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2025
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Determination of Peroxide Value in Sichuan Pepper Sauce by Automated Potentiometric Titration
I. Introduction
Peroxide value is an indicator of the degree of oxidation of oils and fatty acids, used to indicate whether a sample has spoiled due to oxidation. For foods made from oils and fats, peroxide value testing is used to determine their quality and degree of spoilage.
Sichuan pepper sauce contains a large amount of oil, and peroxide value testing is an important indicator for determining its quality.
This method uses excess potassium iodide to react with peroxides in the sample to generate elemental iodine, which is then titrated with sodium thiosulfate to determine the peroxide value of the sample.
II. Instruments and Reagents
2.1 Instruments
JH-T6 fully automatic potentiometric titrator, platinum composite electrode, ultracentrifuge, analytical balance, etc.
2.2 Reagents
Glacial acetic acid-isooctane (3:2) mixed solution, potassium iodide, sodium thiosulfate standard titrant (0.01 mol/L).
III. Experimental Methods
3.1 Sample Preparation
Filter the sample to remove the oil. Collect the filtered oil and centrifuge at 8000-10000 r/min for 15 minutes. Collect the supernatant, add anhydrous sodium sulfate to absorb the water, filter again, and collect for later use.
3.2 Sample Detection
Accurately weigh approximately 5g of the sample and place it in a titration vessel. Add 50mL of a glacial acetic acid-isooctane (3:2) mixture to dissolve the sample and stir thoroughly. Accurately add 0.5mL of saturated potassium iodide solution to the titration vessel. Start the stirrer and react for 60s at a suitable stirring speed. Immediately add 40mL of deionized water to the titration vessel. Insert the electrode and titration head, set the parameters, and titrate to the endpoint using sodium thiosulfate standard titrant (0.01mol/L) on a T960 thermometer with a platinum composite electrode as the working electrode.
The titrator parameters are set as shown in Table 1:
Table 1 Titration Parameter Settings
| Titration mode: | Dynamic titration | minimum addition volume |
0.02mL |
| Electrode equilibrium time: |
4s |
Pre-stirring time: |
60s |
| Electrode equilibrium potential: |
1mv |
Titration rate: | standard |
| Final volume: |
10mL |
Correlation coefficient: |
12.69 |
| Potential jump: |
200 |
Replenishment rate: |
5 |
| Stirring speed: |
7 |
Equilibrium potential before titration: |
10mv |
3.3 Test Spectrum Example
IV. Results and Discussion
4.1 Experimental Results
The peroxide value test results of the Sichuan pepper sauce are shown in Table 2:
Table 2 Peroxide Value Test Results
4.2 Conclusion
The peroxide value of the Sichuan pepper sauce tested was 0.0473 g/100 g. The data repeatability met the standard requirement that the difference between two parallel data should not exceed 10% of the average value, thus meeting the testing requirements.
References
[1] GB 5009.229 National Food Safety Standard - Determination of Peroxide Value in Food [S]
Keyword:
Automated Potentiometric Titration
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