Question

Why does a sugar solution with yeast powder become alcoholic in taste?

Answer 1

Hint: Yeasts are unicellular fungi that have the ability to undergo fermentation of glucose in the absence of oxygen. The product of fermentation is ethanol.

 Complete answer: Yeasts are single-celled fungi, which in sugar solution performs anaerobic breathing. They convert sugar present in the solution to ethanol. The odour occurs due to ethanol and results in \[C{{O}_{2}}\] alcohol production at the end of the reaction. It is also widely used in breweries and bakeries. It absorbs sugar and provides the by-products of its intake with warmth, \[C{{O}_{2}}\] and alcohol. The whole process that occurs in the absence of oxygen is called fermentation. Brewers of beer and wine use yeast to add alcohol to beverages. Yeasts not only make but also limit the quantity of alcohol in these beverages because above 18% by volume, alcohol becomes toxic to the yeast itself. Wine is produced by fermentation of the natural sugars present in grapes and other kinds of fruit. Beer, whiskey, and vodka are produced by fermentation of grain starches that have been converted to sugar by the enzyme amylase, and rum is produced by fermentation of sugarcane.

Note: Pasteur's findings showed that fermentation and yeast growth was occurred absolutely in the experimental conditions to verify his hypothesis. He realised that fermentation was a result of leaven multiplication and that the yeast had to stay alive to produce alcohol. In an early article in 1857 and in a concluding edition in 1860, Pasteur published his essential findings with the name "Mémoire Sur la fermentation alcoolique" which means "Memory for alcoholic fermentation."