Methods, systems, devices, and media for predicting changes in higher alcohol content in fermented grains

Abstract

The present application belongs to the technical field of liquor detection, and discloses a method, system, device and medium for predicting the content change of higher alcohols in fermented grains, the method comprising: detecting CO2 and NH3 in the fermentation stage of liquor by using a near-infrared waveband and a TDLAS method, obtaining data by the TDLAS method, fitting the linear relationship between the harmonic signal amplitude and the gas concentration through the obtained spectral image, calculating the concentrations of CO2 and NH3, and predicting the content change of higher alcohols in fermented grains. The present application predicts the content change of higher alcohols in fermented grains in the fermentation stage of liquor by using a near-infrared TDLAS technology, adjusts the production process in a timely manner according to the obtained results, uses the physicochemical index data to more accurately guide the process operation in actual production, improves the liquor yield and liquor quality, realizes high-quality high yield and low consumption, and provides a train of thought for developing an online detection system for liquor fermentation.

Description

Technical Field

[0001] This invention belongs to the field of liquor detection technology, and in particular relates to a method, system, equipment and medium for predicting changes in the content of higher alcohols in liquor mash. Background Technology

[0002] Currently, baijiu, a popular alcoholic beverage, is made from sorghum or a mixture of grains through processes such as steaming, mixing with yeast, fermentation, distillation, grading and aging, and blending. The quality and style of baijiu depend on the presence of various volatile compounds, and controlling the content of these trace substances plays a crucial role in controlling its flavor. Higher alcohols are important flavor compounds in baijiu, and their levels affect its flavor and quality. Appropriate amounts of higher alcohols can enhance the richness and harmony of the baijiu, but excessive levels can negatively impact health. While my country does not have explicit standards for higher alcohol content, given the growing societal concern for health, the health-oriented approach to baijiu content has gained attention. Controlling the content of higher alcohols in baijiu mash by predicting changes in the mash content and implementing a series of regulatory measures is one of the important goals of the baijiu industry.

[0003] In the production of baijiu (Chinese liquor), the testing of the fermented mash is a crucial means of monitoring the level of process control. Currently, the testing of baijiu mash typically employs an experience-based, manual management model. This involves periodic sampling and destructive measurement methods such as physicochemical testing to measure indicators like ethanol concentration and acidity in the fermentation pits. This approach suffers from numerous problems, including a large workload, long processing time, high manpower costs, and untimely feedback of results. Existing methods for testing baijiu mash mainly include chemical analysis methods, chromatography, and near-infrared spectroscopy.

[0004] Currently, gas chromatography (GC) is generally used for the detection of higher alcohols. It is a chromatographic separation analysis method that utilizes gas as the mobile phase and is suitable for the quantitative and qualitative analysis of volatile substances. GC is widely used in the detection of physicochemical indicators in baijiu mash, offering high accuracy and effectively separating and measuring complex components in the mash. However, it requires large equipment, complex sample pretreatment, is time-consuming, and cannot provide timely feedback on changes in the physicochemical components of the mash to adjust the production process.

[0005] The near-infrared spectral region carries crucial analytical information, specifically the overtones and combination frequencies of hydrogen-containing groups in molecules. Scanning the near-infrared spectrum of a sample reveals the characteristic information of these hydrogen-containing groups. Therefore, by detecting the absorption of near-infrared light, the near-infrared absorption spectrum of a substance can be obtained. Preprocessing and optimizing the spectrum to eliminate or reduce the influence of various non-target factors allows for the establishment of models of physicochemical indicators in baijiu mash to predict the content of desired components. Tunable semiconductor laser absorption spectroscopy (TDLAS), based on Beer-Lambert's law, can obtain characteristic parameters such as temperature, concentration, pressure, and velocity of the gas along the laser's path. It boasts advantages such as high sensitivity, high reliability, and fast response. However, due to the complexity of baijiu fermentation, it remains difficult to control changes in the fermentation process and to monitor it from beginning to end. Currently, most fermentation processes allow for offline measurement of some chemical and physical parameters, but this is time-consuming and difficult to optimize in real-time. Achieving online monitoring of the entire fermentation process is challenging.

[0006] Chemical analysis methods and chromatography can only perform offline detection and cannot achieve online detection to provide timely feedback of detection information for production process control. Spectroscopic detection technology has the characteristics of fast detection speed, high detection accuracy, simultaneous detection of multiple indicators, and online monitoring, which fills the gap in the current online detection of the liquor fermentation process.

[0007] The fermentation process of baijiu (Chinese liquor) is a complex and continuous process. Traditional detection techniques for trace substances in baijiu mash require sampling and processing followed by a period of analysis. This often disrupts the integrity of the fermentation environment and prevents timely analytical results, leading to inaccurate final results. The baijiu industry's current research level on fermentation process control has not kept pace with the development of modern industrial control, and there is an urgent need for a rapid, accurate, and online detection method.

[0008] Based on the above analysis, the problems and shortcomings of the existing technology are as follows:

[0009] (1) Existing methods for detecting fermented mash are complex and time-consuming, which is time-consuming and labor-intensive and cannot achieve the purpose of online detection.

[0010] (2) Existing methods for detecting fermented mash use offline detection, which disrupts the balance of the fermentation process of baijiu mash and cannot provide real-time data for production process control. Summary of the Invention

[0011] In view of the problems existing in the prior art, the present invention provides a method, system, device and medium for predicting the changes in the content of higher alcohols in fermented mash.

[0012] This invention is implemented as follows: a method for predicting changes in the content of higher alcohols in fermented mash, the method comprising:

[0013] The near-infrared band and TDLAS method were used to detect CO2 and NH3 during the fermentation stage of Baijiu. The data were obtained by TDLAS and the linear relationship between harmonic signal amplitude and gas concentration was obtained by fitting the obtained spectral image. The concentrations of CO2 and NH3 were calculated to predict the changes in the content of higher alcohols in the mash.

[0014] Furthermore, the method for predicting changes in the content of higher alcohols in fermented mash includes the following steps:

[0015] Step 1: Gas chromatography was used to determine the content of higher alcohols in the baijiu samples at each stage. The content of CO2 and NH3 in the baijiu samples during fermentation was detected by the TDLAS method. Gas chromatography is a high-precision detection method that can perform accurate qualitative and quantitative analysis of higher alcohols.

[0016] Step two: Calculate the correlation coefficients between each component to determine the correlation between them. Establish a regression equation between CO2, NH3 and higher alcohols through partial least squares regression. The content of CO2 and NH3 can be quickly detected online. The changes in the content of higher alcohols can be observed through the established regression equation, thus realizing the function of online monitoring.

[0017] Step three involves using the TDLAS method to monitor real-time changes in CO2 and NH3 content in the baijiu mash, and then combining this with the regression equation to predict changes in higher alcohol content. This enables online prediction of higher alcohol content changes during the baijiu mash fermentation process, providing a method for automating the baijiu production process.

[0018] Furthermore, the determination of higher alcohol content in baijiu samples at each stage using gas chromatography, and the detection of CO2 and NH3 content during the fermentation process of baijiu samples using the TDLAS method, include:

[0019] CO2 and NH3 during the fermentation process of baijiu were detected using the TDLAS wavelength modulation method. At the same time, samples of the fermented mash in the fermentation tank at the same time were processed, and the content of higher alcohols in each sample was detected by gas chromatography.

[0020] Furthermore, the sampling process includes: sampling 3 times a day, with 10 days as one cycle, and sampling is carried out in 10 cycles.

[0021] Furthermore, the detection of CO2 and NH3 during the fermentation process of Baijiu using the TDLAS wavelength modulation method includes:

[0022] A DFB laser is selected as the detection light source. By modulating the laser and injecting current, the laser wavelength is periodically scanned to cover the characteristic absorption lines of CO2 and NH3. A photodetector is used to detect the attenuated light signal, and a data acquisition card is used to collect the harmonic signals. The voltage signal is converted into a digital signal, and the digital signal is analyzed and processed to obtain the detection result.

[0023] Another object of the present invention is to provide a prediction system for changes in higher alcohol content in fermented mash, which implements the method for predicting changes in higher alcohol content in fermented mash, the prediction system comprising:

[0024] The regression equation construction module is used to determine the content of higher alcohols in baijiu samples at various stages using gas chromatography, and to detect the content of CO2 and NH3 in baijiu samples using the TDLAS method; to calculate the correlation coefficient between each component, to determine the correlation between each component, and to establish the regression equation between CO2, NH3 and higher alcohols through partial least squares regression.

[0025] The CO2 and NH3 content monitoring module is used to monitor the changes in CO2 and NH3 content in Baijiu mash in real time using the TDLAS method.

[0026] The higher alcohol content change prediction module is used to predict the higher alcohol content change based on the monitored changes in CO2 and NH3 content in the baijiu mash and the regression equation.

[0027] Furthermore, the CO2 and NH3 content monitoring module includes:

[0028] A laser emission system consists of a signal generator, a laser controller, a laser, and a collimator; it is used for laser emission.

[0029] The signal receiving and processing system consists of a photodetector and a data acquisition card. It is used to detect attenuated optical signals using the photodetector, acquire harmonic signals using the data acquisition card, convert voltage signals into digital signals, and process digital signals.

[0030] The laser emitting system includes:

[0031] The signal generator is used to generate periodic low-frequency sawtooth or triangular wave scanning signals, which are then applied to the laser controller.

[0032] The laser controller is used to produce the operating temperature and current required by the laser for wavelength tuning.

[0033] The laser is a DFB laser.

[0034] Another object of the present invention is to provide a computer device, characterized in that the computer device includes a memory and a processor, the memory storing a computer program, which, when executed by the processor, causes the processor to perform the steps of the method for predicting changes in the content of higher alcohols in fermented mash.

[0035] Another object of the present invention is to provide a computer-readable storage medium storing a computer program that, when executed by a processor, causes the processor to perform the steps of the method for predicting changes in the content of higher alcohols in fermented mash.

[0036] Another objective of this invention is to provide an information data processing terminal for implementing a prediction system for changes in the higher alcohol content of the fermented mash.

[0037] Based on the above technical solutions and the technical problems solved, the advantages and positive effects of the technical solution to be protected by this invention are as follows:

[0038] This invention uses near-infrared TDLAS technology to predict changes in the content of higher alcohols in the mash during the fermentation stage of baijiu. The results are used to adjust the production process in a timely manner. In actual production, the physicochemical index data can be used to more accurately guide the process operation, thereby improving the yield and quality of the liquor and achieving the goal of high quality, high output, and low consumption. This invention provides a new approach for the development of an online detection system for baijiu fermentation.

[0039] This invention proposes a method for predicting changes in the content of higher alcohols in baijiu mash using near-infrared TDLAS technology. The method selects the near-infrared absorption spectrum of gases produced during baijiu fermentation, uses TDLAS technology to detect the required gas concentration, and then establishes a rapid online prediction model for CO2, NH3 and higher alcohols through partial least squares regression to predict the content of higher alcohols.

[0040] This invention selects wavelength modulation from TDLAS technology. Wavelength modulation introduces a high-frequency signal for modulation, obtaining only the measurement signal with the same frequency as the reference signal, thereby filtering out noise at other frequencies, improving measurement sensitivity, and avoiding interference from noise during the measurement process. Based on the Lambert-Beer law, the invention proposes a CO2 and NH3 gas detection system based on near-infrared TDLAS, where the gas selectively absorbs light of the corresponding frequency, weakening the light intensity. The detector receives the attenuated light signal, and the processing of this signal is the central design principle.

[0041] This invention uses near-infrared light for detection and applies TDLAS technology to predict the content of higher alcohols in baijiu mash during the fermentation process. It has the advantages of simple operation, non-destructive testing, and online detection capability.

[0042] This invention uses a post-processing digital signal processing algorithm to replace the lock-in amplifier, which can solve the problems of temperature drift and device aging that exist in the lock-in amplifier, improve the stability of the system, and reduce the size of the entire system.

[0043] This invention uses TDLAS technology to predict the higher alcohols generated during the fermentation process of baijiu mash. The aim is to improve the quality of the finished liquor by adjusting the production process in a timely manner by predicting the content of higher alcohols in the mash. At the same time, it provides a concept for online monitoring of the baijiu production process and offers a certain reference for the research and development and application of online baijiu production systems.

[0044] This invention utilizes TDLAS wavelength modulation technology to predict the concentration of higher alcohols, a volatile substance, during the fermentation process of baijiu (Chinese liquor). It replaces the lock-in amplifier in the TDLAS detection system with a LabVIEW post-processing digital signal processing algorithm, solving problems such as temperature drift and device aging inherent in lock-in amplifiers, thus improving system stability and reducing the overall system size. By using TDLAS technology to achieve online prediction and timely feedback of changes in higher alcohol content, this invention allows for the regulation of baijiu production processes, improving baijiu quality and controlling flavor variations, providing a theoretical basis for the development of online monitoring systems for the baijiu fermentation process.

[0045] The technical solution of this invention fills a technical gap in the industry both domestically and internationally: This invention uses near-infrared TDLAS technology to predict the changes in the content of higher alcohols during the fermentation of baijiu mash, filling the gap in the lack of online monitoring of flavor substances generated during the fermentation of baijiu mash both domestically and internationally.

[0046] Does the technical solution of this invention solve a long-standing technical problem that people have long desired to solve but have yet to succeed in? The detection of baijiu mash is a crucial step in baijiu production, as the degree of fermentation directly affects the quality and yield of the finished product. Detecting the key physicochemical components of the mash is an important means of monitoring the production process. Currently, the baijiu industry still relies on an experience-based, manual management model, which is not only labor-intensive, time-consuming, and manpower-intensive, but also results in delayed feedback and can damage the fermentation environment of the fermentation pits, compromising the quality of the finished product. Advances in science and technology have led to the emergence of various novel technologies in various industries. However, the baijiu industry's current research level on fermentation process control has not kept pace with the development of modern industrial control, urgently requiring a rapid, accurate, and online detection method. Near-infrared spectroscopy technology, due to its fast detection speed, high accuracy, and ability to enable online monitoring, has been gradually applied to the baijiu industry. However, due to the complex and continuous nature of the baijiu fermentation process, online monitoring of the fermentation process has not yet been achieved. This invention uses near-infrared TDLAS technology to predict changes in higher alcohols in baijiu mash, providing a method for online detection of the baijiu mash fermentation process. This provides strong support for the informatization and automation of baijiu quality control and offers a reference for solving the problem of online monitoring of the baijiu mash fermentation process. Attached Figure Description

[0047] Figure 1 This is a schematic diagram illustrating the principle of predicting changes in the content of higher alcohols in fermented mash, provided in an embodiment of the present invention.

[0048] Figure 2 This is a flowchart of a method for predicting changes in the content of higher alcohols in fermented mash, provided in an embodiment of the present invention.

[0049] Figure 3 This is a schematic diagram of the TDLAS gas detection system provided in an embodiment of the present invention;

[0050] Figure 4 This is a flowchart of LabVIEW-related algorithms provided in an embodiment of the present invention. Detailed Implementation

[0051] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0052] To enable those skilled in the art to fully understand how the present invention is specifically implemented, this section provides an explanatory description of the embodiments that expand upon the technical solutions of the claims.

[0053] like Figures 1-2 As shown, the method for predicting changes in the content of higher alcohols in fermented mash provided in this embodiment of the invention includes the following steps:

[0054] S101, the content of higher alcohols in baijiu samples at each stage was determined by gas chromatography, and the content of CO2 and NH3 in baijiu samples during fermentation was detected by TDLAS method;

[0055] S102, calculate the correlation coefficient between each component, determine the correlation between each component, and establish the regression equation between CO2, NH3 and higher alcohols through partial least squares regression.

[0056] S103, using the TDLAS method to monitor the changes in CO2 and NH3 content in baijiu mash in real time, combined with the regression equation, to predict the changes in higher alcohol content.

[0057] The system for predicting changes in the higher alcohol content of fermented mash provided in this embodiment of the invention includes:

[0058] The regression equation construction module is used to determine the content of higher alcohols in baijiu samples at various stages using gas chromatography, and to detect the content of CO2 and NH3 in baijiu samples using the TDLAS method; to calculate the correlation coefficient between each component, to determine the correlation between each component, and to establish the regression equation between CO2, NH3 and higher alcohols through partial least squares regression.

[0059] The CO2 and NH3 content monitoring module is used to monitor the changes in CO2 and NH3 content in Baijiu mash in real time using the TDLAS method.

[0060] The higher alcohol content change prediction module is used to predict the higher alcohol content change based on the monitored changes in CO2 and NH3 content in the baijiu mash and the regression equation.

[0061] The CO2 and NH3 content monitoring module provided in this embodiment of the invention includes:

[0062] A laser emission system consists of a signal generator, a laser controller, a laser, and a collimator; it is used for laser emission.

[0063] The signal receiving and processing system consists of a photodetector and a data acquisition card. It is used to detect attenuated optical signals using the photodetector, acquire harmonic signals using the data acquisition card, convert voltage signals into digital signals, and process digital signals.

[0064] The laser emitting system provided in this embodiment of the invention includes:

[0065] The signal generator is used to generate periodic low-frequency sawtooth or triangular wave scanning signals, which are then applied to the laser controller.

[0066] The laser controller is used to produce the operating temperature and current required for the laser and to tune the laser wavelength.

[0067] The laser is a DFB laser.

[0068] The method for predicting changes in the content of higher alcohols in fermented mash provided in this embodiment of the invention specifically includes:

[0069] This invention, based on the near-infrared band, employs TDLAS technology to detect CO2 and NH3 during the fermentation stage of baijiu (Chinese liquor). Experimental data is obtained using TDLAS, and the linear relationship between harmonic signal amplitude and gas concentration is fitted to the resulting spectral image, thereby calculating the concentrations of CO2 and NH3. This invention utilizes wavelength modulation in TDLAS technology. Wavelength modulation introduces a high-frequency signal for modulation, obtaining only the measurement signal with the same frequency as the reference signal, thus filtering out noise at other frequencies, improving measurement sensitivity, and avoiding interference from noise during the measurement process. Based on the Lambert-Beer law, the design focuses on the principle that when a laser beam passes through the gas to be detected, the gas selectively absorbs light at the corresponding frequency, weakening the light intensity. The detector receives the attenuated light signal, and processing this signal is the central idea behind the design. This leads to the proposed near-infrared TDLAS-based CO2 and NH3 gas detection system. The near-infrared TDLAS gas detection system of this invention mainly consists of two parts: a laser emission system and a signal receiving and processing section. The specific process is as follows... Figure 1 As shown.

[0070] (1) Laser Emission System. This system mainly consists of a signal generator, a laser controller, a laser, and a collimator. The signal generator produces a periodic low-frequency sawtooth or triangular wave scanning signal, which is then loaded onto the laser controller (usually, the scanning signal and modulation signal are superimposed and then loaded onto the laser controller through the external input of the signal generator; the modulation signal is generally a high-frequency sine wave or square wave, serving as frequency modulation). The laser controller outputs the required operating temperature and current for the laser, achieving wavelength tuning. A DFB laser is selected, whose output wavelength is determined by a grating placed in the active region. It has good single-mode characteristics, stable output laser, narrow linewidth, and high tuning accuracy. Currently, DFB laser technology is developing rapidly, and its wavelength range can basically cover the near-infrared region. Furthermore, its high-temperature resistance and corrosion resistance make it suitable for industrial use.

[0071] (2) Signal reception and processing section. It consists of a photodetector, a data acquisition card, and a test system based on post-processing digital signal processing algorithms.

[0072] 1.2 Higher alcohol formation pathway

[0073] Monohydric alcohols with two or more carbon atoms are collectively called higher alcohols. The higher alcohols in baijiu (Chinese liquor) are mainly isoamyl alcohols, including n-propanol, isobutanol, isoamyl alcohol, and reactive amyl alcohol. Because they are soluble in high concentrations of ethanol but insoluble in low concentrations of ethanol and water, and are oily, they are called fusel oils. Fusel oils are mainly formed by yeast through the metabolism of sugars and amino acids, and there are two main production pathways:

[0074] ① On the one hand, when a certain amino acid is abundant in the fermentation system, the excess amino acid is decomposed and metabolized to produce the corresponding higher alcohol. This pathway is called the amino acid degradation metabolic pathway (Ehrlich metabolic mechanism). It mainly involves the deamination and decarboxylation (removal of CO2) of amino acids to produce higher alcohols that have one less carbon atom than the amino acid molecule. This reaction takes place within yeast cells, and its general reaction formula is:

[0075] RCH(NH2)COOH+H2O→RCH2OH+NH3+CO2

[0076] ② When the amino acid content in the fermentation system is insufficient, yeast produces higher alcohols through the pathway of synthesizing amino acids via sugar metabolism. This pathway is called the sugar synthesis metabolic pathway (Harris metabolic mechanism). The specific reaction process is as follows: pyruvate is produced from sugar metabolism; pyruvate reacts with amino acids to produce another amino acid and another organic acid (α-keto acid); this organic acid is decarboxylated to become an aldehyde, and then reduced to a higher alcohol.

[0077] When the α-amino acid content in the fermentation system is moderate and the two pathways reach a certain coordinated ratio, the production of higher alcohols is relatively low. Currently, there is no definitive conclusion regarding the contribution of the Ehrlich and Harris metabolic pathways to the production of higher alcohols in yeast metabolism. However, results indicate that the higher alcohol production pathways have the following characteristics: In the early stages of baijiu fermentation, when the nitrogen source in the fermentation broth is sufficient, the content of higher alcohols produced by brewing yeast through amino acid catabolism increases significantly. As fermentation progresses, the content of free amino acids in the environment gradually decreases. At this time, brewing yeast will utilize the glycosynthesis pathway to generate the amino acids it needs. If the nitrogen source in the environment is insufficient, the α-keto acids formed by brewing yeast cannot be successfully synthesized into amino acids, leading to a large accumulation of α-keto acids. At this point, the glycosynthesis pathway is activated, causing the excess α-keto acids to undergo decarboxylation and reduction to generate the corresponding higher alcohols. In the baijiu production process, n-propanol, isoamyl alcohol, isobutanol, and reactive pentanol are mainly produced during the process of amino acid production through glycosynthesis, while higher alcohols such as 2-phenylethanol, tyrosol, and croterol mainly come from the degradation metabolism of the corresponding amino acids in the amino acid catabolism pathway. Studies have found that 75% of the content of isoamyl alcohol, isobutanol, and bioactive pentanol in higher alcohols comes from the sugar metabolism synthesis pathway, and 25% comes from the amino acid catabolism pathway involving leucine, valine, and isoleucine.

[0078] 1.3 Establishing a partial least squares prediction model for higher alcohols

[0079] Based on the above characteristics, gas chromatography was used to determine the content of higher alcohols in samples at each stage. According to the aforementioned formation pathway and reaction formula, the formation of higher alcohols is accompanied by the generation of NH3 and CO2. TDLAS technology was used to detect the content of CO2 and NH3, and the changes in the content of these two gases were monitored online. By calculating the correlation coefficients between each component, the correlations between them were observed. Finally, partial least squares regression was used to establish a regression equation between CO2, NH3, and higher alcohols.

[0080] 1.4 The specific implementation steps are as follows:

[0081] Step 1: TDLAS wavelength modulation technology is used to detect CO2 and NH3 during the fermentation process of Baijiu (Chinese liquor). A DFB laser is selected as the detection light source. By modulating the laser and injecting current, the laser wavelength is periodically scanned to cover the characteristic absorption spectra of the two gases. The light emitted by the laser is split into two by an optical fiber beam splitter. One beam passes through a standard instrument, is received by a photodetector, and transmitted to a computer to achieve time-domain to frequency-domain conversion. The other beam passes through a collimator and is incident on an absorption cell. Gas molecules selectively absorb the light, and the attenuated light is received by a photodetector and converted into an AC signal. Finally, the data is processed by the computer.

[0082] Step 2: When the laser beam with the modulated signal passes through the gas being tested, the gas interacts with the laser signal molecules, and the attenuated light signal is obtained after passing through a photodetector. The data acquisition card collects the harmonic signals of each order, converts the voltage signal into a digital signal, and uses a LabVIEW post-processing correlation algorithm to replace the lock-in amplifier, improving accuracy while reducing system size. The subsequent digital signal processing algorithm extracts harmonic signals of different frequencies, obtaining only signals with the same frequency or harmonics as the reference signal, which greatly reduces noise irrelevant to the entire detection process and significantly improves the signal-to-noise ratio.

[0083] The LabVIEW implementation of the post-processing correlation algorithm is as follows: First, the algorithm generates two reference signals R1(t) and R2(t), whose modulation signals have the same frequency and a phase difference of 90°, with frequencies and phases ω and ω, respectively. r θ r V(t) represents the harmonic signals acquired by the signal acquisition card. R1(t)×V(t) and R2(t)×V(t) can be obtained by passing them through low-pass filters:

[0084]

[0085]

[0086]

[0087]

[0088] Harmonic signals of different frequencies can be extracted by changing the frequency of the reference signal, that is:

[0089]

[0090]

[0091] By using this algorithm, V can be obtained respectively. 2f V 1f .

[0092] Step 3, Gas Concentration Inversion: According to Beer-Lambert Law, the modulated signal is:

[0093]

[0094] The second harmonic V of the absorbed light signal I(t) is obtained by using the Fourier series expansion theorem. 2f With the first harmonic V 1f V 2f / V 1f The relationship with volume fraction is as follows:

[0095]

[0096] Due to V 2f / V 1f The peak value corresponds to the absorption peak in the absorption spectrum of the gas being measured, and can be determined by measuring V. 2f / V 1f The peak value is used to invert the volume fraction of the measured gas.

[0097] Step 4: While monitoring the CO2 and NH3 concentrations in the fermentation tank, samples of the fermented mash were taken from the tank at the same time. Sampling was conducted three times a day, with each cycle lasting 10 days, for a total of 10 cycles. The content of higher alcohols in each sample was determined by gas chromatography.

[0098] Step 5: Detect the contents of CO2 and NH3 using TDLAS technology and monitor the changes in the contents of the two gases online. Calculate the correlation coefficients between the CO2 and NH3 contents obtained in the same time period and the detected higher alcohol contents, observe the correlation between each component, and finally establish a regression equation between CO2, NH3, and higher alcohols using partial least squares regression.

[0099] 1.5 Theoretical Support

[0100] According to Beer-Lambert's law, the attenuation of transmitted light at a specific frequency is related to the concentration of gas molecules, and this process can be expressed as:

[0101] I(υ)=I0(υ)e [-α(υ)CL] (1-1)

[0102] Where I0(v) is the initial light intensity, α(v) is the absorption spectral line, C is the gas concentration, and L is the absorption optical path. When CL is small, it can be approximated as I(υ)=I0(υ)[1-α(υ)CL].

[0103] The principle of harmonic detection is as follows:

[0104] The laser achieves wavelength modulation by using a high-frequency signal to modulate the laser light through current tuning; wavelength scanning is achieved by scanning the absorption peaks of the gas spectrum using a low-frequency signal. A cosine wave is used as the modulation signal cos(ωt), and a sawtooth wave is used as the scanning signal U(t). The Lorentz shape represents the gas absorption shape. According to the approximation of the Lambert-Beer law, the modulated signal is:

[0105]

[0106] In the formula, ω is the wavelength modulation frequency, P is the power modulation coefficient, and m is the modulation coefficient. Since sawtooth wave signals have low frequency and slow changes, and both the power modulation coefficient and the gas absorption coefficient are very small in the near-infrared band, i.e., satisfying -α(v)CL << 1 and P << 1, the above equation (1-2) can be approximated as:

[0107]

[0108] The second harmonic V of the absorbed light signal I(t) is obtained by using the Fourier series expansion theorem. 2f With the first harmonic V 1f They are respectively:

[0109] V 1f =PI0 (1-4)

[0110]

[0111] In the formula, k is a constant related to m. V 1f Related to I0(t), V 2f Related to gas concentration C. V is calculated. 2f / V 1f This eliminates the influence of I0(t) on the detection results and improves the sensitivity of gas volume fraction detection. 2f / V 1f The relationship with volume fraction is as follows:

[0112]

[0113] Due to V 2f / V1f The peak value corresponds to the absorption peak in the absorption spectrum of the gas being measured, and can be determined by measuring V. 2f / V 1f The peak value is used to invert the volume fraction of the measured gas.

[0114] Correlation coefficient calculation:

[0115] Mathematical principles of partial least squares regression

[0116] The purpose of partial least squares regression is to find certain linear combinations in the explanatory variable space that can better explain the variation information of the response variable.

[0117] Let there be q dependent variables {y1, ..., y2} q} and p independent variables {x1, ..., x} p Given n sample points, the independent variable data table X = (x1, ..., xn) is formed. p ) n×p The dependent variable data table is Y = (y1, ..., y2) q ) n×q .

[0118] Partial least squares regression extracts components t1 and u1 from X and Y respectively. For the purposes of regression analysis, the following two requirements apply when extracting these components:

[0119] (1) t1 and u1 should carry as much variation information as possible from their respective data tables;

[0120] (2) The correlation between t1 and u1 can reach its maximum.

[0121] These two requirements indicate that t1 and u1 should represent data tables X and Y as well as possible, while the independent variable component t1 should have the strongest explanatory power for the dependent variable component u1. After the first components t1 and u1 are extracted, partial least squares regression is used to regress X on t1 and Y on t1, respectively. If the regression equation has reached satisfactory accuracy, the algorithm terminates; otherwise, the residual information of X after being explained by t1 and the residual information of Y after being explained by t1 will be used for a second round of component extraction. This process is repeated until a satisfactory accuracy is achieved. If a total of m components t1, ..., t1 are extracted from X, ... m Partial least squares regression will be performed by y k ,k=1,2,···,q versus t1,···,t m The regression, and then expressed as y k Regarding the original variables x1, ..., x p The regression equation.

[0122] To demonstrate the inventiveness and technical value of the technical solution of this invention, this section provides specific product or related technology application examples of the technical solution claimed.

[0123] The light-aroma baijiu (Chinese white liquor) mash produced by a certain winery in a certain city was placed in a fermentation tank for fermentation. The fermentation tank and a near-infrared TDLAS gas detection system were then used. Figure 1 The welding process is as follows: ① Select absorption lines for CO2 and NH3 from the HITRAN spectral database, choosing lines with the highest absorption intensity and a certain interval between them and background gas absorption lines to improve measurement accuracy and avoid background gas overlap or cross-interference affecting the measurement results; ② During the 10-day fermentation process, collect CO2 and NH3 parameters of the fermentation environment using a near-infrared TDLAS gas detection system, and collect samples every 8 hours and place them in a refrigerator; ③ Send the collected samples to a gas chromatograph to detect the types and contents of higher alcohols; ④ Collect CO2 and NH3 contents in the fermentation tank environment using a near-infrared TDLAS gas detection system, collecting 3 sets of data per day, and collecting mash samples at the same time as collecting data. One cycle is 10 days, and a total of 10 fermentation cycles are repeated, resulting in 330 sets of sample data; ⑤ Divide the samples into training and test sets at a ratio of 4:1; ⑥ Perform correlation analysis between the obtained CO2 and NH3 contents and the obtained contents of each higher alcohol, and use partial least squares regression to model the correlation.

[0124] The embodiments of the present invention have achieved some positive results during the research and development or use process, and have indeed great advantages compared with the prior art. The following content describes them in conjunction with the data, charts and other information of the experimental process.

[0125] By consulting the HITRAN spectral database and comparing the gas absorption spectra of CO2 and NH3, and considering the advantages of different band tunable diode lasers in optical communication in terms of maturity, operating technology, and cost, two DFB lasers were selected, one with an output center wavelength of 1570nm and the other with an output center wavelength of 1500nm. A 5kHz sine wave modulation signal and a 20Hz sawtooth wave scanning signal generated by a signal generator were superimposed and fed into the laser controller. The laser controller output the operating temperature and current required for the DFB laser to achieve wavelength tuning. In order to stabilize the laser temperature as much as possible and keep the laser temperature control temperature as close as possible to the current room temperature, a temperature of 25℃ was selected as the laser stabilization temperature. Then, the gas content was measured according to the above steps.

[0126] After the near-infrared TDLAS gas acquisition system was set up, the detection accuracy of the system was tested. A pre-configured background gas of N2 and a certain concentration of standard CO2 gas was introduced into the gas cell, and the concentration of the introduced standard gas was detected under a standard environment of 25℃. The detection results are shown in Table 1.

[0127] Table 1. Detection results of CO2 under standard conditions with N2 as the background gas.

[0128]

[0129] In actual gas concentration detection, the concentration is determined by comparing the peak value of the obtained second harmonic signal with the peak value of the second harmonic signal of the standard gas. By detecting standard CO2 gas at different concentrations, it can be observed that the detection error of the near-infrared TDLAS gas detection system of this invention is within ±2%, but the error gradually increases as the gas concentration decreases. When the gas concentration is high, the peak value of the obtained second harmonic signal is also high, and the interference signal is relatively weak, resulting in a high signal-to-noise ratio for the system. When the gas concentration is low, the second harmonic signal generated by the absorption of near-infrared light by the gas is small, so the magnitude of the interference signal has a greater impact on the detection result, and the signal-to-noise ratio of the system decreases. However, overall, the measurement error of this system is small, and it can realize the detection of CO2 and NH3 during the fermentation process of baijiu (Chinese liquor).

[0130] This invention applies the TDLAS gas detection system to detect the concentrations of CO2 and NH3 during the fermentation of Baijiu mash. Gas chromatography is used to perform qualitative and quantitative analysis of higher alcohols in mash samples from the same stage of the gas collection system. The obtained CO2 and NH3 contents are correlated with the contents of each higher alcohol. Finally, partial least squares regression is used to establish a model to achieve online monitoring of changes in higher alcohol content during the fermentation of Baijiu mash.

[0131] It should be noted that embodiments of the present invention can be implemented in hardware, software, or a combination of both. The hardware portion can be implemented using dedicated logic; the software portion can be stored in memory and executed by a suitable instruction execution system, such as a microprocessor or dedicated-design hardware. Those skilled in the art will understand that the above-described devices and methods can be implemented using computer-executable instructions and / or included in processor control code, for example, such code provided on a carrier medium such as a disk, CD, or DVD-ROM, a programmable memory such as read-only memory (firmware), or a data carrier such as an optical or electronic signal carrier. The devices and modules of the present invention can be implemented by hardware circuitry such as very large-scale integrated circuits or gate arrays, semiconductors such as logic chips, transistors, or programmable hardware devices such as field-programmable gate arrays, programmable logic devices, etc., or by software executed by various types of processors, or by a combination of the above-described hardware circuitry and software, such as firmware.

[0132] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent substitutions, and improvements made by those skilled in the art within the scope of the technology disclosed in the present invention, and within the spirit and principles of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for predicting changes in the content of higher alcohols in fermented mash, characterized in that, Includes the following steps: Step 1: Gas chromatography was used to determine the content of higher alcohols in the baijiu samples at each stage, and the content of CO2 and NH3 in the baijiu samples during fermentation was detected by the TDLAS method. Step 2: Calculate the correlation coefficients between each component to determine the correlation between each component, and establish the regression equation between CO2, NH3 and higher alcohols through partial least squares regression. Step 3: Real-time monitoring of CO2 and NH3 content changes in baijiu mash using the TDLAS method, combined with the regression equation, is used to predict changes in higher alcohol content.

2. The method for predicting changes in the content of higher alcohols in fermented mash as described in claim 1, characterized in that, The method employed gas chromatography to determine the content of higher alcohols in baijiu samples at each stage, and the method used TDLAS to detect the content of CO2 and NH3 during the fermentation process of baijiu samples, including: CO2 and NH3 during the fermentation process of baijiu were detected using the TDLAS wavelength modulation method. At the same time, samples of the fermented mash in the fermentation tank at the same time were processed, and the content of higher alcohols in each sample was detected by gas chromatography.

3. The method for predicting changes in the content of higher alcohols in fermented mash as described in claim 2, characterized in that, The sampling process includes: sampling 3 times a day, with 10 days as one cycle, and the sampling is carried out in 10 cycles.

4. The method for predicting changes in the content of higher alcohols in fermented mash as described in claim 2, characterized in that, The method of using TDLAS wavelength modulation to detect CO2 and NH3 during the fermentation process of Baijiu includes: A DFB laser is selected as the detection light source. By modulating the laser and injecting current, the laser wavelength is periodically scanned to cover the characteristic absorption lines of CO2 and NH3. A photodetector is used to detect the attenuated light signal, and a data acquisition card is used to collect the harmonic signals. The voltage signal is converted into a digital signal, and the digital signal is analyzed and processed to obtain the detection result.

5. A system for predicting changes in higher alcohol content in fermented mash, implementing the method for predicting changes in higher alcohol content in fermented mash as described in any one of claims 1-4, characterized in that, The system for predicting changes in the higher alcohol content of the fermented mash includes: The regression equation construction module is used to determine the content of higher alcohols in baijiu samples at various stages using gas chromatography, and to detect the content of CO2 and NH3 in baijiu samples using the TDLAS method; it calculates the correlation coefficients between various components, determines the correlation between various components, and establishes regression equations between CO2, NH3 and higher alcohols through partial least squares regression. The CO2 and NH3 content monitoring module is used to monitor the changes in CO2 and NH3 content in Baijiu mash in real time using the TDLAS method. The higher alcohol content change prediction module is used to predict the higher alcohol content change based on the monitored changes in CO2 and NH3 content in the baijiu mash and the regression equation.

6. The prediction system for changes in higher alcohol content in fermented mash as described in claim 5, characterized in that, The CO2 and NH3 content monitoring module includes: A laser emission system consists of a signal generator, a laser controller, a laser, and a collimator; it is used for laser emission. The signal receiving and processing system consists of a photodetector and a data acquisition card. It is used to detect attenuated optical signals using the photodetector, acquire harmonic signals using the data acquisition card, convert voltage signals into digital signals, and process digital signals. The laser emitting system includes: The signal generator is used to generate periodic low-frequency sawtooth or triangular wave scanning signals, which are then applied to the laser controller. The laser controller is used to produce the operating temperature and current required by the laser for wavelength tuning. The laser is a DFB laser.

7. A computer device, characterized in that, The computer device includes a memory and a processor. The memory stores a computer program that, when executed by the processor, causes the processor to perform the steps of the method for predicting changes in the content of higher alcohols in fermented mash as described in any one of claims 1-4.

8. A computer-readable storage medium storing a computer program, which, when executed by a processor, causes the processor to perform the steps of the method for predicting changes in the content of higher alcohols in fermented mash as described in any one of claims 1-4.

9. An information data processing terminal, characterized in that, The information data processing terminal is used to implement the prediction system for changes in the higher alcohol content of fermented mash as described in any one of claims 5-6.

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