Qulitative test on fats and oils
Title of experiment:
Detection of seasame oil by( BAUDWIN TEST)
Objective:
To detect in a qualitative way the presence of various adulterants in a
samples of fats and oils.
Introduction and principle:
Several qualitative tests are available to detect the presence of added
adulterants in fats and oils.
1) BAUDOUIN TEST:
This test is used to detect the presence of added seasame oil, which is
characterized by the presence of certain phenolic substances. The
principle of the test is based on the reaction of phenols with furfurals in
acid solution. Furfurals are formed by the dehydration of the
monosaccharides in concentrated mineral acids.
Hence a solution of sucrose in concentrated hydrochloric acid will be
hydrolysed to an equimolar mixture of glucose and fructose,both of
which give rise to hydroxymethyl furfural by dehydration. The latter
reacts with the phenols found in seasame oil to give a compound with a
pink colour.
Material and apparatus:
1. ethanol 90% v/v
2. ammonia sol.
3. 1% sucrose sol. concentration hydrochloric acid.
Method:
1- put 5ml of sample in conical flask and add to it 5ml of
ethanol/ammonia mixture (9:1)
2- shake well and heat on a water bath until the sol. Gets free from both
ammonia and ethanol.
3- add 1ml of the acid sucrose mixture, skake and allow the sol. To stand
for 5min.
4- the development of apink colour indicates the presence of seasame oil.
2) B-halphen test:
This test is used to detect in the presence of added cotton seed oil, which
is characterized by the presence of the toxic pigment gossypol. The latter
reacts with giving a reddish colour.
Material:
1-stoppered glass test tubes.
2-water bath.
3-amyl alchhol.
4-precipitated sulpher 1% w/v sol. Dissolved in carbon disulphide.
5-halphen sol. (prepared by mixing equal volume of amyl alchol and
precipitated sulpher )
Methods:
1) put 2-3 ml of the sample in a glass stoppered test tube(20ml capacity)
2) add 3ml of halphen solution and close the tube.
3) immense the tube in boiling water for 30min.
4) development of a red colour indicates the presence of cotton seed oil.
3) Detection of mineral oils:
Edible fats and oils are usually saponifiable , whereas mineral oils are not
. in this test, the ability of the sample to be saponified is determined.
Objectives:
This test is established to detect the presence of mineral oils contaminated with edible
oils.
Material:
1-reflux air condenser.
2-alcocholic potassium hydroxide sol.
Method:
1) place 1ml of the oil in a conical flask and add to it 25ml of alcoholic
potassium hydroxide sol.
2) boil under the reflux contents of the flask about 25ml distilled water
and mix thoroughly , if turbidity appears, the mineral oil is present of
more than 0.5%.
Title of experiment:
4) Rancidity test (kreis kerr)
Objectives:
kreis kerr test is aquaitative test for the presence of aldehydes and ketones
in fats and oils, created by its rancidity.
Introduction and principle:
The term "rancidity" is used to describe the development of bad flavours
and odours in fats and oils. It may result either from hydrolysis of the
triacylglycerol present in fats and oils or from oxidation of the
unsaturated fatty acids present in the triacylglycerols. The former cause
may be detected by an increase in the acid value of the sample .
Autooxidation at fatty acid double bonds occurs by reaction with
molecular oxygen present in the atmosphere, causing the formation of
labile peroxides.
The peroxides formed during autooxidation are unstable and decompose
into free radicals .These initiate chain reactions which lead to eventually
to decomposition of the fatty acid into various low molecular weight
aldehydes and ketones.
Aldehydes and ketones react with phloroglucinol developing a red
colour.
Material:
1) 1% phloroglucinol. In ether solution.
2) concentrated hydrochloric acid.
Method:
1) to 1ml of sample add similar amount of conc. Hydrochloric acid.
2) add 2ml of phloroglucinol solution.
3) a red colour will develop if the oil is rancid.