Determination of moisture content in soybean oil by volumetric method

I. Preface

Soybean oil is an oil extracted by pressing soybeans and is one of the commonly used cooking oils. As one of the commonly used edible oils, the quality of soybean oil directly affects the dietary health of consumers. In response, the state has formulated strict implementation standards to ensure the safety and health of consuming soybean oil. Among them, moisture is an important indicator in the detection requirements, which indicates that the moisture and volatile substances should not exceed 0.2% of the content. The moisture content was determined by the Karl Fischer volumetric method, which has good repeatability and can quickly and accurately measure the moisture content.

Ii. Instruments and Reagents

2.1 Instruments

JH-V5 Karl Fischer moisture titrator, analytical balance, etc

2.2 Reagents

Karl Fischer titrant, methanol - n-hexane (1:2).

Iii. Experimental Methods

3.1 Sample Testing

Through the liquid discharge device of the Karl Fischer moisture titrator, the residual liquid is removed. Then, 40mL of the solvent methanol-n-hexane (1:2) is added to the titration cup, with the solvent covering the electrode. After setting the parameters, the instrument starts the pre-titration. When the instrument is in standby mode, click on the system injection, open the rubber stopper of the feeding port, and select the injection volume according to the volume of titration solution consumed by the sample. Quickly add the sample, immediately cover the rubber stopper, click "Start Measurement", and use Karl Fischer. Titrate the titrant to the endpoint, input the sample weight, and calculate the moisture content of the sample.

The parameters of the titrator are set as shown in Table 1:

Table 1 Titration Parameter Settings

Iv. Results and Discussion

4.1 Experimental Results

The experimental results are as shown in Table 2:

Table 2 Test Results

4.2. Conclusions and Precautions

The JH-V5 Karl Fischer moisture titrator measures the moisture content of soybean oil. The data repeatability is good. The instrument can automatically control the titration process, determine the endpoint and calculate the results, reducing errors caused by human factors. It has the characteristics of being fast and simple. It should be noted that:

The setting of the stirring time should be based on the dissolution state of the sample. If the dissolution is slow, the stirring time should be appropriately extended.

2) The solubility of the sample in the solvent is limited. According to the visual observation, if it is found that the sample cannot dissolve in the solvent, please replace it with a new solvent in time to avoid affecting the test results.

References

[1]GB 5009.3 National Food Safety Standard - Determination of Moisture in Food (Karl Fischer Method) [S]