Starches+Group+5

Starches

Starch, the major digestible polysaccharide in our diets, is the storage form of glucose in plants. There are two types of plant starch:
 * ~ AMYLOSE ||
 * < [[image:amylose.jpg width="236" height="130"]] ||< Amylose is a digestible linear chain type of starch made of multiple glucose units. The glucose units are held together by alpha bonds. It is the varying amylose content that determines the texture of the starch containing food (Brown, 2011). Amylose is gels, so foods with higher levels of amylose are more likely to gel. Corn typically has 28 percent amylose and 72 percent amylopectin and waxy maize has 0 percent amylose and 100 percent amylopectin so corn will gel much more than waxy maize because it contains no amylose. ||
 * ~ AMYLOPECTIN ||
 * < [[image:amylopectin.jpg width="273" height="189"]] ||< Amylopectin is a digestible branched-chain type of starch composed of multiple glucose units, linked together by alpha bonds (Brown, 2011). Amylopectin is non-gelling and tends to be gummy. Digestive enzymes act only on the ends of the amylose and amylopectin molecules, thus the branching of the amylopectin offer more sites for the digestive enzymes to attach to. As a result this causes blood glucose levels to increase at a faster rate after digesting amylopectin than amylose (Byrd-Bredbenner, 2009). ||


 * Both amylose and amylopectin provide a great source of quick energy for plants and for the animals that consume the plants
 * They are found in foods such as potatoes, breads, pasta, beans, etc.
 * Foods in their natural state usually contain 25 percent amylose and 75 percent amylopectin
 * Amylose and amylopectin are to blame for stale bread. In fresh baked bread, fresh from the oven, the amylose and amylopectin are swollen and randomly positioned. In fresh bread, as it cools, the amylose molecules begin to come together and gel, which enables us to cut the bread shortly after baking. Stale bread occurs when the amylopectin molecules have also come together and crystallized, which completely changes the consistency of the bread. Stale bread can be revived by reheating (Brown, 2011). [|Video: How To Revive Stale Bread]

Modified Starches

some starches are modified so that they are more useful in food processing. The modification is done to affect the starch's gelatinization, heating times, freezing stability, cold-water solubility, or viscosity. There are three types of modified starches:

__Cross-Linked Starch__: has been chemically treated so that the starch molecules are closely linked together with cross-bridges. The cross-linking makes the starch more heat resistant, less effected by acid or sugar, and reduces the elasticity found in native starch. It is typically used in the commericial production of pizza, pie fillings, and puddings.

__Oxidized Starch__: is modified by exposing the starch to chemical oxidizers. Oxidized starch is whiter than unmodified starch, has increased clarity, and lower viscosity. They mainly function as emulsion stabilizers and thickeners, but are also used to dust food items like gum because of their powder like consistency.

<span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">__Instant or Pregelatinized Starch__: does not need to be heated in water for it to expand and gel. This starch is precooked and dried so that when cold water is added they quickly absorb the water and expand. The food industry most often uses this starch when manufacturing instant dry mix prodcuts like gravies, puddings, and sauces (Brown, 2011).

<span style="font-family: Arial,Helvetica,sans-serif; font-size: 20px; line-height: 29px;">Lab Results <span style="font-family: Arial,Helvetica,sans-serif; font-size: 16px; line-height: 23px;">In order to test the different starches in our lab we first created a slurry, which is when you add the starch ( 2 tablespoons in our case) slowly to cold water (1cup) until it is thoroughly mixed. (McWilliams, 2009) We then added each slurry to a medium heat and stirred until gel formation occurred. The results were mostly typical of what is known about the different starches.

<span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">There were many different outcomes of this lab as you can see in the pictures below which are of the cooled starch mixtures. You can even see retrogradation in the with the Rice Starch below, there is a bit of cracking happening on the top of the end product. There was also an example of dextrinization in the Browned Wheat Flour, though its not evident in the photo there was a difference in the way it reacted to the touch than the plain Wheat Flour as the browned wheat was much more liquid and less gelling than the wheat. If the flour had been browed more we could have seen greater results.

<span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">Different variations we also tested with the Cornstarch. We did one plain, one with added sugar and one with added vinegar. They each came out differently as you can see in the photos below. The one with sugar was very cloudy and a little less viscous than the plain. The mixture with vinegar was slightly cloudier and also less viscous than the plain.

<span style="font-family: Arial,Helvetica,sans-serif; font-size: 150%;">﻿Results Chart


 * **Starch** || **Viscosity Hot** || **Viscosity Cold** || **Appearance** || **Viscosity Chart** ||
 * Tapioca || Gel like || More gummy || Clear, when cooled trapped air bubbles || 7.25 ||
 * Arrowroot || Pretty solid, a little gummy || More solid || Very clear, glossy, also had air bubbles trapped || 6.0 ||
 * Rice || Less thick, gel like || Thickened more, started cracking (retrogradation) || White, not very smooth, matte || 6.5 ||
 * Cornstarch || Gel like || Thickened more || Clear, glossy || 6.25 ||
 * Cornstarch plus sugar || More runny than plain cs || Thickened a bit more || Cloudy, still glossy || 7.5 ||
 * Cornstarch plus acid || Even more runny than plain or with sugar || Gelled somewhat || Cloudy, still glossy || 9.25 ||
 * Wheat Flour || Soupy/ gravy like || Gelled more || White || 11.5 ||
 * Browed Flour || More Soupy than plain wheat || Less gelling, (dextrinization) || Browner in color || 12.25 ||
 * Potato Flour || Gummy || Thickened, more gunny || Clear || 4.5 ||

Result Photos
 * [[image:1000000062.JPG width="230" height="170" caption="Wheat Flour"]] || [[image:1000000063.JPG width="230" height="170" caption="Browned Wheat Flour"]] || [[image:1000000057.JPG width="239" height="176" caption="Rice Flour an example of Retrogradation"]] ||
 * [[image:1000000059.JPG width="230" height="171" caption="Potato Flour"]] || [[image:1000000064.JPG width="230" height="171" caption="Tapioca"]] || [[image:1000000065.JPG width="230" height="171" caption="Arrowroot"]] ||
 * [[image:1000000058.JPG width="230" height="171" caption="Cornstarch"]] || [[image:1000000061.JPG width="230" height="171" caption="Cornstarch and Vinegar"]] || [[image:1000000060.JPG width="230" height="171" caption="Cornstarch and Sugar"]] ||

Gelatinization:
====In the presence of water and heat, the intermolecular bonds of starch are broken down. The hydrogen bonding sites are able to engage more water and this dissolves the starch granule. The starch grains or flour particles absorb the liquid they are immersed in and when heated, the grains swell until they burst. There are some factors that influence gelatinization including the amount of water, temperature, timing, stirring, and the presence of acid, fat, sugar, and protein. There must be sufficient water present depending on the concentration of amylose and amylopectin in the starch.(Brown, 2011)Because starches do not dissolve in cold or room temperature liquids, they must be in heated water in order for granules to swell and burst. Stirring is essential to obtain a smooth consistency but over stirring will cause the granules to rupture prematurely. Acids added to the starch will weaken it ability to thicken, therefore any acidic fruit juices must be added to the mixture after gelatinization occurs. Excessive amounts of sugar added to the starch during gelatinization will result in a thick runny paste so it is important not to add too much sugar.(Brown, 2011)====

Gel Formation__﻿____﻿____﻿____﻿____﻿____﻿____﻿____﻿____﻿____﻿__:
====Although not all starches will gel, the gel formation will occur after gelatinized sol has had time to cool. Because amylopectin does not gel, the starch’s ability to gel depends on the presence of amylose molecules. The strong bond between the amylose molecules traps water in a three dimensional formation that increases the inflexibility of the starch mass. Cornstarch, which contains high amounts of amylose, makes for a good gelling agent but starches containing low levels, such as potato and tapioca, result in translucent gels.(Brown, 2011)====

Retrogradation:
====This reaction takes place in a gelatinized starch after it has been cooled at lower temperatures. The reaction is also known as weeping or syneresis and occurs as the gel ages. As the gel cools, bonds continue to form between amylose molecules, this process is accelerated by freezing so starches used in frozen foods often come from sources low in amylose.(Brown, 2011) The most efficient way to prevent retrogradation would be to use gelled foods as quickly as possible.====

Dextrinization:
====This reaction occurs in the presence of dry heat and results in a sweeter taste. The breakdown of starch molecules to smaller, sweeter, tasting dextrin molecules causes starches to loose their thickening power. For example, darkened flour used in Louisiana Gumbo contributes immensely to the flavor but very little to the consistency.(Brown, 2011)====

<span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">Starch is also used to thicken gravies, sauces, soups, stews, and pie fillings. To make a thickened sauce, three ingredients are needed:
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">Liquid
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">Thickening Agent
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">Seasonings

<span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">Selecting a Thickening Agent
 * [[image:BRM-557e9304752246fadd529019b5155452.jpg width="98" height="151" caption="Arrowroot"]] || * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">Does not alter or mask flavors
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">Does not make clear liquids cloudy
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">Uses: thickening agent for fruit sauces, puddings, salad dressings, dessert sauces, vegetable sauces, and meat glazes (Bob's, 2011).
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">Arrowroot is high heat sensitive and reaches its maximum thickening at lower temperatures. Because of this it is not ideal for making gravies or pie fillings. ||
 * [[image:BRM-571a681e89adac05a4527c2272bff7ba.jpg width="99" height="152" caption="Cornstarch"]] || * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">Gives off a slightly starchy taste
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">Does not thicken when mixed with acidic liquids
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">Gives a glossy appearance to sauces
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">Uses: thickening agent for pie fillings, puddings, sauces, and soups (Bob's, 2011). ||
 * [[image:BRM-27c044dcfdd73ab7f89a7f9a19dcc03f.jpg width="99" height="152" caption="Potato Flour"]] || * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">Gluten-free starch
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">Adds moisture to baked goods, which make it ideal for gluten-free baking
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">Uses: thickening agent for sauces, soups, and gravies (Bob's, 2011). ||
 * [[image:BRM-00bbe472ed4d1530ba6580c86c9df46f.jpg width="99" height="152" caption="Tapioca"]] || * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">Mild flavor
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">Transparent gloss to fruits
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">Can cause "fish eyes" in pie fillings, which occurs during the baking process when tapioca beads soften and rehydrate. This is why it is usually used in two-crust pies, instead of single crust pies
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">In muffins and cookies it adds structure without the grittiness that is associated with gluten-free baked goods
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">Uses: thickening agent for sauces, soups, and dips (Bob's, 2011). ||

<span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">Types of Thickeners
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">Beurre Maine: ||
 * < media type="youtube" key="PlJC0BChGO4" height="195" width="240" ||
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">Roux: ||
 * < media type="youtube" key="ml984sWWnx8" height="195" width="240" ||
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">Slurry: ||
 * media type="youtube" key="fFd1LOUeQds" height="195" width="240" ||
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">References **

Bredbenner, C., Moe, G., Beshgetoor, D., & Berning, J. (2009). Wardlaw's Perspectives in Nutrtion. 8th ed. New York, NY: Mcgraw-Hill. 158.

Brown, A. (2011). Understanding Food Principles and Preparations. 4th ed. Belmont, CA: Wadsworth Cengage Learning. 41, 381, 397.

<span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">﻿ "Amylose." Photo. Wordpress.com. (2006). Retrieved from [] (6 Mar 2011). <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;"> <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">﻿ "Amylopectin." Photo. Wordpress.com (2006). Retrieved from []. (6 Mar 2011).

Howcaste.com (2009). How to Revive Stale Bread.Video file. Retrieved from []. (6 Mar 2011).

McWilliams, Margaret. (2009) Illustrated Guide to Food Preparation. 10th ed. Pearson Education, Inc. Upper Saddle River, NJ. p. 139-141

"Tapioca," "Potato Flour," "Cornstarch," "Arrowroot."Photos. Bobsredmill.com (2011). Retrieved from []. (10 Mar 2011).

Bob's Red Mill. (2011). "Flours and Meals." Retrieved from []. (10 Mar 2011).

CULN120. (27 Oct 2010). Thickening Agent - Slurry. Video file. Retrieved from []. (10 Mar 2011).

CULN120. (27 Oct 2010). Thickening Agent - Roux. Video file. Retrieved from []. (10 Mar 2011).

Comfycuisine. (8 Dec 2010). Beurre Maine. Video file. Retrieved from []. (10 Mar 2011).