Organic “Breakfast” Food Testing Lab, 2017






     Can organic molecules be found in food? The purpose of this lab is to find and test various types of organic molecules including proteins, lipids, and carbohydrates in common food products. Characteristics of organic molecules will be made evident by using different procedures and stains to identify the macromolecules. The chemistry of living systems is the chemistry of carbon-containing compounds.  Carbon's unique chemical properties allow it to polymerize into chains by dehydration synthesis, forming key biological macromolecules such as: proteins, lipids, carbohydrates and (nucleic acids). Proteins perform the chemistry of the cell.  Proteins are linear polymers of amino acids (monomers). Because the 20 standard amino acids that occur in proteins have side groups with different chemical properties, the function and shape of a protein are critically affected by its particular sequence of amino acids. Proteins are typically characterized as fibrous or globular and have several functions such as: energy, movement, transport, defense, structure, and metabolism. Lipids are not soluble in water.  Fats are one type of water-insoluble molecules called lipids which are polymers made up of fatty acids and glycerol (monomers).  Fats can be saturated, like animal fat or butter or are polyunsaturated like oils. Fats are molecules that contain many more carbon hydrogen bonds than carbohydrates and, thus, provide a more efficient form of long-term energy storage.  Other lipids include phospholipids and steroids.  Fats are used for energy, insulation, metabolism, structure, and transportation. Carbohydrates contain many carbon hydrogen bonds.  Carbohydrates consist of monosaccharides (monomers) or polymers of monosaccharides, and are used principally for energy, which is stored in their carbon-hydrogen bonds.  The most metabolically important carbohydrate is glucose, a six-carbon sugar.  Organisms often transport sugars as disaccharides and therefore, cannot be utilized while they are being transported.  Excess energy resources may be stored in complex sugar polymers called starches (in plants) and glycogen (in animals and fungi) and used for structural material. In summary, carbohydrates can be used as an initial source of energy, structural material, and used to transport energy in the body. The hypothesis is that if proteins, lipids, and carbohydrates are found in basic food produces, then they will be indicated as such using specific stains.





Group:                                                                 Stock Table:             


(4) Test tubes                

(2) Aluminum Dishes

(2) Glass Eye Droppers   

     250 mL Beaker             

     100 mL Beaker        

     Stirring Rod              




Test Tube Clamp

Beaker Tong

Test Tube Rack


Masking Tape




Heat Source

Paper Towels


Water (DD and tap)


Biuret Reagent

Sudan Dye (IV)

Benedict's Solution

Lugol's Solution

Raw Egg

Raw Bacon

Bread (white)

Margarine (not butter)

Jelly (apple)


Unknowns: TBA








Note: dropper full means one squeeze and release of the eye dropper bulb.




1. Carefully break an egg into the dish (don't break yoke) and slowly cook until the egg white is mostly solid white.  Adding heat helps to break molecular bonds and increase surface area; thus, making it easier for the indicators to work. Albumin proteins are found in the egg white.


 2. Carefully retrieve the pan with a test tube holder, extract a white section off the egg (~3x3 cm sq) and place the extraction into a 100 mL beaker.


 3. Add 5 dropper fulls of water to the sample and stir the sample with a stirring rod until it's "soupy". Mixing helps to break molecular bonds and increase surface area.  


 4. Carefully add the "soupy" sample to a test tube.


 5. Add 25 drops of Biuret reagent into the test tube with the egg mixture.  


 6. A color change into purple indicates the presence of protein.


 7. Place 2-3 pieces of pre-cut bacon into the other / new dish and cook the meat until a fair amount of grease appears (try not to burn the bacon).


 8. Save the bacon/fat/grease for later.


* Answer lab report questions at this time followed by cleaning all the materials / glassware.




 1. Place a 5 dropper fulls of water in 2 clean test tubes and add 25 drops of Sudan dye in each.


 2. Heat a small (~3x3 cm sq.) amount of margarine in a 100 mL beaker by carefully holding the beaker with a beaker tong at an angle over a heat source.


 3. With an eye dropper, add 10 drops of liquid margarine into one of the test tubes with the Sudan Dye. Swirl the test tube side to side for a few seconds. 


 4. If necessary, re-heat the bacon grease and using an eye dropper, extract 10 drops of the liquid into the other test tube with the Sudan dye.  Swirl the test tube side to side for a few seconds.


 5. Lipids will be stained redder than the solution and will rise to the top of the water and/or be suspended in small globules after several minutes.  However, the margarine may not separate as well, why do you think this might be happening? (rhetorical question)


* Answer lab report questions at this time followed by cleaning all the materials / glassware.





1. Place a 250 mL beaker of tap water (~1/2 full) onto a burner and warm to a boil.


2. Add a small (~2x2 cm sq.) amount of jelly in a 100 mL beaker. Stir in 2 dropper fulls of “distilled water”.


3. Place 1 dropper full of the jelly liquid into a test tube. 


4. Add 3 drops of Benedict's solution to the jelly solution and shake gently to mix.


5. Place the test tube into the hot water bath and watch the solution in the test tube for about 3 minutes. A light green, yellow, orange, (perhaps red) coloration of the liquids indicates the presence of reducing sugars (sugars breaking into their simplest components (i.e. monosaccharides)) in that order of increasing concentration.


6.  Place a piece of toast into a toaster (do not burn the toast).


7. After toasting the toast, place a small amount (~4 x 4 cm sq.) of the bread in your (or partners) mouth. Chew for 5 minutes but do not swallow the bread. Salivary amylase enzyme, found in your saliva, is used to break the bonds of starch into maltose.


 8. Place the chewed bread in a clean test tube and add 1 dropper full of “distilled water”.


 9. Add 3 drops of Lugol’s solution to the bread solution in the test tube and shake gently to mix. A gray to blue-black to dark purple coloration of the liquid indicates the presence of starch in that order of increasing strength.


* Answer lab report questions at this time followed by cleaning all the materials / glassware.



Testing For an Unknown Substance:


   1. Place a “dropper full” of the Unknown Substance (may be assigned) in “each” of 4 clean test tubes. Label with tape the tubes as A-D. The test tube labels will be for the following:


(A.  lipids, B. proteins, and C. monosaccharides, D. polysaccharides)  


   2. Do the following for each and then compare your results with your previous data:


·         Lipids: Add a “dropper full” of unknown to (A) and then 5 drops of Sudan; observe


·         Proteins: Add a “dropper full” of unknown to (B) and then 5 drops of Biuret; observe


·         Monosaccharides: Add a “dropper full” of unknown to (C) and then 5 drops of Benedict’s; and place in hot water bath and observe (~1 minute)


·         Polysaccharides: Add a “dropper full” of unknown to (D) and then 5 drops of Lugol’s; observe


* Answer lab report questions at this time followed by cleaning all the materials / glassware.