From above adress:
Starch is insoluble in cold water but in warm water it swells until "gelatinisation temperature" when is *begins* to lose structure and leach out compounds. A single granule will gelatinise over a range of ~2C but a sample of complex starch grits or particles will have a 4-10C range. Sucrose in solution will raise the gelatinisation temperature of starch by reducing its swelling. So in a concentrated mashing situation, the conversion of more easily gelatinised small starch particles to simple sugars can slow the gelatinisation of larger less gelatinised particles, extending the range.
The *laboratory* gelatinisation temperature of barley *malt* starch is 64-67C (147-153F), unmalted barley is a couple of degrees lower. However as I have pointed out above, this range can be extended by malt modification, crush, mash concentration, and even the weather down at the barley farm. Even after "gelatinisation", there is further breakdown of the starch granule's matrix structure. Technically gelatinisation is not complete until there is no structure left at all. The fact that *infusion* mashes do not fully gelatinise malt starch is shown by the slight but consistent higher yield of *decoction* mashes.
I think inadequate time between 70C and 75C, inadequate stirring and coarse crush are main reasons for ungelatinised, therefore unconverted starch.
I'm with that. I like to know my grain starch is gelatinized before i start the mash clock
