Question

Explain the process of fermentation of alcoholic beverages like beer and wine.

Answer 1

Alcoholic beverages are produced when yeast, usually Saccharomyces cerevisiae, ferments sugars in the absence of oxygen, forming ethanol and carbon dioxide.

Beer

1. Barley grains are soaked and allowed to germinate; the germinated grains are dried in a process called malting.
2. The malted grains are crushed and mixed with warm water. Enzymes convert their starch into sugars, producing a sugary liquid called wort.
3. The wort is filtered and boiled, then yeast is added. Fermentation converts the sugars into ethanol and carbon dioxide.
4. The beer is filtered, pasteurised and bottled without distillation.

Wine

1. Grapes are crushed to obtain sugar-rich juice.
2. Yeast is added to ferment the grape sugars into ethanol and carbon dioxide.
3. The wine is transferred to barrels and bottled. Its variety depends on the grapes and processing; red wine is commonly made with the grape skins left in the juice, while white wine is made after the skins are removed.

Beer uses barley as its sugar source, whereas wine uses grape juice.