When bread dough is baked in a oven what type of reaction occurs

Browning Reactions

When the baking temperature reaches 300 degrees Fahrenheit, sugar undergoes what is known as a Maillard reaction, a chemical reaction between amino acids, proteins and reducing sugars. The result is browning, which forms the crust of many baked goods, such as bread.

the answer is the index of refraction of the second medium is higher. i just took the test.