Determination of sodium alginate content as thickener in food

Abstract

The present invention provides a method for determining the content of sodium alginate, a thickener, in food, comprising: S1, crushing bird's nest, diluting with water, filtering, and using the filtrate as a test sample; S2, subjecting the test sample to high-performance liquid chromatography-evaporative light scattering detector / differential refractive index detection analysis, and determining whether the test sample contains sodium alginate by comparing the spectra of the test sample with those of a standard substance. The present invention employs a sample pretreatment method using water dissolution and dilution, and uses a C18 chromatographic column for chromatographic separation and an evaporative light scattering detector to detect the content of sodium alginate, a thickener, in instant bird's nests. This method effectively reduces the influence of mannuronic acid on the test results, and can complete the analysis of the content of sodium alginate, a thickener, in instant bird's nests within 4 minutes.

Description

Technical Field

[0001] The invention relates to a method for determining the content of sodium alginate, a thickener, in food. Background Art

[0002] Bird's nests are nests built by the saliva secreted by swiftlets during the breeding season, or by the condensation of saliva and feathers. Bird's nests have long been considered a health food and medicine, nourishing the skin and moistening the lungs. Used both as food and medicine, bird's nests are rich in protein, amino acids, sialic acid, and inorganic elements. Research has shown that bird's nests have antioxidant, immune-enhancing, anti-aging, antiviral, blood clotting inhibitory, and intestinal flora regulation benefits.

[0003] Sodium alginate is a polysaccharide biopolymer extracted from brown algae, composed of α-1-guluronic acid and β-d-mannuronic acid. It is non-toxic, hydrophilic, soluble, and thickening. Current methods for detecting sodium alginate include mass spectrometry, calcium acetate analysis, copper reagent colorimetric spectrophotometry, and Fourier transform infrared spectroscopy. These methods primarily assess purity through a colorimetric reaction with mannuronic acid in sodium alginate. These methods involve numerous reagents, complex procedures, and long processing times. To improve taste and increase consistency, vendors add sodium alginate as a thickener to instant bird's nests. However, because bird's nests themselves contain mannuronic acid, it is currently impossible to determine the content of this thickener in instant bird's nests.

[0004] Therefore, it is a technical problem that those skilled in the art need to solve urgently to develop a method for detecting the content of sodium alginate, a thickener in instant bird's nests, which is simple to operate, fast, accurate, reproducible and low in cost. Summary of the Invention

[0005] The present invention provides a method for determining the content of sodium alginate, a thickener, in food, which can effectively solve the above problems.

[0006] The present invention is achieved in that:

[0007] The present invention provides a method for determining the content of sodium alginate, a thickener, in food, comprising:

[0008] S1, crush the bird's nest, dilute to volume with water, filter, and use the filtrate as the sample to be tested;

[0009] S2. Performing high performance liquid chromatography-evaporative light scattering detector / differential refractive index detector detection and analysis on the sample to be tested, and determining whether the sample to be tested contains sodium alginate by comparing the spectra of the sample to be tested with those of the standard substance.

[0010] As a further improvement, the method further comprises:

[0011] A standard quantitative curve is drawn and the sodium alginate content in the bird's nest is calculated based on the standard quantitative curve.

[0012] As a further improvement, the steps of adjusting the volume with water, filtering, and using the filtrate as the sample to be tested include:

[0013] The mixture was shaken and diluted with water to volume, and passed through a 0.22 μm aqueous filter membrane to obtain the filtrate as the sample to be tested.

[0014] As a further improvement, the liquid chromatography conditions are: hydrophilic C18 chromatographic column; mobile phase A is acetonitrile, and mobile phase B is first-grade water.

[0015] As a further improvement, the ratio of mobile phase A to mobile phase B is 20:80; the flow rate is 1.0 mL / min; and the column temperature is 40°C.

[0016] As a further improvement, the detector conditions include evaporation temperature: 60° C., atomization temperature: 60° C., evaporation gas volume: 1.65 SLM, and LED lamp intensity: 100%.

[0017] The present invention further provides a method for determining the content of sodium alginate, a thickener, in food, comprising:

[0018] S1, crush the gel food, dilute to volume with water, filter, and use the filtrate as the sample to be tested;

[0019] S2. Performing high performance liquid chromatography-evaporative light scattering detector / differential refractive index detector detection and analysis on the sample to be tested, and determining whether the sample to be tested contains sodium alginate by comparing the spectra of the sample to be tested with those of the standard substance.

[0020] The beneficial effects of the present invention are as follows: the present invention adopts a sample pretreatment method of dissolving and fixing the volume with water, and uses a C18 chromatographic column for chromatographic separation and an evaporative light scattering detector or a differential refractometer to detect the content of the thickener sodium alginate in the instant bird's nest, which can effectively reduce the influence of mannuronic acid in the bird's nest on the test results, and the analysis of the content of the thickener sodium alginate in the instant bird's nest can be completed within 4 minutes. And the linearity is good in the concentration range of 0.60-1.40 mg / mL, and the precision and accuracy meet the analysis requirements. The determination method disclosed by the present invention is simple and fast to operate, highly accurate, sensitive and reproducible, and is suitable for the rapid detection of the thickener sodium alginate content in instant bird's nest. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0022] Figure 1 It is a standard curve diagram of sodium alginate concentration and peak area of the present invention.

[0023] Figure 2 Chromatogram of the instant bird's nest sample without added sodium alginate of the present invention.

[0024] Figure 3 、 Figure 4 It is the spectrum of the sodium alginate standard solution of the present invention.

[0025] Figure 5 、 Figure 6 It is a chromatogram of the instant bird's nest sample of the present invention when sodium alginate is added.

[0026] Figure 7 This is the sodium alginate chromatogram of the amino chromatographic column of the present invention.

[0027] Figure 8 This is the sodium alginate chromatogram of the strong cation chromatographic column of the present invention.

[0028] Figure 9 This is the chromatogram of sodium alginate on a phenyl column of the present invention.

[0029] Figure 10 It is the chromatogram of the hydrophilic C18 column sodium alginate of the present invention.

[0030] Figure 11 The chromatogram of the hydrophilic C18 column sodium alginate on a differential refractive index detector of the present invention is shown. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the invention for which protection is sought, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0032] The present invention provides a method for determining the content of sodium alginate, a thickener, in food, comprising:

[0033] S1, crush the bird's nest, dilute to volume with water, filter, and use the filtrate as the sample to be tested;

[0034] S2. Performing high performance liquid chromatography-evaporative light scattering detector / differential refractive index detector detection and analysis on the sample to be tested, and determining whether the sample to be tested contains sodium alginate by comparing the spectra of the sample to be tested with those of the standard substance.

[0035] In step S1, as a further improvement, the steps of adjusting the volume with water, filtering, and using the filtrate as the sample to be tested include:

[0036] Shake well and dilute to volume with water. Pass the filtrate through a 0.22 μm aqueous filter membrane to obtain the filtrate as the sample to be tested. Filtration prevents excessive particles from clogging the chromatographic column.

[0037] In step S2, as a further improvement, during the implementation of the liquid chromatography condition optimization, the separation effects of amino column, strong cation column, phenyl column and hydrophilic C18 column on sodium alginate were investigated respectively. The analytical chromatograms of sodium alginate by different chromatographic columns are shown in FIG. Figure 7-10 , the results show that Figure 7-Figure 9 , the peak shape is poor and the response value is low; Figure 10 The peak shape, response value and separation are relatively good, so the final chromatographic column is: hydrophilic C18 chromatographic column.

[0038] As a further improvement, during the implementation of the liquid chromatography conditions optimization, for the mobile phase, this method determines that mobile phase A is acetonitrile and mobile phase B is first-grade water, and the mobile phase ratios are investigated respectively, and the on-machine determination is carried out according to the ratios of V(A):V(B)=10:90, V(A):V(B)=20:80, V(A):V(B)=30:70, and V(A):V(B)=40:60; because the peak time has a certain influence on the result accuracy of the test sample, after test analysis, when the ratio of mobile phase acetonitrile to water V(A):V(B) is 20:80, the retention time of the sample chromatographic peak is stable, the separation is best, and the peak shape is sharp, so the mobile phase V(A):V(B)=20:80 is finally determined.

[0039] As a further improvement, the optimal liquid chromatography conditions were: a hydrophilic C18 column; mobile phase A: acetonitrile; mobile phase B: first-grade water; a ratio of mobile phase A to mobile phase B of 20:80; a flow rate of 1.0 mL / min; a column temperature of 40°C; and an injection volume of 5 μL. Experiments demonstrated that this column provided excellent separation of sodium alginate, thus preventing the impact of mannuronic acid in bird's nest on the detection of sodium alginate. Other control experiments revealed that other types of columns and mobile phases were unable to effectively separate sodium alginate and mannuronic acid.

[0040] As a further improvement, the detector conditions include evaporation temperature: 60° C., atomization temperature: 60° C., evaporation gas volume: 1.65 SLM, and LED lamp intensity: 100%.

[0041] As a further improvement, the method may further include:

[0042] S3, drawing a standard quantitative curve and calculating the sodium alginate content in the bird's nest according to the standard quantitative curve.

[0043] The above detection method is not limited to the detection of sodium alginate gel adulteration in instant bird's nests, but can also be used for some gel foods, such as shark fin, peach gum, pectin, ice jelly and other foods.

[0044] The present invention further provides a method for determining the content of sodium alginate, a thickener, in food, comprising:

[0045] S1, crush the gel food, dilute to volume with water, filter, and use the filtrate as the sample to be tested;

[0046] S2. Performing high performance liquid chromatography-evaporative light scattering detector / differential refractive index detector detection and analysis on the sample to be tested, and determining whether the sample to be tested contains sodium alginate by comparing the spectra of the sample to be tested with those of the standard substance.

[0047] The detection method is basically the same as the detection method for sodium alginate gel adulteration in instant bird's nest, and will not be repeated here.

[0048] Example 1

[0049] a. Sample pretreatment, including the following steps:

[0050] (1) Weigh 1 g of sample, dilute to 25 mL with water, filter through a 0.22 μm filter membrane, and the filtrate is the sample to be tested;

[0051] b. Preparation of the standard song, including the following steps:

[0052] (1) Accurately pipette 0.60, 0.80, 1.00, 1.20, and 1.40 mL of 10 mg / mL sodium alginate standard stock solution into a 10 mL volumetric flask, add water to the mark, and prepare sodium alginate standard solutions with concentrations of 0.60, 0.80, 1.00, 1.20, and 1.40 mg / mL. Take 5 μL of the sample and plot the peak area-concentration of sodium alginate to obtain the regression equation of the standard curve. The results are shown in the figure. Figure 1 .

[0053] In order to further demonstrate the beneficial effects of the present invention and to better understand the present invention, the properties and application performance of the high performance liquid chromatography-evaporative light scattering detector determination method of the sodium alginate thickener in the instant bird's nest of the present invention are further illustrated by the following determination tests. However, it should not be understood as a limitation of the present invention. The properties of the methods obtained by other determination experiments conducted by those skilled in the art based on the above invention content and the applications based on the above properties are also considered to fall within the scope of protection of the present invention.

[0054] The method of the present invention is used to detect the content of sodium alginate, a thickener in instant bird's nest

[0055] 1. Instruments and reagents

[0056] Instruments: Agilent 1260 high performance liquid chromatograph with evaporative light scattering detector (ELSD) (Agilent, USA); electronic balance (Mettler-Toledo).

[0057] Reagents: sodium alginate standard (Xinyang Zhongjian Metrology Biotechnology Co., Ltd.); acetonitrile (chromatographic grade, Anhui Tiandi High Purity Solvent Co., Ltd.); methanol (chromatographic grade, Anhui Tiandi High Purity Solvent Co., Ltd.); ultrapure water.

[0058] 2. Standard reagents

[0059] Accurately weigh 0.5000 g of sodium alginate standard and place it in a 50 mL volumetric flask. Add water to the volume to prepare a 10 mg / mL standard stock solution. Add 0.60, 0.80, 1.00, 1.20, and 1.40 mL of the standard stock solution to a 10 mL volumetric flask, respectively, and add water to the mark to prepare sodium alginate standard solutions with concentrations of 0.60, 0.80, 1.00, 1.20, and 1.40 mg / mL.

[0060] 3. Instrument analysis conditions

[0061] a. Liquid chromatography conditions

[0062] Chromatographic column: hydrophilic C18 column; mobile phase A is acetonitrile, mobile phase B is first-grade water, the ratio is 20:80; flow rate is 1.0 mL / min; column temperature is 40°C; injection volume is 5 μL.

[0063] b. Detector conditions

[0064] 4. Sample processing

[0065] Weigh 1 g of sample, dilute to 25 mL with water, filter through a 0.22 μm filter membrane, and the filtrate is the sample to be tested.

[0066] 5. Results and Discussion

[0067] (1) Linear range and correlation coefficient

[0068] Under the set experimental conditions, sodium alginate: 0.60-1.40 mg / mL. Take 5 μL of sample, use the peak area-concentration of sodium alginate to plot, get the standard curve regression equation, record the spectrum to get the linear equation and correlation coefficient, the linear regression equation is shown in Figure 1 The linear correlation coefficient was greater than 0.999. The instrument limit of detection (LOD) and limit of quantification (LOQ) were determined using a serial dilution method with standard solutions. The target concentrations corresponding to signal-to-noise ratios (S / N) ≥ 3 and S / N ≥ 10 were used as the instrument limit of detection and limit of quantification, respectively. Based on a 1 g sample weight and a 25 mL volume, the limit of detection was 1.25 g / kg and the limit of quantification was 3.75 g / kg. Figure 3 and 4 This is the standard spectrum of sodium alginate.

[0069] (2) Precision and accuracy of the method

[0070] Six consecutive injections of a 1 mg / mL sodium alginate standard solution were performed, and the peak area response was used as the evaluation standard. The relative standard deviation (RSD) was calculated to be 1.23%. Appropriate amounts of the 10 mg / mL standard solution were added to instant bird's nest samples for sample preparation. The accuracy and precision of the method were investigated through spike-recovery experiments (n=6). The results of the spike-recovery experiments are shown in Table 1. The results showed that the average spiked recoveries of sodium alginate ranged from 100.5% to 102.2%, with relative standard deviations (RSDs) ranging from 1.4% to 2.1%.

[0071] Table 1 Recovery rate and relative standard deviation of sodium alginate in instant bird's nest (n=6)

[0072]

[0073] (3) Ready-to-eat bird's nest sample testing

[0074] Five batches of instant bird's nests were tested, with six parallel samples in each batch. Figure 2 、 Figure 5 and Figure 6 , the spectrum obtained under the same conditions as the standard Figure 3-4 By comparison, it can be seen that some instant bird's nest samples contain sodium alginate. According to the established standard curve, the content of sodium alginate thickener was calculated. The results are shown in Table 2. The relative standard deviation is between 0.42% and 5.05%. There are differences in the sodium alginate thickeners of various instant bird's nests.

[0075] Table 2 Sodium alginate content in 5 batches of instant bird's nests (n=6)

[0076]

[0077] The present invention uses a pretreatment method involving water dissolution and volume fixation to analyze different types of instant bird's nests. The entire experimental method is simple to operate, rapid and efficient, accurate, sensitive, and reproducible, making it suitable for rapid analysis of the thickening agent sodium alginate in instant bird's nests.

[0078] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for determining the content of sodium alginate as a thickener in food, characterized in that: include: S1, crush the bird's nest, dilute to volume with water, filter, and use the filtrate as the sample to be tested; S2. Perform high performance liquid chromatography-evaporative light scattering detector / differential refractive index detector (DRD) detection and analysis on the sample to be tested. By comparing the spectra of the sample to be tested with those of the standard substance, determine whether the sample to be tested contains sodium alginate. The liquid chromatography conditions are as follows: a hydrophilic C18 column; mobile phase A is acetonitrile, mobile phase B is first-grade water; and the ratio of mobile phase A to mobile phase B is 20:

80.

2. The method for determining the content of sodium alginate as a thickener in food according to claim 1, wherein: Further including: A standard quantitative curve was drawn and the sodium alginate content in the bird's nest was calculated based on the standard quantitative curve.

3. The method for determining the content of sodium alginate as a thickener in food according to claim 1, wherein: The steps of adjusting the volume with water, filtering, and using the filtrate as the sample to be tested include: The mixture was shaken and diluted to volume with water, and the filtrate was passed through a 0.22 μm aqueous filter membrane to obtain the filtrate as the sample to be tested.

4. The method for determining the content of sodium alginate as a thickener in food according to claim 1, wherein: The flow rate was 1.0 mL / min and the column temperature was 40 °C.

5. The method for determining the content of sodium alginate as a thickener in food according to claim 1, wherein: The detector conditions include evaporation temperature: 60 °C, atomization temperature: 60 °C, evaporation gas volume: 1.65 SLM, LED light intensity: 100%.

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