Question

4. Give scientific reasons.
a. Foam accumulates on a the surface
of 'dal' kept for a long time in
summer.​

Answer 1

Answer:

In summer, the atmospheric temperature is favourable for microbial growth. Foodstuffs like 'dal' which kept open for a long time favours the growth of microbes. The microbes release various gases as byproduct and these gases form foam on the surface of foodstuffs having more water content.

Explanation:

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Answer 2

Answer:

During summer months, the surroundings temperature and humidity is conductive for the growth of bacteria and fungi. These favourable conditions help the rapid proliferation and growth of these organisms. The dal kept for a long time thus starts fermenting due to bacterial and fungal contamination. The fermentation releases carbon dioxide causing foam on the surface of such dal.