milk, a concentrated mass of protein and oil
formed by coagulating the dissolved proteins
with salts that yoke them and the protein-
coated oil droplets together. Bean curd was
invented in China around 2,000 years ago, was
well known by 500 CE, and became a daily
food beginning around 1300. Chinese bean
curd is traditionally coagulated with calcium
sulfate, Japanese bean curd and bean curd
from coastal regions of China with what the
Japanese call nigari, a mixture of magnesium
and calcium salts left over when table salt,
sodium chloride, is crystallized from
seawater.
Making Bean Curd To make bean curd,
cooked soy milk is cooled to about
175ºF/78ºC, then coagulated with calcium or
magnesium salts dissolved in a small amount
of water. The coagulation takes 8–30 minutes.
When the delicate, cloud-like curds have
formed, the remaining “whey” is ladled off, or