I’ve made soya bean milk at home quite a few times (as mentioned here and here) and written about how one could make soya sauce at home too. Today’s Sunday Times food question column by Chris Tan addresses the issue of making soya bean curd/tofu at home.
The basic process involves setting soya bean milk into a solid form by using a coagulating agent. Chris Tan explains the differences between the types of coagulants, which also helps us to understand the different ingredients used in commercial tofu.
The three main types of coagulants are:
1) Calcium sulphate, a.k.a. gypsum. As this is also one of the ingredients in plaster of paris, the Chinese word is shi2 gao1 石膏, which can also refer to a plaster cast for a broken bone, so don’t be surprised if you see poorly-translated Chinese language cookbooks calling for ‘plaster of paris’. This coagulant is used in Chinese-style tofu, and produces a more soft, moist texture. Available from Chinese provision or medicine shops.
2 ) Nigari. A extract of seawater containing a high proportion of magnesium chloride. Used in Japanese-style tofu, and explains why some Japanese tofu-makers use seawater. A smoother, subtly sweeter effect is created by using nigari. Powdered or liquid form available at Japanese supermarkets and health food stores such as Nature’s Glory.
3) Glucono delta-lactone (GDL). An organic compound developed a few decades ago, and makes a delicate, pudding-like tofu. Instant tofu kits from Japanese supermarkets use GDL, alongside packets of soya bean milk powder to which you add water. Many years ago, when I visited an aunt who lives in Britain, she made a soya bean curd dessert 豆花 for me using one of these kits; as I remember, the texture was very smooth.
Each type of coagulant produces different textures and subtle flavours, and commercial tofu manufacturers often mix up blends of coagulants. You’ll need to experiment and see which you prefer. Food intolerance sufferers might find they are more sensitive to certain types of coagulants as compared to others.