Silicon dioxide is a food additive with many functional attributes.

Silicon Dioxide

Also known as synthetic amorphous silica (SAS)

What is Silicon Dioxide?

Silicon dioxide is a food additive with many functional attributes. It is used as an anticaking agent, coloring and flavor adjunct and antifoaming agent in many foods and  bakery products.1

Typically found as a white amorphous powder or granules, silicon dioxide is made up of one silicon atom covalently bonded to two oxygen atoms.1

Chemical Formula

Silicon Dioxide


Silicon is the most abundant mineral on earth and can be found naturally in many plants. Silicon dioxide is synthetically obtained from a vapor-phase hydrolysis reaction producing fumed silica. Another process to obtain synthetic amorphous silica is through a wet process to form hydrous silica. 2


This additive is used for several purposes in baked goods including:1

  • Anticaking agents: prevents agglomeration of baking powder, flour, starch, cocoa and other powder food ingredients.
  • Coloring adjunct: used as a coloring carrier.
  • Flavoring carrier: used as a flavoring carrier.
  • Defoaming agent: prevents undesirable foaming.
  • Thickener

Nutrition and Health

As a food additive, this doesn’t provide calories. Its safe upper level of consumption is 25 mg/kg of body weight per day. 2

Silicon dioxide is currently regarded as a safe food additive when used following the appropriate levels to obtain the desired effect on the food product, and never exceeding the 2% limit. However, authorities in the EU are reviewing potential hazardous effects of its nanoparticles.2

Commercial production

Silicon dioxide is produced through the following manufacturing processes:2

Thermal process

  1. Hydrolysis reaction: chlorosilanes are placed in an oxygen (air)/ hydrogen gas flame reactor 1000 oC (1832 oF)
  2. Agglomeration: pyrogenic silica agglomerates (1-250 µm) are formed inside the cooling system.
  3. Filtering: solid silica particles are separated from gas by filtering.
  4. De-acidification: to remove surface hydrochloric acid.
  5. Packaging

Wet process

  1. Precipitation reaction: dilute alkali metal silicate is mixed with a diluted acid in water to produce amorphous silica.
  2. Filtering: precipitated silica is filtered and washed to remove undesirable salts.
  3. Dehydration: water is removed from the silica.
  4. Milling: dried silica is milled to the appropriate size distribution.
  5. Packaging


Silicon dioxide is used in several food applications as well as in baked goods.

Typical  usage levels in food products:1

Food Product Usage Level Use Regulation
Fresh fruits and vegetables No more than 2% of the ink solids Color adjunct CFR Title 21 Part 173 Sec. 172.480
Grated cheese Maximum 2% Anticaking agent CFR Title 21 Part 173 Sec. 172.480
Powder egg Maximum 2% Anticaking agent CFR Title 21 Part 173 Sec. 172.480
Flavoring substances Maximum 2% Flavoring carrier CFR Title 21 Part 173 Sec. 172.480
Flour, baking powder Maximum 2% Anticaking agent CFR Title 21 Part 173 Sec. 172.480
Decorations and coating QS* Flavoring and coloring carrier Annex II of Regulation (EC) No 1333/2008
Sugars (powder) 10,000 mg/kg Anticaking agent Annex II of Regulation (EC) No 1333/2008

*QS: quantum satis, the amount enough to produce the desired effect.


Silicon dioxide is considered safe by the FDA when meeting conditions established in the CFR Title 21 Part 173 Sec. 172.480.3

In the EU, silicon dioxide (E 551) is considered a safe  food additive. However, recent concerns regarding the presence of nanoparticles has ignited a debate regarding its safe status.2


  1. Burdock, G. A.. Encyclopedia of Food and Color Additives. United Kingdom, CRC-Press, 1997.
  2. EFSA Panel on Food Additives and Nutrient Sources added to Food (ANS), et al. “Re‐evaluation of silicon dioxide (E 551) as a food additive.” EFSA Journal 16.1 (2018): e05088.
  3. U.S. Department of Health and Human Services.” Food Additives Permitted For Direct Addition To Food For Human Consumption.Title 21 Code of Federal Regulation, Part. 172. April  2019. Available at  . Accessed 17 October 2021.

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