Starch

Starch, Different components of starch, structure of Different starches, Amylose and Amylopectin, applications of starch, Environmental benefits of starch.

1. TOPIC : STARCH SUBJECT : BIODEGRADABLE POLYMERS STARCH

2. Starch Molecule Starch is a polysaccharide. Polysaccharide is made up of hundreds or thousands of glucose molecules . Starch molecule composed of many linked glucose molecules Terminology Polysaccharide – a complex carbohydrate. Glucose – a monosaccharide or simple sugar .

3. widely in vegetables kingdom . > 80 % of all food crops -- cereals and starchy food crops Natural polymer of D-glucose . a very high proportion of world’s food energy intake . Occurs in nature as microscopically small, spherical particles / granules -- whose size and shape are characteristic  each species. STARCH

4. Formed in plants  condensation of large no. of glucose molecules -- into two types of polymers : 1. Amylose -- linear polymer > 2000 glucose units -- α-1,4 glycosidic linkage. 2. Amylopectin -- highly branched -- each branch -- 20 - 30 glucose units & each molecule  hundreds of these branches. Glucose units in linear branch -- α-1,4 linkage . Branch points -- α-1,6-glycosidic linkages . Both amylose and amylopectin  deposited in starch granules  an orderly radial pattern .

5. STRUCTURE OF STARCH

6. Kinds – Native Starches Cornstarch Tapioca Wheat Potato Rice Arrowroot Sago

7. Kinds – Native Starches

8. Composition and Structure Starch granule Starch is deposited in plants in organized units called granules. Starch molecules structured to form crystalline-like patterns in the granule With polarized light, a Maltese cross pattern can be observed under microscope Called birefringence Pattern disappears when starch is heated

9. Cereals and millets (65 to 85 %) e.g., rice, wheat, maize Roots and tubers (19 to 35 %) e.g. tapioca, potato Cereal starch paste (5%)  on cooling sets  a thick jelly Turber starch paste (5%)  a fluid & does not set  to a thick jelly. Cereals  low moisture  starch granules are embedded  in a hard, proteinaceous matrix  requires preliminary softening  starch extraction. Potato  high moisture and no preliminary softening required. SOURCES OF STARCH

10. Characteristics of Starches Amylose Amylopectin Found in Amorphous region Upon Heating - leached out allowing water to enter and swell the starch granule in the crystalline region Found in Crystalline region Highly influences on viscosity changes due to water and heating (gelatinization)

11. Kinds - Resistant Resistant starch is not digested by human body Four main types RS1 RS2 RS3 RS4 May be used in food to increase fiber content

12. Effect of Heat and Cooling Dry heat Starch becomes more soluble Reduced thickening ability Dextrinization Brown, nutty, toasted flavor develops Examples Brown roux and Espagnole sauce A higher proportion of starch to liquid is needed

13. Effect of Heat and Cooling Moist heat Starch granules insoluble in cold water Colloidal dispersion produced with heating Starch paste

14. Long unbranched chain of D-glucose (500 to 5,000 glucose molecules) -- linked -- α-1,4 linkage Molecular weight -- 105 to 106 daltons . Retrogradation -- process -- solution (on keeping) turns turbid -- due to precipitations of amylose . Responsible -- stiffening of cooked rice ( on standing). Blue colour with iodine . Amylose content of starch -- vary  botanical species . Cereal starches : wheat starch  25 – 30% amylose , corn starch ( amylomaize )  40 – 80% amylose . Waxy maize  0% starch. Amylose

15. Branched chain polysaccharide  component of starch Chains linked  α-1,6 linkages Molecular weight  107 to 108 daltons One molecule  50,000 to 5,00,000 molecules of D-glucose Gives  purple colour with iodine Amylopectin

16. What are BIO-based plastics? Bioplastics help manufacturing companies stay competitive by helping to meet rising consumer expectations of sustainability. They are often derived from various biomass sources, the most widely used being starch, which is a natural polymer that can be incorporated in various materials. Starch-based plastics can be used in a variety of applications since they can be incorporated with various petroleum-based polymers or biopolymers to create unique composite materials. These composite materials can then be injection molded or extruded using standard processing machinery.

17. STARCH IN PLASTICS Approximately 50% of the bioplastics used commercially are prepared from starch. The production of starch-based bioplastics is simple, and they are widely used for packaging applications . The tensile properties of starch are suitable for the production of packing materials, and glycerol is added into the starch as a plasticizer. The required characteristics of the bioplastics are achieved by fine-tuning the quantities of the additives. For trade applications, the starch-based plastics are regularly mixed with eco-friendly polyesters.

18. An analysis of a new market research report stated that “starch blends are expected to account for the largest share in the market ” from 2015 to 2020. Out of the 2.05 million tons of bioplastics produced in 2017 worldwide, starch blends accounted for 18.8% . In fact, European Bioplastics stated that “Bioplastics are used in an increasing number of markets, from packaging, catering products, consumer electronics, automotive, agriculture/horticulture and toys to textiles and a number of other segments.” How commonly used are starch-based plastics?

19. Starch can be used to reduce the carbon footprint of traditional resins because they can replace petroleum-based polymers with natural ones. It is also highly degradable, meaning it can be used alongside a compostable polymer without interfering with the degradation process. Environmental benefits

20. The Green Dot Bioplastics team has successfully developed cell phone cases from compostable, starch-based plastics. Additional opportunities are expected in compostable yard and kitchen bags, food service disposables and various types of packaging. Starch-based plastics have increased in relevance with the introduction of improved resin grades, their ability to blend with other biopolymers and an increasing number of suppliers. In fact, starch-based bioplastics are widely employed in the medical industry because of their biocompatibility, low toxicity, degradation properties and mechanical properties. What are the applications?

21. The challenges for researchers and the packaging industry in terms of producing starch-based blends with commercial utility are : a) Overcoming miscibility problems at high starch contents, b) Avoiding mechanical property deterioration at high starch contents, even in compatibilized blends, c) Reducing costs, especially for biodegradable starch-polyester blends at low starch contents (<30 wt.%) . 2) Antimicrobial packaging film: Antimicrobial packaging refers to the integration of an antimicrobial agent into packaging systems for the purpose of preventing microbial growth on food products and extending its shelf life . The packaging materials may acquire antimicrobial activity i ) By incorporating antimicrobial components in a polymer matrix, ii) Surface irradiation of polymer matrix which produces reactive oxidizing species, iii) By gas emission/flush through modified atmosphere packaging , iv) By using inherently antimicrobial polymer resins.

22. Futuristic Approach Focused research is needed in bringing more values such as making the packaging material simpler yet smarter, where consumer is able to assess the quality, safety, shelf-life, and nutritional values of the contents of packet with cost effectiveness. The benefits however should not come at the cost of the cost of curing environmental issues and should eco-friendly.