fermentation is a process in which glucose is broken down to ethanol and carbon dioxide by the action of enzymes present in yeast.
for fermentation:
* suitable grain or fruit is mashed up with water
* yeast is added
* air is excluded, and
* the mixture is kept at about blood temperature, 37C
enzymes (biological catalysts) in the mixture first convert any starch or sucrose in the mixture into glucose and/or fructose, then other enzymes convert glucose or fructose into ethanol and carbon dioxide.
yeast (goes above the arrow)
C6H12O6(aq) -----------> 2CH3--CH2--OH(aq) + 2CO2(g)
bubbles of carbon dioxide are slowly given off: hence the name, fermentation. yeast can produce ethanol contents up to about 15%. alcohol concentrations above this level kill the yeast and stop further fermentation. to produce higher alcohol concents, it is necessary to distil the liquid.
