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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)

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starch
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
slide2

Unheated starch granule

Heated starch granule

starch forms
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

Characteristics of Amylose and Amylopectin

Characteristic Amylose Amylospectin

crystal structure forms
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.
native starches
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
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
slide14

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

types of food starches
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.
slide17

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

slide18

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
slide19

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.

derivatizing reagents
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
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
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
Problems
  • Failure to hydrate
  • Retrogradation
  • Amylases
  • Loss of viscosity
slide26
Pasting characteristics of different native starches(from Food Additives, 2nd Ed 2002, Brane et al. Eds)
gelatinization of starches
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
paste properties of native starches
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

Summary of cornstarch paste properties
exogenous and endogenous effects on starch pasting characteristics
Exogenous and Endogenous Effects on Starch Pasting Characteristics
  • Acid
  • pH
  • Sugar
  • Lipids
  • Proteins
  • Shear
processing effects
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
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
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.
slide37
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.

slide38

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.

applications
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
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
in the selection of a starch for a food application consideration needs to be given to
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 to43
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
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

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.
slide46

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.

slide47

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

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

Graininess

Starch not cooked

Consider pregelled starch. Adjust water; adjust processing time and/or temperature

Common problems, causes and possible solutions for dairy foods
selection of starches for extruded products

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

Common problems, causes and possible solutions for extruded products
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 gel

Surimi, hot applications

High water holding capacity

Blends of native and modified waxy starch

Used as a filler; blends used to improve gel moistness

Selection of starches for meat products
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

Common problems, causes and possible solutions for meat products
take home
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