Potassium Alginate CAS 9005-36- 1
Potassium Alginate is a water-soluble polysaccharide derived from brown seaweeds (Phaeophyceae), such as Laminaria and Macrocystis. It is a salt of alginic acid, a natural linear copolymer composed of (1,4)-linked β-D-mannuronic acid (M) and α-L-guluronic acid (G) residues. Potassium Alginate is widely used in various industries, including food, pharmaceutical, personal care, and industrial applications.
1.Chemical Structure and Properties
Molecular Formula: (C6H7KO6)n
Molecular Weight: Varies depending on the source and extraction process, typically ranging from 32,000 to 400,000 g/mol.
Appearance: White to yellowish-brown powder or granules
Solubility: Soluble in water, forming viscous solutions, Insoluble in organic solvents, such as alcohol, ether, and acetone.
pH Range: Neutral to slightly acidic (pH 5-8)
Thermal Stability: Stable up to 200°C, but can degrade at higher temperatures
A.Chemical Structure
Potassium Alginate is a linear polysaccharide composed of (1,4)-linked β-D-mannuronic acid (M) and α-L-guluronic acid (G) residues.
The chemical structure can be represented as:
[-β-D-mannuronate-(1,4)-α-L-guluronate-(1,4)-]n
The ratio and distribution of the M and G units within the polymer chain can vary depending on the source of the seaweed and the extraction/purification process. Typically, the M/G ratio ranges from 0.5 to 2.0, which influences the physicochemical properties of the Potassium Alginate.
B.Molecular Weight and Polydispersity
Potassium Alginate is a high-molecular-weight polymer, with typical molecular weights ranging from 32,000 to 400,000 g/mol. The molecular weight distribution is generally polydisperse, meaning the polymer chains have a range of different molecular weights. The polydispersity index (PDI) of Potassium Alginate can vary from around 1.5 to 3.0, indicating a relatively broad molecular weight distribution.
C.Solubility and Ionization
Potassium Alginate is readily soluble in water, forming viscous, colloidal solutions.The solubility is attributed to the ionization of the carboxyl groups on the uronic acid residues, which become deprotonated in aqueous environments. The degree of ionization and solubility of Potassium Alginate is influenced by the pH of the solution, with maximum solubility occurring in the neutral to slightly acidic range (pH 5-8). In acidic environments (pH < 5), the carboxyl groups can become protonated, leading to decreased solubility and potential precipitation of the polymer.
D.Rheological Properties
Potassium Alginate solutions exhibit shear-thinning (pseudoplastic) behavior, where the viscosity decreases with increasing shear rate.This non-Newtonian flow behavior is attributed to the alignment and disentanglement of the polymer chains under shear stress. The viscosity of Potassium Alginate solutions can be influenced by factors such as concentration, molecular weight, and the ratio of M to G units. Higher concentrations, higher molecular weights, and higher G-content generally result in increased solution viscosity.
E.Thermal Stability
Potassium Alginate is relatively stable at temperatures up to 200°C, making it suitable for various thermal processing applications. However, prolonged exposure to high temperatures (> 200°C) can lead to the degradation of the polymer, resulting in a reduction in molecular weight and changes in the physicochemical properties. The thermal stability of Potassium Alginate can be affected by factors such as pH, the presence of metal ions, and the specific processing conditions.
2.Functional Properties
Thickening and Stabilizing Agent: Potassium Alginate can increase the viscosity and improve the stability of aqueous systems.
Gel Formation: In the presence of divalent cations (e.g., calcium), Potassium Alginate can form firm, elastic gels through a process called “egg-box” gelation.
Emulsification and Suspension: Potassium Alginate can act as an emulsifier and suspending agent, stabilizing oil-in-water or water-in-oil emulsions.
Water Binding Capacity: Potassium Alginate can absorb and retain large amounts of water, making it useful as a moisture-retaining agent.
A.Thickening and Stabilizing Agent
Potassium Alginate is an effective thickening and stabilizing agent when dissolved in aqueous systems. The long, linear polymer chains of Potassium Alginate entangle and interact with each other, increasing the viscosity of the solution. This thickening ability allows Potassium Alginate to improve the texture, mouthfeel, and stability of various food, personal care, and industrial products.
The viscosity-enhancing properties of Potassium Alginate are influenced by factors such as concentration, molecular weight, and the ratio of mannuronic (M) to guluronic (G) acid units.
B.Gel Formation
Potassium Alginate has the ability to form firm, elastic gels in the presence of divalent cations, such as calcium (Ca2+) and strontium (Sr2+). The gelation process is based on the “egg-box” model, where the divalent cations interact with the guluronic acid (G) residues, forming junction zones that crosslink the polymer chains. The strength and properties of the Potassium Alginate gels are affected by factors like the M/G ratio, the type and concentration of the divalent cations, and the pH of the system.
Potassium Alginate gels are used in various applications, such as food texturizers, drug delivery systems, and wound dressings.
C.Emulsification and Suspension
Potassium Alginate can act as an effective emulsifier and suspending agent in both oil-in-water and water-in-oil emulsions. The long, flexible polymer chains of Potassium Alginate can adsorb at the oil-water interface, stabilizing the emulsion droplets and preventing their coalescence. Additionally, Potassium Alginate can increase the viscosity of the continuous phase, improving the suspension and stability of dispersed particles or oil droplets.
This emulsifying and suspending ability of Potassium Alginate is useful in formulating various food, cosmetic, and personal care products.
D.Water Binding Capacity
Potassium Alginate has a high water-binding capacity, allowing it to absorb and retain large amounts of water. This property is attributed to the hydrophilic nature of the polymer and the formation of hydrogen bonds between the water molecules and the carboxyl and hydroxyl groups of the alginate. The water-binding capacity of Potassium Alginate can be influenced by factors such as the molecular weight, the M/G ratio, and the degree of crosslinking. The water-retaining ability of Potassium Alginate makes it useful as a moisture-enhancing agent in various applications, such as personal care products, wound dressings, and agricultural formulations.
3.Applications
A.Food Industry Applications
a.Thickener and Stabilizer
Potassium Alginate is used as a thickening and stabilizing agent in a wide range of food products, such as dairy items (e.g., yogurt, ice cream), sauces, dressings, and batters. It helps in improving the texture, mouthfeel, and suspension stability of these food products.
b.Gelling Agent
Potassium Alginate can form firm, elastic gels in the presence of divalent cations, such as calcium. This gelation property is utilized in the production of jellies, jams, and various confectionery items.
c.Emulsifier and Fat Replacer
Potassium Alginate can act as an emulsifier, stabilizing oil-in-water emulsions in low-fat or fat-free food products. It can also be used as a fat replacer, providing a similar mouthfeel and texture to the original fat-containing product.
B.Pharmaceutical and Medical Applications
a.Tablet Binder and Disintegrant
Potassium Alginate is used as a binder in the formulation of solid dosage forms, such as tablets and capsules, to improve their mechanical strength and stability. It can also act as a disintegrant, facilitating the breakup of the tablet or capsule in the gastrointestinal tract.
b.Wound Dressing and Absorbent
Potassium Alginate-based wound dressings are used to manage exudating wounds, as the polymer can absorb and retain large amounts of wound fluid. The gel-forming ability of Potassium Alginate helps maintain a moist wound environment, which can promote healing.
c.Sustained-Release Matrix
Potassium Alginate can be used in the development of controlled-release or sustained-release drug delivery systems, where it forms a matrix that controls the release of the active pharmaceutical ingredient.
C.Personal Care and Cosmetic Applications
a.Viscosity Modifier and Stabilizer
Potassium Alginate is used as a viscosity modifier and stabilizer in various personal care products, such as lotions, creams, gels, and toothpastes. It helps in adjusting the rheological properties and improving the overall stability of these formulations.
b.Emulsifier and Suspending Agent
Potassium Alginate can act as an emulsifier and suspending agent in personal care products, stabilizing oil-in-water or water-in-oil emulsions. This helps in dispersing and suspending active ingredients or particulates in the final product.
D.Industrial Applications
a.Binding Agent
Potassium Alginate is used as a binding agent in ceramic, paint, and paper coating formulations, improving the cohesion and mechanical properties of the final products.
b.Flocculating and Suspending Agent
In wastewater treatment, Potassium Alginate can be used as a flocculating agent, helping to remove suspended solids and impurities. It can also act as a suspending agent, maintaining the stability of dispersed particles in various industrial processes.
c.Thickener and Stabilizer
Potassium Alginate is employed as a thickening and stabilizing agent in textile printing and dyeing processes, improving the viscosity and stability of the formulations.
4.Regulatory Status and Safety
A.Regulatory Status
a.Food Industry
Potassium Alginate is approved for use as a food additive (E-number: E402) in the European Union. It is generally recognized as safe (GRAS) by the U.S. Food and Drug Administration (FDA) for use as a direct food additive.
The Joint FAO/WHO Expert Committee on Food Additives (JECFA) has established an acceptable daily intake (ADI) of 0-30 mg/kg body weight for alginates, including Potassium Alginate.
b.Pharmaceutical and Medical
Potassium Alginate is included in the United States Pharmacopeia (USP) and the European Pharmacopoeia (Ph. Eur.) for pharmaceutical applications. It is recognized as a safe and suitable excipient in the development of various drug formulations, including tablets, capsules, and wound dressings.
c.Cosmetics and Personal Care
Potassium Alginate is permitted for use in cosmetic and personal care products in the European Union, the United States, and other major markets. It is listed as a safe and approved ingredient in cosmetic regulations and guidelines, such as the Cosmetic Ingredient Review (CIR) and the International Nomenclature of Cosmetic Ingredients (INCI).
B.Safety and Toxicology
a.Acute Toxicity
Potassium Alginate has a low order of acute toxicity when administered orally, dermally, or through inhalation. The reported LD50 (lethal dose, 50%) values in animal studies are generally high, indicating a wide margin of safety.
b.Chronic Toxicity and Carcinogenicity
Long-term studies in animals have not shown any significant toxic effects or carcinogenic potential associated with the consumption or exposure to Potassium Alginate.
c.Allergenicity and Irritation
Potassium Alginate is generally considered non-allergenic and non-irritating when used as per the recommended guidelines and dosages. However, in rare cases, some individuals may develop mild skin or respiratory irritation upon exposure to Potassium Alginate.
5.Manufacturing
Potassium Alginate is typically extracted from brown seaweeds through a series of chemical and physical processes.
The manufacturing process involves the extraction of alginic acid, followed by neutralization with potassium hydroxide to form the potassium salt.
A.Raw Material Sourcing
Potassium Alginate is primarily extracted from various species of brown seaweed (Phaeophyceae), such as Laminaria and Macrocystis.
The choice of seaweed species can influence the chemical and functional properties of the final Potassium Alginate product.
Seaweed harvesting is typically done from natural sources or from cultivated seaweed farms, depending on the availability and sustainability of the resources.
B.Extraction and Purification
a.Pretreatment
The harvested seaweed is typically washed, chopped, or ground to increase the surface area for the extraction process. Drying or dehydration steps may be included to reduce the moisture content of the raw material.
b.Extraction
The seaweed is treated with an alkaline solution, typically sodium carbonate or sodium hydroxide, to extract the alginic acid from the plant material. This process involves the dissolution of the alginic acid and the separation of the insoluble components, such as cellulose and proteins.
c.Precipitation and Purification
The extracted alginic acid is then precipitated by adding an acid, such as hydrochloric acid or sulfuric acid, to the solution. The precipitated alginic acid is collected and further purified through filtration, washing, and drying steps.
d.Conversion to Potassium Alginate
The purified alginic acid is then neutralized with potassium hydroxide to form the potassium salt of alginic acid, known as Potassium Alginate. This conversion is typically carried out in an aqueous solution, ensuring the complete conversion and forming a potassium alginate precipitate.
e.Final Processing
The Potassium Alginate precipitate is further purified, dried, and ground into a fine powder or granular form. Depending on the intended application, additional processing steps may be employed, such as sieving, blending, or the addition of anti-caking agents.
