Question

If we chew rice and bread for a few minutes it start tasting sweet give reason why

Answer 1

it is the chain of sugar molecules known as starch .......this is why the bread tests sweet after lots of chewing - the amylase enzymes breaks down the starch and turn it in glucose. Amylase isn't only enzyme to break down food into the molecules we can absorb..
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hope it will help u

Answer 2

The answer is, When the food enters in our mouth the salivary glands start giving out saliva to make that food easy to travel in the oesophagus further..and so the saliva includes glucaose a type of sugar.. so