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 ID: 697684
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Fermentation ChemistryLecture 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 + CO2Slide2
Fermentation ChemistryLecture One: Fermentation Basics
2 types of FERMENTATION:
1. Alcohol Fermentation: performed by yeast and bacteria2. Lactic Acid Fermentation: performed by animals like us (not pertinent to brewing)Slide3
Fermentation ChemistryLecture One: Fermentation Basics
When does Fermentation occur?
After WORT COOLINGYeast is added to the cooled wortWhere does Fermentation occur?In the FERMENTATION TANKSlide4
Fermentation ChemistryLecture One: Fermentation Basics
What is the chemical reaction process of
alcohol fermentation?C6H12O6 C3H3O3 C2H4O3 + CO2 C2H6O
glucose
pyruvate
acetaldehyde
ethanolSlide5
Fermentation ChemistryLecture 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
CO2Slide6
Fermentation ChemistryLecture 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: LagersUnwanted esters
can arise from: Contaminated beer from bacteria Too high Fermentation T Slide7
Fermentation ChemistryLecture One: Fermentation Basics
ESTERS:
Slide8
Fermentation ChemistryLecture One: Fermentation Basics
ESTERS:
Slide9
Fermentation ChemistryLecture 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) Slide10
Fermentation ChemistryLecture 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 Slide11
Fermentation ChemistryLecture 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 Slide12
Fermentation ChemistryLecture One: Fermentation Basics
FUSEL (Higher) ALCOHOLS:
Slide13
Fermentation ChemistryLecture 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 Slide14
Fermentation ChemistryLecture One: Fermentation Basics
PHENOLS:
Smokiness Of ScotchSource in scotch whiskey: PEATED MALTS Slide15
Fermentation ChemistryLecture One: Fermentation Basics
PHENOLS:
PhenolsSlide16
Fermentation ChemistryLecture 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 Slide17
Fermentation ChemistryLecture One: Fermentation Basics
DIACETYL:
Slide18
Fermentation ChemistryLecture One: Fermentation Basics
Why do
we oxygenate our wort?Anaerobic Fermentation v. Aerobic Cellular Respiration
C6H
12O6 C3H3
O3 C2H4O3 +
CO2 C
2
H
6
O
glucose
pyruvate
acetaldehyde
ethanol
[No O
2
]
Its all about ENERGYSlide19
Fermentation ChemistryLecture One: Fermentation Basics