The determination of protein content is an important indicator for evaluating the quality of food. Because nitrogen compounds in foods are dominated by proteins, the determination of protein content in foods is usually based on the determination of total nitrogen, and then multiplied by the protein conversion factor to obtain the protein content. In our country's current national standards, the protein is measured by a protein analyzer, which is digested by the sample to be salted, distilled, absorbed by a boric acid solution, and then determined by standard acid droplets. This method is accurate, concise, and flexible. It is a statutory arbitration measurement method, but it is very skillful, and there are many main and objective influencing factors. It is also difficult to obtain accurate measurement results.
In the process of determining the protein content by a protein analyzer, semi-solids (such as ice cream and fermented bean curd) that are more difficult to symmetry may be weighed on a weighted paper sheet (sample weight ~ total weight of a piece of paper), and the sample After weighing it up, place it on the bottom of the Kjeldahl flask. In order to reduce systematic errors, Blank Kjeldahl flasks were loaded with one piece of paper of the same size at the same time. Different foods contain different amounts of nitrogen. In order to ensure that the volume of acid used for end point titration is within the effective range (5 to 5 ml), the weight of the sample should be determined based on the nitrogen content of the sample. The general content of 5% to 20% should be accurately weighed 1. A 2.09, such as cakes, milk powder, on the content. .1 Write a 1.0% increase in the amount of sample to be measured, preferably 5.0 to 10. Museum is suitable, such as starch, glucose; for high content (protein is greater than 30%), the sample quantity should be reduced, generally 0.2 is accurately weighed. L09 is suitable, such as casein, soy flour.
During the use of the protein analyzer, care must be taken that all reagents are formulated with distilled water that does not contain ammonia. The water in the steam generation bottle is acidic to prevent the free ammonia in the water from being distilled out and the result is high. In short, the protein is measured by a protein analyzer, and the results are affected by many factors. In order to make the measurement result accurate, it should be highly valued at the time of measurement.
In the process of determining the protein content by a protein analyzer, semi-solids (such as ice cream and fermented bean curd) that are more difficult to symmetry may be weighed on a weighted paper sheet (sample weight ~ total weight of a piece of paper), and the sample After weighing it up, place it on the bottom of the Kjeldahl flask. In order to reduce systematic errors, Blank Kjeldahl flasks were loaded with one piece of paper of the same size at the same time. Different foods contain different amounts of nitrogen. In order to ensure that the volume of acid used for end point titration is within the effective range (5 to 5 ml), the weight of the sample should be determined based on the nitrogen content of the sample. The general content of 5% to 20% should be accurately weighed 1. A 2.09, such as cakes, milk powder, on the content. .1 Write a 1.0% increase in the amount of sample to be measured, preferably 5.0 to 10. Museum is suitable, such as starch, glucose; for high content (protein is greater than 30%), the sample quantity should be reduced, generally 0.2 is accurately weighed. L09 is suitable, such as casein, soy flour.
During the use of the protein analyzer, care must be taken that all reagents are formulated with distilled water that does not contain ammonia. The water in the steam generation bottle is acidic to prevent the free ammonia in the water from being distilled out and the result is high. In short, the protein is measured by a protein analyzer, and the results are affected by many factors. In order to make the measurement result accurate, it should be highly valued at the time of measurement.
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