E174 is an ingredient listed in the European Food Additives List as E174 and in the Colour Index International as CI 77820. Its chemical name is Silver. It's used for coating food surfaces, decorating food, and in beverages. Similar to gold, silver is not synthesized but mined from the earth's crust. Silver is then purified and processed into the form needed for its intended use.

In the context of food additives, E174 is typically used in its metallic form, which is not synthesized but rather physically processed from naturally occurring silver. The silver is mined, refined, and then beaten into thin sheets or made into a powder.

The synthesis process takes place in different steps:

• Preparation of a silver nitrite (AgNO2) solution by dissolving silver nitrate (AgNO3) in water and adding nitrous acid (HNO2) to convert the nitrate to nitrite.
• Addition of a sodium chloride (NaCl) solution to the nitrite-silver agent, forming a silver chloride (AgCl) precipitate and releasing silver chloride (AgCl) into solution.
• Addition of sodium hydroxide (NaOH) to the solution containing silver chloride (I), forming a silver oxide (Ag2O) precipitate.
• Filtration and washing of the precipitate to remove any impurities.
• Drying of the silver oxide precipitate obtained.
• If necessary, the product undergoes further refining processes to obtain pure silver oxide.

What it is used for and where

Cosmetics

Colorant. This ingredient has the primary function of colouring the solution in which it is inserted in a temporary, semi-permanent or permanent manner, either alone or in the presence of the complementary components added for colouring.

Deodorant agent. When substances that give off an unpleasant odour are included in cosmetic formulations (typical examples are methyl mercaptan and hydrogen sulphide derived from garlic), deodorants attenuate or eliminate the unpleasant exhalation.

Skin conditioning agent - Miscellaneous.  This ingredient has the task of modifying the condition of the skin when it is damaged or dry by reducing its flakiness and restoring its elasticity.

Cosmetic safety

Restrictions IV/1 (Relevant entry in the Annexes of the European Cosmetics Regulation No 1223/2009) apply to this colouring agent 

EFSA's opinion on this ingredient:

Abstract. The present opinion deals with the re-evaluation of the safety of silver (E 174) when used as a food additive. Silver in food additive E 174 is present in its elemental form. The Panel noted that there are data gaps and concerns to be addressed to conduct a risk assessment with respect to the use of silver (E 174): lack of data on toxicity studies on elemental silver or the food additive (E 174); unknown particle size distribution of the food additive (E 174); evidence of the release of silver ions from elemental silver, which may be of concern. However, the extent of the release of the silver ions is unknown in the case of silver (E 174). The Panel concluded that the information available was insufficient to assess the safety of silver as food additive. The major issues included chemical identification an d characterisation of silver E 174 (e.g. quantity of nanoparticles and release of ionic silver) and similar information on the material used in the available toxicity studies. Therefore, the Panel concluded that the relevance of the available toxicological studies to the safety evaluation of silver as a food additive E 174 could not be established. The Panel recommended that the specifications for E 174 should include the mean particle size and particle size distribution (± SD), as well as the percentage (in number) of particles in the nanoscale (with at least one dimension below 100 nm), present in the powder form of silver (E 174) used as a food additive. The methodology applied should comply with the EFSA Guidance document, e.g. scanning electron microscopy (SEM) or transmission electron microscopy (TEM). The Panel recommended that additional data in line with the current Guidance document on evaluation of food additives would be required (1).

• Chemical name   Silver
• CAS: 7440-22-4
• Molecular Formula   Ag
• EC number 231-131-3
• DTXSID4024305
• UNII 3M4G523W1G
• MFCD00003397

Synonyms:

• Silver, colloidal
• Nanosilver
• Silver metal
• Silver powder
• Silver nanoparticles

References_____________________________________________________________________

(1) EFSA Panel on Food Additives and Nutrient Sources added to Food (ANS). (2016). Scientific opinion on the re‐evaluation of silver (E 174) as food additive. EFSA Journal, 14(1), 4364.