Quality Assessment of oil/fat

Quality Assessment of oil/fat

The following methods are used to assess the quality of dietary fats

1) Peroxide Value (Meq/Kg)

2) Free Fatty Acid %

3) Iodine Value (g/100 g)

4) Anisidine Value

5) Color (OD)

6) β- Carotene(ppm)

GC/Head Space Volatile Analysis

The use of volatiles as indicators of lipid oxidation in foods has been well established.

Many analytical methods used for measurement of volatiles generated during lipid oxidation.

GC/MS remains the dominant techniques

Headspace analysis using GC

      Most biological samples are composed of a wide variety of compounds that differ in molecular weight, polarity, and volatility.

      A headspace sample is normally prepared in a vial containing the sample, the dilution solvent, a matrix modifier, and the headspace

      Volatile components from complex sample mixtures can be extracted from non-volatile sample components and isolated in the headspace or vapor portion of a sample vial.

      An aliquot of the vapor in the headspace is delivered to a GC system for separation of all of the volatile components.

Chemiluminescence (CL)

•         The oxidized  sample emits light in pulses

•         The intensities of these emissions increases by using photo sensitizer (luminol and lucigenin) which  react with oxidizing species

•         oxidation occurs and exited state is attained. On the reverse of exited state emission occurs known as chemiluminescence

•         CL Intensity is directly proportion to amount of free radicals or extent of oxidation

Luminometer

      The photo-oxidized, fried and radiated samples were put in the sample port of Bio-orbit 1250 Luminometery system

      Light emitted (as a result of chemical reaction between the sample and the sensitizer

      The CL response recorded as peak  on the chart recorder

Peroxide Value (POV)

Definition: Measure of  amount of oxygen taken up by 1Kg of fat or oil

 Principal : Liberation of free iodine from KI by oxygen present in sample to be titrated against sodium thiosulphate

Reagents

Acetic Acid - Chloroform solution (3:2)

Mix three parts by volume of glacial acetic acid with two parts of chloroform.

Saturated Potassium iodide Solution

Prepare Saturated Potassium iodide (KI) in freshly boiled water

Standard solution of Na₂S₂O₃  (0.01 N)

       Dissolve 2.48g of Na₂S₂O₃ in 1 lit of distilled  water.

      Starch indicator  solution (0.5%)

        Mix 5g of soluble starch in 1000 ml of boiling water

Procedure

      Take 0.5 - 1 g of oil sample in 250-ml flask

       Add 25 ml of solvent mixture (glacial acetic acid and chloroform, 3:2)

      Shake it well to dissolve the oil

      Add 0.5 ml saturated KI solution  & shake it exactly for 1 min

      Add 25 ml Distt. water to stop the reaction

      Add 0.5 ml of starch indicator the blue colour will appear in flask

      Titrate against 0.01N Na₂ S₂ O₃  till the blue colour disappear& note the reading .