E529 (Calcium oxide) is a chemical compound derived from the calcination of limestone, from clean, crushed eggshells. It is obtained by heat treatment at about 900 C, reaction with water or hydrochloric acid and sodium hydroxide.

It appears in the form of a white powder

What it is used for and where

Food

Ingredient included in the list of European food additives as E529 as acidity regulator, preservative (1).

Cosmetics

Buffering agent. It is an iingredient that can bring an alkaline or acid solution to a certain pH level and prevent it from changing, in practice a pH stabiliser that can effectively resist instability and pH change.

Other uses

• scrubber for SO₂ and NO gases in power plant flue gas and waste water
• heterogeneous base catalyst in biodiesel synthesis (2)
• microwave absorber
• agent for the treatment of contaminated soil

• Molecular Formula   CaO
• Molecular Weight     56.08 
• CAS  1305-78-8
• UNII    C7X2M0VVNH
• EC Number  215-138-9

References_____________________________________________________________________

(1) Cid-López, M.L., Soriano-Melgar, L.D.A.A., García-González, A., Cortez-Mazatan, G., Mendoza-Mendoza, E., Rivera-Cabrera, F. and Peralta-Rodríguez, R.D., 2021. The benefits of adding calcium oxide nanoparticles to biocompatible polymeric coatings during cucumber fruits postharvest storage. Scientia Horticulturae, 287, p.110285.

(2) Boey, P.L., Maniam, G.P. and Abd Hamid, S., 2011. Performance of calcium oxide as a heterogeneous catalyst in biodiesel production: A review. Chemical engineering journal, 168(1), pp.15-22.