An anti-caking agent is a substance added to food products to prevent the formation of lumps or clumps. They’re also known as anti-sticking, drying, dusting powders, release agents, and flow enhancers. These substances are used in powdered or granulated foods such as sugar, salt, spices, and powdered mixes. Common anti-caking agents include silicon dioxide, calcium silicate, and magnesium stearate. They work by absorbing moisture or coating the particles to prevent them from sticking together.
Functions of Anti-Caking Agents
Anti-caking agents are used primarily to prevent caking and enhance the flow of a product, as described below.
Preventing Caking
The anti-caking agent mechanism is different for amorphous vs. crystalline materials. The mechanism of an anti-caking agent might function by competing for water with host material, acting as a water barrier, eliminating surface friction, or inhibiting crystal growth.
Some anti-caking agents work by absorbing moisture from the surrounding environment. As moisture can contribute to clumping, these agents help to keep the powdered or granulated substance dry and free-flowing. Silicon dioxide, also known as silica, is a commonly used moisture-absorbing anti-caking agent.
Other anti-caking agents work by coating the particles in a thin layer that prevents them from sticking together. Calcium silicate is an agent that forms a protective coating on the particles.
Enhancing Flow
Powder flowability is more complex than that of fluid. It is affected by material properties and the stress history of the material during processing, internal factors such as particle size and distribution, and external factors such as air humidity and temperature. Anti-caking agents can act as free-flowing agents by reducing friction between particles, helping the substance to flow more efficiently so it’s easier to handle and use. The addition of anti-caking agents increases the flowing properties of the host powder. Magnesium stearate is an example of a flow enhancer used in the food industry.
Applications of Anti-Caking Agents
Anti-caking agents are used in a variety of different food products, as described in the table below:
| Category | Examples |
| Table Salts & Sweeteners | Salt, Salt Substitutes, Sugar Mixes, High-Intensity Sweeteners, Honey Powder, Powdered Sugar Syrups |
| Dairy Products & Dairy Alternates | Dairy Whiteners, Cheese Powder, Yogurt Powder, Milk Powder Analogs, Cheese Analogs |
| Beverages Products | Instant Coffee Powder, Flavored Beverage Mix Powders |
| Convenience | Powder Mixed, Ready-to-Cook Products, Cereal Products, Soup Mixes |
| Spices & Seasonings | Spice Powders, Blended Spices, Seasoning Powders, Condiments |
| Others | Powdered Flavors, Baking Powder, Yeast Extracts, Cocoa Powder |
Classification of Anti-Caking Agents
Anti-caking agents can be classified into two main categories: natural and synthetic. Both types of anti-caking agents serve the same purpose of preventing clumping in powdered or granular materials. The choice between natural and synthetic anti-caking agents may depend on cost, availability, and regulatory requirements.
Natural Anti-Caking Agents
Natural anti-caking agents are substances derived from natural sources, such as minerals or plants. These substances occur naturally in the environment and are generally considered safe for consumption, although regulatory requirements are just as stringent as those for synthetic agents. Some common natural anti-caking agents include rice flour, calcium carbonate, bentonite, magnesium carbonate, cellulose, and starch.
Synthetic Anti-Caking Agents
Synthetic anti-caking agents are substances that are chemically synthesized in a laboratory. They are designed to have similar properties to natural anti-caking agents and are often more economical to produce. These substances are typically regulated by food safety authorities to ensure their safety for consumption.
While these agents are generally considered safe for consumption, there have been concerns about their long-term effects on human health. As a result, there has been an increasing demand for natural alternatives to synthetic anti-caking agents. Some commonly used synthetic anti-caking agents include silicon dioxide (silica), calcium silicate, sodium aluminum silicate, potassium bicarbonate, sodium carbonate, potassium aluminum silicate, iron citrate, sodium ferrocyanide, and magnesium carbonate.
Properties of Commonly Used Anti-Caking Agents
| Anti-Caking Agent | Physicochemical Properties | Benefits and Limitations |
| Aluminum silicates, including sodium aluminum silicate, potassium aluminum silicate, calcium aluminum silicate, and aluminum silicate (kaolin) | Bentonite is a very soft plastic clay consisting predominantly of montmorillonite, a fine particle-sized hydrous aluminum silicate. It contains iron and magnesium as well as either sodium or calcium. The chemical composition diverges according to the type of bentonite samples. Sodium bentonite is a type of bentonite clay with swelling properties and swells to 8-15 times its dry size when water is added. It is insoluble in water and has strong colloidal properties with quick dispersion in water without creating any dust. The suspensions are thixotropic. – Density: 1.5 to 2.8 g/cm3 – Bulk Density: 0.8 to 1.2 g/cm3 – Appearance: very fine, homogeneous, greyish-white powder with a yellowish or pinkish tint – Average particle size: 20-100 mesh – Taste & Odor: Slight earthy, gritty, and a dry muddy taste, odorless – pH: 8.5-10 | – Aluminum silicate is relatively inexpensive compared to many other anti-caking materials. – Due to its highly porous structure, strong hygroscopicity, and ultra-high whiteness, it is widely used to substitute silica. – It can replace some whitening agents in the formulation. – Synthetic and natural aluminosilicates can be used as anti-caking agents. The minerals and zeolites of aluminum silicates have a defined structure (layered or microfibrous). This pre-organized structure produces a high specific surface area (50-800 m2/g), providing higher absorption ability. – It is generally regarded as nontoxic and nonirritating. – Aluminum silicate is generally unsuitable for acidic solutions below pH 3.5. |
| Bentonite | Bentonite is a very soft plastic clay consisting predominantly of montmorillonite, a fine particle-sized hydrous aluminum silicate. It contains iron and magnesium as well as either sodium or calcium. The chemical composition diverges according to the type of bentonite samples. Sodium bentonite is a type of bentonite clay with swelling properties and swells to 8-15 times its dry size when water is added. It is insoluble in water and has strong colloidal properties with quick dispersion in water without creating any dust. The suspensions are thixotropic in nature. – Density: 1.5 to 2.8 g/cm3 – Bulk Density: 0.8 to 1.2 g/cm3 – Appearance: very fine, homogeneous, greyish-white powder with a yellowish or pinkish tint – Average particle size: 20-100 mesh – Taste & Odor: Slight earthy, gritty, and a dry muddy taste, odorless – pH: 8.5-10 | – It is a naturally obtained clay (purified to eliminate unwanted materials). – Montmorillonite has high adsorption affinity for mycotoxins, bacteria, and heavy metals. It provides an advantage in this regard when used in a formulation. – It is also used as an ion exchange material, decolorizing agent, clarifying agent, and flocculating agent. – Bentonite is approved to be used only as a feed additive in the EU. It is generally recognized as a safe food substance in the US as per the FDA. |
| Carbonates of calcium, including calcium carbonate and calcium hydrogen carbonate (calcium bicarbonate) | Calcium carbonate, or chalk, is commonly found in rocks as the minerals calcite and aragonite, eggshells, gastropod shells, shellfish skeletons, and pearls. Calcium carbonate has three forms (anhydrous crystalline, hydrated crystalline, or amorphous powder) – Molecular Formula: CaCO3 – Molecular Weight: 100.0869 g/mol – Density: 2.71 g/cm3 – Bulk Density: 0.8 to 1.2 g/cm3Color: White – Appearance: White powder or colorless crystal – Solubility: Sparingly soluble in water – Average particle size: 0.2-30 μm – Taste & Odor: Chalky taste, odorless – pH: Basic (>8) | – It is available from both natural and synthetic origins. – It acts as an antacid and as a source of calcium when used in food formulations. – It can be added to foods for several purposes, functioning as an acidity regulator, food coloring, firming agent, stabilizer, and flour treatment agent. – Calcium carbonate can have water absorption capacity up to 1.7 g/g. |
| Carbonates of magnesium, including magnesium carbonate and magnesium (hydroxide carbonate) bicarbonate | Magnesium carbonate is an inorganic salt naturally found in the mineral magnesite. Magnesium carbonate and magnesium bicarbonate can be formed synthetically. Magnesium carbonate is available in anhydrous and hydrated forms. Molecular Formula: MgCO3 (Magnesium carbonate) – Molecular Weight: 84.3139 g/mol – Density: 2.96 g/cm3 – Bulk Density: 0.5 to 0.8 g/cm3 – Color: White – Appearance: White powder or colorless crystal – Solubility: Sparingly soluble in water – Average particle size: 0.2-30 μm – Taste & Odor: Earthy taste, odorless – pH: Basic (>8) | – It is available from both natural and synthetic origins. – It acts as an antacid and a calcium source when used in food formulations. It can be added to foods for several purposes, functioning as an acidity regulator, food coloring, firming agent, stabilizer, and flour treatment agent. – It has an excellent absorption capacity and can simultaneously take up oil and water. |
| Silicon dioxide (aka silica) | Silicon dioxide is an oxide of silicon. Fumed silica, or pyrogenic silica, consists of microscopic droplets of amorphous silica fused into branched, chainlike, three-dimensional secondary particles, agglomerating into tertiary particles. Silica comprises aggregates, typically of size greater than 100 nm, made of nanosized particles. Synthetic amorphous silica (SAS) include fumed silica and hydrated silica (precipitated silica, silica gel, and hydrous silica). Silica gel is a form of silica that’s processed into various forms like granules or beads. Silica gel works like a sponge, drawing moisture into its many pores. – Molecular Formula: SiO2 – Molecular Weight: 60.08 g/mol – Density: 2.648 g/cm3 – Bulk Density: 0.1 to 0.4 g/cm3 – Color: White to grey – Appearance: Powder – Solubility: Poorly soluble in water – Average particle size: <100 nm – Taste & Odor: Tasteless, odorless | – Silica has an extremely low bulk density and high surface area of ~ 50-400 m2/g and medium or large pore size (around 10-100 nm diameter. – Silica absorbs water through a process known as capillary condensation. Its three-dimensional structure results in viscosity-increasing, thixotropic behavior when used as a thickener or filler. – Silica gel exhibits an excellent capacity for water adsorption up to 35-40% of its dry mass. – Due to the high water adsorption capacity, silica is used in very minor quantities in food products. – Silica does not significantly affect the color or taste of food. – Due to its extremely low bulk density, amorphous silica is difficult to handle and may pose hazards due to inhalation. |
| Calcium silicate | Calcium silicate is an inorganic or anhydrous substance with varying proportions of calcium as calcium oxide and silicon as silicon dioxide. It can be obtained from naturally occurring limestone and diatomaceous earth or produced synthetically from silicon dioxide and calcium oxide with various ratios. – Molecular Formula: CaSiO3 or Ca2SiO4 – Density: 2.9 g/cm3 – Bulk Density: 0.12 to 0.15 g/cm3 – Color: White – pH: 7 – 10 – Appearance: Fine powder – Solubility: Insoluble in water – Average particle size: ~50 microns – Taste & Odor: Tasteless, odorless | – It is reported to absorb water at 2.5 times its weight to remove moisture from the host ingredient. – It can be obtained naturally as well as synthetically. – It does not significantly impact the odor or taste of food products. |
| Magnesium silicate | Magnesium silicate is a synthetic compound with a mole ratio of magnesium oxide to silicon dioxide, approximately 2:5. Its hydrated form is present naturally as soapstone as talk. The product must not contain asbestos. – Molecular Formula: Mg2SiO4 or Mg2(Si2O6) – Molecular Weight: 140 & 200 g/mol respectively – Density: 3.2 g/cm3 – Bulk Density: 0.3 to 0.6 g/cm3 – Color: Colorless – pH: 10±0.5 – Appearance: Fine powder or crystals – Solubility: Insoluble in water – Average particle size: ~50 microns – Taste & Odor: Tasteless, odorless | – It can be obtained naturally as well as synthetically. – The particles are very porous, and the surface area can vary from 100- 300 m2/g. – It does not significantly impact the odor or taste of food products. |
| Ferric ammonium citrate | Ferric ammonium citrate consists of iron III ions (Fe3+) and citrate ions (C6H5O73−) complexed together. It is synthesized by the reaction of ferric hydroxide with citric acid, followed by treatment with ammonium hydroxide. It is a complex salt of undetermined structure and occurs in two forms depending on the stoichiometry of the initial reactants. – Molecular Formula: C6H11FeNO7+3 – Molecular Weight: 265.00 g/mol – Density: 1.8 g/cm3 – Bulk Density: ~1.0 g/cm3 – Color: Reddish brown or garnet red or brownish yellow – pH: 6-8 (10% w/v) Appearance: Scales, granules, powder – Solubility: Readily soluble in water (1200 g/L) – Taste & Odor: Weak iron taste and slight ammonia odor | – It can interact with bases in a solution and is incompatible with string bases. – It is incompatible with potent oxidizing agents. – It is also a source of iron and can be used as a fortifier due to its stability and bioavailability. |
| Stearates, including magnesium stearate and calcium stearate | Magnesium and calcium stearates are metallic salts of stearic acid, which is a saturated fatty acid. Magnesium stearate helps prevent ingredients from sticking together and enables smoother and more consistent production processes. – Solubility: Insoluble in water – Taste & Odor: Mild odor, feels oily when touched – Appearance: Fine, light powder material that is practically white or close to white | – Magnesium and calcium stearates provide improvement in flowability even in low amounts. – They also act as a lubricant and release agent in formulations. |
| Ferrocyanides, including sodium ferrocyanide, potassium ferrocyanide, and calcium ferrocyanide | Ferrocyanides are inorganic compounds with coordination complex [Fe(CN)₆]⁴⁻. These salts are available in anhydrous forms as well as hydrates. They are freely soluble in water. | – Ferrocyanides effectively block the growth of sodium chloride crystals, thereby preventing them from agglomerating and caking. – Rerrocyanides are less toxic than many salts of cyanide because they tend not to release free cyanide. |
| Phosphates, including tricalcium phosphate and trimagnesium phosphate | Tricalcium phosphate is a chalky, fine, white powder that can absorb 10% of its overall mass in moisture. Because moisture causes mixes to clump, this water absorption feature keeps mixes flowing freely. It is commercially produced from phosphoric acid, which is obtained from a phosphate mine. | – As a hygroscopic substance, tricalcium and trimagnesium phosphate can attract and hold onto water molecules from the surrounding environment. – This property helps to keep the particles in the food product dry and separate, preventing them from sticking together and forming clumps. |
Plant-based Food Ingredients as Anti-Caking Agents
| Anti-Caking Agent | Physicochemical Properties | Benefits & Drawbacks |
| Starches, including rice starch, corn starch, potato starch, and tapioca starch | Starches can absorb moisture, which helps prevent clumping and caking of powdered or granulated substances and improve flowability. The water absorption capacity of starch ranges from 2.42–3.35 g/g. Starches have a low bulk density of <0.8 g/cc. Starches have a fine and powdery texture and white to off-white color. | – Starches are derived from plants and are considered natural and safe for consumption. – Starches are relatively inexpensive and easily available. – Native starches are considered clean-label ingredients as they are easily recognizable by consumers. – They can affect food products’ overall texture, color, and taste. The effect can be desirable or undesirable. |
| Flours, including rice flour, wheat flour, and millet flours | Flours can be good anti-caking agents because they have a low moisture content and absorb moisture from the environment. | – Flours are whole food ingredients obtained from seeds or grains with minimal processing. – They are label-friendly options for synthetic anti-caking agents. – They may negatively affect the color and taste of the product, dilute the flavors, and impact the product’s mouthfeel. For this reason, their use as anti-caking agents is limited. |
| Cellulose & modified cellulose products | – Cellulose is a type of fiber derived from plants and has a high capacity to hold water. – Cellulose has a fine, powdery texture, which helps to prevent particles from sticking together. The small particles of cellulose can create a barrier between the particles of the powdered substance, reducing the chances of caking or clumping. | – Cellulose can be a good plant-based alternative to anti-caking agents. – It increases the product’s fiber content and adds to the bulk of the product. – Although it has no significant taste of its own, it may dilute the taste of food products. – Modified cellulose products are approved food additives with E numbers. |
Advantages and Disadvantages of Using Plant-Based Anti-Caking Agents
There are several advantages to using plant-based natural ingredients as anti-caking agents:
- Natural and Clean Label: Plant-based ingredients are often viewed as more natural and clean-label friendly than synthetic or chemical additives. They are typically derived from real food sources and are minimally processed.
- Healthier Alternative: Many plant-based ingredients used as anti-caking agents are also rich in nutrients and health-promoting compounds. For example, rice flour is a common plant-based anti-caking agent that adds fiber and other beneficial components to food products.
- Wide Availability: Some plant-based ingredients are readily available and widely used in the food industry.
There are also several disadvantages to using plant-based ingredients as anti-caking agents:
- Limited Effectiveness: Plant-based anti-caking ingredients may be less effective than synthetic or mineral-based anti-caking agents. They may not have the same ability to prevent clumping and maintain the free-flowing nature of powdered or granulated products.
- Flavor and Aroma: Some plant-based ingredients may have strong flavors or aromas that can impact the taste and scent of the final product. This can be undesirable in certain applications with a desired neutral taste or scent.
- Dietary Restrictions: Plant-based anti-caking agents can be calorie-dense. Usage of these agents can increase the caloric output of the food product.
- Less Stability: Plant-based ingredients may be less stable than synthetic or mineral-based anti-caking agents. They may degrade or lose effectiveness, especially when exposed to moisture or certain environmental conditions.
- Allergen Concerns: Plant-based ingredients may pose allergen concerns for consumers with certain food allergies or dietary restrictions. For example, ingredients derived from soy, wheat, or nuts can trigger allergic reactions in sensitive individuals.
Formulation Considerations
There are several critical properties that anti-caking agents must possess to be effective, as described in the table below:
| Moisture Absorption Capacity | Anti-caking agents should be chemically inert and not react with other ingredients in the product. This ensures that the anti-caking agent does not affect the product’s taste, aroma, or overall quality. |
| Stability | Anti-caking agents should be stable to processing conditions. They should not lose efficiency in harsh food processing conditions. |
| Chemical Reactivity | Anti-caking agents should be safe for consumption and comply with regulatory standards for food additives. They should not pose any health risks or adversely affect human health. |
| Compatibility | Anti-caking agents should be compatible with the other ingredients in the product, including any additives or flavorings. This ensures that they do not interfere with the functionality or performance of other ingredients. |
| Food Safety | Anti-caking agents should be economically viable and cost-effective for manufacturers to use in their products. This allows for the production of high-quality products at a reasonable cost. |
| Easy Dispersibility | Anti-caking agents should be easily dispersible in the product, allowing for uniform distribution and effective anti-caking action. This ensures that the anti-caking agent is evenly distributed throughout the product, preventing clumping in all areas. |
| Cost-Effectiveness | Anti-Caking agents should be economically viable and cost-effective for manufacturers to use in their products. This allows for the production of high-quality products at a reasonable cost. |
Clean Label Friendliness
Clean-label anti-caking agents refer to natural or minimally processed substances that are used as anti-caking agents in food and other products. These agents are preferred by consumers looking for clean and natural ingredients in their food and want to avoid artificial additives. Clean-label anti-caking agents may or may not provide similar anti-caking properties as their synthetic counterparts but are considered more natural and less processed, so the tradeoff is often considered worthwhile.
Identification Numbers of Common Anti-Caking Agents
| Anti-Caking Agent | CAS Number | EC Number | E Number |
| Aluminum Silicates | 12141-46-7 | 934-756-6 | E554 Sodium aluminum silicate, E555 Potassium aluminum silicate, E556 Calcium aluminum silicate, E559 Aluminum silicate (kaolin) |
| BentoniteSodium Bentonite | 1302-78-9 | 215-108-5 | E 558 |
| Calcium Carbonate | 471-34-1 | 207-439-9 | E 170 (i) |
| Magnesium Carbonate | 546-93-0 | 208-915-9 | E 504 (i) |
| Magnesium Bicarbonate | 144-55-8 | 218-240-1 | E 504 (ii) |
| Silica | 7631-86-9 (silica)112945-52-5 (pyrogenic silica)112696-00-8 (hydrated silica) | 231-545-4 | E 551 |
| Calcium Silicate | 1344-95-2 | 235-336-9 | E 552 |
| Magnesium Silicate | 1343-88-0 | 238-877-9 | E 553 |
| Iron Ammonium Citrate | 1185-57-5 | 214-686-6 | E 381 |
| Sodium Ferrocyanide | 13601-19-9 | 237-081-9 | E 535 |
| Potassium Ferrocyanide | 13943-58-3 | 237-323-3 | E 536 |
| Calcium Ferrocyanide | 1327-39-5 | 237-508-9 | E 538 |
| Magnesium Stearate | 557-04-0 | 209-150-3 | E 572 |
| Calcium Stearate | 1592-23-0 | 216-472-8 | E 470 |
| Tricalcium Phosphate | 7758-87-4 | 231-840-8 | E 341 |
| Trimagnesium Phosphate | 7757-87-1 | 231-824-0 | E 343 |
| Anti-Caking Agent | Permitted Categories | Usage Limit | ADI |
| Aluminum Silicates | Multiple food categories, including beverage mixes, chewing gum, milk powder, salt, seasonings, etc. as per the GSFA provision. Permitted in titanium oxide and iron oxide as well as vitamin preparations as per the commission regulation by the EU. | A PTWI (Provisional tolerable weekly intake) of 2 mg/kg bw for total aluminum was established by the JECFA. The PTWI applies to all aluminum compounds in food. | Undefined |
| BentoniteSodium Bentonite | No exceptions. | No limitations as per the FDA. | Not limited |
| Calcium Carbonate | Multiple food categories as per the GSFA. | No limitations as per the FDA. | Not limited |
| Magnesium Carbonate | Multiple food categories as per the GSFA. | No limitations set by the FDA. | Not limited |
| Magnesium Bicarbonate | Multiple food categories as per the GSFA. | Not limited | |
| Silica | Multiple food categories as per the GSFA. | The usage should not exceed 2 percent by weight of the food as per the FDA. | Not limited |
| Calcium Silicate | Multiple food categories as per the GSFA.Permitted for use in table salt and baking powder as per the FDA. | The usage should not exceed 2% in table salt and 5% in baking powder as per the FDA. | Not limited |
| Magnesium Silicate | Multiple food categories as per the GSFA. | Usage should not exceed 2% as per the FDA. | Not limited |
| Iron Ammonium Citrate | Edible salt. | Maximum dosage of 25 ppm in edible salt as per the FDA. Maximum 10 mg/kg in concentrated flavored drinks as per the GSFA. | Group PMTDI 0.8 mg/kg bw |
| Sodium Ferrocyanide | Salt, salt substitutes, seasonings & crystal salt. | Maximum 13 ppm in salt as per the FDA. Maximum 14 ppm in salts, 20 ppm in salt substitutes and 20 ppm seasonings as per GSFA. | 0-0.025 mg/kg body weight |
| Potassium Ferrocyanide | Salt, salt substitutes, seasonings & crystal salt. | Maximum 14 ppm in salts, 20 ppm in salt substitutes and 20 ppm seasonings as per GSFA. | 0-0.025 mg/kg bw |
| Calcium Ferrocyanide | Salt, salt substitutes, seasonings & crystal salt. | Maximum 14 ppm in salts, 20 ppm in salt substitutes and 20 ppm seasonings as per GSFA | 0-0.025 mg/kg bw |
| Magnesium Stearate | No exceptions. | Not to exceed current good manufacturing practice as per the FDA. | Not specified |
| Calcium Stearate | No exceptions. | Not to exceed current good manufacturing practice as per the FDA | Not specified |
| Tricalcium Phosphate | No exceptions. | Not to exceed current good manufacturing practice as per the FDA. | Group MTDI for phosphorus 70 mg/kg bw |
| Trimagnesium Phosphate | No exceptions. | Not to exceed current good manufacturing practice as per the FDA. | Group MTDI for phosphorus 70 mg/kg bw |
