A compound microbial fermentation agent for enhancing the aroma of dry-cured ham and its application

Abstract

This invention discloses a compound microbial fermentation agent for enhancing the aroma of dry-cured ham and its application. The agent is characterized by being a mixture of Penicillium and Rhodotorula glutinis in a cell ratio of 1-4:1-3, with an inoculation density of 10-1. 5 ~10 8 The application of CFU per gram of cured ham includes the following steps: Inoculate the ham sample surface with the compound microbial fermentation agent at the above-mentioned inoculation density, and ferment for 120–150 days under the following temperature and humidity conditions: 50–60 days at 15–25℃ and 65–75% humidity; 50–60 days at 25–30℃ and 70–80% humidity; and 20–30 days at 30–35℃ and 70–85% humidity. This yields a dry-cured ham with enhanced cured flavor. The advantage is that Penicillium and Rhodotorula glutinis, at a specific ratio, mutually promote each other, significantly improving the cured flavor of the dry-cured ham.

Description

Technical Field

[0001] This invention relates to the field of microorganisms and ham fermentation, and in particular to a compound microbial fermentation agent for improving the cured flavor of dry-cured ham and its application. Background Technology

[0002] Jinhua ham and Rugao ham, as typical representatives of dried and cured hams in my country, are deeply loved by consumers for their high nutritional value and unique flavor. The cured aroma is not only a key attribute of dried and cured ham's fragrance but also an important indicator for distinguishing different quality grades. Volatile flavor compounds produced by amino acid degradation play a crucial role in the aroma formation of dried and cured ham. A large number of volatile flavor compounds, such as branched aldehydes and pyrazines, accumulate to constitute the cured aroma of dried and cured ham. Among them, benzaldehyde, phenylacetaldehyde, and 3-methylbutyraldehyde impart a cured aroma to dried and cured ham; 2,5-dimethylpyrazine is the main contributor to nutty and cured aromas, giving dried and cured ham a meaty aroma; and 3-ethyl-2,5-dimethylpyrazine mainly imparts a rich cured aroma to dried and cured ham. These products are the main components promoting the formation of the cured aroma in dried and cured ham. The formation of these products mainly depends on the catalytic conversion of aromatic amino acids (primarily phenylalanine) into phenylpyruvic acid and phenylethylamine by microorganisms, followed by decarboxylation by aromatic amino acid transaminases and amino acid decarboxylases to form benzaldehyde and phenylacetaldehyde. Meanwhile, branched-chain amino acids (leucine) are converted to 3-methylbutyraldehyde by branched-chain amino acid transaminases and amino acid decarboxylases. Furthermore, α-dicarbonyl compounds react with lysine to form α-aminoketones, which condense to form dihydropyrazines. Dihydropyrazines then form corresponding alkylpyrazines under the action of branched-chain amino acid dehydrogenases, resulting in 2,5-dimethylpyrazines and 2,6-dimethylpyrazines. In summary, the accumulation of branched-chain and aromatic amino acids is a prerequisite for the formation of the waxy aroma, and amino acid transaminases and amino acid dehydrogenases are the rate-limiting enzymes for the formation of branched-chain aldehydes and pyrazines. However, the expression levels of endogenous amino acid transaminases, amino acid decarboxylases, and amino acid dehydrogenases in dry-cured ham are low, and their enzyme activities are insufficient, limiting their ability to catalyze the production of branched-chain aldehydes and pyrazines. Therefore, enhancing the activity of amino acid transaminases and amino acid dehydrogenases during the processing of dry-cured ham and promoting the conversion of branched-chain amino acids and aromatic amino acids into their corresponding branched-chain aldehydes and pyrazines is of great significance for the formation of the cured flavor in dry-cured ham.

[0003] The maturation process of dry-cured ham mostly employs natural fermentation. During natural fermentation, microorganisms primarily originate from the raw meat, fermentation environment, and processing equipment. This wide range of sources results in a diverse and complex microbial community, making it difficult to guarantee product quality and leading to bitterness, stickiness, or off-putting odors. In recent years, the development of humidity and temperature control equipment has enabled artificial intelligence control over the processing of dry-cured ham. This provides the necessary conditions for inoculating microbial fermentation agents and achieving complete control over the fermentation and maturation process, while inhibiting contamination by other microorganisms. Research has found that inoculating microbial fermentation can shorten the maturation time of dry-cured ham and promote the accumulation of volatile flavor compounds, ensuring the formation of a unique flavor while improving product quality and safety. Molds and yeasts are widely distributed microorganisms during the fermentation and maturation process of dry-cured ham and are closely related to the formation of its flavor and quality. The proteolytic enzymes of molds and yeasts can significantly degrade myosin, actin, and other myofibril proteins, converting them into free amino acids, providing precursors for the cured aroma of dry-cured ham. However, to date, no research has reported on the use of Penicillium and Rhodotorula glutinis in co-inoculation to enhance the flavor of dry-cured ham. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a compound microbial fermentation agent for improving the curing aroma of dry-cured ham and its application. The dry-cured ham fermented by the fermentation agent can significantly improve the curing aroma.

[0005] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows: a compound microbial fermentation agent for improving the aroma of dry-cured ham, which is composed of Penicillium chrysogenum and Rhodotorula mucilaginosa in a ratio of (1-4):(1-3) cell count.

[0006] Preferably, the Penicillium chrysogenum and Rhodotorula mucilaginosa are mixed in a 2:3 ratio of cell volume.

[0007] Preferably, the inoculum density of the compound microbial fermentation agent is 10. 5 ~10 8 CFU per kilogram of cured ham.

[0008] This invention also provides a method for enhancing the cured flavor of dry-cured ham using a compound microbial fermentation agent, comprising the following steps: mixing the compound microbial fermentation agent at a bacterial density of 10... 5 ~10 8The ham samples were inoculated with a concentration of CFU / kg after curing and fermented for 120–150 days under the following temperature and humidity conditions: 50–60 days at 15–25℃ and 65–75% humidity; 50–60 days at 25–30℃ and 70–80% humidity; and 20–30 days at 30–35℃ and 70–85% humidity, to obtain dry-cured ham with enhanced cured flavor.

[0009] Preferably, the compound microbial fermentation agent is composed of Penicillium chrysogenum and Rhodotorula mucilaginosa in a 2:3 ratio of bacterial cells.

[0010] Preferably, the inoculum density of the compound microbial fermentation agent is 10. 7 CFU / kg dry-cured ham.

[0011] Compared with existing technologies, the advantages of this invention are as follows: This invention provides a compound microbial fermentation agent and its application for enhancing the cured flavor of dry-cured ham. By utilizing compound inoculation, branched-chain amino acids and aromatic amino acids in dry-cured ham are converted into aromatic aldehydes, branched-chain aldehydes, and pyrazines under the catalysis of amino acid transaminase, amino acid dehydrogenase, and amino acid decarboxylase, thus increasing the cured flavor of the dry-cured ham. Through inoculation with *Penicillium*, *Rhodotorula glutinis*, and a mixture of *Penicillium* and *Rhodotorula glutinis*, it was found that the total content of volatile flavor compounds in Jinhua ham and Rugao ham fermented with the compound inoculation of *Penicillium* and *Rhodotorula glutinis* increased by 2.46 and 2.43 times, respectively, compared with the control group. The cured flavor and overall acceptability of each product increased by more than 1.40 times, significantly higher than products fermented by *Penicillium* and *Rhodotorula glutinis* alone. The synergistic effect of the two strains is more significant. Therefore, Penicillium chrysogenum and Rhodotorula mucilaginosa, when used in a specific ratio, have a mutually reinforcing effect, resulting in dried-cured ham with an effectively enhanced cured flavor, and thus have broad application prospects and market value. Attached Figure Description

[0012] Figure 1 This refers to the change in the total number of fungal communities in the ham product of this invention;

[0013] Figure 2 The changes in sensory scores of the ham product group according to the present invention;

[0014] Figure 3 This invention relates to the changes in the free amino acid content of the ham product group.

[0015] Figure 4 This invention relates to changes in enzyme activity in the ham product group.

[0016] Figure 5 This refers to the changes in the content of volatile flavor compounds in the ham product of the present invention. Detailed Implementation

[0017] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0018] I. Experimental Materials and Measurement Methods

[0019] 1. Collection of Jinhua Ham

[0020] Fresh hind legs of crossbred pigs, weighing 12-15 kg, were trimmed and then left to stand for 48 hours in a cold storage room at 0-4℃ and 85-90% humidity. The pre-cooled hind legs were then cured with a mixture of 5.5% NaCl, 0.015% NaNO2, and 0.015% KNO3 (by weight per kilogram of fresh pig leg), applied in five stages. The hams were then cured at 4℃ and 85% humidity for 40-45 days to allow for salt equilibration. After salt equilibration, the ham surfaces were washed and dried, and a sample was collected, designated as Ham Sample I.

[0021] 2. Collection of Rugao ham

[0022] Freshly trimmed hind legs of crossbred pigs, weighing 12-16 kg, were placed in a cold storage room at 0-4℃ and 85-90% humidity for 48 hours. The pre-cooled hind legs were then cured with a mixture of 6.5% NaCl, 0.015% NaNO2, and 0.015% KNO3 (by weight per kg of fresh pig leg), applied in six stages. The hams were then cured at 4℃ and 85% humidity for 40-45 days to allow for salt equilibration. After salt equilibration, the ham surfaces were washed and dried, and a sample was collected, designated as Ham Sample II.

[0023] 3. Preparation of Penicillium chrysogenum starter

[0024] Penicillium chrysogenum was activated by inoculation onto potato dextrose (PDA) agar. Single colonies were then picked and inoculated into PDA liquid medium and cultured at 25°C for 5 days. After culture, the bacterial suspension was filtered through sterile gauze to remove mold hyphae. After centrifugation at 12,000 rpm for 10 min at 4°C, the Penicillium chrysogenum cells were resuspended in physiological saline, and the suspension concentration was adjusted to the required concentration for use as inoculum.

[0025] 4. Preparation of Rhodotorula mucilaginosa starter culture: Rhodotorula mucilaginosa was inoculated onto yeast peptone glucose (YPD) agar medium for activation. Single colonies were picked and inoculated into yeast peptone glucose liquid medium and cultured at 28℃ for 2 days. After culture, the cells were centrifuged at 12000 rpm for 10 min at 4℃. The Rhodotorula mucilaginosa cells were then suspended in physiological saline, and the suspension concentration was adjusted to the required concentration for use as the inoculum.

[0026] 5. The total colony count was determined according to the method in GB 4789.2-2022, "Determination of Total Colony Count". In a sterile laminar flow hood, 10g of fermented ham sample was taken, chopped, and placed in a sterile homogenizing bag containing 90mL of sterile physiological saline. The sample was then agitated for 1-2 minutes using a sterile beater. 1mL of the sample solution was taken and appropriately diluted with sterile physiological saline to prepare a 1:10 sample solution. Then, 100μL of the appropriate dilution was accurately pipetted onto PCA agar plates for counting. The plates were incubated upside down at 28℃ for 4 days, and colony counts were performed using a colony counter. Six samples were measured in each group. The results are expressed as the average of all replicates, with colony forming units expressed as CFU / g.

[0027] 6. Sensory evaluation

[0028] Sensory evaluation of ham samples was conducted by 10 sensory evaluators (5 men and 5 women, aged 25-35 years) with more than 5 years of experience, in accordance with EN ISO 8586-2014 standard. The evaluators attended training courses on cured aroma and overall acceptability, and conducted descriptive analyses of each sample in a well-ventilated room. Ham samples were cut into 1×1×0.5cm slices and presented to the evaluators for no more than 15 minutes. Evaluators rated cured aroma and overall acceptability on a scale of 0 to 10 (0: none, 10: high intensity). The difference between the individual score for each indicator and the mean was no more than ±1. Results are expressed as the average of ten scores.

[0029] 7. Determination of free amino acids

[0030] Mix 5g of ham sample with 25mL of 0.01M hydrochloric acid solution and let stand at 4℃ for 10h before homogenization. Filter through double-layer filter paper, collect the supernatant, and transfer 1mL of the clear filtrate to a 1.5mL centrifuge tube. Centrifuge at 12000rpm for 30min. Filter the supernatant again through a 0.22μm aqueous filter membrane, and transfer 400μL to a liquid chromatography sample vial for loading. Analyze the free amino acid content using an L-8900 automated amino acid analyzer. The free amino acid content is expressed as mg / 100g ham sample.

[0031] 8. Enzyme activity assay

[0032] Take 5g of chopped ham sample and add 35mL of 50mM sodium phosphate buffer (containing 5mM EGTA, pH 7.5). Homogenize at 12000rpm for 30s under ice bath conditions. Centrifuge at 10000rpm for 20min at 4℃. Collect the supernatant for enzyme activity assay. The activities of aromatic amino acid transaminase (Arat), branched-chain amino acid dehydrogenase (BCAT), branched-chain amino acid dehydrogenase (BCAAD), and keto acid decarboxylase (KDC) were measured using enzyme-linked immunosorbent assay kits. Enzyme activity is expressed as U / g, and each enzyme activity assay was performed in 5 replicates.

[0033] 9. Determination of volatile flavor compounds

[0034] Volatile compounds in ham samples were extracted using headspace solid-phase microextraction (HS-SPME) and analyzed by GC-MS. 4 g of ham sample was placed in a 20 mL headspace vial, and the extraction head (50 / 30 μm DVB / CAR / PDMS) was inserted. Extraction was performed at 45 °C for 40 min, followed by resolution at 250 °C for 5 min at the injection port. The GC-MS temperature program was as follows: hold at 40 °C for 5 min, then increase to 200 °C at a rate of 5 °C / min, and then increase to 250 °C at a rate of 15 °C / min and hold for 8 min. The mass spectrometer was run at 70 eV (EI mode) with a scan range of 35–450 m / z. The NIST 17 database was used for the identification of volatile compounds. Compounds with retention fractions >80 were quantitatively analyzed using 2-methyl-3-heptanone as an internal standard (10 μL, 10 ppm). Quantitative results are expressed as μg / kg ham sample. II. Specific Implementation Methods

[0036] Example 1

[0037] Compound inoculation fermentation of Jinhua ham

[0038] Penicillium chrysogenum and Rhodotorula mucilaginosa were mixed at a cell ratio of 2:3. The mixture was then resuspended in physiological saline, and the suspension concentration was adjusted to 10. 7 CFU / kg was inoculated onto the surface of ham sample I and fermented for 120 days under the following temperature and humidity conditions: 50 days at 20-25℃ and 65-75% humidity; 50 days at 25-30℃ and 70-80% humidity; and 20 days at 30-35℃ and 70-85% humidity to obtain ham sample 1.

[0039] Example 2

[0040] Compound inoculation fermentation of Rugao ham

[0041] Penicillium chrysogenum and Rhodotorula mucilaginosa were mixed at a cell ratio of 2:3. The mixture was then resuspended in physiological saline, and the suspension concentration was adjusted to 10. 7 CFU / kg was inoculated onto the surface of ham sample II and fermented for 150 days under the following temperature and humidity conditions: 60 days at 15–25℃ and 65–75% humidity; 60 days at 25–30℃ and 70–80% humidity; and 30 days at 30–35℃ and 70–85% humidity, resulting in ham sample II. After the above maturation process, the ham's weight loss rate was 40–42%.

[0042] Comparative Example 1

[0043] Jinhua ham naturally fermented

[0044] Sample I of Jinhua ham, after curing, was placed in a fermentation room and fermented naturally for 120 days. During this period, the fermentation room was regularly ventilated (windows opened during the day and closed in the evening, and closed on rainy days) to maintain dryness. The air temperature fluctuated between 15 and 35°C, and the relative humidity varied between 65 and 85%. After the above maturation process, the weight loss rate of the ham was 40%–42%.

[0045] Comparative Example 2

[0046] Rugao ham is naturally fermented.

[0047] After curing, sample II of Rugao ham was placed in a fermentation room and fermented under natural conditions for 150 days. During this period, the fermentation room was regularly ventilated (windows were opened during the day and closed in the evening, and closed on rainy days) to maintain dryness. The air temperature fluctuated between 15 and 35°C, and the relative humidity varied between 65% and 85%. After the above maturation process, the weight loss rate of the ham was 40%–42%.

[0048] Comparative Example 3

[0049] Penicillium inoculation and fermentation of Jinhua ham

[0050] The cells of Penicillium chrysogenum were suspended in physiological saline and the suspension concentration was adjusted to 10. 7 CFU / kg was inoculated onto the surface of ham sample I and fermented under the following temperature and humidity conditions: 50 days at 20–25℃ and 65–75% humidity; 50 days at 25–30℃ and 70–80% humidity; and 20 days at 30–35℃ and 70–85% humidity. After the above maturation process, the ham's weight loss rate was 40–42%.

[0051] Comparative Example 4

[0052] Jinhua ham fermented with Rhodotorula glutinis

[0053] Rhodotorula mucilaginosa cells were suspended in physiological saline and the suspension concentration was adjusted to 10. 7 CFU / kg was inoculated onto the surface of ham sample I, and fermentation and maturation were carried out under the following temperature and humidity conditions: 50 days at 20–25℃ and 65–75% humidity; 50 days at 25–30℃ and 70–80% humidity; and 20 days at 30–35℃ and 70–85% humidity. After the above maturation process, the ham's weight loss rate was 40–42%.

[0054] II. Analysis of Experimental Results

[0055] 1. Optimal ratio of bacterial strains

[0056] Ham samples were prepared by setting the cell ratios of Penicillium chrysogenum and Rhodotorula mucilaginosa to 1:1, 1:2, 1:3, 2:1, 2:3, and 4:3, respectively, using the same preparation method as in Example 1 above.

[0057] According to Example 1 of the present invention, the Penicillium chrysogenum and Rhodotorula mucilaginosa combined fermentation agent exhibits the best growth status of both strains at a ratio of 2:3, and the viable cell counts of the two strains are on the same order of magnitude, which helps to promote the co-growth and fermentation of the two microorganisms. Based on these results, the optimal cell ratio of Penicillium chrysogenum and Rhodotorula mucilaginosa combined fermentation agent is 2:3.

[0058] 2. Determining the optimal inoculation dose

[0059] The cell ratio of Penicillium chrysogenum and Rhodotorula mucilaginosa was set at 2:3, and the inoculum size was set at 10 μg / mL. 5 CFU / kg, 10 6 CFU / kg, 10 7 CFU / kg, 10 8 CFU / kg, the specific preparation method is the same as that in Example 1 above.

[0060] Visual observation revealed that, within the same fermentation time, the inoculum size of the combined Penicillium chrysogenum and Rhodotorula mucilaginosa starter culture was 10. 5 CFU / kg and 10 6 The bacterial strains in the CFU / kg treatment group grew relatively slowly, and their bacterial count was significantly lower than that in the group with an inoculum of 10. 7 CFU / kg treatment group; while the inoculation amount was 10 8 The number of strains in the CFU / kg treatment group was highest during the early fermentation stage and when the inoculum size was 10. 7 There was no significant difference in the number of bacterial strains among the CFU / kg treatment groups. These results combined indicate that the optimal inoculum size for the combined Penicillium chrysogenum and Rhodotorula mucilaginosa fermentation agent is 10... 7 CFU / kg.

[0061] 3. Changes in the total number of fungal communities in ham products

[0062] During ham fermentation, the total number of fungal communities differed significantly between the initial and final stages of fermentation. For example... Figure 1As shown, the total fungal counts of Jinhua ham and Rugao ham at the initial stage of fermentation were 3.04 log CFU / g and 3.08 log CFU / g, respectively; while the total fungal counts of Comparative Examples 1, 2, 3, 4, Example 1, and Example 2 at the end of fermentation were 4.74, 4.92, 6.05, 6.34, 7.58, and 7.79 log CFU / g, respectively. Compared to Comparative Examples 1, 3, and 4, the total fungal count in Example 1 was significantly increased, indicating that the mixed inoculation of *Penicillium chrysogenum* and *Rhodotorula mucilaginosa* further inhibited the growth of other microorganisms, making them the dominant fungi in the fermentation process. After fermentation, the total fungal count in Examples 1 and 2 increased to 7.58 log CFU / g and 7.79 log CFU / g, respectively (P<0.05). These results indicate that the mixed inoculation of Penicillium chrysogenum and Rhodotorula mucilaginosa showed good adaptability in Jinhua ham and Rugao ham.

[0063] 4. Changes in sensory scores of ham products

[0064] Sensory ratings for all ham products, such as Figure 2 As shown, compared with Comparative Example 1, the scores for cured flavor and overall acceptability of Comparative Examples 3, 4, and 1 were significantly increased. Specifically, compared with Comparative Example 1, the cured flavor intensity of the products from Comparative Examples 3, 4, and 1 increased by 1.27, 1.30, and 1.42 times, respectively, while the overall acceptability intensity increased by 1.24, 1.31, and 1.41 times, respectively. Compared with Comparative Example 2, the cured flavor and overall acceptability intensity of Example 2 were 1.42 times and 1.43 times that of Comparative Example 2, respectively. Among all examples and comparative examples, Example 1 and Example 2 showed the highest cured flavor and overall acceptability scores. These results indicate that inoculation with starter cultures, especially the mixture of Penicillium chrysogenum and Rhodotorula mucilaginosa, significantly improved the cured flavor intensity of Jinhua ham and Rugao ham, thereby improving the overall acceptability of the products.

[0065] 5. Changes in the free amino acid content of ham products

[0066] The changes in free amino acid content of hams in different embodiments and comparative examples are as follows: Figure 3As shown, compared with Comparative Example 1, the total free amino acid content of Comparative Examples 3, 4, 1, and 2 was significantly increased. Specifically, the total free amino acid content of Comparative Examples 3, 4, and 1 was 1.37, 1.57, and 1.73 times that of Comparative Example 1, respectively; the total free amino acid content of Example 2 was 1.63 times that of Comparative Example 2. These results indicate that the inoculation starter promoted the formation of free amino acids in ham. The branched-chain amino acid and aromatic amino acid contents of Comparative Examples 3, 4, and 1 were significantly higher than those of Comparative Example 1, while the branched-chain amino acid content of Example 2 was significantly higher than that of Comparative Example 2. Specifically, the aromatic amino acid contents of Comparative Examples 3, 4, and 1 were 1.30, 1.36, and 1.68 times that of Comparative Example 1, respectively; while the branched-chain amino acid contents were 1.38, 1.43, and 1.62 times that of Comparative Example 1, respectively. The aromatic amino acid and branched-chain amino acid contents of Example 2 were 1.72 and 1.68 times that of Comparative Example 2, respectively. Compared with Comparative Examples 1 and 2, Examples 1 and 2 showed higher contents of aromatic amino acids and branched-chain amino acids, respectively. This indicates that inoculation with a mixture of Penicillium chrysogenum and Rhodotorula mucilaginosa is more conducive to the accumulation of branched-chain amino acids and aromatic amino acids in Jinhua ham and Rugao ham. This may further affect the development of volatile flavor compounds and cured aroma in ham.

[0067] 6. Changes in enzyme activity in ham products

[0068] Changes in the activities of amino acid transaminase, amino acid decarboxylase, and amino acid dehydrogenase in ham are as follows: Figure 4 As shown, compared with Comparative Example 1, the activities of aromatic amino acid transaminase, branched-chain amino acid transaminase, branched-chain amino acid dehydrogenase, and ketoate decarboxylase in Comparative Examples 3, 4, and 1 were all significantly increased. Specifically, the activities of branched-chain amino acid transaminase in Comparative Examples 3, 4, and 1 were 2.20, 2.78, and 3.24 times that of Comparative Example 1, respectively, and the enzyme activity of Example 2 was 3.01 times that of Comparative Example 2; while the activities of branched-chain amino acid dehydrogenase in Comparative Examples 3, 4, and 1 were 2.11, 2.53, and 2.69 times that of Comparative Example 1, respectively, and the activity of branched-chain amino acid dehydrogenase in Example 2 was 2.41 times that of Comparative Example 2. Compared with Comparative Examples 1 and 2, Examples 1 and 2 exhibited higher activities of branched-chain amino acid transaminase. These results indicate that simultaneous inoculation with a mixture of Penicillium chrysogenum and Rhodotorula mucilaginosa is more conducive to the formation of branched-chain amino acids and aromatic amino acids into corresponding branched-chain aldehydes and pyrazines under the catalysis of amino acid transaminases, amino acid dehydrogenases, and amino acid decarboxylases.

[0069] 7. Changes in the content of volatile flavor compounds in ham products

[0070] like Figure 5 As shown, the total content of volatile flavor compounds producing a cured and preserved aroma in Comparative Examples 1, 2, 3, 4, Example 1, and 2 were 92.41, 103.27, 176.81, 190.03, 227.08, and 251.02 μg / kg, respectively. Specifically, the total content of flavor compounds in Comparative Examples 3, 4, and 1 was 1.91, 2.06, and 2.46 times that of Comparative Example 1, respectively, and the total content of flavor compounds in Example 2 was 2.43 times that of Comparative Example 2. Benzaldehyde, phenylacetaldehyde, 3-methylbutyraldehyde, 2,5-dimethylpyrazine, 2,6-dimethylpyrazine, and 3-ethyl-2,5-dimethylpyrazine were the main flavor compounds, with 3-ethyl-2,5-dimethylpyrazine having the highest content in each group. Compared to Comparative Examples 1 and 2, Examples 1 and 2 exhibited higher levels of benzaldehyde, phenylacetaldehyde, 3-methylbutyraldehyde, 2,5-dimethylpyrazine, 2,6-dimethylpyrazine, and 3-ethyl-2,5-dimethylpyrazine. This indicates that inoculation with a mixture of Penicillium chrysogenum and Rhodotorula mucilaginosa is beneficial for the accumulation of volatile flavor compounds that produce cured and preserved aromas, thereby enhancing the cured and preserved aromas of Jinhua ham and Rugao ham.

[0071] The foregoing description is not intended to limit the invention, nor is the invention limited to the examples given. Any changes, modifications, additions, or substitutions made by those skilled in the art within the scope of the invention should also be considered within the protection scope of the invention.

Claims

1. A composite microbial starter for enhancing the curing aroma of dry-cured ham, characterized by: The complex microbial fermenting agent is mixed by Penicillium chrysogenum Penicillium chrysogenum and Rhodotorula mucilaginosa Rhodotorula mucilaginosa in a ratio of 1-4:1-3.

2. The compound microbial starter culture for improving the curing aroma of dry-cured ham according to claim 1, characterized in that: The complex microbial fermenting agent is mixed by Penicillium chrysogenum Penicillium chrysogenum and Rhodotorula mucilaginosa Rhodotorula mucilaginosa in a ratio of 2:

3.

3. The compound microbial starter culture for improving the curing aroma of dry-cured ham according to claim 1, characterized in that: The inoculation density of the composite microbial starter is 10 5 ~ 10 8 CFU per kilogram of cured ham.

4. A method for improving the curing aroma of dry-cured ham using the complex microbial starter according to any one of claims 1 to 3, characterized in that comprising the steps of: The complex microbial starter was inoculated to the surface of the ham sample at the end of salting at a concentration of 10 5 ~10 8 CFU / kg, and fermented and matured for 120-150 d under the following temperature and humidity conditions: 15-25 ℃ and 65-75% humidity for 50-60 d; 25-30 ℃ and 70-80% humidity for 50-60 d; 30-35 ℃ and 70-85% humidity for 20-30 d, to obtain dry-cured ham with enhanced salting and bacon aroma.

5. The method for improving the curing aroma of dry-cured ham using a complex microbial starter according to claim 4, characterized in that: The inoculation density of the composite microbial starter is 10 7 CFU / kg dry cured ham.

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