetness from sugars in the beer; stops enzyme action, precipitates proteins, antimicrobial action) → boil (stops enzyme action, extracts flavor, sterilizes) → spent hops removed (used for fertilizer) → add yeast to liquid → brew 5-12 days
Saccharomyces cerevisae - ales top fermented (yeast floats), higher alcohol content, higher hops, paler color; lagers bottom fermented (yeast sinks).
The purpose of the yeast is to convert sugars to carbon dioxide and alcohol and to impart flavor from other metabolic products.

Step 4. Lagering
This is the aging and maturing step.

Beer is aged from 14 days to 3+ months.
The yeast is removed → transferred to lagering tanks where the proteins settle out and flavor improves → carbonated → pasteurized → bottled
Carbonation can be done by: (a) adding beechwood chips and green beer to stimulate a final yeast growth (krausening); (b) introduce CO2 under pressure.