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
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
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
50-500
million
Gel formation
Firm
Non-gelling
to soft
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 crosslinking 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
Reagent
Derivative
Epichlorhydrin
Starch - O-CH2-CHOH-CH2-OStarch
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 crosslinking agents are shown below. In addition to
different cross-linking agents, the degree of
cross-linking varies. The details of the crosslinking of commercial starches remain proprietary
to the company making the starch.

Reagent
Derivative
Epichlorohydrin
Starch
Sodium Trimetaphosphate
Phosphorus Oxychloride
Acrolein
Starch - O-CH2-CHOH-CH2-O-





Starch - O-P-O-Starch
Starch - O-P-O-Starch
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
0.10
Vinyl acetate
0.10
Propylene Oxide
0.20
Sodium tripolyphosphate
0.02
Succinic anhydride
0.05
Starch acetate
0.05 -
Starch acetate
0.05 -
Hydroxylpropyl starch
0.05 -
Starch phosphate
0.01 -
Succinylated starch
0.02 -






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
Starch Gelation and Pasting
Amylose
Swelling
Collapse
Aggregation
C
E
Viscosity
A = Paste initiation temperature
B = Peak Paste Time
D
C = Peak Viscosity
D/C = Stability ratio
E/D = Set back ratio
B
A
Temp
50
Time
65
90
95
80
Pasting Cycle
Pasting characteristics of different
native starches
(from Food Additives, 2nd Ed 2002, Brane et al. Eds)
Gelatinization of starches

Type
Size m
% Amylopectin % Amylose Gelatinization Range °C Granule








Corn
Waxy Corn
High Amylose
Potato
Rice
Tapioca
Wheat
73
99
20-45
78
83
82
76
27
1
55-80
22
17
18
24
62-72
63-72
67-100+
58-67
62-78
51-65
58-64
5-25
5-25
5-25
5-100
2-5
5-35
11-41
Paste Properties of Native Starches

Starch Type
Viscosity
Clarity
Gel
Short
Long
Opaque
Clear
Clear-opaque
V Opaque
Strong
V Weak
Weak
V Strong
Shear Stability







Cereal
Regular
Waxy
Root, tuber
High Amylose
V Short
Good
Poor
Poor
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

Effect of Acid on Starch Pasting
Viscosity
Cornstarch + water
Cornstarch + water + 1.7% acetic acid
Time
Effect of pH on Pasting of Corn
Starch
Viscosity
pH 4
pH 10
pH 2.5
Time
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
Coating
Flavours, bottlers emulsions
Water Binder
Candies, glazes, icings and
toppings
Cakes
Free Lowing/Bulking
Agent
Releasing Agent
Baking powder
Texture modifier
Processed cheese, meat products
Fat Replacer
Salad dressings, dairy products,
baked goods
Candy making
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)
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
0.2-0.3
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?
Source, type, application, function and benefits of some
starches in selected foods.
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
Potato
Native,
cook up
Dry
mixes
Thickener
Bland flavour,
premium cook
up texture
Rapid
hydration, high
viscosity
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
Dry mix
applications
Perform under low
heating conditions
Yoghurt
Acid stable
Pregelled, low
level of crosslinking, freezethaw stability
Cross-linked
Processed
cheese
Gelling characteristics
Cross-linked waxy
maize
Fat replacers in
low fat products,
cross-linked for
better freeze thaw
stability
Instant puddings
and cheese sauces
most common
usage
Used to minimise
syneresis
Common problems, causes and
possible solutions for dairy foods
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
Starch not cooked
Consider pregelled
starch. Adjust water;
adjust processing time
and/or temperature
Graininess
Selection of starches for extruded
products
Product
Requirements
Best Starch
Type
Cereals
“Bowl” stability
High amylose
starch
Expanded
snacks
Good expansion
Light to
moderate crosslinked starch
“Half” product
Shear stability
Twin screw
extruded
products
Shear,
pressure and
temp. stability
Pregelled, cold
water swelling,
moderate cross
linked
Cross linked
“cook-up”
starches
Comments
Single screw
extrusion
followed by
baking
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
Surimi, cold
applications
High viscosity,
high water
holding
capacity
High water
holding capacity
Surimi, hot
applications
High water
holding capacity
Lightly or
moderately
cross linked
and substituted
Blends of native
and modified
amylosecontaining
starches
Blends of native
and modified
waxy starch
need to have
products that are
freeze/thaw
stable
Used as a filler;
blends used to
improve
moistness of the
gel
Used as a filler;
blends used to
improve gel
moistness
Bologna &
frankfurters
Common problems, causes and
possible solutions for meat products
Problem
Possible causes
Possible solutions
Poor water holding
capacity
Lack of water-binding
components
Low freeze-thaw
stability
Low level of
modification
Add substituted,
stabilised starch; use
starch with high water
binding capacity
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
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