Method for measuring pectin content in polysaccharide mixed solution
By using fluorescence detection method with specific excitation wavelength and emission wavelength in polysaccharide solution, the problem of accuracy in detecting pectin content in polysaccharide solution was solved, safe and low-cost pectin quantification was achieved, and the gain effect of plant polysaccharide additives was ensured.
Patent Information
- Application Number
- CN202510957136.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-11
- Publication Date
- 2025-09-09
AI Technical Summary
Existing technologies are unable to accurately distinguish and quantitatively detect the pectin content in polysaccharide solutions, resulting in the inability to control the negative effects of pectin, affecting the gain effect of plant polysaccharide additives. Traditional detection methods require high temperature and strong acid, which is costly and unsafe.
A fluorescence response value standard curve of pectin was constructed using specific excitation wavelengths and emission wavelengths, and the pectin content in the polysaccharide mixed solution was detected by fluorescence detection at 280-285 nm, avoiding high temperature and strong acid treatment.
The accurate quantitative detection of pectin and other polysaccharides is achieved with simple, safe, low-cost operation and accurate results, which can effectively avoid the negative impact of pectin on the sensory quality of cigarettes.
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Abstract
Description
Technical Field
[0001] The invention belongs to the field of pectin, and particularly relates to a method for measuring pectin content in a polysaccharide mixed solution. Background Art
[0002] Plant polysaccharides, as a natural additive, have been widely studied and applied in the field of cigarette flavoring in recent years. Studies have shown that the addition of plant polysaccharides can significantly contribute to the sensory quality of cigarettes by improving the sweetness of smoke, reducing irritation, and enhancing the richness of aroma [Zhang Haonan, Jin Guiyong, Xi Gaolei, et al. Research and application of purification, moisture preservation and thermal cracking products of Asarum polysaccharide [J]. Journal of Henan Agricultural University, 2022, 56(3): 451-459]. However, plant polysaccharides are not a single component and are usually composed of two types of components: neutral polysaccharides and pectin. Further research revealed significant differences between neutral polysaccharides and pectin in their effects on the sensory quality of cigarettes: neutral polysaccharides effectively improve smoke softness and enhance sweetness and aroma, while pectin undergoes high-temperature decomposition during cigarette combustion to produce small molecules such as aldehydes and acids, which lead to increased smoke odor, an astringent aftertaste, and even a pungent aftertaste [Guo Song. Distribution Characteristics of Pectin and Cellulose Content in Flue-cured Tobacco Leaves in my country and Their Impact on Smoking Quality [D]. Henan Agricultural University, 2011]. Therefore, the sensory enhancement effects of plant polysaccharides are highly dependent on the purity and composition of their components, particularly the precise control of pectin content.
[0003] Currently, the application research of plant polysaccharides in the cigarette industry focuses on the macro-correlation between total polysaccharide content and sensory effects, while there is a lack of systematic analysis of the negative impact of pectin. Traditional polysaccharide detection technologies (such as the phenol-sulfuric acid method and the DNS colorimetric method) can only determine the total sugar content and cannot distinguish the component proportions of neutral polysaccharides and pectin, which may lead to the following problems in practical applications: 1) Although the plant polysaccharide solution with excessive pectin meets the total sugar content standard, the negative sensory effect offsets the gain effect of neutral polysaccharides; 2) The proportion of pectin in plant polysaccharides from different sources or extraction processes varies significantly, and directly citing existing process parameters can easily lead to fluctuations in the sensory quality of the product; 3) The lack of a pectin content detection method limits the optimization of the screening criteria for polysaccharide raw materials, making it difficult to achieve precise process control. Therefore, the development of a specific detection method for pectin content in plant polysaccharide solutions is of great significance to the research and development of cigarette additives. By screening high-purity neutral polysaccharide raw materials based on quantitative pectin content, the sensory deterioration effect of pectin can be avoided, the stability of the gain-enhancing effect of plant polysaccharide additives can be ensured, key quality indicators can be provided for the optimization of polysaccharide extraction processes (such as pectin removal treatment), and the efficient preparation of functional polysaccharides can be promoted. This can fill the gap in the field of cigarette additives for the refined analysis of polysaccharide components and lay the foundation for establishing a standardized evaluation system for the sensory contribution of plant polysaccharides.
[0004] The existing methods for detecting pectin in polysaccharide mixed solutions are basically chromatography, such as ion chromatography, liquid chromatography, and gas chromatography. These chromatography methods require the polysaccharides in the sample to be hydrolyzed into monosaccharides under the synergistic conditions of high temperature and strong acid, and then the pectin content in the sample is deduced based on the content of galacturonic acid after acid hydrolysis. For example, the literature [Rao Wei, Tuo Suxing, Zhong Kejun, et al. Determination of pectin in tobacco by enzymatic hydrolysis-ion chromatography [J]. Chemical Research, 2010, 21(3):3] uses ion chromatography to quantitatively detect pectin in tobacco. However, the chromatographic detection of pectin requires high heat, strong acid (generally using highly corrosive concentrated sulfuric acid) and expensive instruments and equipment (chromatograph), which is not conducive to detection. Therefore, it is necessary to develop a green, convenient and low-cost detection method.
[0005] Carbazole sulfuric acid colorimetry is a method for detecting pectin other than chromatography. Its pretreatment method is similar to chromatography, and both require high-temperature acid hydrolysis. The difference is that after using carbazole to color galacturonic acid, the absorbance value is detected at 530nm. Its detection speed and detection cost are better than chromatography. The literature [Liu Enfen, Peng Lijuan, Xie Zhiqiang, et al. Research on the analysis method of pectin content in tobacco stem extract of papermaking reconstituted tobacco raw materials [J]. Paper and Papermaking, 2020, 39(6):3.] shows that carbazole sulfuric acid colorimetry is also suitable for detecting pectin in tobacco products and is a good alternative to ion chromatography. However, carbazole sulfuric acid colorimetry still requires the use of unsafe detection conditions such as high heat and strong acid, which is not conducive to detection. In addition, the calculation of pectin content by galacturonic acid ignores the presence of other monosaccharides in the pectin side chain, which may lead to low detection values.
[0006] Therefore, the art continues to seek a green, safe, convenient and low-cost method for quantitatively detecting pectin in a polysaccharide mixed solution. Summary of the Invention
[0007] In response to the problems existing in the above-mentioned prior art, the present invention provides a method for quantitatively detecting the pectin content in a polysaccharide mixed solution. This method constructs a pectin concentration-fluorescence response value standard curve by selecting a specific excitation wavelength, thereby accurately detecting the pectin content in the polysaccharide mixed solution. Moreover, this method is green, safe, easy to operate, and low-cost. It can avoid the defects of existing detection methods and has broad application prospects.
[0008] Specifically, the present invention provides a method for detecting the pectin content in a polysaccharide mixed solution, which comprises:
[0009] (1) establishing a standard curve of the concentration C of the pectin aqueous solution and the fluorescence response value A, wherein the fluorescence response value A is the fluorescence response value of the pectin aqueous solution under the conditions of an excitation wavelength of 280 to 285 nm and an emission wavelength of 463 ± 5 nm;
[0010] (2) obtaining the fluorescence response value A1 of the polysaccharide mixed solution to be tested under the conditions of an excitation wavelength of 280 to 285 nm and an emission wavelength of 463 ± 5 nm;
[0011] (3) Substituting the fluorescence response value A1 of the polysaccharide mixed solution to be tested into the standard curve of the concentration C and the fluorescence response value A to obtain the concentration of pectin in the polysaccharide mixed solution to be tested;
[0012] (4) Based on the concentration of pectin in the polysaccharide mixed solution to be tested, the pectin content in the polysaccharide mixed solution to be tested is calculated.
[0013] In some embodiments, in step (1), the fluorescence response value A is the fluorescence response value of the pectin aqueous solution under the conditions of an excitation wavelength of 285 nm and an emission wavelength of 463±5 nm;
[0014] Furthermore, step (2) includes: obtaining a fluorescence response value A1 of the polysaccharide mixed solution to be tested under the conditions of an excitation wavelength of 285 nm and an emission wavelength of 463±5 nm.
[0015] In some embodiments, in step (1), the fluorescence response value A is the fluorescence response value of the pectin aqueous solution under the conditions of an excitation wavelength of 285 nm and an emission wavelength of 463 nm;
[0016] Furthermore, step (2) includes: obtaining a fluorescence response value A1 of the polysaccharide mixed solution to be tested under the conditions of an excitation wavelength of 285 nm and an emission wavelength of 463 nm.
[0017] In some embodiments, the standard curve is y=1608056x+101919(R 2 =1), where x represents the pectin concentration (in mg / mL), the concentration range of x is between 0 and 1 mg / mL, and y represents the fluorescence response value.
[0018] In some embodiments, the polysaccharide mixed solution comprises pectin.
[0019] In some embodiments, the polysaccharide mixed solution further comprises one or more selected from starch, sodium carboxymethyl cellulose, and xylan.
[0020] In some embodiments, the polysaccharide mixture is an artificially prepared polysaccharide mixture, or a naturally extracted plant polysaccharide mixture.
[0021] In some embodiments, the plant is tobacco (such as flue-cured tobacco), citrus, astragalus, or dendrobium.
[0022] In some embodiments, the naturally extracted plant polysaccharide mixture is obtained by the following method: mixing plant powder with water at a solid-liquid ratio of 1:15 to 1:30 (g / mL), performing a water extraction and alcohol precipitation step, and collecting the precipitate; freeze-drying the precipitate and then adding water to obtain the plant polysaccharide mixture. In some embodiments, the water extraction is carried out at a temperature of 80 to 100°C (preferably 90°C). In some embodiments, the water extraction time is 1 to 5 hours (preferably 2 or 4 hours). It is well known to those skilled in the art that the water extraction and alcohol precipitation step includes: adding water to the mixture for water extraction; centrifuging the water extract and collecting the supernatant; and subjecting the supernatant to alcohol precipitation and collecting the precipitate. In some embodiments, during the alcohol precipitation, the ratio of the volume of added ethanol to the volume of the supernatant is (3 to 10):1, preferably 4:1 or 9:1. In some embodiments, the supernatant is pre-concentrated before the alcohol precipitation, for example, to 1 / 2 to 1 / 5 of its original volume, preferably 1 / 5.
[0023] In some embodiments, when the plant is tobacco leaves (such as flue-cured tobacco), the polysaccharide mixed solution is obtained by the following method: grinding the flue-cured tobacco into powder, passing through a 40-mesh sieve, adding deionized water at a solid-liquid ratio of 1:15 (g / mL), extracting at 90°C for 4 hours, centrifuging at 4000 r / min for 10 minutes, collecting the supernatant, taking 1 part of the supernatant and adding 9 parts of anhydrous ethanol, precipitating at 4°C overnight, centrifuging at 10000 r / min and 4°C for 10 minutes, collecting the precipitate, and freeze-drying to obtain a crude polysaccharide mainly composed of pectin; adding water to the crude polysaccharide to prepare a polysaccharide mixed solution.
[0024] In some embodiments, when the plant is citrus, astragalus or dendrobium, the polysaccharide mixed solution is obtained by the following method: citrus peel, astragalus or dendrobium are dried and crushed respectively, and then passed through a 60-mesh sieve; water is added at a solid-liquid ratio of 1:30 (g / mL), extracted in a 90°C water bath for 2 hours, and the supernatant is taken after centrifugation; concentrated to 1 / 5 of the original volume, 4 times the volume of anhydrous ethanol is added, and the mixture is allowed to stand at 4°C for 12 hours, and the precipitate is collected by centrifugation; the precipitate is freeze-dried to obtain a crude polysaccharide powder; and the crude polysaccharide powder is added with water to form a polysaccharide mixed solution.
[0025] Beneficial effects
[0026] 1. The method of the present invention can distinguish pectin from other polysaccharides through a specific fluorescence response, thereby achieving quantitative detection of pectin in a mixed polysaccharide solution, and its spiked recovery rate is good;
[0027] 2. The method of the present invention does not require the use of high temperature, strong acid, or other treatments, nor does it require a color developer. It is simple to operate, has accurate results, and has high application value.
[0028] 3. Compared with the carbazole sulfuric acid colorimetric method, the method of the present invention has a better pectin detection rate for the extracted pectin and is more practical. BRIEF DESCRIPTION OF THE DRAWINGS
[0029] Figure 1 is the UV-visible absorption spectrum of different polysaccharides;
[0030] Figure 2 is the fluorescence spectra of different polysaccharides at an excitation wavelength of 285 nm;
[0031] Figure 3 is the fluorescence spectra of different polysaccharides at an excitation wavelength of 250 nm;
[0032] Figure 4 is the fluorescence spectra of different polysaccharides at an excitation wavelength of 265 nm;
[0033] Figure 5 is the fluorescence spectrum of different polysaccharides at an excitation wavelength of 280 nm;
[0034] Figure 6 is the fluorescence spectra of different polysaccharides at an excitation wavelength of 290 nm;
[0035] Figure 7 This is the pectin standard curve. DETAILED DESCRIPTION
[0036] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings and examples, but it will be understood by those skilled in the art that the following drawings and examples are intended only to illustrate the present invention and are not intended to limit the scope of the invention. Various objects and advantages of the present invention will become apparent to those skilled in the art based on the following detailed description of the accompanying drawings and preferred embodiments.
[0037] Example 1: Differences in fluorescence spectra between pectin and other polysaccharides
[0038] To prepare the polysaccharide solution, weigh 0.1 g of each of soluble starch (Sinopharm Group, Catalog No. 10021318), sodium carboxymethyl cellulose (CMC-Na, Aladdin, Catalog No. C104985), xylan (Shanghai Yuanye, Catalog No. S25874-25 g), and pectin (Sigma, Catalog No. P9135) in 100 mL of deionized water. Dissolve under magnetic stirring at room temperature and set aside. The final concentration of each polysaccharide solution is 1 mg / mL.
[0039] Take 200 μL of polysaccharide solution and place it in the UV enzyme plate. Scan the whole wavelength with the enzyme reader in the range of 230-600 nm. The results are as follows: Figure 1 As shown. Figure 1It can be seen that pectin has a high absorbance value in the 230-450nm band, among which there is an obvious absorption peak at 285nm. With 285nm as the excitation wavelength, fluorescence scanning is performed, and the results are as follows Figure 2 As shown. Figure 2 It can be seen that pectin has fluorescence response peaks at 355 nm and 463 nm, respectively. Since other polysaccharide solutions also have high fluorescence response values at 355 nm, 463 nm was selected as the characteristic fluorescence response peak of pectin.
[0040] It is well known to those skilled in the art that changes in the excitation wavelength generally do not affect the emission wavelength. However, in this application, the inventors selected 285 nm to verify whether 285 nm is the most suitable excitation wavelength. Figure 1 In the UV-visible absorption spectrum of the pectin sample, 250 nm, which has the same absorbance as 285 nm, was used as the comparison wavelength for fluorescence scanning. The results are as follows: Figure 3 As shown. Figure 3 It can be seen that, surprisingly, all polysaccharides have a fluorescence response peak at 322 nm, and pectin cannot be distinguished from other polysaccharides at this time.
[0041] In addition, by Figure 1 It can be seen that there is a trough in the UV-visible absorption spectrum of the pectin sample, namely 265nm. Taking this wavelength as the excitation wavelength, the above four polysaccharide solutions were subjected to fluorescence scanning. Figure 4 It can be seen that, unfortunately, all polysaccharides have a fluorescence response peak at 324 nm under this excitation wavelength, making it impossible to distinguish pectin from other polysaccharides.
[0042] In addition, in order to broaden the selection range of excitation wavelengths, the inventors also tried to select wavelengths near 285nm (280nm, 290nm) as excitation wavelengths. Figure 5 It can be seen that under the excitation wavelength of 280nm, pectin has a response peak at 538nm, but its fluorescence response peak value of 519765 is not as good as the fluorescence response peak value of the aforementioned (excitation wavelength 285nm, emission wavelength 463nm, fluorescence response value 1653068), which is less than one-third of it. Figure 6 It can be seen that at an excitation wavelength of 290 nm, all polysaccharides cannot produce peaks in the fluorescence scanning spectrum, and this wavelength cannot meet the detection requirements.
[0043] In summary, the present application unexpectedly found that fluorescence scanning using an excitation wavelength of 280-285 nm can distinguish pectin from other polysaccharides. If quantitative detection is required, 285 nm is preferably used as the excitation wavelength and 463 nm as the emission wavelength.
[0044] Example 2: Plotting of pectin standard curve and calculation of spiked recovery
[0045] The 1 mg / mL pectin solution in Example 1 was diluted to 0.2, 0.4, 0.6, and 0.8 mg / mL, and fluorescence detection was performed with an excitation wavelength of 285 nm and an emission wavelength of 463 nm. A standard curve was drawn based on the fluorescence response value and the pectin concentration. The results are shown in FIG. Figure 7 As shown. Figure 7 It can be seen that the linear equation is y=1608056x+101919(R 2 =1). It is obvious that the above standard curve has excellent linearity and high reliability.
[0046] Spike recovery test: 1 mL and 1 mg / mL standard solutions of soluble starch, sodium carboxymethyl cellulose (CMC-Na), xylan, and pectin were taken, respectively, and then mixed to form a polysaccharide mixture (pectin content 0.25 mg / mL). After adding 0.5 mL of the polysaccharide mixture to each of four 2 mL centrifuge tubes, 0.5 mL of deionized water was added to the first centrifuge tube. The second centrifuge tube was then added with 0.5 mL of a 0.125 mg / mL pectin solution (diluted 8-fold from the 1 mg / mL pectin standard solution), marking this as a 0.5-fold spike. The third centrifuge tube was then added with 0.5 mL of a 0.25 mg / mL pectin solution (diluted 4-fold from the 1 mg / mL pectin standard solution), marking this as a 1-fold spike. The fourth centrifuge tube was then added with 0.5 mL of a 0.5 mg / mL pectin solution (diluted 2-fold from the 1 mg / mL pectin standard solution), marking this as a 2-fold spike. After spike addition, 200 μL of the liquid in the centrifuge tube was taken and the fluorescence value was detected in a fluorescence enzyme plate (excitation wavelength 285 nm, emission wavelength 463 nm). After detection, the concentration was converted according to the standard curve. The spike recovery rate = (sample concentration after spike addition - sample concentration before spike addition) / spike concentration * 100%. The test results are shown in Table 1. The spike recovery rates of all samples were between 90% and 110%, indicating that the method of the present invention can accurately quantify pectin in unknown solutions with little interference from impurities (other polysaccharides).
[0047] Table 1 Spiked recovery
[0048] Spiking multiple 0.5 times 1.0 times 2.0 times Spike recovery 106.52％ 104.47％ 101.71％
[0049] Example 3: Comparison of detection effects between fluorescence quantitative method and carbazole sulfuric acid colorimetry
[0050] Reference [Hou Yuting, Su Jinfang, Chen Shiyue, et al. Comparison of physicochemical properties and in vitro anti-glycation activity of hawthorn pectin extracted by different methods [J]. Modern Food Science and Technology, 2018, 34(4): 159-166] The pectin content was extracted by the heat extraction method with some modifications: the flue-cured tobacco was ground into powder, passed through a 40-mesh sieve, and deionized water was added at a solid-liquid ratio of 1:15 (g / mL). After extraction at 90°C for 4 hours, the supernatant was collected after centrifugation at 4000 r / min for 10 minutes. One part of the supernatant was added with 9 parts of anhydrous ethanol, and precipitated at 4°C overnight. The precipitate was collected by centrifugation at 10000 r / min and 4°C for 10 minutes, and then freeze-dried to obtain pectin.
[0051] Weigh 0.05 g of pectin and add 100 mL of deionized water to prepare a 0.5 mg / mL pectin solution. The pectin content was detected by fluorescence quantitative method and carbazole sulfuric acid colorimetry, respectively. The fluorescence quantitative method directly detected the pectin solution with fluorescence at an excitation wavelength of 285 nm and an emission wavelength of 463 nm. The fluorescence detection value was compared with the standard curve ( Figure 7 ) for concentration conversion; the carbazole sulfuric acid colorimetric method was consistent with that described in the reference [Hou Yuting, Su Jinfang, Chen Shiyue, et al. Comparison of physicochemical properties and in vitro anti-glycation activity of hawthorn pectin extracted by different methods [J]. Modern Food Science and Technology, 2018, 34(4): 159-166].
[0052] The pectin detection rate was calculated by dividing the detection values of the two methods by the original concentration (0.5 mg / mL) and multiplying by 100%. The carbazole sulfuric acid colorimetric method has a strong detection preference for galacturonic acid and lacks significant color development for other monosaccharides. Although pectin has galacturonic acid as its main chain, it also contains other monosaccharides such as rhamnose, galactose, and arabinose on its side chains. Therefore, as shown in Table 2, the pectin detection rate of this method is significantly low. The fluorescence quantitative method, which uses the fluorescence response value of the entire pectin for calibration, has a more realistic pectin detection rate.
[0053] Table 2 Pectin detection rate
[0054] Fluorescence quantification Carbazole sulfuric acid colorimetric method Pectin detection rate (%) 84.62±0.89 56.18±1.58
[0055] Example 4: Preparation of plant polysaccharides with different pectin contents and comparison of their effects in cigarettes
[0056] Step 1: Plant polysaccharide extraction and pectin content determination
[0057] Raw material processing: Citrus peel, Astragalus, and Dendrobium were selected as plant raw materials, dried, crushed, and passed through a 60-mesh sieve. A hot water extraction-ethanol precipitation method was used: the material-liquid ratio was 1:30 (g / mL). Extraction was carried out in a 90°C water bath for 2 hours, and the supernatant was collected after centrifugation. The solution was concentrated to 1 / 5 of the original volume, and 4 times the volume of anhydrous ethanol was added. The solution was allowed to stand at 4°C for 12 hours, and the precipitate was collected by centrifugation. The crude polysaccharide powder was obtained after freeze-drying.
[0058] Pectin content determination: fluorescence spectroscopy was used. 1 mL of polysaccharide solution (1 mg / mL) was taken, with an excitation wavelength of 285 nm and an emission wavelength of 463 nm. The fluorescence detection value was compared with the linear equation ( Figure 7 ) were used for content determination, and the pectin contents of citrus polysaccharide, astragalus polysaccharide, and dendrobium polysaccharide were found to be 38.5%, 12.3%, and 4.1%, respectively.
[0059] Step 2: Add polysaccharide solution to cigarette filter rod
[0060] Preparation of fragrance-carrying filter sticks: The three polysaccharides mentioned above were prepared into 2% aqueous solutions respectively, and the solutions were evenly sprayed onto acetate filter sticks (length 20 mm, circumference 24.3 mm) at an addition amount of 1% of the filter stick weight; the control group used pure water to treat the filter sticks without adding polysaccharides.
[0061] Cigarette sample assembly: The same batch of tobacco (flue-cured tobacco type, tar content 8 mg) was used to roll cigarettes of the same specifications (cigarette length 84 mm), and the above-mentioned filter rods were installed respectively, marked as sample A (citrus polysaccharide), sample B (astragalus polysaccharide), sample C (dendrobe polysaccharide), and control group D.
[0062] Step 3: Sensory quality evaluation
[0063] Evaluation method:
[0064] Ten smokers trained in industry standards conducted a blind evaluation and scored the smoke softness, sweetness, off-flavor, pungency, and aftertaste according to GB 5606.4-2005 (maximum 9 points). The comprehensive sensory scores were calculated and the results are shown in Table 3.
[0065] Table 3 Sensory evaluation scores of samples with different pectin contents
[0066]
[0067] Conclusion: Adding Astragalus polysaccharides and Dendrobium polysaccharides to filter rods can improve the smoke state of cigarettes, while citrus polysaccharides may have a negative impact; when the filter rod contains plant pectin, the pectin content is significantly negatively correlated with the sensory quality (Pearson correlation coefficient r = -0.96, p < 0.01). The effect of pectin in the filter rod on the sensory quality of cigarette products is not entirely negative, and it still needs to be viewed in two ways. In this example, when the pectin content is ≤5% (such as sample C), the comprehensive score is increased by 28.6% compared with the control group, and the impurities and irritation are significantly reduced; when the pectin content is ≥20% (such as sample A), the comprehensive score is lower than the control group, verifying the negative effect of pectin on the sensory quality.
[0068] It can be seen that the fluorescence detection method of the present invention can provide rapid and safe technical support for the quality grading of polysaccharide additives.
[0069] It should be understood that the invention described herein is not limited to specific methodology, experimental protocols or reagents, as these may vary. The discussion and examples provided herein are presented only to describe specific embodiments and are not intended to limit the scope of the invention, which is limited only by the claims.
Claims
1. A method for detecting pectin content in a polysaccharide mixed solution, comprising: (1) establishing a standard curve of the concentration C of the pectin aqueous solution and the fluorescence response value A, wherein the fluorescence response value A is the fluorescence response value of the pectin aqueous solution under the conditions of an excitation wavelength of 280 to 285 nm and an emission wavelength of 463 ± 5 nm; (2) obtaining the fluorescence response value A1 of the polysaccharide mixed solution to be tested under the conditions of an excitation wavelength of 280 to 285 nm and an emission wavelength of 463 ± 5 nm; (3) Substituting the fluorescence response value A1 of the polysaccharide mixed solution to be tested into the standard curve of the concentration C and the fluorescence response value A to obtain the concentration of pectin in the polysaccharide mixed solution to be tested; (4) Based on the concentration of pectin in the polysaccharide mixed solution to be tested, the pectin content in the polysaccharide mixed solution to be tested is calculated.
2. The method according to claim 1, wherein In step (1), the fluorescence response value A is the fluorescence response value of the pectin aqueous solution under the conditions of an excitation wavelength of 285 nm and an emission wavelength of 463±5 nm; Furthermore, step (2) includes: obtaining a fluorescence response value A1 of the polysaccharide mixed solution to be tested under the conditions of an excitation wavelength of 285 nm and an emission wavelength of 463±5 nm.
3. The method according to claim 1, wherein In step (1), the fluorescence response value A is the fluorescence response value of the pectin aqueous solution under the conditions of an excitation wavelength of 285 nm and an emission wavelength of 463 nm; Furthermore, step (2) includes: obtaining a fluorescence response value A1 of the polysaccharide mixed solution to be tested under the conditions of an excitation wavelength of 285 nm and an emission wavelength of 463 nm.
4. The method according to any one of claims 1 to 3, wherein: The standard curve is y=1608056x+101919(R 2 =1), where x represents the pectin concentration (in mg / mL), the concentration range of x is between 0 and 1 mg / mL, and y represents the fluorescence response value.
5. The method according to any one of claims 1 to 4, wherein: The polysaccharide mixed solution contains pectin.
6. The method according to claim 5, wherein: The polysaccharide mixed solution further comprises one or more selected from starch, sodium carboxymethyl cellulose and xylan.
7. The method according to claim 5, wherein: The polysaccharide mixture is an artificially prepared polysaccharide mixture or a naturally extracted plant polysaccharide mixture.
8. The method according to claim 7, wherein: The plant is tobacco (such as flue-cured tobacco), citrus, astragalus or dendrobium.