Imagine that you put a slice white bread in a bag with lukewarm water. After five minutes, the slice of bread transformed into a watery mess that does not look particularly appetizing.. Do the same thing with a slice of sourdough bread or whole wheat bread. After five minutes have hardly anything happened and bread plate looks almost like when you put it in the bag.
the Pouch trick is a simple illustration of what happens in the stomach. French bread that quickly dissolved has high GI, while wholemeal bread has significantly lower GI. Using påstricket you will quickly see that the mashed potatoes, they cooked snabbmakaronerna and many cereal varieties are appallingly high GI. The cooking method may also affect the GI value, paste eaten aldente, i.e. shorter cooking time than the lower GI overcooked pasta etc..