CN109490349B - Low-field nuclear magnetic nondestructive analysis method for detecting water activity of white spirit wine - Google Patents
Low-field nuclear magnetic nondestructive analysis method for detecting water activity of white spirit wine Download PDFInfo
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- CN109490349B CN109490349B CN201910038710.6A CN201910038710A CN109490349B CN 109490349 B CN109490349 B CN 109490349B CN 201910038710 A CN201910038710 A CN 201910038710A CN 109490349 B CN109490349 B CN 109490349B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N24/00—Investigating or analyzing materials by the use of nuclear magnetic resonance, electron paramagnetic resonance or other spin effects
- G01N24/08—Investigating or analyzing materials by the use of nuclear magnetic resonance, electron paramagnetic resonance or other spin effects by using nuclear magnetic resonance
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A90/00—Technologies having an indirect contribution to adaptation to climate change
- Y02A90/30—Assessment of water resources
Abstract
the invention discloses an analysis method for low-field nuclear magnetic nondestructive detection of water activity, and belongs to the technical field of analytical chemistry. Firstly, establishing a standard equation between the real water activity of a sample and a first peak point value of an attenuation curve obtained by detecting the sample by a low-field nuclear magnetic method; when a sample to be detected is detected, the sample is detected by a low-field nuclear magnetic method to obtain a first peak value of an attenuation curve of the Daqu sample, and then the obtained first peak value is substituted into a standard equation to obtain the water activity of the sample to be detected. The method of the invention lays a foundation for rapid, nondestructive and online detection of water activity of the sample.
Description
Technical Field
the invention belongs to the technical field of analytical chemistry, and particularly relates to a low-field nuclear magnetic nondestructive analysis method for detecting the water activity of white spirit.
Background
The yeast is the bone of the liquor, and the Daqu plays an important role in the production of Maotai-flavor liquor, Luzhou-flavor liquor and other white spirits. The preparation aims to provide a multifunctional bacterial system, a multienzyme system, a plurality of flavor substances and precursors thereof for white spirit fermentation, and the multifunctional bacterial system, the multienzyme system, the flavor substances and the precursors thereof also serve as partial raw materials. In the process of producing the yeast for making hard liquor, bacteria and saccharomycetes firstly grow in a block, so that the temperature of a yeast core is increased, heat and moisture are dissipated to form a surface layer suitable for growth of mould, and the mould starts to grow on the surface layer; then, as the water is diffused, the mould is grown in, the curved surface is gradually dried to form a closed layer, the biological heat diffusion generated by the fermentation of multiple strains in the yeast is blocked, a higher 'top fire temperature' is formed, and various flavor substances and precursors thereof are also generated at the moment.
In order to achieve the aim, the traditional process adopts strategies such as yeast pressing, microorganism enrichment (natural ventilation and the like), house merging, pile collection and the like, and on the basis of natural enrichment, the space density of yeast blocks is gradually increased to improve the yeast temperature, so that the aims of naturally purifying a bacterial system and an enzyme system and discharging water are fulfilled. However, once the fermentation is abnormal, the moisture of the yeast is not discharged, a 'water nest' phenomenon is formed, and the moisture of the yeast core is too high, so that the yeast is infected with mixed bacteria in the later storage process, and the quality and the safety of the yeast are seriously influenced. In conventional analysis, water content is usually detected, and as one of the basic parameters, the state of fermentation progress can be represented to a certain extent. However, in the actual fermentation process, macromolecular substances (starch, protein and the like) and small molecular substances (glucose, amino acid and the like) hydrolyzed by the macromolecular substances can interact with water, and the physicochemical properties and the microbial properties of the substrate are obviously influenced. In particular in solid substrates with a low water content per se, the level of water alone has a limited characterization of the fermentation state due to the high content of soluble substances. The water activity is the active part of the water content in the substrate and is a key parameter influencing the growth and metabolism of microorganisms, and different microorganisms have different optimal and minimum water activities. Therefore, the monitoring of the water activity of the yeast is a more important means for inspecting and controlling the quality of the yeast. At present, in the actual production process, due to the limitation of a technical method, online rapid detection cannot be realized, so that the development of an online nondestructive analysis technology is crucial to the rapid and efficient detection of the water activity of the yeast.
At present, nuclear magnetic resonance is widely applied to researches on water distribution and migration (between bound water and free water), plant physiology, polymer glass transition and the like in food and biological systems. According to the principle of nuclear magnetic resonance spectroscopy, relaxation signals are related to the number of spin nuclei, and although some reports for measuring the oil and water contents of grain particles and the like exist, the reports are only directed to small-volume raw materials and are focused on water content detection, and are not suitable for detecting the water activity of relatively large-volume curved blocks or other samples. Although the prior art also has a method for detecting water activity, the detection is slow, and especially a sample with low water content needs several minutes to dozens of minutes; the detection system is also small, only dozens of milliliters of samples are generally used, the samples are destructive, the samples need to be crushed and then detected, and the process can cause the change of water activity, so that the application range of the sample is limited.
Disclosure of Invention
In order to solve the problems, the invention provides an analysis method for quickly and nondestructively detecting the water activity of the white spirit wine by low-field nuclear magnetic resonance, which fills the blank of nondestructively and online detecting the water activity.
The invention relates to an analysis method for detecting the water activity of white spirit distiller's yeast by low-field nuclear magnetic nondestructive, which is characterized by firstly establishing a standard equation between the real water activity of a white spirit distiller's yeast sample and the initial peak value of an attenuation curve obtained by detecting the sample by a low-field nuclear magnetic method; when detecting the liquor koji sample to be detected, firstly detecting the sample by using a low-field nuclear magnetic method to obtain a first peak value of an attenuation curve of the sample, and then substituting the obtained first peak value into a standard equation to obtain the water activity of the liquor koji sample to be detected.
the method of the invention can be applied to the detection of the liquor koji sample with a smaller system, such as: xiaoqu or bran koji, can also be used for the detection of samples with larger volume, such as: the yeast for making hard liquor includes common yeast for making hard liquor, package yeast for making hard liquor (a high-temperature yeast for making hard liquor) and so on, and has wider application range. Preferred samples are: daqu, more preferably ordinary Daqu.
The method can be applied to tracking analysis of the water activity of the white spirit distiller's yeast, can predict the fermentation degree (maturity) of the white spirit distiller's yeast, pre-judge the quality of the white spirit distiller's yeast, improve the production efficiency and stability, and has profound significance for realizing mechanical, automatic and intelligent manufacture of the white spirit distiller's yeast.
In one specific embodiment, the standard equation established by the invention is:
Wherein: a iswDenotes water activity, comprehensive R2When M is equal to 0.98, the mass of the sample to be measured is Kg; p is the initial peak value with the unit of 1, and e is the base number of the natural logarithm function.
The standard equation established by the invention has high detection accuracy, simple parameters and wide application range.
In one embodiment, the low-field nmr detection is a CPMG sequence analysis using a nmr analyzer.
In one embodiment, the method employs a low-field nuclear magnetic resonance apparatus: the field intensity is 0.3-0.4T, the diameter of the coil is 200-400 mm, the frequency is 10-15 MHz, and the temperature is controlled within the range of 30-35 ℃.
in one embodiment, the method employs a low-field nuclear magnetic resonance apparatus: the field intensity is 0.35T, the diameter of the coil is 300mm, the frequency is 12.80MHz, and the temperature is controlled within the range of 31.99-32.01 ℃.
In one embodiment, the method uses a low field nuclear magnetic resonance spectrometer as MacroMR12-150H-I, manufactured by Nymi, Suzhou.
In one embodiment, the specific parameters of the CPMG sequence analysis are: 90 ° pulse width P1: 3-6 mu s; 180 ° pulse width: 5-10 mu s; receiver bandwidth SW: 100-500 KHz; oversampling wait time TW: 100-500 ms; time delay DL 1: 0.01 to 1; pre-amplification gain PRG: 1-8; analog gain RG 1: 5-20; digital gain DRG 1: 1-5; echo number Echonum: 2000-6000; number of oversampling NS: 10 to 30.
In a preferred embodiment, the specific parameters of the CPMG sequence analysis are: 90 ° pulse width P1: 4 mu s; 180 ° pulse width: 8 mu s; receiver bandwidth SW: 333.33 KHz; oversampling wait time TW: 300 ms; time delay DL 1: 0.15; pre-amplification gain PRG: 3; analog gain RG 1: 10; digital gain DRG 1: 3; echo number Echonum: 4000; number of oversampling NS: 16.
In one embodiment, the method of the present invention comprises the steps of:
(1) selecting a liquor distiller's yeast sample to be detected, and weighing the mass W of the sample;
(2) Detecting by adopting a low-field nuclear magnetic method to obtain a first peak value P of the attenuation curve;
(3) substituting the initial peak point value P and the sample mass W into a standard equation to calculate the water activity a of the white spiritw。
the standard equation in step (3) can be as described above.
the method uses low-field nuclear magnetic equipment, under the condition of determining equipment parameters, utilizes a CPMG sequence analysis means to carry out equipment calibration on the semaphore (initial peak point) of a T2 spectrum, and establishes an initial peak value and a white spirit distiller's yeast water activity standard equation so as to rapidly determine the comprehensive water activity of a sample. Compared with the prior art, the invention has the beneficial effects that:
(1) According to the method, a low-field nuclear magnetic analysis technology is applied to the water activity analysis of the white spirit distiller's yeast, the water activity of the white spirit distiller's yeast sample can be directly measured, and the method has non-destructive (no-destructive) and non-invasive (non-invasive), does not cause physical damage and chemical pollution to the sample, and provides a basis for nondestructive online water activity detection of the sample;
(2) The method disclosed by the invention is rapid, accurate and visual in measurement, can detect 4-5 samples within one minute, realizes the effect of measuring a large number of samples in a short time, improves the efficiency, can realize more rapid reflection of the fermentation state by efficient detection in the actual production process, and is beneficial to timely adjustment of fermentation process parameters;
(3) The method is generally not limited by the state, shape and size of the sample (only the sample is ensured not to exceed the diameter of the radio frequency coil), and the problem of detecting the water activity of the whole sample with larger volume is solved;
(4) The method can realize real-time online measurement and provide method support for monitoring the change of the water activity in real time in the production and fermentation process of the white spirit distiller's yeast sample.
Detailed Description
The invention is further described with reference to the following examples, but is not intended to be limited thereto. The experimental procedures in the following examples are conventional unless otherwise specified. The test materials used in the following examples were purchased from a conventional biochemical reagent store unless otherwise specified.
example 1:
1. Purpose of the experiment
And detecting the overall water activity of the target Daqu sample.
2. Test materials
Daqu sample (after yeast block and crushing).
3. Testing instrument
Low field nuclear magnetic resonance apparatus: MacroMR12-150H-I, manufactured by Newmai, Suzhou, with a field strength of 0.35T, a coil diameter of 300mm, a frequency of 12.80MHz, and a temperature controlled in the range of 31.99-32.01 ℃; water activity detector: aquala TDL, manufactured by Decagon Devices.
4. Procedure of the test
(1) respectively taking 3 blocks of any immature yeast and mature yeast, numbering as I-1, I-2, I-3 (immature yeast) and II-1, II-2, II-3 (mature yeast), accurately weighing, directly (without crushing), firstly using a MacroMR12-150H-I nuclear magnetic resonance analyzer to perform CPMG sequence analysis and detection to obtain a first peak value P, then substituting the first peak value into the following equation, and calculating to obtain the predicted water activity, wherein the numbers are respectively I-1, I-2, I-3 (immature yeast) and II-1, II-2 and II-3 (mature yeast); the specific parameters of CPMG sequence analysis are as follows: 90 ° pulse width P1: 4 mu s; 180 ° pulse width: 8 mu s; receiver bandwidth SW: 333.33 KHz; oversampling wait time TW: 300 ms; time delay DL 1: 0.15; pre-amplification gain PRG: 3; analog gain RG 1: 10; digital gain DRG 1: 3; echo number Echonum: 4000; number of oversampling NS: 16.
Wherein: a iswDenotes water activity, comprehensive R2When M is equal to 0.98, the mass of the sample to be measured is Kg; p is the initial peak value with the unit of 1, and e is the base number of the natural logarithm function.
(2) And (2) crushing all parts of the 6 Daqu blocks in the step (1), and measuring the real water activity by using a standard water activity detection instrument (Aquala TDL) to obtain the real water activities of the immature Daqu and the mature Daqu, wherein the real water activities are shown in table 1.
TABLE 1 actual Water Activity and initial Peak Point value of Daqu sample
according to the test data results (table 1), the relative error between the actual value and the calculated value is within 1%, which shows that the low-field nuclear magnetic resonance detection can provide a rapid and nondestructive detection method for measuring the water activity of the Daqu, and the method only needs 15-20 s for detecting the sample, thereby providing a method support for monitoring the change of the water activity in real time in the production and fermentation process of the Daqu or similar samples.
In conclusion, the method can detect the water activity of the yeast in real time, can predict the fermentation degree (maturity) of the yeast quickly, further accurately and prejudge the quality of the yeast, improve the production efficiency and stability, and has profound significance for realizing the mechanized, automatic and intelligent manufacture of the yeast.
Although the present invention has been described with reference to the preferred embodiments, it should be understood that various changes and modifications can be made therein by those skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.
Claims (10)
1. An analysis method for detecting the water activity of the white spirit distiller's yeast by low-field nuclear magnetic nondestructive testing is characterized in that a standard equation between the real water activity of the white spirit distiller's yeast sample and the initial peak value of an attenuation curve obtained by detecting the sample by a low-field nuclear magnetic method is established in advance; when detecting a liquor koji sample to be detected, detecting the sample by using a low-field nuclear magnetic method to obtain a first peak value of an attenuation curve of the sample, and substituting the obtained first peak value into a standard equation to obtain the water activity of the liquor koji sample to be detected; the standard equation is as follows:
Wherein: a iswDenotes water activity, comprehensive R2when M is equal to 0.98, the mass of the sample to be measured is Kg; p is the initial peak value with the unit of 1, and e is the base number of the natural logarithm function.
2. The method of claim 1, wherein the sample is a koji, a bran koji, or a daqu.
3. the method of claim 1, wherein the sample is a daqu.
4. the method of claim 1, wherein the low-field nmr detection is CPMG sequencing with a nmr analyzer.
5. the method of claim 1, wherein the method uses a low-field nmr apparatus: the field intensity is 0.3-0.4T, the diameter of the coil is 200-400 mm, the frequency is 10-15 MHz, and the temperature is controlled within the range of 30-35 ℃.
6. The method of claim 5, wherein the method employs a low-field nuclear magnetic resonance apparatus: the field intensity is 0.35T, the diameter of the coil is 300mm, the frequency is 12.80MHz, and the temperature is controlled within the range of 31.99-32.01 ℃.
7. The method of claim 1, wherein the method uses a low field nuclear magnetic resonance spectrometer from MacroMR12-150H-I, manufactured by Nymi, Suzhou.
8. The method of claim 4, wherein the specific parameters of the CPMG sequence analysis are: 90 ° pulse width P1: 3-6 mu s; 180 ° pulse width: 5-10 mu s; receiver bandwidth SW: 100-500 KHz; oversampling wait time TW: 100-500 ms; time delay DL 1: 0.01 to 1; pre-amplification gain PRG: 1-8; analog gain RG 1: 5-20; digital gain DRG 1: 1-5; echo number Echonum: 2000-6000; number of oversampling NS: 10 to 30.
9. The method of claim 8, wherein the specific parameters of the CPMG sequence analysis are: 90 ° pulse width P1: 4 mu s; 180 ° pulse width: 8 mu s; receiver bandwidth SW: 333.33 KHz; oversampling wait time TW: 300 ms; time delay DL 1: 0.15; pre-amplification gain PRG: 3; analog gain RG 1: 10; digital gain DRG 1: 3; echo number Echonum: 4000; number of oversampling NS: 16.
10. The method of claim 2, comprising the steps of:
(1) Selecting a liquor distiller's yeast sample to be detected, and weighing the mass W of the sample;
(2) detecting by adopting a low-field nuclear magnetic method to obtain a first peak value P of the attenuation curve;
(3) Substituting the initial peak point value P and the sample mass W into a standard equation to calculate the water activity a of the white spiritw。
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