阅读说明：本技术 一种基于低场核磁共振的真空油炸杏鲍菇条水分油脂快速检测技术 (Vacuum fried pleurotus eryngii strip moisture and grease rapid detection technology based on low-field nuclear magnetic resonance ) 是由 任爱清 林芳 唐小闲 邓珊 于 2020-12-21 设计创作，主要内容包括：本发明涉及检测技术领域,且公开了一种基于低场核磁共振的真空油炸杏鲍菇条水分油脂快速检测技术,包括以下步骤：检测物预处理：挑选无霉烂、无机械损伤的杏鲍菇,将杏鲍菇用清水漂洗2～3次,切成6mm×6mm×40mm的条状。该基于低场核磁共振的真空油炸杏鲍菇条水分油脂快速检测技术,建立了T2弛豫参数峰面积与水分、油脂之间的关系方程,所得的回归方程具有较高的拟合度,通过峰面积与能准确、快速地测定杏鲍菇条真空油炸过程中任一时刻的水分及油脂变化规律。利用MRI将核磁共振信号进行可视化,直观监测到真空油炸过程中水分、油脂的分布情况,低场核磁共振技术可快速、准确的测定果蔬真空油炸过程中水分和油脂快含量。(The invention relates to the technical field of detection, and discloses a vacuum fried pleurotus eryngii strip moisture and grease rapid detection technology based on low-field nuclear magnetic resonance, which comprises the following steps: pretreatment of a detected object: selecting pleurotus eryngii without mildew and rot and mechanical damage, rinsing the pleurotus eryngii with clean water for 2-3 times, and cutting the pleurotus eryngii into strips of 6mm multiplied by 40 mm. According to the vacuum fried pleurotus eryngii strip moisture and grease rapid detection technology based on low-field nuclear magnetic resonance, a relation equation between the peak area of a T2 relaxation parameter and moisture and grease is established, the obtained regression equation has high fitting degree, and the moisture and grease change rule at any moment in the vacuum frying process of pleurotus eryngii strips can be accurately and rapidly measured through the peak area. The nuclear magnetic resonance signals are visualized by using MRI, the distribution conditions of water and grease in the vacuum frying process are visually monitored, and the low-field nuclear magnetic resonance technology can quickly and accurately measure the water and grease content in the vacuum frying process of fruits and vegetables.)

1. A vacuum fried pleurotus eryngii strip moisture and grease rapid detection technology based on low-field nuclear magnetic resonance is characterized by comprising the following steps:

1) pretreatment of a detected object: selecting pleurotus eryngii without mildew and rot and mechanical damage, rinsing the pleurotus eryngii with clean water for 2-3 times, cutting the pleurotus eryngii into strips with the thickness of 6mm multiplied by 40mm, blanching the cut pleurotus eryngii strips in boiling water at 900 ℃ for 3min, draining water on the surfaces of the pleurotus eryngii strips, adding 40L of soybean oil into vacuum frying equipment, opening a steam heating valve, heating the soybean oil to the temperature of 90 ℃, opening a sealing door of a fryer, putting processed 300g of shiitake slices into an oil frying basket, closing the sealing door and a vacuum valve, opening a vacuum pump, putting the oil frying basket down when vacuumizing is carried out to the vacuum degree of 0.090MPa, then starting vacuum frying, setting the frying time, then carrying out deoiling on the fried pleurotus eryngii strips, carrying out deoiling at the deoiling speed of 300r/min, carrying out deoiling time of 3min, opening the vacuum valve and the sealing door after the deoiling is finished, and taking out products to be tested;

2) collecting data of a test sample: when the measurement temperature range is 31.99-32.01 ℃, collecting samples once every 2min, placing the samples in a nuclear magnetic tube and the center of a magnet coil, firstly obtaining the center frequency of the samples by using an FID sequence, then measuring the transverse relaxation time T2 in the samples by using a CPMG pulse sequence, repeatedly collecting signals of each sample for three times, and averaging the results;

3) establishing a data chart: the sample is placed in the center of the magnet coil for signal acquisition, and a visual information table is obtained by using an SE sequence in nuclear magnetic resonance imaging software. Performing NMR imaging every 2min, and acquiring signal data of transverse relaxation time of pleurotus eryngii under different frying time through a CPMG sequence echo peak point diagram;

4) and (5) rapidly and comparatively detecting the detection object.

2. The vacuum fried pleurotus eryngii strip moisture and grease rapid detection technology based on low-field nuclear magnetic resonance as claimed in claim 1, wherein in step two, the parameters of the CPMG pulse sequence are set as: the main frequency SF1 is 23MHz, the offset frequency O1 is 416765.87KHz, the 90 ° pulse time P90 is 10 μ s, the 180 ° pulse time P180 is 20 μ s, the number of sampling points TD is 150000, the number of accumulations is 8, the echo time TE is 300ms, and the number of echoes is 5000.

3. The vacuum fried pleurotus eryngii strip moisture and grease rapid detection technology based on low-field nuclear magnetic resonance as claimed in claim 1, characterized in that the nuclear magnetic resonance imaging parameters in step three are set as follows: the main frequency SF1 is 18MHz, the offset frequency O1 is 159.609131kHz, the number of sampling points TD is 256, the sampling frequency SW is 20kHz, the sampling time DW is 50 μ s, the total signal sampling time ACQ is 12.8ms, the receiver dead time DT2 is 1.4ms, the analog gain RG1 is 20dB, the digital gain DRG1 is 3dB, the layer selection direction GsliceY is 1, the phase encoding direction gchasez is 1, the frequency encoding direction GreadX 1, the 90 ° pulse width P1 is 1200 μ s, the 180 ° pulse width P2 is 1200 μ s, the 90 ° pulse width RFA1 is 3%, the 180 ° pulse width RFA2 is 6%, the radio frequency pulse shape RFSH1 is 5sinc256, the number of repeated sampling times NS 4, the number of times of repeated sampling RP1, and the number of times of accumulated cot 2.

4. The vacuum fried pleurotus eryngii strip moisture and grease rapid detection technology based on low-field nuclear magnetic resonance as claimed in claim 1, wherein to ensure high accuracy of data, the obtained peak area and transverse relaxation time are standardized to obtain the peak area and transverse relaxation time corresponding to each unit mass of sample, and the peak area A is₂And transverse relaxation time T₂The normalization process can be expressed as:

in the formula: a. the_tAnd T_tRespectively the peak area and transverse relaxation time/ms after t moment inversion; a. the₂And T₂Respectively the peak area and transverse relaxation time/ms after the standardization treatment at the time t; m₂Is the mass/g of the corresponding pleurotus eryngii strips,

the average initial water content of the pleurotus eryngii is 86.79% by measuring the water content of the pleurotus eryngii by an MB90 type rapid moisture meter, and the water content of the dry pleurotus eryngii is calculated according to the formula (3):

in the formula, M is dry basis water content, g/g, when the pleurotus eryngii is fried to t time; w-moisture content of wet base when vacuum frying pleurotus eryngii to t moment, g/g^[16]. All water contents are expressed in dry basis (%). Repeating the measurement for 3 times, and taking an average value;

fat content was determined by Soxhlet extraction according to the method specified in GB 5009.6-2016, and all oil contents are expressed in dry basis (%), and 3 experiments were repeated, taking the average of 3.

5. The vacuum fried pleurotus eryngii strip moisture and grease rapid detection technology based on low-field nuclear magnetic resonance as claimed in claim 1, wherein the analysis processing of test data uses SPSS 19.0 software, and a, b, c, d, f, g and h represent significant differences at a level of P < 0.05. Each experiment was repeated three times and the results are expressed as mean ± SD.

Technical Field

The invention relates to the technical field of detection, in particular to a vacuum fried pleurotus eryngii strip moisture and grease rapid detection technology based on low-field nuclear magnetic resonance.

Background

The low-temperature vacuum frying technology utilizes the principle that the water vaporization temperature is reduced under the negative pressure state to ensure that food is quickly dehydrated at low temperature, and meanwhile, the low-temperature vacuum frying technology can generate a loose and porous texture and endow the food with pleasant flavor.

The vacuum frying technology has the characteristics of low oxygen and low temperature, reduces the oxidation deterioration of grease and the generation of carcinogens such as acrylamide and the like, simultaneously maintains the original color, aroma, taste and nutritional ingredients of the product, has high puffing degree, crisp mouthfeel and low oil content, has wide applicability, and meets the consumption requirements of people on food nutrition, health and delicacy.

The pleurotus eryngii is rich in nutrition, thick in mushroom meat and crisp and tender in texture, large-scale industrial cultivation is started in Zhejiang, Fujian, Shanxi and the like, seasonal limitation is broken through, annual production can be realized, and the vacuum frying instant pleurotus eryngii crisp chips are suitable for being produced by vacuum frying.

The oil content of fried foods is an important factor influencing the acceptance of consumers, and a large number of studies show that excessive intake of oil can cause many chronic diseases such as cancer, cardiovascular diseases, diabetes, obesity, hypertension and the like.

The traditional oil and fat determination adopts a Soxhlet extraction method, which is long in time consumption and consumes a large amount of organic solvent. Therefore, it is urgently needed to establish a quick, convenient and accurate oil and fat determination method for monitoring and controlling the oil content of the fried food.

The low-field nuclear magnetic resonance is a nondestructive and rapid detection technology, can be used for detecting small molecular protons in a complex food system, and is already applied to the determination of the oil content and the water distribution state of plant seeds. At present, related researches on migration change of oil and moisture of food in a frying process are mostly concentrated on fried potato chips, potato chips and the like, and no report is found on the related researches on moisture and oil distribution of vacuum fried pleurotus eryngii, particularly on a rapid detection technology of the vacuum fried pleurotus eryngii.

Disclosure of Invention

Technical problem to be solved

Aiming at the defects of the prior art, the invention provides a vacuum fried pleurotus eryngii strip moisture and grease rapid detection technology based on low-field nuclear magnetic resonance, fresh pleurotus eryngii is used as a raw material, the change rule of moisture, grease, brittleness, hardness and color of pleurotus eryngii strips in the vacuum frying process is researched, the low-field nuclear magnetic resonance technology and the imaging technology thereof are adopted, the relational equation between the T2 relaxation parameter and the moisture, grease, hardness and brittleness is established, and the rapid, accurate and nondestructive moisture and grease detection method is provided for fruit and vegetable vacuum fried fruit and vegetable crisp chips.

(II) technical scheme

In order to achieve the purpose, the invention provides the following technical scheme: a vacuum fried pleurotus eryngii strip moisture and grease rapid detection technology based on low-field nuclear magnetic resonance comprises the following steps:

1) pretreatment of a detected object: selecting pleurotus eryngii without mildew and rot and mechanical damage, rinsing the pleurotus eryngii with clean water for 2-3 times, cutting the pleurotus eryngii into strips with the thickness of 6mm multiplied by 40mm, blanching the cut pleurotus eryngii strips in boiling water at 900 ℃ for 3min, draining water on the surfaces of the pleurotus eryngii strips, adding 40L of soybean oil into vacuum frying equipment, opening a steam heating valve, heating the soybean oil to the temperature of 90 ℃, opening a sealing door of a fryer, putting processed 300g of shiitake slices into an oil frying basket, closing the sealing door and a vacuum valve, opening a vacuum pump, putting the oil frying basket down when vacuumizing is carried out to the vacuum degree of 0.090MPa, then starting vacuum frying, setting the frying time, then carrying out deoiling on the fried pleurotus eryngii strips, carrying out deoiling at the deoiling speed of 300r/min, carrying out deoiling time of 3min, opening the vacuum valve and the sealing door after the deoiling is finished, and taking out products to be tested;

2) collecting data of a test sample: when the measurement temperature range is 31.99-32.01 ℃, collecting samples once every 2min, placing the samples in a nuclear magnetic tube and the center of a magnet coil, firstly obtaining the center frequency of the samples by using an FID sequence, then measuring the transverse relaxation time T2 in the samples by using a CPMG pulse sequence, repeatedly collecting signals of each sample for three times, and averaging the results;

3) establishing a data chart: the sample is placed in the center of the magnet coil for signal acquisition, and a visual information table is obtained by using an SE sequence in nuclear magnetic resonance imaging software. Performing NMR imaging every 2min, and acquiring signal data of transverse relaxation time of pleurotus eryngii under different frying time through a CPMG sequence echo peak point diagram;

4) and (5) rapidly and comparatively detecting the detection object.

Preferably, in the second step, the CPMG pulse sequence parameters are set as: the main frequency SF1 is 23MHz, the offset frequency O1 is 416765.87KHz, the 90 ° pulse time P90 is 10 μ s, the 180 ° pulse time P180 is 20 μ s, the number of sampling points TD is 150000, the number of accumulations is 8, the echo time TE is 300ms, and the number of echoes is 5000.

Preferably, the mri parameters in step three are set as: the main frequency SF1 is 18MHz, the offset frequency O1 is 159.609131kHz, the number of sampling points TD is 256, the sampling frequency SW is 20kHz, the sampling time DW is 50 μ s, the total signal sampling time ACQ is 12.8ms, the receiver dead time DT2 is 1.4ms, the analog gain RG1 is 20dB, the digital gain DRG1 is 3dB, the layer selection direction GsliceY is 1, the phase encoding direction gchasez is 1, the frequency encoding direction GreadX 1, the 90 ° pulse width P1 is 1200 μ s, the 180 ° pulse width P2 is 1200 μ s, the 90 ° pulse width RFA1 is 3%, the 180 ° pulse width RFA2 is 6%, the radio frequency pulse shape RFSH1 is 5sinc256, the number of repeated sampling times NS 4, the number of times of repeated sampling RP1, and the number of times of accumulated cot 2.

Preferably, in order to ensure high accuracy of the data, the obtained peak area and transverse relaxation time are subjected to standardization processing to obtain the peak area and transverse relaxation time corresponding to each unit mass of the sample, and the peak area A₂And transverse relaxation time T₂The normalization process can be expressed as:

in the formula: a. the_tAnd T_tRespectively the peak area and transverse relaxation time/ms after t moment inversion; a. the₂And T₂Respectively the peak area and transverse relaxation time/ms after the standardization treatment at the time t; m₂Is the mass/g of the corresponding pleurotus eryngii strips,

the average initial water content of the pleurotus eryngii is 86.79% by measuring the water content of the pleurotus eryngii by an MB90 type rapid moisture meter, and the water content of the dry pleurotus eryngii is calculated according to the formula (3):

in the formula, M is dry basis water content, g/g, when the pleurotus eryngii is fried to t time; w-moisture content of wet base when vacuum frying pleurotus eryngii to t moment, g/g^[16]. All water contents are expressed in dry basis (%).

Repeating the measurement for 3 times, and taking an average value;

fat content was determined by Soxhlet extraction according to the method specified in GB 5009.6-2016, and all oil contents are expressed in dry basis (%), and 3 experiments were repeated, taking the average of 3.

Preferably, the assay data is processed using SPSS 19.0 software, and a, b, c, d, f, g, and h represent significant differences at levels of P < 0.05. Each experiment was repeated three times and the results are expressed as mean ± SD.

The invention aims to solve another technical problem of providing a vacuum fried pleurotus eryngii strip moisture and grease rapid detection technology based on low-field nuclear magnetic resonance, which comprises the following steps:

1) pretreatment of a detected object: selecting pleurotus eryngii without mildew and rot and mechanical damage, rinsing the pleurotus eryngii with clean water for 2-3 times, cutting the pleurotus eryngii into strips with the thickness of 6mm multiplied by 40mm, blanching the cut pleurotus eryngii strips in boiling water at 900 ℃ for 3min, draining water on the surfaces of the pleurotus eryngii strips, adding 40L of soybean oil into vacuum frying equipment, opening a steam heating valve, heating the soybean oil to the temperature of 90 ℃, opening a sealing door of a fryer, putting processed 300g of shiitake slices into an oil frying basket, closing the sealing door and a vacuum valve, opening a vacuum pump, putting the oil frying basket down when vacuumizing is carried out to the vacuum degree of 0.090MPa, then starting vacuum frying, setting the frying time, then carrying out deoiling on the fried pleurotus eryngii strips, carrying out deoiling at the deoiling speed of 300r/min, carrying out deoiling time of 3min, opening the vacuum valve and the sealing door after the deoiling is finished, and taking out products to be tested;

2) collecting data of a test sample: when the measurement temperature range is 31.99-32.01 ℃, collecting samples once every 2min, placing the samples in a nuclear magnetic tube and the center of a magnet coil, firstly obtaining the center frequency of the samples by using an FID sequence, then measuring the transverse relaxation time T2 in the samples by using a CPMG pulse sequence, repeatedly collecting signals of each sample for three times, and averaging the results;

3) establishing a data chart: the sample is placed in the center of the magnet coil for signal acquisition, and a visual information table is obtained by using an SE sequence in nuclear magnetic resonance imaging software. Performing NMR imaging every 2min, and acquiring signal data of transverse relaxation time of pleurotus eryngii under different frying time through a CPMG sequence echo peak point diagram;

4) and (5) rapidly and comparatively detecting the detection object.

(III) advantageous effects

Compared with the prior art, the invention provides a vacuum fried pleurotus eryngii strip moisture and grease rapid detection technology based on low-field nuclear magnetic resonance, which has the following beneficial effects:

according to the vacuum fried pleurotus eryngii strip moisture and grease rapid detection technology based on low-field nuclear magnetic resonance, a relation equation between the peak area of a T2 relaxation parameter and moisture and grease is established, the obtained regression equation has high fitting degree, and the moisture and grease change rule at any moment in the vacuum frying process of pleurotus eryngii strips can be accurately and rapidly measured through the peak area. And (3) visualizing the nuclear magnetic resonance signal by using MRI, and visually monitoring the distribution condition of water and grease in the vacuum frying process. The low-field nuclear magnetic resonance technology can quickly and accurately measure the moisture content and the grease content of the fruits and vegetables in the vacuum frying process.

Drawings

FIG. 1 is a graph showing the attenuation curve of the Pleurotus eryngii strip of the present invention;

FIG. 2 is a graph of inversion spectra of T2 according to the present invention as a function of fry time;

FIG. 3 is an inversion spectrum of T2 of dried Pleurotus eryngii strips according to the present invention;

FIG. 4 is a graph showing hydrogen proton imaging of Pleurotus eryngii strips of the present invention as a function of drying time.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Referring to fig. 1 to 4, the present invention provides a technical solution: a vacuum fried pleurotus eryngii strip moisture and grease rapid detection technology based on low-field nuclear magnetic resonance comprises the following steps:

1) pretreatment of a detected object: selecting pleurotus eryngii without mildew and rot and mechanical damage, rinsing the pleurotus eryngii with clean water for 2-3 times, cutting the pleurotus eryngii into strips with the thickness of 6mm multiplied by 40mm, blanching the cut pleurotus eryngii strips in boiling water at 900 ℃ for 3min, draining water on the surfaces of the pleurotus eryngii strips, adding 40L of soybean oil into vacuum frying equipment, opening a steam heating valve, heating the soybean oil to the temperature of 90 ℃, opening a sealing door of a fryer, putting processed 300g of shiitake slices into an oil frying basket, closing the sealing door and a vacuum valve, opening a vacuum pump, putting the oil frying basket down when vacuumizing is carried out to the vacuum degree of 0.090MPa, then starting vacuum frying, setting the frying time, then carrying out deoiling on the fried pleurotus eryngii strips, carrying out deoiling at the deoiling speed of 300r/min, carrying out deoiling time of 3min, opening the vacuum valve and the sealing door after the deoiling is finished, and taking out products to be tested;

2) collecting data of a test sample: when the measurement temperature range is 31.99-32.01 ℃, collecting samples once every 2min, placing the samples in a nuclear magnetic tube and placing the magnetic coil center, firstly obtaining the center frequency of the samples by using an FID sequence, then measuring the transverse relaxation time T2 in the samples by using a CPMG pulse sequence, repeatedly collecting signals for each sample for three times, averaging the results, and setting the parameters of the CPMG pulse sequence as: the main frequency SF1 is 23MHz, the offset frequency O1 is 416765.87KHz, the 90 ° pulse time P90 is 10 μ s, the 180 ° pulse time P180 is 20 μ s, the number of sampling points TD is 150000, the number of accumulations is 8, the echo time TE is 300ms, and the number of echoes is 5000;

3) establishing a data chart: the sample is placed in the center of the magnet coil for signal acquisition, and a visual information table is obtained by using an SE sequence in nuclear magnetic resonance imaging software. NMR imaging is carried out every 2min, then signal data of transverse relaxation time of pleurotus eryngii under different frying time are collected through a CPMG sequence echo peak point diagram, and nuclear magnetic resonance imaging parameters are set as follows: the main frequency SF1 is 18MHz, the offset frequency O1 is 159.609131kHz, the number of sampling points TD is 256, the sampling frequency SW is 20kHz, the sampling time DW is 50 μ s, the total signal sampling time ACQ is 12.8ms, the receiver dead time DT2 is 1.4ms, the analog gain RG1 is 20dB, the digital gain DRG1 is 3dB, the layer selection direction GsliceY is 1, the phase encoding direction gchasez is 1, the frequency encoding direction GreadX 1, the 90 ° pulse width P1 is 1200 μ s, the 180 ° pulse width P2 is 1200 μ s, the 90 ° pulse width RFA1 is 3%, the 180 ° pulse width RFA2 is 6%, the radio frequency pulse shape RFSH1 is 5sinc256, the number of repeated sampling times NS 4, the number of times of repeated sampling RP1, and the number of times of accumulated tot 2;

4) and (5) rapidly and comparatively detecting the detection object.

In order to ensure high accuracy of data, the obtained peak area and transverse relaxation time are subjected to standardization treatment to obtain the peak area and transverse relaxation time corresponding to each unit mass of sample, and the peak area A₂And transverse relaxation time T₂The normalization process can be expressed as:

in the formula: a. the_tAnd T_tRespectively the peak area and transverse relaxation time/ms after t moment inversion; a. the₂And T₂Respectively the peak area and transverse relaxation time/ms after the standardization treatment at the time t; m₂Is the mass/g of the corresponding pleurotus eryngii strips,

the average initial water content of the pleurotus eryngii is 86.79% by measuring the water content of the pleurotus eryngii by an MB90 type rapid moisture meter, and the water content of the dry pleurotus eryngii is calculated according to the formula (3):

in the formula, M is dry basis water content, g/g, when the pleurotus eryngii is fried to t time; w is the moisture content of the wet base when the pleurotus eryngii is fried in vacuum to the time t, and g/g. All water contents are expressed in dry basis (%). Repeating the measurement for 3 times, and taking an average value;

the fat content is determined by a Soxhlet extraction method according to the method specified in GB 5009.6-2016, all oil contents are expressed in dry basis (%), 3 times of experiments are repeated, and the average number is taken;

the experimental data was analyzed using SPSS 19.0 software and significant differences at P <0.05 levels were expressed as a, b, c, d, f, g, and h. Each experiment was repeated three times and the results are expressed as mean ± SD;

as can be seen from FIG. 1, the trend of the decay curve of the CPMG sequence is consistent, and as the frying time is prolonged, the transverse relaxation time required for the pleurotus eryngii strips to descend from the highest point of the signal amplitude to be flat is shorter and shorter, and the decay rate is faster and faster, namely when the frying time is 14min, the decay curvature and the decay rate are maximum. However, the attenuation curve of the CPMG sequence can only show the relative change trend of the whole water content, oil content and fluidity of the pleurotus eryngii strip, and the state and distribution of internal water and oil cannot be obtained, so that the CPMG signal is converted into a spectrum signal by utilizing a Fourier formula, and the T2 relaxation spectrogram of the water state and distribution and the oil distribution in the pleurotus eryngii strip can be better reflected.

As can be seen from FIG. 2, the inverted NMR T2 inversion map of Pleurotus eryngii strips with different frying times has 1-3 peaks, the 3 relaxation time peak maps are named as T21 (0.35-1.02 ms), T22 (3.65-18.74 ms) and T23 (21.54-114.98 ms), the amplitude of a T21 signal is increased from 1.22au to 10.06au, the amplitude of a T22 signal is decreased from 312.31au to 3.44au, and the amplitude of a T23 signal is increased from 10.76 to 23.78; the whole T2 inversion spectrum shows the phenomena that all peaks gradually move leftwards, the total area of the peaks is reduced, and the peaks are fused, because the moisture of the pleurotus eryngii strips is gradually reduced along with the extension of the frying time, the moisture with high degree of freedom in the vacuum frying process of the pleurotus eryngii strips is transferred to the moisture with low degree of freedom, wherein the degree of freedom of the free water in the pleurotus eryngii strips is large and is removed at the initial stage of frying, so that the mobility of the free water is poor, the flowability of the free water is not easy to enhance, part of the free water is transferred to semi-combined water, on the other hand, most of the semi-combined water is removed after being transferred to the free water, and the T22 is obviously reduced along with the extension of the drying time; meanwhile, part of the combined water with relatively high fluidity migrates to the half-combined water, so that T23 gradually decreases, and therefore all peaks gradually move leftwards, and the total area of the peaks is reduced;

in order to clearly distinguish proton signals between water and oil in the pleurotus eryngii strips, the pleurotus eryngii strips are dried in an oven at 60 ℃ to constant weight by a direct drying method;

FIG. 3 shows an inversion map of relaxation time T2 of a dried sample, and it can be seen that the inverted NMR T2 spectrum has 1-2 peaks, which are T21' (1.16-12.53ms) and T22' (18.73-533.67ms), respectively, and the peak of T21' may be a characteristic peak of trace residual bound water in the sample; t22 'shows characteristic peaks of grease, the area of the characteristic peaks increases with the time, and in combination with the graph in FIG. 2 and FIG. 3, after frying, the relaxation signal of pleurotus eryngii strips has 3 characteristic peaks, the relaxation time of T23 is similar to that of T22', and the areas of the characteristic peaks are the same, so that the peak generated by T21+ T22 is T water, and the peak generated by T23 is T oil;

in order to predict the water and oil contents of the fried pleurotus eryngii strips by using a low-field nuclear magnetic resonance technology, a relation between T2 characteristics and actual water and oil contents and quality of the fried pleurotus eryngii strips is established, T2 parameters are highly related to the water and oil contents, hardness and brittleness, the correlation between the water content and the A water is the highest in two T2 parameters, R2 is 0.995, the low-field nuclear magnetic resonance technology is a supplement technology for monitoring the water and oil contents of the fried pleurotus eryngii strips in the frying process, and an obtained regression equation has high fitting degree and can accurately predict the water and oil change rule at any moment in the vacuum frying process of the pleurotus eryngii strips;

the equation for the relationship between the T2 relaxation parameter and moisture, grease, hardness and brittleness is as follows:

note that P <0.05 indicates a significant difference between the two parameters.

In fig. 4, the moisture content and distribution of the material can be measured efficiently, accurately and nondestructively by using Magnetic Resonance Imaging (MRI), visual information of an internal structure can be provided visually through the definition and brightness of an image, and the MRI image has clear outline and high brightness, which indicates that the moisture content of the material is high; the image is fuzzy and low in brightness, which indicates that the moisture content of the material is low, the low-field nuclear magnetic resonance imaging analysis technology can macroscopically represent the change condition of moisture and the distribution condition of grease, the nuclear magnetic image can reflect the strength of a grease signal by using the difference of colors, the deeper the color is, the stronger the signal is, the overall grease distribution condition of the fried pleurotus eryngii strips can be visually represented, and as can be seen from fig. 4, the inner side outline of the MRI image of the pleurotus eryngii strips is gradually fuzzy, the brightness is gradually weakened, the volume is contracted, the moisture is less, the inside of the image is close to the background color (blue) along with the extension of the frying time within 0-6min, and the sample reaches the drying end point; after 8min, the signal of the outer edge of the grease is gradually enhanced because the grease is gradually increased, so that the signal is enhanced, and the content of the grease is distributed on an edge shell layer. Therefore, as the frying time increases, moisture is continuously removed, the moisture signal gradually weakens, and the grease signal becomes stronger.

The invention has the beneficial effects that: according to the vacuum fried pleurotus eryngii strip moisture and grease rapid detection technology based on low-field nuclear magnetic resonance, a relation equation between a T2 relaxation parameter peak area and moisture and grease is established, the obtained regression equation has high fitting degree, the moisture and grease change rule at any moment in the vacuum frying process of pleurotus eryngii strips can be accurately and rapidly determined through the peak area, nuclear magnetic resonance signals are visualized through MRI, the distribution conditions of the moisture and the grease in the vacuum frying process can be visually monitored, and the low-field nuclear magnetic resonance technology can be used for rapidly and accurately determining the rapid moisture and grease content in the vacuum frying process of fruits and vegetables.

Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.