Running head: STARCH

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

Numb

er

Starch Amount of

Starch

(Tablespoon)

Firmness

(Cooled

Paste)

Appearance

(Cooled Paste)

1 Flour 2  Runny/saucy  Barely gelled

3 Cornstarch 2  soft  Slightly gelled

5 Cornstarch,

water, lemon

juice

2  firm  Well gelled

7 Flour, darkly

browned

2  soft  Softly gelled

8 Cornstarch

and 1/3 cup

sugar

2  Medium  Gelled a little

more than just

cornstarch

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Samples 1, 3, 5, 7 and 8 Samples 3 and 8 bottom Samples 1 and 7

From left to right Sample 5 top Left to right

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

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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.

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

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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/

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