Starch
Chapter 13
Introductory Foods, 13th ed.Bennion and Scheule
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Nutrition Starch – in breads, cereals, grains, potatoes,
and other foods – provides 70-80% of the world’s calories
Breads and cereals offer, in addition to starch, vitamins and minerals.
Introductory Foods, 13th ed.Bennion and Scheule
© 2010 Pearson Higher Education,Upper Saddle River, NJ 07458. • All Rights Reserved.3
Sources Parts of plants
Seeds Roots Tubers
Foods Cereal grains (i.e. corn, wheat, rice, oats) Legumes (i.e. dried beans) Roots and tubers (i.e. potato, tapioca, arrowroot)
Introductory Foods, 13th ed.Bennion and Scheule
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Milling Wet milling
Process used to separate starch from grains and tubers.
Introductory Foods, 13th ed.Bennion and Scheule
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Starch Molecule
Starch is a polysaccharide.
Polysaccharide is made up of hundreds or thousands of glucose molecules.
Terminology Polysaccharide – a complex carbohydrate. Glucose – a monosaccharide or simple sugar.
Introductory Foods, 13th ed.Bennion and Scheule
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Composition and Structure Starch molecule composed of many linked glucose
molecules
Two types or fractions Amylose
Long, chainlike molecule Gelling characteristics
Amylopectin Branched, bushy structure Thickening / cohesion properties
Introductory Foods, 13th ed.Bennion and Scheule
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Terminology Gel
Colloidal dispersion that holds shape
Colloidal Intermediate between small particles in solution
and large particles in suspension
Introductory Foods, 13th ed.Bennion and Scheule
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Composition and Structure Starch granule
Starch is deposited in plants in organized units called granules.
Starch molecules structured to form crystalline-like patterns in the granule With polarized light, a Maltese cross pattern can be
observed under microscope Called birefringence Pattern disappears when starch is heated
Introductory Foods, 13th ed.Bennion and Scheule
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Kinds – Native Starches Cornstarch Tapioca Wheat Potato Rice Arrowroot Sago
Introductory Foods, 13th ed.Bennion and Scheule
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Kinds – Improved Native Starches Developed through plant breeding or genetic
engineering
No physical or chemical modification of the starch
Introductory Foods, 13th ed.Bennion and Scheule
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Kinds – Modified Starches
Chemical or physical modifications may be used to change function in food preparation.
Hydrolysis or acid-converted Cross-linked or cross-bonded Substitution or stabilization Physically modified
Instant or pregelatinized Cold-water swelling Heat treated
Introductory Foods, 13th ed.Bennion and Scheule
© 2010 Pearson Higher Education,Upper Saddle River, NJ 07458. • All Rights Reserved.12
Modified Starch
Hydrolysis or acid-converted starch “Thin-boiling starch” Low viscosity paste Produces stiff gel Useful in confectionary industry
Cross-linked or cross-bonded Lower viscosity and increase temperature for hydration Resistant to shear or stirring Greater tolerance of heat Useful for canned soup, spaghetti sauces, and pie
fillings
Introductory Foods, 13th ed.Bennion and Scheule
© 2010 Pearson Higher Education,Upper Saddle River, NJ 07458. • All Rights Reserved.13
Modified Starch Substitution or stabilization
Prevents retrogradation Improves clarity Reduces syneresis Useful for frozen or refrigerated starch-thickened foods
i.e. “clear gel” starch
Physically modified – Instant starch Will absorb cold water Useful in “instant” pudding
Introductory Foods, 13th ed.Bennion and Scheule
© 2010 Pearson Higher Education,Upper Saddle River, NJ 07458. • All Rights Reserved.14
Kinds - Resistant Resistant starch is not digested by human body
Four main types RS1 RS2 RS3 RS4
May be used in food to increase fiber content
Introductory Foods, 13th ed.Bennion and Scheule
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Effect of Heat and Cooling Dry heat
Starch becomes more soluble Reduced thickening ability Dextrinization Brown, nutty, toasted flavor develops
Examples Brown roux and Espagnole sauce A higher proportion of starch to liquid is needed
Introductory Foods, 13th ed.Bennion and Scheule
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Effect of Heat and Cooling
Moist heat Starch granules insoluble in cold water Colloidal dispersion produced with heating Starch paste
Introductory Foods, 13th ed.Bennion and Scheule
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Changes with Moist Heat and Cooling Gelatinization
With heat, starch granules absorb water and swell Increased viscosity and increased translucency
Pasting Gel formation or gelation
Occurs with cooling
Retrogradation Occurs with standing after gel formation Amylose molecules associate more closely Gel network shrinks
Syneresis
Introductory Foods, 13th ed.Bennion and Scheule
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Factors Affecting Starch Pastes Temperature and time of heating
Agitation and stirring
Acidity
Addition of other ingredients
Introductory Foods, 13th ed.Bennion and Scheule
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Factors Affecting Starch Pastes Temperature and time of heating
Thicker if cooked quickly If undercooked
Raw starch flavor Less smooth and silky
Agitation or Stirring Stirring desirable to disperse starch If excessive – starch granules may rupture
Slick and pasty mouthfeel
Introductory Foods, 13th ed.Bennion and Scheule
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Factors Affecting Starch Pastes Acidity (pH)
May cause fragmentation and hydrolysis Decrease of thickening power Add acid late in cooking process
i.e. lemon pie
Introductory Foods, 13th ed.Bennion and Scheule
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Factors Affecting Starch Pastes Addition of other ingredients
Sugar Raises temperature of gelatinization May decrease viscosity
Fats and proteins Delay hydration of starch Lowers rate of viscosity development
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Starch Cookery Combining starch with hot liquids
Roux Slurry
Introductory Foods, 13th ed.Bennion and Scheule
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Mother Sauces Thickened with starch
Béchamel Velouté Espagnole
May be thickened with starch Tomato
Thickened with an emulsion Hollandaise
Introductory Foods, 13th ed.Bennion and Scheule
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Cream Soups
Often use mirepoix for flavoring Thickened with
Starch (roux or slurry) Cream Pureed starchy vegetables (i.e. potatoes)
Curdling Acid (i.e. tomatoes) Freshness of milk/cream Higher fat milk/cream is more stable than low or nonfat
milk
Introductory Foods, 13th ed.Bennion and Scheule
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Starch-Thickened Desserts
Typical starch choices Corn starch
Clear and glossy Flour Tapioca
Separate starch by mixing with sugar then cold liquid
Cook starch mixture before adding eggs Temper eggs
Introductory Foods, 13th ed.Bennion and Scheule
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Microwave Cooking of Starch Best for small batches
Stop microwave and stir in approximately once every 1 minute
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