Starch

1. Starch • Widely used as a food ingredient for many purposes. • A very wide selection of starches, both native and modified (National Starch has >200 different starches for sale for selected application) • Starch gelation and pasting characteristics altered by other ingredients and by processing conditions

2. Unheated starch granule Heated starch granule

3. Starch Forms • Starch is the primary carbohydrate source for growing seeds and leaf tissue development and is found in leaves, tubers, fruits and seeds. • Two general types of starch exist – amylose and amylopectin. Both are polymers of glucopyranose molecules, but differ in structure and functional properties,

4. Form Essentially linear Branched Linkage -1,4 (some -1,6) -1,4; -1,6 Polymer units 200-2,000 Up to 2,000,000 Molecular weight Generally <0.5 million 50-500 million Gel formation Firm Non-gelling to soft Characteristics of Amylose and Amylopectin Characteristic Amylose Amylospectin

5. Amylose

6. Amylopectin

7. Amylopectin General Structure

8. Amylopectin structure (Chaplin, 2004)

10. Crystal Structure Forms • The form depends upon the source of the granules. • Type A crystal structure is found in most cereals, whereas • Type B is found in some tubers and high amylose cereal starches. • Some plants have both A and B and are desginated Type C. When starches are heated in the presence of lipid, a different crystal structure may be formed, which is called Type V.

11. Types of crystal structure in amylopectin (Chaplin, 2004).

12. Native Starches • The most common native starches are corn (maize), rice, wheat, potato, tapioca (cassava) and waxy maize. • Except for waxy maize, these starches generally contain from 15-27% amylose. • Waxy maize and other waxy native starches generally contain less than 2% amylose. • High amylose starches contain more than 30% amylose and have quite different properties. They: • Are difficult to gelatinise > 100° C • Can form films and fibres Have more helical structure - may entrap fatty acids – retards granule swelling

13. Differences in Native Starches • Vary in amylose and amylopectin content • Vary in crystal structure • Vary in gelation and pasting characteristics • Vary in minor components that can be incorporated within the structure of amlyose and amylopectin • Phoshate esters • Phospholipids • Proteins

14. Properties of selected commercial starches (National Starch) Starch Viscosity, mild heat, neutral Viscosity, high heat, acidic Shear resistance Freeze-thaw stability Comments Tapioca (N) 3 3 5 3 Bland flavoured, fillings and canned Tapioca (N) 3 3 5 2 Process tolerant, short texture; dairy products, soups and sauces Tapioca (CL) 4 4 4 6 High viscosity, dairy products Potato 6 2 2 2 Rapid hydration, high viscosity; meat, sauces snacks Corn 3 4 5 3 Process tolerant, low hot viscosity; dressings and cereals Waxy maize, cross linked 4 5 4 6 Freeze thaw stability; frozen foods, fillings and sauces

15. Types of Food Starches • Unmodified • Native starches: Corn, wheat, etc. • Pregelatinized starches • Modified • Acid thinned - hydrolyze to reduce molecular weight • Crosslinked - Chemically linking OH's from two adjacent molecules. Toughens granule. Adds acid and heat stability • Derivatized - Add bulky groups to starch to reduce retrogradation. Changes hydrophobicity • Crosslinked-Derivatized - Does both • Oxidized - reduces retrogradation.

16. Modified Starches

17. Reagent Derivative Epichlorhydrin Starch - O-CH2-CHOH-CH2-O-Starch Sodium Trimetaphosphate Starch - O-P-O-Starch Phosphorus Oxychloride Starch - O-P-O-Starch Acrolein Starch-O-CH2-CH2-C-O-Starch Cross-linked starches make up about 25% of all starches used in foods. The four major cross-linking agents are shown in Table 7. In addition to different cross-linking agents, the degree of cross-linking varies. The details of the cross-linking of commercial starches remain proprietary to the company making the starch. Table 7: Cross-Linking Agents for Starch

18. Cross-linked starches make up about 25% of all starches used in foods. The four major cross-linking agents are shown below. In addition to different cross-linking agents, the degree of cross-linking varies. The details of the cross-linking of commercial starches remain proprietary to the company making the starch. • Reagent Derivative • Epichlorohydrin Starch - O-CH2-CHOH-CH2-O-Starch • Sodium Trimetaphosphate Starch - O-P-O-Starch • Phosphorus Oxychloride Starch - O-P-O-Starch • Acrolein Starch-O-CH2-CH2-C-O-Starch

19. Derivitized StarchesThe five primary derivatized starches, the derivatising agents and the degree of substitution are shown in the following table. The starch properties will vary with the type of derivatised starch and the degree of substitution. Many companies made “double derivatized” starches that are both cross-linked and derivatized.

20. Derivatizing Reagents • Reagent Derivative D.S. • Acetic anhydride Starch acetate 0.05 -0.10 • Vinyl acetate Starch acetate 0.05 - 0.10 • Propylene Oxide Hydroxylpropyl starch 0.05 - 0.20 • Sodium tripolyphosphate Starch phosphate 0.01 - 0.02 • Succinic anhydride Succinylated starch 0.02 - 0.05

21. Gelatinization and Pasting • “Starch gelatinisation is the collapse (disruption of molecular order) within the starch granule, manifested in irreversible changes in properties such as granular swelling, native crystalline melting, loss of birefringence and starch solubilisation. The point of initial gelation and the range over which it occurs is governed by the starch type, concentration, method of observation, granular type and heterogeneities within the granule population under observation.” • “Pasting is the phenomenon following gelatinisation in the dissociation of starch. It involves granular swelling, exudation of molecular components from the granule; and eventually the total disruption of the granules”

22. Factors Affecting Hydration • Amount of water • Availability of water • Time and Temperature of heating • Starch type • Corn vs. rice etc. • Crosslinking • Derivitization • Pregelatinization • pH • Saturated monoglycerides

23. Problems • Failure to hydrate • Retrogradation • Amylases • Loss of viscosity

24. Starch Gelation and Pasting

25. Pasting Cycle

26. Pasting characteristics of different native starches(from Food Additives, 2nd Ed 2002, Brane et al. Eds)

27. Gelatinization of starches • Type % Amylopectin % Amylose Gelatinization Range °C Granule Size m • Corn 73 27 62-72 5-25 • Waxy Corn 99 1 63-72 5-25 • High Amylose 20-45 55-80 67-100+ 5-25 • Potato 78 22 58-67 5-100 • Rice 83 17 62-78 2-5 • Tapioca 82 18 51-65 5-35 • Wheat 76 24 58-64 11-41

28. Paste Properties of Native Starches • Starch Type Viscosity Clarity Gel Shear Stability • Cereal • Regular Short Opaque Strong Good • Waxy Long Clear V Weak Poor • Root, tuber Clear-opaque Weak Poor • High Amylose V Short V Opaque V Strong Stable

29. Type Comments Native Poor freeze thaw stability High amylose Granules- birefringent Acid modified Decreased hot paste viscosity Hydroxy-ethyl Increased paste viscosity - low retrogradation Phosphate Reduced gel at refrigeration temperature - low retrogradation Cross-linked Reduced peak viscosity, increased stability; freeze thaw stability Acetylated Good paste clarity and stability Summary of cornstarch paste properties

30. Exogenous and Endogenous Effects on Starch Pasting Characteristics • Acid • pH • Sugar • Lipids • Proteins • Shear

31. Effect of Acid on Starch Pasting

32. Effect of pH on Pasting of Corn Starch

33. Effect of Sugars on Pasting of Corn Starch

34. Processing Effects • Processes that are known to affect the pasting • characteristics of starches include: • ·Order of addition of ingredients • ·Temperature achieved • ·Rate of temperature rise • ·Duration of heating • ·Rate of cooling • ·Storage temperature • ·Shear

35. Retrogradation • Solubilised starch polymer and remaining insoluble granular fragment tend to re-associate after heating. The re-associating is termed “Retrogradation”. • Retrogradation has been defined as follows: • “Retrogradation is a process which occurs when starch chains start to re-associate into an ordered structure. In its initial phase, two or more starch chains may form a simple junction point, which then may develop into more extensively ordered regions. Ultimately, under favourable conditions, a crystalline order appears.” • Generally, amylose-containing starches show greater retrogradation. Factors relating to retrogradation include:

36. Factors relating to retrogradation include: • · Amount of branching • · High amylopectin starches - e.g., waxy maize shows no retrogradation when frozen • · Hydrogen bonding between OH groups in amylose in gelatinised starches during cooling • · Water forced out of gel structure (syneresis) & • Starch insolubilized.

37. Amylopectin also plays a role in retrogradation over time. Short-term retrogradation is largely associated with amylose (which reaches a limit in 2 days), whereas long-term retrogradation is thought to involved amylopectin (reaching a limit is 40 days) The botanical source is important in respect to retrogradation, not only for starches that differ in amylose content, but also for starches with very similar amylose content. For retrogradation to occur there must first be an aggregation of the chains. Amylopectin from potato and tapioca (B type starches) retrograde to different degrees and this has been related to difference in short branch chains.

38. Function Example Thickener Puddings, sauces, pie fillings Binder Formed meats; breaded items; pasta Gelling agents Confections Encapsulation, Emulsion Stabilizer Flavours, bottlers emulsions Coating Candies, glazes, icings and toppings Water Binder Cakes Free Lowing/Bulking Agent Baking powder Releasing Agent Candy making Texture modifier Processed cheese, meat products Fat Replacer Salad dressings, dairy products, baked goods Functions of starch in food systems and examples of how these are utilised in different food systems.

39. Applications • The amount of starch used in different types of foods ranges from 0.2% in beverage products to 12% is some candies. Use levels, except for gums & candies, generally fall into two general categories. • <1%: beverages, butter sauces, cake mix and icing and marshmallows • 2 – 5%: baby foods, spoonable salad dressings, Harvard style beets and creamed soups, cheese analogs

40. Approximate Amount of Starch in Food Products (%) • Baby foods 3-5 • Beverages (bottler's emulsions) 0.2-0.3 • Butter sauces 0.3-0.5 • Cake mix and icings 0.3-0.5 • Dressings • Pourable 1.5-2.3 • Spoonable 2.8-5.0 • Gum candy 5-12 • Harvard style beets 2-4 • Marshmallows 0.5-1.0 • Pie crust 0.5-1.2 • Pie filling 3-5 • Pudding • Canned 4.5-6.5 • Cooked 5-8 • Instant 3-7 • Sauces • Thick 4-6 • Gravy 1.0-2.5

41. Lots of Choices

42. In the selection of a starch for a food application, consideration needs to be given to: ·Flavour ·Texture ·Body ·Appearance

43. In the selection of a starch for a food application, consideration needs to be given to: • Formulation • How long is the shelf life of the food • High Acid or Low Acid • Processing conditions • High heat vs low heat • High shear vs low shear • Both high heat and high shear

44. Other Questions to ask in Selecting a Starch Is there sufficient moisture to hydrate the starch? ·Is the solids level to low or too high? ·How will lipids affect the starch and the resulting food? ·What salts and what salt levels are required in the food? ·What type and level of sugar is being used? ·Are there other hydrocolloids included in the formulation?

45. Origin Type Application Function Benefit Corn Native Soup mixes Thickener Body, mouth feel Corn Pre-gelled Puffed snacks Texture Improved processing Waxy maize Cross linked Salad dressing Stabiliser Body, gloss, stability Tapioca Cold water swelling Instant dairy products Texture Bland flavour, premium cook up texture Potato Native, cook up Dry mixes Thickener Rapid hydration, high viscosity Source, type, application, function and benefits of some starches in selected foods.

46. Starch types for different foods and applications Application Binding Viscosity building Film formation Texturising Soups and sauces - X, XS, PX, PXS -- X, XS, PX, PXS Bakery PN X, P, PX, PXS D, M P, X, PX, PXS, M Dairy N, A, M, X, XS, P, PX, PXS -- X, XS, PXS, A, NX, O, PO, M Snacks N, P, PN, PO, D --- --- -- Batters & coatings X, PX, O P, PX D O, PO, D. M Meat products N, X, XS, P ---- XS XS N=native; X = cross-linked; P=pregelatinised; S=substituted (derivatised); O=oxidised; A=acid hydrolysed; D=dextrin; M=maltodextrin. Where letters are together without a comma, all types are combined into a single product.

47. Product Requirements Best Starch Type Comments General Dairy Heat tolerant, shear tolerant, freeze-thaw stable, bland flavour Cross-linked and substituted Tapioca best from a flavour viewpoint UHT products More heat & shear tolerant Increase degree of cross-linking Frozen desserts Freeze-thaw stability most important Substituted Fat replacers in low fat products, cross-linked for better freeze thaw stability Dry mix applications Perform under low heating conditions Pregelled, low level of cross-linking, freeze- thaw stability Instant puddings and cheese sauces most common usage Yoghurt Acid stable Cross-linked Used to minimise syneresis Processed cheese Gelling characteristics Cross-linked waxy maize Selection of starches for dairy foods

48. Problem Possible causes Possible solutions Syneresis Poor freeze thaw stability; colloid system breakdown Decrease shear; Increase starch level, Increase cooking time and/or temperature; Use stabilised starch Runny texture Low solids content Increase starch; select different starch; decrease shear; check for amylases in other ingredients Graininess Starch not cooked Consider pregelled starch. Adjust water; adjust processing time and/or temperature Common problems, causes and possible solutions for dairy foods

49. Product Requirements Best Starch Type Comments Cereals “Bowl” stability High amylose starch Expanded snacks Good expansion Light to moderate cross- linked starch “Half” product Shear stability Pregelled, cold water swelling, moderate cross linked Single screw extrusion followed by baking Twin screw extruded products Shear, pressure and temp. stability Cross linked “cook-up” starches Selection of starches for extruded products

50. Problem Possible causes Possible solutions Lack of crispness Weak expansion Increase amylose if product exposed to high shear Poor cutting or shape Low dough viscosity or strength Increase amylosefor high shear; Increase amylopectin for low shear adjust moisture content Non-uniform sheet thickness High water absorption Decrease water content; choose starch with low water holding capacity Common problems, causes and possible solutions for extruded products