Starch (pati)
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
Unheated starch granule
Heated starch granule
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,
Characteristics of Amylose and Amylopectin
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
Characteristic Amylose Amylospectin
Amylose
Amylopectin
Amylopectin General
Structure
Amylopectin structure (Chaplin, 2004)
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.
Types of crystal structure in amylopectin (Chaplin, 2004).
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
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
Starch Viscosity, mild heat, neutral
Viscosity, high heat, acidic
Shear resistanc e
Freeze -thaw stabilit y
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
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.
Modified Starches
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 Starch - O-P-O-Starch
Reagent Derivative
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 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
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.
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
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”
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
Problems
Failure to hydrate
Retrogradation
Amylases
Loss of viscosity
Amylose
Swelling Collapse Aggregation C
Viscosity E
D
B
A Time
A = Paste initiation temperature B = Peak Paste Time
C = Peak Viscosity D/C = Stability ratio E/D = Set back ratio
50 65
Temp 90 95 80
Amylose
Swelling Collapse Aggregation C
Viscosity E
D
B
A Time
A = Paste initiation temperature B = Peak Paste Time
C = Peak Viscosity D/C = Stability ratio E/D = Set back ratio
50 65
Temp 90 95 80
Amylose
Swelling Collapse Aggregation C
Viscosity E
D
B
A Time
A = Paste initiation temperature B = Peak Paste Time
C = Peak Viscosity D/C = Stability ratio E/D = Set back ratio
A = Paste initiation temperature B = Peak Paste Time
C = Peak Viscosity D/C = Stability ratio E/D = Set back ratio
50 65
Temp 50 65 90 95 80
Temp 90 95 80
Starch Gelation and Pasting
Pasting Cycle
Pasting characteristics of different native starches
(from Food Additives, 2
ndEd 2002, Brane et al. Eds)
Gelatinization of starches
Type % Amylopectin % Amylose Gelatinization Range °C Granule Size
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
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
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
Exogenous and Endogenous Effects on Starch Pasting Characteristics
Acid
pH
Sugar
Lipids
Proteins
Shear
Viscosity
Time
Cornstarch + water
Cornstarch + water + 1.7% acetic acid
Viscosity
Time
Cornstarch + water
Cornstarch + water + 1.7% acetic acid
Viscosity
Time
Cornstarch + water
Cornstarch + water + 1.7% acetic acid
Effect of Acid on Starch Pasting
pH 4
pH 10
pH 2.5
V is co si ty
Time
pH 4
pH 10
pH 2.5
V is co si ty
Time
Effect of pH on Pasting of Corn
Starch
Effect of Sugars on Pasting of Corn
Starch
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
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:
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 .
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.
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
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
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
Lots of Choices
In the selection of a starch for a food application, consideration
needs to be given to:
Flavour
Texture
Body
Appearance
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
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?
Origin Type Applicat ion
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.
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.
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
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
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
Common problems, causes and possible solutions for extruded products
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
Selection of starches for meat products
Product 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 Surimi, hot gel
applications
High water
holding capacity
Blends of native and modified waxy starch
Used as a filler;
blends used to improve gel moistness
Common problems, causes and possible solutions for meat products
Problem 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
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
