Download IDENTIFYING MACROMOLECULES IN FOOD LAB

IDENTIFYING
MACROMOLECULES
IN FOOD
LAB
Introduction
Carbohydrates,
proteins, and fats are
all essential nutrients.
We cannot manufacture
these nutrients so we
must obtain them
from our environment.
Introduction
• In this lab, with the use of
indicators as chemical detection
tools, you will analyze a variety of
foods for the presence of nutrients.
• Detection is based upon observing
a chemical change that takes place
most often a change in color.
What is an indicator?
• Indicators are chemical compounds used
to detect the presence of other
compounds.
Background Information
INDICATOR
MACROMOLECULE
NEGATIVE POSITIVE
TEST
TEST
Benedict’s
solution
simple
carbohydrate
blue
orange
IKI solution
complex
carbohydrate
dark red
black
Biuret
solution
protein
blue
violet,
black
Sudan IV
lipid
dark red
reddishorange
Test for Simple Carbohydrates
Benedict’s solution
• Benedict's solution is a chemical indicator for
simple sugars such as glucose: C6H12O6.
• Aqua blue: negative test;
• Yellow green/brick red, etc.: positive test
Test for Simple Carbohydrates
Benedict’s solution
• Unlike some other indicators, Benedict’s
solution does not work at room
temperature - it must be heated first.
Procedure
Simple carbohydrate
Add 1ml of monosaccharide to test
tube #1
Add 1 ml of disaccharide to test
tube #2
Add 1 ml of polysaccharide to test
tube #3
Add 10 drops of Benedict solution
Place test tube in a hot
water bath for 5 minutes.
1.
2.
3.
4.
5.
–
Record your results
Test for Complex Carbohydrates
Lugol’s solution
• IKI solution  (Iodine Potassium Iodine) color
change = blue to black
Test for Complex Carbohydrates
Lugol’s Iodine Solution
• Iodine solution is an indicator for a molecule
called starch.
• Starch is a huge molecule made up of hundreds
of simple sugar molecules (such as glucose)
connected to each other.
Procedure
Complex carbohydrate
1. Add 1ml of monosaccharide to test
tube #1
2. Add 1 ml of disaccharide to test
tube #2
3. Add 1 ml of polysaccharide to test
tube #3
4. Add 10 drops of IKI solution to
each test tube
–
Record your results
Test for Fats (lipids)
Sudan IV
• Like lipids, the chemical Sudan
IV is not soluble in water; it is,
however, soluble in lipids.
• In this test dark red Sudan IV is
added to a solution along with
ethanol to dissolve any possible
lipids.
• If lipids are present the Sudan IV
will stain them reddish-orange
(positive test).
Test for Fats (lipids)
Sudan IV
• If lipids are present the Sudan IV will stain them
reddish-orange (positive test).
Procedure
Fats (lipids)
•
Add 1ml of food sample
to tray
Add 10 drops of Sudan
IV
•
–
•
Record your results
Using a Q-Tip smear a
sample of the lipid onto a
square of brown paper.
–
Record your results
Test for Protein (amino acids)
Biuret solution
• Biuret solution  dark violet blue to
pinkish purple
Procedure
Protein (amino acids)
1. Add 1ml known protein sample to
well-tray
2. Add 1 ml of known non-protein
(any of the other samples in the
front of the room) to well-tray
3. Add 10 drops of Biuret solution
–
Record your results