definition:

The by-products after extracting iodine and mannitol from brown algae kelp or Sargassum. Its molecules consist of β-D-mannuronic acid (β-D-mannuronic, M) and α-L-guluronic acid ( α-L-guluronic, G) is connected by pressing the (1→4) key. It is a natural polysaccharide with the stability, solubility, viscosity and safety required for pharmaceutical excipients.

Physical and chemical properties:

Sodium alginate is white or light yellow powder, almost odorless and tasteless. Sodium alginate is soluble in water but insoluble in organic solvents such as ethanol, ether and chloroform. It is soluble in water into a viscous liquid, and the pH value of 1% aqueous solution is 6-8. When pH=6-9, the viscosity is stable, when heated to above 80 ℃, the viscosity will decrease. Sodium alginate is non-toxic, LD50>5000mg/kg. The effect of chelating agent on the properties of sodium alginate solution The chelating agent can complex the divalent ions in the system, so that the sodium alginate can be stabilized in the system.

1. Composition

Sodium alginate (C6H7O6Na)n is mainly composed of sodium salt of alginic acid, which is composed of β-D-mannuronic acid (M unit) and α-L-guluronic acid (G unit) relying on β-1,4- A copolymer composed of GM, MM and GG fragments in different proportions connected by glycosidic bonds. [3]

2. Molecular weight

The molecular weight of commercial sodium alginate is usually like polysaccharide, relatively dispersed. Therefore, the molecular weight of a sodium alginate usually represents the average of all molecules in the group. The most common ways to express molecular weight are number average molecular weight (Mn) and weight average molecular weight (Mw). In polydisperse molecular groups, usually Mw>Mn. The coefficient of Mw/Mn is the dispersion index, and the classic range of the index of sodium alginate commodity is 1.5～2.5. The most commonly used method for determining molecular weight is calculated based on internal viscosity and light scattering measurements.

3. Molecular formula

The molecular formula is (C6H7NaO6)x

4. pH value

Sodium alginate is slightly soluble in water and insoluble in most organic solvents. It dissolves in alkaline solution and makes the solution sticky. Sodium alginate powder becomes wet with water, and the hydration of the particles makes the surface sticky. The particles then quickly adhere to each other to form agglomerates, which slowly hydrate and dissolve completely. If the water contains other compounds that compete with alginate for hydration, sodium alginate is more difficult to dissolve in water. Sugar, starch or protein in the water will reduce the hydration rate of sodium alginate, and the mixing time must be extended. Salts of monovalent cations (such as NaCl) have a similar effect when the concentration is higher than 0.5%. The pH value of sodium alginate in a 1% distilled water solution is about 7.2.

5. Stability

Sodium alginate is hygroscopic, and the amount of water in equilibrium depends on the relative humidity. The dry sodium alginate is quite stable when stored at 25℃ and below in a well-sealed container. Sodium alginate solution is stable at pH 5-9. The degree of polymerization (DP) and molecular weight are directly related to the viscosity of the sodium alginate solution. The decrease in viscosity during storage can be used to estimate the degree of sodium alginate depolymerization. Sodium alginate with high degree of polymerization is not as stable as sodium alginate with low degree of polymerization. It is reported that sodium alginate can be hydrolyzed by proton catalysis, and the hydrolysis depends on time, pH and temperature. Propylene glycol alginate solution is stable at room temperature and at pH 3 to 4; when the pH is less than 2 or greater than 6, the viscosity will quickly decrease even at room temperature.

Application areas:

1. Application in food

Food grade sodium alginate

Sodium alginate is used as a stabilizer for ice cream instead of starch and gelatin. It can control the formation of ice crystals and improve the taste of ice cream. It can also stabilize mixed beverages such as sorbet, sherbet and frozen milk. Many dairy products, such as refined cheese, whipped cream, dried cheese, etc., use the stabilizing effect of sodium alginate to prevent the stickiness of food and packaging. It can be used as a cover for dairy accessories to stabilize it and prevent frosting The skin is cracked.

Sodium alginate is used as a thickener for salad (a kind of cold dish) sauce, pudding (a kind of dessert), jam, ketchup and canned products to improve the stability of the product and reduce liquid leakage.

The addition of sodium alginate in the production of dried noodles, vermicelli and rice noodles can improve the adhesion of the product structure, make it strong in tension, large in bending, and reduce the rate of broken ends, especially for the low gluten content of flour, the effect is more obvious. Adding sodium alginate to bread, cakes and other products can improve the uniformity and water retention of the internal tissue of the product, and extend the storage time. Adding to frozen dessert products can provide a thermal fusion protective layer, improve flavor escape, and improve the performance of melting point.

Sodium alginate can be made into various gel foods, maintains a good colloidal form, does not leak or shrink, and is suitable for frozen foods and artificial imitation foods. It can also be used to cover fruits, meat, poultry and aquatic products as a protective layer, without direct contact with the air, extending the storage time. It can also be used as a self-coagulating agent for bread icing, fillings, dessert coatings, canned foods, etc. It can maintain its original shape in high temperature, freezing and acidic media. It can also replace agar to make elastic, non-sticky, transparent crystal soft candy.

2. Application in pharmaceutical preparations

Sodium alginate has been included in the United States Pharmacopoeia as early as 1938. Alginic acid was included in the British Pharmacopoeia in 1963. Alginic acid is insoluble in water, but will swell when placed in water. Therefore, traditionally, sodium alginate is used as a binder for tablets, and alginic acid is used as a disintegrant for quick-release tablets. However, the effect of sodium alginate on tablet properties depends on the amount put in the prescription, and in some cases, sodium alginate can promote the disintegration of the tablet. Sodium alginate can be added during the granulation process, rather than in the form of powder after granulation, so the production process is simpler. Compared with the use of starch, the resulting tablets have greater mechanical strength.

Sodium alginate is also used in the production of suspensions, gels and concentrated emulsions based on fats and oils. Sodium alginate is used in some liquid medicines to enhance viscosity and improve the suspension of solids. Propylene glycol alginate can improve the stability of emulsions.

3. Application of printing and textile industry

Sodium alginate is used as a reactive dye paste in the printing and dyeing industry, which is superior to grain starch and other pastes. The printed textile has bright patterns, clear lines, high color yield, uniform color, and good permeability and plasticity. Seaweed gum is the best slurry for modern printing and dyeing industry. It has been widely used in the printing of cotton, wool, silk, nylon and other fabrics. It is especially suitable for the preparation of discharge printing slurry.

The Chinese textile sector uses alginate and starch to mix or replace starch to prepare warp sizing, which not only saves a lot of food, but also makes the warp fibers lint-free, friction-resistant, and has a low end-break rate, thereby improving the efficiency of weaving. Seaweed gum is effective on cotton fibers and synthetic fibers.

4. Application in the pharmaceutical industry

The PS type gastrointestinal double contrast barium sulfate preparation made of alginate sulfate dispersant has the characteristics of low viscosity, fine particle size, good wall adhesion and stable performance.

PSS is a kind of fucoidan diester sodium developed with alginic acid as raw material. It has the functions of anticoagulant, lowering blood lipid and lowering blood viscosity.

Using seaweed glue instead of rubber and plaster as a dental impression material is not only cheap and easy to operate, but also the printed tooth shape is more accurate.

Seaweed gum can also be used to produce various forms of hemostatic agents, including hemostatic sponge, hemostatic gauze, hemostatic film, scald gauze, spray hemostatic agent, etc.