Basic for good fermentation

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

Brief history of yeast

• Pasteur: yeast=living microorganism. creation of bio+chemistry(mid 19th)
• Emil Hansen: isolate lager yeast, how to store them longer(1883)
• why lager popular?

1. longer shelf life=larger distribution area=increase sale=brewers love it
2. fist clean-tasting beer to mass

• what is hot side(cooking, in brewhouse)&cold side(cooling, pitching, fermenting)

For good fermentation?

• yeast
• sugar: 

1. high in glucose=higher esters
2. high in maltose(<-rice or corn)=lower esters
3. esters? 'ethyl acetate(tastes like adhesive, solvent)' 'isoamyl acetate(tastes like banana)' 

adhisive

• oxygen: 8~10 ppm at least, high yeast demand(lager, high gravity) beer require more oxygen
• nutrients
• fermentation system: 

1. large, open=harvest yeast for many generations but difficult to clean and sanitize 
2. cone-shaped=clean-in-place, temperature control but tall fermentor->pressure of gases↑->stress on yeast

• temperature control: problem but not contamination?->look temperature

1. temperature can affect: off-flavor pre-cursors and yeast's ability to reduce off-flavor compounds(at the end of fermentation)

• fermentor monitoring: main measurements are 

1. temperature
2. specific gravity
3. pH
4. oxygen
5. carbon dioxide
6. + how much yeast pitched, its source, its viability, beer volume, daily progress