Caustic soda is the common name for sodium hydroxide, a strongly alkaline compound used in soap making, drain clearing, and food processing. In food plants it is the backbone of clean-in-place systems, dissolving fats, proteins, and burnt-on residues from equipment, and it is used in olive curing, cocoa processing, and pretzel making, where brief alkaline treatment develops colour and flavour. It is corrosive and causes severe burns, so food-grade handling demands protective equipment and thorough rinsing to leave no residue. Its dual identity, essential processing aid and hazardous chemical, makes strict control and training mandatory.