Download shroff srrotary institute of chemical technology

SHROFF S.R.ROTARY
INSTITUTE OF CHEMICAL
TECHNOLOGY
Subject :- OCUP
Topic :- Tests Of Protein
 Prepared By:1. Gaurav Jadav (130990105008)
2. Sidhdharth Parmar (130990105022)
Guided By:Dr. Anjali Bishnoi
Content
Importance of Proteins
Determination of the Protein Content of Foods
Color Tests of Proteins
References
Importance of Proteins
 Proteins are indispensable components of all living things,
including the simplest forms of life, such as bacteria, algae,
and other micro-organisms.
 They are required in the diets of all animals, including human,
to synthesize tissues, enzymes certain harmones, and some
blood components.
 In addition, they are used in the maintenance and repair of
existing tissues and as source of energy for the body.
Determination of the Protein
Content of Foods
 The analysis of protein content of foods is based on its
nitrogen content. Since the average nitrogen content of
protein is 16 per cent, the protein content of a substance can
be obtained by multiplying its nitrogen value by a factor
100/16=6.25.
 For example, if a certain food contains 2 per cent nitrogen, on
analysis its protein content would be 2x6.25=12.5 per cent.
 The total nitrogen content of proteins and peptides may be
determined by the Dumas method or Kjeldahl method.
Color Tests of Proteins
 Proteins give a number of color reactions which serve as their
test. In fact, these reactions are due to the presence of certain
specific groups in the protein structure.
 Therefore, a given protein may not respond to all the general
tests listed below.
1. Xanthoproteic Test : When a protein is warmed with conc.
is produced .
, a yellow color
 This test is given by a protein that consists of amino acids
containing a benzene ring, such as tyrosine and tryptophan.
The aromatic rings undergo nitration to give yellow products.
Tyrosine
2. Biuret Test : A small amount of NaOH solution is added to the protein.
After mixing the two reagents, copper sulfate solution is
added. Violet color is produced.
Protein + NaOH + Copper sulfate = Violet Color
 This test is given by all proteins that contain two or more
peptide linkages.
3. Ninhydrin Test : When proteins are boiled with a dilute aqueous solution of
ninhydrin, a violet color is produced.
Protein + Ninhydrin = Violet Color
 This test is given by α-amino acids, proteins and dipeptides.
Glycine
Ninhydrin
4. Millon’s Test : The Millon’s reagent consists of mercury dissolved in nitric
acid (forming a mixture of mercuric and mercurous nitrates
and nitrites).
 When Millon’s reagent is added to a protein, a white
precipitate is formed.
Protein + Millon’s Reagent = White Precipitate
 This test is given by protein which yield tyrosine on hydrolysis.
5. Hopkins-Cole Test : Concentrated sulfuric acid is added down the side of a testtube containing a solution of protein and glyoxalic acid, to
form a layer. A violet ring appears between the two layers.
 This test is given by proteins which have the amino acid
tryptophan in its structure.
Violet Ring formed
Glyoxalic acid
Protein
References
Organic Chemistry (Bahl & Bahl)
www.google.com