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Determination of Acid Value in Sichuan Pepper Sauce by Fully Automated Potentiometric Titration
I. Introduction
Acid value determination reflects the degree of acidity or rancidity of oil and is one of the basic indicators for detecting whether an oil product is rancid.
Sichuan pepper sauce is a uniquely flavored condiment that enriches people's daily diet and greatly enhances their appetite, making it a popular appetizer. However, Sichuan pepper sauce contains a large amount of oil, and if not consumed promptly, the oil is likely to become rancid, leading to diarrhea and other problems.
This method uses the JH-T6 fully automated potentiometric titration instrument from Shanghai Jiahang to determine the acid value of Sichuan pepper sauce. It exhibits good repeatability and a clear abrupt change, accurately determining the acid value of this oil and providing an accurate basis for oil product testing.
II. Instruments and Reagents
2.1 Instruments
JH-T6 fully automated potentiometric titrator, pH composite electrode, ultracentrifuge, analytical balance, etc.
2.2 Reagents
Ether-isopropanol (1:1) solution, sodium hydroxide (0.1 mol/L) standard solution.
III. Experimental Methods
3.1 Sample Preparation
Filter the oil from the sample using a filter screen. 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 transfer 10g of the oil sample into a titration cup, add 50ml of an ether-isopropanol (1:1) mixture, mix thoroughly, place the sample on the potentiometric titration stage, turn on the stirrer, insert the electrodes and titration head, and after the potential stabilizes, titrate with 0.1mol/L sodium hydroxide standard solution to the endpoint. Record the endpoint titration volume.
The titrator parameters are set as shown in Table 1:
Table 1 Titration Parameter Settings
| Titration mode: | Dynamic titration | minimum addition volume |
0.04mL |
| Electrode equilibrium time: |
8s |
Pre-stirring time: |
10s |
| Electrode equilibrium potential: |
1mv |
Titration rate: | standard |
| Final volume: |
10mL |
Correlation coefficient: |
56.1 |
| Potential jump: |
100 |
Replenishment rate: |
400 |
| Stirring speed: |
6 |
Equilibrium potential before titration: |
6mv |
3.3 Test Spectrum Example
IV. Results and Discussion
4.1 Experimental Results
The acid value test results for Sichuan pepper sauce are shown in Table 2:
Table 2 Acid Value Test Results
4.2 Conclusion
The acid value of the sample tested was 0.8852 mg KOH/g. The results showed good parallelism, and the detection was safe, convenient, rapid, and accurate.
References
[1] GB 5009.227 National Food Safety Standard - Determination of Acid Value in Food [S].
Keyword:
Automated Potentiometric Titration
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