Automatic Kjeldahl determination of protein content in food

The protein content in food is very uneven, and the content of different foods varies greatly. The determination of protein content is an important evaluation index of the nutritional value of food. Protein is a complex nitrogen-containing organic compound, and the common method for its determination is tedious and time consuming. In recent years, the automatic Kjeldahl nitrogen analyzer has been used. This is currently the most advanced nitrogen determination instrument in China, greatly improving the previous deficiencies, saving time and effort, and the results obtained are accurate and reliable.

Weigh the sample into the digestive tract, add two /KJELTABSCU/3.50 copper catalysis tablets, add about 10ml of concentrated sulfuric acid and shake slowly to wet the sample. Put the digestive tube into the digester that has been preheated to 420e. The sample is digested in a transparent blue-green liquid for about 30-60 minutes. Take out and cool for 15-20 minutes. Put the digestive tube into the automatic Kjeldahl distiller and close the safety gate. Wait for the instrument to automatically distill, titrate, calculate, and print the results.

Six kinds of samples with different protein contents were taken. Each sample was measured in parallel for 6 times. The relative standard deviation (RSD) of the results was less than 2%, indicating that the accuracy of the automatic Kjeldahl nitrogen analyzer was good. Six kinds of samples with different protein contents were taken and the standard addition (ferrous ammonium sulfate) recovery test was performed. The recovery rate of ammonium ferrous sulfate was above 99%, indicating that the accuracy of the automatic Kjeldahl meter was good. The protein contents of the six samples were determined using the automatic Kjeldahl determination instrument and the classical Kjeldahl method. The results showed that there was no significant difference between the two methods for the same sample (t=1.0, P>0.05 ).

The determination of nitrogen content in different samples was carried out by the automatic Kjeldahl nitrogen analyzer. From the measurement results, it can be concluded that the automatic Kjeldahl nitrogen analyzer is simple and quick to operate, saving time and effort and having a high degree of accuracy. Compared with the classical Kjeldahl method, the measured results are more satisfactory, but it is not yet possible to determine whether the volatile base nitrogen in the sample can be determined from the appeal test. Further study is needed.

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