Yeast and Fermentation
What microorganism is primarily responsible for converting sugars into alcohol in beer?
YEAST!!
What main flavor do hops add to beer?
Bitterness
Barley!
What phase change occurs during boiling that helps sterilize wort?
BOILING
liquid-> vapor
Dark beer is always higher in alcohol
MYTH
What two main products are formed when yeast ferments glucose anaerobically?
Ethanol and carbon dioxide!
When are hops added if you want aroma instead of bitterness?
Late in the boil or after boiling (dry hopping)
What enzyme breaks starch into fermentable sugars during mashing?
Amylase!
Convection!
Cold temperatures slow down yeast metabolism
SCIENCE
Ale yeast and lager yeast differ mainly in what fermentation characteristic?
Temperature! Ales warm, and lagers cold
What happens if hops are boiled for a long time?
Which sugar is most readily fermented by yeast: glucose, maltose, or dextrin?
Glucose!
why does rapid cooling reduce contmaination risk?
Less time in the microbial "danger zone"
Skunky beer comes form oxygen exposure
MYTH (light exposure is actually the culprit)
What metabolic pathway do yeast use to convert glucose into ethanol?
Glycolysis followed by alchoholic fermentation
Why does boiling hops longer increase bitterness?
a) More hop sugar ferments
b) Heat changes hop compounds into bitter ones
c) Hops dissolve better in alcohol
d) Yeast activates hop enzymes
Lower mash temperatures tend to produce what type of beer?
A) Sweeter
B) Drier
C) Sour
D) Stronger
Drier
They are volatile and evaporate!
Higher mash temperatures lead to sweeter beer
Science!
What compund produce by stressed yeast is responsible for "banana" flavors in some beers?
A) Diacetyl
B) Isoamyl acetate
C) Acetaldehyde
D) Methanol
B) Isoamyl acetate (an ester)
Why do green bottles protect beer better than clear ones?
They block light that causes skunky flavors
What type of sugar is largely unfermentable and contributes to body and mouthfeel?
Dextrins!
What thermodynamic principle explains why fermentation generates heat?
Exothermic reactions
Beer foam ("head") has no impact on flavor or aroma
Myth