Equipment Glossary Acknowledgements


Site Map
Introduction
Section 1
Brewing Your First Beer With Malt Extract
1 A Crash Course in Brewing
2 Brewing Preparations
3 Malt Extract and Beer Kits
4 Water for Extract Brewing
5 Hops
6 Yeast
7 Boiling and Cooling
8 Fermentation
9 Fermenting Your First Beer
10 What is Different for Brewing Lager Beer?
11 Priming and Bottling
Section 2
Brewing Your First Extract and Specialty Grain Beer
Section 3
Brewing Your First All-Grain Beer
Section 4
Formulating Recipes and Solutions

 

 

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Chapter 8 - Fermentation

8.3 Conditioning Processes

The conditioning process is a function of the yeast. The vigorous, primary stage is over, the majority of the wort sugars have been converted to alcohol, and a lot of the yeast are going dormant; but there is still yeast activity. During the earlier phases, many different compounds were produced by the yeast in addition to ethanol and CO2, e.g., acetaldehyde, esters, amino acids, ketones- diacetyl, pentanedione, dimethyl sulfide, etc. Once the easy food is gone, the yeast start re-processing these by-products. Diacetyl and pentanedione are two ketones that have buttery and honey-like flavors. These compounds are considered flaws when present in large amounts and can cause flavor stability problems during storage. Acetaldehyde is an aldehyde that has a pronounced green apple smell and taste. It is an intermediate compound in the production of ethanol. The yeast reduce these compounds during the later stages of fermentation.

The yeast also produce an array of fusel alcohols during primary fermentation in addition to ethanol. Fusels are higher molecular weight alcohols that often give harsh solvent-like tastes to beer. During secondary fermentation, the yeast convert these alcohols to more pleasant tasting fruity esters. Warmer temperatures encourage ester production.

Towards the end of secondary fermentation, the suspended yeast flocculates (settles out) and the beer clears. High molecular weight proteins also settle out during this stage. Tannin/phenol compounds will bind with the proteins and also settle out, greatly smoothing the taste of the beer. This process can be helped by chilling the beer, very similar to the lagering process. In the case of ales, this process is referred to as Cold Conditioning, and is a popular practice at most brewpubs and microbreweries. Cold conditioning for a week clears the beer with or without the use of finings. Fining agents, such as isinglass (fish bladders), Polyclar (plastic dust), and gelatin, are added to the fermentor to help speed the flocculation process and promote the settling of haze forming proteins and tannins. While much of the emphasis on using finings is to combat aesthetic chill haze, the real benefit of dropping those compounds is to improve the taste and stability of the beer.

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Fermentation
8.0
Some Misconceptions
8.1
Factors for a Good Fermentation
8.1.1
Yeast Factors
8.1.2
Wort Factors
8.1.3
Temperature Factors
8.2
Re-defining Fermentation
8.2.1
Lagtime or Adaptation Phase
8.2.2
Primary or Attenuative Phase
8.2.3
Secondary or Conditioning Phase
8.3
Conditioning Processes
8.4
Using Secondary Fermentors
8.5
Secondary Fermentor vs. Bottle Conditioning
8.6
Summary
Real Beer Page

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Appendix A - Using Hydrometers
Appendix B - Brewing Metallurgy
Appendix C - Chillers
Appendix D - Building a Mash/Lauter Tun
Appendix E - Metric Conversions
Appendix F - Recommended Reading

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All material copyright 1999, John Palmer