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Determination method for detecting true protein content by using salting-out method and application of determination method

A method of determination, a technology of true protein, applied in the field of analysis and detection, can solve the problems of lack of operating specifications, poor accuracy and repeatability of measurement results, etc. in the determination of true protein content, and achieve the effect of improving repeatability and accurate measurement results

Active Publication Date: 2021-06-08
QINGDAO AGRI UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0003] The technical problem to be solved by the present invention is to provide a A more detailed and accurate detection method for the detection of true protein content in feed or dairy products using the salting out method

Method used

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  • Determination method for detecting true protein content by using salting-out method and application of determination method
  • Determination method for detecting true protein content by using salting-out method and application of determination method
  • Determination method for detecting true protein content by using salting-out method and application of determination method

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Experimental program
Comparison scheme
Effect test

Embodiment 1

[0036] Embodiment 1 test method and steps

[0037] 1) Accurately weigh about 0.5g of the sample (accurate to 0.0001g) and place it in a 200mL beaker, add 50mL of water, heat to boiling, and put it in a water bath at 80°C for 30 minutes.

[0038] 2) Take out the beaker from the water bath, and immediately add 20 mL of 1.25% sodium hydroxide slowly to the beaker with a pipette, then add 20 mL of 6% copper sulfate solution, stir while adding, and let it stand for 2 hours.

[0039] 3) Filter the test solution after standing still with double-layer qualitative filter paper, wash the precipitate with hot water at 80-90°C for 6 to 7 times, check the filtrate with a few drops of 5% barium chloride solution, until no white barium sulfate precipitate is formed .

[0040] 4) Put the precipitate after filtering and washing together with the filter paper in an oven at 80°C for about 2 hours, then transfer all of it to the digestion tube, first add 15mL of concentrated sulfuric acid, let i...

Embodiment 2

[0042] The influence of embodiment 2 different test conditions on test result

[0043] 1. The influence of the sample size on the determination result (fish meal and bacterial protein are used as test samples).

[0044] Table 1 The influence of sample size on the results

[0045]

[0046] It can be seen from Table 1 that the test results of the two samples with the mass of the sample between 0.5g-2g are all within the allowable relative deviation range, indicating that the weight of the sample weighed between 0.5g-2g has little influence on the test results Big. Considering factors such as the volume of hydrochloric acid consumed by washing, digestion, and titration, it is more appropriate for the sample mass to be 0.5g-1g.

[0047] 2. The influence of the heating method on the measurement results (fish meal, bacterial protein, and standard substance are used as test samples).

[0048] In the sample pretreatment, the sample is kept in a micro state for 30 minutes after b...

Embodiment 3

[0062] Embodiment 3 verification test

[0063] The content of true protein was measured under the condition of artificially adding non-protein nitrogen substances to the standard substance to verify the reliability and feasibility of the method.

[0064] Table 5 Adding adulterant test results

[0065]

[0066] It can be seen from Table 5 that artificially adding non-protein nitrogen substances into the reference materials significantly increases the crude protein content, which is the main means of adulteration by illegal traders. Urea, ammonium sulfate, and melamine are easily soluble in water, so the determination results of their true protein are close to the content of the standard substance, while the content of feather meal is relatively high. The reason is that the finely crushed feather meal is difficult to dissolve in water. Not thorough, but from the perspective of relative deviation, it is within the allowable range. Therefore, this method is suitable for the d...

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Abstract

The invention discloses a determination method for detecting true protein content through a salting-out method. The method comprises the following steps of 1) weighing a sample, placing the sample in a container, adding a proper amount of water, heating to boiling, and then transferring into a water bath at 80 DEG C for 30 minutes; 2) taking out from the water bath, immediately and slowly adding sodium hydroxide, then adding copper sulfate, standing and aging to obtain a test solution; 3) filtering the test solution after standing, and washing the precipitate for several times; 4) fully drying the precipitate and the filter paper, putting the precipitate and the filter paper into a nitrogen determination and elimination tube, firstly adding 15mL of sulfuric acid, standing, slowly heating and pre-digesting, then taking down and cooling, then adding sulfuric acid, anhydrous sodium sulfate and copper sulfate again, heating to 420 DEG C, digesting to be clear, and obtaining a to-be-tested sample; and 5) determining nitrogen of the to-be-detected sample by using a Kjeldahl method to obtain the content of true protein in the sample. According to the method, the result of detecting the true protein content in the feed or a dairy product by using the salting-out method is more accurate, and the repeatability and the stability of the detection result are improved.

Description

technical field [0001] The invention belongs to the field of analysis and detection, and relates to an improved salting-out method for determining the content of true protein in feed or dairy products and its application. Background technique [0002] Protein content is one of the main indicators for evaluating the nutritional value of feed and dairy products, and is a key control factor for the quality of feed and dairy products. At present, crude protein is generally used to judge protein content, and crude protein is usually expressed by the national standard method Kjeldahl The nitrogen determination method is the protein content calculated by measuring the total nitrogen content in feed and dairy products, and the total nitrogen content includes protein nitrogen and non-protein nitrogen. True protein is calculated based on protein nitrogen protein content. The "Chinese Agricultural Standard Compilation Feed Volume" published by China Standard Press in 2001 also mention...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01N21/82G01N21/83G01N1/28
CPCG01N21/82G01N21/83G01N1/28
Inventor 张玉娜王倩文黄小丽孙潇
Owner QINGDAO AGRI UNIV
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