Aluminium potassium sulphate
Score impact
-0.30
points/product
Description
The food additive E522, also known as aluminium potassium sulphate or potassium alum, is a chemical compound used mainly as a stabiliser in the food industry. It is a double salt of aluminium and potassium with the formula KAl(SO4)2·12H2O, appearing as colourless crystals or a white, odourless powder with a slightly astringent taste.
Its origin is both natural and synthetic: it is found in minerals such as alunite, but most is produced industrially by reacting aluminium sulphate with potassium sulphate in aqueous solution, followed by crystallisation. This process yields a high-purity product suitable for food use.
The physicochemical properties of E522 include high solubility in water (approximately 140 g/L at 20 °C) and an ability to form complexes with proteins and polysaccharides, which gives it its stabilising function. It acts as a cross-linking agent, improving the texture and consistency of foods, especially in products requiring firmness or gelation. Additionally, it has astringent properties and can act as an acidity regulator in certain applications.
Historically, potassium alum has been used since ancient times as a mordant in dyeing and in traditional medicine. Its use as a food additive in the European Union has been regulated since the early additives directives, and it was re-evaluated by the European Food Safety Authority (EFSA) in 2008 and subsequently in 2018. EFSA established a Tolerable Daily Intake (TDI) of 0.14 mg/kg body weight per day for aluminium from all sources, including E522. The World Health Organization (WHO) has also evaluated aluminium and set a similar TDI of 2 mg/kg body weight per week (equivalent to 0.286 mg/kg/day).
It is important to note that E522 contributes to total aluminium intake, which also comes from other sources such as water, cookware, and medicines.
Regarding food safety, EFSA concluded that dietary exposure to aluminium, including from E522, does not pose a health risk for the general population, although it recommended reducing exposure in certain vulnerable groups such as children and people with kidney disease. The labelling of foods containing E522 must include its name or E number, according to Regulation (EU) No 1169/2011.
Overall, E522 is considered safe within the established limits, but its use is restricted to certain foods and maximum concentrations.
E522 is used as a stabiliser in various food categories, mainly in products requiring a firm texture or controlled gelation. According to Regulation (EC) No 1333/2008, its authorised uses in the European Union include: preserved fruits and vegetables (e.g., stuffed olives, pickled gherkins), where it acts as a firming agent; confectionery products such as hard candies and chewing gum, to improve consistency; and in some fine bakery products, such as biscuits and cakes, where it contributes to structure. It is also used in the preparation of pasteurised egg whites to stabilise foam, and in the production of caviar substitutes (agar-agar pearls).
In the Spanish market, E522 is commonly found in olives stuffed with anchovy or pepper, in pickled gherkins, and in certain hard candies. Authorised limits vary by product: for example, in stuffed olives up to 500 mg/kg (expressed as aluminium) is allowed, while in hard candies the limit is 200 mg/kg. Compared to the US FDA, potassium alum is generally recognised as safe (GRAS) for similar uses, although with restrictions in certain products. In Japan, its use is permitted but with stricter limits in some foods.
It is important to note that E522 is not authorised in foods for infants and young children due to the greater sensitivity of this group to aluminium.
The side effects of E522 are mainly related to the toxicity of aluminium, as the aluminium ion can accumulate in the body. EFSA and WHO have evaluated aluminium and concluded that at usual consumption levels, no significant adverse effects occur in the general population. However, studies in animals and observations in humans have documented that chronic exposure to high doses of aluminium may be associated with neurotoxicity, affecting the central nervous system and possibly linked to diseases such as Alzheimer's, although this relationship is not firmly established.
The proposed biological mechanism includes aluminium's ability to interfere with cellular processes, such as calcium homeostasis and the activity of antioxidant enzymes. Sensitive populations include people with kidney insufficiency, as their ability to excrete aluminium is reduced, which can lead to accumulation and bone or neurological toxicity. Caution is also recommended in children, whose nervous system is developing. No significant interactions with medications have been documented, although aluminium can interfere with the absorption of certain drugs such as tetracycline antibiotics if taken simultaneously.
EFSA, in its 2018 evaluation, set a TDI of 0.14 mg/kg/day for total aluminium and concluded that average dietary exposure in Europe is below this limit, so the health risk is low. Nevertheless, it recommends minimising exposure in vulnerable groups.
In summary, E522 is considered safe in authorised amounts, but total aluminium intake should be monitored.
- Aluminium potassium sulphate
- Potassium alum
- Potash alum
- Potassium aluminium sulphate dodecahydrate
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