| MadSci Network: Chemistry |
Hi, Kim. Flake cereals are made by partly cooking whole grains, then rolling them flat and baking them until brown and dry. Water softens the cell walls gelatinizing the starch grains and making them soggy. The starch forms 'walls' primarily composed of amylopectin.
The sogginess is really due to the water absorption through the walls. You can think of these cellular walls as gas filled foams just waiting to absorb water. The rate of transfer and the amount of water it absorbs will determine the difference in sogginess of different cereals. Only water impermeable packaging and internal water barriers can prevent loss of crispiness over weeks.
Another factor is that the more water it absorbs the denser the grain is and the less air it will have. A cereal with more air will taste lighter and crispier. Different grains also have varying degrees of water absorption capabilities due to their protein makeup. For example, gluten is found primarily in wheat and it absorbs more water than corn which is not high in gluten.
Finally another reason for sogginess, or lack of, are additives. Certain additives like phosphates absorb more water.
Hope that helps and you can find out more on cereal chemistry in Harold McGee's book called 'On Food and Cooking.'
Try the links in the MadSci Library for more information on Chemistry.