Method for evaluating quality of salted pork based on flavor substance analysis

Abstract

The invention provides a salted pork quality evaluation method based on flavor substance analysis, and the method comprises the following steps: S1, measuring the content of characteristic flavor substances of to-be-detected salted pork, taking OAV of the characteristic flavor substances as an independent variable, taking the flavor difference between the to-be-detected salted pork and representative Zhenjiang salted pork as a dependent variable, and adopting an OPLS-DA method to establish a discrimination model, obtaining a VIP value graph and a standardized regression coefficient graph; and S2, according to the positive and negative correlation of the characteristic flavor substance indexes in the standardized regression coefficient graph in the step S1, referring to the VIP value graph, taking the obtained VIP value as the weight of each characteristic flavor substance index, and adopting a weighted TOPSIS analysis method improved based on a grey correlation coefficient to finally obtain a relative closeness value. According to the method, the internal quality of the salted pork can be comprehensively evaluated, subjective assume is effectively eliminated, the reliability and accuracy of the evaluation result are enhanced, and a basis can be provided for quality control and protection of georationally marked products.

Description

Technical Field

[0001] The invention relates to the technical field of flavor chemical analysis, and in particular to a method for evaluating the quality of braised pork based on flavor substance analysis. Background Art

[0002] Zhenjiang Yaorou is one of the "three wonders" of Zhenjiang. It was once the main dish of cold dishes at state banquets. It is a famous food in Jiangsu Province and the Yangtze River Delta, with a history of more than 300 years. The raw materials are carefully selected, and the raw materials are selected from 3-4 jin of fresh pig's front feet. The pig's front feet have the characteristics of less fat, more lean meat, and sufficient toughness. The meat from other parts cannot be replaced. The production process of Zhenjiang Yaorou is to marinate the pig's front feet with saltpeter and salt, add spices, etc., cook them over low heat until they are crispy, and freeze them to condense. It has the four characteristics of being fragrant, crispy, fresh, and tender. The meat is red, white, smooth and crystal, and the marinated frozen meat is transparent, so it is also called "Crystal Yaorou".

[0003] The unique "yao aroma" of Zhenjiang Yao meat is an important reason why it is popular among consumers. Aroma is one of the sensory indicators of the quality of Zhenjiang Yao meat. The "yao aroma" of Zhenjiang Yao meat has a fresh meaty fragrance and a unique fat aftertaste, which is closely related to the volatile flavor substances in the Yao meat. Reducing sugars, amino acids, lipids, nucleotides, etc. are the main meat flavor precursors, which will produce volatile flavor substances through lipid oxidation, Strecker degradation, Maillard reaction, etc. These volatile flavor substances include aldehydes, alcohols, ketones, aromatics, etc., which together constitute the unique aroma of Zhenjiang Yao meat, but only a small part of them is the key to the overall aroma of Zhenjiang Yao meat.

[0004] In order to further improve the product quality and market competitiveness of Zhenjiang Yaorou, it is particularly important to conduct in-depth screening of the characteristic components that determine its flavor. These characteristic components not only constitute the unique flavor basis of Zhenjiang Yaorou, but also are an important mark that distinguishes it from other similar products. However, the current systematic screening research on the characteristic components of Zhenjiang Yaorou is still insufficient, which to a certain extent restricts the in-depth understanding of its flavor mechanism and the scientific implementation of quality control. Moreover, in the current market environment, the quality evaluation of Zhenjiang Yaorou still lacks unified and scientific standards and methods. Traditional quality assessment mostly relies on sensory evaluation. Although this method directly reflects the intuitive feelings of consumers, it is easily affected by subjective factors and it is difficult to ensure the objectivity and accuracy of the evaluation.

[0005] Therefore, establishing a screening and discrimination model for the quality of Yaorou is of great significance for the quality evaluation of Zhenjiang Yaorou. Summary of the invention

[0006] In view of the problem that the quality evaluation of Zhenjiang Yaorou lacks unified and scientific standards and methods, the present invention provides a Yaorou quality evaluation method based on flavor substance analysis, which can achieve a comprehensive evaluation of the intrinsic quality of Yaorou, effectively eliminate subjective assumptions, and enhance the reliability and accuracy of the evaluation results.

[0007] In order to achieve the above object, the present invention provides a method for evaluating the quality of braised pork based on flavor substance analysis, comprising the following steps:

[0008] S1. The characteristic flavor substances content of the tested meat was measured, the OAV of the characteristic flavor substances was used as the independent variable, the flavor difference between the tested meat and the representative Zhenjiang meat was used as the dependent variable, and the discriminant model of the tested meat was established by the OPLS-DA method to obtain the VIP value graph and the standardized regression coefficient graph;

[0009] S2. According to the positive and negative correlations of the characteristic flavor substance indicators in the standardized regression coefficient diagram in step S1, and referring to the VIP value diagram to obtain the VIP value as the weight of each characteristic flavor substance indicator, a weighted TOPSIS analysis method improved based on the grey correlation coefficient is adopted to finally obtain a relative closeness value. If the relative closeness value of the tested meat is less than or equal to the relative closeness value of the representative Zhenjiang meat, it is determined that the quality of the tested meat is up to standard; otherwise, it is determined that the quality of the tested meat is not up to standard.

[0010] Orthogonal partial least squares discriminant analysis (OPLS-DA) is the most commonly used analytical method for chemical recognition patterns. It analyzes multiple variables by reducing dimensions, has high prediction accuracy, and the discriminant model score map can be used to identify and distinguish Zhenjiang Yaorou from Yaorou from other origins. The variable importance projection (VIP value) indicates the contribution of the variable to the explanatory power of the model in the OPLS-DA analysis. The larger the VIP value, the greater the contribution of the substance to the flavor of Zhenjiang Yaorou. Among them, VIP>1 indicates that the substance contributes significantly to the flavor of Zhenjiang Yaorou.

[0011] Grey relational analysis (GRA) is a powerful tool for solving complex relationship problems among multiple targets. It can determine which factors are the most influential dominant factors based on the comparison of the correlation between factors. The comprehensive evaluation value of each index is expressed intuitively, avoiding human judgment. The weighted ranking of near ideal solutions (TOPSIS) method can reasonably weight multiple indicators and make a comprehensive evaluation based on the degree of distance from the idealized target. It can avoid the influence of subjective factors on quality evaluation and has good accuracy and scientificity. The multi-target comprehensive evaluation method integrated with weighted TOPSIS based on the improved grey relational coefficient is used to comprehensively evaluate the evaluation targets from two dimensions, horizontal and vertical, which not only eliminates subjective assumptions but also enhances the accuracy of the evaluation results.

[0012] The present invention analyzes the volatile flavor substances in representative Zhenjiang yao meat samples, obtains the types and contents of volatile flavor substances in the Zhenjiang yao meat samples, identifies the contribution of volatile flavor substances to the overall flavor of Zhenjiang yao meat based on the odor activity value (OAV), and screens flavor substances with OAV≥1, which play an important role in the formation of the "yao fragrance" flavor of Zhenjiang yao meat and are the key aroma components of Zhenjiang yao meat. The OPLS-DA method is used to establish a discriminant model of Zhenjiang yao meat and the yao meat to be tested, and a VIP value map and a standardized regression coefficient map are obtained; then, the relative closeness value is finally obtained by combining the weighted TOPSIS analysis method improved based on the grey correlation coefficient, and it is judged whether the quality of the yao meat to be tested meets the standard, which can eliminate subjective assumptions and enhance the accuracy of the evaluation results.

[0013] Specifically, in step S1, the characteristic flavor substances are hexanal, heptanal, nonanal, octanal, (Z)-2-nonenal, eucalyptol, n-hexanol, linalool, 1-octen-3-ol, 1-octene, (+)-limonene, 4-allylanisole and anethole.

[0014] The type screening method of the characteristic flavor substances is as follows:

[0015] The volatile flavor substances in representative Zhenjiang Yaorou were qualitatively and quantitatively analyzed to obtain its flavor information.

[0016] The OAV method was used to evaluate the contribution of each volatile flavor compound to the overall aroma of Zhenjiang Yaorou, and the volatile flavor compounds with OAV≥1 were screened as characteristic flavor compounds.

[0017] Specifically, the qualitative analysis is as follows: referring to the NIST search spectral library, screening out the volatile flavor substances with a forward and reverse matching degree>800 among the detected volatile flavor substances; the quantitative analysis is as follows: adding methyl octanoate-methanol internal standard solution to the braised pork sample before SPME, and calculating the content of each volatile flavor substance in the braised pork sample according to the peak area ratio of the sample peak area and the internal standard peak area.

[0018] Specifically, the OAV method is as follows: according to the odor threshold of the volatile flavor substances in the braised pork sample, the odor activity value is calculated: OAV x =C x / T x , where OAV x is the odor activity value of volatile flavor substance x, C x is the content of volatile flavor substance x in braised pork, T x is the odor threshold of the volatile flavor substance x; the volatile flavor substances with OAV≥1 are screened as characteristic flavor substances for subsequent processing.

[0019] Specifically, in step S1, simca 14.1 software was used to perform OPLS-DA discriminant analysis.

[0020] Specifically, in step S2, the weighted TOPSIS analysis method based on the improvement of grey correlation coefficient is specifically:

[0021] Step 1: Normalization of index values: Take each group of meat as the evaluation object, take the selected characteristic flavor substances as the evaluation index, and take the original data. Suppose there are m evaluation objects and n evaluation indexes. Combined with the positive and negative correlations of the characteristic flavor substance indexes in the standardized regression coefficient diagram, the positive index and the negative index are normalized according to formula (1) (2), and a table is established:

[0022] Positive indicators:

[0023] Negative indicators:

[0024] Where: X ij is the evaluation value of the jth indicator of the ith evaluation object.

[0025] Step 2: Weighted processing of standardized data: refer to the VIP value chart to obtain the VIP value as the weight of each characteristic flavor substance index (Q j ), the weighted calculation formula is formula (3), the weighted decision matrix is ​​obtained, and the optimal value of each indicator is taken as the reference series (Z c ), the positive indicator selects the maximum value of each indicator, and the negative indicator selects the minimum value of each indicator;

[0026] Z ij =Q j ×Y ij (3)

[0027] Step 3: Calculate the correlation coefficient and establish the correlation coefficient matrix: Calculate the correlation coefficient according to formula (4) and establish the correlation coefficient matrix; take each maximum value to establish the positive ideal solution ζ + , take each minimum value to establish the negative ideal solution ζ － ; Then calculate the distance d of each indicator to the positive and negative ideal solutions according to formula (5) (6) i + and d i - ;

[0028]

[0029] Where: i (j) is the correlation coefficient; Δ i (j) = Z cj -Z ij, indicating Z c With Z i The absolute difference at the jth index; ρ is the resolution coefficient, which is 0.5;

[0030]

[0031] Step 4: Calculation of relative closeness: Calculate the relative closeness C according to formula (7): i ,

[0032]

[0033] C i The smaller it is, the closer the evaluation object is to the ideal point, and the higher the quality of the corresponding meat product is.

[0034] In the above step S2, since there are large differences in the indicators of volatile flavor substances, it is necessary to normalize the data to eliminate the dimensional effects of different indicators, so as to facilitate the comparison between indicators. Weight refers to the importance of a certain indicator to a certain thing. Compared with the general proportion, it emphasizes the relative importance of the indicator, which tends to be contribution or importance. Therefore, the VIP value of the characteristic flavor substance in the OPLS-DA analysis is used as the weight of each indicator (Q j ), weighted processing of data can obtain more representative results, which in turn makes the results more applicable and reliable.

[0035] Through the above technical solution, the present invention achieves the following beneficial effects:

[0036] The present invention proposes a method for evaluating the quality of braised pork with asparagus based on the analysis of volatile flavor substances, which can comprehensively evaluate the intrinsic quality of braised pork with asparagus, is targeted and feasible; can more accurately distinguish and differentiate braised pork of different qualities, and at the same time rank their qualities, which can effectively eliminate subjective assumptions, enhance the reliability and accuracy of evaluation results, and obtain scientific and objective evaluation; and can provide a solid scientific theoretical basis for the quality control and protection of geographical indication products. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is the electronic nose radar diagram of each meat product in Example 1 of the present invention;

[0038] Figure 2 This is an overlay of GC-MS spectra of different braised meat products in Example 1 of the present invention;

[0039] Figure 3 is a graph showing the content of volatile flavor substances in different braised meat products in Example 1 of the present invention;

[0040] Figure 4is a cluster analysis heat map of the braised pork product in Example 1 of the present invention;

[0041] Figure 5 This is a replacement inspection diagram of a braised pork product in Example 1 of the present invention;

[0042] Figure 6 is a standardized regression coefficient diagram of volatile flavor substances in the braised pork product in Example 1 of the present invention;

[0043] Figure 7 VIP value diagram of volatile flavor substances of the braised pork product in Example 1 of the present invention;

[0044] Figure 8 VIP value diagram of volatile flavor substances of braised pork product in Example 3 of the present invention;

[0045] Fig. 9 3 is a standardized regression coefficient diagram of volatile flavor substances in the braised pork product in Example 3 of the present invention. DETAILED DESCRIPTION

[0046] The specific implementation of the present invention is described in detail below in conjunction with the examples. It should be understood that the specific implementation described herein is only used to illustrate and explain the present invention, and is not used to limit the present invention.

[0047] In the following examples, the reagents and instruments used were: methyl octanoate (Sigma-Aldrich (Shanghai) Trading Co., Ltd.), methanol (chromatographic grade, Shanghai MacLean Biochemical Co., Ltd.); AL204 electronic balance (Mettler-Toledo Instruments (Shanghai) Co., Ltd.), Tace 1300-ISQ gas chromatograph-mass spectrometer (Thermo Fisher Scientific, USA).

[0048] Example 1 Construction of quality analysis model

[0049] In this embodiment, the vacuum-packed representative Zhenjiang Yaorou were selected and purchased from the two most distinctive brands in Zhenjiang. Brand 1 selected the Zhenjiang time-honored Yanchun (its Yaorou production and processing technology was listed as the "Intangible Cultural Heritage Protection Project" of Zhenjiang City and Jiangsu Province, hereinafter referred to as Product Y), and Brand 2 selected the Jiangsu Province Time-honored Intangible Cultural Heritage Food Committee Member Junzeyuan (its Yaorou production skills are the intangible cultural heritage of Zhenjiang City, and the producer is the inheritor of Zhenjiang Yaorou production skills, hereinafter referred to as Product J). The vacuum-packed Yaorou products to be tested selected Product D (Origin: Weifang) and Product S (Origin: Huai'an). Each brand purchased products of different batches with production dates between 2024.08.01 and 2024.08.30, conducted parallel tests, and averaged the data.

[0050] (1) Odor profile analysis

[0051] Weigh 3.00 g of sample, mince it, place it in a 20 mL headspace bottle and seal it immediately. After incubating it in a 50°C water bath for 20 min, insert the injection needle into the headspace bottle for measurement.

[0052] Electronic nose measurement conditions: collection interval 1 s, cleaning time 120 s, pre-injection time 5 s, measurement time 160 s, gas flow rate 400 mL / min.

[0053] Result analysis: Figure 1 The radar chart of the odor profiles of four kinds of yak meat detected by the electronic nose showed that among the 10 sensors, the two groups of yak meat produced in Zhenjiang (Y and J) had similar odor profiles on nine sensors, including W1C (sensitive to aromatic components benzene), W3S (sensitive to long-chain alkanes), W2W (sensitive to aromatic hydrocarbons and organic sulfur compounds), W2S (sensitive to alcohols, aldehydes and ketones), W1W (sensitive to sulfur-containing compounds, terpenes and pyrazines), W1S (sensitive to methyl), W5C (short-chain alkane aromatic components), W6S (sensitive to hydrides) and W3C (sensitive to ammonia aromatic components), except for the W5S (sensitive to nitrogen oxides) sensor. There were no significant differences in the response intensities of W6S, W2W, W1S, W1W, W2S and W3S (P < 0.05), which indicated that the yak meat produced in Zhenjiang had similar flavor characteristics. In comparison, the two groups of non-Zhenjiang-produced yak meat (D, S) had differences in odor profiles from Zhenjiang-produced yak meat, especially in the response intensities of the electronic nose sensors at W2W, W2S, W1W, W1S, and W5S. The response value of the S sample at W5S (15.05) was the highest (P < 0.05). The response values ​​of the four groups of yak meat samples at W3S were not significantly different (P > 0.05). From the results of the electronic nose, Zhenjiang-produced yak meat and non-Zhenjiang-produced yak meat had different odor profiles and had certain differences in aroma.

[0054] (2) GC-MS spectrum overlay

[0055] Figure 2 This is a superimposed comparison of the GC-MS spectra of volatile flavor substances in yak meat. Although there are corresponding differences in the peak area values ​​and contents of each flavor component between the two groups of representative Zhenjiang yak meat samples, the types of flavor and aroma components are similar, and they all have peaks at similar retention times, which is different from yak meat not produced in Zhenjiang.

[0056] (3) Comparative analysis of volatile substances

[0057] In order to better study the odor characteristics of yak meat, SPME-GC-MS was used to analyze and identify the volatile substances of four yak meats. The volatile flavor substances with a forward and reverse matching degree of >800 were screened out by referring to the NIST search spectral library. A total of 67 volatile flavor compounds were detected in the four yak meat samples, including 8 aldehydes, 12 alcohols, 13 olefins, 11 alkanes, 4 aromatics, 10 esters, and 9 others. Combined with the data results in Table 1, it can be seen that 41 and 40 compounds were detected in yak meat Y and J produced in Zhenjiang, respectively, while 24 and 31 compounds were detected in the other two non-Zhenjiang yak meat samples S and D, respectively. Among them, 11 compounds including hexanal, heptanal, nonanal, 4-terpene alcohol, linalool, α-terpineol, α-pinene, (+)-limonene, ethylbenzene, terpineol acetate, and 4-allyl anisole were the common flavor substances of the four yak meat samples. In addition, 17 compounds including benzaldehyde, octanal, lauryl aldehyde, (Z)-2-nonenal, n-hexanol, 3-furanmethanol, (2Z, 5Z)-2,5-pentadecan-1-ol, α-terpinene, heptane, decamethylcyclopentasiloxane, hexamethylcyclotrisiloxane, hexamethylcyclooctasiloxane, o-isopropyltoluene, methyl palmitate, isopropyl hydrogen trithiocarbonate, piperitone, and methyl heptenone are the unique flavor substances of samples produced in Y and J Zhenjiang. Figure 3 The content of volatile flavor substances in each group of yak meat samples was significantly different (P < 0.05), among which J sample had the highest total content of flavor substances (681.52 μg / kg), followed by Y sample (605.64 μg / kg), and D sample had the lowest total content (209.98 μg / kg). Compared with non-Zhenjiang yak meat (S, D), Zhenjiang yak meat (Y, J) had significantly higher contents of aldehydes, alkanes, and esters (P < 0.05).

[0058] Table 1 Analysis of volatile flavor substances in braised pork

[0059]

[0060]

[0061]

[0062]

[0063]

[0064] The data of volatile substances can be visualized through clustering heat map. Clustering can divide similar sample groups into different groups or subsets through static classification methods. Each grid represents a compound, the color represents the concentration of each substance, and the depth of the color represents the concentration. After clustering analysis, Figure 4As shown, Zhenjiang Yaorou samples Y and J and non-Zhenjiang Yaorou products were divided into two categories, indicating that Zhenjiang Yaorou Y and J had the greatest similarity in volatile flavor substances, and were different from non-Zhenjiang Yaorou.

[0065] (4) Odor activity method

[0066] The OAV method was used to evaluate the contribution of each volatile flavor substance to the overall aroma of Zhenjiang Yaorou, and the odor activity value (OAV) was calculated according to the odor threshold of the volatile flavor substances in the Zhenjiang Yaorou samples. The calculation formula is: OAV x =C x / T x , where OAV x is the odor activity value of volatile flavor substance x, C x is the content of volatile flavor substance x in Zhenjiang Yaorou, T x is the odor threshold of volatile flavor substance x.

[0067] The OAV of the main volatile flavor substances of Zhenjiang Yaorou was calculated according to the threshold of the compounds in the Compilation of Olfactory Thresholds of Compounds. The results showed that there were 13 volatile flavor substances with OAV values ​​≥ 1, as shown in Table 2. These substances play an important role in the formation of the "Yaoxiang" flavor of Zhenjiang Yaorou and are the key aroma components of Zhenjiang Yaorou. The 13 volatile flavor substances with OAV ≥ 1 were screened as characteristic flavor substances for subsequent processing.

[0068] Table 2 Odor activity values ​​(OAV) of main volatile substances in braised pork

[0069]

[0070]

[0071] Note: The table selects the volatile flavor compounds with OAV>1 in braised pork.

[0072] (5) SIMCA 14.1 software was used to perform orthogonal partial least squares discriminant analysis (OPLS-DA) and calculate the predictor importance projection (VIP).

[0073] The content of characteristic flavor substances was taken as the independent variable, and the flavor differences between non-representative yak meat samples S and D and representative Zhenjiang yak meat samples Y and J were taken as the dependent variable. Orthogonal partial least squares discriminant analysis was performed to establish the OPLS-DA discriminant model, VIP value graph and standardized regression coefficient graph, as shown in the figure below. Figure 5-Figure 7 shown.

[0074] In this analysis, the independent variable fit index and the dependent variable fit index are: R 2 X =1, R 2y =0.994, the model prediction index is: Q 2 =0.982. Usually R 2 and Q 2 When the value is greater than 0.5, the model fitting result is considered reliable and acceptable. Figure 5 , after 200 permutation tests, the R on the far right 2 , Q 2 The values ​​are higher than the left side, and Q 2 The point where the regression line intersects the vertical axis is less than zero, indicating that the model is not overfitted and the model verification results are valid.

[0075] The VIP value indicates the contribution of the variable to the explanatory power of the model in the OPLS-DA analysis, that is, the larger the VIP value, the greater the influence of the variable on the model. Figure 7 As shown in Figure 2, among the 13 volatile compounds with OVA≥1, there are 4 volatile compounds with VIP≥1, namely: linalool, (Z)-2-nonenal, hexanal, and eucalyptol. These compounds contribute greatly to the flavor of Zhenjiang yao meat. Figure 6 The results show that among the 13 characteristic flavor substances with OAV≥1, 9 compounds (namely hexanal, heptanal, nonanal, octanal, (Z)-2-nonenal, eucalyptol, n-hexanol, 1-octen-3-ol, and 1-octene) are positively correlated with the flavor of Zhenjiang yao meat; and 4 compounds (namely (+)-limonene, 4-allylanisole, anethole, and linalool) are negatively correlated with the flavor of Zhenjiang yao meat.

[0076] (6) The weighted TOPSIS analysis method improved based on the grey correlation coefficient is used to finally obtain the relative closeness value.

[0077] (6.1) Data normalization

[0078] Function: Due to the large differences among flavor indicators, it is necessary to normalize the data to eliminate the dimensional influence of different indicators and facilitate the comparison between indicators.

[0079] Based on the 13 odor active substances in Zhenjiang Yao meat, each group was taken as the evaluation object, and the 13 characteristic flavor substances were taken as the evaluation indicators. The contents of each indicator in two groups of Zhenjiang Yao meat and two groups of non-Zhenjiang Yao meat were taken as the original data (as shown in Table 3). Combined with the positive and negative correlation of the correlation coefficient, the positive and negative indicators were normalized according to formulas (1) (2) (as shown in Table 4).

[0080] Positive indicators:

[0081] Negative indicators:

[0082] In the formula

[0083] X ij is the value of the jth indicator of the ith sample.

[0084] Table 3. Raw data

[0085]

[0086]

[0087] Table 4 Normalization results of data

[0088] Y J D S Hexanal 1 0 0.01 0.01 Heptanal 1 0.16 0 0.02 Nonanal 0.60 1 0.04 0 Octanal 1 0.32 0.01 0 (Z)-2-Nonenal 0.56 1 0 0 Eucalyptol 1 0 0 0 n-Hexanol 1 0.01 0 0 Linalool 0.78 0 1 0.82 1-Octen-3-ol 1 0 0 0 1-Octene 1 0 0 0 (+)-Limonene 0.87 1 0.37 0 4-Allylanisole 0.88 0 1 0.88 Anethole 0.77 0 0.78 1

[0089] (6.2) Weighted processing of standardized data

[0090] Function: Weight refers to the importance of a certain indicator to a certain thing. Compared with the general proportion, it emphasizes the relative importance of the indicator, which tends to be contribution or importance. Weighted processing of data can obtain more representative results.

[0091] The VIP values ​​of the 13 odor activity indices in the OPLS-DA analysis were used as the weights of each index (Q j ), the weighted calculation formula is formula (3), and the weighted decision matrix is ​​obtained (as shown in Table 5). The optimal value of each indicator is taken as the reference series (Zc).

[0092] Z ij =Q j ×Y ij (3)

[0093] Table 5 Weighted decision matrix

[0094]

[0095] (6.3) Calculation of correlation coefficient and establishment of correlation coefficient matrix

[0096] Calculate the correlation coefficient according to formula (4) and establish the correlation coefficient matrix. Take each maximum value to establish the positive ideal solution ξ + , take each minimum value to establish the negative ideal solution ξ - , as shown in Table 6.

[0097] Table 6 Correlation coefficient matrix

[0098]

[0099]

[0100] (6.4) Calculation of closeness

[0101] According to formula (5) (6), the distance d of each indicator to the positive and negative ideal solutions is calculated. + and d - :

[0102]

[0103] Where: Δ i (j) = Z cj -Z ij

[0104] ρ is the resolution coefficient, which is 0.5.

[0105]

[0106] The relative closeness is calculated according to formula (7). The smaller C is, the closer the research object is to the ideal point.

[0107]

[0108] C i The smaller it is, the closer the evaluation object is to the ideal point, and the higher the quality of the corresponding meat product is.

[0109] The quality ranking of each group of yam meat samples is shown in Table 7. As can be seen from Table 7, the relative closeness C of the representative Zhenjiang yam meat samples Y and J is i The values ​​are 0.45 and 0.5 respectively, with an average value of 0.475, while the relative closeness C of the non-representative braised pork samples S and D is i The values ​​are much higher than that of the other two. The ranking of the quality of braised pork products is Y, J, S, and D. The non-representative braised pork samples S and D are not produced in Zhenjiang and have lower scores, which are obviously different from the quality of the representative Zhenjiang braised pork samples Y and J.

[0110] Table 7 Quality ranking of each group of braised pork samples

[0111]

[0112] Example 2 Verification of the quality analysis model

[0113] The quality analysis model of Example 1 was verified using fuzzy mathematical sensory evaluation.

[0114] 1. Establishment of fuzzy mathematical model

[0115] 1.1 Establishment of factor set, comment set and weighted set

[0116] The factors of this study are the color (U1), taste (U2), appearance (U3), aroma (U4), and overall acceptance (U5) of braised pork, as shown in Table 8, thus obtaining the factor set of braised pork U = {U1, U2, U3, U4, U5}.

[0117] Table 8 Sensory indexes of braised meat

[0118]

[0119] The sensory evaluation of products Y, J, S, and D is as follows:

[0120] Table 9 Sensory evaluation scores of products Y, J, S, and D

[0121]

[0122] The review grades of braised pork are excellent (V1), good (V2), medium (V3), and poor (V4), and the review set V = {V1, V2, V3, V4} is obtained. The review sets of products Y, J, S, and D are shown in Table 10.

[0123] Table 10 Review set of products Y, J, S, and D

[0124]

[0125]

[0126] Taking the color of sample Y as an example, 6 people rated 9-10 points, 3 people rated 6-8 points, 1 person rated 3-5 points, and 0 people rated 0-2 points, then we can get U1 = {0.6, 0.3, 0.1, 0}, and similarly, U2 = {0.8, 0.2, 0, 0}; U3 = {0.7, 0.3, 0, 0}; U4 = {0.8, 0.2, 0, 0}; U5 = {0.9, 0.1, 0, 0}. The evaluation results of the five single-factor fuzzy matrices U1, U2, U3, U4, and U5 are combined into a matrix, that is:

[0127]

[0128] Similarly, we can get:

[0129]

[0130] It is known that the weight vector of the five indicators of braised pork is X = {0.1, 0.25, 0.2, 0.25, 0.2}. According to the formula Y = X × R, the evaluation result of the Y sample is obtained:

[0131]

[0132] Similarly, we can get Y J={0.79,0.135,0.075,0}, Y S ={0.585,0.22,0.195,0}, Y D ={0.485,0.23,0.26,0}

[0133] According to the formula D = Y × K, the Y of the Y sample Y ={0.78,0.21,0.01,0} and the evaluation level set K ={9,7,4,1}, the calculation results show that: the comprehensive score of sample Y is:

[0134] Similarly, we can get D J =8.355, D S =7.585, D D =7.015

[0135] The higher the comprehensive score of the sample, the better the sensory evaluation, and the lower the score, the worse the sensory evaluation. This result is basically consistent with the result calculated by the model.

[0136] Example 3 Quality evaluation of braised pork products

[0137] Products Y and J were selected for vacuum-packed braised pork produced in Zhenjiang, and products N (origin: Nanjing) and H (origin: Zhenjiang) were selected for vacuum-packed braised pork produced outside Zhenjiang. The quality evaluation steps for products N and H are as follows:

[0138] The content of flavor substances was measured as follows:

[0139] Table 11 Results of the measurement of volatile flavor substances in braised pork products

[0140]

[0141]

[0142] Taking the odor activity value (OAV) of characteristic flavor substances as the independent variable and the flavor difference between the tested yak meat samples H and N and the representative Zhenjiang yak meat samples Y and J as the dependent variable, orthogonal partial least squares discriminant analysis was performed to establish the VIP value diagram and standardized regression coefficient diagram of the tested yak meat, as shown in the figure below. Figure 8 and Fig. 9 shown.

[0143] The four groups of yak meat Y, J, H and N were used as evaluation objects, and the 13 characteristic flavor substances screened out were used as evaluation indicators. As the original data, there were 4 evaluation objects and 13 evaluation indicators, as shown in Table 13. Combined with the above standardized regression coefficient diagram ( Fig. 9) in the sample, the positive and negative correlations of the characteristic flavor substance indexes were normalized according to formula (1) (2), and a table was established, as shown in Table 12:

[0144] Table 12 Data standardization results

[0145]

[0146]

[0147] Refer to the VIP value chart to obtain the VIP value as the weight of each characteristic flavor substance index (Q j ), the weighted calculation formula is formula (3), and the weighted decision matrix is ​​obtained, as shown in Table 13. The optimal value of each indicator is taken as the reference series (Z c );

[0148] Table 13 Weighted decision matrix

[0149] Y J H N <![CDATA[Z C ]]> Hexanal 1.13 0 0.14 0.03 1.13 Heptanal 0.46 0.08 0 0.03 0.46 Nonanal 0.34 0.66 0 0.01 0.66 Octanal 0.85 0.28 0 0.34 0.85 (Z)-2-Nonenal 0.7 1.26 0 0 1.26 Eucalyptol 1.93 2.22 0 2.22 0 n-Hexanol 0.34 0.01 0 0.11 0.34 Linalool 1.37 0 1.78 1.36 0 1-Octen-3-ol 0.47 0 0 0.07 0.47 1-Octene 0.47 0 0 0 0.47 (+)-Limonene 0.13 0.1 0 0.07 0.13 4-Allylanisole 0.18 0 0.16 0.17 0 Anethole 0.23 0 0.17 0.24 0

[0150] The correlation coefficient is calculated according to formula (4), and the correlation coefficient matrix is ​​established, as shown in Table 14. Each maximum value is taken to establish the positive ideal solution ζ + , take each minimum value to establish the negative ideal solution ζ － ;

[0151] Table 14 Correlation coefficient matrix

[0152]

[0153]

[0154] Then, according to formula (5) (6), the distance d of each indicator to the positive and negative ideal solutions is calculated. + and d - , the relative closeness C is calculated according to formula (7), and the results are shown in Table 15.

[0155] Table 15: Samples of braised pork in each group + ,d - The calculation results of and C

[0156] <![CDATA[d + ]]> <![CDATA[d - ]]> <![CDATA[C i ]]> Y 0.96 0.91 0.51 J 1.05 0.93 0.53 H 1.25 0.67 0.65 N 1.35 0.16 0.89

[0157] It can be seen from Table 15 that the average C value of product Y and product J is 0.52, and the C values ​​of product H and product N are both higher than the average value. Therefore, product H and product N are both substandard products.

[0158] The preferred implementation modes of the present invention are described in detail above in combination with the embodiments; however, the present invention is not limited to the specific details in the above implementation modes. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical scheme of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0159] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0160] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A method for evaluating the quality of braised pork based on flavor substance analysis, characterized in that: The steps include: S1. The characteristic flavor substances content of the tested meat was measured, the OAV of the characteristic flavor substances was used as the independent variable, the flavor difference between the tested meat and the representative Zhenjiang meat was used as the dependent variable, and the discriminant model of the tested meat was established by the OPLS-DA method to obtain the VIP value graph and the standardized regression coefficient graph; S2. According to the positive and negative correlations of the characteristic flavor substance indicators in the standardized regression coefficient diagram in step S1, and referring to the VIP value diagram to obtain the VIP value as the weight of each characteristic flavor substance indicator, a weighted TOPSIS analysis method improved based on the grey correlation coefficient is adopted to finally obtain a relative closeness value. If the relative closeness value of the tested meat is less than or equal to the relative closeness value of the representative Zhenjiang meat, it is determined that the quality of the tested meat is up to standard; otherwise, it is determined that the quality of the tested meat is not up to standard.

2. The method for evaluating the quality of braised pork according to claim 1, characterized in that: In step S1, the characteristic flavor substances are hexanal, heptanal, nonanal, octanal, (Z)-2-nonenal, eucalyptol, n-hexanol, linalool, 1-octen-3-ol, 1-octene, (+)-limonene, 4-allylanisole and anethole.

3. The method for evaluating the quality of braised pork according to claim 2, characterized in that: The type screening method of the characteristic flavor substances is as follows: The volatile flavor substances in representative Zhenjiang Yaorou were qualitatively and quantitatively analyzed to obtain its flavor information. The OAV method was used to evaluate the contribution of each volatile flavor compound to the overall aroma of Zhenjiang Yaorou, and the volatile flavor compounds with OAV≥1 were screened as characteristic flavor compounds.

4. The method for evaluating the quality of braised pork according to claim 3, characterized in that: The qualitative analysis method is: referring to the NIST search spectral library, screening out the volatile flavor substances with a forward and reverse matching degree>800 among the detected volatile flavor substances; the quantitative analysis method is: adding methyl octanoate-methanol internal standard solution to the braised pork sample before SPME, and calculating the content of each volatile flavor substance in the braised pork sample according to the peak area ratio of the sample peak area and the internal standard peak area.

5. The method for evaluating the quality of braised pork according to claim 3, characterized in that: The OAV method is as follows: according to the odor threshold of the volatile flavor substances in the braised pork sample, the odor activity value is calculated: OAV x =C x / T x , where OAV x is the odor activity value of volatile flavor substance x, C x is the content of volatile flavor substance x in braised pork, T x is the odor threshold of volatile flavor substance x; screening OAV x The volatile flavor substances with a value ≥1 are characteristic flavor substances.

6. The method for evaluating the quality of braised pork according to claim 1, characterized in that: In step S2, the weighted TOPSIS analysis method improved based on grey correlation coefficient is specifically: Step 1: Normalization of index values: Taking each group of meat as the evaluation object, the selected characteristic flavor substances as the evaluation index, and the content of each characteristic flavor substance as the original data, assuming that the number of evaluation objects is m and the number of evaluation indexes is n, and combining the positive and negative correlations of the characteristic flavor substance indexes in the standardized regression coefficient diagram, the positive index and the negative index are normalized according to formula (1) (2), and a table is established: Positive indicators: Negative indicators: Where: X ij is the evaluation value of the jth indicator of the ith evaluation object. Step 2: Weighted processing of standardized data: refer to the VIP value chart and use the obtained VIP value as the weight of the characteristic flavor substance index (Q j ), the weighted calculation formula is formula (3), the weighted decision matrix is ​​obtained, and the optimal value of each indicator is taken as the reference series (Z c ); Z ij =Q j ×Y ij (3) Step 3: Calculate the correlation coefficient and establish the correlation coefficient matrix: Calculate the correlation coefficient according to formula (4) and establish the correlation coefficient matrix; take each maximum value to establish the positive ideal solution ζ + , take each minimum value to establish the negative ideal solution ζ － ; Then calculate the distance d of each indicator to the positive and negative ideal solutions according to formula (5) (6) i + and d i - ; Where: i (j) is the correlation coefficient; Δ i (j)=|Z cj -Z ij |, indicating Z c With Z i The absolute difference at the jth index; ρ is the resolution coefficient, which is 0.5; Step 4: Calculation of relative closeness: Calculate the relative closeness C according to formula (7): i , C i The smaller it is, the closer the evaluation object is to the ideal point, and the higher the quality of the corresponding meat product is.

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