Just learned it in school, you can say a lot of bad things about dieticians, but they do know some things which most others don't know
I don't know the correct English terms but I'll try to explain:
When you heat up potatoes (or any other carb source, like spaghetti etc)
it'll take water in it's cells. At about 75°C the cells become 4-5x as big, the cellwalls can't take it anymore and they'll crack (but still remain intact).
I think this is called 'pregelatinization' in english but correct me if wrong. If you continue to heat them up (above 95°C) they'll crack competely and the cell is 'destoyed'. (gelatinization)
When this happens, your body is able to digest potatoes (I'm not really sure if you can't digest them before cooking, but it'll certainly be much harder). If you let the potato cool down, then the starch will cristallize again, but the won't return to their former form, since the cells are destroyed. This means that they are still digestable but not as easily as when they were just cooked (this process is called retrogradation).
And while I'm at it: here are 3 types of starch.
RDS: rapidly digestable starch (just cooked starch), fast digestion
SDS: slowly digestable starch (mostly raw vegetables), slow but complete digestion
RS: resistant starch: no digestion (fibre)
- RS1: fysical unaccesible starch: coarse grains and seeds
- RS2: resistant starch (something like this, can't translate it properly): raw potatoes and bananas
- RS3: retrogradated starch: cooled potatoes, bread, ...
So you can see that cooled potatoes contain RS3 starches.
Type of starch /100g starch (not for 100g of vegetable):
cooked (warm) potato: 65%RDS, 5%SDS,5%RS
cooked (cold) potato: 53%RDS, 11%SDS, 10%RS
It's not an enormous difference, but it is some difference and I hope it's explained pretty well and written in good English.
And, Hoosegow, I hope it does make sense now and that some of you have learned sometyhing new
EDIT: It's almost the length of a KPj post