Starches+Group+1

=Starches =



Starch is a polysaccharide consisting of long chains of repeating units of glucose. Starch is used as a thickening agent for sauces, edible film on gum, and a sweetener (Brown). Several types of foods contain starches such as cake mixes, breadings, dressings, ice cream, jams, meat products, etc. Plant starch contains two forms of polysaccharides: ** Amylose ** and ** Amylopectin. **


 * Amylose ** is a linear polymer made up of 500 to 2,000 glucose units (Brown, 393). Its structure is tightly packed which makes it more resistant to digestion than other starch molecules.



Amylose Picture

** Amylopectin ** is a highly branched polymer made up of 100,000 to 1,000,000 glucose units. 

Amylose components of starch are insoluble in water while amylopectin is soluble. High levels of amylose tends to cause gelling, while higher levels of amylopectin are considered non gelling, but somewhat gummy. The varying amylose amounts is what determines the texture. The amount and proportions of amylopectin and amylose vary according to the starch's plant source (Brown, 393).

What is Gelatinization?
Gelatinization occurs when starch granules are heated in a liquid. The heated liquid weakens the hydrogen bonds which are responsible for holding the starch molecule together. This is what causes the starch to absorb water and swell until their max thickness is reached (Brown, 394). There is an increased volume and gumminess that is associated with gelatinization, which drastically changes the texture of many foods. Gelatinization is dependent on several factors, including the amount of water, temperature, timing, stirring, along with the presence of acid, sugar, fat, and protein. and tapioca) ||= 133-158 (56-70) ||< Form viscous, long-bodied, relatively clear pastes; weak gel upon cooling. || sorghum, rice, and wheat) ||= 144-167 (62-75) ||< Form viscous, short-bodied pastes; set to opaque gel upon cooling. || sorghum) ||= 145-165 (63-74) ||< Form heavy-bodied, stringy, clear pastes; resistant to gelling upon cooling. || (corn) ||= 212-320 (100-160) ||< Form short-bodied pastes; set to very rigid, opaque get upon cooling. || (Table from Brown, 394)
 * ~ Critical Temperatures of Gelatinization ||~  ||~   ||
 * < **Starch Source** ||= **Critical Temperature, F (C)** ||< **Characteristics of Cooked Starch** ||
 * < Roots and tubers (potato
 * < Cereal grains (corn,
 * < Waxy hybrids (corn and
 * < High-amylose hybrids



What is Gel Formation?
Gel Formation or gelation, occurs after gelatinization. As the product cools a sol (fluid starch paste) or a gel (semisolid paste) forms. Not all starches will gel but those that do, gel forms after the gelatinized sol has been cooled, usually to below 100F (38C). Gel formation is dependent on the amount of amylose that is present.



What is Retrogradation?
Retrogradation occurs as bonds continue forming between amylose molecules, while the gel cools. As the gel cools and ages the gel contracts and water begins to seep out, this is also known as weeping. Freezing accelerates retrogradation so the best way to prevent this from occurring, is to use the gelled food as soon as possible. Frozen food products usually come from sources low in amylose, because of this process (Brown, 396).

What is Dextrinization?
The breakdown of starch molecules into smaller, sweeter-tasting dextrin molecules in the presence of dry heat. The sweetness of the resulting dextrins is due the break down of amylose and amylopectin, during toasting or browning. A side effect to dextrinized starches is the loss of their thickening power. This is because they have been broken down into smaller units, so more flour may be required to thicken gravy if the flour has been browned in the gravy-making process (Brown, 396).



Group 1 Lab Results: Thickening Power of Various Starches
**Amylose** || **Percent** **Amylopectin** || **Viscosity** **Rating (Hot)** || **Characteristics of Hot** || **Characteristics of Cool** || Wheat Flour || 28% || 72% || 14.25 || brown, dull, smooth, less viscous || lack of gelling because of dextrinization ||
 * **Starch** || **Percent**
 * Potato || 21% || 79% || 3.00 || cloudy paste || weak gel ||
 * Tapioca || 17% || 83% || 8.50 || glossy, clear paste, sticky || weak gel ||
 * Arrowroot || 17% || 83% || 6.25 || smooth, clear || weak gel ||
 * Rice Flour || 22% || 78% || 3.75 || white, smooth, opaque || weak gel, retro-degradation apparent after 30 min ||
 * Wheat Flour || 28% || 72% || 8.25 || shiny, opaque || firm gel ||
 * Browned
 * Cornstarch || 28% || 72% || 8.00 || smooth, cloudy, paste || opaque gel, appears thicker ||
 * Cornstarch with Acid* || 28% || 72% || 4.75 || smooth, cloudy, || gel appears thicker ||
 * Cornstarch with Sugar* || 28% || 72% || 6.25 || shiny, opaque || very glossy, weak gel ||

*Acid will weaken the gelling process and decrease the viscosity of the starch. *Sugar competes with starch for available water, this delays the gelling process. Our results for the Cornstarch additives did not have a decrease in viscosity. Two sources of error could be as follows: increased heat while cooking cornstarch with sugar, and pH level of acid added to cornstarch was not below 4.0. Also, cornstarch with acid may not have been cooked long enough because in principal it should have been thinner than it was.

Our Starches: Corn Starch, Corn Starch with Acid, Corn Starch with Sugar Corn Starch, Potato Starch, Tapioca Starch, Arrowroot Starch, Rice Starch, Wheat Flour Starch, Brown Flour Starch

We noticed that our starches each had their own qualities. Tapioca: seemed to be sticky. Potato: seemed to be gummy. Wheat flour: seemed to be smooth. Browned flour: seemed to be very thin.

How to choose the correct starch:
Generally, starches high in amylose such as wheat and corn are clear when hot and become cloudy when cold. Root starches such as tapioca and arrowroot contain mostly amylopectin and are clear when hot or cold and the viscosity becomes thinner after the cooked starch cools. (Corriher)

After looking at each of the starches we noticed that Corn Starch would be good in a blueberry pie filling because it's thick so it can hold everything together and it has a glossy look to it to make the pie look more presentable. However, a cherry pie would present best with a starch that is clear when hot or cold. A root starch such as tapioca or arrowroot would give the pie the clear, but thick coating. Corn Starch can also be used for cakes, since its a modified Corn Starch it will hold water long and help keep the cake from getting stale. Also the Tapioca Starch would be good for pudding, since the starch is glossy and transparent, it also had a sticky texture to it. Rice Starch would be good for pasta. For thickening a stir fry, you should use a starch that gives a clear coating such as cornstarch, without any flour products added. Arrowroot would be good for Gravy.

An Article on Starches:
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More about Starches:
Modified Food Starches are used as gelling agents, they maintain the right texture in frozen and microwaved foods. They can be used to thicken fat- free dairy products and can also make food bulkier without changing the nutritional value. There is no harm in using Mortified Food Starch. There are three types of Modified Starches: Cross-Linked: chemically treated starches that are linked together for heat resistance. Used for pizza, cheese and spaghetti. Oxidized: chemically treated starches with a clearer consistency, less viscous. Used for emulsions such as salad dressings and powder coatings. Pre-gelatinized: precooked, then dried. Cool water starts expansion, no heating required. Used for instant puddings and packaged gravies.

Starch is used to thicken most sauces. The preparation of thickened sauces utilizes three main ingredients. 1. Liquid - stock, milk or butter 2. Thickening agent - wheat flour starch for a cloudy appearance or cornstarch for a clear, glossy appearance 3. Seasonings - flavorings

Thickened Sauces Include: Roux - heated flour and butter foodproof.com

Beurre Manie - flour and butter unheated, but added gradually anyoneforseconds.wordpress.com

Slurry - cold water added to cornstarch or flour, then slowly added to simmering product thekitchn.com

How to make a Slurry:
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