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Home / News / Industry News / What Is the Silicone Antifoaming Agent Used in Food? A Practical Guide
Industry News
A silicone antifoaming agent used in food is a food-grade processing aid based on polydimethylsiloxane (PDMS), formulated as a stable emulsion with permitted emulsifiers and often fine silica. It is dosed into liquids that come into contact with food processing equipment to prevent and destroy foam, especially in continuous production lines where pump cavitation, overflow, or inaccurate filling can disrupt output.
Foam in food processing is not just an aesthetic problem. It slows heating and cooling, reduces product volume, causes splash and waste, and can leave protein soil behind after cleaning. Because silicone defoamers work at low concentrations, they are one of the most efficient foam-control tools available.
What It Is
A silicone-based emulsion that weakens the surface film around gas bubbles, allowing liquid to drain and bubbles to coalesce and escape.
How It Is Added
Directly into the process stream through a dosing pump, or pre-blended with a water-soluble carrier before high-shear mixing.
Why It Is Used
To keep production lines stable, reduce product loss, and maintain consistent texture and quality in foods where bubble entrapment would be visible.
What Is Inside a Food-Grade Silicone Antifoamer?
Polydimethylsiloxane is a linear polymer with a backbone made of alternating silicon and oxygen atoms. Each silicon atom also carries two methyl groups. This structure gives the polymer a very low surface tension, good spreading behaviour, and strong resistance to oxidation and heat. It is not digested by microorganisms in the same way as oil-based materials, which is exactly why it can keep knocking foam down for hours.
The emulsion form is usually white and pourable. It contains tiny PDMS droplets stabilized by food-approved emulsifiers. Some grades include a small amount of hydrophobic silica, which helps the droplet enter the bubble film more quickly.
| Parameter | Typical Range | Effect on Performance |
|---|---|---|
| Active PDMS content | 5–40% | Higher active content often means lower use level |
| Viscosity at 25°C | 200–5,000 mPa·s | A thicker emulsion may need a larger drop size and more shear to disperse |
| pH | 6.5–8.0 | Stable in most food liquids; extreme conditions may require an acid- or alkali-stable grade |
| Density | 0.95–1.02 g/cm3 | Affects mixing and settlement behaviour |
| Heat stability | Stable up to 150°C | Needed for boiling, frying, retorting, and high-temperature washing |
| Foam knockdown time | Typically under 30 seconds at 100 ppm | Shorter time improves fast-moving filling lines |
How Does a Silicone Antifoaming Agent Destroy Foam?
Silicone defoamers work by entering the liquid film that surrounds each bubble. Because the defoamer has lower surface tension than water, it spreads over the surface and pushes the film outward. The film becomes thinner at that point until it cannot support the pressure difference between adjacent bubbles, so the bubble ruptures.
1
Contact
Droplets of PDMS reach the bubble surface by turbulent mixing or buoyancy.
2
Spreading
The droplet spreads across the liquid-air interface as a thin silicone film.
3
Dewetting
The water film is pulled away from the droplet, leaving a bare area.
4
Rupture
The weakened film breaks, and the small bubbles merge into larger ones that rise and disappear.
The same principle explains why silicone is fast. PDMS has a surface tension around 20–21 mN/m, while water is around 72 mN/m. The larger the difference, the stronger the driving force that pulls the defoamer across the film.
Foam Collapse Curve With and Without a Silicone Defoamer
In the example below, a silicone defoamer is added after the first minute. The grey line shows foam height continuing to rise, while the green line shows rapid collapse.
Illustrative data for a boiling 5% soy sauce solution at 100°C.
Where Is Silicone Antifoam Used in Food Production?
Silicone antifoams can be found in both primary processing and final product filling. Their ability to remain active in hot, acidic, or salty liquids makes them useful in a wider range of food operations than many organic defoamers.
| Application | What Causes Foam | Typical Starting Dose |
|---|---|---|
| Fruit and vegetable washing | Plant proteins, pectin, and detergent residues | 5–50 ppm |
| Juice and soft drink filling | Air entrainment and agglomeration | 10–100 ppm |
| Beer fermentation | CO2 release from yeast activity | 10–200 ppm |
| Dairy processing | Protein films are more elastic than soap foam | 50–300 ppm |
| Soup, sauce, and jam cooking | Protein and starch leach into the water | 100–500 ppm |
| Edible oil refining and frying | Water droplets in hot oil and oxidation products | 1–10 ppm in the oil |
| Sugar and starch evaporation | Dense viscous syrup with surface-active compounds | 50–200 ppm |
The dose is not a fixed specification. Start at the low end, observe the foam in the worst operating condition, and increase only when the foam depth or defect frequency comes back.
What Does "Food-Grade" Mean for a Silicone Antifoam?
Food-grade means that the entire formulation, not just the PDMS molecule, is made from components permitted in the country where the food is sold. The supplier should have a letter of compliance showing the applicable regulation and the maximum allowed use level.
United States Approval
FDA 21 CFR 173.340 covers defoaming agents of dimethylpolysiloxane for use in processing food. The additive may be present at a level not to exceed 10 ppm in the finished food.
European Union Approval
Dimethylpolysiloxane is listed as E900. Use levels are set in Regulation (EC) No 1333/2008 and purity criteria in Regulation (EU) No 231/2012. Quantities vary by food category.
Other Markets
Many global standards follow the Codex specifications, but national limits can differ. Always check the target market before launching a product.
Operating without a compliance letter is a common compliance risk. Food companies often ask for a product-specific declaration, a full list of ingredients, and the maximum use level. The supplier should also be able to identify the country-specific authorization number. If the supplier hesitates, treat that as a red flag.
For a silicone defoamer to be acceptable in food contact, the manufacturing site also needs good allergen management, microbial control, and traceability. This is why a coating-grade defoamer cannot simply be placed into a food line without a formal food-grade declaration.
Silicone Defoamer vs Non-Silicone Food-Grade Defoamer
Silicone and non-silicone defoamers are both available for food use. Silicone is usually the fastest and most heat-stable choice. Non-silicone options, such as mineral oil, vegetable oil, fatty acids, and wax esters, are used when the processor needs a material that is easier to biodegrade or wants to avoid potential silicone residues in the final product.
| Factor | Silicone Antifoam | Non-Silicone Antifoam |
|---|---|---|
| Foam knock-down speed | Very fast | Moderate |
| Persistence in process | High | Lower |
| Heat resistance | Up to 150°C or higher | Some products break down above 80–100°C |
| Effect on taste or odour | Generally none at ppm level | Can be more detectable |
| Biodegradability | Low | Generally higher |
| Typical use level | 5–300 ppm | 50–1,000 ppm or more |
| Best suited for | Hot, acidic, high-protein liquids with fast-paced filling | Gentler processes and lower-foam liquids |
The choice is also relevant in water-based coatings, inks, and adhesives. Formulators face the same kind of trade-off: silicone is excellent at breaking foam, but it can cause cratering or poor interlayer adhesion if the compatibility is not tested. Non-silicone defoamers such as DH2020 are often useful when a smoother surface is more important than extreme foam speed.
DH-2020 Silicone-Free Defoamer for Coatings and InksThis silicone-free defoamer offers rapid foam elimination and good surface leveling, making it a practical choice when silicone compatibility issues are a concern.View Product →
For a more detailed comparison of industrial-grade materials, see our guide on silicone defoamer versus non-silicone defoamer solutions.
How to Select a Silicone Antifoaming Agent for Your Process
The selection process starts with understanding the foam source and the environment where foam appears.
- Identify whether the foam is caused by protein, starch, saponins, or injected gas.
- Record the normal and maximum process temperature.
- Check the pH range and salt level of the liquid.
- Determine where the defoamer can be added so that it is well dispersed before the foam reaches the critical point.
- Make sure the dosage will stay below the regulatory maximum.
After checking these conditions, run a simple beaker test. Pour 100 ml of process liquid into a measuring cylinder, add a known amount of defoamer, shake or stir at the same speed, and record the foam height at 10 seconds and 5 minutes. Compare several concentrations before moving to a pilot trial.
| Foam Tendency | Examples | Starting Dose (active PDMS content basis) |
|---|---|---|
| Low | Clear juice, simple syrup, coffee | 5–50 ppm |
| Medium | Carbonated beverages, milk, brine | 50–200 ppm |
| High | Protein soups, pea starch, yeast broth | 200–500 ppm |
Another practical issue is that the defoamer should be added in a way that matches the process shear. If the liquid is cold and viscous, the emulsion may need to be diluted with water before dosing. If the process has a high-shear pump, adding before the pump will usually give better dispersion. Adding after a filter may create a concentrated layer that causes surface defects.
Lab Validation
Use a reproducible bottle test with the actual production water and raw material batch to see threshold behaviour.
Pilot Trial
Run the liquid through a pump, filter, heat exchanger, or filling head to check foam in the same shear conditions as production.
Production Check
Measure line speed, underfill rate, and residual foam in packaged food over 24 h.
In coatings and inks, the same logic applies. A defoamer must not only reduce foam during manufacturing; it should also stay stable in the container and disappear after the film is applied. Our silicone defoamer category covers water-based and solvent-based industrial grades for formulators who need foam control without unwanted side effects.
Silicone Defoamers Product Category OverviewThis category page covers silicone defoamers for water-based and solvent-based systems, highlighting their efficiency and the need to balance foam control with surface quality.View Product →Why Is Foam Still Present After Adding Silicone Antifoam?
Sometimes the defoamer is correctly chosen but the foam still returns. In most cases the problem is not chemistry, but adding the wrong form or adding it at the wrong point. Here are the most common reasons.
| Symptom | Likely Cause | Action |
|---|---|---|
| Little or no foam reduction | Over-emulsified product is not spreading | Use a more hydrophobic grade or add less shear during mixing |
| Foam collapses only for a few seconds | Defoamer is stripped from the tank by continuous bubbling | Switch to a higher active content or use continuous dosing |
| Foam is fine in the kettle but appears at the filling nozzle | Air is re-entrained after the defoamer has been diluted | Add a second dose at the pump inlet |
| Microfoam remains as small white bubbles | Droplets are too small to form a bridge | Increase droplet size of the emulsion or choose a coarser emulsion |
| Foam gets worse after adding more defoamer | Overdosing may stabilise the foam film | Run a dose-response curve and identify the optimum plateau |
One common myth is that more defoamer equals less foam. The dose-response curve often reaches a plateau, and beyond the plateau the extra silicone droplets act as nucleation sites for new microfoam. This is more common when the emulsion is over-agitated and the droplet size becomes too small.
If the problem appears only after a raw material or water source changes, check the water hardness and ionic strength first. Calcium and magnesium can affect the emulsion stability of some silicone antifoams. In a food plant, water quality can change seasonally, so the same dose that worked in winter may not be enough in summer.
Manufacturing Consistency and Supplier Qualification
A food processor should expect a silicone antifoam to behave the same way in every delivery. That requires control of the base PDMS viscosity, the emulsion droplet size, the active content, and the microbial quality of the water phase. Ask for a certificate of analysis with parameters such as viscosity, pH, active content, and microbial count.
If the product is intended for food use, the supplier should also provide a food-grade compliance letter that clearly names the country and regulation. If the supplier cannot provide this, do not use the product in food, regardless of how well it performs in the beaker test.
In our own production system, we test every defoamer batch for solid content, viscosity, pH, and foam-knockdown performance before it leaves the factory. For water-based paints and inks, this means the formulator can rely on the product to keep the production process stable while preserving flow, leveling, and film finish.
DH-2270S Water-Based Polyether Silicone DefoamerThis defoamer provides stable foam suppression across wide temperatures, wets substrates effectively, and is suited for water-based coatings, inks, and adhesives.View Product →
Food-grade approval is a separate requirement, but the disciplines of raw material traceability and batch control are the same.
Frequently Asked Questions
Is dimethylpolysiloxane allowed as a defoamer in food?
Yes, in many jurisdictions, dimethylpolysiloxane is an approved food additive when used as a processing aid. In the United States, FDA 21 CFR 173.340 permits it at not more than 10 ppm in food. In the EU, it is listed as E900 and permitted only under specific conditions. Always verify the current limit for the relevant food category.
Is a silicone antifoamer the same as food-grade silicone oil?
Not exactly. Silicone oil is the raw polymer. A food-grade antifoamer is a formulated emulsion that contains silicone oil, water, emulsifiers, and sometimes silica. The emulsifiers and additives also need to be suitable for food use.
Can I use a paint or coating defoamer in food?
No. Paint and coating defoamers are not formulated with food-compliant raw materials, and they may contain surfactants, solvents, or metal residues that are not permitted in food. Even if the chemical family is the same, only a product with an explicit food-grade declaration should be used.
Does silicone antifoam affect the sensory quality of food?
At authorised levels, food-grade silicone defoamers are generally considered odourless and tasteless. Overdosing or poor dispersion may lead to a slight oily mouthfeel, which is why the lowest effective dose is recommended.
Why is silicone more effective at high temperature than oil-based defoamers?
PDMS does not oxidise or hydrolyse easily at elevated temperature. Many vegetable-oil or wax emulsions lose their structure above 100°C, while a food-grade silicone emulsion can continue spreading until about 150°C.
Can silicone antifoam be used in clean-in-place systems?
Sometimes, but it is not always required. Silicone can be difficult to completely rinse away, so processors often use lower foam during CIP and a separate defoamer dose only in the process line. Test the carryover before final product inspection.
