Page Banner

United States Department of Agriculture

Agricultural Research Service

Science Projects for Students
headline bar

Amylose Content Experiment-
For Students Ages 10+

Explore these Links to Science for Students

 

 


 

Amylose Content Experiment

Background Information
Food contains various types of molecules. Those, which exist in food in the greatest amounts, are proteins, fats, and carbohydrates. After food is eaten by humans, carbohydrates are digested, or broken down, into a form that our bodies are able to use for energy. Just as a car today needs gasoline as its energy source, humans need carbohydrates as their source of energy. Carbohydrates contain a group of large molecules known as starch. Examples of foods which are largely made-up of starch are crops known as cereal grains such as rice (e.g. rice cakes), wheat (e.g. bread), and corn (e.g. corn flakes). Starch exists as two different types of molecules known as: amylose and amylopectin. The shape of amylose is similar to that of a spring. The quantity of amylose in rice kernels has a big impact on the properties of cooked rice kernels. That is, rice with little amylose will be sticky and soft. But rice with a large amount of amylose will be harder and not sticky. People in some areas of the world tend to prefer rice that is soft and sticks together (low in amylose) such as in Japan and Korea. While in other areas such as India and Pakistan, people generally prefer rice that is harder and not sticky (high in amylose). Consumers in the United States choose rice with various types of cooking properties because they have various ethnic backgrounds and have had the opportunity to try foods, which originated in other countries. However, the largest quantity of rice purchased in the United States is moderately firm and not sticky.

Being able to measure the quantity of amylose and amylopectin is a very valuable laboratory method considering the importance of those carbohydrates to rice quality. Most methods available today use iodine to measure amylose and amylopectin. When iodine is exposed to amylose a blue color is formed. Iodine with amylopectin produces a purple color. The greater the quantity of either carbohydrate the darker the color. If neither amylose nor amylopectin are present a solution of iodine will remain a yellow color.


 

Purpose of Experiment
The purpose of this experiment is to examine the amylose content of various types of rice and cereal grain fractions. Another purpose is to gain an awareness of the diversity in cereal grain eating and cooking properties, which are controlled by differences in their chemical make-up.


 

Experimental Materials
3/4 c long grain rice
3/4 c sweet rice*
1/4 t corn starch
1/4 t wheat gluten* (protein from wheat --- no starch)
1 bottle of iodine*
1 set of measuring spoons
1 hammer
1 flour sieve
2 thin cotton towels (or strong paper towels)
1 eye dropper
4 teaspoons
2 small zip lock plastic bags
1 marker pen

* Note: Sweet rice can be purchased in Asian or ethnic food stores. Wheat gluten can be found in the baking section of grocery stores. Grocery stores or pharmacies will generally carry iodine.


 

Experimental Method
Part A

  1. Write the following, from left to right, across the top of a 12" wide piece of wax paper: corn starch, long grain rice, sticky rice, wheat gluten.
  2. Grind both types of rice using the following method. Place 1 t of each type of rice on a towel, fold the edges of the towel over the rice, place towel on a hard surface (e.g. linoleum floor) and hammer the rice until at least 1/4 t of course flour is produced. (The rice is fine enough if it can pass through a flour sieve)
  3. Place 1/4 t of each rice flour, corn starch and wheat gluten below their names on the wax paper.
  4. The following steps should be performed as quickly as possible.
  5. Using the eye dropper place 5 to 7 drops of iodine over each sample.
  6. Mix each sample plus iodine into a paste using a different teaspoon for each sample.


 

Record the Results

  1. Examine each of the flours spread on the paper towel.
  2. Write on a piece of paper the color of each paste using the following terms: brown, medium blue, dark bluish or black.


 

Part B

  1. Cook 1/2 cup of both the long grain and the sticky rice according to the directions on the package.
  2. Place 2 or 3 t of each cooked rice in a plastic bag and seal.
  3. Let the rice cool to room temperature.


 

Record the Results

  1. Taste both types of rice.
  2. Feel each type with your fingers.
  3. Write on a piece of paper a description of how the rice felt in your mouth and in your fingers. That is, was it sticky and soft, or not sticky and firm.


 

Conclusions Based on Experimental Results

  1. Based on the results that you recorded which of the four flours has the most amylose and which has the least? Why?
  2. Based on what you have learned about the effect of amylose content on rice properties determine which rice has the most amylose and which has the least.


 

Answers

  1. The corn starch contains the most amylose. It is 100% starch and should be a dark blue to a black color. The wheat gluten contains the least amylose because it contains little to no starch (it should be a reddish brown color similar to what the iodine looked like in its bottle).
  2. Of the rices, the sticky rice has the least amylose but the most amylopectin and should appear as a reddish brown color. The long grain rice should have the most amylose and should be a dark blue to a black color. The sweet rice when cooked should be sticky and soft while the long grain would be harder and not sticky.


 

Discussion
Question: How many foods and beverages can you name which contain rice?

Answer: It is difficult to say how many foods and beverages in the world are made using rice. The reason being that the list is always changing as new products are created by food processing industries, restaurants and in people's homes all around the world everyday.

Some examples of foods which contain rice are as follows: canned chicken and rice soap, rice cakes, puffed rice cereal, Cream of Rice, Kellogg's Rice Krispies and Special K, multi-grain cereals, miso (fermented rice seasoning), kochujang (a fermented soybean and rice paste, which originated in Korea, is used like ketchup, sake (rice wine), pet foods, rice paper/wrappers, rice pilaf, rice milk, baby formulas, rice pudding, rice noodles, unleavened bread, rice bran oil, beer, bounden balls, rice cake (e.g. dosai from India), rice based casseroles, rice snack foods (e.g. kroepeck and lohuwa from the Philippines)and rice vinegar.

 


 

Links to Science for Students

ARS SCI4KIDS

The Knowledge Bank-The Growth Stages of the Rice Plant

Junior Master Gardener

U.S. Rice Producers Assn. site for students and teachers


Last Modified: 11/7/2005
Footer Content Back to Top of Page