FNB News - Potential application of starch in food industry

You can get e-magazine links on WhatsApp. Click here

TOP NEWS

Potential application of starch in food industry

Tuesday, 18 January, 2022, 12 : 00 PM [IST]

Katke S. D & Deshpande H. W

Starch is a naturally occurring, biodegradable, inexpensive and abundantly available polysaccharide molecule. It is widely distributed in the form of tiny granules as the major reserve carbohydrate in stems, roots, grains, and fruits of all forms of green leafed plants.

Cereal grains, such as corn, wheat, sorghum, and tubers, and roots, such as potato, tapioca, arrowroot, etc., are some of the commercial sources of starch for industrial exploitation. It consists of glucose units (C6H10O5)n with ‘n’ ranging from 300 to 1000. Starch is composed of a mixture of two polymers called amylose and amylopectin. Amylose is a linear polymer with molecular weight of less than 0.5 million Dalton depending on its botanical source. Amylose macromolecules consist of a-D- glucopyranose units joined by a - 1,4 acetal linkages. Amylopectin molecules are much larger and highly branched with molecular weight of 50 to 100 million Dalton. The molecules contain a -1,4 linear bounds, and is branched through a -1,6 linkages.

In addition to being a major food item, it is currently used industrially as coatings and sizing in paper, textiles and carpets, as binders and adhesives, as absorbents, and as encapsulants bone replacement implants, bone cements, drug delivery systems, and tissue engineering scaffolds. However, in native state it exhibits limited applications due to low shear stress resistance and thermal decomposition, high retrogradation and syneresis, in addition to poor processability and solubility in common organic solvents.

Therefore, to meet the demanding technological needs of today, the properties of starch are modified by a variety of modification methods. Starch modification is aimed at correcting one or some of the above mentioned shortcomings, which will enhance its versatility and satisfy consumer demand.

Modification of 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. Modification can be chemical, physical and enzymatic. 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 in industrial prospective. 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, stabilise or, texturally influence a food product. In actual context, they can be used as multi-functional form in different industry. The techniques for starch modification have been broadly classified into four categories; physical, chemical, enzymatic and genetical modifications, that aim to produce various novel derivatives with improvised physiochemical properties along with useful structural attributes.

Types of Modified Starches
1. Pregelatinised starch:
It is the simplest starch modification, prepared by cooking the slurry, roll drying, spray drying or, extrusion process. It maintains starch integrity while providing cold water thickening.

2. Cross-linked starch:
Cross linking is the most important modified form that used in industry. It involves replacement of hydrogen bond present between starch chains by stronger, permanent covalent bonds. Di-starch phosphate or, adipate are the most commonly used cross-linked starch. Cross-linked starches offer acid, heat and shear stability over the native starch.

3. Oxidized starch:
It is obtained by reaction with sodium hypochlorite or peroxide. These are mainly used as surface sizing agent or coating binder and available in different viscosity grade.

4. Cationic starch:
Cationic starches are produced by reacting native starches with tertiary or, quaternary amines, using wet or dry production processes. They are mainly used in paper forming process.

5. Anionic starch:
Anionic starches are prepared by reaction with phosphoric acid and alkali metal phosphates or by making derivative with carboxymethyl group.

6. Thinned starch:
These are produced through depolymerisation reaction by hydrochloric acid or other acids.

7. Acetylated starch:
Starch after treatment with acetic anhydride produces starch esters which are useful in biodegradable applications. In particular, high DS starch acetates provide thermo-plasticity, hydrophobicity and compatibility with other additives.

8. Dextrins:
Dextrination is the heating of powdered starch, mostly in the presence of small amounts of acids, at different temperatures and with different reaction times. Dextrins are used as adhesives in paper and textile based industry.

9. Grafted starch:
Grafted starches are produced by free radical copolymerisation with ethylenically unsaturated monomers. Starch grafted with synthetic polymers are most utilized starches from different botanical origins were grafted with 1, 3 butadiene, styrene, acrylamide, acrylonitrile and Meth acrylic acid using free redox reaction.

10. Starch ethers:
Starch ethers are produced by a nucleophilic substitution reaction with an ethylenically unsaturated monomer, followed by acid-catalysed hydrolysis for viscosity adjustment.

11. Physically modified starch:
Native starch can be modified with mechanical treatment, using spray drying technique, annealing technique.

12. Enzyme modified starch:
Starch modified with amylase enzyme produces derivative with good adhesion property and mainly used in coating the food with colourant.

Application of starch in Food Industry
It has been almost decades since commercial production of starch for food and industrial application was initiated. Native starch is utilised in the food industry in a number of forms, but we shall concerns about modified starches in food industry which is mainly used to enhance paste consistency, thickening, smoothness and clarity and also to impart cold storage stability and freeze thaw stability in comparison to its native counterpart. Most modified starches involve introduction of low levels of substituent group through the interaction of hydroxyl group. Food industry generally recommends modified starches with less degree of substitution (0.2 to 0.0001 or less). Modified starches are used in different food types like baked food, baby foods, snacks, confectionaries.

1. Frozen Food:
To stabilise the food products starches are used in frozen bottle foods to provide freeze-thaw stability and retrogradation.

2. Flavor Encapsulation:
Modified starches are used to encapsulate or, preserve the flavor of the food products. Octenylsuccinylated derivatives and other starch hydrolysates are used as flavor encapsulation.

3. Dairy Products:
Modified starches are used in a wider way to the dairy products; it provides variety of effects, including enhanced viscosity, cuttability, mouthfeel and stability. In puddings, starch is used to enhance viscosity and smoothness. Starches are used in yogurts and sour cream to control syneresis and enhance thickness.

4. Canned Food:
Canning process preserves food for up to several years by achieving a temperature sufficient to destroy or inactivate food poisoning or spoilage microbes. Starch is most commonly used to thicken, stabilize and enhance the mouthfeel of canned foods such as puddings, pie- fillings, soups, sauces and gravies. Highly cross-linked starches are used for this purpose.

Table 1. Commercially available starch and functions

Starch source	Function
Corn	Increased fibre content in cake production. Reduce sponge cake texture as compared to wheat flour. Corn syrup production. Thickener in infant formula.
Wheat	Breadfruit cookies formulation. Gelling properties.
Potato	Pasting and gelling properties. Production of potato starch film.
Tapioca / Cassava	Increased quality gluten-free jasmine rice bread. Thickener in fruit filling. Enhancing soup product.
Rice	Emulsion stabilizer. Improved gel properties with the addition of hydrocolloids.

Table 2. Potential application of starches

Type of starch	Application
Native starches	Paper, Textile food, cardboard and potable alcohol production industry
Hydrolyzed starches
Maltodextrins	Food preparation (bulking agent) Pharmaceutical (excipient) Ingredient in ice cream industry
Glucose syrup	Dextrose Equivalent of between 40 and 60: food industry Beverage and confectionary industry Used directly as a substrate for the manufacture of fermentation products (such as citric acid, lysine or ethanol or glutamic acid) Processed into other major starch derivatives, such as iso-glucose, fructose syrup
Modified starches
Substituted starches	Textiles Paper Water treatment (flocculation) Oil industry (fluid loss reducer)
Converted starches	Dextrins: Adhesives (gummed paper, bag adhesives, bottle labelling) Textiles (textile fabric finishing, printing)
Converted starches	Acid-modified starches: Food industry (sweets) and Pharmaceuticals Oxidized starches: Food and paper industry (surface sizing, coating) Textile industry (fabric finishing, warp sizing) Enzymatically converted starch: paper industry and fermentation industry
Cross-linked starches	Food industry (desserts, bakery products, soups, sauces) Textile industry (printing) Adhesives Pharmaceuticals