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.
DETERMINATION OF PROTEIN (KJELDAHL METHOD)
AIM:
To determine total protein content in a sample.
APPARATUS:
Digestion flask, distillation unit, titration setup.
REAGENT:
Concentrated H₂SO₄, NaOH, boric acid, indicator.
PRINCIPLE:
Nitrogen is converted to ammonia, distilled, and titrated to estimate protein.
PROCEDURE:
Digest sample with H₂SO₄ + catalyst.
Neutralize, distill ammonia into boric acid.
Titrate with HCl.
CALCULATION:
% Protein = Titre × 1.4 × 6.25 / Sample weight
Seliwanoff’s Reagent
Purpose: Differentiates between aldose and ketose sugars.
Procedure:
Dissolve 0.05 g resorcinol in 100 ml of 3M HCl.
Store in an amber bottle.
DETERMINATION OF ALCOHOL IN WINE (DISTILLATION + DENSITY)
AIM:
To measure ethanol content in wine.
APPARATUS:
Distillation setup, pycnometer or alcohol hydrometer.
REAGENT:
None.
PRINCIPLE:
Ethanol is distilled and measured based on density.
PROCEDURE:
Distill 100ml of wine.
Collect distillate and measure density at 20°C.
Refer to alcohol tables.
CALCULATION:
% Alcohol = Based on density from standard chart.
Biuret Reagent
Purpose: Detects proteins (peptide bonds).
Procedure:
Dissolve 1.5 g CuSO₄·5H₂O in 500 ml distilled water.
Add 6 g sodium potassium tartrate and 375 ml of 10% NaOH.
Make up to 1000 ml with distilled water.
