torque rating for mash stirrer?

[conkers]

Hey everyone,
I'm planning to build an automated mash stirrer to keep my corn mash from sticking and burning to the bottom of the pot.
I know some use an icecream mixer motor but am doubtful it will stir 15-18 kgs of wet grain.
I've been looking around at geared AC motors and have been talking to a company that sell them. They are trying to recommend a motor to me but need to know the power and torque I need. The power rating I think should be somewhere around 1/4-1/2hp that'll should be plenty I reckon, but the torque rating I'm not so sure about.
Has anyone got any suggestions about how much torque I'd need to turn a 500mm paddle at 30rpm?
cheers
conk