Method for realizing ham quality grading based on non-volatile flavor substance analysis

Abstract

The application relates to a method for realizing ham quality grading based on non-volatile flavor substance analysis, and relates to the field of ham quality grading methods. The application solves the problem that the existing Xuanwei ham fermentation process is not standardized and the fermentation process cannot be adjusted according to the content of non-volatile compounds and the change rule of overall taste. Method: I. Taking naturally fermented mature Xuanwei ham, cutting off the oxidation layer, and quickly separating the biceps femoris and semimembranosus; II. Amino acid determination is carried out on the separated biceps femoris and semimembranosus, and ham quality is graded according to the test data. The application realizes accurate evaluation of Xuanwei ham quality through amino acid analysis. The application is used for Xuanwei ham quality grading.

Description

Technical Field

[0001] This invention relates to the field of methods for grading the quality of ham. Background Technology

[0002] Xuanwei ham is a traditional and famous meat product from Xuanwei City, Yunnan Province, China. Due to its unique sensory characteristics, such as flavor and texture, it has gained high recognition among consumers. Xuanwei ham, along with Rugao ham from Jiangsu Province and Jinhua ham from Zhejiang Province, is hailed as one of the "Three Great Hams of China." The flavor compounds in dry-cured ham refer to compounds or components that help enhance and improve its taste and aroma. Some reports indicate that many non-volatile metabolites belong to the flavor compounds in meat products. The flavor compounds in ham mainly include oligopeptides produced by protein hydrolysis, free amino acids, organic acids, and mineral ions. The flavor of ham is not a simple superposition and accumulation of these flavor compounds, but rather a complex mixture of these substances in a certain proportion. Current research has clarified that free amino acids are closely related to the formation of the flavor in dry-cured ham, are one of the main components of its flavor compounds, and are also important precursors for the umami, sweetness, sourness, and bitterness of dry-cured ham. Organic acids are important components of the flavor compounds in ham. They can enrich the flavor of cured ham, and high levels can give it a pronounced sour taste. However, their flavor characteristics in cured ham depend on their concentration. Biogenic amines, nitrogen-containing organic compounds, are commonly detected in fermented foods with relatively high protein content. The production of biogenic amines in fermented meat products is attributed to the action of decarboxylases from several microorganisms. These enzymes promote the decarboxylation of free amino acids, and because the microbial community is dominant in ham fermentation, they are more prone to amine decarboxylation.

[0003] Chen et al. used high-throughput sequencing technology to investigate the physicochemical properties, biogenic amine concentration, and microbial diversity during the processing of Sanchuan ham, analyzing the dynamic correlation between physicochemical properties, free amino acid content, biogenic amine concentration, and microbial diversity during the fermentation process of Sanchuan ham. Landeta et al. found that tyramine and putrescine were the most abundant biogenic amines in Italian cured ham. WANG et al. studied the microbial community and volatile compounds in the biceps femoris (BF) and semimembranosus (SM) muscles of normal and spoiled Xuanwei ham, analyzing the correlation between microorganisms and volatile compounds, and clarifying the relationship between the Xuanwei ham microbial community and off-flavor formation. Alfaia et al. assessed the characteristics of biogenic amines in Portuguese cured ham, finding that spermine and cadaverine were often present in large quantities, while histamine and spermidine were usually present in lower amounts. However, existing studies lack the ability to monitor the quality of different grades of Xuanwei ham through non-volatile compounds.

[0004] Mature Xuanwei ham is graded into four levels using a "three-skewer" method, which assesses the intensity of the aroma by smelling bamboo skewers. Ham exhibiting a strong meaty aroma in all three designated areas is classified as superior (Grade A). Ham exhibiting a strong meaty aroma in two designated areas, with no off-odors in the remaining areas, is classified as first-grade (Grade B). Ham exhibiting a strong meaty aroma in one designated area and no off-odors in the other two is classified as acceptable (Grade C). Finally, ham considered rotten (Grade D) is identified by the presence of a strong foul odor in one of the three designated areas. However, traditional sensory evaluation is highly subjective and difficult to categorize precisely. Summary of the Invention

[0005] This invention provides a method for grading the quality of ham based on the analysis of non-volatile flavor compounds, in order to solve the problem that the existing fermentation process of Xuanwei ham is not standardized and cannot be adjusted according to the content of non-volatile compounds and the overall flavor variation.

[0006] A method for grading the quality of ham based on the analysis of non-volatile flavor compounds is specifically carried out according to the following steps:

[0007] 1. Take naturally fermented and matured Xuanwei ham, cut off the oxidized layer, and quickly separate the biceps femoris muscle and semimembranosus muscle;

[0008] 2. The biceps femoris and semimembranosus muscles separated in step 1 were subjected to amino acid analysis. The biceps femoris muscle was denoted by BF and the semimembranosus muscle by SM. The quality of the ham was graded according to the total amino acid content or the umami amino acid content, and divided into grade A, grade B, grade C and grade D from high to low.

[0009] Furthermore, the Grade A quality mentioned in step two is as follows: the total amino acid content of the BF fraction is ≥4650mg / 100g, and the total amino acid content of the SM fraction is ≥4437mg / 100g.

[0010] Grade B quality: The total amino acid content of BF part is ≥3997mg / 100g and <4650mg / 100g, and the total amino acid content of SM part is ≥3856mg / 100g and <4437mg / 100g.

[0011] Grade C quality: The total amino acid content of the BF part is ≥3023mg / 100g and <3997mg / 100g, and the total amino acid content of the SM part is ≥2726mg / 100g and <3856mg / 100g.

[0012] Grade D quality: Total amino acid content of BF portion <3023mg / 100g, total amino acid content of SM portion <2726mg / 100g.

[0013] Furthermore, the Grade A quality mentioned in step two is as follows: the umami amino acid content in the BF part is ≥798mg / 100g, and the umami amino acid content in the SM part is ≥749mg / 100g.

[0014] Grade B quality: The umami amino acid content of BF part is ≥677mg / 100g and <798mg / 100g, and the umami amino acid content of SM part is ≥625mg / 100g and <749mg / 100g.

[0015] Grade C quality: The umami amino acid content of BF part is ≥480mg / 100g and <677mg / 100g, and the umami amino acid content of SM part is ≥438mg / 100g and <625mg / 100g.

[0016] Grade D quality: BF portion contains <480mg / 100g of umami amino acids, SM portion contains <438mg / 100g of umami amino acids.

[0017] Furthermore, if the test values ​​for the BF and SM areas fall into different levels, the lower level shall prevail.

[0018] Furthermore, total amino acids include bitter amino acids, umami amino acids, sweet amino acids, and tasteless amino acids.

[0019] Furthermore, umami amino acids include aspartic acid and glutamic acid.

[0020] Furthermore, bitter amino acids include histidine, arginine, tyrosine, valine, methionine, phenylalanine, isoleucine, and leucine.

[0021] Furthermore, the sweet amino acids include serine, glycine, threonine, alanine, proline, and lysine; the tasteless amino acid is cysteine.

[0022] Furthermore, the Xuanwei ham is produced according to the following steps:

[0023] S1. Remove blood stains and dirt from fresh pork leg meat, then cut and shape it to obtain leg embryos;

[0024] S2. The leg embryos treated in S1 are salted four times. After each salting, the salted leg embryos are stacked and turned over. The total amount of salt is controlled to be 9-14% of the weight of the leg embryos. The total salting time is two months.

[0025] S3. Rinse the ham after S2 to remove the surface salt, then air dry until there is no moisture on the surface, and then hang it in the fermentation room for natural fermentation to obtain naturally fermented and matured Xuanwei ham.

[0026] Furthermore, the natural fermentation described in S3 takes 360–380 days.

[0027] Even under the same conditions during the processing of dry-cured ham, the biceps femoris (BF) and semimembranosus (SM) muscles can exhibit differences. The internal muscle BF shows higher water content and proteolytic activity during production than SM. This results in different amounts of non-volatile compounds in BF and SM.

[0028] One of the most important biochemical reactions during ham maturation is protein degradation caused by the activity of endogenous muscle proteases, primarily calpain, cathepsin, dipeptidase, and aminopeptidase. Based on their cleavage sites on proteins and polypeptides, these enzymes are classified as endopeptidases and exopeptidases. Endopeptidases, mainly calpain and cathepsin, participate in the initial breakdown of sarcoplasmic and myofibrillar proteins by cleaving myofibrillar proteins. Exopeptidases (dipeptidase and aminopeptidase) continue to degrade proteins, mainly producing small peptides and free amino acids. The variation in free amino acid content depends on their formation and degradation during the dry-curing ham production process. Some free amino acids directly enhance the ham flavor, while others serve as precursors in dry-cured meat products, participating in the formation of key aroma compounds. The umami flavor of cured ham is closely related to its glutamic acid and aspartic acid content, while leucine, phenylalanine, isoleucine, valine, and methionine are considered closely associated with bitterness. However, excessive accumulation of free amino acids can lead to unpleasant bitterness and sourness.

[0029] This invention analyzes the biceps femoris and semimembranosus muscles in Xuanwei ham, enabling precise quality grading of Xuanwei ham. Principal component analysis establishes an intrinsic correlation between these components and product quality, providing theoretical support for quality control of Xuanwei ham and laying a foundation for its industrialization and commercialization.

[0030] Beneficial effects of this invention:

[0031] 1. This invention achieves accurate quality assessment of Xuanwei ham through amino acid analysis. Compared with traditional single-indicator detection methods, it can more comprehensively reflect the flavor characteristics, safety, and processing maturity of the ham, effectively avoiding misjudgments caused by the limitations of the indicators.

[0032] 2. Precise grading and spoilage warning: Based on amino acid analysis, it can quickly distinguish between Grade A (superior), Grade B (first grade), Grade C (qualified), and Grade D (spoiled ham), with a particularly significant improvement in the sensitivity of identifying spoiled products (such as Grade D).

[0033] 3. High-efficiency and convenient industrial application potential: The present invention adopts standardized detection techniques, with good repeatability and convenient operation of the method, and can be connected to the quality control link of the production line. By monitoring the dynamic changes of key indicators (such as moisture content, salt gradient), it guides enterprises to adjust the pickling and drying process parameters, shortening the production cycle and reducing energy consumption.

[0034] 4. Scientific support for quality improvement and standardization: Establish a quality evaluation system based on the content index of non-volatile compounds, providing an objective and quantitative standard for the grade classification of Xuanwei ham, and promoting the standardization process of the industry.

[0035] The present invention is used to achieve the quality grading of Xuanwei ham. Brief Description of the Drawings

[0036] Figure 1 It is the electronic tongue analysis diagram of different muscle parts of Xuanwei ham with different grades;

[0037] Figure 2 It is the PCA diagram of the electronic tongue of different muscle parts of Xuanwei ham with different grades;

[0038] Figure 3 It is the correlation PCA diagram of different muscle parts of Xuanwei ham with different grades. Detailed Embodiments

[0039] Detailed Embodiment 1: A method for achieving ham quality grading based on the analysis of non-volatile flavor substances in this embodiment is specifically carried out according to the following steps:

[0040] 1. Take naturally fermented and mature Xuanwei ham, cut off the oxidized layer, and quickly separate the biceps femoris and semimembranosus muscles;

[0041] 2. Measure the amino acids of the biceps femoris and semimembranosus muscles separated in step 1 respectively. Set the biceps femoris to be represented by BF and the semimembranosus to be represented by SM. Grade the ham quality according to the total amino acid content or the content of umami amino acids, and divide it into grade A, grade B, grade C, and grade D from high to low.

[0042] Detailed Embodiment 2: The difference between this embodiment and Detailed Embodiment 1 is that for the grade A quality described in step 2: the total amino acid content of the BF part ≥ 4650 mg / 100 g, and the total amino acid content of the SM part ≥ 4437 mg / 100 g;

[0043] For the grade B quality: the total amino acid content of the BF part ≥ 3997 mg / 100 g and < 4650 mg / 100 g, and the total amino acid content of the SM part ≥ 3856 mg / 100 g and < 4437 mg / 100 g;

[0044] Grade C quality: The total amino acid content of the BF part is ≥3023mg / 100g and <3997mg / 100g, and the total amino acid content of the SM part is ≥2726mg / 100g and <3856mg / 100g.

[0045] Grade D quality: Total amino acid content in the BF fraction < 3023 mg / 100g, and total amino acid content in the SM fraction < 2726 mg / 100g. Other aspects are the same as in Specific Implementation Method 1.

[0046] Specific Implementation Method 3: This implementation method differs from Specific Implementation Method 1 or 2 in that: the Grade A quality mentioned in step 2 is: the umami amino acid content of the BF part is ≥798mg / 100g, and the umami amino acid content of the SM part is ≥749mg / 100g;

[0047] Grade B quality: The umami amino acid content of BF part is ≥677mg / 100g and <798mg / 100g, and the umami amino acid content of SM part is ≥625mg / 100g and <749mg / 100g.

[0048] Grade C quality: The umami amino acid content of BF part is ≥480mg / 100g and <677mg / 100g, and the umami amino acid content of SM part is ≥438mg / 100g and <625mg / 100g.

[0049] Grade D quality: umami amino acid content in the BF portion <480mg / 100g, and umami amino acid content in the SM portion <438mg / 100g. Other aspects are the same as in specific implementation methods one or two.

[0050] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that if the test values ​​for the BF and SM areas fall into different levels, the lower level shall prevail. Otherwise, it is the same as Specific Implementation Methods One to Three.

[0051] Specific Implementation Method Five: This implementation method differs from Specific Implementation Methods One to Four in that the total amino acids include bitter amino acids, umami amino acids, sweet amino acids, and tasteless amino acids. Everything else is the same as in Specific Implementation Methods One to Four.

[0052] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One to Five in that the umami amino acids include aspartic acid and glutamic acid. Everything else is the same as in Specific Implementation Methods One to Five.

[0053] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods One to Six in that the bitter amino acids include histidine, arginine, tyrosine, valine, methionine, phenylalanine, isoleucine, and leucine. Everything else is the same as in Specific Implementation Methods One to Six.

[0054] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Methods One to Seven in that: the sweet-tasting amino acids include serine, glycine, threonine, alanine, proline, and lysine; the tasteless amino acid is cysteine. Everything else is the same as in Specific Implementation Methods One to Seven.

[0055] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Methods One through Eight in that the Xuanwei ham is produced according to the following steps:

[0056] S1. Remove blood stains and dirt from fresh pork leg meat, then cut and shape it to obtain leg embryos;

[0057] S2. The leg embryos treated in S1 are salted four times. After each salting, the salted leg embryos are stacked and turned over. The total amount of salt is controlled to be 9-14% of the weight of the leg embryos. The total salting time is two months.

[0058] S3. Rinse the cured ham from S2 to remove surface salt, then air-dry until the surface is dry. Hang it in a fermentation room for natural fermentation to obtain naturally fermented Xuanwei ham. Other steps are the same as in specific implementation methods one through eight.

[0059] Specific Implementation Method Ten: This implementation method differs from Specific Implementation Methods One to Nine in that the natural fermentation described in S3 takes 360 to 380 days. Everything else is the same as in Specific Implementation Methods One to Nine.

[0060] The scope of this invention is not limited to the above-described embodiments; a combination of one or more specific embodiments can also achieve the purpose of the invention.

[0061] Example 1:

[0062] This embodiment describes a method for grading ham quality based on the analysis of non-volatile flavor compounds. The ham used is Xuanwei ham, which is prepared using the following steps:

[0063] S1. Remove blood stains and dirt from fresh pork leg meat, then cut and shape it to obtain leg embryos;

[0064] S2. The leg embryos treated in S1 are salted four times. After each salting, the salted leg embryos are stacked and turned over. The total amount of salt is controlled to be 11% of the weight of the leg embryos. The total salting time is two months.

[0065] S3. Rinse the ham after S2 curing to remove surface salt, then air dry until there is no moisture on the surface, and then hang it in the fermentation room for natural fermentation to obtain naturally fermented and matured Xuanwei ham, which takes about 12 months to fully ferment.

[0066] In Example 1, all processes were completed at Dehe Co., Ltd. in Xuanwei City, Yunnan Province.

[0067] Example 2:

[0068] This embodiment describes a method for grading the quality of ham based on the analysis of non-volatile flavor compounds, including the following steps:

[0069] 1. Take naturally fermented and matured Xuanwei ham, cut off the oxidized layer, and quickly separate the biceps femoris muscle and semimembranosus muscle;

[0070] 2. The biceps femoris and semimembranosus muscles separated in step 1 were subjected to amino acid analysis. The biceps femoris muscle was denoted by BF and the semimembranosus muscle by SM. The quality of the ham was graded according to the total amino acid content or the umami amino acid content, and divided into grade A, grade B, grade C and grade D from high to low.

[0071] Example 3:

[0072] Six hams were randomly selected from the same batch of Xuanwei hams produced using the "three-signature" grading method (Superior Grade A, Grade B, Qualified Grade C, and Deteriorated Grade D). The oxidized layer (approximately 0.5 cm) of the Xuanwei hams was removed. Subsequently, the biceps femoris (BF) and semimembranosus (SM) muscles were rapidly separated to prepare samples for analysis of amino acids, nucleotides, organic acids, and electronic tongue.

[0073] The amino acids include, but are not limited to, tartaric acid, malic acid, lactic acid, glacial acetic acid, citric acid and succinic acid; eight bitter amino acids (histidine, arginine, tyrosine, valine, methionine, phenylalanine, isoleucine and leucine); two umami amino acids (aspartic acid and glutamic acid); six sweet amino acids (serine, glycine, threonine, alanine, proline and lysine); and one tasteless amino acid (cysteine).

[0074] Nucleotides include, but are not limited to, AMP, GMP, and IMP.

[0075] Organic acids include, but are not limited to, tartaric acid, malic acid, lactic acid, glacial acetic acid, citric acid, and succinic acid.

[0076] Electronic tongue detection includes, but is not limited to, salty, umami, bitter, astringent, sour, and richness of flavors.

[0077] Materials and reagents

[0078] Trichloroacetic acid; Standards: lactic acid, tartaric acid, malic acid, citric acid, succinic acid, acetic acid, mixed amino acid standard solution, 17 single amino acid standards, 9 biogenic amine mixed standards, etc., were all purchased from Beijing Solarbio Science & Technology Co., Ltd.; Nucleotide standards were purchased from Shanghai Yuanye Biotechnology Co., Ltd.

[0079] Instruments and equipment

[0080] Electronic balance (AL204), Mettler Toledo Instruments, Inc.; homogenizer (XHF-DY), Ningbo Xinzhi Biotechnology Co., Ltd.; high performance liquid chromatograph (1260Infinity), Agilent Technologies Inc.

[0081] Experimental methods

[0082] 1. Electronic tongue assay: Take 5g of sample, chop it and mix it with 100mL of ultrapure water. Homogenize in an ice bath at 10000r / min for 30s (10s / time, 3 times in total). Let stand for 30min. Filter the suspension with filter paper, and then centrifuge the collected filtrate at 8000r / min for 10min at 4℃. After centrifugation, filter the supernatant again with filter paper. Then, analyze the umami, saltiness, sourness, richness, and bitterness of the sample using an electronic tongue. Each treatment is set up in duplicate, and each duplicate is repeated 6 times. Three data points are selected as raw data for analysis.

[0083] 2. Determination of Organic Acids: 5.0 g of ham sample was homogenized in 25 mL of purified water for 5 min; then centrifuged at 10000 g for 20 min at 4 °C. Before injection, the supernatant was filtered through a 0.45 μm water membrane. Agilent high-performance liquid chromatography (HPLC) and an Agilent ZORBAX SB-C18 analytical column were used. 0.1% phosphoric acid was used as phase A, with methanol (phase B) as the main component, in proportions of 97.5% and 2.5%, respectively. The following HPLC parameters were followed: sample volume set to 20 μL; flow rate set to 1.0 mL / min; operating temperature set to 30 °C; and detector wavelength range selected as 210 nm. The presence and content of various organic acids were confirmed and determined by comparing the retention time and peak area of ​​each organic acid standard. Organic acid content is expressed in mg / g dry matter.

[0084] 3. Amino acid determination method: First, mix 1.0000g of ham sample (chopped) with 25mL of 5% trichloroacetic acid. If the volume exceeds the mark, bring the volume to 50mL and record the volume. After mixing, sonicate at room temperature for 30 minutes. After standing for 2 hours, filter the solution using double-layer filter paper, and centrifuge 1mL of the clear filtrate in a 1.5mL centrifuge tube at 15,000rpm for 30min. Take 400µL of the supernatant into a liquid chromatography bottle; filter again through a 0.22μm water film. Gas chromatography analysis conditions: CP WAX column (30m×0.32mm×0.25μm); injection port 250℃, detector 250℃, programmed temperature rise to 120℃ and hold for 3 min, rise to 190℃ at 10℃ / min, then rise to 220℃ at 2℃ / min and hold for 15 min, carrier gas N2 flow rate 3 mL / min, fuel gas H2 flow rate 47 mL / min, combustion gas (air) flow rate 400 mL / min, split ratio 10:1.

[0085] 4. Determination of Nucleotides: Accurately weigh 4g of chopped ham sample, add 20mL of 5% (v / v) pre-cooled perchloric acid, homogenize the mixture at 10000r / min for 30s (10s / time, 3 times) under ice bath conditions, centrifuge at 8000r / min for 10min at 4℃, and collect the supernatant. Filter the supernatant through double-layer filter paper. Add 10mL of pre-cooled 5% perchloric acid to the precipitate and mix well. Centrifuge again under the same conditions. Combine the supernatants collected from the two centrifugations, and adjust the pH of the solution to 6.5 with 1mol / L potassium hydroxide. Then, bring the volume to 50mL with ultrapure water and filter through a 0.22μm aqueous filter membrane before determination. The determination was performed using a high-performance liquid chromatograph equipped with a 2487 ultraviolet (UV) detector (220nm / 280nm). The chromatographic column was a Diamonsil C18 column (4.6mm×250mm, 5μm). The mobile phases A and B were acetonitrile and water, respectively. The detection wavelength was 250nm.

[0086] Analysis of test results

[0087] Analysis of organic acids in different grades of Xuanwei ham

[0088] Organic acids are important non-volatile flavor compounds that significantly influence the flavor properties of ham. The results, shown in Table 1, revealed six organic acids, including tartaric acid, malic acid, lactic acid, glacial acetic acid, citric acid, and succinic acid. In both biceps femoris (BF) and semimembranosus (SM) muscles, as the ham quality declined from superior (A) to spoiled (D), the content of various organic acids, including tartaric acid, malic acid, lactic acid, glacial acetic acid, citric acid, and succinic acid, as well as their total content, decreased significantly. Significant differences in organic acid content were observed between different grades within the same muscle type (P<0.05), indicating that organic acid content is a key factor affecting quality. For different muscle parts within the same grade, the content of most organic acids was higher in BF than in SM, and significant differences in organic acid content were observed between different muscle types (P<0.05), suggesting that muscle type also significantly affects organic acid content. Among the various organic acids, tartaric acid and malic acid show significant variations and relatively stable content differences among different qualities and muscle types; glacial acetic acid has a high content and shows a clear decreasing trend; citric acid has a low content and fluctuates greatly; succinic acid has a high content, and within the same grade, the content of BF and SM differs relatively greatly.

[0089] Table 1 Organic acid content of different muscle parts of Xuanwei ham of different grades

[0090]

[0091] Note: Different uppercase letters (A-D) indicate significant differences (P<0.05) between different grades of the same muscle group, and different lowercase letters (a-b) indicate significant differences (P<0.05) between different muscle groups of the same group.

[0092] Analysis of amino acids in different grades of Xuanwei ham

[0093] As shown in Table 2, a total of 17 amino acids were detected. Based on their flavor characteristics, these amino acids can be divided into bitter, umami, sweet, and tasteless amino acids. These include 8 bitter amino acids (histidine, arginine, tyrosine, valine, methionine, phenylalanine, isoleucine, and leucine); 2 umami amino acids (aspartic acid and glutamic acid); 6 sweet amino acids (serine, glycine, threonine, alanine, proline, and lysine); and 1 tasteless amino acid (cysteine). Regarding bitter amino acids, leucine was the most abundant. Its content decreased significantly with decreasing grade (A, B, C, D) (P<0.05). Grades A, B, and C all had leucine contents exceeding 300 mg / 100g. There was a significant difference between grade D ham and grades A, B, and C, with grade D ham having a significantly lower leucine content than the other three grades. Histidine was the amino acid with the lowest content (P<0.05), and there was no significant difference between different grades of ham (P>0.05). For other bitter amino acids, the content of bitter amino acids generally decreased with decreasing quality (P<0.05), and higher quality hams had relatively higher levels of bitter amino acids, indicating that free amino acids are unlikely to be the key factor causing unpleasant tastes (bitterness, sourness, astringency) in ham. Regarding umami amino acids, two umami amino acids were detected: glutamic acid and aspartic acid. Glutamic acid was more abundant than aspartic acid, accounting for nearly 1 / 8 of the total amino acids, making it the most abundant umami amino acid in Xuanwei ham. With decreasing ham grade, the content of glutamic acid decreased for both BF and SM grades (P<0.05). Hams of grades A, B, and C all had glutamic acid levels above 450 mg / 100g, while grade D ham had significantly lower levels than the other three grades, indicating that umami is an important flavor indicator for evaluating ham quality. Regarding aspartic acid, its content decreases significantly with decreasing ham quality. Numerically, levels A and B exceed 200 mg / 100g, while C and D are closer, ranging from 100-130 mg / 100g. For the same grade but different muscle cuts, BF (bread, glutamic acid) has a significantly higher content than SM (sweet ham). Glutamic acid and aspartic acid account for approximately 1 / 6 of the total amino acids, exhibiting relatively high content. Glutamic acid, as a umami amino acid, directly affects the umami flavor of the ham. Changes in glutamic acid content during curing and fermentation can significantly influence the ham's taste. As for sweet amino acids, the total sweet amino acid content is close to 2 / 5 of the total amino acid content. With decreasing ham quality, the sweet amino acid content shows a gradual decreasing trend, with A quality having the highest content and D quality having the lowest.The two most abundant sweet amino acids are alanine and lysine, with their content reaching over 500mg / 100g in Grade A ham. Alanine, in particular, reaches over 700mg / 100g, making it the amino acid with the highest content in Xuanwei ham.

[0094] For the same grade of muscle from different parts, there were no significant differences in the levels of sweet amino acids (except for alanine, proline, and lysine) between BF and SM. For the tasteless cysteine, there was no significant trend among the four grades (A, B, C, and D). Furthermore, the cysteine ​​content was relatively low (below 4 mg / 100g) across all four grades (A, B, C, and D), and there was no significant difference between BF and SM. This suggests that cysteine ​​may not be a major amino acid in Xuanwei ham and has a relatively small impact on its flavor.

[0095] Regarding total free amino acids, the total amino acid content of Grade A Xuanwei ham was significantly higher than that of other hams (P<0.05). The average total amino acid content of BF and SM was 4874.49 mg / 100g. The total amino acid content of BF was higher than that of SM, which may be related to the moisture and salt content. The activity of aminopeptidase is considered to be the main factor in the release of free amino acids in meat.

[0096] The taste threshold ratio (TAV) of amino acids measures the ratio between the concentration of a specific amino acid in a sample and its corresponding taste threshold. Generally, if the TAV is greater than 1, it means that this component has a significant impact on the taste of food; conversely, if the TAV is less than 1, it indicates that it does not significantly enhance the taste. In quality grades A, B, and C, only serine, proline, and threonine have a TAV less than 1. In quality grade D ham, the TAVs of serine, glycine, threonine, and proline are less than 1, indicating that spoiled ham has suffered a significant loss of sweet amino acids.

[0097] Table 2. Amino Acids in Different Muscle Parts of Xuanwei Ham of Different Grades

[0098]

[0099]

[0100]

[0101] Note: Different uppercase letters (A-D) indicate significant differences (P<0.05) between different grades of the same muscle group, and different lowercase letters (a-b) indicate significant differences (P<0.05) between different muscle groups of the same group.

[0102] Table 2 also verifies that the results of grading using amino acid testing are consistent with existing ham grading methods, confirming that the method of the present invention is reliable and accurate.

[0103] Nucleotide analysis of different grades of Xuanwei ham

[0104] Three flavor nucleotides, AMP, GMP, and IMP, were detected in the ham muscle of different grades and parts, as shown in Table 3. The AMP content gradually decreased with decreasing ham grade. For BF and SM, the AMP content decreased from 9.65 mg / 100g and 8.71 mg / 100g in superior grade to 5.84 mg / 100g and 5.24 mg / 100g in D grade, respectively (P<0.05). Within the same grade, the AMP content in BF was significantly higher than that in SM among different parts (P<0.05). The GMP content in BF and SM gradually decreased from 10.83 and 9.73 mg / 100g in A grade to 5.21 mg / 100g and 4.89 mg / 100g in D grade, respectively. Within the same grade, the GMP content in BF was significantly higher than that in SM among different parts. The IMP content in BF and SM gradually decreased from 5.42 mg / 100g and 4.71 mg / 100g in A to 1.95 mg / 100g and 1.57 mg / 100g in D, respectively (P<0.05). For the same grade, there were significant differences between different parts, with BF having a significantly higher IMP content than SM. The AMP, GMP, and IMP nucleotide contents decreased with the decline in Xuanwei ham quality. This may be because as ham quality decreases, microorganisms during fermentation consume or decompose nucleotides in the ham, endogenous enzymes accelerate nucleotide degradation, and oxidation reactions may damage the structure of nucleotides, reducing their content.

[0105] Table 3. Nucleotide content of different muscle parts in different grades of Xuanwei ham.

[0106]

[0107]

[0108] Note: Different uppercase letters (A-D) indicate significant differences (P<0.05) between different grades of the same muscle group, and different lowercase letters (a-b) indicate significant differences (P<0.05) between different muscle groups of the same group.

[0109] Analysis of electronic tongues for different grades of Xuanwei ham

[0110] As attached Figure 1As shown in the figure, for the same part of the ham, the umami response value decreases as the quality of the ham decreases, and the umami response value of grade D ham is much lower than that of grade A ham, indicating that ham spoilage has a significant impact on the umami of Xuanwei ham and seriously affects its quality. For different muscle parts of the same quality, there is no significant difference in umami between BF and SM grades. Regarding sourness, for the same part of the ham, for different quality grades A, B, C, and D, sourness increases as the quality decreases. For different muscle parts of the same quality, there is no significant difference in sourness between BF and SM grades. Regarding astringency, for different quality grades A, B, C, and D hams of the same part of the ham, astringency increases as the quality decreases, indicating that astringency increases with decreasing quality and has a significant impact on the overall flavor of the ham. For different muscle parts of the same quality, there is no significant difference in astringency between BF and SM grades. Regarding bitterness, for the same part of the ham and different qualities, the response value of bitterness increased as the quality of Xuanwei ham decreased, indicating that bitterness is also an important flavor affecting the quality of Xuanwei ham. There was no significant difference in bitterness between BF and SM muscle parts of the same quality. Regarding saltiness, for the same part of the ham and different qualities, the response value of saltiness decreased as the quality of Xuanwei ham decreased, indicating that our salt content decreased, a result consistent with our salt content determination. There was no significant difference between BF and SM muscle parts of the same quality, inconsistent with the salt content determination; this may be due to a synergistic salt-enhancing effect of high umami compounds and salt. It is noteworthy that the response values ​​of umami and saltiness were significantly higher than those of sourness, bitterness, and astringency, indicating that umami and saltiness are the most important flavor attributes in ham, consistent with previous reports. Richness, or the aftertaste value of umami, reflects the residual umami flavor. In this study, for the same part of the ham and different qualities, the richness decreased as the ham grade decreased, indicating that higher quality ham has a richer umami flavor and a more pronounced aftertaste. There was no significant difference in richness between BF and SM muscle parts of the same quality. The higher richness of premium ham may be due to the accumulation of flavor components such as amino acids, organic acids, and nucleotides, which increases the richness intensity of premium ham.

[0111] As attached Figure 2As shown, PCA analysis was used to further illustrate the differences between the taste values ​​of each group. PC1 contributed 83.2%, PC2 contributed 14.5%, and the cumulative contribution was 97.7%, representing the overall taste characteristics of the samples. Sample A was mainly concentrated in the second quadrant, samples B and C were mainly in the third quadrant, and sample D was in the first quadrant and far from the other three quality hams. This indicates that quality A ham differs significantly from B, C, and D; D differs significantly and considerably from A, B, and C; while the difference between B and C is not significant. This suggests that the electronic tongue can effectively distinguish between different grades of Xuanwei ham. PC1 was positively correlated with bitterness, sourness, and astringency, and negatively correlated with saltiness and umami. PC2 was positively correlated with sourness, bitterness, astringency, umami, and richness, and negatively correlated with saltiness. Bitterness, sourness, and astringency were similar to those of D, indicating that bitterness, sourness, and astringency are important taste characteristics of spoiled ham. The main characteristics of Grade A ham are its umami and richness, both of which fall in the second quadrant, indicating that umami is an important flavor factor affecting the quality grade of Xuanwei ham.

[0112] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

[0113] Correlation analysis

[0114] To further understand the impact of non-volatile compounds on the quality variations of different grades of Xuanwei ham, all the above indicators were synthesized and analyzed using principal component analysis (PCA). (See attached...) Figure 3As shown, principal component analysis (PC1) effectively distinguishes samples A, B, C, and D, indicating good differences among them. PC1 explains 84.2% of the variance, and PC2 explains 7.3%. From PC1, the BF and SM of grades A and B hams are mainly concentrated on the right side of PC1, while the BF and SM of grades C and D are mainly concentrated on the left side, with grade D being far from the other three grades. This indicates that Xuanwei ham grades A, B, and C are well distinguishable from rotten ham. Furthermore, free amino acids, organic acids, and nucleotides are also mainly concentrated on the right side of PC1, indicating that the content of flavor compounds has a significant impact on the quality of Xuanwei ham. From PC2, different muscle parts of the same grade of ham can be well distinguished, with a certain distance between BF and SM, indicating some differences between them. Grade D rotten ham is far from non-volatile flavor compounds, indicating that rotten ham contains fewer non-volatile flavor compounds.

[0115] In summary, this patent provides a method for ham quality grading based on the analysis of non-volatile flavor compounds. This method assesses ham quality by measuring the content of non-volatile compounds (such as amino acids), enabling accurate grading and early warning of spoilage risks. It has potential for industrial application, can promote industry standardization, and clarifies the correlation between various indicators and ham quality. The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the invention. Various modifications and improvements made to the technical solutions of the present invention by those skilled in the art without departing from the spirit of the invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for grading the quality of ham based on the analysis of non-volatile flavor compounds, characterized in that... This method is specifically carried out in the following steps:

1. Take naturally fermented and matured Xuanwei ham, cut off the oxidized layer, and quickly separate the biceps femoris muscle and semimembranosus muscle; 2. The biceps femoris and semimembranosus muscles separated in step 1 were subjected to amino acid analysis. The biceps femoris muscle was denoted by BF and the semimembranosus muscle by SM. The quality of the ham was graded according to the total amino acid content or the umami amino acid content, and divided into grade A, grade B, grade C and grade D from high to low. The Grade A quality described in Step 2 is as follows: total amino acid content of BF fraction ≥ 4650 mg / 100g, and total amino acid content of SM fraction ≥ 4437 mg / 100g; Grade B quality: The total amino acid content of BF part is ≥3997mg / 100g and <4650 mg / 100g, and the total amino acid content of SM part is ≥3856 mg / 100g and <4437 mg / 100g. Grade C quality: The total amino acid content of the BF part is ≥3023mg / 100g and <3997 mg / 100g, and the total amino acid content of the SM part is ≥2726mg / 100g and <3856mg / 100g. Grade D quality: Total amino acid content in BF portion <3023mg / 100g, total amino acid content in SM portion <2726 mg / 100g; Or, as described in step two, Grade A quality: umami amino acid content in BF portion ≥ 798 mg / 100g, umami amino acid content in SM portion ≥ 749 mg / 100g; Grade B quality: The umami amino acid content of BF part is ≥677mg / 100g and <798mg / 100g, and the umami amino acid content of SM part is ≥625 mg / 100g and <749 mg / 100g. Grade C quality: The umami amino acid content of BF part is ≥480mg / 100g and <677mg / 100g, and the umami amino acid content of SM part is ≥438mg / 100g and <625mg / 100g. Grade D quality: BF portion contains <480mg / 100g of umami amino acids, SM portion contains <438mg / 100g of umami amino acids; If the test values ​​for the BF and SM areas fall into different levels, the lower level shall prevail.

2. The method for grading ham quality based on the analysis of non-volatile flavor compounds according to claim 1, characterized in that... Total amino acids include bitter amino acids, umami amino acids, sweet amino acids, and tasteless amino acids.

3. The method for grading ham quality based on the analysis of non-volatile flavor compounds according to claim 1, characterized in that... Umami amino acids include aspartic acid and glutamic acid.

4. The method for grading ham quality based on the analysis of non-volatile flavor compounds according to claim 2, characterized in that... Bitter amino acids include histidine, arginine, tyrosine, valine, methionine, phenylalanine, isoleucine, and leucine.

5. The method for grading ham quality based on the analysis of non-volatile flavor compounds according to claim 2, characterized in that... Sweet-tasting amino acids include serine, glycine, threonine, alanine, proline, and lysine; tasteless amino acids include cysteine.

6. The method for grading ham quality based on the analysis of non-volatile flavor compounds according to claim 1, characterized in that... The Xuanwei ham is produced according to the following steps: S1. Remove blood stains and dirt from fresh pork leg meat, then cut and shape it to obtain leg embryos; S2. The leg embryos treated in S1 are salted four times. After each salting, the salted leg embryos are stacked and turned over. The total amount of salt is controlled to be 9-14% of the weight of the leg embryos. The total salting time is two months. S3. Rinse the ham after S2 to remove the surface salt, then air dry until there is no moisture on the surface, and then hang it in the fermentation room for natural fermentation to obtain naturally fermented and matured Xuanwei ham.

7. The method for grading ham quality based on the analysis of non-volatile flavor compounds according to claim 6, characterized in that... The natural fermentation process described in S3 takes 360-380 days.

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