Q I WOULD like to find out how to make soya bean curd. I have made soya bean milk using a blender, but have yet to figure out how to make the milk coagulate into curd.
A Beancurd is made by coagulating fresh soya bean milk with one or more setting agents.
Chinese-style tofu commonly uses calcium sulphate as a coagulant. This mineral, known as gypsum, is also found in plaster of paris, hence the slightly alarming recipes in old or mistranslated Chinese cookbooks telling you to add plaster of paris to your soya bean milk.
Japanese-style tofu typically uses nigari, an extract of seawater rich in magnesium chloride. Some old-school tofu makers around Japan's coasts still make a rustic tofu with fresh seawater and a few modern manufacturers have added a twist by using deep-sea water.
Another coagulant that has only been around for a few decades is glucono delta-lactone, or GDL, an organic compound.
These three coagulants produce slightly different textures and according to connoisseurs, subtle differences in flavour. Calcium sulphate makes higher yields of soft, moist tofu. Nigari yields a smoother, faintly sweeter tofu and GDL makes a delicate, pudding-like tofu.
Commercial manufacturers often stir up blends of different coagulants for precise texture control.
Various permutations of coagulant, water content, temperature, pressing and other processes give rise to the different forms of tofu sold in our markets and supermarkets.
Have fun experimenting at home. You can buy gypsum at Chinese provision or medicine stores and powdered or liquid nigari in Japanese supermarkets. The latter also sell Japanese instant tofu kits that include pouches of soya bean milk powder you just dissolve in water, plus sachets of GDL. Get a good guide, such as The Book Of Tofu by William Shurtleff and Akiko Aoyagi, to clue you in on the finer points of tofu-making.
This article was first published in The Sunday Times on Mar 2, 2008.