Brew Chem 101

Homebrew Talk - Beer, Wine, Mead, & Cider Brewing Discussion Forum

Help Support Homebrew Talk - Beer, Wine, Mead, & Cider Brewing Discussion Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.


Maniacally Malty
HBT Supporter
Apr 9, 2007
Reaction score
Oakland, CA
This is what i've learned so far by reading Brew Chem 101 by Lee W. Janson

only about 1/3 finished with the book so far. it's pretty informative on certain things...most of this stuff i already knew in limited depth, but it gives me much more detail into the WHY of homebrewing practices.

Please feel free to correct me if i am misunderstanding any of this. Any correspondence would be welcome...this is a very interesting book and subject in general!

1. Preparation stage = yeast acclimating to their environment (lag)
1a. Aerobic respiration = reproductive stage (aerobic = w/oxygen) - during this time sugar and oxygen is consumed and co2 is produced, but no alcohol is produced.
1b. Anaerobic respiration = fermentation (anaerobic = w/o oxygen) - reproduction still occurs - interesting: one molecule of co2 is produced for every molecule of ethanol

2. Noble hops have less cohumulone hydrocarbons and higher humulene giving them a more elegant, refined taste and odor. All the hops i like (saaz, tettnanger, fuggle, hallertau, e.k. golding) are noble hops :)
2a. Because they have less cohumulone, however, you have to use more for bittering and often other hops should be used for this addition...taste will not necessarily be adversely affected by using the higher alpha acids (which is mostly a reading of cohumulone in home brewing) to obtain bitterness.
2b. oxidation affects these flavors and aromas greatly, so they die faster over time (interesting)

3. The major (and the only truly discernible) difference between ale yeast and lager yeast is that ale yeast do not completely digest the sugar raffinose. although there are old terms used (ale = top-fermenting, warm temperatures, lager = bottom-fermenting, lower temps) it is not necessarily true as there are many different and hybrid strains.

4. Amylose, amylopectin & starch are broken down during mashing and boiling to create 1-3 glucose molecules, which are the only sugars that yeast can break down. any residual "starches" (normaly improper term in chemistry for first 3 mentioned) give the malty flavour to beers. this is why some beers are mashed at lower temperatures...there is a higher conversion rate and results in a more fermentable wort leaving less starches and less maltiness.

5. lipids are the reason leaving beer on the trub is so controversial. they contribute flavour, but can also give a soapy taste or ruin the head if they are on the beer too long. (from experience i'd say the flavour they contribute greatly outweighs their perceived drawbacks)

More to come as I read on!


Latest posts