Each of you take a piece of bread or roti or some cooked rice. Put it in your mouth, chew three to four times and swallow it. Did the taste change as you chewed it?
The enzymes used to aid in digestion are contained within the buccal cavity, and as such when one masticates a bite of food more enzymes are produced. Carbihydrates are broken down by these enzymes into sugar. Sugar is sweet and these sweet end products taste sweet.