Fermentation timeline

from <Yeast: the practical guide to beer fermentation(White and Zainasheff, 2010)>

Fermentation timeline

• pitch yeast: sugar+2ADP+2phosphates->2ethanol+2CO2+2ATP
• lag: 0~15hrs
• exponential growth: 4hrs~4d
• stationary 3~10d
• what the yeast gain from fermentation?&what they do for the beer?

Lag phase

• building new healthy yeasts for fermentation
• cell<=oxygen(from outside), mineral, amino acid(=nitrogen->protein)(from wort)
• vitamin: riboflavin, inositol, biotin
• mineral: phosphorus, sulfur, copper, iron, zinc, potassium, sodium
• vitamin+mineral=enzymes for growth
• not add oxygen later but for high gravity/alcohol beer
• temperature warmer? precursors for diacetyl produced
• 22~24'c->20'c or 22~24'c->10~13'c(for lager)
• below 22~24'c+12~36hrs raising temperature: for cleaner beer, healthy yeast

Exponential phase

• phase for yeast growth
• growth+produce CO2+{ethanol+flavo compounds}
• olive smell!
• consume sugar

1. simple(glucose, fructose, sucrose)sugar: metabolism quicker!
2. maltose(59%, cf. glucose 14%)+maltase->glucose: beer flavors
3. maltotriose: determine attenuation power. better digest+less flocculent

• form color yellow to brown

Stationary phase(Conditioning phase)

• growth slow down, matures
• green beer(young beer)
• reabsorb diacetyl, acetaldehyde
• hydrogen sulfide escape as a gas
• if new strain... check if complete!: rousing? raising the temperature? repitching?
• temperature down to 2~4'c to floc settle down(in a professional brewery)
• rush the process?->diacetyl remain! +warmth&time to complete