E331ii - Disodium citrate
What it is and how it is used
Disodium citrate is citric acid with two of its three acid groups neutralised by sodium — the middle member of the sodium citrate family, between monosodium (E 331(i)) and the much more common trisodium citrate (E 331(iii)). It is made by neutralising citric acid, which itself comes from fermenting sugar with the mould Aspergillus niger rather than from fruit.
Partial neutralisation is the whole point. A half-neutralised citrate is a buffer: it resists pH change in both directions, holding a product at a target acidity as other ingredients try to shift it. It also chelates calcium, which is what stops milk proteins curdling when they meet acid or heat.
Foods commonly containing it
Fizzy and still soft drinks, jams and fruit preparations, processed and spreadable cheese, UHT and evaporated milk, ice cream, and effervescent tablets.
Safety summary
Sodium citrates are authorised in Great Britain as E 331 and sit in Group I — the set of additives permitted at quantum satis, meaning no numerical maximum is set and use is limited to the amount needed for the technical effect. Disodium citrate is specified as E 331(ii).
EFSA re-evaluated citric acid and its salts and found no safety concern at reported uses, with no numerical ADI considered necessary. Citrate is a normal intermediate in human energy metabolism, which is the reason no daily limit is set.