Zusammenfassung der Ressource
Fermentation
- It is a process
used to produce
alcohol e.g. beer
and wine. The
microbe used is
yeast
- Main stages of fermenting yeast
- 1. Extract sugar
- 2. Add yeast
- 3. Adjust temperature for yeast growth
- 4. Ferment mixture into airtight container to
prevent entry of air and microorganisms
- 5. Clarify beer (makes yeast settle)
- 6. Draw out the alcohol
- 7. Pasteurise and bottle the beer
- The breakdown of sugar by yeast in the absence of oxygen =
anaerobic respiration
- sugar -> ethanol + carbon dioxide + energy
- C6H12O6 -> 2C2H5OH +2CO2
- If oxygen is present = aerobic respiration
- sugar + oxygen -> water + carbon dioxide
- Yeast and Alcohol
- Different strains of
yeast give alcohol
different flavours
and strengths
- Usually the high
concentration of
alcohol produced
by the yeast cells
kills them making
the drink safe for
humans
- Yeast that can
tolerate high levels
of alcohol are used
to produce drinks
with a higher alcohol
content e.g. vodka
- Effect of temperature on yeast
- For every 10 degree celcius rise, the yeast doubles
- Until it reaches the optimum and then the yeast decreases
- This is because the enzymes are denaturing