- 23/05/2026
- Posted by: Marta
- Category: Questions and answers
Dear Dongo lawyer,
I kindly ask you to elaborate on the uses of caustic soda (sodium hydroxide) in the food supply chain and its specific characteristics.
Thank you very much, [signed letter]
The lawyer Dario Dongo, Ph.D. in Agri-Food Systems, answers
Sodium hydroxide (also known as caustic soda) is used both as a technological adjuvant, in the food (1) and food contact materials sectors, both as food additiveIts main function in foods is to acidity regulator, to modify and stabilize the pH of foods so as to promote preservation, microbiological stability and technological functionality.
In the food sector, under Regulation (EC) No. 1333/2008, E 524 is used in the following product categories:
- jams, jellies, marmalades and fruit and vegetable creams (cat. 4.2.5.2 and 4.2.5.3), where the additive is authorised up to a maximum level of 10.000 mg/kg, calculated individually or in combination with other thickeners and gelling agents (E 400–E 404, E 406, E 407, E 410, E 412, E 415, E 418);
- bakery products such as pretzels and similar products (cat. 7.1 and 7.2), where the alkaline bath in E 524 solution contributes to obtaining the characteristic brown colour of the crust and the typical surface consistency; the additive is authorised quantum satis;
- fruit and vegetables in vinegar, oil or brine (cat. 4.2.2), including olives, where E 524 facilitates the softening of raw materials and the reduction of bitterness; in this context, caustic soda often acts as a technological adjuvant (preliminary alkaline leaching); its use as an additive is authorised quantum satis;
- cocoa and chocolate products governed by Directive 2000/36/EC (cat. 5.1);
- Dietary Supplements in solid, liquid and syrup or chewable form (cat. 17.1, 17.2 and 17.3), quantum satis.
Production and use of caustic soda as a food additive
General requirements
Il Regulation (EC) No. 1333/2008 (2) establishes rules relating to the production and marketing of food additives.
The general conditions for the use of food additives provide that – on the basis of available scientific data – their use does not pose safety concerns for the health of consumers, also taking into account other relevant legitimate factors including environmental factors. (3) Food additives must also comply with the specifications defined for them (see the next paragraph). (4)
The provisions of Titles II, V, VI and VII (5) of the REACH Regulation do not apply, to the extent that a substance is used in a food also in the form of a food additive. (6) Title IV (7) alone does not apply in the case of mixtures in the finished state, intended for the final user. (8)
The requirements of Regulation (EC) No 1272/08 (CLP – Classification, Labeling and Packaging of chemical substances and mixtures Regulation) in turn do not apply to chemicals used as foods, food ingredients and food additives. (9)
E 524: specifications and purity requirements
The sodium hydroxide (synonym: caustic soda), classified in the EU list with the code E524, is authorised for use as a food additive (10) in various product categories, under the conditions set out in Annex II to Regulation (EC) No 1333/08, as amended by Regulation (EU) No 1129/11. (11)
Regulation (EU) No 231/2012 (12) establishes the following requirements:
a) definition:
– EINECS: 215-185-5;
– chemical name and chemical formula: sodium hydroxide (NaOH);
– molecular weight: 40,0;
– Content: not less than 98,0% total alkali (as NaOH) in solid forms. Corresponding solution content, according to the percentage of NaOH declared or indicated on the label;
b) description:
– lumps, flakes, sticks, fused masses, or other forms, white or almost white in color. The solutions are clear or slightly cloudy, colorless or slightly colored, highly caustic and hygroscopic, and, when exposed to air, absorb carbon dioxide, forming sodium carbonate;
3) identification:
– sodium test: positive;
– pH: a 1% solution is strongly alkaline;
– Solubility: Very soluble in water. Easily soluble in ethanol;
4) purity:
– water-insoluble and organic matter: a 5% solution is perfectly clear and colorless to slightly colored;
– carbonates: not more than 0,5% (as Na2CO3);
– arsenic: no more than 3 mg/kg;
– lead: no more than 0,5 mg/kg;
– mercury: no more than 1 mg/kg.
Uses in dietary supplements and fortified foods
E 524 – sodium hydroxide has been introduced into the list of mineral substances that can be added in Dietary Supplements and in fortified foods, following the amendments to Annex II of Directive 2002/46/EC (13) and to Regulation (EC) No. 1925/2006 (14) introduced by Regulation (EC) No. 1170/2009. (15)
Purity criteria for mineral substances permitted for food supplements and foods should be defined by the Commission. Pending the definition of such criteria, the following shall apply: (16)
- the purity criteria prescribed by Union legislation for the use of such substances in the manufacture of foodstuffs for purposes other than those covered by the rules on food supplements or fortified foods (see previous paragraph); or, in the absence of such criteria;
- the generally acceptable purity requirements recommended by international bodies. (17)
In the absence of harmonized standards at European level, Member States may maintain national standards that establish more stringent purity requirements.
Materials and objects in contact with food
Regulation (EC) No. 1935/2004 – in defining the conditions for the production and placing on the market of materials and articles in contact with food (MOCA, or FCM – Food Contact Materials) (18) – provides for the possible adoption of specific measures for certain materials, including plastics. (19) These measures have been established by Regulation (EU) No. 10/2011, (20) to which MOCA made from recycled plastic produced pursuant to Regulation (EU) 2022/1616 must also comply. (21)
Regulation (EU) No 10/2011 provides for the possible use of caustic soda, or sodium hydroxide, as a polymerisation additive or aid (substance No 400). (22)
All MOCA must be manufactured in such a way as not to transfer their components to food products in quantities such as to a) constitute a danger to human health; b) cause an unacceptable change in the composition of food products; or c) cause a deterioration in their organoleptic characteristics. (23)
Substances used in the manufacture of plastic MOCA must also have a high degree of purity and a technical quality appropriate to the intended and foreseeable use. They are also subject to specific restrictions, which include compliance with both the specific migration limits (SML) from MOCA to food and the overall migration limits (OML) from MOCA to simulants, respectively. (24)
Available for any clarification or further information deemed useful,
Dario Dongo
Credit cover of Husband M
Note
(1) Processing aid: any substance which: (i) is not consumed as a food in itself; (ii) is intentionally used in the processing of raw materials, foods or their ingredients, to perform a specific technological function in the working or processing; (iii) may give rise to the unintentional but technically unavoidable presence of residues of that substance or its derivatives in the finished product, provided that these residues do not constitute a health risk and do not have technological effects on the finished product.
(2) Regulation (EC) No. 1333/2008 of the European Parliament and of the Council of 16 December 2008 on food additives. Consolidated text as of 18/02/2026: http://data.europa.eu/eli/reg/2008/1333/2026-02-18
(3) See art. 6, par. 1, letter. a) of the reg. (EC) n. 1333/2008.
(4) See Reg. (EC) n. 1333/2008, art. 4, par. 5 and art. 14.
(5) Title II: Registration of substances; Title V: Downstream users; Title VI: Evaluation; Title VII: Authorization.
(6) See art. 2, par. 5, letter. b) of the reg. (EC) n. 1272/2008.
(7) Title IV: Information within the supply chain.
(8) See art. 2, par. 6, letter. d) of the reg. (EC) n. 1272/2008.
(9) See art. 1, paragraph 5, letter e), point i) of Regulation (EC) No. 1272/2008.
(10) Food additive: any substance not normally consumed as a food in itself and not used as a characteristic ingredient of foods, with or without nutritional value, the intentional addition of which to foods for a technological purpose in the manufacture, processing, preparation, treatment, packaging, transport or storage of such foods results, or may reasonably be expected to result, in the substance or its by-products becoming, directly or indirectly, components of such foods.
(11) Commission Regulation (EU) No. 1129/2011 of 11 November 2011 amending Annex II to Regulation (EC) No. 1333/2008 of the European Parliament and of the Council by establishing a Union list of food additives. Consolidated text: 21/11/2013 http://data.europa.eu/eli/reg/2011/1129/2013-11-21
(12) Commission Regulation (EU) No. 231/2012 of 9 March 2012 laying down specifications for food additives listed in Annexes II and III to Regulation (EC) No. 1333/2008 of the European Parliament and of the Council. Consolidated text as of 09/05/2026: http://data.europa.eu/eli/reg/2012/231/2026-05-09
(13) Directive 2002/46/EC of the European Parliament and of the Council of 10 June 2002 on the approximation of the laws of the Member States relating to food supplements. Consolidated text as of 16/03/2025: http://data.europa.eu/eli/dir/2002/46/2025-03-16
(14) Regulation (EC) No. 1925/2006 of the European Parliament and of the Council of 20 December 2006 on the addition of vitamins and minerals and of certain other substances to foods. Consolidated text as of 17/07/2024: http://data.europa.eu/eli/reg/2006/1925/2024-07-17)
(15) Commission Regulation (EC) No 1170/2009 of 30 November 2009 amending Directive 2002/46/EC of the European Parliament and of the Council and Regulation (EC) No 1925/2006 of the European Parliament and of the Council as regards the lists of vitamins and minerals and their forms that may be added to foods, including food supplements. http://data.europa.eu/eli/reg/2009/1170/oj
(16) See art. 4, par. from 2 to 4 of Directive 2002/46/EC, and art. 5 of the reg. (EC) n. 1925/2006.
(17) As an example, Codex Alimentarius Guide CAC/GL 55 – 2005 indicates to refer to the purity criteria of other Codex standards (e.g. food additives), or of the International Pharmacopoeia or other recognized international standards.
(18) Regulation (EC) No. 1935/2004 of the European Parliament and of the Council of 27 October 2004 on materials and articles intended to come into contact with food and repealing Directives 80/590/EEC and 89/109/EEC. Consolidated text as of March 27, 2021: http://data.europa.eu/eli/reg/2004/1935/2021-03-27
(19) See art. 5 and Annex I of Regulation (EC) No. 1935/2004.
(20) Commission Regulation (EU) No. 10/2011 of 14 January 2011 on plastic materials and articles intended to come into contact with food. Consolidated text as of 16/03/2025: http://data.europa.eu/eli/reg/2011/10/2025-03-16
(21) Commission Regulation (EU) 2022/1616 of 15 September 2022 on recycled plastic materials and articles intended to come into contact with food and repealing Regulation (EC) No. 282/2008. Consolidated text as of 16/03/2025: http://data.europa.eu/eli/reg/2022/1616/2025-03-16)
(22) See Annex I, Table I of Regulation (EU) No 10/2011.
(23) See art. 3, par. 1 of the reg. (EC) n. 1935/2004.
(24) See art. 8, par. 1 and art. 9, par. 1 of the reg. (EU) no. 10/2011.
