Made from Glycine max
Tofu is bean curd: hot soy milk is coagulated with calcium or magnesium salts, then the delicate curds are gathered and pressed into anything from a custardy silken set to a firmer slicing block.1 In the Northeast it matters less as an inherited field staple than as one of the most direct ways to turn regional soybeans into a fresh, neutral protein that can move in many directions.2
Its history is older than most of the modern soy foods built on top of it. McGee places tofu’s invention in China around two thousand years ago, and by the early modern period it was already ordinary daily food rather than a luxury.1 Steinkraus’s description of tofu for sufu production shows the same basic logic still holding: beans are ground with water, the milk is heated and filtered, and a salt-based coagulant pulls the proteins into a curd that can then be pressed, cut, salted, inoculated, or fermented further.3
That high water content is what makes tofu so useful in a notebook like this one. The fresh curd is mild and almost blank on its own, but it readily absorbs salt, smoke, acids, grain ferments, and mold growth. Freezing concentrates the protein network and leaves behind a more open, spongy structure when thawed, while gentler coagulation leaves enough moisture in place for silken tofu and other custard-like sets.1 Tofu is therefore not just a finished food but a structural starting point: a way of translating the chemistry of soy milk into something sliceable, fryable, dryable, or fermentable.