Question

The bread or idli dough rises because of
(i) heat (ii) grinding (iii) growth of yeast cells (iv) kneading

NCERT Class VIII
Science - Main Course Book

Chapter 2. Microorganisms: Friend and Foe

Answer 1

(iii)growth of yeasts is the answer.......

Answer 2

The bread or idli dough rises because of the 'growth of yeast cells'.  

Option (iii)

Explanation:  

• 'Yeast is a 'fundamental component' for making bread and other savory baked goods. Yeast is added to warm water, where yeast reproduces and builds a colony.
• They use the 'sugars present' in the bread and secretes a liquid along with carbon dioxide as well as ethyl alcohol. The gas and alcohol help in rising the bread. The bread becomes 'very soft and fluffy' as a result.
• When the bread is baked, the alcohol evaporates off and the resultant bread tastes fine.