Powder non-synchronous hygroscopic moisture migration spatio-temporal modeling method, system and prediction method

Abstract

The application discloses a kind of powder non-synchronous hygroscopicity moisture migration space-time modeling method, system and prediction method, belong to powder moisture migration characterization field, solve the problem that prior art cannot quantitatively powder internal non-synchronous hygroscopicity behavior and moisture activity space-time distribution caused by the difference of stacking height difference.First, utilize dynamic moisture adsorption instrument to combine GAB model and establish powder moisture activity prediction model;Then, the dynamic dry basis moisture content of powder of different stacking height is determined by saturated salt solution method time sequence, and moisture activity is calculated;Finally, introduce stacking height x correction Peleg equation, and construct space-time coupling model I.The method is used to predict the moisture activity of powder at any time and stacking height, and optimize the anti-caking storage process.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of powder moisture migration characterization. More particularly, the present application relates to a powder non-synchronous moisture absorption migration spatiotemporal modeling method, system and prediction method. BACKGROUND

[0002] Powder food (such as instant powder, seasoning powder, nutritional preparation) is prone to moisture absorption during processing and storage, leading to uneven moisture distribution, decreased flowability and local caking, which seriously affects product quality. Traditional research is mostly based on the assumption of synchronous moisture absorption, using dynamic moisture adsorption instruments or saturated salt solution methods to determine the overall average moisture content or the terminal water activity of the powder (such as the equilibrium adsorption isotherm fitted by the GAB model), which can characterize the final moisture absorption capacity of the material, but cannot analyze the dynamic moisture migration rules in different spatial positions (especially in the stacking height direction) of the powder during the moisture absorption process.

[0003] Recent research has found that powder moisture absorption has significant non-synchronous characteristics: when water migrates from the surface to the interior, there is a gradient difference in the moisture absorption rate in different stacking height regions, leading to uneven distribution of water activity in space and time. Existing caking evaluation methods (such as FT4 rheometer) can indirectly reflect the degree of caking, but only provide static end-state data, which cannot quantify the dynamic migration process under the coupling of time-height double variables, nor can it establish a mathematical model that can predict the water activity at any time point and any stacking depth.

[0004] Therefore, the existing technology has the following core defects: first, the spatial dimension is missing, ignoring the effect of stacking height (x) on the moisture migration rate, which cannot characterize the gradient distribution of water activity inside the powder; second, the dynamic process is disconnected, existing technology basically relies on end-point equilibrium data, lacking quantitative description of the time-series water activity evolution rule; third, the model adaptation is insufficient, traditional kinetic equations (such as Peleg model) do not introduce spatial variables, making it difficult to fit the spatiotemporal coupling effect of non-synchronous moisture absorption.

[0005] Therefore, there is an urgent need for a moisture migration modeling method that can simultaneously integrate time and stacking height double variables to dynamically quantify the non-synchronous behavior during powder moisture absorption. SUMMARY

[0006] It is an object of the present application to solve at least the above problems and to provide at least the advantages to be explained later.

[0007] It is another object of the present application to provide a powder non-synchronous moisture absorption migration spatiotemporal modeling method, which realizes the quantitative analysis of the dynamic distribution of water activity at different spatiotemporal positions (any time, any height) inside the powder by establishing a non-synchronous moisture absorption migration model I that integrates time and stacking height double variables, providing a theoretical basis for accurately predicting the moisture migration rule inside the powder and optimizing the powder storage and anti-caking process.

[0008] To achieve these objects and other advantages in accordance with the present application, a method for modeling the temporal and spatial migration of powder unsynchronized hygroscopic moisture is provided, comprising:

[0009] S1, determining the mass m of the sample of the powder to be tested at different relative humidities by a dynamic moisture adsorption instrument w , and calculating the equilibrium dry basis moisture content X of the sample of the powder to be tested w , using the GAB model to nonlinearly fit the moisture adsorption isotherm of the sample of the powder to be tested, and establishing a moisture activity prediction model of the sample of the powder to be tested based on the equilibrium dry basis moisture content;

[0010] S2, preparing the sample of the powder to be tested with different stacking heights, and using the saturated salt solution method to sequentially determine the dry basis moisture content of the sample of the powder to be tested with each stacking height in a constant relative humidity environment, and using the moisture activity prediction model of the sample of the powder to be tested based on the equilibrium dry basis moisture content established in step S1 to sequentially calculate the moisture activity of the sample of the powder to be tested with each stacking height;

[0011] S3, introducing the stacking height x of the powder to correct the Peleg equation and fitting, to construct an unsynchronized hygroscopic migration model I of the sample of the powder to be tested:

[0012] (I);

[0013] Wherein, x is the stacking height of the powder, cm; y is the hygroscopic time, days; z is the average moisture activity of the sample of the powder to be tested at the stacking height, and a, b, c and d are fitting parameters, dimensionless.

[0014] In the above technical solution, through steps S1-S2, the mapping relationship between the equilibrium dry basis moisture content X w and the moisture activity a w is established by the GAB model: a w =f(X w ); during the dynamic hygroscopic process in step S2, the time-series dry basis moisture content X t is calculated, and the time-series moisture activity z · is calculated by the GAB model, and the average value z of the time-series moisture activity z t at the same stacking height is further calculated, which is recorded as the average moisture activity of the sample of the powder to be tested at the stacking height. Peleg equation: ; wherein, G is the hygroscopic rate of the sample, g / g; y is the hygroscopic time, days; a and b are equation parameters, dimensionless; G0 is the initial moisture content of the sample, g / g.

[0015] Peleg equation only contains time variable y, on this basis, the packing height is introduced as a key factor for inhibiting the moisture absorption rate (because the larger the packing height, the slower the powder absorbs moisture), and the time linear term in the denominator of the Peleg equation is extended to the coupling term of time + packing height, that is, by→cx+y (c is the height inhibition coefficient or resistance coefficient, y is the moisture absorption time) The physical meaning of the time + packing height coupling term is: the powder moisture absorption resistance increases with the increase of the packing height and the extension of the moisture absorption time. After the extension of the independent variable, the model is reconstructed and the parameters are reset, the above extended independent variable is substituted into the Peleg equation, and the dependent variable is converted into (moisture activity), that is, the model is converted into , let z0=d (initial moisture activity), k=a (moisture absorption rate coefficient) to obtain the non-synchronous moisture migration model I. The physical meanings of the parameters in model I are as follows: a, the maximum moisture absorption potential, related to the powder void structure; b, the initial moisture absorption resistance, related to the powder hydrophilic ability; c, the height resistance coefficient, related to the space migration difficulty; d, the initial moisture activity.

[0016] As can be seen, the Peleg equation only describes the change of the moisture absorption rate G with the moisture absorption time y, and the parameters a and b are only related to time, completely ignoring the space dimension. In the denominator term, the present application introduces the packing height x as an independent variable, and quantifies the space resistance effect through the denominator coupling term cx+y, rather than simply adding, which is obtained after deeply understanding the mechanism of the nonlinear increase of the powder moisture absorption resistance with the packing height. In the molecular term, the time is changed to time x moisture absorption rate coefficient, which more accurately describes the nonlinear behavior that the powder needs a longer time to reach equilibrium under a certain packing height.

[0017] Preferably, the specific operation of establishing the moisture activity prediction model of the to-be-tested powder sample based on the equilibrium dry basis moisture content in step S1 includes:

[0018] S11, weigh the to-be-tested powder sample and place it in the sample disc and into the dynamic moisture adsorption instrument, set the temperature to 25℃, the N2 flow rate to 200sccm, and the relative humidity RH to increase from 0% to 90% at an increment of 10%, and record the sample mass every minute;

[0019] S12, when the change value of the mass with time dm / dt<0.005mg / min, it is considered that the to-be-tested powder sample reaches equilibrium under the corresponding relative humidity, and the dry basis mass m w at equilibrium is recorded as the equilibrium dry basis moisture content X w of the to-be-tested powder sample under the corresponding relative humidity.

[0020] S13, the moisture adsorption isotherm of the to-be-tested powder sample is nonlinearly fitted by using the GAB model, and the moisture activity prediction model II of the to-be-tested powder sample based on the equilibrium dry basis moisture content X w is established:

[0021] (II);

[0022] wherein, X w is the equilibrium dry basis moisture content, g / g; is the average water activity of the powder sample to be measured, = RH / 100; C and K are fitting parameters, dimensionless; X m is the fitted monolayer moisture content, g / g.

[0023] Preferably, the equilibrium dry basis moisture content X w is calculated by X w = (m w -m0) / m0, wherein m w is the mass of the powder sample to be measured at equilibrium under the corresponding relative humidity, and m0 is the dry matter mass of the powder sample to be measured; wherein the dry matter mass m0 of the powder sample to be measured is calculated by first placing another powder sample to be measured in an oven at 105°C until the mass reaches equilibrium, calculating the initial dry basis moisture content X0 of the powder sample to be measured, and then calculating the dry matter mass m0 of the powder sample to be measured according to the initial mass M0 of the powder sample to be measured in the dynamic moisture sorption instrument, m0 = M0 × X0.

[0024] Preferably, in step S2, the powder sample to be measured is prepared at different stacking heights, and the specific operation for measuring the dry basis moisture content of each stacking height of the powder sample to be measured in the dynamic moisture absorption process in time sequence by the saturated salt solution method includes:

[0025] S21, a series of mass gradient powder samples to be measured are weighed and placed in sample tubes, and the stacking height x of the powder sample to be measured in each sample tube is recorded;

[0026] S22, the sample tubes containing the powder samples to be measured at different stacking heights are placed in a drying dish containing a saturated salt solution under a constant relative humidity environment for moisture absorption, the sample tubes are weighed once every 24 hours, and the dry basis moisture content of each stacking height of the powder sample to be measured in the dynamic moisture absorption process is calculated in time sequence according to the mass change before and after moisture absorption.

[0027] Preferably, the gradient range of the stacking height x of the powder sample to be measured in step S21 is 0.01-5 cm, and the adjacent gradient height difference is ≤0.5 cm.

[0028] Preferably, the constant relative humidity in S22 is 10-90%.

[0029] Preferably, the fitting accuracy of the non-synchronous moisture absorption migration model I of the powder sample in step S3 is verified by statistical parameters, and satisfies: the determination coefficient R 2≥ 0.95, root mean square error RMSE ≤ 0.02, chi-square test value χ 2 ≤ 0.005. The Peleg model with compatibility height correction is screened from a large number of mathematical models, and is verified by statistics, which cannot be obtained by a limited number of experiments.

[0030] Preferably, the powder sample to be tested includes natural powder and artificial simulated powder matrix, which includes monosaccharide penetration matrix, disaccharide penetration matrix and trisaccharide penetration matrix.

[0031] The application further claims a method for predicting the internal moisture spatio-temporal distribution in the non-synchronous moisture absorption process of powder, comprising:

[0032] Step one, obtaining the non-synchronous moisture absorption migration model I of the powder to be predicted and fitting the parameter values a, b, c and d according to the non-synchronous moisture absorption spatio-temporal modeling method of the powder;

[0033] Step two, inputting any two of the target stacking height, target moisture absorption time and target average moisture activity of the powder to be predicted, and predicting the result of the remaining one through the non-synchronous moisture absorption migration model I of the powder to be predicted.

[0034] The application further claims a spatio-temporal prediction system for moisture migration in the non-synchronous moisture absorption process of powder, comprising:

[0035] A dynamic moisture adsorption unit is configured to measure the mass of the powder sample to be tested at different relative humidities through a dynamic moisture adsorption instrument, and to calculate the equilibrium dry basis moisture content X w of the powder sample to be tested.

[0036] A dynamic moisture absorption unit is provided with multiple groups of saturated salt solution drying dishes and sample tubes, and is configured to realize the preparation of powder with different stacking heights and to perform dynamic moisture absorption experiments.

[0037] A data processing unit is embedded with:

[0038] A GAB model fitting module is configured to nonlinearly fit the GAB model and to construct a moisture activity prediction model of the powder based on the equilibrium dry basis moisture content.

[0039] A moisture activity prediction module is configured to call the moisture activity prediction model II of the powder based on the equilibrium dry basis moisture content, and to calculate the moisture activity of the powder sample to be tested at each stacking height in sequence.

[0040] A non-synchronous migration model construction module is configured to execute step S3, and simultaneously output the parameters in the non-synchronous moisture absorption migration model I of the powder and the non-synchronous moisture absorption migration model I of the powder.

[0041] The present invention has at least the following beneficial effects:

[0042] Firstly, the spatiotemporal modeling method for asynchronous moisture absorption and migration of powder provided by this invention obtains an asynchronous moisture absorption and migration model I with time and stacking height as dual variables by introducing the stacking height (x) to modify the Peleg equation. For the first time, it realizes the dynamic migration modeling of water activity (z) inside the powder under the dual-variable coupling of time (y) and space (x), breaking through the limitation of traditional models that only rely on time variables, and accurately quantifying the gradient distribution law of asynchronous moisture absorption.

[0043] Secondly, the spatiotemporal modeling method for non-synchronous moisture absorption and water migration of powder provided by this invention is based on a dynamic moisture adsorbent + GAB model (Model II) to establish an equilibrium water activity prediction method. Combined with the accurate calculation of dry matter mass (m0=M0×X0), it provides a high-precision water activity time series calculation basis for the dynamic moisture absorption process and solves the problem that the endpoint data cannot reflect the migration process.

[0044] Thirdly, the spatiotemporal modeling method for asynchronous moisture absorption and migration of powder provided by this invention obtains high-resolution spatial moisture absorption data through gradient stacking height design and time-series weighing of saturated salt solution, which significantly improves the model's ability to characterize the rate of moisture migration from the surface to the deep layers of powder.

[0045] Fourth, the method for predicting the spatiotemporal distribution of internal moisture during asynchronous moisture absorption of powder provided by this invention utilizes the fitted asynchronous migration model I. By inputting any two of the target stacking height, time, and water activity, the remaining parameter results can be predicted, providing a real-time dynamic control basis for optimizing powder storage processes.

[0046] Fifth, the spatiotemporal prediction system for moisture migration during asynchronous moisture absorption of powder provided by this invention integrates a powder moisture adsorption unit, multiple sets of moisture absorption experimental units, and an embedded data processing module. It automatically completes GAB model fitting, water activity calculation, and migration model construction, realizing the integration of experiment, modeling, and prediction, and significantly improving the efficiency and reliability of moisture migration law analysis during asynchronous moisture absorption of powder.

[0047] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Attached Figure Description

[0048] Figure 1 This is a schematic diagram of the moisture absorption device for powder samples of different heights in an embodiment of the present invention;

[0049] Figure 2 This is a schematic diagram illustrating the asynchronous hygroscopic migration of powder samples at different heights in an embodiment of the present invention.

[0050] Figure 3The non-synchronous moisture migration fitting model of jujube powder in Example 1 of the present application;

[0051] Figure 4 The non-synchronous moisture migration fitting model of jujube powder in Example 2 of the present application simulates a unary system (JSS-F)

[0052] Figure 5 The non-synchronous moisture migration fitting model of jujube powder in Example 3 of the present application simulates a binary system (JSS-F1 / G2)

[0053] Figure 6 The non-synchronous moisture migration fitting model of jujube powder in Example 4 of the present application simulates a ternary system (JSS-F1 / G1 / S1). DETAILED DESCRIPTION

[0054] The present application will be further described in detail below with reference to the accompanying drawings, so that those skilled in the art can implement the present application according to the description.

[0055] It should be understood that the terms such as "have", "contain" and "include" used herein do not exclude the presence or addition of one or more other elements or combinations thereof.

[0056] Example 1—Time and space modeling method of moisture migration of jujube powder (JP) during non-synchronous moisture absorption process at 75% relative humidity

[0057] (1) Weigh the JP sample (30-35 mg) and place it in a sample plate, then put it into a dynamic water adsorption instrument, set the temperature to 25°C, the N2 flow rate to 200 sccm and the RH to 0%, and dry the sample to a constant weight. Increase the RH from 0% to 90% in increments of 10%, and when the change in mass with time dm / dt (m: sample mass; t: time) is less than 0.005 mg / min, it is considered to have reached equilibrium, and the sample mass is recorded every minute. Calculate the equilibrium moisture content of the sample based on the corresponding sample equilibrium mass at each relative humidity, and plot the water adsorption isotherm with the sample and the corresponding equilibrium dry basis moisture content as the horizontal and vertical coordinates, respectively, and use the GAB model for nonlinear fitting to establish a water activity prediction model II for the test powder sample based on the equilibrium dry basis moisture content X w

[0058] ;

[0059] Wherein, X w is the equilibrium dry basis moisture content (g / g); is the average water activity.

[0060] (2) As Figure 1 ​As shown, a series of jujube powder (JP) with mass gradients of 1.00 g, 2.00 g, 3.00 g, and 4.00 g were weighed and placed in sample tubes, with corresponding powder accumulation heights of 0.25 cm, 0.5 cm, 0.75 cm, and 1.00 cm. The moisture content of JP was 5.96%. The sample tubes containing the JP were placed in a desiccator containing saturated NaCl solution (75% relative humidity) for dynamic moisture absorption for 40 days. Every 24 hours, the sample tubes were removed and weighed on an electronic balance. The change in equilibrium dry basis moisture content of the JP during the dynamic moisture absorption process was obtained by calculating the mass change before and after moisture absorption.

[0061] The coefficient of determination R of Model II 2 =0.9968, indicating that JP's There is a good correlation between the equilibrium dry basis moisture content and the moisture content of JP at different heights during the moisture absorption process. Therefore, the corresponding moisture content can be calculated from the equilibrium dry basis moisture content of JP at different heights during the moisture absorption process. value.

[0062] (3) Construction of asynchronous hygroscopic migration model: water activity of JP sample at different heights a w The value is the average water activity value corresponding to that segment of powder ( The modified Peleg equation was used to calculate the powder packing height (x), moisture absorption time (y), and a. w (z) A nonlinear surface model is fitted to obtain the nonlinear surface fitting equation, which is the asynchronous hygroscopic migration model I of the powder sample to be tested:

[0063] ;

[0064] Depend on Figure 3 It can be seen that the coefficient of determination R of the nonlinear curve fitting model is 2 =0.9974, indicating that the model can effectively and quantitatively characterize the change in water activity from the surface to the interior during the asynchronous moisture absorption process of JP, and can fully reflect the interaction between powder height and moisture absorption time on water activity. Under the conditions of 4 g mass and 1.00 cm total powder height, combined with the schematic diagram... Figure 2 JP's average water activity value from surface to interior after 10 days of moisture absorption. In order =0.423、 =0.376、 =0.343 and =0.319, indicating that the water activity of JP decreases in a gradient from the surface to the interior during the moisture absorption process.

[0065] Example 2—Spatiotemporal Modeling Method for Moisture Migration in a Solid Matrix Jujube Powder Simulated Univariate System (Fructose Single Permeation) During Asynchronous Moisture Absorption at 75% Relative Humidity:

[0066] (1) Preparation of solid matrix jujube powder simulation univariate system sample: Fully ripe jujubes without mechanical damage or pests were selected, washed, pitted, and cut into 6.0 mm slices. The sugar components in the jujube slices were removed by ultrasonic water extraction at 25°C: ultrasonic power 100 W, ultrasonic time 4 h, material-to-liquid ratio 1:20 (g / mL), water change frequency 30 min / time, to obtain sugar-removed jujube slice solid matrix (Jujube Slice Skeleton, JSS), with a small molecule sugar removal rate of 96.8%. Based on JSS, fructose (F) was permeated into it. The permeation conditions were: fructose solution concentration 100 g / L, material-to-liquid ratio 1:10 (g / mL), permeation temperature 50°C, and permeation time 2 h. Jujube slices that have undergone permeation treatment were heat pump dried at 60°C for 12 h. Finally, they were pulverized (10 s / time, repeated 3 times) and sieved (60 mesh) to obtain a jujube powder simulation system with single fructose permeation (JSS-F), in which the moisture content was 2.41% and the fructose content was 368.72 g / g. The system was sealed and stored at room temperature in a desiccator containing silica gel particles.

[0067] (2) Weigh the JSS-F sample (30-35 mg) and place it in the sample tray. Put the tray into the dynamic moisture adsorption instrument and set the temperature to 25℃. N 2. With a flow rate of 200 sccm and RH of 0%, the sample was dried to constant weight. RH was increased from 0% to 90% in 10% increments. Equilibrium was considered reached when the mass change over time (dm / dt, where m is the sample mass and t is time) was less than 0.005 mg / min. The sample mass was recorded every minute. The dry basis moisture content was calculated based on the equilibrium mass of the sample at each relative humidity. Moisture adsorption isotherms were plotted using the equilibrium dry basis moisture content as the x and y axes, respectively. A GAB model was then used for nonlinear fitting to establish a moisture adsorption isotherm for the powder sample based on the equilibrium dry basis moisture content X. w Water activity prediction model II:

[0068] ;

[0069] Among them, X w To balance the dry basis moisture content (g / g); This represents the average water activity.

[0070] (3) Weigh a series of JSS-F samples with mass gradients of 1.00 g, 2.00 g, 3.00 g, and 4.00 g and place them in sample tubes, with corresponding powder heights of 0.25 cm, 0.5 cm, 0.75 cm, and 1.00 cm. Place the sample tubes containing the JSS-F samples in a desiccator containing saturated NaCl solution (75% relative humidity) for 40 days to absorb moisture. Remove the sample tubes every 24 hours and weigh them on an electronic balance. The change in equilibrium dry basis moisture content of JSS-F during the dynamic moisture absorption process can be obtained by calculating the mass change before and after moisture absorption.

[0071] Coefficient of determination of Model II R 2 =0.9997, indicating that JSS-F There is a good correlation between the equilibrium dry basis moisture content and the moisture content of JSS-F at different heights during the moisture absorption process. . The corresponding calculation can yield the result. value.

[0072] (4) Construction of asynchronous hygroscopic migration model: water activity a of JSS-F sample at different heights w The value is the average water activity value corresponding to that segment of powder ( The modified Peleg equation was used to calculate the powder height (). x ), moisture absorption time ( y ) and a w （z A nonlinear surface model was fitted to obtain the nonlinear surface fitting equation, which is the asynchronous hygroscopic migration model I of the powder sample to be tested:

[0073] ;

[0074] Depend on Figure 4 It can be seen that the coefficient of determination R of the nonlinear curve fitting model is 2 =0.9988, indicating that the model can effectively and quantitatively characterize the change in water activity from the surface to the interior during the asynchronous moisture absorption process of JSS-F, and can fully reflect the effect of powder height and moisture absorption time on a. w The interaction. Under the conditions of 4 g mass and 1.00 cm total powder height, combined with the schematic diagram. Figure 2 The average water activity value of JSS-F after 10 days of moisture absorption, from the surface to the interior. In order =0.685、 =0.602、 =0.541 and =0.493, indicating that during the moisture absorption process, JSS-F absorbs moisture from the surface to the interior. w The change decreases gradually.

[0075] Example 3 - Spatiotemporal modeling of moisture migration in non-synchronous moisture absorption process of solid matrix date powder simulated binary system (fructose:glucose = 1:2 permeation) at 75% relative humidity

[0076] (1) Preparation of solid matrix date powder simulated binary system sample: Select fully ripe, no mechanical damage, no disease and insect pests of gray jujube, after washing and removing the core, cut into 6.0 mm slices. Remove the sugar components in the jujube slices at 25°C by ultrasonic water extraction method: ultrasonic power 100 W, ultrasonic time 4 h, solid-liquid ratio 1:20 (g / mL), water change frequency 30 min / time, to obtain the sugar-removed jujube slice solid matrix (Jujube Slice Skeleton, JSS), and the removal rate of small molecule sugars reaches 96.8%. On the basis of JSS, fructose (Fructose, F) and glucose (Glucose, G) binary permeation is carried out, and the permeation conditions are as follows: the concentration of fructose solution is 33.33 g / L, the concentration of glucose solution is 66.67 g / L; the solid-liquid ratio is 1:10 (g / mL), the permeation temperature is 50°C, and the permeation time is 2 h. The permeated jujube slices are dried by heat pump at 60°C for 12 h, and finally crushed (10 s / time, repeated 3 times) and sieved (60 mesh) to obtain the fructose:glucose = 1:2 permeated date powder simulated binary system (JSS-F1 / G2), wherein the moisture content is 2.27%, the fructose content is 117.67 g / g, and the glucose content is 232.42 g / g; store at room temperature in a dry dish containing silica gel particles.

[0077] (2) Weigh the JSS-F1 / G2 sample (30-35 mg) and place it in the sample dish, then put it into the dynamic moisture adsorption instrument, set the temperature to 25°C, the N2 flow rate to 200 sccm and the RH to 0%, and dry the sample to a constant weight. RH is increased from 0% to 90% by 10% increments, and when the mass change value dm / dt (m: sample mass; t: time) is less than 0.005 mg / min, it is considered to reach equilibrium, and the sample mass is recorded every minute. According to the corresponding sample equilibrium mass at each relative humidity, the equilibrium moisture content on a dry basis is calculated, and the sample mass and the corresponding equilibrium moisture content on a dry basis are taken as the horizontal and vertical coordinates to draw the water adsorption isotherm, and the GAB model is used for nonlinear fitting to establish the water activity prediction model II of the test powder sample based on the equilibrium moisture content on a dry basis:

[0078] ;

[0079] Wherein, X w is the equilibrium moisture content on a dry basis / (g / g); is the average water activity.

[0080] (3) Weigh a series of JSS-F1 / G2 samples with mass gradients of 1.00 g, 2.00 g, 3.00 g, and 4.00 g and place them in sample tubes, with corresponding powder heights of 0.25 cm, 0.5 cm, 0.75 cm, and 1.00 cm. Place the sample tubes containing the JSS-F1 / G2 samples in a desiccator containing saturated NaCl solution (75% relative humidity) for 40 days to absorb moisture. Every 24 hours, remove the sample tubes and weigh them on an electronic balance. By calculating the mass change before and after moisture absorption, the change in equilibrium dry basis moisture content of JSS-F1 / G2 during the dynamic moisture absorption process can be obtained.

[0081] Coefficient of determination of Model II R 2 =0.9996, indicating that JSS-F1 / G2 There is a good correlation between the equilibrium dry basis moisture content and the moisture content of JSS-F1 / G2 at different heights during the moisture absorption process. . The corresponding calculation can yield the result. value.

[0082] (4) Construction of asynchronous hygroscopic migration model: water activity a of JSS-F1 / G2 samples at different heights w The value is the average water activity value corresponding to that segment of powder ( The modified Peleg equation was used to calculate the powder height (). x ), moisture absorption time ( y ) and a w ( z A nonlinear surface model was fitted to obtain the nonlinear surface fitting equation, which is the asynchronous hygroscopic migration model I of the powder sample to be tested:

[0083] ;

[0084] Depend on Figure 5 It can be seen that the coefficient of determination R of the nonlinear curve fitting model is 2 =0.9989, indicating that the model can effectively and quantitatively characterize the change in water activity from the surface to the interior during the asynchronous moisture absorption process of JSS-F1 / G2, and can fully reflect the effect of powder height and moisture absorption time on a. w The interaction. Under the conditions of 4 g mass and 1.00 cm total powder height, combined with the schematic diagram. Figure 2 The average water activity value of JSS-F1 / G2 after 10 days of moisture absorption from the surface to the interior. In order =0.654、 =0.580、 =0.524 and = 0.480, indicating that JSS-F1 / G2 is a hygroscopic process from the surface to the inside a w The change is gradiently decreased.

[0085] Example 4 - The method of space-time modeling of moisture migration in the non-synchronous hygroscopic process of the solid matrix date powder simulating ternary system (fructose: glucose: sucrose = 1:1:1 penetration) at 75% relative humidity

[0086] (1) Preparation of the sample of the solid matrix date powder simulating ternary system: Select the gray dates at the mature stage, without mechanical damage, and without pests and diseases, after cleaning and removing the core, cut into 6.0 mm slices. Remove the sugar components in the date slices at 25°C by ultrasonic water extraction: ultrasonic power 100 W, ultrasonic time 4 h, solid-liquid ratio 1:20 (g / mL), water change frequency 30 min / time, to obtain the date slice skeleton (JSS) with a sugar removal rate of 96.8%. On the basis of JSS, ternary penetration of fructose (F), glucose (G), and sucrose (S) is carried out: the concentration of fructose solution is 33.33 g / L, the concentration of glucose solution is 33.33 g / L, and the concentration of fructose solution is 33.33 g / L; the solid-liquid ratio is 1:10 (g / mL), the penetration temperature is 50°C, and the penetration time is 2 h. The date slices after penetration are dried by heat pump at 60°C for 12 h, and finally crushed (10 s / time, repeated 3 times) and sieved (60 mesh) to obtain the date powder simulating ternary system (JSS-F1 / G1 / S1) with fructose: glucose: sucrose = 1:1:1 penetration, wherein the moisture content is 2.47%, the fructose content is 127.89 g / g, the glucose content is 125.96 g / g, and the sucrose content is 85.71 g / g; store at room temperature in a dry dish containing silica gel particles.

[0087] (2) Weigh the JSS-F1 / G1 / S1 sample (30-35 mg) and place it in the sample dish, and then put it into the dynamic water adsorption instrument, set the temperature to 25°C, N 2The flow rate is 200 sccm and RH is 0%, and the sample is dried to a constant weight. RH is increased from 0% to 90% by 10% increments, and when the change in mass with time dm / dt (m: sample mass; t: time) is less than 0.005 mg / min, it is considered to reach equilibrium, and the sample mass is recorded every minute. According to the corresponding sample equilibrium mass at each relative humidity, the moisture content on a dry basis is calculated, and the sample Moisture adsorption isotherms were plotted using the equilibrium dry basis moisture content as the x and y axes, respectively. A GAB model was then used for nonlinear fitting to establish a moisture adsorption isotherm for the powder sample based on the equilibrium dry basis moisture content X. w Water activity prediction model II:

[0088] ;

[0089] Among them, X w To balance the dry basis moisture content (g / g); This represents the average water activity.

[0090] (3) Weigh a series of JSS-F1 / G1 / S1 samples with mass gradients of 1.00 g, 2.00 g, 3.00 g, and 4.00 g and place them in sample tubes, with corresponding powder heights of 0.25 cm, 0.5 cm, 0.75 cm, and 1.00 cm. Place the sample tubes containing the JSS-F1 / G1 / S1 samples in a desiccator containing saturated NaCl solution (75% relative humidity) for 40 days to absorb moisture. Every 24 hours, remove the sample tubes and weigh them on an electronic balance. By calculating the mass change before and after moisture absorption, the change in equilibrium dry basis moisture content of JSS-F1 / G1 / S1 during the dynamic moisture absorption process can be obtained.

[0091] Coefficient of determination of Model II R 2 =0.9994, indicating that JSS-F1 / G1 / S1 There is a good correlation between the equilibrium dry basis moisture content and the moisture content of JSS-F1 / G1 / S1 at different heights during the moisture absorption process. . The corresponding calculation can yield the result. value.

[0092] (4) Construction of asynchronous hygroscopic migration model: water activity a of JSS-F1 / G1 / S1 samples at different heights w The value is the average water activity value corresponding to that segment of powder ( The modified Peleg equation was used to calculate the powder height (). x ), moisture absorption time ( y ) and a w ( z A nonlinear surface model was fitted to obtain the nonlinear surface fitting equation, which is the asynchronous hygroscopic migration model I of the powder sample to be tested:

[0093] ;

[0094] Depend on Figure 6 It can be seen that the coefficient of determination R of the nonlinear curve fitting model is 2=0.9995, indicating that the model can effectively and quantitatively characterize the change in water activity from the surface to the interior during the asynchronous moisture absorption process of JSS-F1 / G1 / S1, and can fully reflect the effect of powder height and moisture absorption time on a. w The interaction. Under the conditions of 4 g mass and 1.00 cm total powder height, combined with the schematic diagram. Figure 2 The average water activity value of JSS-F1 / G2 after 10 days of moisture absorption from the surface to the interior. In order =0.693、 =0.612、 =0.552 and =0.506, indicating that during the moisture absorption process, JSS-F1 / G1 / S1 is absorbed from the surface to the interior. w The change decreases gradually.

[0095] From the parameters of the moisture migration model I for the asynchronous moisture absorption process of powder matrices in Examples 1-4, it can be seen that the height (spatial) resistance coefficient c in the model is an indicator of the difficulty of deep moisture absorption. The c value is the largest in the moisture migration model for the asynchronous moisture absorption process of natural jujube powder. This is because natural jujube powder contains macromolecules such as pectin and fiber, forming a dense network structure, resulting in high resistance to deep moisture migration. In the artificial infiltration system, sugar molecules replace some fibers, increasing porosity and making the migration channels more unobstructed. Therefore, the c value in the moisture migration model for the asynchronous moisture absorption process of the artificial infiltration system decreases. The maximum hygroscopic potential 'a' in the model represents the hydrophilicity of the powder. Therefore, the a value in the moisture migration model for the asynchronous moisture absorption process of the artificial infiltration system (infiltrating sugar) is larger than the a value in the moisture migration model for the asynchronous moisture absorption process of natural jujube powder. The initial moisture absorption resistance 'b' in the model represents the surface adsorption energy barrier. In the artificial infiltration system, infiltrating sugar covers the matrix surface, forming a homogeneous hydrophilic layer, which reduces the initial adsorption energy barrier of the powder.

[0096] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A method for modeling the temporal and spatial migration of moisture in powder desorption, characterized in that, Comprising: S1, measuring the mass m of the powder sample to be tested under different relative humidities by a dynamic water adsorption instrument w , and calculating the equilibrium dry basis moisture content X of the powder sample to be tested w , using the GAB model to perform nonlinear fitting on the water adsorption isotherm of the powder sample to be tested, and establishing a water activity prediction model of the powder sample to be tested based on the equilibrium dry basis moisture content S2, preparing different pile-up heights of the to-be-tested powder sample, and using the saturated salt solution method to measure the dry basis moisture content of each pile-up height of the to-be-tested powder sample in a dynamic moisture absorption process in time sequence under a constant relative humidity environment, and using the water activity prediction model of the to-be-tested powder sample based on the equilibrium dry basis moisture content established in step S1 to calculate the water activity of each pile-up height of the to-be-tested powder sample in time sequence; S3, introducing the pile-up height x of the powder to correct the Peleg equation and fitting to construct the non-synchronous moisture absorption migration model I of the to-be-tested powder sample: （Ⅰ）； The specific operation of establishing the water activity prediction model of the to-be-tested powder sample based on the equilibrium dry basis moisture content in step S1 comprises: S11, weighing the to-be-tested powder sample and placing it in a sample disc and into a dynamic water adsorption instrument, setting the temperature to 25°C, the N2 flow rate to 200sccm, and the relative humidity RH to increase from 0% to 90% at an increment of 10%, and recording the sample mass once every minute; S12, when the value of the change of mass with time dm / dt <0.005 mg / min, it is considered that the sample of the powder to be measured reaches equilibrium under the corresponding relative humidity, and the dry basis mass m w The equilibrium dry basis moisture content X of the sample of the powder to be measured under the corresponding relative humidity is calculated w ; S13, using the GAB model to non-linearly fit the moisture adsorption isotherm of the powder sample to be tested, and establishing the moisture activity prediction model of the powder sample to be tested based on the equilibrium dry basis moisture content X w of the powder sample to be tested （Ⅱ）； x is the pile-up height of the powder, cm; y is the moisture absorption time, days; z is the average water activity of the to-be-tested powder sample at the pile-up height, and a, b, c and d are fitting parameters, dimensionless; X w To balance the dry basis moisture content, g / g; the average water activity of the powder sample to be tested, = RH / 100; C and K are fitting parameters, dimensionless; X m is the fitted monolayer water content, g / g.

2. The method of claim 1, wherein the powder non-synchronous hygroscopic moisture migration spatiotemporal modeling method is characterized by, Step S12 of balancing the dry basis moisture content X w By X w = (m w -m0) / m0, wherein m w is the mass of the sample to be measured when the sample to be measured is balanced at a corresponding relative humidity, and m0 is the dry matter mass of the sample to be measured; wherein the dry matter mass m0 of the sample to be measured is calculated by the following method: first, another sample to be measured is placed in a 105°C oven until the mass reaches equilibrium, the initial dry basis moisture content X0 of the sample to be measured is calculated, and then the dry matter mass m0 of the sample to be measured is calculated according to the initial mass M0 of the sample to be measured in the dynamic water adsorption instrument, m0 = M0 X0.

3. The method of claim 2, wherein the powder non-synchronous hygroscopic moisture migration spatio-temporal modeling method is characterized by, The specific operation of preparing different pile-up heights of the to-be-tested powder sample in step S2, and using the saturated salt solution method to measure the dry basis moisture content of each pile-up height of the to-be-tested powder sample in a dynamic moisture absorption process in time sequence comprises: S21, weighing a series of mass gradient to-be-tested powder samples into sample tubes and recording the pile-up height x of the to-be-tested powder sample in each sample tube; S22, placing the sample tubes containing different pile-up height to-be-tested powder samples into a drying dish containing a saturated salt solution under a constant relative humidity environment for moisture absorption, weighing the sample tubes once every 24h, and calculating the dry basis moisture content of each pile-up height of the to-be-tested powder sample in a dynamic moisture absorption process in time sequence according to the mass change before and after the moisture absorption.

4. The method of claim 3, wherein the powder non-synchronous hygroscopic moisture migration spatio-temporal modeling method is characterized by, The gradient range of the pile-up height x of the to-be-tested powder sample in step S21 is 0.01-5cm, and the adjacent gradient height difference is ≤0.5cm.

5. The method of claim 4, wherein the powder non-synchronous hygroscopic moisture migration spatio-temporal modeling method is characterized by, The constant relative humidity in S22 is 10-90%.

6. The method of claim 5, wherein the powder non-synchronous hygroscopic moisture migration spatio-temporal modeling method is characterized by, The fitting accuracy of the non-synchronous moisture absorption and migration model I of the measured powder sample in step S3 is verified by statistical parameters, and meets: the determination coefficient R 2 ≥ 0.95, the root mean square error RMSE ≤ 0.02, and the chi-square test value χ 2 ≤ 0.

005.

7. The method of claim 1, wherein the powder non-synchronous hygroscopic moisture migration spatio-temporal modeling method is characterized by, The to-be-tested powder sample includes a natural powder and an artificial simulated powder matrix, and the artificial simulated powder matrix includes a monosaccharide permeation matrix, a disaccharide permeation matrix and a trisaccharide permeation matrix.

8. A method for predicting the spatial and temporal distribution of internal moisture in a powder non-synchronous hygroscopic process, characterized by, Comprising: Step one, obtaining the non-synchronous moisture absorption migration model I of the to-be-predicted powder and fitting the parameter values a, b, c and d according to the powder non-synchronous moisture absorption moisture migration space-time modeling method of any one of claims 1-7; Step two, inputting any two of the target pile-up height, the target moisture absorption time and the average water activity at the target time of the to-be-predicted powder, and predicting the result of the remaining one through the non-synchronous moisture absorption migration model I of the to-be-predicted powder.

9. A system for spatiotemporal prediction of moisture migration in a powder asynchronous moisture uptake process, characterized in that, Comprising: a dynamic water adsorption unit configured to measure the mass of the powder sample to be tested when equilibrated at different relative humidities by a dynamic water adsorption instrument, and to calculate the equilibrium dry basis moisture content X of the powder sample to be tested w ; A dynamic moisture absorption unit provided with multiple groups of saturated salt solution drying dishes and sample tubes, and configured to realize the preparation of different pile-up height powders and perform dynamic moisture absorption experiments; A data processing unit embedded with: A GAB model fitting module configured to nonlinearly fit the GAB model and construct a water activity prediction model of the powder based on the equilibrium dry basis moisture content; The water activity prediction module is configured to call the water activity prediction model II based on the equilibrium dry basis moisture content of the to-be-tested powder sample according to any one of claims 1-7, and calculate the water activity of the to-be-tested powder sample at each stacking height in sequence; The non-synchronous migration model construction module is configured to execute step S3, and synchronously output the parameters in the non-synchronous moisture absorption migration model I of the to-be-tested powder sample according to any one of claims 1-7 and the non-synchronous moisture absorption migration model I of the to-be-tested powder sample.

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