Stirring during the coagulation

It helps to mix the coagulant thoroughly with the soybean milk and thicken it. You seem to be interested in tofu production. Check the following website out for more information:

http://en.wikipedia.org/wiki/Tofu

A friendly word of advice here; besides the amount of coagulant added, the texture also depends upon the temperature and time required to drain the tofu.

I would assume that there is really 2 purposes, the first is to mix in the coagulant, but that will be a relatively short process. Continuing the mixing however will ensure that flocs of coagulated contact each other and therefore speed up the coagulation process. This would be similar to the flocculation process in water treatment.

You may note that the production is highly sensitive to the type, size and speed of mixer blade. This relates to the shear rate distribution in the tank. Too much shear and flocs will break up, not enough and won't collide so easily. If you are having problems a larger slow moving impeller is better at distributing shear, and the total shear in the tank is proportional to the power applied (you will need to calculate this though so that gearbox losses etc are taken into account).