Cornstarch

This is pure starch, stripped of all protein. The thermodynamics of cornstarch are precise: it gelatinizes around 85°C. Unlike flour (which yields matte, opaque sauces), it produces a translucent, glossy binding with a gel-like texture. It is the secret to mirror-like Asian glazes. However, its starchy network is fragile: boiling for too long or overly violent blending after thickening will break the starch chains, making the sauce irreversibly liquid again.