Peroxide Value of Oil and Fat samples

Peroxixe Value :

Peroxide value is a measure of the amount of peroxides in a substance, usually a fat or oil. Peroxides are formed when fats or oils are exposed to air or heat, and they can cause the fat or oil to go rancid. Therefore, measuring the peroxide value is important in determining the freshness and quality of a fat or oil.

Table of Contents

1. Methods of peroxide Value determination
2. Materials and reagents Needed for determination
3. Procedure of peroxide measurement
4. Significance of peroxide Value
5. In Summary

Methods of peroxide Value determination

Peroxide determination refers to the measurement or analysis of peroxides, which are compounds that contain an oxygen-oxygen single bond (O-O) and are often used as disinfectants, bleaching agents, and oxidizing agents in various industrial and chemical processes. There are several methods available for peroxide determination, ranging from colorimetric and titrimetric methods to electrochemical and spectroscopic methods.Commonly used method for peroxide determination is Iodometric Titration.

In this method, peroxides are titrated with a reducing agent, typically iodide ions (I-), which are oxidized to iodine (I2) in the presence of peroxides. The amount of iodine formed is then determined by titration with a standard solution of a reducing agent, such as sodium thiosulfate (Na2S2O3), using a starch indicator. The endpoint is reached when the blue color of the starch-iodine complex disappears, indicating that all the peroxides have reacted.

Materials:

Materials and Reagents

1. Clonical Flask
2. Burette
3. Pipette
4. Burette Stand
5. Fat/oil sample
6. Solvent (e.g. chloroform, acetic acid)
7. Potassium iodide (KI) solution
8. Sodium thiosulfate (Na2S2O3) solution
9. Starch solution
10. Sulfuric acid (H2SO4) solution

Procedure of peroxide measurement

1. Weigh a sample of the fat/oil (usually 1-5 g) into a clean, dry flask.
2. add 2:3 ratio chloroform- acetic acid solution.
3. Add 1 ml 15% KI solution to the flask and swirl to dissolve.
4. Allow the mixture to stand in the dark for 10 minutes at room temperature to allow the peroxides to react with the KI and form iodine.
5. Add 30 ml of distilled water to the flask and titrate the liberated iodine with 0.1 N I Na2S2O3 solution until the solution becomes pale yellow.
6. Add a few drops of starch solution to the flask and continue titration until the blue color disappears.
7. Record the volume of Na2S2O3 solution used for titration.
8. Calculate the peroxide value using the following formula: Peroxide Value = (Volume of Na2S2O3 × 0.1N Na2S2O3 × 1000) / (Weight of Sample in Grams)

where 0.1N Na2S2O3 is the normality of the Na2S2O3 solution, and the result is expressed in meq/kg.

It is important to perform this analysis in a dark environment to prevent light-induced oxidation of the sample. Also, the reagents used in this method are hazardous and should be handled with care.

Significance of peroxide Value

1. It provides valuable information about the degree of oxidative rancidity or deterioration of the oil or fat. High peroxide values indicate that the oil or fat has undergone significant oxidation, which can lead to the formation of off-flavors, odors, and harmful compounds such as free radicals and aldehydes.
2. Used to monitor the stability of oils and fats during storage and processing. By measuring the peroxide value at different time intervals, it is possible to determine the rate of oxidation and predict the shelf life of the product.
3. In the food industry, peroxide value is an important parameter for ensuring the quality and safety of food products. It is commonly used to monitor the quality of edible oils, such as vegetable oils, olive oil, and fish oil. In the cosmetic industry, peroxide value is used to evaluate the stability of oils and fats used in the formulation of cosmetic products.

In Summary

the peroxide value is an important analytical parameter that provides information about the quality and stability of oils and fats. Its measurement is critical in ensuring the safety and efficacy of many products that rely on these substances.