Calcium Hydroxide
The short version
Slaked lime — the alkali of corn nixtamalization, tofu coagulation, and traditional pickling.
It's widely considered safe at the amounts used in food, so we mark it green. The Safety section below has the details.
Where it comes from
Produced by hydration of calcium oxide (quicklime), itself from thermal decomposition of limestone. Among the oldest deliberately used chemicals — Mesoamerican civilizations used it for corn nixtamalization for at least 3500 years.
How it's used
The alkali of nixtamalization — soaking corn in calcium-hydroxide-treated water before grinding releases bound niacin, transforms aromatics, and produces the distinctive tortilla/masa flavor and aroma. Also coagulates soft tofu, firms pickled vegetables (cucumber and watermelon-rind pickles), and clarifies sugar in cane-juice processing.
Safety profile
ADI not specified — considered safe at residual food-use levels (typically <0.1% in finished product). The active material is corrosive in pure form, but is fully neutralized during processing.
Physical & chemical properties
White powder, sparingly soluble in water (limewater). Strongly alkaline solution. Reacts exothermically with acids.
Regulation worldwide
Permitted globally without restrictive limits as a processing aid and acidity regulator.
Educational information only. Not medical or dietary advice.