Abstract

The qualitative analysis and determination of type of lipid based on their proper tie and characteristics as a result of their reaction with the different qualitative tests was sucessfully done. The charring of the casein indicates that carbon is present. Moisture or droplets in the test tube indicates that hydrogen and oxygen is present. The bad odor indicates that nitrogen is present. Formation of white precipitate indicates that sulfur is present. Formation of yellow precipitate indicates that phosphorus is present.

Introduction

Proteins are polymers of amino acids. Twenty different types of amino acids occur naturally in proteins. Proteins differ from each other according to the type, number and sequence of amino acids that make up the polypeptide backbone. As a result they have different molecular structures, nutritional attributes and physiochemical properties. Proteins are important constituents of foods for a number of different reasons. They are a major source of energy, as well as containing essential amino-acids, such as lysine, tryptophan, methionine, leucine, isoleucine and valine, which are essential to human health, but which the body cannot synthesize. Proteins are also the major structural components of many natural foods, often determining their overall texture, e.g., tenderness of meat or fish products. Isolated proteins are often used in foods as ingredients because of their unique functional properties, i.e.,their ability to provide desirable appearance, texture or stability. Typically, proteins are used as gelling agents, emulsifiers, foaming agents and thickeners. Many food proteins are enzymes which are capable of enhancing the rate of certain biochemical reactions. These reactions can have either a favorable or detrimental effect on the overall properties of foods. Food analysts are interested in knowing the total concentration, type, molecular structure and functional properties of the proteins in foods

PROCEDUREA. Carbon, Hydrogen, And Oxygen1. Prepped a pinch of casein in a test tube2. Inclined test tube, causing the casein to spread within the bottom of the tube3. Heated gently in a low flame for 2-3 minutes or until change had occurred4. Observed and recorded observationsB. Nitrogen1. Prepped 0.25g of soda lime and a pinch of casein the size of a mongo bean in a mortar.2. Mixed substances within test tube.3. Transferred the mixture to a dry test tube and heated cautiously4. Exposed a piece of red litmus paper over the mouth of the tube5. Observed and recorded observationsC. Sulfur1. Prepped the 1ml portion of the filtrate2. Added dilute HCl until it acidifies3. Heated solution to boiling4. Added several drops of 0.1M BaCL₂ solution till white precipitate appears.5. Observed and recorded observationsD. Phosphorus1. Prepped 5 drops of the second portion of the fusion mixture into a micro test tube

2. Added 2-3 drops of Conc. HNO₃ until the substance is acidic3. Added 3 drops of Ammonium Molybdate solution4. Heated nearly to boiling5. Observed and recorded observations

Result

ELEMENT DESCRIPTION OF RESULT CHEMICAL EQUATIONCarbon, Hydrogen & Oxygen Black precipitate Casein + O2 → C + H2ONitrogen Red to blue lp – basic

There was gasNH3 + OH2 → NH4 + OH

Sulfur White ppt , acidic Ba2+ + SO42- → BaSO4

Phosphorus Yellow ppt , acidic PO43- + 3NH4 + 12MoO4

2- + 24H+ → (NH4)3PO4(MoO3)12 + 12H2O

DiscussionThe presence of carbon, oxygen and hydrogen was tested by heating casein, a protein found

mostly in milk products. The casein was heated for three minutes. While heating, you can see the charring of casein, creating a black precipitate, this means that carbon is present. There was also moisture in the test tube, this means that hydrogen and oxygen is present.

The presence of nitrogen was tested in casein through mixture with soda lime. It was then heated. A red litmus paper was placed on the mouth of the test tube while heating. There was also gas inside the test tube while heating. The red litmus paper turned to blue, this is due to NH3 gas. The bad odor indicates the presence of nitrogen.

Fusion was used to oxidize sulfur to sulfate and phosphorus to phosphate. Casein was mixed with the fusion mixture and was heated in a porcelain crucible. The substance first turned black and then to white. It was dissolved in a hot water and filtered. This was then used in the test for sulfur and phosphorus.

The presence of sulfur was tested by using the filtrate from the fusion method and HCl. It took 17 drops of HCl until it was made acidic. It heated to boiling. BaCl2 was the added. A white precipitate was then formed. This is the BaSO4 or barium sulfate.

The presence of phosphorus was tested by using the filtrate from the fusion method and nitric acid. Nitric acid was added until acidic. After that, ammonium molybdate was added then heated. A yellow precipitate was formed. This is the ammonium phospho-molybdate.

ConclusionThe experiment confirmed that carbon, hydrogen, oxygen, nitrogen, sulfur and phosphorUs is

present in proteins.

Reference1. https://mtfiles.wordpress.com/biochemistry/elementary-composition-of-proteins/ 2. https://mynotesarchive.wordpress.com/2012/02/18/chem-lab-notes/