Republic of the Philippines
CENTRAL BICOL STATE UNIVERSITY OF AGRICULTURE
San Jose, Pili, Camarines Sur 4418
Website: www.cbsua.edu.ph
Email Address: op@cbsua.edu.ph
Trunkline: (054) 871-5531-33 local 101
COLLEGE OF ARTS AND SCIENCES
Name: ___________________________________
Date: _________________
Course, Year & Section: _____________________
Rating: _______________
Laboratory Activity #1
TEST FOR PRESENCE OF STARCH
As you have learned during the discussion, starch is the major form of stored
carbohydrate for plants. It is composed of thousands of units of monomer–glucose, in
the forms of amylose and amylopectin. In this activity, we will test several food samples
for the presence of starch by using an iodine solution.
Samples containing starch turn blue-black in color when a few drops of
iodine solution are placed. This is due to the formation of polyiodide chains from the
reaction of starch (amylose) and iodine. The amylose in starch forms helices where
iodine molecules assemble, forming a dark blue or black color.
Warning
Be careful in handling iodine! It can stain clothing, equipment, and skin. DO
NOT put iodine in your mouth and DO NOT eat any tested foods, as iodine can be
poisonous. Wash your hands and clean your stations when done.
Materials
 10 different food samples
o Starchy (cornstarch, cassava starch, potato, ube, pasta, bread)
o Non-starchy (milk, apple, cucumber, soft drinks, table sugar)
 Iodine solution
Any of the following:
o Betadine (povidone-iodine mixture)
o Lugol’s solution (iodine-potassium mixture)
o Tincture of iodine (iodine is dissolved in alcohol, or alcohol and water)
 Watch glass/spot plate/disposable plastic cups or containers
 Medicine dropper
 Mortar and pestle, knife
Procedure
1. Prepare the food samples to be tested and place each sample in a container.
2. Using the medicine dropper, add 2-3 drops of iodine solution to each sample.
Page 1 of 3
3. Observe any change in color.
Observations/Guide Questions
Complete the table below using the food your group has compiled. When drops of
iodine solution are applied to food containing starch, the solution will turn dark blue,
purple, or blackish.
Food Sample
Description
before testing
Description after
testing
Conclusion: Is
starch present?
1.
2.
3.
4.
5.
6.
7.
Page 2 of 3
8.
9.
10.
What principle is involved in the iodine test for starch? How will you explain the
reason for the change in color of food samples?
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
_____________
Conclusion/Generalization
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
_____________
Page 3 of 3