Raman spectrum technology detection method for gel quality of minced pork treated by starch

Abstract

The invention belongs to the technical field of nondestructive rapid detection, and particularly relates to a Raman spectrum technology detection method for the quality of minced pork gel treated by starch. The method comprises the following steps: preparing a minced pork sample containing starch; determining physical and chemical indexes of the minced pork sample; collecting a Raman spectrum of the minced pork sample, and preprocessing the spectrum; and finally, constructing a quantitative prediction model for the gel quality of the minced pork. According to the method, starch treatment and Raman spectrum technologies are creatively combined, complex information related to the quality of the minced pork gel can be efficiently captured and excavated, complex and nonlinear minced pork Raman spectrum data are linearly separable through the support vector machine model, and finally efficient, accurate and nondestructive detection of the quality of the minced pork is achieved. Wide application prospects are realized.

Description

Technical Field

[0001] The invention belongs to the technical field of non-destructive rapid detection, and in particular relates to a method for detecting the gel quality of ground pork treated with starch using Raman spectroscopy technology. Background Art

[0002] Pork mince is a kind of meat product made by adding a certain amount of ingredients to fresh pork and mincing it into fine mince, and then centrifuging and heat processing it. It is deeply loved by consumers because of its firmness and elasticity, delicate and chewy taste, and rich protein content. Among them, the difference in the secondary structure of protein affects the texture, flavor, water retention and tenderness of the meat. However, in the conventional preparation process of pork mince, there are problems such as high surface viscosity and loose structure caused by internal pores or cracks, which seriously affect the quality and economic benefits of pork mince products. Starch can be used as an exogenous additive for meat products due to its low cost and strong water retention to improve product quality. During the heating process, the gelatinized starch gradually forms a gelatinous matrix, which fills and fixes the gaps inside the pork mince, making the overall network structure more uniform and compact. However, there are few reports on the research on quality based on starch treatment in the field of detection. Therefore, the present invention conducts a rapid detection study of pork mince quality by adding starch during the preparation process of pork mince, which is of great significance to improving the quality of pork mince products.

[0003] In addition, most of the current methods for testing the quality of minced pork are traditional methods. For example, the traditional method of measuring water holding capacity and gel strength requires the use of centrifuges and food property analyzers. However, these conventional methods have obvious defects. For example, using a property analyzer to measure gel strength requires direct puncture of the sample, and multiple measurements of the same sample are required to obtain a more accurate result, which makes it time-consuming and inefficient. This makes it difficult to meet the needs of rapid on-site testing of minced pork during large-scale production. Summary of the invention

[0004] In order to solve the above-mentioned technical problems, the present invention provides a method for detecting the quality of minced pork gel under starch treatment by Raman spectroscopy technology; firstly, starch-containing minced pork gel is prepared, and a quantitative prediction model is constructed by combining the physicochemical indicators of gel strength and water holding capacity with Raman spectroscopy data, and finally, the protein secondary structure content is calculated by the characteristic peak area of ​​Raman spectroscopy, so as to realize rapid and non-destructive detection of the quality of minced pork.

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

[0006] A method for detecting the gel quality of ground pork treated with starch by Raman spectroscopy, comprising the following steps:

[0007] Step 1, preparing minced pork gel: fresh pork tenderloin is selected as a sample, and fat and connective tissue on the fresh pork tenderloin are first removed to obtain processed pork tenderloin; the processed pork tenderloin is then fully mixed with water, salt and starch, and the obtained mixture is minced to obtain a starch-raw minced meat mixture; the starch-raw minced meat mixture is then centrifuged to remove pores to obtain a centrifuged product; finally, the centrifuged product is heated in a constant temperature water bath to obtain minced pork gel;

[0008] Preferably, the mass ratio of the processed pork tenderloin, water and salt in step 1 is 40:8:1-2, and the amount of starch added is 5-25% of the mass of the processed pork tenderloin; the starch includes corn starch, potato starch, mung bean starch and pea starch.

[0009] Preferably, in step 1, the centrifugal speed is 1500-2000 r / min, and the centrifugal time is 10-15 min.

[0010] Preferably, in step 1, the constant temperature water bath heating is preheated at 42-45° C. for 35-40 min, and then heated to 77-82° C. for 30-40 min.

[0011] Step 2: The minced pork gel prepared in step 1 is used as a sample to be tested and divided into two parts, one part is used to test the physical and chemical indicators of the minced pork gel, wherein the physical and chemical indicators include the water holding capacity and gel strength of the minced pork gel;

[0012] Another portion collects Raman spectrum data of minced pork gel, and performs baseline processing on the Raman spectrum data of minced pork gel to obtain pre-processed Raman spectrum data;

[0013] Preferably, in step 2, when determining the water holding capacity, the mass before centrifugation is first determined; then 2-4 layers of filter paper are used to wrap the minced pork gel, and the mass after centrifugation is determined at a centrifugal speed of 8000-9000r / min and a centrifugal time of 15-20min. The water holding capacity is the mass ratio after centrifugation to that before centrifugation.

[0014] Preferably, in step 2, the gel strength is determined by selecting a P / 0.5R spherical probe for penetration testing, using a pre-test speed of 2-3 mm / s and a test speed of 0.5-1 mm / s, and setting the penetration distance to 8-10 mm and the trigger force to 5 g.

[0015] Preferably, in the step 2, the spectral data of the minced pork gel is collected using a fully automatic confocal micro-Raman spectrometer, the collection time is 20-30s, and the excitation wavelength is 532nm; the baseline processing method is: the spectral smoothness is 15-20, the maximum number of fitting points is 70-80, and the number of noise points is 10-20.

[0016] Step 3: Based on the Raman spectrum data preprocessed in step 2, the -1 The corresponding peak areas are used to calculate the protein secondary structure content;

[0017] Preferably, in step 3, when calculating 1650-1700cm -1 When the peak area at is calculated, the response function width value is 1-5, the smoothness is 1-5%, the convergence criterion parameter is 2-4%, and the percentage of peak amplitude change is 2-3%.

[0018] Step 4: The physical and chemical indicators (water holding capacity and gel strength) measured in step 2 and the corresponding pre-processed Raman spectrum data are divided into a training set and a prediction set in proportion, and quantitative prediction models of water holding capacity and gel strength of minced pork gel are constructed respectively. The quality of minced pork gel can be detected based on the prediction model.

[0019] Preferably, in step 4, the ratio of the training set to the prediction set is 3:2.

[0020] Preferably, in the step 4, in constructing the quantitative prediction model of water holding capacity and gel strength of minced pork gel: the independent variable (Raman spectral data obtained in step 2) and the dependent variable (physical and chemical values ​​of gel strength and water holding capacity obtained in step 2) are normalized to [-1, 1]; the cross-validation fold is 5-10, the evolutionary generations and population size of the genetic algorithm (particle swarm optimization) are 90-105 and 15-25 respectively; the range of the regularization parameter c and the kernel function parameter g is [-8, 8].

[0021] The beneficial effects of this technical invention are as follows:

[0022] 1. The present invention adds starch during the preparation of minced pork, and optimizes the type of starch and the use conditions, thereby significantly improving the loose structure caused by macropores or cracks that occur under conventional preparation.

[0023] 2. The present invention uses a confocal micro-Raman spectrometer to collect spectral data of minced pork. Compared with traditional physical and chemical testing, it can more quickly, efficiently and accurately detect effective information related to the quality of minced pork.

[0024] 3. The quantitative prediction model of the present invention is an uninformative variable elimination-support vector machine model. Its powerful nonlinear processing method is more suitable for complex and inseparable Raman spectral data of minced pork. It can use high-dimensional space to mine the relationship between Raman spectrum and gel strength and water holding capacity, and then more accurately predict the quality of minced pork gel, achieving substantial technical effects. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is an operation flow chart of the present invention.

[0026] Figure 2 Electron micrographs of pork mince gel with different types of starch added, where A is the control, B is mung bean starch, C is pea starch, D is corn starch, and E is potato starch.

[0027] Figure 3 The graph shows the effects of different starches and their added amounts on the water holding capacity (A) and gel strength (B) of minced pork gel.

[0028] Figure 4 The ratio of protein secondary structure content in pork minced gel with different types of starch added.

[0029] Figure 5 This is a schematic diagram of the prediction results of the uninformative variable elimination-support vector machine model in Example 5 for the gel strength and water holding capacity of minced pork. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. In addition, with regard to the numerical range in the present invention, it should be understood that each intermediate value between the upper limit and the lower limit of the range is also included. Any intermediate value within the stated value or stated range, and each smaller range between other intermediate values ​​within these stated values ​​or ranges also belong to the content of the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded within the scope. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians of the art without making creative work are within the scope of protection of this application.

[0031] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, the present application is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0032] Embodiment 1:

[0033] Step 1. Preparation of minced pork gel: fresh pork tenderloin was selected as a sample. The fat and connective tissue on the fresh pork tenderloin were first removed to obtain the processed pork tenderloin, which was cut into small pieces. The pieces were then mixed with water and salt in a mass ratio of 40:8:1. Mung bean starch was added at 5%, 10%, 15%, 20% and 25% of the mass of the processed pork tenderloin, respectively. After mixing, the mixture was minced in a meat grinder for 3 minutes to obtain a starch-raw minced meat mixture.

[0034] 45 g of the starch-meat mixture was placed in a centrifuge tube and centrifuged at 1800 rpm for 10 minutes. Finally, a two-stage heating method was adopted, first preheating at 42°C in a constant temperature water bath for 40 minutes, then heating to 78°C for 25 minutes to obtain pork mince gel.

[0035] Step 2: using the minced pork gel prepared in step 1 as a sample to be tested, and measuring the physical and chemical indicators of the minced pork gel; the physical and chemical indicators include water holding capacity (a) and gel strength (b);

[0036] (a) The steps for determining the water holding capacity of pork mince gel are as follows: first, determine the mass before centrifugation; then, wrap the pork mince gel with three layers of filter paper, centrifuge at 8000 r / min for 10 minutes, and determine the mass after centrifugation. The water holding capacity is the ratio of the mass before centrifugation to the mass after centrifugation.

[0037] (b) The steps for determining the gel strength of minced pork gel are as follows: cut the minced pork gel into cylinders (20 mm × 20 mm); select a P / 0.5R spherical probe for penetration test, with a pre-test speed of 2.00 mm / s, a test speed of 1.00 mm / s, and a post-test speed of 1.00 mm / s; set the penetration distance to 10 mm, the trigger force to 5 g, and obtain the breaking force data; the gel strength is the product of the breaking force and the breaking distance.

[0038] Embodiment 2:

[0039] The operation is the same as in Example 1, except that mung bean starch is replaced by potato starch.

[0040] Embodiment 3:

[0041] The operation is the same as in Example 1, except that mung bean starch is replaced by pea starch.

[0042] Embodiment 4:

[0043] The operation is the same as in Example 1, except that mung bean starch is replaced by corn starch.

[0044] Comparative Example 1:

[0045] The operation is the same as in Example 1, except that mung bean starch is not added.

[0046] Finally, the starches (mung bean starch, potato starch, pea starch, corn starch) used in different examples and their different addition amounts (5%, 10%, 15%, 20%, 25%) were statistically analyzed to determine the water holding capacity and gel strength of minced pork gel. Figure 2As shown, increasing the addition amount of the four starches from 0% to 15% can significantly improve the water holding capacity (P<0.05) and gel strength (P<0.05); specifically, the water holding capacity increased from 68.148% (no starch) to 74.968% (mung bean starch), 80.7% (potato starch), 75.508% (pea starch) and 78.378% (corn starch), respectively; similarly, the gel strength increased from 1750.827 g×mm (no starch) to 2415.761 g×mm (mung bean starch), 3139.254 g×mm (potato starch), 2456.961 g×mm (pea starch) and 2908.648 g×mm (corn starch), respectively.

[0047] The above results show that the addition of starch improves water holding capacity and gel strength, but the improvement effects of different types of starch are not the same, and potato starch has the best effect. At the same time, the amount of starch added is also very important. Too little effect is not obvious, but the more the better is not the case. When the starch content exceeds 15%, it cannot further improve water holding capacity and gel strength. Therefore, 15% is selected as the optimal addition amount.

[0048] On the other hand, combined with the electron microscopy results ( Figure 1 ) It can be found that potato starch has the most significant filling effect on the pork mince gel network.

[0049] Embodiment 5:

[0050] Step 1: Prepare pork mince gel:

[0051] Fresh pork tenderloin was selected as a sample. The fat and connective tissue on the fresh pork tenderloin were first removed to obtain the processed pork tenderloin, which was cut into small pieces and then mixed with water and salt in a mass ratio of 40:8:1. Mung bean starch accounting for 15% of the mass of the processed pork tenderloin was added, and the mixture was mixed in a meat grinder for 3 minutes to obtain a starch-raw minced meat mixture.

[0052] 45 g of the starch-meat mixture was placed in a centrifuge tube and centrifuged at 1800 rpm for 10 minutes. Finally, a two-stage heating method was adopted, first preheating at 42°C in a constant temperature water bath for 40 minutes, then heating to 78°C for 25 minutes to obtain a pork mince gel based on mung bean starch.

[0053] Similarly, the operation is carried out according to step one, except that mung bean starch is replaced by pea starch, corn starch and potato starch, respectively, to obtain pea starch-based minced pork gel, corn starch-based minced pork gel and potato starch-based minced pork gel.

[0054] Step 2: using each of the obtained pork mince gels based on different starches as a test sample to form 4 test samples; similarly using a group without starch as a control to form 5 groups of test samples; and dividing each test sample into two parts, one for determining the physical and chemical indicators of the pork mince gel; the physical and chemical indicators are water holding capacity and gel strength;

[0055] (1) Physical and chemical indicators:

[0056] (a) The steps for determining the water holding capacity of pork mince gel are as follows: first, determine the mass before centrifugation; then, wrap the pork mince gel with three layers of filter paper, centrifuge at 8000 r / min for 10 minutes, and determine the mass after centrifugation. The water holding capacity is the ratio of the mass before centrifugation to the mass after centrifugation.

[0057] (b) The steps for determining the gel strength of the pork mince gel are as follows:

[0058] The minced pork gel was cut into cylinders (20mm×20mm). A P / 0.5R spherical probe was selected for penetration test. The pre-test speed was 2.00mm / s, the test speed was 1.00mm / s, and the post-test speed was 1.00mm / s. The penetration distance was set to 10mm and the trigger force was 5g to obtain the breaking force data. The gel strength is the product of the breaking force and the breaking distance.

[0059] (2) Another sample of minced pork gel was collected using a fully automatic confocal micro-Raman spectrometer to collect spectral data of minced pork gel, and the Raman spectrum of the minced pork was preprocessed. The specific operation is as follows: When collecting Raman spectrum information of minced pork gel, the excitation wavelength is 532nm, a 50x objective lens is used to determine the collection point, and the collection time is 27 seconds. Preprocessing method: the smoothing index is 15, the maximum number of fitting points is 75 times, and the number of noise points is 10.

[0060] Step 3: Collect the Raman spectrum of minced pork at 1650-1700cm -1 The specific operation is as follows: import the Raman spectrum data collected in step 2 into PeakFit, with a response function width value of 2.5, a smoothing degree of 5%, a convergence standard parameter of 3%, and a peak amplitude change percentage of 2.5%; export each characteristic peak area. Among them, 1650-1658cm -1 The characteristic peak area at 1660-1665cm corresponds to the α-helix content value. -1 The characteristic peak area at 1665-1680cm corresponds to the random curl content value. -1 The characteristic peak area at 1680-1690cm corresponds to the β-folding content value. -1 The characteristic peak area at corresponds to the β-turn content value;

[0061] Step 4: Combine the conventional measured values ​​of pork mince gel strength and water holding capacity with the corresponding Raman spectral data; each group contains 16 sets of data, and the five groups share 80 sets of data; the training set and the test set are 48 sets and 32 sets respectively. The quantitative prediction model used is the uninformative variable elimination-support vector machine model (which can present the linearly inseparable pork mince Raman spectral data to a high-dimensional linearly separable hyperplane through the hyperparameter optimization process). Then import the training set and the test set into the uninformative variable elimination-support vector machine model.

[0062] In establishing the quantitative prediction model: the independent variable (Raman spectral data obtained in step 2) and the dependent variable (physical and chemical values ​​of gel strength and water holding capacity obtained in step 2) are normalized to [-1, 1]; the cross-validation fold is set to 5, the evolutionary generations and population size of the genetic algorithm (particle swarm optimization) are 100 and 20 respectively; the range of the regularization parameter c and the kernel function parameter g is [-8, 8].

[0063] Finally, the collected Raman spectra of minced pork (1650-1700cm -1 ) characteristic peaks to obtain the area ratio of each region ( Figure 4 As shown in the figure, for β-folding that is beneficial to the formation of gel network structure and random coiling that is not conducive to the formation of gel network structure, compared with the addition of other starches, the β-folding content of pork mince gel with added potato starch is the highest (28.121%), and the random coiling is the lowest (20.667%), indicating that the addition of potato starch can more effectively improve the protein conformation in the pork mince gel system and make the gel network closely connected.

[0064] Run the prediction results in step 4 as follows Figure 5 Shown: Gel strength training correlation coefficient Rc of minced pork 2 =0.9393, RMSEC=101.0498 (g×mm) ， Prediction correlation coefficient Rp 2 =0.8508, RMSEP = 164.8441 (g × mm), RPD = 2.1981; Correlation coefficient of water holding capacity training of minced pork Rc 2 =0.9047, RMSEC = 1.1770 (%), prediction correlation coefficient Rp 2 =0.8553, RMSEP=1.5468(%), RPD=2.1567.

[0065] The above results indicate that the solution provided by the present invention can achieve quantitative prediction of the gel strength and water holding capacity (gel quality) of minced pork, and can more quickly, efficiently and accurately detect effective information related to the quality of minced pork, thus achieving substantial technical effects.

[0066] The embodiments described above are only descriptions of the preferred methods of the present application, and are not intended to limit the scope of the present application. Without departing from the design spirit of the present application, various modifications and improvements made to the technical solutions of the present application by ordinary technicians in this field should fall within the scope of protection determined by the claims of the present application.

Claims

1. A method for detecting the gel quality of ground pork treated with starch by Raman spectroscopy, characterized in that: The following steps are involved: Step 1, preparing minced pork gel: fresh pork tenderloin is selected as a sample, and fat and connective tissue on the fresh pork tenderloin are first removed to obtain processed pork tenderloin; the processed pork tenderloin is then fully mixed with water, salt and starch, and the obtained mixture is minced to obtain a starch-raw minced meat mixture; the starch-raw minced meat mixture is then centrifuged to remove pores to obtain a centrifuged product; finally, the centrifuged product is heated in a constant temperature water bath to obtain minced pork gel; Step 2: The minced pork gel prepared in step 1 is used as a sample to be tested and divided into two parts, one part is used to test the physical and chemical indicators of the minced pork gel, wherein the physical and chemical indicators include the water holding capacity and gel strength of the minced pork gel; Another portion collects Raman spectrum data of minced pork gel, and performs baseline processing on the Raman spectrum data of minced pork gel to obtain pre-processed Raman spectrum data; Step 3: Based on the Raman spectrum data preprocessed in step 2, the -1 The corresponding peak areas are used to calculate the protein secondary structure content; Step 4: divide the physicochemical indicators measured in step 2 and the corresponding pre-processed Raman spectral data into a training set and a prediction set in proportion, and construct quantitative prediction models for the water holding capacity and gel strength of minced pork gel, respectively.

2. The method for detecting the gel quality of ground pork by Raman spectroscopy after starch treatment according to claim 1, characterized in that: The mass ratio of the processed pork tenderloin, water and salt in step 1 is 40:8:1-2, and the amount of starch added is 5-25% of the mass of the processed pork tenderloin; the starch includes corn starch, potato starch, mung bean starch and pea starch.

3. The method for detecting the gel quality of ground pork by Raman spectroscopy after starch treatment according to claim 1, characterized in that: In the step 1, the centrifugal speed is 1500-2000 r / min, and the centrifugal time is 10-15 min.

4. The method for detecting the gel quality of ground pork by Raman spectroscopy after starch treatment according to claim 1, characterized in that: In the step 1, the constant temperature water bath heating is first preheated at 42-45° C. for 35-40 minutes, and then heated to 77-82° C. for 30-40 minutes.

5. The method for detecting the gel quality of ground pork by Raman spectroscopy after starch treatment according to claim 1, characterized in that: In the step 2, when measuring the water holding capacity, the mass before centrifugation is first measured; then 2-4 layers of filter paper are used to wrap the minced pork gel, and the mass after centrifugation is measured at a centrifugal speed of 8000-9000r / min and a centrifugal time of 15-20min. The water holding capacity is the mass ratio after centrifugation to that before centrifugation.

6. The method for detecting the gel quality of ground pork by Raman spectroscopy after starch treatment according to claim 1, characterized in that: In the step 2, the gel strength is measured by selecting a P / 0.5R spherical probe for penetration testing, using a pre-test speed of 2-3 mm / s and a test speed of 0.5-1 mm / s, and setting the penetration distance to 8-10 mm and the trigger force to 5 g.

7. The method for detecting the gel quality of ground pork by Raman spectroscopy after starch treatment according to claim 1, characterized in that: In the step 2, the spectral data of the minced pork gel is collected using a fully automatic confocal micro-Raman spectrometer, the collection time is 20-30s, and the excitation wavelength is 532nm; the baseline processing method is: the spectral smoothness is 15-20, the maximum number of fitting points is 70-80, and the number of noise points is 10-20.

8. The method for detecting gel quality of ground pork by Raman spectroscopy after starch treatment according to claim 1, characterized in that: In step 3, when calculating 1650-1700cm -1 When the peak area at is calculated, the response function width value is 1-5, the smoothness is 1-5%, the convergence criterion parameter is 2-4%, and the percentage of peak amplitude change is 2-3%.

9. The method for detecting gel quality of ground pork by Raman spectroscopy after starch treatment according to claim 1, characterized in that: In the step 4, the ratio of the training set to the prediction set is 3:

2.

10. The method for detecting gel quality of ground pork by Raman spectroscopy after starch treatment according to claim 1, characterized in that: In the step 4, in constructing the quantitative prediction model of water holding capacity and gel strength of minced pork gel: the independent variables and dependent variables are normalized to [-1, 1]; the cross-validation fold is 5-10, the evolutionary generations and population size of the genetic algorithm are 90-105 and 15-25 respectively; the range of the regularization parameter c and the kernel function parameter g is [-8, 8].

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