June 17, 2024

Starch Derivatives: An Important Class of Polymers With Wide Industrial Applications

It is made by all green plants as an energy store in the form of starch granules. It is the most common carbohydrate in human diets as it is present in many staple foods like potatoes, wheat, rice and corn. Starch is insoluble in cold water and requires heat to dissolve and initiate its breakdown.

Modification of Native Starch
Though native starch possesses many useful properties, it has certain limitations like susceptibility to hydrolysis by acids or enzymes at higher temperatures. Therefore, chemical or physical modification is done to change its properties and make it suitable for various industrial applications. Some common methods used for starch modification are:

Physical Modification
Physical modification involves subjecting starch to processes like annealing, Starch Derivatives heat moisture treatment, irradiation etc. This changes the crystalline structure of starch granules without breaking chemical bonds. Annealing starch leads to increased gelatinization temperature and viscosity. Irradiated starch has improved stability against acids and enzymes.

Oxidation
Oxidation of starch increases its hydrophilicity by introducing carbonyl and carboxyl groups. This process is done using oxidizing agents like hypochlorite, chlorine gas, hydrogen peroxide etc. Oxidized starch has superior absorption and retention properties making it useful in pharmaceutical and cosmetic products. It also has better film-forming ability and freeze-thaw stability.

Acetylation and Esterification
In this process, hydroxyl groups of starch are substituted by esterification using acetic anhydride or other acid anhydrides. Acetylated starch is soluble in cold water and organic solvents. It finds application as sizing agent in textile industry and also as a thickening agent in foods. Etherification leads to formation of ethers by reaction of starch with sodium monochloroacetate, propylene oxide or ethylene oxide. This improves the thermal properties and stability against acids and enzymes.

Crosslinking
Crosslinking involves creation of covalent bonds between two or more starch polymer chains using crosslinking agents like phosphorous oxychloride or epichlorohydrin. Crosslinked starches have highly increased viscosity, better thermomechanical properties and resistance to shear, acids and enzymes. They are used as encapsulation agents, disintegrants in tablets and thickeners in foods and cosmetics.

Uses of Starch Derivatives in Industries

Paper Industry
In paper industry, starch derivatives are used at various stages of paper production. Oxidized and acetylated starches are primarily used as fillers and coatings to improve paper quality and increase its gloss, brightness and Printing properties. Starch helps in retention of fibers and pigments on paper surface. Derivatives also act as binders in the coating layer and provide strength to paper sheets.

Food Industry
Native and chemically modified starches are widely used as thickeners, stabilizers, emulsifiers and gelling agents in various food products. Acetylated starch is used to make instant puddings and soups. Crosslinked and oxidized varieties provide better stability against acids and shear stress in soups, baked goods and sauces. Starch also improves organoleptic and textural properties of foods.

Textile Industry
Starch derivatives help in sizing of fabrics during weaving process. Sizing formulations containing starch provide strength, luster and body to fabrics. Oxidized and hydroxyethyl starches act as effective warp sizes. Acetylated starch finds application in mercerization of cotton fabrics as it lubricates fibers during this process. Starch also helps improve appearances of printed fabrics.

Paperboard Industry
Highly substituted starches are used as coatings for paperboards which are used in production of folding paper boxes, milk cartons, ice cream cartons, etc. Starch acts as an adhesive to bind coating pigments to paperboard surface. It improves printing properties, ink receptivity and surface strength. Oxidized and crosslinked starches are preferred for their good binding ability and water resistance.

Adhesives Industry
Starches are key ingredients in formulation of many adhesives. Oxidized and acetylated starches are used as adhesives for wood, paper and packaging applications due to their film forming and bonding abilities. Cold-water soluble starches can be used for non-permanent adhesives. Crosslinked and cationic starches impart permanent adhesive characteristics suitable for furniture, footwear, corrugated boards and construction works.

Pharmaceutical Industry
Starch derivatives find applications as disintegrants, binders and coating agents in solid oral dosage forms like tablets. Crosslinked starches are prominent disintegrants that facilitate breakup of tablets/capsule contents in gastrointestinal fluids. Their porous structure absorbs water which helps disintegration. Oxidized and hydroxyethyl derivatives act as binders, fillers and capsules coating agents.

Cosmetic Industry
In cosmetics, derivatives are used as binders, viscosity control agents and film formers. Acetylated starch acts as a soft film former in lotions and creams. Hydroxyethyl starch helps improve stability of oil-water emulsions. Crosslinked starch maintains suspension of insoluble powders and provides glide to products. Oxidized starch absorbs sweat and sebum from skin.

To Conclude, native starch needs modification to widen its utility scope in various industrial domains. Physical and chemical treatments help tailor starch properties for specific formulation requirements. Widely available starch resources and versatility of derivatives have contributed to their extensive applications in major processing sectors ranging from foods to pharmaceuticals. Proper understanding and use of modified starches enables development of high-performance products.

*Note:
1.Source: Coherent Market Insights, Public sources, Desk research
2.We have leveraged AI tools to mine information and compile it