Functions of Starches in Foods
|
Function |
Example |
|
Thickener |
Puddings |
|
Sauces |
|
|
Pie fillings |
|
|
Binder |
Formed meats |
|
Breaded items |
|
|
Encapsulation, Emulsion Stabilizer |
Flavors |
|
Bottler's emulsions |
|
|
Coating |
Candies |
|
Water Binder |
Cakes |
|
Free Lowing/Bulking Agent |
Baking powder |
|
Releasing Agent |
Candy making |
|
Fat Replacer |
Salad dressings |
|
Baked goods |
|
|
Dairy products |
Approximate Amount of Starch in Food Products
|
Food |
Starch (%) |
|
|
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 |
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Pourable |
1.5-2.3 |
|
|
Spoonable |
2.8-5.0 |
|
|
Gum candy |
5-12 |
|
|
Harvard style beets |
2-4 |
|
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Marshmallows |
0.5-1.0 |
|
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Pie crust |
0.5=1.2 |
|
|
Pie filling |
3-5 |
|
|
Pudding |
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Canned |
4.5-6.5 |
|
|
Cooked |
5-8 |
|
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Instant |
3-7 |
|
|
Sauces |
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Thick |
4-6 |
|
|
Gravy |
1.0-2.5 |
|
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.
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
|
Starch Type |
Viscosity |
Clarity |
Gel |
Shear Stability |
|
Cereal |
||||
|
Regular |
Short |
Opaque |
Strong |
Good |
|
Waxy |
Long |
Clear |
Very Weak |
Poor |
|
Root, tuber |
Clear to slight |
Weak |
Poor |
|
|
High Amylose |
Very Short |
Very Opaque |
Very Strong |
Stable |
Crosslinking Agents for 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 |
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 |
Brabender Amylograph
This instrument measures the viscosity of a starch slurry while heating the slurry at a constant rate to a preset temperature, with stirring. Typically, 5% starch is used and a holding period followed by cooling is also usual.
The curves from this analysis can help to determine:
Gelatinization temperature
Peak viscosity
Stability to shearing
"Set back" gelling upon cooling
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