Tea oil adulteration identification method based on ultrasonic detection and characteristic indication substance determination

Abstract

The invention belongs to the technical field of tea oil adulteration identification, and discloses a tea oil adulteration identification method based on ultrasonic detection and characteristic indication substance determination, and the method comprises the following steps: S1, respectively collecting pure camellia oil, other vegetable oil pure oil and a plurality of adulterated camellia oil; s2, carrying out ultrasonic detection on the collected sample oil; s3, performing liquid chromatography-mass spectrometry analysis on the sample, and determining the content of trace active components in the sample oil; and S4, establishing a PLS model between the ultrasonic parameters and the adulterated oil ratio by using a partial least square method, performing principal component analysis and orthogonal partial least square discriminant analysis on the basis of a response value obtained by liquid chromatography-mass spectrometry analysis, establishing a camellia oil authentic identification model, and predicting the variety of adulterated oil. According to the method, adulterated tea oil can be quickly distinguished by utilizing the PLS model, the distinguishing accuracy rate reaches 95% or above, and the variety of adulterated oil can be distinguished and the production process of the sample tea oil can be determined by utilizing the camellia oil authentic identification model. The method is simple to operate and reliable in technology.

Description

Technical Field

[0001] The invention relates to the technical field of tea oil adulteration identification, and in particular to a tea oil adulteration identification method based on ultrasonic detection and characteristic indicator substance determination. Background Art

[0002] Tea oil is a woody edible vegetable oil unique to my country and one of the most popular high-quality edible vegetable oils on the market in my country. Its chemical composition is very similar to that of olive oil, with an unsaturated fatty acid content of up to 90%, of which the oleic acid content is as high as 75% or more. Therefore, it is an ideal health care and nutritional oil for patients with hypertension, hyperlipidemia, atherosclerosis, etc. The trace active nutrients such as polyphenols, vitamin E, squalene, and phytosterols rich in tea oil are also of great significance to human health. Due to its limited annual output and scarce sources, tea oil is more expensive than other edible vegetable oils. In order to maximize their profits, illegal vendors often mix other cheap vegetable oils into pure camellia oil and sell it as pure camellia oil. In addition, the processing technology of tea oil includes pressing and leaching. The price of pressed tea oil is usually higher than that of leached tea oil. Therefore, some merchants will sell leached tea oil as pressed tea oil to obtain higher profits. These industry chaos have led to uneven quality of camellia oil products and chaotic market prices, which not only harmed the interests of the general public, but also seriously threatened the legitimate interests of pure camellia oil manufacturers and hindered the healthy development of the oil camellia industry. In order to safeguard the interests of the general public and stabilize the market order, developing an effective certification method for identifying pure camellia oil has been an important task that the food safety industry needs to solve and develop over the years.

[0003] At present, many edible oil certification and testing technologies have been developed, such as gas chromatography, high performance liquid chromatography, gas chromatography-mass spectrometry, electronic nose, near infrared spectroscopy, Raman spectroscopy, differential scanning calorimetry, etc., which are widely used in food quality control and material performance measurement. Among these methods, the signal overlap and peak overlap problems of electronic nose, spectroscopy and nuclear magnetic resonance technology make it difficult to improve their detection accuracy, while detection methods such as chromatography and mass spectrometry require cumbersome sample pretreatment and the detection process takes a long time. The physical and chemical properties of different types of oils are crucial to distinguish them. In recent years, ultrasonic technology has been widely used in the quality detection of industrial oils such as petroleum, which can quickly and accurately evaluate the physical properties of liquids (density, viscosity, etc.). Studies have found that when ultrasonic waves propagate in oil media, their energy attenuation is closely related to the type of oil, which makes it possible to reflect the type and purity of oil by measuring the changes in parameters such as speed, energy attenuation, and acoustic impedance when ultrasonic waves penetrate vegetable oil. However, adulteration identification uses a single detection technology, and the results can only reflect the differences in a small part of the characteristic values, which is not effective in terms of detection accuracy and repeatability. Summary of the invention

[0004] The present invention is intended to provide a method for identifying adulteration of camellia oil based on ultrasonic detection and determination of characteristic indicator substances, using ultrasonic nondestructive detection to identify whether the camellia oil is adulterated, and further determining characteristic indicators of adulterated camellia oil to identify the type of adulterated oil. By analyzing the lipid trace active components of camellia oil and measuring the trace active nutrients therein, combining mass spectrometry with ultrasonic detection technology, a multivariate method is established to analyze the oil characteristics of camellia oil, which can achieve rapid detection and accurate identification of adulterated camellia oil, with high detection accuracy.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] A method for identifying tea oil adulteration based on ultrasonic detection and characteristic indicator substance determination comprises the following steps:

[0007] S1. Sample collection: Collect pure camellia oil samples produced by pressing and leaching methods and several pure oil samples of other vegetable oils, with camellia oil as the adulterated oil and other oils as the adulterated oils. The adulterated oils and the adulterated oils are evenly mixed in different mass proportions to obtain experimental samples of adulterated camellia oil;

[0008] S2. Physical and chemical property testing of sample oils: at a preset temperature, ultrasonic testing was performed on pure camellia oil samples, pure oil samples of other vegetable oils, and adulterated camellia oils. The acoustic impedance, energy attenuation, and ultrasonic velocity change when ultrasound passed through the oil were measured. The density and viscosity of the corresponding sample oils were determined using a densitometer and a rheometer.

[0009] S3. Analysis of trace active ingredients in sample oil: pure camellia oil, pure oil of other vegetable oils and adulterated camellia oil were weighed, and after pretreatment, the samples were subjected to liquid chromatography-mass spectrometry analysis to determine the content of trace active ingredients in the sample oil;

[0010] S4. Sample adulteration identification: Calculate the correlation coefficient between viscosity, density and ultrasonic parameters to obtain the multivariate equation of viscosity and density to ultrasonic parameters, and use partial least squares method to establish the relationship model between independent variables and dependent variables, where the independent variables are viscosity, density and ultrasonic parameters, and the dependent variable is the proportion of adulterated oil; Based on the response values ​​obtained by liquid chromatography-mass spectrometry analysis, perform principal component analysis and orthogonal partial least squares discriminant analysis to establish a camellia oil authentication model and predict the type of adulterated oil.

[0011] Furthermore, in S1, the mixing ratio of the adulterated oil to the mixed oil is 0%, 1%, and 5% respectively, and increases gradually from 5% to 100%; the mixing ratio is defined as: adulterated oil mass / (mixed oil mass+adulterated oil mass)×100%.

[0012] Further, in S1, the adulterated oil includes one or two of peanut oil, soybean oil, rapeseed oil, cottonseed oil, corn oil, sunflower oil, cottonseed oil and palm oil.

[0013] Further, in S2, the preset temperatures are 5°C, 10°C, 20°C, and 30°C.

[0014] Further, in S3, the specific operation steps of pretreatment are: weigh 0.1g of tea oil sample, place it in a conical flask, add 2g of ascorbic acid and 10mL of water, vortex and shake well, then add 30mL of anhydrous ethanol and 15mL of 50% potassium hydroxide aqueous solution, shake well, ultrasonically treat for 30min under ultrasonic power of 80W, and then saponify at 80℃ for 1h; after cooling, extract 3 times with 40mL of petroleum ether, combine the extracts, wash with water until neutral, transfer the petroleum ether layer to a centrifuge bottle, blow dry with nitrogen, make up to volume with methanol, pass through a 0.22μm organic filter membrane, and wait for analysis.

[0015] Furthermore, in S3, the chromatographic column for liquid chromatography-mass spectrometry analysis was a Thermo scientific C18 reverse phase column, the column temperature was 30°C, the injection volume was 5 μL, the mobile phase was 0.02% formic acid methanol + acetonitrile, gradient elution, the mobile phase flow rate was 0.50 mL / min, and the mass spectrometry analysis adopted a positive ion scanning mode, the carrier gas was high-purity nitrogen, and the flow rate was 10 mL / min.

[0016] Furthermore, in S3, trace active ingredients in the sample oil include sterols, squalene, carotene, and polyphenols.

[0017] The principle and beneficial effects of this technical solution are:

[0018] The present invention establishes a prediction model based on the specific changes of parameters such as acoustic impedance, energy attenuation and ultrasonic velocity when ultrasound passes through different oils, and then substitutes the ultrasonic parameters of the product to be tested into the established model for analysis and judgment. Since the ultrasonic time is very short, the present invention can quickly identify whether tea oil is adulterated, which can usually be completed within a few seconds, and the sample does not need any treatment, which belongs to non-destructive in-situ detection, and can realize the authentication operation of 1%-100% of the tea oil adulteration mass, and the overall accuracy reaches more than 95%. Compared with the traditional detection method, the detection accuracy of the present invention is equivalent, but the detection efficiency is much higher and the cost is much lower than the traditional chromatography or mass spectrometry. On the other hand, the present invention obtains the content of characteristic trace active ingredients in different oils through mass spectrometry analysis of pure tea oil and adulterated tea oil of different processes, and establishes relevant prediction models. After using ultrasound to identify the adulteration of tea oil, the type of adulterated oil can be further determined by this model, and the preparation process of tea oil can also be determined by this model.

[0019] The identification method of the present invention is simple, fast, accurate and specific, and provides reliable technical guarantee for tea oil safety and authentication of high-end edible oil industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The present invention is a process flow chart of a method for identifying tea oil adulteration based on ultrasonic detection and characteristic indicator substance determination.

[0021] Figure 2 It is a schematic diagram of the structure of the ultrasonic detection device.

[0022] The names of the corresponding marks in the accompanying drawings are:

[0023] 1. Sealed container; 2. Ultrasonic sensor; 3. Fixing plate; 4. Pulse generator; 5. Micro oscilloscope; 6. Microcomputer processor; 7. Reflection plate. DETAILED DESCRIPTION

[0024] The present invention is further described in detail below in conjunction with the embodiments:

[0025] like Figure 1 As shown, a method for identifying tea oil adulteration based on ultrasonic detection and characteristic indicator substance determination comprises the following steps:

[0026] S1. Sample collection:

[0027] (1) Twenty samples of pure camellia oil produced by pressing method (numbered CY1 to CY20), 20 samples of pure camellia oil produced by leaching method (numbered CJ1 to CJ20), 30 samples of pure peanut oil (numbered HS1 to HS30), 20 samples of pure corn oil (numbered YM1 to YM20), and 25 samples of pure rapeseed oil (numbered CZ1 to CZ25) were collected from the market.

[0028] (2) Pure camellia oil (CY1-CY20) was used as the adulterated oil and peanut oil (HS1) was used as the adulterated oil. The adulterated oil and the adulterated oil were uniformly mixed in a mass ratio of 1%, 5%, 10%, 15%, 20%, 25%, ..., 95% to obtain experimental samples of adulterated camellia oil, which were numbered H1-H400.

[0029] (3) Camellia oil (CY1~CY20) was used as the adulterated oil and corn oil (YM1) was used as the adulterated oil. The adulterated oil and the adulterated oil were uniformly mixed in a mass ratio of 1%, 5%, 10%, 15%, 20%, 25%, ..., 95% to obtain experimental samples of adulterated camellia oil, which were numbered Y1~Y400.

[0030] (4) Camellia oil (CJ1-CJ20) was used as the adulterated oil and rapeseed oil (CZ1) was used as the adulterated oil. The adulterated oil and the adulterated oil were uniformly mixed in a mass ratio of 1%, 5%, 10%, 15%, 20%, 25%, ..., 95% to obtain experimental samples of adulterated camellia oil, which were numbered C1-C400.

[0031] S2. Physical and chemical properties of sample oil:

[0032] (5) Detect the acoustic impedance, energy attenuation and ultrasonic velocity changes of all sample oils. The detection device is as follows: Figure 2 As shown, it consists of an ultrasonic sensor 2 and a sealed container 1, the container contains the oil sample to be tested and is immersed in warm water at 20°C. The device also includes a pulse generator 4, a micro oscilloscope 5, a microcomputer processor 6, a fixing plate 3 and a reflecting plate 7.

[0033] (6) Density and viscosity of all sample oils were measured by densitometer and rheometer, and the normality of density, viscosity and ultrasonic parameters was evaluated by Shapiro-Wilk test.

[0034] S3. Analysis of trace active ingredients in sample oil:

[0035] (7) According to the methods in (1)-(4), tea oil, tea oil + peanut oil, tea oil + corn oil, tea oil + rapeseed oil blended oil samples were prepared respectively. The samples were pretreated for liquid quality detection, wherein the pretreatment method is as follows: 0.1 g (accurate to 0.0001 g) of tea oil sample was weighed, placed in a conical flask, 2 g of ascorbic acid and 10 mL of water were added, vortexed and shaken, then 30 mL of anhydrous ethanol and 15 mL of 50% (v / v) potassium hydroxide aqueous solution were added, shaken, ultrasonically treated at an ultrasonic power of 80 W for 30 min, and then saponified at 80° C. for 1 h; after cooling, extracted with 40 mL of petroleum ether for 3 times, the extracts were combined, washed with water until neutral, the petroleum ether layer was transferred to a centrifuge bottle, dried with nitrogen, fixed to volume with methanol, and filtered through a 0.22 μm organic filter membrane for analysis.

[0036] (8) After sample pretreatment, liquid chromatography-mass spectrometry (LC-MS) was performed, wherein the LC-MS chromatographic conditions were set as follows:

[0037] Thermo scientific C 18 reverse phase column, triple quadrupole mass spectrometer (TripleQuad4500), mobile phase: A is 0.02% formic acid methanol, B is 100% acetonitrile, flow rate: 0.50mL / min; injection volume: 5μL; column temperature: 30℃. Gradient elution program: 0~1.0min, 85%B~95%B; 1.0~7.0min, 95%B; 7.0~12.5min, 95%B~100%B; 12.5~13.0min, 100%B~85%B.

[0038] The mass spectrometry detection method is:

[0039] Ion source: electrospray ionization source (ESI); scanning mode: positive ion scanning mode; capillary voltage: 3kV; spray voltage: 3.88kV; nebulizer gas pressure: 270kPa; drying gas (N2) flow rate: 10mL / min; desolvation temperature: 300℃; cone gas flow rate: 50L / hr; desolvation gas flow rate: 800L / hr; collision gas: Ar; scanning mode: SRM mode; sheath gas: 30units nitrogen (N2): 5units; evaporator temperature: 300℃.

[0040] (9) Use liquid chromatography-mass spectrometry to obtain the content of trace active ingredients (sterols, squalene, carotene, polyphenols) in the sample oil.

[0041] S4. Sample adulteration identification:

[0042] (10) According to the normality test results of (6), the correlation equations between density, viscosity and ultrasonic parameters were calculated using the XLSTAT Premium 2018 software package.

[0043] (11) The experimental data were collected and partial least squares (PLS) was performed using OriginPro 9.8 to find the relationship between the independent variables (ultrasonic parameters, oil sample density, and viscosity) and the dependent variable (mass fraction of adulterated oil). Ultrasonic parameters were then used to replace the oil sample density and viscosity in the relationship to obtain a relationship model for predicting the mass fraction of adulterated oil using ultrasonic parameters.

[0044] The model was trained using the PLS method, where the sample set information and prediction results are shown in Table 1:

[0045] Table 1 shows the tea oil prediction model training set and results based on the PLS method

[0046] Sample code tea oil Adulterated oil Adulteration ratio / % Predicted value / % Error value / % XL1 CY3 - 0 98.45 -1.55 XL2 CY4 HS2 1 96.28 -2.72 XL3 CY5 HS3 5 97.32 2.32 XL4 CY6 HS4 10 87.09 -2.91 XL5 CY7 HS5 1 97.83 -1.17 XL6 CY8 HS6 5 94.06 -0.94 XL7 CY9 HS7 10 88.02 -1.98 XL8 CY10 HS8 1 100.05 1.05 XL9 CY11 HS9 5 93.07 -1.93 XL10 CY12 HS10 10 91.05 1.05 XL11 CY13 HS11 1 99.86 0.86 XL12 CY14 HS12 5 93.22 -1.78 XL13 CJ2 HS13 10 91.38 1.38 XL14 CJ3 HS14 1 98.75 -0.25 XL15 CJ4 HS15 5 92.06 -2.94 XL16 CJ5 HS16 10 87.34 -2.66 XL17 CJ6 HS17 1 100.02 1.02 XL18 CJ7 HS18 5 94.31 -0.69 XL19 CJ8 HS19 10 91.43 1.43 XL20 CJ9 - 0 101.32 1.32

[0047] It can be seen that the model has a good prediction effect for the adulteration ratio of peanut oil in tea oil of 1% to 10%, with an overall prediction accuracy of more than 95% and an error range of within ±3%.

[0048] (12) Based on the response values ​​obtained from liquid chromatography-mass spectrometry analysis, principal component analysis and orthogonal partial least squares discriminant analysis were performed to establish a camellia oil authentication model and predict the type of adulterated oil.

[0049] The model was trained using the OPLS-DA method, and the sample set information and prediction results are shown in Table 2:

[0050] Table 2 shows the tea oil prediction model training set and results based on the OPLS-DA method

[0051]

[0052] It can be seen that the model has a good prediction effect for the adulteration ratio of peanut oil in tea oil of 1% to 20%, and the prediction accuracy of whether it is adulterated is over 98%. When the adulteration ratio reaches more than 5%, the model's prediction accuracy of the type of adulterated oil reaches over 95%.

[0053] The identification steps of the method of the present invention for tea oil are firstly to perform ultrasonic detection and combine with a model to predict its purity, and further perform trace active component analysis on adulterated tea oil and combine with a model to predict the type of adulterated oil.

[0054] In summary, the present invention is a method for identifying adulteration of camellia oil based on ultrasonic detection and determination of characteristic indicator substances. Ultrasonic non-destructive detection is used to identify whether the camellia oil is adulterated, and characteristic indicators of adulterated camellia oil are further determined to identify the type of adulterated oil. By analyzing the lipid trace active components of camellia oil and measuring the trace active nutrients therein, mass spectrometry analysis is combined with ultrasonic detection technology to establish a multivariate method to analyze the oil characteristics of camellia oil, which can achieve rapid detection and accurate identification of adulterated camellia oil. At the same time, the model can identify the lowest adulteration level of 1%, and the overall accuracy reaches more than 95%. This method has high accuracy, no pollution to the environment, convenient detection and low cost, and expands the identification method of adulteration of camellia oil and other edible oils.

[0055] The above is only an embodiment of the present invention, and the common knowledge such as the known specific technical solutions or characteristics in the solution is not described in detail here. It should be pointed out that for those skilled in the art, several modifications and improvements can be made without departing from the technical solution of the present invention, which should also be regarded as the protection scope of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. A method for identifying tea oil adulteration based on ultrasonic detection and characteristic indicator substance determination, characterized in that: The following steps are involved: S1. Sample collection: Collect pure camellia oil samples produced by pressing and leaching methods and several pure oil samples of other vegetable oils, with camellia oil as the adulterated oil and other oils as the adulterated oils. The adulterated oils and the adulterated oils are evenly mixed in different mass proportions to obtain experimental samples of adulterated camellia oil; S2. Physical and chemical property testing of sample oils: at a preset temperature, ultrasonic testing was performed on pure camellia oil samples, pure oil samples of other vegetable oils, and adulterated camellia oils. The acoustic impedance, energy attenuation, and ultrasonic velocity change when ultrasound passed through the oil were measured. The density and viscosity of the corresponding sample oils were determined using a densitometer and a rheometer. S3. Analysis of trace active ingredients in sample oil: pure camellia oil, pure oil of other vegetable oils and adulterated camellia oil were weighed, and after pretreatment, the samples were subjected to liquid chromatography-mass spectrometry analysis to determine the content of trace active ingredients in the sample oil; S4. Sample adulteration identification: Calculate the correlation coefficient between viscosity, density and ultrasonic parameters to obtain the multivariate equation of viscosity and density to ultrasonic parameters, and use partial least squares method to establish the relationship model between independent variables and dependent variables, where the independent variables are viscosity, density and ultrasonic parameters, and the dependent variable is the proportion of adulterated oil; Based on the response values ​​obtained by liquid chromatography-mass spectrometry analysis, perform principal component analysis and orthogonal partial least squares discriminant analysis to establish a camellia oil authentication model and predict the type of adulterated oil.

2. The method for identifying tea oil adulteration based on ultrasonic detection and characteristic indicator substance determination according to claim 1, characterized in that: In S1, the mixing ratio of the adulterated oil to the mixed oil is 0%, 1%, and 5% as a gradient increasing from 5% to 100%; the mixing ratio is defined as: adulterated oil mass / (mixed oil mass+adulterated oil mass)×100%.

3. The method for identifying tea oil adulteration based on ultrasonic detection and characteristic indicator substance determination according to claim 1, characterized in that: In S1, the adulterated oil includes one or two of peanut oil, soybean oil, rapeseed oil, cottonseed oil, corn oil, sunflower oil, cottonseed oil and palm oil.

4. The method for identifying tea oil adulteration based on ultrasonic detection and characteristic indicator substance determination according to claim 1, characterized in that: In S2, the preset temperatures are 5°C, 10°C, 20°C, and 30°C.

5. The method for identifying tea oil adulteration based on ultrasonic detection and characteristic indicator substance determination according to claim 1, characterized in that: In S3, the specific steps of pretreatment are as follows: weigh 0.1 g of tea oil sample, place it in a conical flask, add 2 g of ascorbic acid and 10 mL of water, vortex and shake well, then add 30 mL of anhydrous ethanol and 15 mL of 50% potassium hydroxide aqueous solution, shake well, ultrasonically treat for 30 min at an ultrasonic power of 80 W, and then saponify at 80 ° C for 1 h; after cooling, extract 3 times with 40 mL of petroleum ether, combine the extracts, wash with water until neutral, transfer the petroleum ether layer to a centrifuge bottle, blow dry with nitrogen, make up to volume with methanol, pass through a 0.22 μm organic filter membrane, and wait for analysis.

6. The method for identifying tea oil adulteration based on ultrasonic detection and characteristic indicator substance determination according to claim 1, characterized in that: In S3, the chromatographic column for liquid chromatography-mass spectrometry analysis was a Thermo scientific C18 reverse phase column, the column temperature was 30°C, the injection volume was 5 μL, the mobile phase was 0.02% formic acid methanol + acetonitrile, gradient elution, the mobile phase flow rate was 0.50 mL / min, and the mass spectrometry analysis adopted the positive ion scanning mode, the carrier gas was high-purity nitrogen, and the flow rate was 10 mL / min.

7. The method for identifying tea oil adulteration based on ultrasonic detection and characteristic indicator substance determination according to claim 1, characterized in that: In S3, trace active ingredients in the sample oil included sterols, squalene, carotene, and polyphenols.

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