Ammonium phosphates
A mineral salt used as a leavening agent in baked goods, helping dough rise and controlling acidity during baking.
What is it?
Ammonium phosphates are salts formed from phosphoric acid and ammonia. The two forms permitted as food additives are monoammonium phosphate (E342i) and diammonium phosphate (E342ii). Both are white crystalline powders soluble in water.
What does it do?
Acts primarily as a leavening agent: when heated, ammonium phosphates release ammonia gas and carbon dioxide, causing baked goods to rise. Also used as an acidity regulator and yeast nutrient (diammonium phosphate is a nitrogen source that feeds yeast during fermentation). In very small quantities it can buffer pH in doughs and batters.
Where you will see it
Found mainly in bread, biscuits, crackers, wafers, and pastries. Diammonium phosphate is also used in winemaking as a yeast nutrient. On a UK ingredient label it appears as 'ammonium phosphates', 'E342', or its sub-forms 'E342(i)' and 'E342(ii)'.
What the science says
Phosphate intake from food additives
Ammonium phosphates contribute to overall dietary phosphate intake. High total phosphate consumption, primarily from phosphate additives across many processed foods, has been associated in observational studies with poorer cardiovascular and kidney outcomes, particularly in people with existing kidney disease. However, the contribution from E342 specifically is small relative to phosphates found naturally in meat, dairy, and grains.
Elevated serum phosphate, driven partly by inorganic phosphate additives, is associated with increased cardiovascular mortality in people with chronic kidney disease (CKD) in observational cohort data.
EFSA's Panel on Food Additives and Nutrient Sources (ANS Panel) reviewed phosphates as a group and concluded that exposure from their combined use across food categories warrants monitoring, while noting that natural dietary phosphate substantially exceeds additive-derived phosphate for most consumers.
Ammonia release during baking
The ammonia released when ammonium phosphates decompose under heat largely volatilises off during baking. Residual ammonia in the finished product is typically very low. No toxicological concern has been identified at the levels that remain in baked foods.
Thermal decomposition of ammonium phosphates in baking conditions results in ammonia gas that mostly escapes into the atmosphere; residues in finished baked goods are well below any level of toxicological concern.
Where it stands with the regulators
Who should be careful
People with chronic kidney disease are advised by nephrologists to limit all inorganic phosphate additives, since impaired kidneys struggle to excrete excess phosphate. Look for 'ammonium phosphates' or 'E342' on the label. Those on a medically prescribed low-phosphate diet should treat it the same as any other phosphate additive.
The honest read
Ammonium phosphates have been used in commercial baking for well over a century and their chemistry in food is thoroughly characterised. The main open question is not E342 itself but the cumulative load of phosphate additives across all processed foods eaten daily. EFSA flagged this collective exposure picture in 2019 and called for intake monitoring. For most people eating biscuits or bread in normal quantities, the phosphate from E342 is modest compared with phosphate naturally present in meat, dairy, and wholegrains. The kidney-disease association is real but rests on observational data about total phosphate burden, not on any study specifically implicating E342.
Related additives
Common questions
Is E342 banned in the UK?
No. Ammonium phosphates are permitted food additives in the UK under retained and assimilated EU food law. They appear on the UK FSA approved-additives list.
Do ammonium phosphates leave ammonia in my food?
Almost none. The ammonia produced when ammonium phosphates react during baking almost entirely escapes as gas in the oven. Finished biscuits and bread contain only trace residues.
What foods contain E342?
Mainly biscuits, crackers, wafers, and some breads. Diammonium phosphate (E342ii) is also added to wine and cider as a yeast nutrient during fermentation.
Is E342 vegan?
Yes. Ammonium phosphates are mineral salts produced synthetically from phosphoric acid and ammonia. They contain no animal-derived ingredients.
Sources
- EFSA ANS Panel: Re-evaluation of phosphoric acid and phosphates (E 338-341, E 343, E 450-452) as food additives
- EFSA Scientific Opinion on the safety of ammonium phosphates (E 342) as a food additive
- UK FSA: Approved additives and E numbers
- EU Regulation 1333/2008 on food additives (Annex II)
- Block GA et al., Association of serum phosphorus and calcium x phosphate product with mortality risk in chronic hemodialysis patients, Journal of the American Society of Nephrology
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