Source: University of Illinois - International Soybean Program
2 3/4 to 3 cups (400 grams) whole soybeans
3 tablespoons (15 grams) calcium sulfate
Clean whole soybeans by removing dirt and damaged soybeans.
Soak cleaned dry whole soybeans in 5 times tap water weight overnight or at least 8 hours at room temperature.
Drain and rinse with cold water (weight of the soaked soybeans is about 800 grams).
Grind the soaked soybeans into slurry in a Warning blender in 3000 grams tap water for 3 minutes at high speed.
Filter through cheesecloth to remove fibrous materials (okara).
Collect the liquid portion.
Simmer the soymilk for 10 minutes. Weigh out 3000 grams cooked soymilk.
Cool the cooked soymilk to 80 degrees F. Monitor the temperature of soymilk closely.
Add a preheated coagulant solution (15 grams calcium sulfate in 100 ml water) to the soymilk with agitation. Immediately stop stirring and the flow of the soymilk as the curd beings to form. Allow the curd to set without disturbing for 10 minutes.
*In general, the amount of coagulant is 0.25 to 0.5% of cooked soymilk by weight.
Break the curd evenly. Transfer coagulated dispersion into a tofu mold lined with cheese cloth.
Fold cloth, cover with tofu lid and press for 15 minutes.
Remove tofu lid, unfold the cloth and remove the tofu mold. Cut tofu into pieces and soak in cold water.
Hold the tofu in refrigerator and change soaking water daily.