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Silicone moulds can release unwanted chemicals into the food

This test of 18 different silicone baking molds shows, that they can release problematic chemicals into the food.

Lars Andresen og Katja Ravn · Foto: Benjamin Creative · 15. november 2022
Bageforme muffins

Silicone is practical and an obvious choice for ice cube trays, dough scrapers and baking molds for muffins, cakes, and cooking. Silicone is a material that can withstand heat, it is flexible, water- and grease repellant.

But silicone can contain various problematic chemicals that can migrate to the food when in contact with the silicone.

We have tested 18 silicone baking molds for unwanted chemicals released when you bake cupcakes or similar in the oven.

These chemicals in silicone are of high concern

Silicone can release various chemicals, especially if the material is not hardened sufficiently in production and is used at high temperatures. 

Silicone often also contains residues of a group of chemicals called cyclic siloxanes. These siloxanes can have several negative effects.

Some cyclic siloxanes are on the EU’s candidate list ofEU’s candidate list of substances of very high concern (SVHC), some are suspected of being endocrine disruptors and one of the cyclic siloxanes is also classified as suspected of classified as suspected of damaging fertility

In the test, we focused on three types of release of substances from the silicone molds. We have measured:

  • A total amount of volatile compounds released from baking molds.
  • Whether this release increases over time.
  • Whether particularly problematic substances are released – i.a. cyclic siloxanes.

9 silicone molds release larger amounts of chemicals

In our test, 9 out of 18 silicone molds receive the C-rating because they release larger amounts of chemicals and/or have a higher release of the problematic siloxanes.

Some of the chemicals we found are problematic substances to which we should  be exposed to as little as possible, and therefore we do not believe that they should either be in or released from products that are in direct contact with our food. Stine Müller, Test manager at the Danish Consumer Council THINK Chemicals.

Out of these 9 baking molds, 5 of them were bought on the online marketplaces Aliexpress, Amazon and Wish. Therefore, we do not recommend buying baking molds and other kitchen equipment outside the EU.

Increasing release of chemicals

The silicone molds have been tested three times to find out if the release of chemicals decreases or increases over time.

If the release increases, it indicates that the material is not stable and the baking form is not suited for repeated use. There is a risk that it will release more and more chemicals into the food over time.

For most baking molds in the test, the release decreases over time, but for some we found that the release of chemicals increases from the first to the third test.

The individual silicone mold is not a problem

The release of chemicals from the individual baking mold is not in itself harmful to health.

It is our overall exposure to the unwanted chemicals over long periods of time which can affect our health. This is called the cocktail effect.

7 tips for silicone baking forms

  • Buy the silicone baking molds from Danish retailers instead of online marketplaces or retailers, of unknown origin.
  • Choose products where the indication of maximum temperature is clear and written directly on the product. Then you always have the information at hand when using the product. If the information is only on the accompanying note, the information is easily misplaced or forgotten.
  • Make sure that the silicone molds are designed for the temperature that you will need and follow these temperature limits.
  • Before baking for the first time wash the baking mould and heat it for a few hours in the oven at 200 degrees with no contents. Preheating can reduce the amount of substances released to the food when the product afterwards is used for baking.
  • Avoid placing the silicone molds very close to the sides or top of the oven.
  • Dispose the baking molds when they clearly appear worn out.

No specific rules for silicone

For all materials intended for food contact, a general rule applies that they must not release substances in quantities that are harmful to human health.

However, there is no specific legislation in the EU or in Denmark which limits the release of specific substances from silicone intended for food contact.

“It would be easier for everyone if there were specific rules for all types of materials. The EU Commission has just started to revise the legislation, and the expectation is that the rules for chemical substances in food contact materials will become more uniform across the different types of materials in the future," says Mette Holm, chief consultant at the Danish Food and Drug Administration.

At the Danish Consumer Council, we stress that the cocktail effect must also be considered when the safety of substances that are in contact with food is assessed and that the most problematic substances are banned in food contact materials.

“It is not enough to just consider whether the release of a chemical you are exposed to, is harmful to you, when you are eating a muffin baked in a silicone form.Th  actual exposure is probably relatively small and thus in it self safe. However,  we are exposed to problematic substances from many different sources day in and day out, which means that the total chemical exposure increases andbecomes problematic, says Test manager Stine Müller and continues:

“We are working for the introduction of specific requirements for all types of materials intended for food contact – including silicone. Our tests and studies show that it is possible to make kitchen equipment such as silicone baking molds without consumers being exposed neither to higher amounts of chemicals nor to particularly problematic chemicals. This means that chemicals of very high concern should be banned in kitchen equipment and food packaging”. Stine Müller Test manager, Consumer Council Think Chemicals.

Facts about food contact materials

Not only silicone baking molds and other silicone products for food are not regulated by specific EU rules. This also applies to e.g. ceramics and food contact materials made of cardboard and paper. We have tested paper and cardboard for food contact several times and have found problematic chemicals.

However, for cardboard and paper packaging in Denmark there is since 2020 a national ban on fluorine substances, better known as PFAS. But this does not apply in other EU countries and does not include other substances in paper and board either.

About the test

  • This test is a collaboration between the Danish Consumer Council THINK Chemicals and other European Consumer Organizations within ICRT (International Consumer Research and Testing).

    The silicone molds are selected jointly among the partners of the test and the focus is on international brands and retailers. It includes products from several webshops such as Wish, Amazon and Aliexpress.

    The products in the test was sent to a laboratory, where the various baking molds were tested for the release of chemicals..

    The molds were filled with 50% ethanol, which is used to simulate fatty foods such as cakes.

    After 8 hours at 100 degrees celcius, we examined to which extent the forms  released chemicals and also which chemicals were released.

    We repeated the test three times for each baking form to determine whether the release of chemicals from the product increases as the product is repeatedly used.

    The test focused on three different sub-results:

    • The total amount of volatile compounds released from the baking molds.
    • Whether this release increases over time.
    • Whether particularly problematic substances are released - i.a. cyclic siloxanes.
  • We have tested 18 silicone baking molds from the Danish market. Out of the 18 silicone molds tested:

    • 5 baking molds receive the best chemical rating, the A-rating, because they do not release chemicals in the test, or only to a very small extent.
    • 4 baking molds receive the medium chemical rating, the B-rating, because they release smaller amounts of problematic siloxanes.
    • 9 baking molds receive the lowest chemical rating, the C-rating, because they release higher and, in some cases, increasing amounts of chemicals and/or have higher releases of problematic siloxanes.

    Total release

    The test shows that silicone baking molds can release chemicals when heated.

    In some cases, there is a visible release in the form of color or other fragments that makes the foodsimulant used in the test colored or cloudy after the test.

    In several cases, the tested baking molds therefore release substances into the food that is prepared in silicone forms and which we then eat.

    Some products have significantly higher overall release of volatile chemicals compared to the best products in the test, which are largely free of release.

    Overall, the release of chemicals from kitchen equipment and tableware should be limited as much as possible, which is why we give the products with a relatively high total release of volatile compounds (above 30 mg per kg) the C-rating.

    5 of the 9 products where  a higher release is measured were purchased on online platforms.

    In the overall European test, 16 out of a total of 44 products receive the C-rating because they have a relatively high total release of volatile compounds or they release substances where no safe limit for release in plastic has been established.

    The release increases over time

    Release of chemicals from plastics intended for food contact must not increase over time. The same principle should apply to silicone to avoid insufficient stability of the silicone material. We have used this requirement in our assessment of the products.

    For the vast majority of the tested products, the release of substances decreases from the first to the third test.

    However, in three of the tested products from the Danish market, the migration (or release) increases significantly from the first to the third test. Thus,  they all receive the C-rating.

    Release of particularly problematic siloxanes

    Several baking molds release a certain type of silicone substances, called cyclic siloxanes D4, D5 and D6, which are particularly problematic.

    These chemicals are listed on the EU’s candidate list of particularly problematic substances/substances of very high concern (SVHC). D4 is classified as suspected to of damaging fertility, and D5 is also suspected of being an endocrine disruptor.

    Silicone must meet the general requirement in the EU: food contact materials must not release substances in quantities considered harmful to health.

    But there are no rules for the release of specific substances such as the problematic siloxanes from silicone products.

    In a control project from 2016, the Danish Food and Food Administration used an action value for the release of D4-D8 of 1.5 milligrams per kilogram of food. The action value was health-based and determined by the Technical University of Denmark Food Institute based on toxicological studies of the substances.

    Several products in the test release cyclic siloxanes at levels above this proposed action limit. The test shows a release of D4-D8 of up to 4,8 milligrams per kilogram of food.

    Other substances

    The test also included a measurement of many other substances, including bisphenol A, primary aromatic amines, phthalates and other plasticizers, antioxidants, UV filters.

    In one of the Danish products, we saw the release of a suspected hormone-disrupting substance, ethyl hexyl salicylate. This product receive the B-rating.

    There were no release of either phthalates, primary aromatic amines, or bisphenol A from the Danish products.

    In the overall European test, one mould released dibutyl phthalate in low levels and another mould released benzophenone, a UV-filter suspected of being endocrine disrupting.