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.
The presence of these
macromolecules can be
detected by chemical indicators
Introduction
In 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.
Objective
Identify the presence of major nutrients such
as simple carbohydrates (glucose),
complex carbohydrates (starch), protein
and fat in common foods.
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
Lugol’s
solution
complex
carbohydrate
dark red
black
Biuret
solution
protein
blue
violet,
black
Sudan III
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.
 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
1. Add 2ml of food sample to test
tube
2. Add 8 drops of Benedict solution
3. Place test tube in a hot
water bath for 10 minutes.
Test for Complex Carbohydrates
IKI solution (Lugol’s 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.
Test for Complex Carbohydrates
IKI solution
• IKI solution  (Iodine Potassium Iodine) color
change = blue to black
Procedure
Complex carbohydrate
1. Add 2ml of food sample to test
tube
2. Add 8 drops of Lugols solution
Test for Protein (amino acids)
Biuret solution
• Biuret solution  dark violet blue to
pinkish purple is positive for protein
Procedure
Protein (amino acids)
1. Add 2ml of food sample to test
tube
2. Add 8 drops of Biuret solution
Test for Fats (lipids)
Sudan III
• Like lipids, the chemical Sudan
III is not soluble in water; it is,
however, soluble in lipids.
• In this test dark red Sudan III is
added to a solution along with
ethanol to dissolve any possible
lipids.
Test for Fats (lipids)
Sudan III
• If lipids are present the Sudan III will stain them
reddish-orange (positive test).
Procedure
Fats (lipids)
•
•
Add 2ml of food sample to test
tube, then 2 ml of distilled water.
Add 10 drops of Sudan IV *do not
shake!!
LAB SAFETY and CLEAN UP
WEAR safety
goggles and
apron at all times
NO EDIBLE
products
in lab
THOROUGHLY
CLEAN lab area
and equipment
Murder and a Meal
Conclusion
• Report your findings in discussion format. Open the
discussion with a statement regarding which
restaurant the victim visited for his last meal (1 point).
Provide a logical explanation, using data from the tests
on the stomach contents, that explains how you
reached that conclusion (4 points).
• The discussion should explain the results of the
investigation in regard to the scientific concepts
• that are being applied in the investigation. In this case,
the scientific concept being applied are
macromolecules and the specific chemical tests used
to determine their presence (5 points)
Simple Carbohydrate
1.
2.
3.
Add 2ml of food sample to test tube
Add 8 drops of Benedict solution
Place test tube in a hot water bath for 10 minutes.
Complex Carbohydrate
1.
2.
Add 2ml of food sample to test tube
Add 8 drops of Lugols solution
Protein (amino acids)
1.
2.
Add 2ml of food sample to test tube
Add 8 drops of Biuret solution
Fats (lipids)
1. Add 2ml of food sample to test tube, then 2 ml of distilled water.
2. Add 10 drops of Sudan IV *do not shake!!