Detection method of volatile basic nitrogen

Abstract

The invention relates to the technical field of chemical detection, in particular to a detection method of volatile basic nitrogen. According to the method, the capsule filled with magnesium oxide is placed in the distillation tube of the automatic Kjeldahl apparatus for distillation, and compared with the existing method that magnesium oxide is directly placed in the distillation tube, the obtained result is more accurate. The method disclosed by the invention is high in detection accuracy, small in error, simple and convenient to operate, safe, efficient and relatively low in cost. The method disclosed by the invention is suitable for detecting the freshness of products such as food, feed, fermented and enzymolyzed products and the like.

Description

Technical Field

[0001] The invention relates to the technical field of chemical detection, and in particular to a method for detecting volatile basic nitrogen. Background Art

[0002] Volatile basic nitrogen is the general term for alkaline nitrogen-containing substances such as ammonia and amines produced by protein decomposition when food and feed become corrupt under the action of enzymes and bacteria. It is the main indicator for judging the freshness of food and feed. In recent years, with the improvement of people's living standards, people have paid more and more attention to food safety. The freshness of meat and aquatic products is related to food safety, and the volatile basic nitrogen testing business for detecting their freshness has surged. At the same time, with the rise in feed prices, many farms feed animals partially fermented and enzymatic feeds in order to reduce feeding costs. These feeds also need to be tested for volatile basic nitrogen to control feed quality. Therefore, there is a huge market demand for fast, accurate, low-cost, and easy-to-operate volatile basic nitrogen detection methods and related products.

[0003] At present, the standard for testing volatile basic nitrogen in animal feed is GBT32141-2015 "Determination of Volatile Basic Nitrogen in Feed", and the standard for testing volatile basic nitrogen in food is GB5009.228-2016 "National Food Safety Standard Determination of Volatile Basic Nitrogen in Food". Both standards have some problems and room for improvement. For example, in GBT32141-2015 "Determination of Volatile Basic Nitrogen in Feed", perchloric acid solution is used for sample extraction, and perchloric acid solution is highly corrosive and irritating, and its use is highly dangerous. In addition, in this standard, 10ml of perchloric acid extract is drawn and placed in a digestion tube, and 10ml of 40g / L sodium hydroxide solution is added to the digestion tube for distillation. The pH of 40g / L sodium hydroxide solution is about 12, and the perchloric acid extract is acidic. After the two are neutralized, the solution becomes weakly alkaline, which basically meets the detection conditions of volatile basic nitrogen. However, due to the different physical and chemical properties of the test samples and the different weighed masses, the pH value of the extract after the samples were extracted with perchloric acid solution is uncertain, and the consistency of the pH in the distillation tube after adding sodium hydroxide solution to each sample cannot be guaranteed. In the automatic Kjeldahl nitrogen analyzer method of GB5009.228-2016 "National Food Safety Standard Determination of Volatile Basic Nitrogen in Food", after adding 1g of magnesium oxide to the distillation tube, it must be connected to the distiller immediately. During this process, if the action is not fast enough, part of the gas produced by the reaction will escape into the air, which will cause large human operation errors; at the same time, when the number of samples to be tested is large, the weighing of magnesium oxide is cumbersome and not conducive to rapid determination.

[0004] Therefore, there is still an urgent need for a method for detecting volatile basic nitrogen that is fast, accurate, and easy to operate. Summary of the invention

[0005] In view of the above problems, the main purpose of the present invention is to provide a method for detecting volatile basic nitrogen. The method of the present invention has high detection accuracy, is easy to operate, and improves detection efficiency.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] The present invention provides a method for detecting volatile basic nitrogen, which comprises the following steps:

[0008] Sample processing;

[0009] Reagent preparation: including the preparation of hydrochloric acid standard titration solution or sulfuric acid standard titration solution;

[0010] Preparation of magnesium oxide capsules: adding magnesium oxide to hollow capsules to obtain magnesium oxide capsules;

[0011] The determination is performed using an automatic Kjeldahl nitrogen analyzer. When performing a reagent blank determination and a determination of a sample to be tested, the magnesium oxide capsule is respectively added into a distillation tube of the automatic Kjeldahl nitrogen analyzer for distillation.

[0012] Preferably, the hollow capsule is an animal-derived hollow capsule.

[0013] When using the automatic Kjeldahl nitrogen analyzer to test volatile basic nitrogen, it was unexpectedly discovered that wrapping magnesium oxide in hollow capsules and then adding them to a distillation tube for testing had significantly better data repeatability (parallelism) than directly adding magnesium oxide to the distillation tube.

[0014] Preferably, the amount of magnesium oxide used when measuring the sample to be tested is 0.04-1.00 g. The size of the hollow capsule includes size 00, size 0, size 1, size 2, size 3 and size 4. In practical applications, the specific size of the hollow capsule and the number of capsules used can be selected according to the amount of magnesium oxide used.

[0015] Preferably, the magnesium oxide used is selected from light magnesium oxide, ordinary magnesium oxide or heavy magnesium oxide, preferably light magnesium oxide.

[0016] Preferably, the sample includes food, feed raw materials, fermentation broth and enzymatic hydrolysate; the processing method for feed raw materials, fermentation broth and enzymatic hydrolysate includes: mixing and leaching the sample with trichloroacetic acid solution to obtain a sample solution; taking the sample solution for centrifugation or filtration, taking the supernatant or filtrate to obtain the sample to be tested. The sample processing method of the food refers to the sample processing method in the automatic Kjeldahl nitrogen analyzer method of GB5009.228-2016 "National Food Safety Standard Determination of Volatile Basic Nitrogen in Food".

[0017] Preferably, when measuring the sample to be tested, when light magnesium oxide is selected, the amount of light magnesium oxide is ≥0.04g, and the distillation time is ≥90s; when ordinary magnesium oxide is selected, the amount of ordinary magnesium oxide is ≥0.15g, and the distillation time is ≥120s; when heavy magnesium oxide is selected, the amount of heavy magnesium oxide is ≥0.15g, and the distillation time is ≥120s.

[0018] Preferably, after the sample is extracted with trichloroacetic acid solution, it is measured using an automatic Kjeldahl nitrogen analyzer, the amount of water and alkali added to the automatic Kjeldahl nitrogen analyzer is set to 0 ml, when performing a reagent blank measurement, a trichloroacetic acid solution and a magnesium oxide capsule of an equal volume to the sample are added to the distillation tube, and when performing a measurement of the sample to be tested, the sample and the magnesium oxide capsule are added to the distillation tube.

[0019] Preferably, when the volatile basic nitrogen content in the sample to be tested is ≤20 mg / 100 g, the concentration of the standard hydrochloric acid titration solution or the standard sulfuric acid titration solution used is 0.010-0.015 mol / L; when the volatile basic nitrogen content in the sample to be tested is 20-80 mg / 100 g, the concentration of the standard hydrochloric acid titration solution or the standard sulfuric acid titration solution used is 0.01-0.05 mol / L; when the volatile basic nitrogen content in the sample to be tested is ≥80 mg / 100 g, the concentration of the standard hydrochloric acid titration solution or the standard sulfuric acid titration solution used is 0.10-0.15 mol / L.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] Compared with the existing method for detecting volatile basic nitrogen based on the Kjeldahl method, the detection method of the present invention has higher detection accuracy and smaller error.

[0022] GB5009.228-2016 "National Food Safety Standard Determination of Volatile Basic Nitrogen in Food" stipulates that the amount of magnesium oxide used in the automatic Kjeldahl nitrogen analyzer method is 1g. However, the present invention found in actual testing that the addition of 1g of magnesium oxide is seriously excessive. The present invention found through experiments that adding 0.04g of magnesium oxide can meet the needs of the experiment. In addition, by comparing the dosage and titration time of light magnesium oxide, ordinary magnesium oxide and heavy magnesium oxide, the present invention found that the dosage of light magnesium oxide is less and the reaction speed is faster. Therefore, the selection of light magnesium oxide can save the dosage and time of drugs on the one hand; on the other hand, under the condition of the same dosage, the use of light magnesium oxide can better ensure that the entire reaction is an alkaline environment, thereby ensuring the accuracy of the test results.

[0023] The present invention also optimizes the concentration of the hydrochloric acid standard titration solution or the sulfuric acid standard titration solution. According to the volatile basic nitrogen concentration content in the sample, the concentration range of the hydrochloric acid standard titration solution or the sulfuric acid standard titration solution used is determined. Within the concentration range, the volume of the hydrochloric acid or sulfuric acid consumed is convenient for accurate measurement, thereby solving the problem of result parallelism caused by too small a volume of the hydrochloric acid or sulfuric acid titration.

[0024] The method of the present invention is simple to operate, safe, efficient, low in cost, and widely applicable, and is suitable for detecting the freshness of products such as food, feed, fermentation and enzymolysis. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The graph of the amount of magnesium oxide added (g) and the consumption of hydrochloric acid (ml) for the three types of magnesium oxide described in Experimental Example 1 of the present invention is as follows: A is light magnesium oxide, B is ordinary magnesium oxide, and C is heavy magnesium oxide;

[0026] Figure 2 This is a graph showing the hydrochloric acid consumption (ml) of the three types of magnesium oxide at different distillation times (s) described in Experimental Example 1 of the present invention: A is light magnesium oxide, B is ordinary magnesium oxide, and C is heavy magnesium oxide;

[0027] Figure 3 A scatter plot is made for the mean plus standard deviation of each group of data described in Test Example 2 of the present invention: A blank hydrochloric acid consumption, B sample hydrochloric acid consumption, C volatile basic nitrogen content;

[0028] Figure 4 A scatter plot is made for the mean plus standard deviation of each group of data described in Test Example 3 of the present invention: A blank hydrochloric acid consumption, B sample hydrochloric acid consumption, C volatile basic nitrogen content. DETAILED DESCRIPTION

[0029] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0030] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations and / or combinations thereof.

[0031] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below in conjunction with specific embodiments.

[0032] Example 1

[0033] A method for detecting volatile basic nitrogen, the method comprising the following steps:

[0034] (1) Sample processing

[0035] The processing method for feed raw materials, fermentation broth and enzymatic hydrolysate includes: mixing and leaching the sample with trichloroacetic acid solution to obtain a sample solution; centrifuging the sample solution and taking the supernatant to obtain the sample to be tested; or filtering the sample solution with filter paper and using the filtrate as the test sample. The working concentration of the trichloroacetic acid solution is 20g / L.

[0036] The food sample processing method refers to the sample processing method in the automatic Kjeldahl nitrogen analyzer method in GB5009.228-2016 "National Food Safety Standard Determination of Volatile Basic Nitrogen in Food".

[0037] (2) Reagent preparation:

[0038] Preparation of hydrochloric acid standard titration solution or sulfuric acid standard titration solution: when the volatile basic nitrogen content in the sample to be tested is ≤20mg / 100g, the concentration of the hydrochloric acid standard titration solution or sulfuric acid standard titration solution used is 0.01-0.015mol / L; when the volatile basic nitrogen content in the sample to be tested is 20-80mg / 100g, the concentration of the hydrochloric acid standard titration solution or sulfuric acid standard titration solution used is 0.01-0.05mol / L; when the volatile basic nitrogen content in the sample to be tested is ≥80mg / 100g, the concentration of the hydrochloric acid standard titration solution or sulfuric acid standard titration solution used is 0.10-0.15mol / L.

[0039] Preparation of magnesium oxide capsules: 0.10 g of light magnesium oxide is loaded into one or more hollow gelatin capsules to obtain magnesium oxide capsules.

[0040] The preparation of other reagents is the same as that used in the automatic Kjeldahl nitrogen analyzer method in GB5009.228-2016 "National Food Safety Standard Determination of Volatile Basic Nitrogen in Food".

[0041] (3) Determination using an automatic Kjeldahl nitrogen analyzer:

[0042] Instrument settings: Automatic Kjeldahl nitrogen analyzer with automatic reagent addition and automatic waste discharge function, turn off the automatic waste discharge, automatic alkali addition and automatic water addition functions, set the alkali and water addition volume to 0mL, and set the distillation time to 180s. Kjeldahl nitrogen analyzer without automatic reagent addition and automatic waste discharge function, set the alkali and water addition volume to 0mL, and set the distillation time to 180s.

[0043] Reagent blank determination: If water extraction is used when processing samples or liquid samples are directly used on the machine, add 10ml of water to the distillation tube; if trichloroacetic acid is used to extract samples, add 10ml of trichloroacetic acid solution to the distillation tube. Then add 1 magnesium oxide capsule to the distillation tube, connect it to the distiller and start distillation using the set program. After distillation, record the volume of hydrochloric acid standard titration solution consumed. This volume is counted as V2 in ml; in addition, multiple parallels can be made, and the average of the parallels is recorded as V2.

[0044] Sample determination: add the sample to the distillation tube, add 1 magnesium oxide capsule, connect to the distiller and start distillation using the set program. After the distillation is completed, record the volume of the hydrochloric acid standard titration solution consumed. This volume is measured as V1 in ml. If the accuracy requirement is high, multiple parallel tests can be performed.

[0045] After the determination is completed, clean and clear the liquid adding pipeline and distillation system in time.

[0046] Result calculation

[0047]

[0048] For the meaning of symbols in the formula, see GB5009.228-2016 "National Food Safety Standard Determination of Volatile Basic Nitrogen in Food".

[0049] Example 2

[0050] The difference from Example 1 is that 0.15 g of heavy magnesium oxide is packed into hollow gelatin capsules, and the rest is the same as Example 1.

[0051] Example 3

[0052] The difference from Example 1 is that 0.50 g of ordinary magnesium oxide is packed into hollow gelatin capsules, and the rest is the same as Example 1.

[0053] Example 4

[0054] The difference from Example 1 is that 1.00 g of light magnesium oxide is packed into hollow gelatin capsules, and the rest is the same as Example 1.

[0055] Test Example 1

[0056] In this experiment, light magnesium oxide, magnesium oxide and heavy magnesium oxide were used in the detection of volatile basic nitrogen. Different distillation times and different addition amounts of magnesium oxide were used to find the optimal distillation time and optimal addition amount of the three types of magnesium oxide.

[0057] Silkworm pupa powder is one of the samples with the highest protein content in food and feed raw materials. It is typical to use it as an experimental object to determine the dosage of each magnesium oxide.

[0058] 1. Sample Processing

[0059] Weigh 100 g of silkworm pupa powder into a stoppered conical flask, accurately add 1000 ml of 20 g / L trichloroacetic acid solution, cover the stopper and shake for 30 minutes, filter with filter paper, and the filtrate is the sample to be tested.

[0060] 2. Experimental Methods

[0061] 2.1 Experimental design

[0062] To simplify the test process, this experiment only records the sample titration volume. When the titration volume of a sample decreases significantly, it means that the sample has not reacted fully, which can be judged as insufficient distillation time or insufficient magnesium oxide addition.

[0063] Determine the optimal addition amount: fix the distillation time to 180s, add different types and masses of magnesium oxide into the capsule, and repeat 3 times for each sample, as shown in Table 1.

[0064] Determine the optimal distillation time: The fixed addition amount is the optimal addition amount, and the samples are distilled at different distillation times. Each sample is repeated 3 times. See Table 2 for details.

[0065] Table 1 Optimal addition amount grouping table

[0066]

[0067] Table 2 Optimal distillation time grouping table

[0068]

[0069] 2.2 Instrument settings:

[0070] This experiment uses an automatic Kjeldahl nitrogen analyzer, turns off the automatic waste discharge, automatic alkali addition and automatic water addition functions, sets the alkali and water addition volumes to 0 mL, and sets the distillation time according to Tables 1 and 2.

[0071] 2.3 Sample determination

[0072] Pipette 10 ml of the test solution into the distillation tube, add magnesium oxide capsules, connect to the distiller and start distillation using the set program. After the distillation is completed, record the volume of the consumed hydrochloric acid standard titrant.

[0073] 2.4 Data Analysis

[0074] Record the volume of hydrochloric acid consumed by the sample and use Graphpad Pism9.5 to make a line graph.

[0075] 3. Results and Analysis

[0076] Depend on Figure 1It can be seen that the hydrochloric acid consumption of adding 0.08g, 0.06g and 0.04g of light magnesium oxide is basically the same. After reducing the amount of light magnesium oxide to 0.2g and 0.1g, the hydrochloric acid consumption shows a significant decrease. The significant decrease in hydrochloric acid consumption indicates that the amount of light magnesium oxide added is too little, and the alkaline environment in the distillation tube is not enough. Therefore, the amount of light magnesium oxide added should be ≥0.04g; the hydrochloric acid consumption of adding 0.25g, 0.20g and 0.15g of magnesium oxide is basically the same. After reducing the amount of magnesium oxide to 0.10g and 0.05g, the hydrochloric acid consumption shows a significant decrease. The amount of magnesium oxide added should be ≥0.15g; the hydrochloric acid consumption of adding 0.25g, 0.20g and 0.15g of heavy magnesium oxide is basically the same. After reducing the amount of heavy magnesium oxide to 0.10g and 0.05g, the hydrochloric acid consumption shows a significant decrease. The amount of heavy magnesium oxide added should be ≥0.15g.

[0077] Depend on Figure 2 It can be seen that: when the distillation time of light magnesium oxide is reduced to 60s, the consumption of hydrochloric acid is significantly reduced, and the distillation time of light magnesium oxide should be ≥90s; when the distillation time of magnesium oxide is reduced to 90s, the consumption of hydrochloric acid is significantly reduced, and the distillation time of magnesium oxide should be ≥120s; when the distillation time of heavy magnesium oxide is reduced to 90s, the consumption of hydrochloric acid is significantly reduced, and the distillation time of heavy magnesium oxide should be ≥120s.

[0078] 4. Conclusion

[0079] When using light magnesium oxide, the amount added should be ≥0.04g, and the distillation time should be ≥90s; when using magnesium oxide, the amount added should be ≥0.15g, and the distillation time should be ≥120s; when using heavy magnesium oxide, the amount added should be ≥0.15g, and the distillation time should be ≥120s.

[0080] Test Example 2

[0081] The volatile basic nitrogen of a certain blood globulin powder sample was tested, and the estimated volatile basic nitrogen was above 80 mg / 100 g. The concentration of the standard hydrochloric acid titration solution used was 0.1148 mol / L.

[0082] 1. Sample Processing

[0083] Weigh 10g of blood globulin powder to an accuracy of 0.001, place it in a stoppered conical bottle, accurately add 100ml of 20g / L trichloroacetic acid solution, cover the stopper and ultrasonicate for 30min. Take about 60ml of the sample in a 100ml centrifuge tube, centrifuge and take the supernatant to be tested.

[0084] 2. Experimental Methods

[0085] 2.1 Experimental design

[0086] The experiment was divided into a capsule group and a national standard group. The capsule group: 0.10g of light magnesium oxide in a hollow gelatin capsule, and the national standard group directly added 1.00g of light magnesium oxide, and each group was done 4 parallels. The national standard group refers to the national standard: GB5009.228-2016 "National Food Safety Standard Determination of Volatile Basic Nitrogen in Food".

[0087] 2.2 Instrument settings

[0088] For an automatic Kjeldahl nitrogen analyzer with automatic reagent addition and waste discharge functions, turn off the automatic waste discharge, automatic alkali addition and automatic water addition functions, set the alkali and water addition volume to 0mL, and set the distillation time to 180s. For a Kjeldahl nitrogen analyzer without automatic reagent addition and waste discharge functions, set the alkali and water addition volume to 0mL, and set the distillation time to 180s.

[0089] 2.3 Reagent blank determination

[0090] Add 10ml of 20g / L trichloroacetic acid solution to the distillation tube. For the capsule group, add 1 capsule pre-loaded with 0.10g of light magnesium oxide to the distillation tube, connect it to the distiller and start distillation using the set program. For the national standard group, add

[0091] 1.00g of light magnesium oxide, immediately connect to the distiller and start distillation using the set program. After the distillation is completed, record the volume of hydrochloric acid standard titration solution consumed. Make 4 parallels and record the average of the parallels as V2.

[0092] 2.4 Sample determination

[0093] Add the test solution into the distillation tube. Add 1 capsule pre-loaded with 0.10g light magnesium oxide to the capsule group, connect to the distiller and start distillation using the set program. Add 1.00g light magnesium oxide directly to the distillation tube for the national standard group, immediately connect to the distiller and start distillation using the set program. After distillation, record the volume of hydrochloric acid standard titration solution consumed. Make 4 parallels, and record the volume of hydrochloric acid consumed in each parallel as V1.

[0094] 2.5 Data Analysis

[0095] Record the sample weight (m), dissolved volume (V0), sampling volume (V), blank hydrochloric acid consumption volume (V2) and sample hydrochloric acid consumption volume (V1). The hydrochloric acid standard titration solution is calibrated to a concentration of 0.1148 mol / L (c). Calculate the volatile basic nitrogen content (X).

[0096]

[0097] Graphpad Pism9.5 was used to draw a scatter plot of the mean plus standard deviation of blank consumption, sample consumption and volatile basic nitrogen content of the capsule method and the national standard method to compare the results obtained by the two methods.

[0098] 3. Results and Analysis

[0099] Table 3 Blood globulin powder test results

[0100]

[0101] From Table 3 and Figure 3 It can be seen that compared with the national standard group, the capsule group has a smaller standard deviation and a lower degree of data dispersion, indicating that the capsule group is more accurate. The volatile basic nitrogen content of the capsule group is slightly higher than that of the national standard group because the sample of the national standard group begins to react after adding magnesium oxide, and a small amount of volatile basic nitrogen escapes before connecting the distillation device, making the result slightly smaller. It can be seen that the method of the present invention is superior to the national standard method.

[0102] Test Example 3

[0103] The volatile basic nitrogen content in the small peptide feed enzymatic hydrolysate was tested, and it was estimated that the volatile basic nitrogen was below 20 mg / 100 g. The concentration of the hydrochloric acid standard titration solution used was 0.01148 mol / L.

[0104] 1. Sample Processing

[0105] Take about 100 ml of enzymatic hydrolysate, add 2 g of trichloroacetic acid to make the concentration of trichloroacetic acid in the mixed solution about 20 g / L, shake well and let it stand for more than 15 minutes, take about 60 ml of the sample in a 100 ml centrifuge tube, centrifuge and take the supernatant to be tested.

[0106] 2. Experimental Methods

[0107] 2.1 Experimental design

[0108] The experiment was divided into a capsule group and a national standard group. The capsule group: 0.10g of light magnesium oxide in a hollow gelatin capsule, and the national standard group directly added 1.00g of light magnesium oxide, and each group was done 4 parallels. The national standard group refers to the national standard: GB5009.228-2016 "National Food Safety Standard Determination of Volatile Basic Nitrogen in Food".

[0109] 2.2 Instrument settings

[0110] For an automatic Kjeldahl nitrogen analyzer with automatic reagent addition and waste discharge functions, turn off the automatic waste discharge, automatic alkali addition and automatic water addition functions, set the alkali and water addition volume to 0mL, and set the distillation time to 180s. For a Kjeldahl nitrogen analyzer without automatic reagent addition and waste discharge functions, set the alkali and water addition volume to 0mL, and set the distillation time to 180s.

[0111] 2.3 Reagent blank determination

[0112] Add 10ml of 20g / L trichloroacetic acid solution to the distillation tube. For the capsule group, add 1 capsule pre-loaded with 0.10g of light magnesium oxide to the distillation tube, connect it to the distiller and start distillation using the set program. For the national standard group, add

[0113] 1.00g of light magnesium oxide, immediately connect to the distiller and start distillation using the set program. After the distillation is completed, record the volume of hydrochloric acid standard titration solution consumed. Make 4 parallels and record the average of the parallels as V2.

[0114] 2.4 Sample determination

[0115] Add the test solution into the distillation tube. Add 1 capsule pre-loaded with 0.10g light magnesium oxide to the capsule group, connect to the distiller and start distillation using the set program. Add 1.00g light magnesium oxide directly to the distillation tube for the national standard group, immediately connect to the distiller and start distillation using the set program. After distillation, record the volume of hydrochloric acid standard titration solution consumed. Make 4 parallels, and record the volume of hydrochloric acid consumed in each parallel as V1.

[0116] 2.5 Data Analysis

[0117] Record the sample weight (m), dissolved volume (V0), sampling volume (V), blank hydrochloric acid consumption volume (V2) and sample hydrochloric acid consumption volume (V1). The hydrochloric acid standard titration solution is calibrated to a concentration of 0.01148 mol / L (c). Calculate the volatile basic nitrogen content (X).

[0118]

[0119] Graphpad Pism9.5 was used to draw a scatter plot of the mean plus standard deviation of blank consumption, sample consumption and volatile basic nitrogen content of the capsule method and the national standard method to compare the results obtained by the two methods.

[0120] 2. Data Analysis

[0121] Table 4 Enzyme hydrolysate test results

[0122]

[0123]

[0124] From Table 4, Figure 4 It can be seen that compared with the national standard group, the capsule group has a smaller standard deviation and lower data dispersion, indicating that the capsule group is more accurate.

[0125] In summary, compared with the existing national standard method, the method of the present invention is more accurate and the results obtained are more stable.

[0126] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A method for detecting volatile basic nitrogen, characterized in that: The following steps are involved: Sample processing; Reagent preparation: including the preparation of hydrochloric acid standard titration solution or sulfuric acid standard titration solution. Preparation of magnesium oxide capsules: adding magnesium oxide into hollow capsules to obtain magnesium oxide capsules. The determination is performed using an automatic Kjeldahl nitrogen analyzer. When performing a reagent blank determination and a determination of a sample to be tested, the magnesium oxide capsule is respectively added into a distillation tube of the automatic Kjeldahl nitrogen analyzer for distillation.

2. The method for detecting volatile basic nitrogen according to claim 1, characterized in that: The samples include food, feed raw materials, fermentation broth and enzymatic hydrolysate; The processing method for feed raw materials, fermentation broth and enzymatic hydrolysate includes: mixing and leaching the sample with trichloroacetic acid solution to obtain a sample solution; taking the sample solution for centrifugation or filtering, and taking the supernatant or filtrate to obtain the sample to be tested.

3. The method for detecting volatile basic nitrogen according to claim 1, characterized in that: The hollow capsules are animal-derived hollow capsules.

4. The method for detecting volatile basic nitrogen according to claim 1, characterized in that: When measuring the sample to be tested, the amount of magnesium oxide used is 0.04-1.00g.

5. The method for detecting volatile basic nitrogen according to claim 1, characterized in that: The magnesium oxide used is selected from light magnesium oxide, ordinary magnesium oxide or heavy magnesium oxide, preferably light magnesium oxide.

6. The method for detecting volatile basic nitrogen according to claim 5, characterized in that: For the test sample, when light magnesium oxide is selected, the amount of light magnesium oxide is ≥0.04g, and the distillation time is ≥90s; when ordinary magnesium oxide is selected, the amount of ordinary magnesium oxide is ≥0.15g, and the distillation time is ≥120s; when heavy magnesium oxide is selected, the amount of heavy magnesium oxide is ≥0.15g, and the distillation time is ≥120s.

7. The method for detecting volatile basic nitrogen according to claim 2, characterized in that: After the sample was extracted with trichloroacetic acid solution, it was determined by an automatic Kjeldahl nitrogen analyzer. The amount of water and alkali added to the automatic Kjeldahl nitrogen analyzer was set to 0 ml. When performing a reagent blank determination, a trichloroacetic acid solution and a magnesium oxide capsule with an equal volume to the sample were added to the distillation tube. When performing a determination of the sample to be tested, the sample and the magnesium oxide capsule were added to the distillation tube.

8. The method for detecting volatile basic nitrogen according to claim 1, characterized in that: When the volatile basic nitrogen content in the sample to be tested is ≤20mg / 100g, the concentration of the standard hydrochloric acid titration solution or the standard sulfuric acid titration solution used is 0.010-0.015mol / L; when the volatile basic nitrogen content in the sample to be tested is 20-80mg / 100g, the concentration of the standard hydrochloric acid titration solution or the standard sulfuric acid titration solution used is 0.01-0.05mol / L; when the volatile basic nitrogen content in the sample to be tested is ≥80mg / 100g, the concentration of the standard hydrochloric acid titration solution or the standard sulfuric acid titration solution used is 0.10-0.15mol / L.

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