● Starch, is a white, granular, organic chemical that is produced by all green plants.
● It is a soft, white, tasteless powder that is insoluble in cold water, alcohol, or other solvents.
● The basic chemical formula is (C6H10O5)n.
● It is a polysaccharide comprising glucose monomers joined in α 1,4 linkages.
● The simplest form of starch is the linear polymer amylose; amylopectin is the branched form
Starch is manufactured in the green leaves of plants from excess glucose produced during photosynthesis.
● Starch is stored in chloroplasts in the form of granules and in such storage organs as the roots of the cassava plant, the tuber of the potato, the stem pith of sago, and the seeds of corn, wheat, and rice.
● When required, starch is broken down, in the presence of certain enzymes and water, into its constituent monomer glucose units, which diffuse from the cell to nourish the plant tissues.
● In humans and other animals, starch from plants is broken down into its constituent sugar molecules, which then supply energy to the tissues
Modified Starch
Modified starch is a food additive that is prepared by treating starch granules, causing them to be partially degraded.
● The purposes of this modification are to enhance its properties, particularly in specific applications.
● To improve the increase in water holding capacity, heat resistant behavior, reinforce its binding, minimized the syneresis of starch, and improve thickening.
Advantage Of Modifying Starches
● Unprocessed native starches are structurally too weak and functionally too restricted for application in pharmaceutical, food, and non-food technologies.
● Modifications are necessary to create a range of functionality.
● Starch modification can be introduced by altering the structure and affecting the structure including the hydrogen bonding in a controlled manner to enhance and extend their application from an industrial perspective.
● The modification takes place at the molecular level. Modified starches are typically used in food systems around the globe.
● They are mainly added to primarily thicken, stabilize or, texturally influence a food product.
Reasons For Modifying Starches
Provide functional Attributes.
Abundant and readily available.
Provide an economic advantage.
PRODUCTION OF STARCH
● The production is an isolation of starch from plant sources. It takes place in starch plants.
● Starch industry is a part of food processing that is using starch as a starting material for the production of starch derivatives, hydrolysates, and dextrins.
Wheat was originally used as the raw material for making starch. Currently, the following are the most common sources of starch:
- maize or corn (in America, China, and Europe) – 70%,
- potatoes (in Europe) – 12%,
- wheat – 8% (in Europe and Australia),
- tapioca – 9% (South East Asia and South America)
- rice, sorghum, and others – 1%.
Corn Starch
● Corn starch, also known as maize starch or cornflour in British English, is obtained from the grain of corn(maize).
● It is extracted from the kernel’s endosperm.
● Starch is a common culinary additive that is used to thicken sauces and soups, as well as to manufacture corn syrup and other sugars.
● It is versatile and easy to modify, and it has a wide range of applications in industry, including adhesives, paper goods, anti-sticking agents, and textile manufacture.
POTATO STARCH
● Potato starch is a type made from potatoes.
● Leucoplasts are found in the cells of the potato plant’s root tubers (starch grains).
● The potatoes are crushed to extract it, and the starch grains are liberated from the destroyed cells.
● The starch is then dried to powder after settling out of the solution or being separated by hydro cyclones.
PRODUCTION OF MODIFIED STARCHES
● Starch extracted from grains and vegetables such as wheat, maize, and potatoes is used to make modified starches.
● This starch has now been enhanced to give it specialized properties, such as the capacity to lend texture and structure to the dish to which it is added.
● They can acquire specific capabilities depending on the process, which might be useful in certain food preparation processes, for example.
The various modifications of starch make it possible to obtain:
- Easier food preparation
- Better conservation of food
- Better stability of food even when heated under severe conditions
Modification Of starch
● Physical Modification: Physical modifications are starch property modifications imparted by physical treatments that do not result in any chemical modification of the starch other than limited glycosidic bond cleavages. Thermal treatments include those that produce pregelatinized and granular cold-water-swelling starches, heat-moisture treatment, annealing, microwave and other heating of “dry” starch, and “osmotic pressure treatment.” Nonthermal treatments include sonication, milling, static ultrahigh-pressure treatments, and the use of high-pressure.
● Chemical Modification: The extracted starches were separately carboxymethylated and their degrees of substitution were determined by pH-metric titration. Moreover, the carboxymethylation of the potato, maize, and cassava starches was carried out using sodium hydroxide and mono-chloroacetic acid.
● Enzyme-modified: Starch modified with amylase enzyme produces a derivative with good adhesion properties and is mainly used in coating food with colorant.
● Heat-moisture treatment: Heat-moisture treatment of starches is defined as a physical modification that involves incubation of starch granules at a low moisture level (<35% water w/w) during a certain period of time. In addition, this occurs at a temperature above the glass transition temperature but below the gelatinization temperature (Hoover 2010).
● Annealing: Annealing causes an increase in pasting temperatures and, at the same, makes the temperature range narrower. In addition, it has little effect on the process of enthalpy. If starch retains its grainy structure after modification, its swelling power decreases with an increase in pasting temperatures.
● Retrogradation: Starch retrogradation has been used to describe changes in physical behavior following gelatinization. It is the process that occurs when starch molecules reassociate and form an ordered structure. Under favorable conditions, a crystalline order appears and physical phase separation occurs.
● Pregelatinization: Starch gelatinization is a process of breaking down its intermolecular bonds in the presence of water and heat. Subsequently, allowing the hydrogen bonding sites (the hydroxyl hydrogen and oxygen) to engage more water. This irreversibly dissolves the starch granule in water.
Chemical Modification
● Cross-linking: It is the most important modified form that is used in industry. It involves the replacement of hydrogen bonds present between starch chains by stronger, permanent covalent bonds. Distarch phosphate or, adipate is the most commonly used cross-linked starch. Cross-linked ones offer acid, heat, and shear stability over native starch.
● Esterification: Esterification is one of the most important methods to alter the structure of starch granules and improve their applications. Conventionally, starch esters are prepared by conventional or dual modification techniques, which have the disadvantages of being expensive, having regent overdoses, and being time-consuming.
Also see: Various Types Of Flavors And Their Isolation/Extraction Methods In Detail
● Acid Treatment: Acid modification has been shown to change the physicochemical properties of starch without destroying its granular structure, yielding starch with increased solubility and gel strength but decreased viscosity; the extent of hydrolysis depends on starch consistency, the acidity of the medium.
● Oxidation: It is obtained by reaction with sodium hypochlorite or peroxide. These are mainly used as surface sizing agents or coating binders and are available in different viscosity grades.
● Enzymatic Modification: The technology of enzymes has many potential applications in the baking industry because carbohydrate-active enzymes specifically react with carbohydrate components, such as starch, in complex food systems.
● Amylolytic enzymes are added to starch-based foods, such as baking products, to retain moisture more efficiently and to increase softness, freshness, and shelf life.
● The catalytic reaction of a single enzyme or a mixture of more than two enzymes has been applied, generating novel starches, with chemical changes in the starch structure, in which the changes in molecular mass, branch chain length distribution, and the ratio of amylose to amylopectin may occur. These developments in enzyme technology highlight the potential to create various structured starches for the food and baking industry.
● The major reactions used to modify the structure of food starch include:
- hydrolysis of α-1, 4, or α-1, 6 glycosidic linkages, disproportionation by the transfer of glucan moieties, and
- branching by the formation of α-1, 6 glycosidic linkages.
Starch Applications in the food industry
Baked Products:
• Baked products like biscuits, pies, bread, cakes wafers, and sausages are high-density products requiring heat-resistant starches. Hence cross-linked starches are used since they are more resistant to oven baking temperatures of 120 ≥ 230°C.
• Gelatinized starches are also used in ready-to-eat cereal meals such as cornflakes, etc.
• The temperature, humidity, and degree of stirring determine the texture and quality of the product.
Confectionery
● Oxidized starches have high clarity or transmittance, low viscosity, and low-temperature stability. It is frequently used in confectioneries for coating
candies and sweets since they easily melt.
Gravies, Soups, and Sauces
● Etherified and cross-linked starches are mostly used.
● Crosslinked starched have higher stability for granules-swelling, high-temperature resistance, high shear stability, and acidic conditions stability.
● They are used as viscosifiers and texturizers in soups, sauces, gravies, bakery, and dairy products.
● Etherified starches have improved the clarity of starch paste, greater viscosity, reduced syneresis, and freeze-thaw stability.
● Crosslinked starches are used in a wide range of food applications such as gravies, dips, sauces, fruit pie fillings, and puddings
Mayonnaise, salad dressing, ice cream, spreads, and beverages
● Hydrolyzed and esterified starches are mostly used in salad dressings and beverages.
● Hydrolyzed (acid-modified starches) have lower paste viscosity under cold and hot conditions. Hence they are used in mayonnaise
and salad dressing.
● Esterified starches have lower gelatinization temperature and retrogradation, lower tendency to form gels, and higher paste clarity, and are used in refrigerated and frozen foods, as emulsion stabilizers, and for encapsulation of beverage clouds.
● OSA starch is used as an emulsifier in mayonnaises and salad dressings.
Pasta, Spaghetti, Or Macaroni
● Pregelatinized and cross-linked starches are mostly used in pasta.
● Gelatinized starch affects pasta elasticity and softness, delectableness, and digestibility. Crosslinking gives the needed structural firmness to the pasta.
Puddings (custard, pap, others).
● Pregelatinized starches are used in puddings, instant lactic mixtures, and breakfast foods to achieve thickening or water retention without
employing heat.
● They are also used in ready-to-use bread mixtures.
● They are used where little or no heat is required and the increased absorption and retention of water improves the quality of the product; as an agglutinant in the meat industry, and as a filling for fruit pies