Simple sugars Ethanol + CO2 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 C3H3O3 C2H4O3 + CO2 C2H6O glucose pyruvate 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 Diacetyl *some are good, some are not so good CO2

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 Want Esters: Most Ales Hefewiesen beers Belgian ales We Do Not Want Esters: Lagers Unwanted esters can arise 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)

Increasing ESTERS in your beer/spirits: 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 T’s 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:

Its all about ENERGY Why do we oxygenate our wort? [No O2] 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 C3H3O3 C2H4O3 + CO2 C2H6O glucose pyruvate acetaldehyde ethanol

Fermentation Chemistry Lecture One: Fermentation Basics