Starch

Chemical Properties

white fine crystalline powder

Chemical Properties

Starch occurs as an odorless and tasteless, fine, white to off-white powder. It consists of very small spherical or ovoid granules or grains whose size and shape are characteristic for each botanical variety.

Uses

corn starch is used as a thickener in cosmetics and in face powders. Corn starch absorbs water and is soothing to the skin. It can cause allergic reactions such as inflamed eyes, stuffy nose, and perennial hay fever. A natural material obtained from corn kernels.

Uses

Dusting powder; pharmaceutic aid.

Uses

Starch is used in face powders to give a “peach-like” bloom and also to provide a smooth surface on the skin. One problem with rice starch is that when it is moistened, it tends to cake. Furthermore, another drawback is that the wet product might provide an environment for bacterial growth.

Uses

Starch is a carbohydrate consisting of glucose units containing amy- lose and amylopectin which contribute to varying starch properties. starch is insoluble in cold water, but upon heating the starch gran- ules swell and burst forming starch paste. starch sources include arrowroot, corn, potato, rice, sage, tapioca, waxy corn, and wheat. starches are modified by treatment to alter their functional proper- ties. terminology designating these starches includes acid-modified cornstarch, food starch modified, modified food starch, oxidized cornstarch, pregelatinized starch, thin-boiling starch, and wheat starch, gelatinized. see specific starch.

Definition

A polysaccharide that occurs exclusively in plants. Starches are extracted commercially from maize, wheat, barley, rice, potatoes, and sorghum. The starches are storage reservoirs for plants; they can be broken down by enzymes to simple sugars and then metabolized to supply energy needs. Starch is a dietary component of animals.
Starch is not a single molecule but a mixture of amylose (water-soluble, blue color with iodine) and amylopectin (not water-soluble, violet color with iodine). The composition is amylose 10–20%, amylopectin 80–90%.

Production Methods

Starch is extracted from plant sources with specific processes according to the botanical origin. Typical production steps are steeping (corn), wet milling (corn, potato), dry milling (wheat), or sieving and physical separation with hydrocyclones. The last production step is usually a centrifugal separation from the starch slurry followed by drying with hot air. The starch separation process may use sulfur dioxide or peroxides as a processing aid, improving the separation process and the microbial quality of the final product.

Definition

starch: A polysaccharide consistingof various proportions of two glucosepolymers, amylose and amylopectin.It occurs widely in plants,especially in roots, tubers, seeds, andfruits, as a carbohydrate storageproduct and energy source. Starch istherefore a major energy source foranimals. When digested it ultimatelyyields glucose. Starch granules are insolublein cold water but disrupt ifheated to form a gelatinous solution.This gives an intense blue colourwith iodine solutions and starch isused as an indicator in certain titrations.

General Description

Fine, white, odorless powder. Note that granules from different vegetable sources vary in shape, size, and general appearance. A mixture of the carbohydrate polymers amylose amylopectin varying according to the vegetable source. Principally used for food.

Reactivity Profile

Starch is combustible. Presents a dust explosion hazard if dispersed as a fine dust in air in sufficient concentrations. Granules swell greatly in water and produce a colloidal suspension. Incompatible with oxidizing agents, acids, iodine, bases. Reacts with nitric acid/sulfuric acid mixtures to give nitroStarch, an explosive.

Hazard

Dermatitis. Questionable carcinogen.

Agricultural Uses

Starch is reserve carbohydrate usually stored in the seeds, roots or stems of a plant. It is the second largest source of carbohydrates, next only to cellulose. Although starch is widespread in plants, only a few sources are abundant enough to make the extraction commercially feasible. The general sources are arrowroot, barley, corn, maize, potato, rice, sago, sorghum, tapioca and wheat. Arrowroot, barley, potato and wheat are commercial sources of starch, available as loosely packed granules of varying shapes and sizes. There are two basic types of starch molecules - the linear starch polymer and the branched starch polymer. Starch is a polysaccharide consisting of various proportions of the two glucose polymers, namely, amylose and amylopectin.
Amylose consists of an unbranched chain of 200 to 500 glucose units, whereas amylopectin consists of chains of 20 glucose units joined by cross links to give a highly branched structure. Most natural starches are mixtures of amylose and amylopectin; potato and cereal starches are 20 to 30% amylose and 70 to 80% amylopectin.
Amylum is the ordinary starch found in all green plants. A molecule of starch is built out of a large number of a-glucose rings joined through oxygen atoms, thus making starch a major energy source for animals. Starch is a tasteless, odorless, colorless, white amorphous powder insoluble in water. It turns iodine solutions intensely blue, and is used as an indicator in certain titrations. An expert can tell the source of a starch
by its appearance in a grain under the microscope. Starches in the form of rice, potato, wheat and some cereal products, supply about 70% of the world's food. Soluble starch is obtained by heating ordinary starch with 10% hydrochloric acid for 24 hours and then precipitating it with alcohol.
Natural starches are used as thickeners in food.

Pharmaceutical Applications

Starch is a versatile excipient used primarily in oral solid-dosage formulations where it is utilized as a binder, diluent, and disintegrant.
As a diluent, starch is used for the preparation of standardized triturates of colorants, potent drugs, and herbal extracts, facilitating subsequent mixing or blending processes in manufacturing operations. Starch is also used in dry-filled capsule formulations for volume adjustment of the fill matrix, and to improve powder flow, especially when using dried starches. Starch quantities of 3–10% w/w can act as an antiadherent and lubricant in tableting and capsule filling.
In tablet formulations, freshly prepared starch paste is used at a concentration of 3–20% w/w (usually 5–10%, depending on the starch type) as a binder for wet granulation. The required binder ratio should be determined by optimization studies, using parameters such as tablet friability and hardness, disintegration time, and drug dissolution rate.
Starch is one of the most commonly used tablet disintegrants at concentrations of 3–25% w/w; a typical concentration is 15%. When using starch, a prior granulation step is required in most cases to avoid problems with insufficient flow and segregation. A starch– lactose compound has been introduced enabling the use of granular starch in direct compression, improving the tableting process and the disintegration time of the tablets. However, starch that is not pregelatinized does not compress well and tends to increase tablet friability and capping if used in high concentrations. Balancing the elastic properties of starch with adapted excipients has been shown to improve the compaction properties in tableting.
Starch, particularly the fine powders of rice and wheat starch, is also used in topical preparations for its absorbency of liquids. Starch paste is used in ointment formulations, usually in the presence of higher ratios of glycerin.
Starch has been investigated as an excipient in novel drug delivery systems for nasal, and other site-specific delivery systems. The retrogradation of starch can be used to modify the surface properties of drug particles. Starches are useful carriers for amorphous drug preparations, such as pellets with immediate or delayed drug release obtained, for example, by melt extrusion, and they can improve the bioavailability of poorly soluble drugs.
Starch, particularly rice starch, has also been used in the treatment of children’s diarrheal diseases. Specific starch varieties with a high amylose content (resistant starches) are used as insoluble fiber in clinical nutrition, and also for colon-targeting applications. Due to their very high gelatinization temperature, these starches are used in extrusion/spheronization processes. Starches with a high amylopectin content (waxy starches) are used as the starting material for the synthesis of hydroxyethyl starch, a plasma volume expander.
Native starches conforming to pharmacopeial specifications are used as the raw materials for the production of starch-based excipients and active pharmaceutical ingredients, frequently covered with their own pharmacopeial monographs.

Biochem/physiol Actions

Starch is a carbohydrate made up of glucose units joined by glycosidic bonds. Undigested part of potato starch is referred as Resistant starch (RS). Resistant starch, RS4 reduces the concentrations of total cholesterol and triglycerides in the serum as well as enhances the concentration of HDL-cholesterol in Wistar rats.

Safety Profile

A nuisance dust. Mildly toxic by intraperitoneal route. A skin irritant. An allergen. Flammable when exposed to flame; can react with oxidizing materials. Moderately explosive when exposed to flame.

Safety

Starch is an edible food substance, considered a food ingredient and not a food additive. It is regarded as an essentially nontoxic and nonirritant material. Starch is therefore widely used as an excipient in pharmaceutical formulations.
Both amylose and amylopectin have been evaluated as safe and without limitation for daily intake. Allergic reactions to starch are extremely rare and individuals apparently allergic to one particular starch may not experience adverse effects with a starch from a different botanical source. The wheat proteins (gluten) are problematic for conditions such as celiac disease.
Contamination of surgical wounds with the starch glove powder used by surgeons has resulted in the development of granulomatous lesions.
LD50 (mouse, IP): 6.6 g/kg

storage

Dry starch is stable if protected from high humidity. Starch is considered to be chemically and microbiologically inert under normal storage conditions. Starch solutions or pastes are physically unstable and are readily metabolized by microorganisms; they should therefore be freshly prepared when used for wet granulation.
Starch should be stored in an airtight container in a cool, dry place.

Incompatibilities

Starch is incompatible with strongly oxidizing substances. Colored inclusion compounds are formed with iodine.

Regulatory Status

GRAS listed. Included in the FDA Inactive Ingredients Database (buccal tablets, oral capsules, powders, suspensions and tablets; topical preparations; and vaginal tablets). Included in nonparenteral medicines licensed in the UK. Included in the Canadian List of Acceptable Non-medicinal Ingredients.