Starch (pati)

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Starch (pati)

• Widely used as a food ingredient for many
  purposes.
• A very wide selection of starches, both native
  and modified (National Starch has gt200 different
  starches for sale for selected application)
• Starch gelation and pasting characteristics
  altered by other ingredients and by processing
  conditions

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Unheated starch granule
Heated starch granule
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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,

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Characteristics of Amylose and Amylopectin
Characteristic Amylose
Amylospectin
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Amylose
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Amylopectin
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Amylopectin General Structure
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Amylopectin structure (Chaplin, 2004)
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(No Transcript)
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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.

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Types of crystal structure in amylopectin
(Chaplin, 2004).
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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 gt 100 C
• Can form films and fibres
•            Have more helical structure - may
  entrap fatty acids retards
• granule swelling

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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

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Properties of selected commercial starches
(National Starch)
 
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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.

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Modified Starches
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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
 
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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

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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.
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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

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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
  

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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  

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Problems

• Failure to hydrate
• Retrogradation
• Amylases
• Loss of viscosity

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

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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
•  

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Summary of cornstarch paste properties
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Exogenous and Endogenous Effects on Starch
Pasting Characteristics

• Acid
• pH
• Sugar
• Lipids
• Proteins
• Shear

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Effect of Acid on Starch Pasting
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Effect of pH on Pasting of Corn Starch
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Effect of Sugars on Pasting of Corn Starch
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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

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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

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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.

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• 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.

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Functions of starch in food systems and examples
of how these are utilised in different food
systems.
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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.
• lt1 beverages, butter sauces, cake mix and icing
  and marshmallows
• 2 5 baby foods, spoonable salad dressings,
  Harvard style beets and creamed soups, cheese
  analogs

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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

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Lots of Choices
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In the selection of a starch for a food
application, consideration needs to be given to
           
Flavour            
Texture             Body             Appearance
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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

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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?
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Source, type, application, function and benefits
of some starches in selected foods.
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Starch types for different foods and applications
Nnative X cross-linked Ppregelatinised
Ssubstituted (derivatised) Ooxidised Aacid
hydrolysed Ddextrin Mmaltodextrin. Where
letters are together without a comma, all types
are combined into a single product.  
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Selection of starches for dairy foods
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Common problems, causes and possible solutions
for dairy foods
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Selection of starches for extruded products
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Common problems, causes and possible solutions
for extruded products
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Selection of starches for meat products
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Common problems, causes and possible solutions
for meat products 
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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