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1 Starch Sandra Hill LEARNING OUTCOMES –Usage of starch –Understand the structure and nomenclature used for starch polysaccharides –Appreciate some of.

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Presentation on theme: "1 Starch Sandra Hill LEARNING OUTCOMES –Usage of starch –Understand the structure and nomenclature used for starch polysaccharides –Appreciate some of."— Presentation transcript:

1 1 Starch Sandra Hill LEARNING OUTCOMES –Usage of starch –Understand the structure and nomenclature used for starch polysaccharides –Appreciate some of the structural features of starch granules –Recognition that starch is only one component of storage organs –Modified starches Nov 2004

2 2 Starch Major food for animals Usage in the paper industry Bioethanol production Filler component for many pharmaceuticals Building material Some times eaten by people

3 3 FoodBeverageAnimal FeedPlasticPharmacyBuilding MayonnaiseSoft drinksPelletsBiodegradable plasticTabletsMineral fibre tiles Baby foodBeerBy productsDusting powderGypsum board BreadAlcoholConcrete BunsCoffeeGypsum plaster ConfectioneryAgricultureTextilePaperVarious Meat sausagesJelly gumsSeed coatingWarpCorrugated boardFoundries Meat rolls and loavesHigh-boiled sweetsFertiliserFabricsWater treatment KetchupJelliesYarnsCardboardCoal Marchmallows SoupsMarmaladePaperDetergent SnacksJamFermentationNon-WowenPrinting paperOil drilling Pizza saucesIce creamce creamVinegarHygienic diapersStain remover SaucesDairy creamEnzymesBaby diapersPackaging materialGlue Low fat foodsFruit fillingsSanitary napkinsFoamed starch Noodles

4 4 Given the right crops and new technology, bioethanol could make a real contribution to world fuel needs, writes Giuliano Grassi.Giuliano Grassi Bioethanol plant in Nebraska, USA, processes corn to produce 925 litres per day (Minnesota Corn Producers). 03/bioethanol.html

5 Starch based products High proportion of human requirement for energy supplied by starch –potatoes crisps chips –maize extruded products –rice variety and preference –wheat (bread and cake and the bubble) –cassava a staple for much of the world

6 Starch Starch the chemical Starch the macromolecule Starch the supermacromolecule Starch the granule Starch the stuff that comes in a sack

7 7 In Europe a starch factory consumes between 1,000 and 2,000 tonnes of cereals each day.

8 Carbohydrates sugar components –open chains –ring structures chair H CHO OH HHO OHH OHH CH 2 OH O HO O H H HO H HO OH H H OH o Starch the chemical

9 Linking sugars link (1-4) –example maltose glucose -glucose

10 multiple links (ribbons and helices)

11 Amylose and Amylopectin

12 link (1-6) –example amylopectin glucose -glucose

13 Amylose helix Pitch 0.8nm 6 residues per turn Double helix, association of 2 left handed helices

14 Starch carbohydrate reserve –seeds –roots –tubers –stem Native starch always is: glucose polymers –amylose ( 1-4) and amylopectin ( 1-4 and 1-6) packed into granules –different size and shape depending of the botanical source –semi crystalline structures

15 How starch is laid down in the plant Smith, Denyer & Martin, 1993

16 Starch complex assembly of two macromolecules amylose Glucose units linked (mostly) 1-4 Number of glucose units ~ 250-5, % weight

17 Racemose model Amylopectin 70-85% by weight number of glucose units ~ 10, ,000 branch chains ~20 glucose units only one reducing end Glucose units linked 1-4 and some 1-6 linkage

18 Diagram of the starch granule organisation

19 Glucose chains form helices Two types in native starch A and B mixture of A and B known as C differ in the amount of water in the helix

20 Can tell the structure of the helices by X-ray X-ray wavelength m

21 Packing of the molecules to form a starch granule

22 Polarised Light-optical microscope

23 23 Measurement of the amount of crystallites DSC (Differential scanning calorimetry) –Temperature at which the crystallites melt –Amount of energy required to melt them NMR (nuclear magnetic resonance) FTIR (Fourier transform infra red) Endothermic heat flow 65C

24 Growth ring Wheat starch granule, erosion during germination

25 25 (Gallent et al, 1997)

26 Size shape and morphology of the granules is characteristic of the botanical source wheatlentil rice rye maize potato shoti avacado green pea 10 m

27 Starch Storage polysaccharides examples cereal wheat rice oat barley seedspea tuberpotato cassava / tapioca /manioc stemsago

28 Different starches From Pomeranz 1991 Swinkels,1985 Molecules per granule 10* * * * *10 -12

29 Remember that with the starch can come other components within the granule wheatmaizepotato Amylose Lipids Protein Ash Phosphorus * Internal components Note : the amount of amylose depends on the method used to measure

30 Amylose : a)the straight chain portion (but there are often some 1-6 linkages) b)the portion that incorporates iodine (chains of less than 10 glucose units -no colour colour goes from red, red-purple, purple, blue depending on chain length) 645nm d.p. 366 or higher but long chains of the amylopectin, often B1 chains, can do this) c)hot water soluble fraction (amylose not water soluble at above 2mg/ml, it precipitates)

31 Remember that with the starch can come other components from outside the granule External components Maize: starch in protein matrix

32 Texture Cell walls Starch Cooking Cell/cell adhesion Properties of the starch RAW

33 33 Modified starch

34 Starch and Water starch is biosynthesised in an aqueous environment drying starch can cause shrinkage and cracks most water goes to the amorphous phase or to the surface of the crystallites material up to 1000 daltons can enter the starch granule-might be pores dry starches in water can absorb up to 50% of its weight -will expand %, this is reversible.

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