Propylene glycol esters
An emulsifier made by combining propylene glycol with fatty acids, used to create stable, airy textures in baked goods, whipped toppings and frozen desserts.
The manufacturing process can introduce glycidyl esters, which are recognised process-derived carcinogens. Current EU and UK specifications for E477 set no limit for glycidyl esters. No long-term carcinogenicity or reproductive toxicity studies for E477 itself have been done.
What is it?
Propylene glycol esters of fatty acids (also called propane-1,2-diol esters of fatty acids) are produced by reacting propylene glycol with edible fats and oils. The result is a mixture of mono- and diesters, often derived from hydrogenated palm, soya or sunflower oil. The specific crystalline properties of the distilled monostearate form (PGMS) are particularly valued in food processing.
What does it do?
Acts as an emulsifier and foam stabiliser. It helps fat and water mix and, crucially, stabilises the alpha-crystal form of monoglycerides, which is the form best at trapping air bubbles. This is why it is especially effective in whipped and aerated products: it creates and holds a stable foam structure, giving products their light, creamy or spongy texture.
Where you will see it
Whipped cream alternatives, non-dairy dessert toppings, powdered cake-mix emulsifiers, edible ices and ice cream, fine bakery wares such as cakes and muffins, chocolate confectionery coatings, and some processed dairy-analogue products. On a UK label it appears as 'emulsifier (E477)', 'emulsifier (propylene glycol esters of fatty acids)', or 'E477'.
What the science says
Specification gaps: glycidyl esters and 3-MCPD
Propylene glycol esters are manufactured from refined or hydrogenated vegetable oils. The refining and hydrogenation process can generate glycidyl fatty acid esters and 3-MCPD esters as by-products. Glycidyl esters are recognised genotoxic carcinogens. The EU and UK specifications for E477 currently include no maximum limit for either contaminant, which EFSA identified as a significant gap in its 2018 re-evaluation.
Current specifications for E477 do not include maximum limits for glycidyl esters, 3-MCPD esters, trans-fatty acids or erucic acid. EFSA recommended the European Commission revise specifications to address these gaps.
Glycidyl esters are hydrolysed in the gut to glycidol, which is genotoxic and carcinogenic in animal studies and is classified as a probable human carcinogen.
No long-term toxicity data for E477 itself
When EFSA completed its systematic re-evaluation of E477 in 2018, it found no chronic toxicity, carcinogenicity, or reproductive and developmental toxicity studies had been conducted using propylene glycol esters specifically. The safety conclusion was based on short-term animal data and on the metabolic fate of the hydrolysis products (propylene glycol and fatty acids), both of which are common in the diet. This is a structural evidence gap.
No chronic toxicity, carcinogenicity, reproductive or developmental toxicity studies with propane-1,2-diol esters of fatty acids were available to the EFSA Panel during the 2018 re-evaluation.
Short-term rodent studies gave a NOAEL of 6,768 mg/kg bw/day for rats and dogs tolerated 432 mg/kg bw/day without adverse effects. Acute toxicity was characterised as low.
Cumulative propylene glycol exposure
When E477 is digested, it releases propylene glycol (itself authorised as E1520). Propylene glycol also appears in E405 (propylene glycol alginate). EFSA noted that dietary exposure from all three sources combined could approach or exceed the ADI for propylene glycol in some population groups, particularly children who consume high amounts of ice cream or whipped desserts. EFSA flagged plans to establish a group ADI to control the combined load.
EFSA noted that combined exposure to propylene glycol from E477, E405 and E1520 could warrant a group ADI and recommended further assessment of cumulative dietary exposure.
Heavy metal contaminant limits
The current EU and UK specifications permit up to 3 mg/kg arsenic and 2 mg/kg lead in E477 as sold. EFSA noted that at these levels, the contaminants could make a meaningful contribution to overall dietary exposure, particularly for heavy users of products containing the additive. EFSA recommended reducing these permitted limits.
EFSA flagged that existing arsenic (3 mg/kg) and lead (2 mg/kg) limits in E477 specifications may significantly contribute to dietary exposure of toxic elements and recommended tightening them.
Where it stands with the regulators
Who should be careful
People limiting propylene glycol intake for medical reasons should watch for E477, E405 and E1520 together, as all three release propylene glycol on digestion. Those avoiding products processed with hydrogenated vegetable oils may wish to note that E477 is commonly derived from such oils. Look for 'E477' or 'propylene glycol esters of fatty acids' in the ingredients list.
The honest read
The science here is messier than the approved status suggests. E477 has been authorised for decades and its breakdown products, propylene glycol and fatty acids, are ordinary dietary components. The short-term animal data is reassuring on acute and sub-acute toxicity. The unsettled part is what EFSA did not have: no long-term carcinogenicity study, no reproductive toxicity study, and no specification limits for glycidyl esters, which are process-derived contaminants recognised as probable human carcinogens. EFSA asked the European Commission to fix the specifications in 2018. Whether and when that has been done in practice is the outstanding question. The real-world exposure from E477 at typical food use levels is low, but the absence of the key long-term studies is a genuine data gap rather than a clean bill of health.
Related additives
Common questions
Is E477 banned in the UK?
No. E477 is listed as an approved additive on the UK FSA's approved-additives list, under 'Emulsifiers, stabilisers, thickeners and gelling agents'. The UK retained the EU authorisation after Brexit via assimilated EU Regulation 1333/2008. It is permitted in a range of food categories including baked goods, edible ices and confectionery coatings.
Why did EFSA flag concerns about E477 if it is approved?
EFSA's 2018 re-evaluation confirmed the ADI and found no safety concern at typical food use levels. However, EFSA also identified specification gaps: the current rules set no maximum limit for glycidyl esters, a group of process-derived carcinogens that can occur in products made from refined or hydrogenated oils. EFSA recommended the European Commission update the specifications to add such limits. The additive remains approved while those revisions are considered.
What foods contain E477?
E477 is used mainly in products that require a stable aerated or emulsified texture: non-dairy whipped cream alternatives, powdered cake emulsifiers and cake mixes, ice cream and frozen desserts, chocolate and confectionery coatings, and some fermented dairy analogues. It appears on the label as 'emulsifier (E477)' or 'emulsifier (propylene glycol esters of fatty acids)'.
Is E477 vegan?
Not always. E477 is produced from propylene glycol and fatty acids derived from fats and oils. The fatty acid source is most often vegetable oil (palm, soya or sunflower), making those versions plant-based. However, animal-derived fat sources are also permitted, so vegan status depends on the specific supplier and product. If you need certainty, contact the manufacturer directly or look for a certified vegan label.
Sources
- Re-evaluation of propane-1,2-diol esters of fatty acids (E 477) as a food additive, EFSA Journal 2018
- Re-evaluation of propane-1,2-diol esters of fatty acids (E 477), PMC full text
- UK FSA Approved Additives and E Numbers
- EFSA CONTAM Panel opinion on glycidyl esters, EFSA Journal 2016
See this on every food you scan
NutraSafe reads the label and puts every additive into plain English, with the source, right in the app.
Get NutraSafe on the App Store