Systematic monitoring and analysis method for physicochemical properties of pit mud of Luzhou-flavor liquor in different seasons and its application

Abstract

The application discloses a kind of strong-flavor liquor pit mud seasonal physicochemical property system monitoring analysis method and application thereof, belong to strong-flavor liquor brewing technical field.The method includes: in spring and autumn, upper layer, middle layer and lower layer of pit in pit are collected pit mud sample;Sample is characterized, wet sample bulk density test, with ethyl caproate and pure water as medium contact angle and immersion time test, fourier transform infrared spectrum analysis;Integrate above multidimensional data, based on the comprehensive evaluation of the structure characteristics, interface characteristics and fermentation function state of pit mud on the basis of multi-parameter collaborative change relationship, realize the system monitoring of pit mud seasonal change.The application is analyzed by multiple parameters, overcome the one-sidedness of single index evaluation, provide reliable basis for pit maintenance and process control.

Description

Technical Field

[0001] This invention belongs to the field of strong-aroma baijiu brewing technology, and relates to a method for systematically monitoring and analyzing the seasonal physicochemical properties of strong-aroma baijiu cellar mud and its application. Specifically, it relates to a method for systematically monitoring and analyzing the seasonal physicochemical properties of strong-aroma baijiu cellar mud based on the synergistic analysis of multiple physicochemical parameters. Background Technology

[0002] Strong-aroma baijiu is renowned for its rich aroma and harmonious flavor. The formation of its core flavor compounds, such as ethyl hexanoate, is closely related to the physicochemical properties of the fermentation pit mud and the metabolic state of microorganisms. As an important habitat for microorganisms, the water content, pore structure, surface wetting characteristics, and functional group composition of the fermentation pit mud fluctuate significantly with seasonal changes, thereby affecting the fermentation process and the formation of flavor compounds.

[0003] Currently, research on fermentation pit mud largely focuses on the detection and analysis of single indicators, such as the determination of physicochemical parameters or the analysis of microbial composition. However, evaluation methods based on single indicators are insufficient to comprehensively reflect the overall state of the pit mud under different seasons and its correlation with fermentation function. Existing technologies lack an analytical method that can integrate multiple physicochemical parameters and systematically monitor the seasonal changes and functional status of the pit mud.

[0004] Therefore, it is urgent to establish a multi-parameter collaborative method for analyzing the physicochemical properties of pit mud with system monitoring significance, so as to achieve scientific evaluation and process control of the fermentation state of pits. Summary of the Invention

[0005] The purpose of this invention is to provide a systematic monitoring and analysis method for the seasonal physicochemical properties of cellar mud in strong-aroma baijiu production. By integrating multi-dimensional data such as cellar mud morphology, dry / wet sample bulk density, contact angle and wetting time, and infrared spectroscopy, the method can achieve systematic monitoring and comprehensive evaluation of the physicochemical properties and functional status of cellar mud in different seasons and at different levels.

[0006] To achieve the above-mentioned objectives, the technical solution adopted in this application is as follows.

[0007] In a first aspect, the present invention provides a method for systematically monitoring and analyzing the seasonal physicochemical properties of cellar mud for strong-aroma baijiu, comprising the following steps: S1. Collect cellar mud samples from different depth levels of strong-aroma baijiu cellars in spring and autumn, respectively; S2. Conduct systematic analysis of the collected pit mud samples, including: S2-1. Characterize the morphology of the pit mud samples and obtain morphological features, including their macroscopic and microscopic structural features; S2-2. Determine the bulk density of the wet mud sample and analyze its compactness and structural differences based on the bulk density; S2-3. Using ethyl hexanoate and pure water as test media, the surface contact angle of the pit mud sample was determined by the seat drop method and the wetting time was recorded to analyze its interfacial affinity characteristics. S2-4. Fourier transform infrared spectroscopy was used to detect the pit mud samples and obtain infrared spectral data and information on their functional group composition. S3. Integrate the morphological features, bulk density, interface characteristics, and infrared spectral data obtained in step S2 to establish a database of seasonal physicochemical properties of pit mud. Based on the synergistic changes of multiple parameters, comprehensively evaluate the structural features, interface characteristics, and fermentation functional status of pit mud to achieve systematic monitoring and analysis of seasonal changes in pit mud.

[0008] In step S1 above, spring refers to March to May each year, and autumn refers to September to November each year; the different depth levels are calculated according to their distance from the surface of the pit, including an upper layer of 0 to 20 cm, a middle layer of 20 to 40 cm, and a lower layer of less than 40 cm.

[0009] In step S2-1 above, the morphological characterization includes: observing the macroscopic morphology of the wet pit mud sample using a stereomicroscope, and observing the microscopic pore structure and lamellar stacking characteristics of the dried pit mud sample using a scanning electron microscope.

[0010] In step S2-2 above, the bulk density test is performed in accordance with ASTM D7263 standard.

[0011] In steps S2-3 above, during the seat drop method determination, the temperature of the test medium is controlled at 25±1℃, and the volume of the test liquid is 2~5μL.

[0012] In steps S2-4 above, the test spectral range of the Fourier transform infrared spectrum is 4000~400cm. -1 .

[0013] In step S3 above, the comprehensive evaluation includes: The structural activity and porosity development of pit mud are assessed based on morphological characteristics. The compactness and moisture content of the pit mud are assessed based on its bulk density. The interfacial affinity of pit mud for flavor compounds and moisture was evaluated based on contact angle and wetting time. Identify the functional group composition of alcohols, acids, and esters in pit mud based on infrared spectral characteristic peaks.

[0014] In step S3 above, the multi-parameter synergistic change relationship includes the correlation between morphological characteristics, bulk density, interface properties and infrared spectral data of pit mud samples from different seasons and different levels; the correlation is used to characterize the intrinsic relationship between the structural state, moisture distribution, flavor substance affinity and metabolic activity of pit mud.

[0015] Secondly, the present invention provides the application of the above method in the maintenance of strong-aroma baijiu cellars or the control of fermentation process.

[0016] Thirdly, the present invention provides a system for the above-described method.

[0017] Compared with the prior art, the present invention has the following beneficial effects: This invention integrates four modules—morphological characterization, bulk density testing, interfacial property testing, and infrared spectroscopy analysis—to construct a multi-physicochemical parameter synergistic analysis system. This system can systematically and comprehensively reflect the changes in the physicochemical properties of fermentation pit mud in different seasons and at different levels. This method overcomes the one-sidedness of traditional single-index evaluation, comprehensively judging the functional state of fermentation pit mud from multiple dimensions such as structural characteristics, bulk properties, interfacial behavior, and molecular composition, significantly improving the scientific rigor and stability of the evaluation of fermentation state in fermentation pits. Simultaneously, this invention provides reliable monitoring data and decision-making basis for the management of strong-aroma baijiu fermentation pits, pit mud maintenance, and flavor control, possessing high industrial application value. Attached Figure Description

[0018] Figure 1 A flowchart illustrating the systematic monitoring and analysis method for the seasonal physicochemical properties of cellar mud in strong-aroma baijiu production; Figure 2 Microscopic images of wet mud samples from the bottom (a, d), middle (b, e), and top (c, f) layers of pit mud in Pit 1 of the embodiment. Figure 3 The images are scanning electron microscope (SEM) images of dry mud samples from the bottom (a, d), middle (b, e), and top (c, f) layers of pit mud in pit No. 1 in the embodiment. Figure 4 Fourier transform infrared spectra of the upper, middle and lower layers of pit mud samples from pit No. 1 in the example during spring; Figure 5 The Fourier transform infrared spectra of the upper, middle and lower layers of pit mud samples from pit No. 1 in the example are shown. Detailed Implementation

[0019] To make the technical problems, solutions, and beneficial effects of this application clearer, the following detailed description is provided in conjunction with the embodiments. Unless otherwise defined, all technical terms used herein have the same meaning as understood by one of ordinary skill in the art.

[0020] This invention provides a method for systematically monitoring and analyzing the seasonal physicochemical properties of cellar mud used in strong-aroma baijiu production. The process flow diagram is shown below. Figure 1As shown in the figure. This method integrates four modules: morphology characterization, bulk density testing, interface property testing, and infrared spectroscopy analysis. It performs multi-parameter collaborative analysis on pit mud samples from different layers in spring and autumn, realizing systematic monitoring and comprehensive evaluation of the seasonal physicochemical properties and functional status of pit mud. The specific steps are as follows.

[0021] Step 1: Sampling of pit mud: Specifically, samples of cellar mud were collected from different depths in the fermentation pits of strong-aroma baijiu during spring (March to May) and autumn (September to November). Spring and autumn are critical periods for the production of strong-aroma baijiu, with significant differences in environmental temperature and humidity conditions. The physicochemical properties of the cellar mud, such as water content, pore structure, surface characteristics, and functional group composition, exhibit obvious seasonal changes. Therefore, sampling during these two seasons can effectively capture the seasonal evolution of the physicochemical properties of the cellar mud.

[0022] During sampling, samples were collected in stratified layers at different depths from the surface of the fermentation pit. As a preferred sampling method, the pit mud samples were divided into upper, middle, and lower layers: the upper layer was 0–20 cm, the middle layer was 20–40 cm, and the lower layer was below 40 cm. Due to their different locations, the pit mud in different layers exhibited variations in contact with the yellow water, microbial community structure, and fermentation metabolic environment, resulting in a regular distribution of physicochemical properties in the vertical space. Stratified sampling reveals the spatial distribution characteristics of the pit mud's physicochemical properties, laying the foundation for subsequent stratified comparative analysis.

[0023] The collected pit mud samples should be sealed and preserved in their original state for subsequent wet sample testing and dry sample analysis.

[0024] Step 2: Conduct a systematic analysis of the collected pit mud samples, including: (1) Morphological characterization: The wet pit mud samples were observed macroscopically using a stereomicroscope, which allowed for a direct view of the composition of the pit mud, such as yellow sand grains, white calcium and magnesium salt crystals, as well as the surface texture of the sand grains and the overall looseness of the pit mud. The dried pit mud samples were observed microscopically using a scanning electron microscope to examine the microscopic pore structure and lamellar stacking characteristics, which allowed for the acquisition of microscopic morphological information, such as the stacking pattern of the nanosheet structure, the pore structure formed between the lamellars, and the degree of pore development.

[0025] The structural characteristics of fermentation pit mud directly affect its function as a carrier for microorganisms. A loose, porous structure facilitates the attachment and growth of microorganisms and provides physical space for the infiltration, penetration, and mass transfer of flavor substances in the liquid phase. Morphological characterization can determine the structural activity of the pit mud. Pit mud samples exhibiting a loose, porous structure typically possess higher structural activity and better pore development, which is more conducive to fermentation metabolism.

[0026] (2) Bulk density test: The bulk density test shall be conducted in accordance with ASTM D7263 standard. This standard is applicable to the density determination of soil samples. The method of directly measuring the size of regular samples or the wax-sealed drainage method shall be used to determine the volume. The bulk density of the wet sample shall be calculated according to the ratio of mass to volume. During the test, a wet sample of pit mud that has been kept in its original shape shall be taken, its mass shall be weighed, and its volume shall be determined by an appropriate method to obtain the bulk density data.

[0027] Bulk density reflects the mass of pit mud per unit volume and is closely related to factors such as porosity, water content, and organic matter content. Pit mud samples with relatively low bulk density usually have a looser structure and better pore development, which is conducive to microbial activity and material exchange; pit mud samples with relatively high bulk density may have better water content or a denser structure. By comparing the bulk density of pit mud samples from different seasons and different layers, the vertical distribution and seasonal variation patterns of the pit mud's structural looseness and water content can be revealed.

[0028] (3) Interface characteristics test: Under the condition of 25±1℃, ethyl hexanoate and pure water were used as test media and the test was conducted by the seat drop method. During the test, the liquid volume was controlled to be 2~5μL. The test drop was added to the surface of the pit mud sample, the drop profile was recorded by the optical system, the initial contact angle was calculated, and the wetting time required for the drop to spread completely on the pit mud surface was recorded at the same time.

[0029] The contact angle reflects the initial wetting ability of the test medium on the surface of the pit mud. The smaller the contact angle, the better the wettability and the stronger the affinity between the two. The immersion time reflects the dynamic process of wetting. The shorter the immersion time, the faster the test medium spreads on the surface of the pit mud and the higher the rate of penetration and adsorption.

[0030] By selecting different test media, interfacial information from various dimensions can be obtained: using ethyl hexanoate as the test medium, the interfacial affinity characteristics of pit mud for ester flavor compounds can be evaluated. Ethyl hexanoate is a key flavor compound in strong-aroma baijiu, and its wetting behavior on pit mud directly relates to the adsorption, enrichment, and formation efficiency of ester compounds. Using pure water as the test medium, the interfacial affinity characteristics of pit mud for water can be evaluated, indirectly reflecting the water content of the pit mud. Pit mud samples with a smaller contact angle with pure water generally have a better water content, which is conducive to maintaining microbial metabolic activity.

[0031] In specific assessments, pit mud samples with smaller contact angles and shorter wetting times are considered to have strong interfacial affinity for the corresponding test media. For example, middle-layer pit mud with a small contact angle and short wetting time for ethyl hexanoate indicates a strong affinity for ester flavor compounds, suggesting it may be a core region for ester formation and enrichment; while bottom-layer pit mud with a small contact angle for pure water indicates a relatively stable water content.

[0032] (4) Infrared spectroscopy analysis: Fourier transform infrared spectrometer was used to test the pit mud samples from different seasons and different layers. The test spectral range was 4000~400cm. -1 Within this full-band range, the complete infrared absorption spectrum of the pit mud sample can be obtained, reflecting the vibrational information of various functional groups within it.

[0033] Infrared spectroscopy analysis can reveal the molecular composition of fermentation mud, determining whether it contains fermentation-related organic matter such as alcohols, acids, and esters, and the distribution characteristics of these substances in different seasons and at different levels. The relative intensity of characteristic peaks reflects the relative content of corresponding functional groups.

[0034] Step 3: System Data Analysis and Comprehensive Evaluation By integrating the morphological features, bulk density, interfacial characteristics, and infrared spectral data obtained in step two, a database of seasonal physicochemical properties of pit mud is established. The core of this invention lies in not analyzing single parameters in isolation, but rather identifying the inherent correlations between different parameters—that is, the synergistic changes of multiple parameters—and based on these synergistic relationships, comprehensively evaluating the structural characteristics, interfacial properties, and fermentation functional state of the pit mud, thereby achieving systematic monitoring and analysis of the seasonal changes in pit mud.

[0035] First, the aforementioned multi-parameter synergistic relationship refers to the fact that the morphological characteristics, bulk density, interfacial properties, and infrared spectral data of pit mud samples from different seasons and levels are not independent of each other, but rather exhibit specific correlation patterns. The essence of this correlation lies in the inherent physicochemical connection between the microstructure, macroscopic density, interfacial behavior, and molecular composition of the pit mud, which jointly determine its fermentation functional state. For example, when the pit mud has a loose and porous microstructure, its macroscopic bulk density is often relatively low; when the pit mud exhibits a strong interfacial affinity for ethyl hexanoate, the intensity of the C=O absorption peak related to esters in its infrared spectrum is usually relatively high; when the pit mud has a good water content, its contact angle with pure water is often small, while the intensity of the OH absorption peak is high. These inherent correlations among the parameters constitute the synergistic basis for judging the functional state of the pit mud.

[0036] Then, based on the above-mentioned multi-parameter synergistic change relationship, the present invention identifies parameter combination patterns with specific orientations through comprehensive analysis of four-dimensional parameters, and then judges the functional state of the pit mud.

[0037] In one specific embodiment of the present invention, the functional state of the pit mud can be judged when multiple parameters exhibit consistent directionality. For example, if a sample simultaneously exhibits a loose and porous morphology, relatively low bulk density, a small contact angle with ethyl hexanoate, a short wetting time, and a relatively high C=O absorption peak intensity, these four parameters collectively indicate that the sample is an active region for the generation and enrichment of ester flavor substances. If a sample simultaneously exhibits a relatively high bulk density, a small contact angle with pure water, and a relatively high OH absorption peak intensity, these three parameters collectively indicate that the sample has a good water content and a high content of hydroxyl compounds. If a sample's contact angle with ethyl hexanoate is greater than its contact angle with pure water, this single comparative relationship can indicate that the pit mud has a relatively stronger affinity for ester substances.

[0038] Combining the above parameter combinations with the sampling season and sampling level can further develop a systematic understanding of the seasonal changes in pit sludge. For example, if a certain level in a particular season simultaneously exhibits characteristics such as a loose and porous morphology, low bulk density, strong affinity for ethyl hexanoate, and strong C=O peak, then that level can be identified as the core region for ester formation in that season. If it simultaneously exhibits characteristics such as high bulk density, strong affinity for pure water, and strong OH peak, then that level can be identified as a region with good water content and high hydroxyl content in that season. If samples from different levels and seasons generally show a contact angle with ethyl hexanoate that is greater than that with pure water, then the pit can be identified as having the selective enrichment capacity for ester flavor compounds.

[0039] Based on the above evaluation logic, this invention enables systematic monitoring and analysis of seasonal changes in pit mud. Through multi-dimensional collaborative analysis, it is possible to systematically monitor and scientifically evaluate the seasonal physicochemical properties and fermentation functional status of pit mud, providing a reliable basis for pit maintenance and process control. This evaluation method based on multi-parameter synergistic relationships overcomes the one-sidedness of single-index evaluation and can more comprehensively and accurately reflect the actual functional status of pit mud.

[0040] This invention also provides the application of the above-mentioned method in the maintenance or fermentation process control of strong-aroma baijiu fermentation pits. For example, by regularly conducting systematic analysis of the pit mud at different levels, the dynamic trends of the pit's physicochemical properties can be grasped: if a certain level of structure is detected to become denser and its bulk density increases, loosening treatment can be considered; if a decrease in interfacial affinity for ethyl hexanoate is found, the microbial environment of that level can be adjusted accordingly; if infrared spectroscopy shows a weakening of ester-related peak intensity, fermentation conditions can be optimized to promote esterification reactions. Through multi-parameter synergistic monitoring, precise control of the pit's health status can be achieved, improving the stability and quality of the liquor.

[0041] The following specific embodiments will be provided to explain the solution of the present invention. Those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be considered as limiting the scope of the invention. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially. Example

[0042] This embodiment aims to verify the feasibility and effectiveness of the seasonal physicochemical property monitoring and analysis method for strong-aroma baijiu cellar mud described in this invention through specific experimental data, and specifically includes the following steps.

[0043] 1. Sample collection The cellar mud samples in this embodiment were taken from the production cellars of Luzhou Laojiao Co., Ltd. in Luzhou City, Sichuan Province. Two high-quality cellars for strong-aroma baijiu were selected from the production workshop and labeled as Cellar No. 1 and Cellar No. 2, respectively. The cellar mud from the selected cellars was dark brown in color, fine in texture, and had a rich cellar aroma.

[0044] Sampling was conducted in spring and autumn on pits No. 1 and No. 2. Samples were collected in stratified layers at different depths from the pit surface: the upper layer was 0–20 cm, the middle layer was 20–40 cm, and the lower layer was below 40 cm. Samples were sealed and stored for later use.

[0045] 2. Test Methods and Results (1) Morphological characterization: Taking No. 1 pit as an example, the macroscopic morphology of its wet mud sample was observed using a stereomicroscope, such as Figure 2 As shown; the microstructure of the dried pit mud samples was observed using a scanning electron microscope, such as... Figure 3 As shown.

[0046] Depend on Figure 2 It is known that the mud in pit No. 1 is mainly composed of yellow sand particles and some white crystals, with the white crystals primarily consisting of calcium and magnesium salts. The sand particles exhibit an uneven surface, which may be related to the microbial degradation of organic matter. Stereomicroscopic images of the middle layer of mud show a more porous and fluffy structure, which is conducive to the production of flavor compounds by microorganisms.

[0047] Depend on Figure 3 It is known that the mud in pit No. 1 has a microstructure composed of stacked nanosheets, with numerous channels formed between the layers, resulting in a porosity of over 60%. This abundant pore structure facilitates the wetting, spreading, and penetration of liquids within the mud.

[0048] (2) Bulk density test: The bulk density of wet mud samples from different layers of pit No. 1 and No. 2 was determined according to the ASTM D7263 standard method. The results are shown in Table 1.

[0049] Table 1 Bulk density of wet pit mud samples from different seasons and grades (unit: g / cm³) 3 )

[0050] Test results show that the bulk density of the middle layer of pit mud is relatively low in spring, indicating that its middle layer structure is relatively loose, which may be related to the light, porous organic-biopolymers (such as extracellular polysaccharides, mycelial networks, and humic colloids) produced by microbial metabolism. The bulk density of the bottom layer of pit mud is relatively high in autumn, indicating that the bottom layer is more prone to enriching liquid phase components; while the bulk density of wet samples from the upper and middle layers of pit mud fluctuates depending on the pit conditions. These results indicate that there are stable and significant vertical physicochemical differences between different layers of pit mud in autumn, and these differences can serve as important parameters for characterizing the fermentation state and moisture distribution characteristics of the pit.

[0051] (3) Contact angle and wetting time test: Wet sample pit mud was pressed into standard sample. Under the condition of 25℃, ethyl hexanoate and pure water were used as test media. The contact angle was determined by the seat drop method, and the wetting time of ethyl hexanoate on the surface of pit mud was recorded at the same time.

[0052] The results of ethyl hexanoate testing showed that the average contact angle of the middle layer mud samples in pits No. 1 and No. 2 with ethyl hexanoate was significantly lower than that of the bottom and top layers, and the average wetting time of ethyl hexanoate on the surface of the middle layer mud was also significantly shorter than that of the bottom and top layers. This indicates that the middle layer mud has stronger interfacial wettability and affinity for ethyl hexanoate in spring, which is more conducive to the adsorption and enrichment of ethyl hexanoate. In addition, the average wetting time of ethyl hexanoate on the surface of each layer of mud was generally lower in spring than in autumn, indicating that the affinity and enrichment capacity of the mud for ethyl hexanoate are generally enhanced in spring, which is consistent with the high yield of ethyl hexanoate in spring.

[0053] Pure water testing results showed that the bottom layer of pit mud had the lowest average contact angle, followed by the middle layer, and the top layer had the highest. This indicates that the bottom layer of pit mud had a better water content, while the top layer of pit mud experienced more severe water evaporation due to long-term exposure to air.

[0054] Comparative analysis of the contact angle test results of ethyl hexanoate and pure water revealed that in spring and autumn, the average contact angle of ethyl hexanoate in different grades of pit mud samples was greater than that of pure water. This indicates that the relative affinity of pit mud surface for ethyl hexanoate is stronger than its hydrophilicity, reflecting its selective wetting and enrichment characteristics of ester flavor substances.

[0055] (4) Infrared spectroscopy analysis: Fourier transform infrared spectroscopy (FTIR) was used to analyze mud samples from different layers of pit No. 1 in spring and autumn. The spectral range was 4000~400cm. -1 The result is as follows Figure 4 (Spring) and Figure 5 As shown in (Autumn).

[0056] The following characteristic absorption peaks were observed in the infrared spectrum obtained by full-band scanning: 3622cm -1 The presence of a distinct OH stretching vibration absorption peak nearby indicates the widespread presence of substances containing hydroxyl functional groups, such as alcohols, carboxylic acids, and substances related to microbial metabolism, in the pit mud from different layers. Compared to spring samples, the peak intensity was generally higher in autumn pit mud, suggesting a relatively higher water content or hydroxyl content.

[0057] 1626~1647cm -1 A distinct absorption peak was detected within the range, which is related to the stretching vibrations of carbonyl functional groups such as esters or carboxylates. In spring, the peak intensity in the bottom layer of pit mud samples was weaker than that in the middle and upper layers; in autumn samples, the peak intensity in the middle layer of pit mud was stronger than that in the bottom and upper layers, reflecting the differences in the distribution of carbonyl-containing substances in pit mud of different seasons and layers.

[0058] 1002~1036cm -1 A CO tensile vibration peak was detected within the range, at 798 cm⁻¹. -1 Bending vibration peaks of CH bonds were detected nearby, at 520–526 cm⁻¹. -1 Low wavenumber absorption peaks associated with organic molecular skeleton vibrations or carbonyl-containing structures can be observed nearby.

[0059] Comparison of infrared spectra of mud samples from different layers revealed no significant differences in their overall spectral characteristics, indicating that each layer of mud contains similar characteristic functional groups, mainly including fermentation-related organic compounds such as alcohols, acids, esters, and ketones, including ethanol, 1-hexanol, hexanoic acid, ethyl hexanoate, and 2-pentanone. These alcohols are essential metabolic products generated during fermentation and alcohol production, while the presence of carbonyl functional groups suggests that acetic acid and ethanol produced during fermentation may undergo esterification to generate esters with typical aroma characteristics.

[0060] Comprehensive analysis shows that the mud in each layer of the No. 1 fermentation pit exhibits normal and stable fermentation and metabolic characteristics, and has the ability to convert organic substrates into ethanol, organic acids, and further generate flavor esters.

[0061] 3. Results of multi-parameter collaborative analysis By integrating and analyzing the aforementioned morphological characteristics, bulk density, interfacial properties, and infrared spectral data, specific synergistic variation patterns were found among the four dimensions of pit mud samples from different seasons and at different levels. These synergistic patterns have a clear correspondence with the fermentation functional state of the pit mud and can be used to systematically monitor the seasonal changes of pit mud, as detailed below.

[0062] (1) Synergy between structural features and bulk properties Morphological observation and bulk density testing results show that the microstructure of the pit mud is closely related to its macroscopic density. The middle layer of pit mud exhibits a loose and porous morphological characteristic, and its wet sample bulk density is relatively low (1.6348 g / cm³ in spring). 3 Autumn 1.4982g / cm 3 This indicates that the loose microstructure directly leads to the lower macro density; although the bottom layer of pit mud also has well-developed micropores, its high water content results in a higher bulk density (1.5576 g / cm³ in autumn). 3 This synergistic relationship between microstructure and macro density indicates that the bulk density parameter can comprehensively reflect the porosity and water content of the pit mud, and is a coupling manifestation of structural characteristics and bulk properties.

[0063] (2) Synergy between interfacial properties and molecular composition Contact angle testing and infrared spectroscopy analysis revealed that the interfacial behavior of the pit mud was closely related to its molecular composition. In spring, the middle layer of pit mud exhibited a smaller contact angle (significantly lower than the upper and bottom layers) and a shorter wetting time for ethyl hexanoate, while its infrared spectrum showed ester-related C=O absorption peaks (1626–1647 cm⁻¹). -1 The strength is relatively high. This synergistic relationship between "interfacial affinity and ester functional group abundance" indicates that pit mud with strong affinity for ethyl hexanoate also has a relatively rich content of ester substances, and the two together point to the ability to generate and enrich ester flavor substances.

[0064] In autumn, the bottom layer of pit mud exhibits a small contact angle with pure water, while its infrared spectrum shows an OH absorption peak (3622 cm⁻¹). -1 The strength is relatively high. This synergistic relationship between "hydrophilicity and hydroxyl abundance" indicates that pit mud with strong affinity for water also has a higher water content or hydroxyl content, and the two together reflect the water state and metabolic activity of the pit mud.

[0065] (3) The pattern of coordinated change across seasons and levels By comparing the performance of spring and autumn pit mud samples, as well as samples from different grades, across various parameters, we can identify multi-parameter combinations with specific orientations. These combinations reflect the differences in functional states of pit mud from different seasons and grades. The spring mid-layer samples from both fermentation pits No. 1 and No. 2 exhibited a loose and porous morphology, relatively low bulk density, a small contact angle with ethyl hexanoate, a short wetting time, and relatively high intensity of the C=O absorption peak related to esters in their infrared spectra. This combination of multi-parameter characteristics indicates that the spring mid-layer is the core region for the formation and enrichment of ester flavor compounds.

[0066] The autumn bottom samples from both pits No. 1 and No. 2 exhibited relatively high bulk density, small contact angle with pure water, and relatively high intensity of the OH absorption peak in the infrared spectrum. This combination of multi-parameter characteristics suggests that the bottom layer had a better water content and higher hydroxyl content in autumn, reflecting different metabolic characteristics compared to the middle layer.

[0067] The mud samples from different layers of pits No. 1 and No. 2 generally showed a larger contact angle with ethyl hexanoate than with pure water, and this characteristic remained stable in both spring and autumn. This common feature indicates that the pit mud has a relatively stronger affinity for ester flavor compounds, demonstrating its selective enrichment function of flavor compounds.

[0068] The above results indicate that by integrating four modules—morphological characterization, bulk density testing, interface characteristic testing, and infrared spectroscopy analysis—it is possible to systematically reveal the differences in physicochemical properties of pit mud at different seasons and levels, as well as their intrinsic relationships, thereby enabling effective judgment of the functional status of pit mud.

[0069] In summary, this embodiment verifies the feasibility and effectiveness of the method described in this invention through specific experimental data. Test results show that mud samples from different seasons and at different levels exhibit significant differences in morphological characteristics, bulk density, interfacial properties, and infrared spectral data, and these differences show an inherent synergistic correlation. This method can systematically and comprehensively monitor the seasonal physicochemical changes and fermentation functional status of strong-aroma baijiu fermentation mud, providing a scientific basis for assessing the health status of fermentation pits and regulating the brewing process, and has good industrial application value.

Claims

1. A systematic monitoring and analysis method for the seasonal physicochemical properties of cellar mud in strong-aroma baijiu production, characterized in that, Includes the following steps: S1. Collect cellar mud samples from different depth levels of strong-aroma baijiu cellars in spring and autumn, respectively; S2. Conduct systematic analysis of the collected pit mud samples, including: S2-1. Characterize the morphology of the pit mud samples to obtain their macroscopic and microscopic structural features; S2-2. Determine the bulk density of the wet mud sample to obtain information on its compactness and structural differences; S2-3. Using ethyl hexanoate and pure water as test media, the surface contact angle of the pit mud sample was determined by the seat drop method and the wetting time was recorded to obtain its interfacial affinity characteristics. S2-4. Fourier transform infrared spectroscopy was used to detect the pit mud samples and obtain their functional group composition information; S3. Integrate the morphological features, bulk density, interface characteristics, and infrared spectral data obtained in step S2 to establish a database of seasonal physicochemical properties of pit mud. Based on the synergistic changes of multiple parameters, comprehensively evaluate the structural features, interface characteristics, and fermentation functional status of pit mud to achieve systematic monitoring and analysis of seasonal changes in pit mud.

2. The method according to claim 1, characterized in that: In step S1, spring refers to March to May each year, and autumn refers to September to November each year; the different depth levels are calculated according to the distance from the surface of the pit, including an upper layer of 0 to 20 cm, a middle layer of 20 to 40 cm, and a lower layer of less than 40 cm.

3. The method according to claim 1, characterized in that: In step S2-1, the morphological characterization includes: observing the macroscopic morphology of the wet pit mud sample using a stereomicroscope, and observing the microscopic pore structure and lamellar stacking characteristics of the dried pit mud sample using a scanning electron microscope.

4. The method according to claim 1, characterized in that: In step S2-2, the bulk density test is performed in accordance with ASTM D7263 standard.

5. The method according to claim 1, characterized in that: In steps S2-3, during the seat drop method determination, the temperature of the test medium is controlled at 25±1℃, and the volume of the test liquid is 2~5μL.

6. The method according to claim 1, characterized in that: In steps S2-4, the test spectral range of the Fourier transform infrared spectrum is 4000~400cm. -1 .

7. The method according to claim 1, characterized in that, In step S3, the comprehensive evaluation includes: The structural activity and porosity of pit mud were assessed based on morphological characteristics. The compactness and moisture content of the pit mud are assessed based on its bulk density. The interfacial affinity of pit mud for flavor compounds and moisture was evaluated based on contact angle and wetting time. Identify the functional group composition of alcohols, acids, and esters in pit mud based on infrared spectral characteristic peaks.

8. The method according to claim 1, characterized in that, In step S3, the multi-parameter synergistic change relationship includes the correlation between morphological characteristics, bulk density, interface properties and infrared spectral data of pit mud samples from different seasons and different levels; the correlation is used to characterize the intrinsic relationship between the structural state, moisture distribution, flavor substance affinity and metabolic activity of pit mud.

9. The application of the method according to any one of claims 1 to 8 in the maintenance or fermentation process control of strong-aroma baijiu cellars.

10. A system for implementing the method according to any one of claims 1 to 8.

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