Starch Sandra Hill LEARNING OUTCOMES Usage of starch

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 1

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

Food Beverage Animal Feed Plastic Pharmacy Building Mayonnaise Soft drinks Pellets Biodegradable plastic Tablets Mineral fibre tiles Baby food Beer By products Dusting powder Gypsum board Bread Alcohol Concrete Buns Coffee Gypsum plaster Confectionery Agriculture Textile Paper Various Meat sausages Jelly gums Seed coating Warp Corrugated board Foundries Meat rolls and loaves High-boiled sweets Fertiliser Fabrics Ketchup Jellies Yarns Water treatment Cardboard Coal Paper Detergent Printing paper Oil drilling Marchmallows Soups Marmalade Snacks Jam Fermentation Non-Wowen Pizza sauces Ice cream Vinegar Hygienic diapers Sauces Dairy cream Enzymes Baby diapers Low fat foods Fruit fillings Sanitary napkins Stain remover Packaging material Glue Foamed starch Noodles 3

Given the right crops and new technology, bioethanol could make a real contribution to world fuel needs, writes Giuliano Grassi. Bioethanol plant in Nebraska, USA, processes corn to produce 925 litres per day (Minnesota Corn Producers). http: //www. jxj. com/magsandj/rew/2000_ 03/bioethanol. html 4

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

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

In Europe a starch factory consumes between 1, 000 and 2, 000 tonnes of cereals each day. http: //www. aac-eu. org/html/everydayuses. html 7

Carbohydrates C H O H sugar components O H H O – open chains – ring structures H H O H C H 2 O H O o chair H OH H Starch the chemical O HO HO H H H OH HO

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

multiple links (ribbons and helices)

Amylose and Amylopectin

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

Amylose helix Pitch 0. 8 nm 6 residues per turn Double helix, association of 2 left handed helices

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

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

Starch • complex assembly of two macromolecules • amylose Glucose units linked (mostly) 1 -4 Number of glucose units ~ 250 -5, 000 15 -30% weight

Amylopectin Racemose model Glucose units linked 1 -4 and some 1 -6 linkage 70 -85% by weight number of glucose units ~ 10, 000 -100, 000 branch chains ~20 glucose units only one reducing end

Diagram of the starch granule organisation

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

Can tell the structure of the helices by X-ray wavelength 10 -10 m

Packing of the molecules to form a starch granule

Polarised Light-optical microscope

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

Growth ring Wheat starch granule, erosion during germination

(Gallent et al, 1997) 25

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

Starch cereal Storage polysaccharides examples wheat rice oat barley seeds pea tuber potato cassava / tapioca /manioc stem sago

Different starches granule Amylose Molecules Degree per granulepolymerisaton um % DP(amylose) Starch Corn regular waxy Potato Rice Sago Cassava Wheat 5 --25 15 --100 3 --8 20 --60 5 --35 26 ~1 22 17 25 10*10 -12 800 0. 01*10 -12 10*10 -12 3000 4*10 -12 5*10 -12 3000 800 From Pomeranz 1991 Swinkels, 1985

Remember that with the starch can come other components within the granule wheat Internal components maize potato Amylose 26 -31 24 -32 23 Lipids Protein 0. 48 -1. 12 0. 20 -0. 33 0. 6 -0. 8 0. 27 -0. 39 0. 05 0. 2 0. 06 0. 1 0. 02 Ash Phosphorus 0. 4 0. 08* Note : the amount of amylose depends on the method used to measure

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 goes from red, red-purple, blue depending on chain length) 645 nm d. p. 366 or higher but long chains of the amylopectin, often B 1 chains, can do this) c)hot water soluble fraction (amylose not water soluble at above 2 mg/ml, it precipitates)

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

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

Modified starch 33

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 30 -100%, this is reversible.