Starches+Group+2

= Starch = = =

Plants store glucose as the polysaccharide starch. Polysaccharides consist of long chains of repeating units of glucose. The cereal grains (wheat, rice, corn, oats, barley) as well as tubers such as potatoes are rich in starch. Starch can be separated into two fractions--amylose and amylopectin. Natural starches are mixtures of amylose (10-20%) and amylopectin (80-90%). =﻿ = =What is Amylose ? = Amylose is a component of starch characterized by its straight chains of glucose units. Amylose contributes to the gelling property.

 (5)

=What is Amylopectin ? = Amylopectin is a highly branched polymer of glucose. Amylopecting does not have a gelling property and tends to be gummy.

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=Gelatinization = = =

This occurs when a starch such as rice, oats or pasts is heated in a liquid. The hot liquid causes the hydrogen bonds in the starch molecule to weaken and makes it swell from the intake of water.

Results within the lab:
 * ** Starch ** || ** Viscosity Hot ** || ** Viscosity Cold ** || ** Appearance ** || ** Thickness based on chart ** ||
 * Tapioca || Gummy || Gummy || Clear || 6.5 ||
 * Arrowroot || Gel like || Gel || Cloudy, shiny || 4.5 ||
 * Rice || Thin gel || Thick gummy gel || Cloudy, dark white || 5.0 ||
 * Cornstarch || Liquidy gel || Gummy gel || cloudy || 6.75 ||
 * Cornstarch plus potato || Thin gel || Thin gel || Cloudy || 3.25 ||
 * Cornstarch plus acid (vinegar) || Very liquid || liquid || White and cloudy || Too liquid to measure ||
 * Wheat Flour || Thin, liquidy || Gummy || Cloudy, yellow tint || 7.75 ||
 * Browed Flour || Liquid || Liquidy || Brown color || 1 tbs= 8.0 ||

Viscosity of Different Starches

Tapioca: When hot it appeared to be very gummy and kept this consistency even after it cooled. It was clear and had a viscosity of about 6.5

Arrowroot: In both hot and cool conditions this starch formed a nice cloudy and shiny gel with a viscosity of about 4.5

Rice: When hot this starch became a thin gel and as it cooled became a little more gummy and pastey. It also had a cloudy white appearance with a viscosity of 5.0

Cornstarch: At hot and cool temperatures the product was a thin cloudy gel that came to a 6.75 viscosity

Cornstarch with sugar: In both hot and cool conditions, the sugar kept the starch from forming a nice gel and it was thin, cloudy and gummy with a viscosity of 6.5

Cornstarch and acid: The acid completely destroyed the starches ability to gel and became very liquidy, white and cloudy in both hot and cool temperatures. A viscosity was not measured

Potato: This starch made perhaps the firmest gel coming with a viscosity of 3.25. At both hot and cool the potato starch formed a nice thick cloudy gel

Wheat Flour: After heating it, the gel formed became a whitish yellow color and was a very thin, liquidy gel. Its viscosity was measured out to 7.75

Browned Flour: The gel formed was brown and cloudy and the dry heat completely destroyed its gelling capabilities. In both hot and cool temperatures it was super liquidy and only one tablespoon was measured instead of two for it viscosity which came out to 8.0

It is known that the amount of amylose present in a starch will determine its gelling ability. Cornstarch is a good example of a starch high in amylose (28%) making a good cloudy gel. Tapioca and Potato in particular have percentages of amylose at 17% and 21% respectively. Since these numbers are a little lower they form nice clear gels which we discovered in our experiment, but we found them to be gummier then the Cornstarch.

Whether the starch forms a clear or cloudy gel, however, can come in handy when cooking food. When cutting into a nice cherry pie, its prettier when the fruit filling is nice, clear and shiny so a starch like tapioca may be used. In a stew, however, it's darker and the appearance may not necessarily be as important, therefore, a cloudier starch like Cornstarch could be used. This can be seen in the following two recipes:



Factors that influence gelatinization : water - water allows for absorption temperature - heat is needed to dissolve starch stirring - helps prevent lumps from forming and helps acid - weakens starches ability to thicken sugar - competes with starch for water because hydrophillic fat/ protein - coats starch and delays absorptiona and gelatinization

Gel Formation This is similar to the process of making gelatin. During the process as it cools either a sol (fluid starch paste) or a gel (semisolid paste) will form. The amount of amylose present will determine how well the gel forms.

Retrogradation: As the product formed in the process continues to cool the protein molecules in the starch will continue to contract tighter and tighter causing the water to seep out. This is often referred to as "weeping" or "syneresis." This happens because the amylose molecules are forming more bonds with each other and freezing will help speed this up.

An example from our lab includes when the beads of water on top of the pudding form.

=Dextrinization: = Dextrinization is when the gelling is lost. This occurs when starch is broken down to dextrin molecules, also occurs in the presence of dry-heat. Dextrinization increases the sweetness of the product, and reduces the thickening capability of the starch.



Toasting or browning of flour happens during a dry heating process. This is done in order to increase the sweetness of a product often giving it a nutty taste but it also reduces its ability to thicken into a gel. The starches inability to gel occurs because during the process of heating the starch molecules break down into dextrin molecules.

Types of Modified Starches: Cross-Linked Starches: starch molecules are chemically treated so that they stay linked together. A good example of this would be in fruit pies, rather than the fruit leaking out it stays firmly in place. It is used mostly for commercial products pizza and puddings. Oxidized Starch: is modified with chemical oxidizers making it less viscous and clearer than cross-linked starch. Since it has a powdery consistancy it is used to dust commercial products like marshmallows. Pregelatinized Starch: unlike untreated starch it does not need to be heated in liquid because it is already precooked. Instead, cooled water begins the expansion process of the starch molecules and is usually seen in commercial such as puddings.

<span style="color: #9a1935; font-family: 'Comic Sans MS',cursive;">The three main ingrediants in making a sauce includes a liquid, a thickening agent and seasoning. Starch is an important ingrediant in sauces because it is the thickening agent which the sauce relies on for its gelatinization and smooth texture.

Types of sauce thickeners:

<span style="font-family: 'Comic Sans MS',cursive;"> Roux : [|Roux]



<span style="font-family: 'Comic Sans MS',cursive;"> Beurre Manie : [|Beurre manie]

Slurry: <span style="font-family: 'Comic Sans MS',cursive;">[|] [|Slurry]

References: Picture 1 [] =Picture 2 []= =Picture 3 []= =﻿Picture 4 tp://www.google.com/imgres?imgurl=http://cook.dannemann.org.uk= =Starch. []= =Amylose.http://www.merriam-webster.com/dictionary/amylose<span style="color: #ff00ff; font-family: 'Comic Sans MS',cursive;">﻿ = =<span style="color: #000000; font-family: Arial,Helvetica,sans-serif;">Picture 5 and 6: [] = =Picture 7 []= =Picture 8- recipetips.com= =﻿Picture 9 - []= Cherry Pie- [] Old - Time Beef Stew- []