Starch: Production, Composition & Uses

• Starch

Starch Production and Composition

• Produced through photosynthesis, combining carbon dioxide, water, and sunlight to create oxygen and food
• Digestible due to glycogen stored in the liver and muscles
• Glycogen provides extra energy, and adipose tissue can convert to energy
• The term "amylum" means polymer
• The term "sterchen" means to stiffen, traditionally used to strengthen fibers in fabric
• Composed of 100% carbohydrates
• It is tasteless, odorless, lighter, more velvety, and whiter than regular flour
• Polysaccharide made entirely of glucose molecules exists as amylose (straight chain) and amylopectin (branched chain)
• Found as granules or grains in amyloplasts/leucoplasts in plants, including in seeds, roots, cereals, and legumes
• Starches vary

Amylose and Amylopectin

• The amount and proportions of amylose and amylopectin in starches varies with the plant source
• Properties and textural differences depend on the amylose-to-amylopectin ratio

Sources of Starch

• Roots/Tubers include potato, arrowroot, cassava, Gabi, Yautia, and Ube
• Fruits include Breadfruit and Banana (Saba)
• Cereals include Corn (waxy and non) and Wheat & Rice (waxy and non)
• Legumes include Chick Peas, Peanuts, Manggo, and Cow Peas

Pure Starch Characteristics

• It is a white, tasteless, and odorless powder that is insoluble in cold water and alcohol
• Protein is removed during processing, eliminating fiber
• Native starch is originally derived from its plant source
• Modified starch has altered structures using physical or chemical agents to improve properties
• Acid-modified starch affects gel formation, making it softer by weakening hydrogen bonds created by amylose

Amylose vs Amylopectin percentage across sources

• Arrowroot: 20.5% Amylose vs 79.5% Amylopectin
• Banana: 17% Amylose vs 83% Amylopectin
• Cassava: 18.6% Amylose vs 81.4% Amylopectin
• Corn: 28% Amylose vs 72% Amylopectin
• Potato: 17.8% Amylose vs 82.2% Amylopectin
• Rice: 35% Amylose vs 65% Amylopectin
• Tapioca: 16.7% Amylose vs 83.3% Amylopectin
• Wheat: 20% Amylose vs 80% Amylopectin

Amylose Characteristics

• Linear component of starch
• Contains 1,4-alpha-glycosidic bonds
• Molecular weight is less than 0.5 million
• Forms coils that can trap iodine, turning blue (every 6 glucose units can bind one iodine)
• Easily thickens and gels at a 5% concentration
• Retrogrades easily

Cornstarch

• Ideal for making gels because of its high amylose and amylopectin content
• High amylose content makes it harden easily, but this process is reversible

Amylopectin Characteristics

• It is the branched component of starch, therefore features more weight and complexity
• Contains 1,4-alpha-glycosidic bonds and 1,6-alpha-glycosidic bonds
• Molecular Weight: 50-500 million
• Limited coiling causes a purplish-red color when iodine is added
• Can thicken, but not gel, unless the concentration reaches 30%
• Less likely to retrograde

Comparison of Amylose and Amylopectin Content

• Starches generally contain more amylopectin than amylose (approximately 75% amylopectin and 25% amylose)
• Some starches consist of 100% amylopectin
• Roots/tubers typically contain more amylopectin than cereals
• Roots/Tubers: 80% amylopectin
• Cereals typically have 75% amylopectin
• Waxy corn and rice contain virtually all amylopectin (100%) Amylose is essential in the making of maja blanca by creating a bond outside and creating a 3D network.

Starch Composition

• Tapioca: 17% amylose, 83% amylopectin
• Potato: ~20% amylose, ~80% amylopectin
• Wheat: 25-26% amylose, ~75% amylopectin
• Corn: 24-28% amylose, ~75% amylopectin
• Waxy corn: ~0% amylose, ~100% amylopectin
• High amylose: ~75% amylose, ~25% amylopectin
• Rice: 22% amylose, 78% amylopectin

Starch Granule Structure

• Made in the cytoplasm of plant cells
• Amylopectin forms concentric circles with amylose dispersed between
• Held together by hydrogen bonds (weak bond; easily destroyed)
• The granule swells when heated in water (gelatinization)

Gelatinization

• Amylopectin is the major polymer in most starches (non-waxy 70-85%, waxy almost 100%)
• Starch properties like pasting and gel formation, are determined by the amylose-amylopectin content
• Thickening of starch granules increases the volume because water penetrates the water granules
• When starch heats in water, hydrogen bonds weaken, and water swells granules
• Water and then heat are important
• Amylose migrates out of the granule
• The H-bonding between water and amylopectin increases
• Reduced free water changes the viscosity of the starch mixture, thickening it

End Stage of Gelatinization

• Starch granules collapse and spill out free molecules creating a viscous state called "paste"
• The cooked starch is a combination of swollen granules and loose molecules after their collapse

Factors Influencing Gelatinization

• Kind and concentration of starch
• Heating rate and endpoint temperature
• Stress (agitation or stirring)
• Dextrinization
• Effects of added ingredients
• Cooling and storage conditions
• Thicker as starch temperatures increases
• Begins thickening usually starts at approximately 140 deg.F (60deg.C) Heated up to 100deg.C without much granule rupture
• Temperatures vary
• Starch with high concentration of amylopectin thickens at lower temperature
• Larger starch granules (ex. Potato) gelatinize at lower temperature

Gelatinization and Sugar

• Used together in pie fillings and pudding
• Sugar competes with starch for water, therefore there is less water available for gelatinization
• Delays gelatinization and decreases viscosity, but results to firmer gel
• Increases gelatinization temperature
• The more sugar added, the longer the delay due to hygroscopic ability

Gelatinization and Acid:

• Used together in fruit pie fillings (e.g. lemon, lime, and pineapple fillings)
• Acid breaks down starch molecules so the paste is thinner
• Reduces viscosity (watery)
• Acid effect can be minimized by adding after gelatinization or heating rapidly
• Soften/weaken the hydrogen bond

Gelatinization and Type of Starch:

• Best thickening ability: Potato Starch
• Worst thickening ability: Wheat Starch
• More amylopectin = more translucent = more stringy

Gelation

• Gel Formation
• As a starch paste cools, a gel forms
• Free amylose molecules lose energy as temperature decreases and hydrogen bonds form
• Bonds create a 3-dimensional network that holds the swelled granules in place
• Gel forms after the gelatinized sol has been cooled (usually below 100deg.F or 38deg.C)
• Setting of sol into a solidified mass; when gelatinized starch is cooled, amylopectin and water envelop to form a gel

Gelation and Other Effects:

• Heating at a moderate temperature and rate
• Enough amylose must be released from granule bursting
• Agitation during cooling disrupts the amylose network
• Should mix flavorings immediately after removing from heat

Effects of Added Ingredients:

• Sugar competes with starch for available water, delays gelatinization, and increases the required temperature
• The swollen granules become more resistant to mechanical rupture
• Acid weakens the ability of starches to thicken (pH >4.0) and results in a softer gel (dextrinization)
• Fats/Protein delays gelatinization by coating the starch and preventing it from absorbing water
• Milk and Egg increase the firmness of the gel

Retrogradation of Starch:

• Realignment of amylose molecules with reassociation of the linear amylose chains by hydrogen bonding
• Hydrogen bonds break and reform into more orderly crystals
• Accelerated by low temperature
• Can be reversed by low temperature with examples being refrigerated pudding or stale bread

Gelation and Starch Source:

• High amylopectin (less amylose) means the gel is softer
• Potato starch has high amylopectin (good thickening agent) but forms a soft gel
• Corn starch has less amylopectin (less effective thickening agent) but forms a stronger gel
• More amylose starch forms more opaque gels

Aging Gels (Syneresis):

• It is the loss of water from a gel
• Amylose molecules pull together, squeezing water out

Dextrinization:

• When starch is heated without water, bonds break throughout the starch, forming dextrins
• Dextrins have a sweetish taste and nutty flavor
• If not controlled, will proceed to carbonization (burning)

Starch Retrogradation in Rice Grain

• Gelation is sometimes referred to as the "early stage of dixtrinization"
• Raw rice features a crystalline structure
• Gelatinized starch features an amorphous structure
• Retrograded starch features a recrystallized structure People with diabetes should consume retrogradated rice because the structure of the starch is complex. As a result, digestion is resisted reducing absorption in the body.