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 INDICATORMACRO- MOLECULE NEGATIVE TEST POSITIVE TEST Benedict’s solution simple carbohydrate blueorange IKI solutioncomplex carbohydrate dark redblack Biuret solution proteinblueviolet, black Sudan IVlipiddark redreddish- orange

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 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 Benedict solution 5.Place test tube in a hot water bath for 5 minutes. –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