Classification of Food Starches | Food Chemistry | Biotechnology (2022)

Depending on the sources, food starches are classified into three: 1. Natural Starches – Amylose and Amylopectins 2. Modified Starches 3. Waxy Starches.

1. Natural Starches – Amylose and Amylopectins:

These are naturally present starches in various types of plant foods. The starch granules from various grains differ in size, ranging from 2 to 150 microns. Their shape may be round or polygonal in corn, wheat, waxy maize, etc. Starch is made up of two molecules, amylose and amylopectin, whose parts are connected by glycosidic linkages.

Amylose molecules typically make up approximately one-quarter of starch. Amylose is a long linear chain composed of thousands of glucose units with attachment of the carbon 1 and carbon 4 of glucose units, and therefore contains α -1, 4 glycosidic linkages. It forms a three-dimensional network when molecules associate upon cooling, and is responsible for the gelation of cooked, cooled starch pastes. The amylose content of various starch sources includes – cereal grains – 26-28% and roots and tubers – 17-23%.

Amylose chain Amylopectin molecules constitute approximately three quar­ters of the polymers in a starch granule. The glucose chain of amylopectin contains α -1, 4 glycosidic linkages, similar to amylose, also with α -1, 6 branching at every 15-30 glucose units of the chain. There is a linkage between the carbon 1 of the glu­cose and carbon 6 of the branch.

The chains are highly branched and bushy. The branches make amylopectin less soluble in water than amylose. Starches with a high percentage of amylopectin will thicken a mixture but do not form a gel. The greater the amy­lopectin, the more viscous the starch paste and the greater the amount of amylose the stronger the gel.

2. Modified Starches:

Natural starches may be modified chemically to produce physical changes that contribute to shelf stability, appearance, convenience, and performance in food preparation.

The important types of modified starches used in food biotechnology are:

(i) Pregelatinised starches

(ii) Cold water-swelling (CWS) starches

(iii) Cross-linked starches

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(iv) Stabilized (substituted) starches, and

(v) Acid modified starches.

(i) Pregelatinized Starches:

Pregelatinized starch is an instant starch that has been gelatinized and then dried. It subsequently swells in liquid without the application of heat. Pregelatinised starch appears in many foods, including instant pudding mixes. The main properties of pregelatinized starches are it will dispersible in cold water, it can be cooked and dried and it undergoes irreversible change and cannot return to its original ungelatinized condition.

(ii) Cold Water-Swelling (CWS) Starches:

Cold water-swelling (CWS) starch is an instant starch that remains as an intact granule. It offers convenience, stability, clarity, and texture. Cold water-swelling starches maybe gelling or non-gelling. They may be used in cold-process salad dressings, providing the thick, creamy mouth feel in no-fat salad dressings.

(iii) Cross-Linked Starches:

Cross-linked starches are those that undergo a molecular reaction at selected hydroxyl (-OH) groups of two adjoining, intact, starch molecules. The purpose of cross-linking is to enable the starch to withstand such conditions as low pH, high shear, or high temperatures.

The cross-linked starch becomes less fragile and more resistant to rupture than the original unmodified starch. These starches are used in many foods, especially acid food products such as pizza sauce or barbecue sauce because the modified starch is more acid resistant than an unmodified starch.

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(iv) Stabilized (Substituted) Starches:

Stabilized (substituted) starches are used in frozen foods and other foods stored at cold temperature in order to prevent gelling. The stabilized starch produces pastes able to withstand several times in freeze condition and also foods such as sauces and gravies stored at cold temperatures.

(v) Acid Modified Starches:

Acid modified starch is starch that is subject to treatment in acid slurry by heat treatment. Once the starch is mixed into a food product and farms a strong gel upon cooling.

3. Waxy Starches:

Waxy starches are derived from some natural strains of barley, corn, rice, and sorghum. They do not contain amylose, become less thick and do not produce gels, e.g., waxy cornstarch, which does not have the same gel forming properties as ordinary cornstarch. It contains no gel producing amylose, but consists of amylopectin.

Soluble Fibers:

Pectins, gums and mucilages are the important soluble fiber like polysaccharides in foods. They are widely used as gelling agents, thickeners, and stabilizers. They are constituents of plant tissue and are large, complex molecules whose exact nature is not certain. Because of their functional properties it is helpful to produce convenience and special texture foods.

Pectins:

Pectic substances including protopectin, pectinic acid, and pectic acid are an important constituent of plant tissue and are found mainly in the primary cell wall. They also occur between cell walls, where they act as intercellular cement. Pectic substances may be grouped into one of the three categories depending on the number of methyl ester groups attached to the polymer.

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They are listed follows:

(i) Protopectin:

It is found in immature fruits and is a high-molecular-weight methylated galacturonic acid polymer. It is insoluble in water but can be converted to water dispersible pectin by heating in boiling water. It cannot form gels.

(ii) Pectinic Acid:

It is a methylated form of galacturonic acid that is formed by enzymatic hydrolysis of protopectin as a fruit ripens. The high- molecular-weight pectinic acids are known as pectins. Pectinic acids are dispersible in water and can form gels.

(iii) Pectic Acid:

It is a shorter-chain derivative of pectinic acid that is formed as fruit over ripens.

(iv) Structure of Pectin:

Pectins are high-molecular-weight pectinic acids and are dispersible in water. It is a linear polymers of D-galacturonic acid joined by α -1, 4-glycosidic linkages. Some of the carboxyl groups along the galacturonic acid chain are esterified with methanol. The degree of esterification in unmodified pectins ranges from about 60% in apple pulp to about 10% in strawberries. According to the degree of esterification, pectins are classified as high methoxyl or low methoxyl pectins.

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(v) Low-Methoxyl Pectin:

Low-methoxyl pectins contain mostly free carboxyl groups and only 20-40% of the carboxyl groups are esterified. So, most of them are cross-links with divalent ions such as calcium and form gels

(vi) High-Methoxyl Pectin:

High-methoxyl pectins contain a high proportion (usually 50- 58%) of esterified carboxyl groups. It will not produce cross-links with divalent ions, so these pectins do not form gels. But they can be made to gel with the addition of sugar and acid. It is the high- methoxyl pectins that are commonly used to form pectin jellies.

(vii) Pectin Sources:

Pectins are commonly seen in jams, jellies, apple, citrus fruits and some desserts. Pectins with a high-molecular weight and a high proportion of methyl ester groups have the best jelly-forming ability. The pectin content of fruits is variable and depends not only on the type of fruit but also on its maturity or ripeness. If jellies or jams are made at home, it is best to add commercial pectin to ensure that there is sufficient pectin to form a gel. Purified pectin is made from apple cores and skins (apple pomace) and from the white inner skin of citrus fruits.

(viii) Pectin Gel Formation:

A pectin gel consists of water held in a three-dimensional network of pectin molecules. Pectin is dispersible in water and forms a sol (solid dispersed in liquid continuous phase), but under the appropriate conditions, it can be converted into a gel (liquid dispersed in solid continuous phase). It is not easy to form pectin gels; it requires a delicate balance of pectin, water, sugar, and acid.

Pectin is hydrophilic (water loving) due to the large number of polar hydroxyl groups and charged carboxyl groups on the molecule. When pectin is dispersed in water, some of the acid groups ionize and water binds to both the charged and polar groups on the molecules. The negative charge on the pectin molecules, coupled with their attraction for water, keeps them apart so that they form a stable sol.

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FAQs

What are the 4 types of starch? ›

All five starch types (potato, tapioca, wheat, corn, and rice) have been characterized by LD and MIA.

What is starch in food chemistry? ›

Starch is a polysaccharide made up of 1,4 linkages between glucose monomers. The chemical formula of the starch molecule is (C6H10O5)n. Starch is made up of long chains of sugar molecules that are connected together. The linear polymer amylose is the most basic form of starch, while amylopectin is the branched form.

What are the 3 starches? ›

Starch can be found in two varieties native starch and modified starch. The first is a natural derivative of the vegetable and the second is chemically modified as a thickener. The most common starches used in in gluten free cooking are: corn starch, arrowroot starch, tapioca and potato starch.

What is the classification of simple starch? ›

Depending on the different velocity and degree of hydrolysis by alpha-amylase, starch can be classified in three classes: Rapidly digestible starch. Slowly digestible starch.

What are the 5 different kinds of starch? ›

Today, the main commercial refined starches are cornstarch, tapioca, arrowroot, and wheat, rice, and potato starches. To a lesser extent, sources of refined starch are sweet potato, sago and mung bean. To this day, starch is extracted from more than 50 types of plants.

What are the two classes of starch? ›

Starch consists of glucose molecules. It can occur in two forms: amylose and amylopectin. Amylose is a linear or straight-line polymer that scientists describe as amorphous or solid. Amylopectin forms a branched chain and is crystalline.

What are the 7 functional properties of starches? ›

Viscosity, shear resistance, gelatinization, textures, solubility, tackiness, gel stability, cold swelling and retrogradation are all functions of their amylose/amylopectin ratio.

What is starch and examples? ›

Starch is a type of carbohydrate. Its molecules are made up of large numbers of carbon, hydrogen and oxygen atoms. Starch is a white solid at room temperature, and does not dissolve in cold water. Most plants, including rice, potatoes and wheat, store their energy as starch.

What are the characteristics of starch? ›

Characteristics. Starch is a complex polysaccharide made up of a large number of glucose units joined together by glycosidic bonds. It is white, tasteless, and odorless powder. It has a variable molar mass.

What is the function of starch? ›

The only function of starch in the human diet is to convert into glucose for energy. Starch begins breaking down in your mouth, where saliva surrounds complex starch molecules. As you chew, saliva breaks up starch into simpler carbohydrates called maltose.

What are the components of starch? ›

Starch contains two main components: amylose and amylopectin.

What are the different source of food starch? ›

Corn, cassava, sweet potato, wheat, and potato are the major sources of food starch, while sorghum, barley, rice etc., serve as minor source of starch in different parts of the world.

What are the 3 classification of carbohydrates? ›

Three types of simple carbohydrates include: Monosaccharides. Disaccharides. Polysaccharides.

What is the classification of modified starch? ›

According to their main physicochemical characteristics, modified starches can be classified into four main categories: pregelatinized, derivatized, cross-linked, and dextrinized starches (Table 2).

Why is starch classified as a polysaccharide? ›

Polysaccharides are long chains of monosaccharides linked by glycosidic bonds. Three important polysaccharides, starch, glycogen, and cellulose, are composed of glucose. Starch and glycogen serve as short-term energy stores in plants and animals, respectively. The glucose monomers are linked by α glycosidic bonds.

What are the six starch properties and reaction? ›

The properties of dextrinized starch is dependent upon the reaction conditions (moisture, temperature, pH, reaction time) and the products characteristics vary in its content of reducing sugar, cold water solubility, viscosity, color and stability.

What is the functional group of starch? ›

The two important functional groups in most polysaccharides are the hydroxyl group and the acetal group. Starch is a typical polysaccharide.

What are the two types of starches and what is the difference between them? ›

There are two forms of starch: amylose and amylopectin. Structurally they differ in that amylose is a linear polysaccharide, whereas amylopectin is branched.

What are starch foods to avoid? ›

You should avoid the following foods due to their high starch content:
  • Pasta. A cup of cooked spaghetti has 43 grams (g) of carbohydrates, 36 of which come from starch. ...
  • Potatoes. A single, medium-sized potato has about 31 g of starch. ...
  • White Bread. ...
  • White Rice. ...
  • Corn.
26 Oct 2020

What are natural starches? ›

Native starches are basically pure forms of starch. They can be obtained from sources such as corn, wheat, potato, rice, cassava and tapioca. These long-chain carbohydrates are insoluble in cold water and swell to different degrees, depending on type and temperature.

What is called starch? ›

Starch is a soft, white, tasteless powder that is insoluble in cold water, alcohol, or other solvents. The basic chemical formula of the starch molecule is (C6H10O5)n. Starch is a polysaccharide comprising glucose monomers joined in α 1,4 linkages.

What is starch in human body? ›

Starch is a type of carbohydrate consisting of glucose molecules. Glucose provides cells with energy and helps nerve cells in the brain function properly. Starchy foods come in many forms, and people often consume them as staple foods in diets worldwide. Legumes, grains, and root vegetables are all examples of them.

Why is starch important? ›

Starchy foods are our main source of carbohydrate and play an important role in a healthy diet. They are also a good source of energy and the main source of a range of nutrients in our diet. As well as starch, they contain fibre, calcium, iron and B vitamins.

What is a healthy starch? ›

Rice and grains are an excellent choice of starchy food. They give us energy, are low in fat, and good value for money. There are many types to choose from, including: all kinds of rice – such as quick-cook, arborio, basmati, long grain, brown, short grain and wild.

What are sources of starch? ›

Starch is obtained from a variety of plant sources. Corn, cassava, sweet potato, wheat, and potato are the major sources of food starch, while sorghum, barley, rice etc., serve as minor source of starch in different parts of the world. Native or raw starch occurs in the form of granules.

What are the components of starch? ›

Starch contains two main components: amylose and amylopectin.

Is starch a protein? ›

Starch is not a protein.

How is starch formed? ›

Starch is an example of a natural polymer. A polymer is a long and repeating chain of the same molecule stuck together. Starch is a long-chain polymer of glucose molecules joined together. As the plant adds one glucose molecule to the starch polymer, one molecule of water is released.

What are the characteristics of starch? ›

Characteristics. Starch is a complex polysaccharide made up of a large number of glucose units joined together by glycosidic bonds. It is white, tasteless, and odorless powder. It has a variable molar mass.

What is the chemical formula of starch? ›

What is the other name for starch? ›

What is another word for starch?
sugarcarbohydrate
cassonadesweetener
refined carbohydratexylose
saccharoselevulose
saccharin
9 more rows

What enzyme breaks down starch? ›

Amylases digest starch into smaller molecules, ultimately yielding maltose, which in turn is cleaved into two glucose molecules by maltase.

What is the difference between starch and carbohydrates? ›

The key difference between carbohydrates and starch is that carbohydrates can be polymeric or non-polymeric compounds, whereas starch is a polymeric carbohydrate. Carbohydrates are biomolecules that contain carbon, hydrogen, and oxygen atoms with a 2:1 ratio between hydrogen and oxygen atoms.

What are the three starch properties and reactions? ›

Starch can undergo reactions such as hydrolysis, esterification, etherification and oxidation. These reactions give modified starches which can be used in baked foods, confectionaries, soups and salad dressings.

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