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

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. Characteristics of Amylose and Amylopectin
Characteristic Amylose Amylospectin
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
million
Gel formation
Firm
Non-gelling to soft

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)
Viscosity, mild heat, neutral
Viscosity, high heat, acidic
Shear resistance
Freeze-thaw stability
Comments
Tapioca (N) 3 5
Bland flavoured, fillings and canned 2
Process tolerant, short texture; dairy products, soups and sauces
Tapioca (CL) 4 6
High viscosity, dairy products
Potato
Rapid hydration, high viscosity; meat, sauces snacks
Corn
Process tolerant, low hot viscosity; dressings and cereals
Waxy maize, cross linked
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. Cross-linked starches make up about 25% of all starches used in foods
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
Epichlorhydrin
Starch - O-CH2-CHOH-CH2-O-Starch
Sodium Trimetaphosphate
Starch - O-P-O-Starch
Phosphorus Oxychloride
Reagent
Derivative
Acrolein
Starch-O-CH2-CH2-C-O-Starch

18. Cross-linked starches make up about 25% of all starches used in foods
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 Starches The 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
Vinyl acetate Starch acetate
Propylene Oxide Hydroxylpropyl starch
Sodium tripolyphosphate Starch phosphate
Succinic anhydride Succinylated starch

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
Waxy Corn
High Amylose
Potato
Rice
Tapioca
Wheat

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. Summary of cornstarch paste properties
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

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
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. Puddings, sauces, pie fillings
Functions of starch in food systems and examples of how these are utilised in different food systems.
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

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)
Butter sauces
Cake mix and icings
Dressings  
Pourable
Spoonable
Gum candy 5-12
Harvard style beets 2-4
Marshmallows
Pie crust
Pie filling 3-5
Pudding  
Canned
Cooked 5-8
Instant 3-7
Sauces  
  Thick 4-6
  Gravy

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

46. Starch types for different foods and applications
Binding
Viscosity building
Film formation
Texturising
Soups and sauces -
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
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. Selection of starches for dairy foods
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

48. Common problems, causes and possible solutions for dairy foods
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

49. Selection of starches for extruded products
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

50. Common problems, causes and possible solutions for extruded products
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

51. Selection of starches for meat products
Requirements
Best Starch Type
Comments
Bologna & frankfurters
High viscosity, high water holding capacity
Lightly or moderately cross linked and substituted
need to have products that are freeze/thaw stable
Surimi, cold applications
High water holding capacity
Blends of native and modified amylose- containing starches
Used as a filler; blends used to improve moistness of the gel
Surimi, hot applications
Blends of native and modified waxy starch
Used as a filler; blends used to improve gel moistness

52. Common problems, causes and possible solutions for meat products
Possible causes
Possible solutions
Poor water holding capacity
Lack of water-binding components
Add substituted, stabilised starch; use starch with high water binding capacity
Low freeze-thaw stability
Low level of modification
Increase degree of cross linking and or substitution
Poor bite, soft texture
Structure not fully developed
Check starch selection; add substituted, stabilised starch

53. Take Home Starches are very complex
Selection of a starch is related to the type of food and processing conditions
Lots of choices – different starches (both native and modified) give different characteristics to the food
Modified starches generally used when you need:
Resistance to shear
Resistance to heat
Resistance to acid
Reduced retrogradation
Product expected to have a very long shelf-life