TEST FOR FORMALIN IN MILK
AIM:
To detect formalin (formaldehyde) in milk.
APPARATUS:
Test tube, ice bath.
REAGENT:
Sulfuric acid, ferric chloride.
PRINCIPLE:
Formalin reacts with ferric chloride and acid to give a violet ring.
PROCEDURE:
Take 5ml milk in a test tube.
Add 5ml sulfuric acid with FeCl₃ carefully along the wall.
Observe for a violet ring at the interface.
RESULT:
Presence of violet ring indicates formalin.
TEST FOR PRESENCE OF UREA IN MILK
AIM:
To detect adulteration of milk with urea.
APPARATUS:
Test tubes, dropper.
REAGENT:
Para-dimethylaminobenzaldehyde (PDAB) reagent.
PRINCIPLE:
Urea reacts with PDAB to form a yellow color.
PROCEDURE:
Add 5ml milk sample in a test tube.
Add 2ml of PDAB reagent.
Observe for yellow color development.
RESULT:
Yellow color indicates presence of urea.
DETERMINATION OF PHOSPHATE IN FOOD (VANADOMOLYBDATE METHOD)
AIM:
To determine phosphate content in a food sample.
APPARATUS:
Test tubes, colorimeter.
REAGENT:
Ammonium molybdate, ammonium vanadate, nitric acid.
PRINCIPLE:
Phosphate reacts with vanadomolybdate reagent to form a yellow complex.
PROCEDURE:
Prepare sample extract.
Add reagent and incubate for 10 minutes.
Measure absorbance at 400–420 nm.
CALCULATION:
Compare with phosphate standard curve.
DETERMINATION OF VITAMIN A (COLORIMETRIC METHOD)
AIM:
To determine the vitamin A content in margarine or food sample.
APPARATUS:
Test tubes, colorimeter, pipettes.
REAGENT:
Chloroform, antimony trichloride reagent (Carr-Price reagent).
PRINCIPLE:
Vitamin A reacts with antimony trichloride to form a blue complex, measurable colorimetrically.
PROCEDURE:
Extract sample with chloroform.
Add 2ml of Carr-Price reagent.
Measure absorbance at 620 nm.
Compare with vitamin A standard.
CALCULATION:
Use standard calibration curve to estimate µg vitamin A.
DETERMINATION OF SUGAR IN HONEY (FEHLING’S TEST)
AIM:
To detect reducing sugars in honey.
APPARATUS:
Test tubes, burette, water bath.
REAGENT:
Fehling’s A and B solutions.
PRINCIPLE:
Reducing sugars reduce Cu²⁺ to Cu₂O (red precipitate).
PROCEDURE:
Mix equal volumes of Fehling A and B.
Add honey solution gradually while boiling.
Observe brick-red precipitate.
CALCULATION:
Compare against known glucose standards.
Tollen’s Reagent
Purpose: Detects aldehydes (reducing agents).
Procedure:
Prepare fresh before use:
Mix 2 ml of 0.1 M silver nitrate solution.
Add a few drops of dilute NaOH to form Ag₂O precipitate.
Add dilute ammonia dropwise until the precipitate just dissolves.
