E-numbers / Other additives / E517
also: Ammonium sulfate · diammonium sulphate
An inorganic salt used as a yeast nutrient in bread and flour production, and as an acidity regulator in a small number of foods.
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Ammonium sulphate is the ammonium salt of sulphuric acid.
Ammonium sulphate is the ammonium salt of sulphuric acid. It is a white crystalline powder with the chemical formula (NH4)2SO4. It occurs naturally in some environments but the food-grade version is produced synthetically. It provides both ammonium ions (a nitrogen source) and sulphate ions.
In bread and flour milling it acts as a yeast food, supplying nitrogen that yeast needs to grow and ferment efficiently during dough proving. It also functions as a dough conditioner and acidity regulator, helping control pH during fermentation. In other applications it can act as an anti-caking agent or processing aid.
Most commonly found in commercially baked bread, rolls, and flour mixes where it feeds yeast during fermentation. It may also appear in some baking powders and flour treatment agents. On an ingredient label it appears as 'ammonium sulphate' or 'E517'.
The European Food Safety Authority re-evaluated the group of sulphate salts including E517 in 2019. The panel concluded that exposure from food use does not raise a concern at the levels actually used in food. No numerical acceptable daily intake was considered necessary because the compounds are normal constituents of the diet and are metabolised by ordinary physiological pathways.
EFSA's Panel on Food Additives and Flavourings concluded that exposure to ammonium sulphate at reported food use levels does not raise a safety concern, and set no numerical ADI.
At very high doses, sulphate salts can cause a laxative effect in humans. EFSA noted this threshold in its re-evaluation. Estimated dietary exposure from food additive use sits far below the level at which this effect has been observed, so it is not relevant to normal food consumption.
A dose of 300mg sulphate per kg body weight per day produced a laxative effect in human studies; mean and high-percentile dietary exposure from E517 use in food was estimated to fall well below this threshold.
When ammonium sulphate is metabolised, it releases ammonium ions which the body converts to ammonia and then to urea, which is excreted. This is a normal metabolic route for all dietary protein. At the small quantities supplied by food additives, this pathway presents no issue for people with normal kidney and liver function. People with urea cycle disorders, who cannot process ammonia normally, are a specific exception.
Ammonium ions are a normal product of protein metabolism and are processed via the urea cycle; additive-level exposure contributes negligibly to the total ammonium load from a typical diet.
People with urea cycle disorders, a rare inherited condition affecting ammonia metabolism, are advised to avoid unnecessary sources of ammonium compounds. Check for 'ammonium sulphate' or 'E517' on the label. For everyone else there is no established food-additive-level concern.
Ammonium sulphate has been used in bread-making for decades, primarily as a yeast food. The 2019 EFSA re-evaluation is the most thorough recent review, and it found no concern at the quantities used in food. The science on this additive is not contested or particularly active. The sulphate portion is the same ion found in ordinary tap water in many areas of the UK; the ammonium portion is handled by the same metabolic machinery that processes protein. The picture here is straightforwardly settled.
No. Ammonium sulphate is on the UK FSA approved additives list and remains permitted under assimilated EU Regulation 1333/2008. It is approved across the UK and EU.
Ammonium sulphate is used in agriculture as a nitrogen fertiliser, but food-grade E517 is a separately manufactured and controlled ingredient. The compound itself is the same molecule, but purity standards differ. Its use in bread production as a yeast nutrient predates widespread awareness of its agricultural role.
It appears most often in commercially produced bread, rolls, and bakery products. It feeds the yeast during fermentation. It may also be present in some flour blends and baking powders. Home-baked bread made with plain yeast and flour typically does not contain it.
Yes. Ammonium sulphate is an inorganic salt derived from a synthetic process. It contains no animal-derived ingredients and is suitable for vegans.
Last reviewed: 20 June 2026
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