- In carbonation process, 1 to 1.5% of lime by weight at 50 to 55°C is added to the juice. CO2 gas is bubbled to remove alkalinity. The temperature is raised to the boiling point to remove excess carbonic acid.
- Sugar mill carbonation after the mill crushes, shreds, or presses the cane or beets to extract juice, it adds calcium oxide (milk of lime).
- The calcium oxide raises the juice to 11pH or slightly more.
- The water in the juice reacts with the calcium oxide to form calcium hydroxide.
- The chemical addition has three desirable effects:
- The high pH prevents the sugar from becoming starch or reverting to non-sucrose forms
- Organic acids are changed into salts for later removal by precipitation
- Foreign matter is kept in suspension for removal by filtration. To prevent scale build up in subsequent stages, the mill must remove the excess lime via carbonation.