Fermentation Chemistry Lecture One: Fermentation Basics What is

Fermentation Chemistry Lecture One: Fermentation Basics What is Fermentation? Alcohol Fermentation is the chemical conversion of simple sugars (like glucose) to ethanol and carbon dioxide (CO2) Yeast perform the fermentation chemical reactions Fermentation pathway: Anaerobic (oxygen is not needed) The primary method yeast acquire energy for living

Simple sugars Ethanol + CO2 Fermentation Chemistry Lecture One: Fermentation Basics 2 types of FERMENTATION: 1. Alcohol Fermentation: performed by yeast and bacteria

2. Lactic Acid Fermentation: performed by animals like us (not pertinent to brewing) Fermentation Chemistry Lecture One: Fermentation Basics When does Fermentation occur? After WORT COOLING Yeast is added to the cooled wort Where does Fermentation occur?

In the FERMENTATION TANK Fermentation Chemistry Lecture One: Fermentation Basics What is the chemical reaction process of alcohol fermentation? C6H12O6 glucose C2H 6O C3H3O3

pyruvate C2H4O3 + CO2 acetaldehyde ethanol Fermentation Chemistry Lecture One: Fermentation Basics Are there other chemicals or compounds that yeast produce during alcohol fermentation, other than ethanol and CO2?

YES. Up to over 600 others!! Including: Esters Fusel (higher)alcohols Phenols CO2 Diacetyl *some are good, some are not so good

Fermentation Chemistry Lecture One: Fermentation Basics ESTERS: Esters are the most common/important flavor chemical that brewing yeast produce Esters are typically fruity in flavor and produced more by Ale Yeasts Sometimes we want them, other times not; depending on the beer style We Do Not Want Esters:

We Want Esters: Lagers Most Ales Hefewiesen beers Unwanted esters can arise Belgian ales from: Contaminated beer from bacteria Too high Fermentation T

Fermentation Chemistry Lecture One: Fermentation Basics ESTERS: Fermentation Chemistry Lecture One: Fermentation Basics ESTERS: Fermentation Chemistry Lecture One: Fermentation Basics ESTERS in DISTILLING FERMENTATION:

ethyl acetate nail polish remover, model paint and glue isoamyl acetate pear, banana all others are a potential (see Ester List) Fermentation Chemistry Lecture One: Fermentation Basics Increasing ESTERS in your beer/spirits: 1. Choose ester-producing ale yeast 2. Under pitch your yeast 3. Increase Fermentation T

4. Under oxygenate at pitching Fermentation Chemistry Lecture One: Fermentation Basics FUSEL ALCOHOLS: Definition: alcohol with 3+ carbons Fusel alcohols are formed from pyruvate and too high fermentation Ts Taste profile: jet fuel Issue: a major cause of hangover headaches

Fermentation Chemistry Lecture One: Fermentation Basics FUSEL (Higher) ALCOHOLS: Fermentation Chemistry Lecture One: Fermentation Basics PHENOLS: Phenols are produced from pyruvate in the fermentation pathway Flavor profile: clove, medicinal, band-aide, smokey Phenols can be wanted or unwanted, depending on the beer style Phenols and beer styles:

Belgian ales German hefeweisens Wheat beers Rauchbier Fermentation Chemistry Lecture One: Fermentation Basics PHENOLS: Smokiness Of Scotch Source in scotch whiskey: PEATED MALTS

Fermentation Chemistry Lecture One: Fermentation Basics PHENOLS: Phenols Fermentation Chemistry Lecture One: Fermentation Basics DIACETYL: Diacetyl arise from pyruvate in the fermentation pathway Typically, you NEVER want diacetyl

Flavor profile: buttery, butterscotch, buttered popcorn Yeasts naturally produce diacetyl and will reabsorb it, given a little time: the diacetyl rest Too high Fermentation Temperature will also produce too much diacetyl Fermentation Chemistry Lecture One: Fermentation Basics DIACETYL:

Fermentation Chemistry Lecture One: Fermentation Basics Why do we oxygenate our wort? Anaerobic Fermentation v. Aerobic Cellular Respiration Its all about ENERGY [No O2] C6H12O6

glucose C3H3O3 pyruvate C2H4O3 + CO2 acetaldehyde ethanol

C2H6O Fermentation Chemistry Lecture One: Fermentation Basics

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