Running head: STARCH
1
Starch Lab Report
By June Saxton
6/18/2013
Introduction
In this paper, we will examine how time, temperature, agitation, acidity and
different ingredients affect the gelatinization of cooked starch paste and how moist and dry heat
effect the cooking properties of starch as well as the effect of water temperature on starch
dispersion through the use of two different kitchen experiments.
Experiment A-Starch Principles
Materials and Methods
For this experiment the materials used were a glass measuring cup, a wire whisk,
tablespoon, a one quart pan, a muffin tin, cornstarch, flour, sugar, lemon and water. All the
mixtures were mixed using 2 tablespoons of starch and one tablespoon of water except the lemon
one which was mixed using 2/3 cup water and 1/3 cup + 2 tablespoons freshly squeezed lemon
juice and the cornstarch and sugar one was made with 1 cup water, 1/3 cup sugar and 2
tablespoons of corn starch. The starch and liquid were mixed together and whisked to make sure
there are no lumps in the pan. The pan was then placed on the stove and cooked over medium
heat, stirring constantly until it boiled for one minute. Each mixture was then poured into a
section of the muffin tin and filled to the top and allowed to cool. I placed the mixture in the
refrigerator for about 60 minutes because my house was 80 degrees and I did not feel that the
muffin cups could cool sufficiently. Since they were in a muffin tin, I was unable to unmold
them. Instead, I spooned them into small bowls.
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Results
Table 3.1 TABLE FOR THE EVALUATION OF STARCH GELS
Number Starch
Amount of Starch
Firmness
Appearance (Cooled
(Tablespoon)
(Cooled Paste)
Paste)
1
Flour
2
Runny/saucy
Barely gelled
3
Cornstarch
2
soft
Slightly gelled
5
Cornstarch, water, 2
firm
Well gelled
2
soft
Softly gelled
2
Medium
Gelled a little more
lemon juice
7
Flour, darkly
browned
8
Cornstarch and
1/3 cup sugar
than just cornstarch
Samples 1, 3, 5, 7 and 8
Samples 3 and 8 bottom
From left to right
Sample 5 top
Samples 1 and 7
Left to right
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Discussion
Cornstarch thickens a lot more than flour because it has twice the thickening power and
thickens faster when reaches the boiling point. It also contains more amylose. Flour takes longer
to cook and thicken (Who’s in the Kitchen, 2009). The addition of an acid to a starch paste
enhances the thickening power. I would recommend that a slurry be made and then cooked. Dry
heats effect on flour is to darken it. The longer it is cooked and the higher the temperature, the
darker that the resulting product will be. It also thickens a little more. Adding sugar to the starch
mixture helped it to thicken a little more than with just starch. Gelatinization occurs when a
starch is heated in water and the structure of the starch molecules if disrupted as water is
absorbed and starch granules swell. The starch thickens until peak viscosity is reached and it also
increases in translucency. Gelation occurs upon cooling of the gelatinized starch paste. Starches
containing a large portion of amylose form firmer gels than those that contain a lower
concentration (Benton & Scheule, 2010).
Experiment B-Effect of Water Temperature on Starch Dispersion
Materials and Method
For this experiment the materials used were water, flour, a glass measuring cup, a
tablespoon and saucepan.
Using the glass measuring cup 2 tablespoons of flour were stirred into 8 oz. of cold water.
The mixture was then allowed to stand for 10 minutes. To further observe the reaction of water
on starch, 1 cup of water was boiled in a 1-quart saucepan and 2 tablespoons of flour was added
to the boiling water while stirring constantly.
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Results
When cold water was first stirred in 1 cup of water, a temporary suspension was formed.
After standing for 10 minutes the flour settled the bottom. When flour was added to boiling
water and stirred while added, the flour granules swelled up and the gelatinization process was
started, but all the starch was not incorporated and lumps formed.
Mixed with water After settling-side After settling-top
Boiled for one minute
Discussion
Flour settles to the bottom of the container after a few minutes because adding cold water
to them only forms a temporary suspension which will settle after a few minutes (Conforti,
2008). Lumps form in a heated solution of flour and water because near the simmering point the
starch granules swell suddenly and huddle together. These lumps cannot be dissolved (Sawtelle,
2009). A starch slurry is a mixture of cold water and starch stirred together until the starch
dissolves (Who's in the Kitchen, 2009). This mixture is effective in preventing lumps in the
starch mixture because it makes it easier to incorporate the starch into the hot mixture. A slurry
made with flour requires a longer time to cook in order to thicken the mixture and this allows the
flour taste to cook out. Cornstarch has twice the thickening power of flour and works
immediately when a slurry of it added to hot liquids with no starchy taste (Who’s in the Kitchen,
2009).
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References
Bennion, M., & Scheule, B. (2010). Introductory foods. (13th ed.). Upper Saddle River, NJ:
Pearson Prentice Hall.
Conforti, F. D. (2008). Food selection and preparation, a laboratory manual. (2nd ed.).
Blackwell Pub.
Sawtelle, H. (2009, March 11). The sauce thickens - how to avoid lumps. Retrieved from
http://www.culinate.com/columns/ask_hank/thickening_sauces
Who's in the Kitchen? (2009, December). How to make (and use) a slurry. Retrieved from
http://howtoboilanegg.wordpress.com/2009/12/21/how-to-make-and-use-a-slurry/