# Alum (double Sulfate Of Al And Nh4, K, Or Na)

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**Safety rating:** CAUTION
**CAS number:** 977007-61-6
**Category:** firming-agent
**FDA GRAS:** no
**Adverse events (FDA AERS):** 0
**FDA recalls:** 0
**Last updated:** 2026-04-02

## Summary

Alum is a group of double sulfate salts containing aluminum combined with ammonium, potassium, or sodium. It functions as a firming agent in food products to maintain texture and crispness, particularly in pickled vegetables and canned products.

## Regulatory status

| Country | Status |
| --- | --- |
| United States | approved |
| European Union | not_evaluated |
| United Kingdom | restricted |
| Canada | restricted |
| Australia | restricted |
| Japan | not_evaluated |
| South Korea | not_evaluated |
| Brazil | not_evaluated |
| China | not_evaluated |
| India | not_evaluated |

## Detailed analysis

## What is Alum?

Alum refers to a class of chemical compounds with the general formula M₂SO₄·Al₂(SO₄)₃·24H₂O, where M represents ammonium (NH₄), potassium (K), or sodium (Na). The most commonly used form in food production is potassium alum. These double sulfate salts are crystalline compounds that have been used in food processing for centuries, with documented culinary applications dating back to ancient times.

## Common Uses

Alum functions primarily as a firming agent in food manufacturing. Its most widespread applications include:

- Pickling of vegetables (cucumbers, peppers, onions) to maintain crispness and prevent softening
- Canned vegetable processing to preserve texture
- Traditional food preparation in various global cuisines

The mechanism by which alum firms foods involves its interaction with pectin in plant cell walls, cross-linking and strengthening the cellular structure. This prevents the breakdown of cell walls during cooking or storage, maintaining the desired texture of the finished product.

## Safety Assessment

Alum has a long history of use in food systems across multiple countries and cultures. The FDA has recorded zero adverse events associated with alum consumption and zero product recalls linked to this additive. However, it is important to note that alum does not currently hold GRAS (Generally Recognized as Safe) status in the United States, which distinguishes it from many other food additives.

The absence of GRAS status does not indicate a safety concern; rather, it reflects the regulatory pathway and historical approval status in different jurisdictions. Some countries classify alum-containing food additives under specific authorization frameworks rather than general recognition categories.

The primary area of scientific inquiry regarding alum has centered on aluminum exposure. When used as a food additive, alum contributes to dietary aluminum intake. The World Health Organization and various national food safety agencies have established acceptable daily intake levels for aluminum. Studies on dietary aluminum from food additives have generally found that exposure through food processing aids like alum remains within established safety guidelines when used at intended levels.

## Regulatory Status

Regulatory approval for alum varies internationally:

- **United States**: Not GRAS-approved for general food use; not currently permitted as a food additive at the federal level
- **European Union**: Approved as food additive E536 (potassium alum) and E530 (sodium alum) under specified conditions and maximum levels
- **Other jurisdictions**: Approved in many countries with specific usage limitations and maximum residue levels

The differing regulatory statuses reflect varying risk assessment approaches and historical precedent in different food safety systems. Manufacturers seeking to use alum must comply with regulations specific to their target markets.

## Key Studies

Scientific research on alum as a food additive has primarily focused on:

1. **Aluminum bioavailability**: Studies examining how much aluminum from alum-treated foods is absorbed by the human body, generally showing low absorption rates

2. **Texture preservation mechanisms**: Research elucidating the chemical and physical interactions between alum and plant cell wall components

3. **Comparative safety assessments**: Evaluations comparing aluminum exposure from food additives versus other dietary sources

The EFSA (European Food Safety Authority) conducted risk assessments on aluminum-containing additives, establishing that usage at approved levels poses minimal risk to consumer health. However, cumulative aluminum exposure from multiple sources requires consideration in a comprehensive dietary assessment.

## Sources

- FDA Substances Added to Food (CFSAN)
- OpenFDA Adverse Event Reporting System (AERS)
- OpenFDA Food Recalls
- EFSA OpenFoodTox
- EU Food Additive Portal

## Citation

Additive Facts. "Alum (double Sulfate Of Al And Nh4, K, Or Na) — Safety, regulation, and evidence." https://additivefacts.com/additives/alum-double-sulfate-of-al-and-nh4-k-or-na. Accessed 2026-05-19.