E-numbers / Thickeners & emulsifiers / E405
also: Propane-1,2-diol alginate · PGA
A seaweed-derived thickener and emulsifier, chemically modified to dissolve in acidic foods such as salad dressings and beer.
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Water, Sugar, Pineapple Juice from Concentrate (4%), Dextrose, Stabilisers (Guar Gurn, Xanthan Gum, Propylene Glycol Alginate), Acid (Citric Acid), Colours (Curcumin, Beta-Carotene), Flavouring
Propylene glycol alginate is made by partly esterifying alginic acid (extracted from brown seaweed) with propylene glycol.
32
of the 43,325 UK supermarket foods we checked declare E405 in their ingredients
That is under 0.1%, counted by its code or its name.
Counted by NutraSafe from UK supermarket ingredient lists, September 2026. How we counted
Propylene glycol alginate is made by partly esterifying alginic acid (extracted from brown seaweed) with propylene glycol. The modification makes it stable and soluble in acidic, low-pH conditions where plain alginates would precipitate. It is also known by the chemical name propane-1,2-diol alginate.
It thickens and stabilises water-based mixtures, preventing oil and water from separating. In acidic foods it keeps emulsions smooth, stops foam from collapsing, and gives dressings a consistent pourable texture. During digestion it breaks down into alginic acid (which the body passes unabsorbed) and propylene glycol, which is absorbed and oxidised normally in the body.
Most commonly found in salad dressings, mayonnaise-style sauces, beer and beer foam stabilisers, fruit-flavoured drinks, ice cream and frozen desserts, cake toppings, and some low-calorie dairy products. On ingredient labels it appears as 'propylene glycol alginate' or 'E405'.
E405 hydrolyses in the gut, releasing propylene glycol (propane-1,2-diol). EFSA assumed worst-case that up to 45% of the additive converts to free propylene glycol, all of which enters the bloodstream. The body oxidises propylene glycol to lactic and pyruvic acids via normal metabolic pathways. No accumulation has been observed at food-additive exposure levels.
EFSA's 2018 re-evaluation assumed 100% systemic availability of released propylene glycol, leading to an ADI of 55mg/kg body weight per day for E405, equivalent to 25mg/kg bw/day expressed as propylene glycol.
Because young children eat proportionally more of certain foods relative to body weight, EFSA modelled their exposures separately. At the 95th percentile, toddlers reached 39.6mg/kg body weight per day and infants on specialised medical foods reached 46.8mg/kg bw/day. Both remained below the ADI of 55mg/kg bw/day, though EFSA flagged limited use-level data across most authorised food categories as a gap.
95th percentile exposure in toddlers reached 39.6mg/kg bw/day; infants on specialised medical foods reached 46.8mg/kg bw/day, both below the established ADI, though use-level data were available for only 3 of 21 authorised food categories.
E405 is one of two authorised food additives that release propylene glycol in the gut (E1520, propylene glycol itself, is the other). EFSA noted that exposure estimates for E405 do not account for the additional propylene glycol contributed by E1520 used in the same diet. The combined load was flagged as a gap but not modelled, so cumulative intake is uncertain.
EFSA flagged that propylene glycol exposure from E405 is additive with that from E1520 (propylene glycol, E1520), and that the cumulative exposure was not assessed in the 2018 opinion.
Multiple animal and in vitro studies found no evidence that propylene glycol alginate or its breakdown products damage DNA, cause tumours, or affect reproduction or development. Acute toxicity is classified as low across species tested.
Multiple genotoxicity assays, subacute and subchronic animal studies, and reproductive/developmental toxicity studies found no adverse effects attributable to propylene glycol alginate.
There are no declarable allergens associated with E405. People following a diet free from seaweed-derived ingredients may wish to note it comes from brown algae. Look for 'propylene glycol alginate' or 'E405' on the label.
E405 has been in food use for decades and has been formally evaluated several times. The EFSA 2018 opinion is the most thorough: it found no genotoxicity, carcinogenicity, or reproductive harm, and modelled exposures in the most vulnerable groups (toddlers, infants) below the numerical ADI. The outstanding uncertainties are procedural rather than alarming: sparse use-level data across most food categories, uncontrolled stereochemistry of the ester, impurity limits recommended for review, and unanswered questions about combined propylene glycol intake when E405 and E1520 both appear in the same diet. None of these gaps have been resolved by a follow-up opinion, so cumulative propylene glycol exposure from a diet high in additives remains imprecisely characterised.
No. E405 is approved in the UK under the assimilated EU Regulation 1333/2008 and appears on the UK FSA's approved-additives list.
E405 breaks down in the gut to release propylene glycol. The body processes propylene glycol through normal metabolic pathways. EFSA's 2018 re-evaluation found no safety concern at the levels found in food, though it noted that propylene glycol also enters the diet via E1520 and the combined intake was not fully assessed.
Salad dressings, mayonnaise-style sauces, beer (as a foam stabiliser), fruit drinks, ice cream, cake toppings, food supplements, and some specialised dietary foods. Check for 'propylene glycol alginate' or 'E405' in the ingredients list.
The alginate base comes from brown seaweed, and the propylene glycol used in production is synthetic. E405 itself contains no animal-derived ingredients, so it is generally considered compatible with a vegan diet. Individual certifications vary by manufacturer.
Last reviewed: 20 June 2026
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