IDENTIFYING MACROMOLECULES IN FOOD LAB Introduction Carbohydrates proteins

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 Benedict’s solution simple carbohydrate blue orange IKI solution complex carbohydrate dark red black Biuret solution protein blue violet, black Sudan IV lipid dark reddishorange

Test for Simple Carbohydrates Benedict’s solution • Benedict's solution is a chemical indicator for simple sugars such as glucose: C 6 H 12 O 6. • 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 1. Add ~15 drops of monosaccharide to test tube labeled Mono. 2. Add ~15 drops of disaccharide to test tube labeled Disac. 3. Add ~15 drops of polysaccharide to test tube labeled Poly. 4. Add ~15 drops of water to the test tube labeled H 2 O 5. Add 10 drops of Benedict solution 6. Place test tube in a hot water bath for 5 min – 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 ~15 drops of monosaccharide to test tube labeled Mono. 2. Add ~15 drops of disaccharide to test tube labeled Disac. 3. Add ~15 drops of polysaccharide to test tube labeled Poly. 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 1 ml 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 ~15 drops of known protein sample to well-tray 2. Add ~15 drops of known nonprotein (any of the other samples in the front of the room) to well-tray 3. Add 10 drops of Biuret solution – Record your results