Method for detecting sodium hypochlorite content in chicken

Abstract

The application provides a method for detecting the content of sodium hypochlorite in chicken, and belongs to the technical field of quantitative detection. Terahertz spectrum testing is performed on a dried chicken sample to obtain the peak height of a sodium hypochlorite characteristic peak; then, according to a standard curve and the peak height of the sodium hypochlorite characteristic peak, the content of sodium hypochlorite in the chicken is obtained; the frequency of the sodium hypochlorite characteristic peak is 1.10 THz or 1.25 THz; and the standard curve is a fitting curve of the mass content of sodium hypochlorite in the chicken and the peak height of the sodium hypochlorite characteristic peak. Different molecules exhibit different absorption peaks in terahertz absorption spectrum, and the application detects the content of sodium hypochlorite in chicken by using a terahertz spectrum method, and obtains the content of sodium hypochlorite in chicken by using the fitting relationship between the peak height of the sodium hypochlorite absorption peak and the content of sodium hypochlorite. The method provided by the application is simple, and can quickly and accurately obtain the content of sodium hypochlorite in chicken.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of quantitative detection, in particular to a method for detecting the content of sodium hypochlorite in chicken. BACKGROUND

[0002] Cold fresh chicken refers to chicken carcass subjected to blast chilling so as to be cooled to 0-4 DEG C within 1 hour, and kept in the range of 0-4 DEG C in the subsequent processing, storage, transportation and retail processes. Cold fresh chicken has no big difference in taste compared with fresh chicken, and the shelf life is greatly prolonged, which is conducive to the processing and sale of chicken.

[0003] Sodium hypochlorite solution with a concentration of 50-100 mg / L is often used for sterilization and disinfection in the production process of cold fresh chicken. The sodium hypochlorite solution can effectively kill harmful microorganisms in chicken, but if the concentration is too high, the residual amount of sodium hypochlorite in chicken is too large, which may cause harm to consumers, and even food poisoning, seriously threatening the health and safety of human body.

[0004] However, the iodine-thiosulfate method needs titration experiment, and the operation is complex and low in efficiency. SUMMARY

[0005] Therefore, the present application aims to provide a method for detecting the content of sodium hypochlorite in chicken. The method for detecting the content of sodium hypochlorite in chicken provided by the present application can simply, quickly and accurately obtain the content of sodium hypochlorite in chicken.

[0006] In order to achieve the above-mentioned application purposes, the present application provides the following technical solutions.

[0007] The present application provides a method for detecting the content of sodium hypochlorite in chicken, comprising the following steps:

[0008] (1) performing terahertz spectrum test on the dry chicken sample to obtain the peak height of the sodium hypochlorite characteristic peak;

[0009] (2) obtaining the content of sodium hypochlorite in chicken according to the predetermined standard curve and the peak height of the sodium hypochlorite characteristic peak in step (1); the frequency of the sodium hypochlorite characteristic peak is 1.10 THz or 1.25 THz; and the standard curve is a fitting curve of the mass content of sodium hypochlorite in chicken and the peak height of the sodium hypochlorite characteristic peak.

[0010] Preferably, the measurement mode of the terahertz spectrum test is a spectral line mode, the sample bin is a transmission module, the average number is 1, the sample thickness is 1 mm, and the scanning range is 50*50 mm.

[0011] Preferably, when the frequency of the sodium hypochlorite characteristic peak is 1.25 THz, the fitting curve is a linear relationship fitting curve.

[0012] Preferably, when the frequency of the sodium hypochlorite characteristic peak is 1.10 THz, the fitting curve is a third-order polynomial fitting curve.

[0013] Preferably, the preparation method of the dried chicken sample comprises the following steps:

[0014] The chicken slices are dried to obtain a dried chicken sample; the drying temperature is 43-47 DEG C, and the time is 2-2.5 h.

[0015] Preferably, the size of the chicken slices is 2±0.1 cm in length, 2±0.1 cm in width, and 0.1 cm in thickness.

[0016] The present application provides a method for detecting the content of sodium hypochlorite in chicken, comprising the following steps: (1) performing terahertz spectrum test on a dried chicken sample to obtain the peak height of a sodium hypochlorite characteristic peak; (2) obtaining the content of sodium hypochlorite in chicken according to a predetermined standard curve and the peak height of the sodium hypochlorite characteristic peak in step (1); the frequency of the sodium hypochlorite characteristic peak is 1.10 THz or 1.25 THz; and the standard curve is a fitting curve of the mass content of sodium hypochlorite in chicken and the peak height of the sodium hypochlorite characteristic peak. Since different molecules exhibit different absorption peaks in the terahertz absorption spectrum, the present application detects the content of sodium hypochlorite in chicken by using the terahertz spectrum method, and obtains the content of sodium hypochlorite in chicken by using the fitting relationship between the peak height of the sodium hypochlorite absorption peak and the content of sodium hypochlorite. The method provided by the present application is simple, and can quickly and accurately obtain the content of sodium hypochlorite in chicken. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 is the terahertz spectrum of the first sodium hypochlorite solid standard sample;

[0018] Figure 2 is the terahertz spectrum of the fourth sodium hypochlorite solid standard sample;

[0019] Figure 3 is the linear relationship curve of the concentration of sodium hypochlorite soaking solution and the sodium hypochlorite characteristic peak at 1.25 THz;

[0020] Figure 4 is the linear relationship curve of the concentration of sodium hypochlorite soaking solution and the sodium hypochlorite characteristic peak at 1.10 THz;

[0021] Figure 5 is the third-order polynomial relationship curve of the concentration of sodium hypochlorite soaking solution and the sodium hypochlorite characteristic peak at 1.10 THz;

[0022] Figure 6 is a linear relationship curve of effective chlorine residual concentration in chicken and concentration of sodium hypochlorite soaking solution. DETAILED DESCRIPTION

[0023] The present application provides a method for detecting the content of sodium hypochlorite in chicken, comprising the following steps:

[0024] (1) performing terahertz spectrum test on the dry chicken sample to obtain the peak height of the sodium hypochlorite characteristic peak;

[0025] (2) obtaining the content of sodium hypochlorite in chicken according to the predetermined standard curve and the peak height of the sodium hypochlorite characteristic peak in step (1); the frequency of the sodium hypochlorite characteristic peak is 1.10 THz or 1.25 THz; the standard curve is a fitting curve of the mass content of sodium hypochlorite in chicken and the peak height of the sodium hypochlorite characteristic peak.

[0026] The present application performs terahertz spectrum test on the dry chicken sample to obtain the peak height of the sodium hypochlorite characteristic peak. In the present application, the preparation method of the dry chicken sample preferably comprises the following steps:

[0027] drying the chicken slices to obtain the dry chicken sample.

[0028] The present application does not have special requirements for the type of chicken, and chicken known to those skilled in the art can be used in the method of the present application to detect the residual amount of sodium hypochlorite. In the present application, the size of the chicken slices is preferably 2x2x1 cm. In the present application, the drying method is preferably oven drying, and the drying temperature is preferably 43-47℃, more preferably 45℃; the time is preferably 2-2.5 h, more preferably 2.2 h.

[0029] The present application does not have special requirements for the test method of the terahertz spectrum, and the parameters of the terahertz spectrum are as follows: the measurement mode is the spectral line mode, the sample bin is the transmission module, the average number is 1, the sample thickness is 1 mm, and the scanning range is 50x50 mm. In the present application, the frequency of the sodium hypochlorite characteristic peak is 1.10 THz or 1.25 THz. In the present application, when the frequency of the sodium hypochlorite characteristic peak is 1.25 THz, the fitting curve is a linear relationship fitting curve. The present application does not have special requirements for the method of drawing the standard curve, and the standard curve can be drawn using methods known to those skilled in the art. In the present application, the mass content (mg / g) of sodium hypochlorite is positively correlated with the peak height. In the present application, the detection limit of the fitting curve is 0.1716 mg / g.

[0030] In the present application, when the standard curve is a linear relationship fitting curve, the method for obtaining the standard curve preferably comprises the following steps:

[0031] (1) accurately prepare sodium hypochlorite solutions with concentrations of 200, 300, 400, 500, and 600 mg / L to obtain sodium hypochlorite standard solutions with a series of concentrations;

[0032] (2) prepare frozen chicken breast into thin slices with a length of 2±0.1 cm, a width of 2±0.1 cm, and a thickness of 0.1 cm, and dry the thin slices at 43-47°C for 2-2.5 h to obtain dried chicken;

[0033] (3) soak the chicken in the sodium hypochlorite standard solutions with a series of concentrations for 20 min, and determine the sodium sulfite content (mg / g) in the soaked chicken by the iodine-sodium thiosulfate method;

[0034] (4) dry the soaked chicken, and perform terahertz spectrum testing on the obtained dried chicken sample to obtain the peak height of the characteristic peak of sodium hypochlorite at 1.25 THz, and plot a linear relationship fitting curve with the sodium sulfite content obtained in step (3) as the abscissa and the peak height as the ordinate, to obtain a standard curve.

[0035] The steps (1) and (2) are not limited in time sequence.

[0036] In the present application, when the frequency of the characteristic peak of sodium hypochlorite is 1.10 THz, the fitting curve is a third-order polynomial fitting curve. The present application does not have special requirements for the method of drawing the standard curve, and the standard curve can be drawn by using a method well known to those skilled in the art. In the present application, the detection limit of the fitting curve is 0.1716 mg / g.

[0037] In the present application, when the standard curve is a third-order polynomial fitting curve, the method for obtaining the standard curve preferably comprises the following steps:

[0038] (1) accurately prepare sodium hypochlorite solutions with concentrations of 200, 300, 400, 500, and 600 mg / L to obtain sodium hypochlorite standard solutions with a series of concentrations;

[0039] (2) prepare frozen chicken breast into thin slices with a length of 2±0.1 cm, a width of 2±0.1 cm, and a thickness of 0.1 cm, and dry the thin slices at 43-47°C for 2-2.5 h to obtain dried chicken;

[0040] (3) soak the chicken in the sodium hypochlorite standard solutions with a series of concentrations for 20 min, and determine the sodium sulfite content (mg / g) in the soaked chicken by the iodine-sodium thiosulfate method;

[0041] (4) drying the soaked chicken, and testing the obtained dried chicken sample by terahertz spectrum to obtain the peak height of the characteristic peak of sodium hypochlorite at 1.1 THz, and drawing a third-order polynomial fitting curve with the sodium hypochlorite content obtained in step (3) as the horizontal coordinate and the peak height as the vertical coordinate, to obtain a standard curve.

[0042] The steps (1) and (2) are not limited in time sequence.

[0043] The detection method of the sodium hypochlorite content in chicken provided by the present application will be described in detail below in combination with examples, but they should not be understood as limiting the protection scope of the present application.

[0044] Example 1

[0045] (I) accurately weighing 200 mg of sodium hypochlorite powder, and pressing the sodium hypochlorite powder into tablets by using a tablet press to prepare six sodium hypochlorite solid standard samples.

[0046] The terahertz spectrum of the six sodium hypochlorite solid standard samples was collected by using the transmission module of the terahertz time-domain spectrometer CCT-1800. When collecting the spectrum, nitrogen was applied to the closed environment to maintain the temperature stability of the collection environment and to keep the humidity below 20%. The spectrum of each sample can be seen to have two peaks at two specific positions, one at about 1.10 THz and the other at about 1.25 THz. The terahertz spectrum of the first sample is shown in FIG. 1, and the terahertz spectrum of the fourth sample is shown in FIG. 2. As can be seen from FIGS. 1 and 2, the two peaks at 1.10 THz and 1.25 THz are both characteristic peaks of sodium hypochlorite in the terahertz spectrum, and when the concentration is higher than the detection limit, they can be used as the detection markers of sodium hypochlorite residues. Figure 1 Figure 2 Figure 1 Figure 2 As can be seen from FIGS. 1 and 2, the two peaks at 1.10 THz and 1.25 THz are both characteristic peaks of sodium hypochlorite in the terahertz spectrum, and when the concentration is higher than the detection limit, they can be used as the detection markers of sodium hypochlorite residues.

[0047] Five healthy white-feathered chickens were purchased on the market, and the chicken breast meat was taken after being slaughtered and frozen at -15℃. The frozen chicken breast meat was prepared into uniform slices with a size of 2×2×1 cm and dried in a constant-temperature oven at 45℃ for 2 h. The sodium hypochlorite solution was diluted by 312, 208, 156, 125 and 104 times, respectively, to obtain sodium hypochlorite standard solutions with concentrations of 200, 300, 400, 500 and 600 mg / L, respectively. The dried chicken breast meat slices were contaminated by soaking in the sodium hypochlorite standard solutions, and the number of chicken breast meat slices in each group was 5. After soaking for 20 min, the chicken breast meat slices were dried at 45℃, and the terahertz spectrum was measured.

[0048] (1) The average peak height at 1.25 THz in the terahertz spectrum of the chicken treated by the sodium hypochlorite standard solution with different concentrations of sodium hypochlorite is shown in Table 1.

[0049] ​​​Table 1 Average peak height at 1.25 THz in the terahertz spectrum of chicken treated by different concentrations of soaking solution

[0050]

[0051] A linear standard curve was drawn according to the data in Table 1, and the results are shown in Figure 3 Figure 3 It can be seen that the average peak height and the concentration of sodium hypochlorite soaking solution have a good linear relationship, and the linear relationship curve is y = 0.0061x + 2.7499, R 2 = 0.9673, x is the concentration of sodium hypochlorite, unit: mg / L, and y is the peak height, unitless. This can quantitatively illustrate the relationship between the peak height of the characteristic peak of sodium hypochlorite at 1.25 THz in the terahertz spectrum and the concentration of sodium hypochlorite used.

[0052] (2) The average peak height at 1.10 THz in the terahertz spectrum of chicken treated by different concentrations of soaking solution is shown in Table 2.

[0053] Table 2 Average peak height at 1.10 THz in the terahertz spectrum of chicken treated by different concentrations of soaking solution

[0054]

[0055] A linear standard curve was drawn according to the data in Table 2, and the results are shown in Figure 4 Figure 4 It can be seen that a good linear relationship between the average peak height and the concentration of the soaking solution cannot be obtained, indicating that there is no linear relationship between the intensity of the sodium hypochlorite characteristic peak at 1.10 THz and the concentration of the soaking solution.

[0056] The data was fitted by a third-order polynomial, and the results are shown in Figure 5 Figure 5 It can be seen that when the third-order fitting is performed, the characteristic peak at 1.10 THz has a good non-linear relationship with the concentration of the soaking solution, and the third-order polynomial fitting curve is y = -2E-0.7x 2 + 0.0003x 2 - 0.0901x + 12.941, R 2 = 0.9811, x is the concentration of sodium hypochlorite, unit: mg / L, and y is the peak height, unitless. This can quantitatively illustrate the relationship between the peak height of the characteristic peak of sodium hypochlorite at 1.15 THz in the terahertz spectrum and the concentration of sodium hypochlorite soaking solution used.

[0057] ​​​In summary, it can be illustrated that both 1.10 THz and 1.25 THz terahertz characteristic peaks can be used for qualitative analysis and quantitative detection of sodium hypochlorite residues in chicken, and in the scheme of the embodiment, the detection limit of the sodium hypochlorite soaking solution concentration is 200 mg / L, and the residual amount of sodium hypochlorite is 0.1716 mg / g.

[0058] (ii) Sodium thiosulfate titration test

[0059] The frozen chicken breast was prepared into 2x2x1 cm uniform slices, and after complete thawing, the surface moisture was wiped dry with a water absorption paper and weighed. The effective chlorine concentration of the sodium hypochlorite solution used in the experiment was measured by the sodium thiosulfate titration method, and the sodium hypochlorite standard solution was diluted by 0, 5, 10, 15 and 20 times, respectively, to obtain the effective chlorine concentration of 41.18, 8.236, 4.118, 2.745 and 2.059 g / L, and the chicken breast slices were soaked in the sodium hypochlorite solution, and the number of chicken breast slices in each group was 5. After soaking for 20 min, the chicken breast was taken out and placed in a test tube containing 4 mL of distilled water, and after homogenization, it was left to stand for 10 min, and 1 mL of the upper clear liquid was taken for sodium thiosulfate titration. The effective chlorine residual concentration in each group of chicken is shown in Table 3.

[0060] Table 3 Effective chlorine residual concentration in each group of chicken

[0061]

[0062] The linear relationship curve of the effective chlorine residual concentration in chicken and the soaking concentration is shown in Figure 6 . It can be seen from Figure 6 that the effective chlorine residual concentration and the soaking concentration show a good linear relationship, and the linear curve is Y=0.006X+0.0815, R 2 =0.977, X=2.745-41.48 g / L.

[0063] Therefore, the above experiment can illustrate that when the frequency of the sodium hypochlorite characteristic peak is 1.10 THz, the mass content of sodium hypochlorite in chicken and the peak height of the sodium hypochlorite characteristic peak show a linear relationship; when the frequency of the sodium hypochlorite characteristic peak is 1.25 THz, the mass content of sodium hypochlorite in chicken and the peak height of the sodium hypochlorite characteristic peak show a third-order polynomial fitting relationship.

[0064] The above only describes the preferred embodiments of the present application, and it should be noted that for those skilled in the art, without departing from the principles of the present application, a number of improvements and refinements can be made, and these improvements and refinements should also be considered as the protection scope of the present application.

Claims

1. A method for detecting the content of sodium hypochlorite in chicken, comprising the following steps: (1) performing terahertz spectrum test on a dried chicken sample to obtain the peak height of a sodium hypochlorite characteristic peak; (2) obtaining the content of sodium hypochlorite in the chicken according to a predetermined standard curve and the peak height of the sodium hypochlorite characteristic peak in step (1); the frequency of the sodium hypochlorite characteristic peak is 1.10 THz or 1.25 THz; the standard curve is a fitting curve of the mass content of sodium hypochlorite in the chicken and the peak height of the sodium hypochlorite characteristic peak; the measurement mode of the terahertz spectrum test is a spectral line mode, the sample bin is a transmission module, the average number is 1, the sample thickness is 1 mm, and the scanning range is 50*50 mm.

2. The detection method according to claim 1, characterized in that, When the frequency of the sodium hypochlorite characteristic peak is 1.25 THz, the fitting curve is a linear relationship fitting curve.

3. The method of claim 1, wherein, When the frequency of the sodium hypochlorite characteristic peak is 1.10 THz, the fitting curve is a third-order polynomial fitting curve.

4. The method of claim 1, wherein, The preparation method of the dried chicken sample, comprising the following steps: drying chicken slices to obtain a dried chicken sample; the drying temperature is 43-47℃, and the time is 2-2.5 h.

5. The detection method according to claim 4, characterized in that, The size of the chicken slices is 2±0.1 cm in length, 2±0.1 cm in width, and 0.1 cm in thickness.

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