Tools

Analyze quality and quantity of fats

Procedure

Acrolein test:

  1. Take 1 ml of the lipid sample in a test tube.
  2. Add crystals of potassium hydrogen sulphate.
  3. Heat the solution for a few minutes.
  4. Smell the test tube for the pungent smell.

If glycerol present in the sample, it will give a pungent smell.

If glycerol is absent in a sample, it will not produce a pungent smell.

Sudan IV test:

Method:

  1. Take 1 ml of the lipid sample in a test tube.
  2. Then add 1-2 drops of Sudan IV to the solution.
  3. Observe the tubes for the appearance of red-orange colour in the solution.
  4. Gives red-orange colour to the solution, if the lipid is present otherwise the colour of the solution will remain unchanged.

Baduoin test:

  1. Take 5ml of melted ghee in a test tube.
  2. Add 5ml of concentrated hydrochloric acid and 2-3% of furfural solution in alcohol to it.
  3. Keep it aside for 5 to 10 minutes.
  4. If there is the appearance of rose-red colour then the given ghee contains vanaspati. Rose-red colour is formed due to the presence of sesame oil. Vanaspati ghee contains sesame oil whereas pure desi ghee does not contain sesame oil. So, this test is used to distinguish between desi ghee and vanaspati ghee.

Saponification Value:

Material Required:

  • Oil sample
  • Ethanol
  • 0.1N KOH
  • Phenolphthalein
  • Conical flask
  • Burette
  • Beaker

Procedure:

  1. Weigh 1gm of oil sample and dissolve it in 25ml of ethanol in conical flask.
  2. Prepare 0.1N KOH solution and fill it into the burette.
  3. Add 2 drops of phenolphthalein indicator in oil solution and mix it thoroughly and titrate it against 0.1N KOH.
  4. Appearance of light pink color will be the end point. Take the initial and final reading of burette.
  5. Repeat the experiment for two concordant readings.

Calculate Saponification value by using formula given below:

Saponification value = (Blank titration reading – Test sample reading) × N × 56/ Wt. of sample in gm

Solution: 2.5 M KOH Solution: It can be prepared by dissolving 24.2 g KOH in 100 ml water.

Acid Value:

Material Required:

  • Oil sample
  • Ethanol
  • 0.1N KOH
  • Phenolphthalein
  • Conical flask
  • Burette
  • Beaker

Procedure:

  1. Weigh 1gm of oil sample and dissolve it in 25ml of ethanol in conical flask.
  2. Prepare 0.1N KOH solution and fill it into the burette.
  3. Add 2 drops of phenolphthalein indicator in oil solution and mix it thoroughly and titrate it against 0.1N KOH.
  4. Appearance of light pink color will be the end point. Take the initial and final reading of burette.
  5. Repeat the experiment for two concordant readings.

Calculation:

Acid value = V× N × 56.1/ Wt. of oil (1gm) Where,
V = Volume in mL of standard potassium hydroxide or sodium hydroxide used
N = Normality of the potassium hydroxide solution or Sodium hydroxide solution; and
W = Weight in gm of the sample

Iodine value:

Material Required:

  • Oil sample
  • Distilled H2O
  • 0.1N Sodium thiosulphate
  • Carbon tetrachloride (CCl4)
  • Wij’s Solution (iodine monochloride in glacial acetic acid)
  • KI solution
  • 1% Starch indicator solution
  • Iodine flasks
  • Burette
  • Measuring cylinder

Procedure:

  1. (a) Preparation of Test sample: Weigh approx. 2.7 to 3.0gm of oil sample in iodine flask and dissolve in 25 ml of CCl 4 . Now add 25ml of wij’s solution and mix thoroughly. Kept it in dark for 30 minutes.
    (b) Preparation of Blank sample: Prepare similar to 1(a) (only oil sample will be not be taken).
  2. Take out Test sample and add 20ml of KI solution and 50ml of distilled H 2 O and mix thoroughly. The solution will be dark red brown in colour. Titrate it against 0.1N sodium thiosulphate solution until light yellow colour observed, at this stage add 1ml of starch indicator, a purple colour solution obtained. Continue the titration until the colour of the solution in flask turns colourless. This will be recorded as endpoint.
  3. Similarly, above procedure is repeated for Blank sample and record endpoint value for Blank sample.

Calculate the Iodine value using given formula below:

Iodine Value = 12.69 × (V B - V T ) × N ̸ W s
V B = burette reading for Blank sample
V T = burette reading for Test sample
W s = weight of oil sample