Why does the starch in steamed bread change in the mouth at first?

The starch in steamed bread will be hydrolyzed into maltose.

Steamed bread contains starch, and the mouth can secrete saliva. Protein in saliva has catalytic activity, which can catalyze starch hydrolysis to maltose. The optimum pH value of salivary amylase is in the neutral range, and chlorine and thiocyanate in saliva can activate this enzyme. After food enters the stomach, salivary amylase can continue to be used for a period of time until the stomach contents become acidic and the pH value is about 4.5.

Starch is an important part of food, so it feels a little sweet to chew rice. This is because amylase in saliva hydrolyzes starch into monosaccharides. After food enters the gastrointestinal tract, it can also be hydrolyzed by amylase secreted by the pancreas, and the formed glucose is absorbed by the small intestine wall and becomes a nutrient for human tissues. Starch is a high molecular polymer of glucose, which is hydrolyzed into maltose in disaccharide stage and glucose is obtained after complete hydrolysis.

Because of the important position of glucose in organisms, understanding its chemical composition and structure has become an important topic in organic chemistry in the19th century. From 65438 to 0884, Emile Fisher began to study sugar. ?

At that time, only four monosaccharides were known: two aldoses (glucose and galactose) and two hexoses (fructose and sorbose), with the same molecular formula. H. iKhani, a chemist at the University of Munich, initially proved that glucose and galactose are linear pentahydroxy aldehydes, while fructose and sorbose are linear pentahydroxy ketones.