Assertion (A): The dough, which is used for making foods such as dosa and idli is fermented by bacteria.
Reason (R): Micro-organisms such as Lactobacillus grow in milk and convert it to curd.
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → The assertion (A) and reason (R) both are true but reason is not the correct explanation of assertion.
Assertion (A): The dough, which is used for making foods such as dosa and idli is fermented by bacteria. — True. NCERT states that the dough for dosa and idli is fermented by bacteria. The CO2 released during this fermentation gives the dough its puffed-up look.
Reason (R): Micro-organisms such as Lactobacillus grow in milk and convert it to curd. — True. Lactobacillus and other lactic acid bacteria (LAB) grow in milk, and the acids they make coagulate and partially digest the milk proteins, turning milk into curd.
A is about the fermentation of dosa and idli dough. R is about the making of curd from milk.
Why R does not explain A? Both are examples of microbes used in household products, but they describe two separate processes with different starting materials. The fact that LAB turn milk into curd does not tell us why the dough for dosa and idli ferments, so R cannot be the reason for A. Both statements are true, but R is not the correct explanation of A.
NCERT Extract:
Microbes in Household Products – “… A common example is the production of curd from milk. Micro-organisms such as Lactobacillus and others commonly called lactic acid bacteria (LAB) grow in milk and convert it to curd. During growth, the LAB produce acids that coagulate and partially digest the milk proteins. … The dough, which is used for making foods such as dosa and idli is also fermented by bacteria. The puffed-up appearance of dough is due to the production of CO2 gas.”