阅读说明：本技术 一种食品中蛋白质含量的检测方法 (A kind of detection method of protein content in foodstuff ) 是由 庄泽龙 李厚标 李少军 于 2019-07-22 设计创作，主要内容包括：本发明属于食品检测技术领域,具体涉及一种食品中蛋白质含量的检测方法。本申请的食品中蛋白质含量的检测方法,通过测试未处理样品中的氮含量和添加沉淀剂A和沉淀剂B后样品中的氮含量,从而获得样品中的蛋白质含量,与现有技术相比,该蛋白质含量检测方法先通过添加沉淀剂A和沉淀剂B使得样品中的蛋白质沉淀,从而获得非蛋白的氮含量,改进了测试流程,使得测得的蛋白质含量准确度更高,可以更加真实的反应食品中蛋白质的含量,且该测试流程操作简单,便于实验人员操作。(The invention belongs to technical field of food detection, and in particular to a kind of detection method of protein content in foodstuff.The detection method of the protein content in foodstuff of the application, pass through the nitrogen content in sample after the nitrogen content and addition precipitating reagent A and precipitating reagent B in test untreated samples, to obtain the protein content in sample, compared with prior art, the method for detecting protein content first passes through addition precipitating reagent A and precipitating reagent B and makes protein precipitation in sample, to obtain the nitrogen content of non-protein, improve testing process, so that the protein content accuracy measured is higher, the content of Protein in Food can more really be reacted, and the testing process is easy to operate, convenient for experimenter's operation.)

1. a kind of detection method of protein content in foodstuff, it is characterised in that:

S1: the sample M and N of two parts of equivalent are weighed；

S2: sample M being placed in be added in beaker and distilled water and is stirred, be then added into beaker precipitating reagent A and precipitating reagent B into Solution after mixing is transferred to centrifuge tube centrifuge separation 30-50min by row mixing；

S3: by step 1 sample N and step 2 in supernatant in centrifuge tube be respectively placed in digestion tube, and sulfuric acid is added Copper, potassium sulfate and the concentrated sulfuric acid；

S4: it is in clarification blue-green that the digestion tube in step S3, which is placed in digestion furnace, and is heated to resolution liquid in pipe in solution, Water is added after cooling, obtains stock solution M1 and solution N1；

S5: boric acid solution and mixed indicator being added into receiving bottle, and are inserted into the lower end of condenser pipe under the liquid level of receiving bottle；

S6: the digestion tube containing solution M1 is mounted on azotometer, and alkaline solution to digestion tube is added in digestion tube and is in Sepia or bronzing are not taken off；It opens distillation function and is passed through steam, collect distillate, collection is rinsed with a small amount of water cold after the completion Solidifying pipe lower end, removes receiving bottle；

S7: it is calculated with solution in standard acidic solution titration receiving bottle to grey or bluish violet, and according to the volume of the acid of consumption Nitrogen content X in sample M₁；

S8: the digestion tube containing solution N1 is operated by step S5-S7, obtains the nitrogen content X in sample N₂；

S9: according to the nitrogen content X in the sample M of acquisition₁With the nitrogen content X in sample N₂Calculate the content of protein in sample.

2. the detection method of protein content in foodstuff according to claim 1, it is characterised in that: the step S3 is also wrapped It includes and takes with the same amount of copper sulphate of processing sample, potassium sulfate, the concentrated sulfuric acid in digestion tube, and operated by step S4-S7, counted Calculate the nitrogen content X in reagent₀。

3. the detection method of protein content in foodstuff according to claim 2, it is characterised in that: albumen in the sample The content of matter is equal to the nitrogen content X in sample N₂Subtract the nitrogen content X in sample M₁With the nitrogen content X in reagent₀。

4. the detection method of protein content in foodstuff according to claim 1, it is characterised in that: sink in the step S2 Shallow lake agent A includes one of the potassium ferricyanide, the sodium ferricyanide or a variety of.

5. the detection method of protein content in foodstuff according to claim 4, it is characterised in that: the precipitating reagent A with The mass percent of sample is 4.5-6.5:0.2-2.0.

6. the detection method of protein content in foodstuff according to claim 1, it is characterised in that: the precipitating reagent B packet Include zinc acetate, the mass percent of the zinc acetate and sample is 4.5-6.5:0.2-2.0.

7. the detection method of protein content in foodstuff according to claim 1, it is characterised in that: the step S4 resolution It includes: digestion tube to be placed in digestion furnace to be warming up to 180-220 DEG C, and constant temperature is anti-that pipe, which is placed in the heating stepses in digestion furnace, It answers 1-3 hours；It then continues to be warming up to 380-420 DEG C, isothermal reaction to solution is in clarification blue-green, and solution is in clarification blue-green After continue heat 0.3-1.0h.

8. the detection method of protein content in foodstuff according to claim 1, it is characterised in that: boron in the step S5 The concentration of acid solution is 2%.

9. the detection method of protein content in foodstuff according to claim 1, it is characterised in that: alkali in the step S6 Property solution includes one of sodium hydroxide solution, potassium hydroxide solution, sodium acetate solution, liquor kalii acetici or a variety of.

10. the detection method of protein content in foodstuff according to claim 1, it is characterised in that: the standard acidic Solution includes 0.05N sulfuric acid solution or 0.05N hydrochloric acid solution.

Technical field

The invention belongs to technical field of food detection, and in particular to a kind of detection method of protein content in foodstuff.

Background technique

Food/agricultural product fraud is the problem of current world is faced and paid close attention to jointly.EU Committee's health and disappear Expense person's policy represents John Dalli and thinks: food fraud belongs to a kind of " important asking of being driven of huge potential economic interests Topic ".Food fraud is a kind of deceit practiced against consumers, mainly passes through the shape to circulate on the market that poor quality food is adulterated Formula, or carried out in the form of supplementary material inferior replaces material at high price, post fictitious label in processed food.

Between past many decades, the principal mode of food/agricultural product fraud first is that " complete with relatively inexpensive substitute Or part substitutes valuable ingredient ".By taking fresh milk purchases link as an example, initial illegal retailer is by being added water in fresh milk To improve income.After acquiring firm judges water mixing situation by way of the nutrition contents such as detection protein, illegal quotient Dealer adds various substances manually to influence testing result.After the detection method for adulterated substance is succeeded in developing, illegal quotient Dealer can upgrade adulterated means again.Only during past more than ten year, the adulterant of lactoprotein just has been subjected to urea, melamine The substances such as amine, leather hydrolysate, soybean protein isolate.

Other than cream is with dairy products, meat and meat products, silk, wool textile, leather and fur products, using donkey-hide gelatin as the drug of representative Encountered adulteration.The phenomenon that adulteration has not only hit regular legitimate enterprise, generates " bad money drives out good money ", and The brand image for having damaged " made in China " reduces Chinese commodity in the price of international market.

The main reason for above situation occur is " detection of adulterations ".I.e. present detection technique is usually in catalysis fire-bar Protein under part in decomposing food, makes it generate ammonia, and ammonia generates ammonium sulfate in conjunction with sulfuric acid.Swim ammonia by distillation of alkalizing again From, and titrated after being absorbed with boric acid with sulfuric acid or Hydrochloric Standard Titration, nitrogen content is calculated according to the consumption of acid, multiplied by Conversion coefficient, the as content of protein.This processing mode makes the content of protein in sample higher, non-because containing in sample Proteinic nitrogen such as organic nitrogen amino acid, inorganic nitrogen ammonium salt etc..

Summary of the invention

In order to solve the problems such as above-mentioned existing detection technique detection protein content is inaccurate, the present invention provides a kind of food The detection method of middle protein content.

To achieve the above object, the technical scheme adopted by the invention is that: a kind of detection side of protein content in foodstuff Method,

S1: the sample M and N of two parts of equivalent are weighed；

S2: sample M is placed in, distilled water is added in beaker and stirs, precipitating reagent A and precipitating are then added into beaker Agent B is mixed, and solution after mixing is transferred to centrifuge tube centrifuge separation 30-50min；

S3: by step 1 sample N and step 2 in supernatant in centrifuge tube be respectively placed in digestion tube, and sulphur is added Sour copper, potassium sulfate and the concentrated sulfuric acid；

S4: it is in that clarification is bluish-green that the digestion tube in step S3, which is placed in digestion furnace, and is heated to resolution liquid in pipe in solution Water is added in color after cooling, obtain stock solution M1 and solution N1；

S5: boric acid solution and mixed indicator being added into receiving bottle, and make the liquid of the lower end insertion receiving bottle of condenser pipe Under face；

S6: the digestion tube containing solution M1 is mounted on azotometer, and alkaline solution is added to resolution in digestion tube Pipe does not take off in sepia or bronzing；It opens distillation function and is passed through steam, collect distillate, rushed after the completion of collecting with a small amount of water Condenser pipe lower end is washed, receiving bottle is removed；

S7: with solution in standard acidic solution titration receiving bottle to grey or bluish violet, and the volume of the acid according to consumption Calculate the nitrogen content X in sample M₁；

S8: the digestion tube containing solution N1 is operated by step S5-S7, obtains the nitrogen content X in sample N₂；

S9: according to the nitrogen content X in the sample M of acquisition₁With the nitrogen content X in sample N₂Protein contains in calculating sample Amount.

Further, step S3 further includes taking with the same amount of copper sulphate of processing sample, potassium sulfate, the concentrated sulfuric acid in digestion tube It is interior, and operated by step S4-S7, calculate the nitrogen content X in reagent₀。

Further, the content of protein is equal to the nitrogen content X in sample N in sample₂Subtract the nitrogen content X in sample M₁ With the nitrogen content X in reagent₀。

Further, precipitating reagent A includes one of the potassium ferricyanide, the sodium ferricyanide or a variety of in step S2.

Further, the mass percent of precipitating reagent A and sample is 4.5-6.5:0.2-2.0.

Further, precipitating reagent B includes zinc acetate, and the mass percent of the zinc acetate and sample is 4.5-6.5:0.2- 2.0。

Further, it includes: that digestion tube is placed in resolution that step S4 digestion tube, which is placed in the heating stepses in digestion furnace, 180-220 DEG C, and isothermal reaction 1-3 hours are warming up in furnace；It then continues to be warming up to 380-420 DEG C, isothermal reaction to solution In clarification blue-green, solution is in continue to heat 0.3-1.0h after clarifying blue-green.

Further, the concentration of boric acid solution is 2% in step S5.

Further, step S6 neutral and alkali solution includes sodium hydroxide solution, potassium hydroxide solution, sodium acetate solution, vinegar One of sour potassium solution is a variety of.

Further, standard acidic solution includes 0.05N sulfuric acid solution or 0.05N hydrochloric acid solution.

The present invention provides a kind of detection method of protein content in foodstuff, passes through the nitrogen content in test untreated samples With the nitrogen content after addition precipitating reagent A and precipitating reagent B in sample, so that the protein content in sample is obtained, with the prior art It compares, which first passes through addition precipitating reagent A and precipitating reagent B and makes protein precipitation in sample, from And the nitrogen content of non-protein is obtained, testing process is improved, so that the protein content accuracy measured is higher, it can be more true The content of real reaction Protein in Food, and the testing process is easy to operate, operates convenient for experimenter.

Detailed description of the invention

Fig. 1 is the flow chart of the detection method of protein content in foodstuff.

Specific embodiment

Following will be combined with the drawings in the embodiments of the present invention, is clearly and completely retouched to the technical solution in the present invention It states, it is clear that the described embodiments are merely a part of the embodiments of the present invention, instead of all the embodiments.