Method for determining nonlinear rheological behavior of crispy oil for lamination system and application of method

Abstract

The invention discloses a method for determining the nonlinear rheological behavior of crispy oil for a lamination system. The method comprises the following steps: (1) preparing a grease sample; (2) performing an LAOS experiment on the grease sample, and collecting original data such as modulus, oscillation strain and stress; and (3) processing data, and evaluating the nonlinear rheological behavior of the grease. The method for testing the nonlinear rheological behavior of the grease opens up a new way for representing the viscoelastic behavior of the grease under the actual operation temperature and calendering condition, and can be used for analyzing the structural characteristics of the crispy oil for a lamination system. Meanwhile, the method has a definite guiding significance on the use of the pastry oil in the automatic production of laminated baked products.

Description

Technical Field

[0001] The present invention belongs to the technical field of oil processing, and particularly relates to a method for measuring the non-linear rheological behavior of flaky oil for lamination systems and its application. Background Art

[0002] Oils and fats are mixtures of solid fats and liquid oils at room temperature and have plasticity. Flaky oil is one of the most important raw materials for lamination baking system products, accounting for 20% - 35% of the dough weight. During the preparation of laminated dough, it needs to be folded and rolled repeatedly, so ductility is the most important characteristic of flaky oil, and the fat crystal network is the structural basis endowing the mechanical properties of oils and fats. It is generally considered that the ideal flaky oil can be summarized as follows: ① The fat crystals are in the β' crystal form; ② The melting point is higher than 40°C; ③ The solid fat content is between 20% - 25% at 20 - 30°C. However, other types of plastic oils and fats may also have similar physical and chemical properties.

[0003] Currently, the research on the fat crystal network pays more attention to the linear viscoelastic region. However, during the rolling process, the flaky oil and the dough will be subjected to a pressure of 30 - 60 Kpa, and the structure will change after experiencing large deformations and high-speed shears. Related methods for detecting the ductility of oils and fats, such as uniaxial compression experiments, can only calculate the apparent elastic modulus and viscosity, and the test error of viscosity is relatively large after reaching the yield pressure; shear creep and stress relaxation will cause the sample products to have non-uniform and uncontrolled flow; the cone penetration experiment lacks a theoretical basis and does not have clearly defined physical properties. Therefore, it is particularly important to develop a new non-linear rheological test method that can adapt to the actual application scenarios. Summary of the Invention

[0004] The purpose of this part is to outline some aspects of the embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this part, as well as in the abstract and the title of the specification of this application, to avoid obscuring the purpose of this part, the abstract of the specification, and the title of the invention, and such simplifications or omissions shall not be used to limit the scope of the present invention.

[0005] In view of the above and / or problems existing in the prior art, the present invention is proposed.

[0006] Therefore, the purpose of the present invention is to overcome the deficiencies in the prior art and provide a method for measuring the non-linear rheological behavior of flaky oil for lamination systems.

[0007] To solve the above technical problems, the present invention provides the following technical solution: A method for measuring the non-linear rheological behavior of flaky oil for lamination systems, characterized in that it includes:

[0008] Preparing an oil sample: Rolling and cutting the oil to be tested, and refrigerating and standing it for later use;

[0009] Perform LAOS experiments on the oil samples and collect the original data of modulus, oscillatory strain, and stress;

[0010] Data processing: Based on the trend of modulus change, determine the linear and non-linear regions of the oil, clarify the critical strain value, and evaluate the non-linear rheological behavior of the oil. When the critical strain is reached, the fat enters the non-linear viscoelastic region.

[0011] As a preferred embodiment of the method of the present invention, wherein: the oil to be tested includes anhydrous butter, palm oil mid-fraction, commercial shortening, and puff pastry oil.

[0012] As a preferred embodiment of the method of the present invention, wherein: roll and cut the oil to be tested, wherein the height of the oil to be tested is 1950 ± 50 μm, and the diameter is 2.0 - 4.0 cm.

[0013] As a preferred embodiment of the method of the present invention, wherein: after cutting, the oil to be tested is wrapped with siliconized paper and refrigerated.

[0014] As a preferred embodiment of the method of the present invention, wherein: the refrigeration temperature is 4 ± 0.5 °C, and the refrigeration time is 24 ± 1 h.

[0015] As a preferred embodiment of the method of the present invention, wherein: the measurement temperature of the LAOS experiment is 20 ± 0.5 °C, the test gap is 1950 ± 50 mm, the oscillation frequency f = 1 Hz, and the strain range is 0.1% - 1000%.

[0016] As a preferred embodiment of the method of the present invention, wherein: collect the original data of modulus, oscillatory strain, and stress, and select the data of 3 - 5 cycles after the strain response waveform reaches stability. Plot the strain-time spectrum with time as the abscissa.

[0017] As a preferred embodiment of the method of the present invention, wherein: clarify the critical strain value, and when the dynamic modulus is 90% of the initial value, it is the critical strain.

[0018] As a preferred embodiment of the method of the present invention, wherein: the changes in oscillatory strain and stress are described by the Lissajous-Bowditch curve, with strain as the abscissa and stress as the ordinate; the shape of the curve reflects the structural characteristics of the fat, showing an ellipse in the linear viscoelastic region and gradually forming other shapes as the strain increases.

[0019] Another object of the present invention is to overcome the deficiencies in the prior art and provide an application of a method for measuring the non-linear rheological behavior of puff pastry oil for laminated systems in food baking.

[0020] Advantages of the present invention:

[0021] The testing method for the non-linear rheological behavior of fats and oils provided by the present invention can open up a new way for characterizing the viscoelastic behavior of fats and oils under actual operating temperatures and calendering conditions, and can be used to analyze the structural characteristics of flaky shortening for laminated systems. At the same time, this method has clear guiding significance for the use of flaky shortening in the automated production of laminated baked products. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings. Among them:

[0023] Figure 1 are the basic characteristics of the plastic fat in the embodiment of the present invention;

[0024] Figure 2 is the oscillatory sweep spectrum of the fat sample in the embodiment of the present invention;

[0025] Figure 3 is the elastic Lissajous-Bowditch curve of the fat sample in the embodiment of the present invention;

[0026] Figure 4 A is the strain hardening coefficient of the fat sample in the embodiment of the present invention; Figure 4 B is the shear thickening coefficient of the fat sample in the embodiment of the present invention; Figure 4 C is the higher harmonic ratio of the fat sample in the embodiment of the present invention; Figure 4 D is the critical strain value of the fat sample in the embodiment of the present invention;

[0027] Figure 5 is the schematic diagram of the laminated structure and external shape of the flaky product prepared from the fat sample in the embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0028] In order to make the above objects, features and advantages of the present invention more obvious and understandable, the following will describe the specific embodiments of the present invention in detail in conjunction with the embodiments of the specification.

[0029] In the following description, many specific details are set forth in order to fully understand the present invention. However, the present invention can also be implemented in other ways different from those described herein. Those skilled in the art can make similar extensions without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0030] Secondly, the so-called "one embodiment" or "embodiment" herein refers to specific features, structures, or characteristics that may be included in at least one implementation manner of the present invention. The appearances of "in one embodiment" in different places in this specification do not all refer to the same embodiment, nor are they separate or alternative embodiments that are mutually exclusive of other embodiments.

[0031] An embodiment of the present invention provides a method for testing the non-linear rheological properties of fats and oils, including ① preparation of a fat and oil sample; ② performing a LAOS experiment on the fat and oil sample and collecting original data such as modulus, oscillatory strain, and stress; ③ data processing to evaluate the non-linear rheological behavior of the fat and oil.

[0032] Further, in step ①, weigh 3.5 g of the fat and oil sample to be tested, place it in a cylindrical mold with a height of 2 mm and a diameter of 40.1 mm, roll it repeatedly, use a wire with a diameter of 0.05 mm to cut the edge of the fat and oil around the inner side of the mold to obtain a fat and oil sample with a height of 2 mm and a diameter of 40 mm (to fit the rheometer fixture size), wrap it with siliconized paper, and let it stand still for 24 h under refrigeration conditions at 4°C to form a stable fat crystal network.

[0033] Further, in step ②, measure through the amplitude sweep mode of a DHR rotational rheometer produced by TA Instruments, USA, to obtain the dynamic modulus. The test conditions are: temperature 20°C, select a 40 mm aluminum plate fixture, and the test gap is 2.0 mm. The oscillation frequency f = 1 Hz, and the strain range is 0.1% - 1000%.

[0034] Further, in step ②, collect the original data of strain and stress, use time as the abscissa, and plot the strain-time and stress-time spectra. And select the data of 3 - 5 cycles after the strain response waveform reaches stability to avoid the influence of transient oscillation.

[0035] Further, in step ③, judge the linear and non-linear regions of the fat and oil according to the trend of modulus change, and clarify the critical strain value. When the dynamic modulus is 90% of the initial value, it is defined as the critical strain. When the critical strain is reached, the fat enters the non-linear viscoelastic region. Plotting the Lissajous-Bowditch curve can be used to describe the change of strain-stress, where the abscissa is strain and the ordinate is stress. The curve shape can reflect the structural characteristics of the fat, usually showing an ellipse in the linear viscoelastic region and gradually forming different shapes as the strain increases.

[0036] Further, in step ③, in the non-linear region, the fat will produce a complex shear stress response, and the strain and stress no longer present as a sine function. The elastic modulus (G') and viscous modulus (G") cannot truly reflect the viscoelastic characteristics of the sample. Perform a multiple harmonic Fourier series expansion on the stress response:

[0037]

[0038] where σ is the shear stress, γ0 is the strain amplitude, and G n ' is the power series of the elastic modulus, and G n ” is the power series of the viscous modulus. ω is the angular frequency (rad / s), t is the time (s), n is the harmonic order. In the linear viscoelastic region, n = 1, and G1' and G1” are approximately constant. In the non-linear region, n > 1, and high-order harmonics are observed in the Fourier rheological spectrum, indicating the existence of non-linear mechanical responses. To quantify the non-linear response of the sample, the sampling ratio of the original strain-stress data is 61 -1 .

[0039] Furthermore, in step ③, performing a Fourier transform on the time-domain signal x(t) can obtain the frequency-domain spectrum X(ω):

[0040]

[0041] X(ω) is a complex function, with a real part X'(ω) and an imaginary part X”(ω). The high-order harmonic I(ω) is defined as:

[0042]

[0043] The degree of non-linear viscoelasticity of the grease sample can be quantified by the high-order harmonic ratio. The third-order relative harmonic intensity is usually used to determine the non-linear rheological behavior of the sample, and there is a correlation between the third-order relative harmonic intensity ratio I3 / I1 and the stress and strain levels.

[0044] Furthermore, in step ③, using the Fourier series to decompose the stress (σ) into the elastic stress (σ') and the viscous stress (σ”)

[0045] σ(t) = σ'(t) + σ”(t)

[0046] σ'(t) = γ0∑ n odd G' n (ω,γ0) sinnωt

[0047] σ”(t) = γ0∑ n odd G” n (ω,γ0) cosnωt

[0048] Furthermore, in step ③, introducing the Chebyshev polynomial can express σ' and σ” as:

[0049] σ'(t) = γ0∑ n odd e n (ω,γ0) T n(x)

[0050]

[0051] T n (x) and T n (y) corresponds to the n - th order Chebyshev polynomial function, and γ0 and γ0 are the maximum strain and shear rate within the cycle respectively, e n (ω, γ0) and v n (ω, γ0) are the elastic Chebyshev coefficient and viscous Chebyshev coefficient of the n - th order respectively

[0052] G M ' = ∑ n odd nG n ' = e1 - 3e3 + 5e5 + …

[0053] G L ' = ∑ n odd nG n '(-1) (n-1) / 2 =e1 + e3 + e5 + …

[0054]

[0055] G M ' and G L ' represent the elastic modulus at minimum strain and large strain respectively, η M ' and η L ' represent the viscous modulus at minimum shear rate and large shear rate respectively. Further, the non - linear behavior of the grease is analyzed through the dimensionless non - linear parameters stress hardening ratio (S) and shear thickening ratio (T):

[0056]

[0057] When S = 0, the sample shows a linear elastic response; when S > 0, the sample shows a strain hardening response; when S < 0, the sample shows a strain softening response. When T = 0, the sample shows a linear viscous response; when T > 0, the sample shows a shear thickening response; when T < 0, the sample shows a shear thinning response.

[0058] Example 1

[0059] This example provides a method for measuring the non - linear rheological behavior of grease. The sample to be measured is anhydrous butter. The anhydrous butter used in this example contains only β' crystals, with a melting point of 33.1 ± 1.2 °C and an initial shear viscosity of 3955.28 Pa·s, and includes the following steps:

[0060] (1) Weigh 3.5 g of anhydrous butter and place it in a cylindrical mold with a height of 2 mm and a diameter of 40.1 mm. Roll it repeatedly and use a wire with a diameter of 0.05 mm to cut the edge of the grease around the inner side of the mold to obtain a grease sample with a height of 2 mm and a diameter of 40 mm (adapting to the rheometer fixture size). Wrap it with siliconized paper and let it stand for 24 h under refrigeration conditions at 4 °C to form a stable fat crystal network.

[0061] (2) Conduct a large-amplitude oscillatory shear test using a DHR rotational rheometer. The specific experimental operations are as follows: measure through the amplitude sweep mode to obtain the dynamic modulus.

[0062] The test conditions are as follows: temperature 20 °C, select a 40 mm aluminum plate fixture, and the test gap is 2.0 mm. The oscillation frequency f = 1 Hz, and the strain range is 0.1% - 1000%. Collect the original data of strain and stress, and select the data of 3 - 5 cycles after the strain response waveform reaches stability.

[0063] (3) Process the collected experimental data.

[0064] Draw a Lissajous - Bowditch curve to describe the change of strain - stress, where the abscissa is strain and the ordinate is stress.

[0065] As shown in the figure, when the anhydrous butter is under a small strain, the graph is an ellipse. When the strain reaches 120%, the curve shape is approximately a quadrilateral. The critical strain of anhydrous butter is 0.016%. As the strain increases, the strain hardening coefficient shows a change of increase - decrease - increase - decrease; the shear thinning coefficient shows a gradually decreasing trend, indicating that the crystal network of anhydrous butter is not stable under large deformations and is prone to damage and reconstruction. The change trend of the third - order relative harmonic intensity ratio I3 / I1 is consistent with that of the strain hardening coefficient.

[0066] Example 2

[0067] This example provides a method for measuring the non - linear rheological behavior of grease. The sample to be measured is the palm oil mid - fraction. The palm oil mid - fraction used in this example only contains β' crystals, with a melting point of 36.8 ± 2.9 °C and an initial shear viscosity of 28043.3 Pa·s. It includes the following steps:

[0068] (1) Weigh 3.5 g of palm oil mid - fraction and place it in a cylindrical mold with a height of 2 mm and a diameter of 40.1 mm. Roll it repeatedly and use a wire with a diameter of 0.05 mm to cut the edge of the grease around the inner side of the mold to obtain a grease sample with a height of 2 mm and a diameter of 40 mm (adapting to the rheometer fixture size). Wrap it with siliconized paper and let it stand for 24 h under refrigeration conditions at 4 °C to form a stable fat crystal network.

[0069] (2) Conduct a large-amplitude oscillatory shear test using a DHR rotational rheometer. The specific experimental operations are as follows: Measure through the amplitude sweep mode to obtain the dynamic modulus.

[0070] The test conditions are as follows: Temperature is 20 °C, select a 40-mm aluminum parallel plate fixture, and the test gap is 2.0 mm. The oscillation frequency f = 1 Hz, and the strain range is 0.1% to 1000%. Collect the original data of strain and stress, and select the data of 3 to 5 cycles after the strain response waveform reaches stability.

[0071] (3) Process the collected experimental data.

[0072] Plot the Lissajous-Bowditch curve to describe the strain-stress variation, where the abscissa is strain and the ordinate is stress.

[0073] As shown in the figure, for the palm oil mid-fraction, when the strain is small, the graph is oval. As the strain increases, the curve area gradually increases. When the strain reaches 120%, the curve transforms into a distorted "bow tie" shape, indicating that the structure is more severely damaged. As the strain increases, the strain hardening coefficient increases significantly and then decreases significantly when the strain reaches 6.72%. The third-order relative harmonic intensity ratio I3 / I1 shows the same trend of change.

[0074] Example 3

[0075] This example provides a method for measuring the non-linear rheological behavior of oils and fats. The sample to be measured is commercial shortening. The commercial shortening used in this example contains β and β' crystals, with a melting point of 47.3 ± 2.6 °C and an initial shear viscosity of 11259.6 Pa·s. It includes the following steps:

[0076] (1) Weigh 3.5 g of commercial shortening and place it in a cylindrical mold with a height of 2 mm and a diameter of 40.1 mm. Roll it repeatedly, and use a 0.05-mm diameter iron wire to cut the edge of the fat around the inner side of the mold to obtain a fat sample with a height of 2 mm and a diameter of 40 mm (to fit the rheometer fixture size). Wrap it with siliconized paper and let it stand at 4 °C for 24 h under refrigeration conditions to form a stable fat crystal network.

[0077] (2) Conduct a large-amplitude oscillatory shear test using a DHR rotational rheometer. The specific experimental operations are as follows: Measure through the amplitude sweep mode to obtain the dynamic modulus.

[0078] The test conditions are as follows: Temperature is 20 °C, select a 40-mm aluminum parallel plate fixture, and the test gap is 2.0 mm. The oscillation frequency f = 1 Hz, and the strain range is 0.1% to 1000%. Collect the original data of strain and stress, and select the data of 3 to 5 cycles after the strain response waveform reaches stability.

[0079] (3) Process the collected experimental data.

[0080] Plot the Lissajous - Bowditch curve to describe the strain - stress variation, where the abscissa is strain and the ordinate is stress.

[0081] As shown in the figure, for commercial shortening at relatively small strains, the graph is elliptical, the curve area increases with the increase of strain, and gradually transforms into a quasi - quadrilateral structure.

[0082] Compared with Example 1 and Example 2, the strain hardening coefficient of commercial shortening shows an increasing trend with the increase of strain, and the absolute value of the strain hardening coefficient is much larger than the shear thinning coefficient, indicating that the non - linear behavior of commercial shortening is mainly strain hardening.

[0083] The basic characteristics of the oil samples used in Examples 1 - 3 are as Figure 1 shown, where Figure 1 A is the polymorphic characteristics of common plastic fats; Figure 1 B is the melting point characteristics of common plastic fats; Figure 1 C is the solid fat content characteristics of common plastic fats; Figure 1 D is the shear behavior of common plastic fats. Traditional methods usually judge the properties of shortening based on these basic characteristics of fats. However, plastic fats are food materials with a specific three - dimensional network structure formed by the self - assembly of triglyceride molecules, having a certain yield stress and viscoelasticity. The crystal network structure is exactly the structural basis for plastic fats to have ideal mechanical properties (plasticity, ductility). In the supercooled state, triglyceride molecules are paired and then assembled into lamellar structures. Nano - sheet crystals stack to form single crystals through intermolecular interactions and then combine into crystal clusters; the crystal clusters continue to grow into larger crystal structures. Therefore, plastic fats have complex structural hierarchies, including the molecular level, polymorphic behavior, nanostructure, microstructure, and macroscopic mechanical properties. Although the melting point, polymorphic behavior, and solid fat content can reflect the structural characteristics of plastic fats, during the actual lamination process, the fats will undergo strong shear and rolling, and the crystal network structure will change. Therefore, traditional methods cannot adapt to the changes in the fat structure during the actual processing.

[0084] Example 4

[0085] This example provides a method for measuring the non - linear rheological behavior of fats. The sample to be measured is puff pastry oil. The puff pastry oil used in this example is a special oil for laminated puff baking products, containing β and β' crystals, with a melting point of 37 ± 1.2 °C and an initial shear viscosity of 15546.4 Pa·s, and includes the following steps:

[0086] (1) Weigh 3.5 g of shortening and place it in a cylindrical mold with a height of 2 mm and a diameter of 40.1 mm. Roll it out repeatedly, and use a wire with a diameter of 0.05 mm to cut the edge of the grease around the inner side of the mold to obtain a grease sample with a height of 2 mm and a diameter of 40 mm (to fit the rheometer fixture size). Wrap it with siliconized paper and let it stand for 24 h under refrigeration at 4 °C to form a stable fat crystal network.

[0087] (2) Conduct a large-amplitude oscillatory shear test using a DHR rotational rheometer. The specific experimental operations are as follows: Measure through the amplitude sweep mode to obtain the dynamic modulus.

[0088] The test conditions are as follows: Temperature is 20 °C, select a 40-mm aluminum plate fixture, and the test gap is 2.0 mm. The oscillation frequency f = 1 Hz, and the strain range is 0.1% - 1000%. Collect the original data of strain and stress, and select the data of 3 - 5 cycles after the strain response waveform reaches stability.

[0089] (3) Process the collected experimental data.

[0090] Draw a Lissajous - Bowditch curve to describe the change of strain - stress, where the abscissa is strain and the ordinate is stress.

[0091] As shown in the figure, the curve area of the shortening increases with the increase of strain and shows an elliptical shape under various deformations. The critical strain of the shortening is 0.062%, which is significantly higher than that of the other three groups of examples. As the strain increases, the strain hardening coefficient of the shortening changes little, while the shear thinning coefficient decreases significantly when the strain reaches 0.69%, showing shear thinning behavior. In addition, compared with other examples, the change of the higher harmonic ratio of the shortening is small, indicating that its crystal network structure is the most stable in the large-amplitude oscillatory shear test.

[0092] Based on the above example analysis, for laminated baking fats, conventional plastic fat evaluation indexes such as melting point, polymorphic form, solid fat content, and shear viscosity cannot effectively reflect the calendering characteristics of the product, while the non-linear behavior of the fat in the large-amplitude oscillatory shear test is an effective means to evaluate the flakiness performance of the product.

[0093] Example 5

[0094] This example provides a preparation method for preparing a flaky pastry product from the grease samples in Examples 1 - 4, including the following steps:

[0095] The raw material ratio is shown in Table 1. Place high-gluten flour, low-gluten flour, salt, granulated sugar, and dry yeast in a dough mixer and stir at low speed for 1 - 2 min to mix evenly. Pour in eggs and ice water and beat at high speed until the dough is formed. Then add butter and stir at low speed for 1 - 2 min to fully mix the butter with the dough, and then beat at high speed for 6 - 8 min to form an ideal gluten network structure. Let the obtained dough stand at room temperature for 15 min, and then roll out the dough into a dough sheet with a length of 28.0 cm, a width of 10.0 cm, and a height of 1.0 cm. Roll out the puff pastry oil to a length of 13.5 cm, a width of 9.5 cm, and a height of 0.6 cm. Wrap the puff pastry oil with the dough sheet, roll it out to 0.8 ± 0.5 cm, fold it and continue to roll and fold, repeat three times, and finally roll out the dough sheet to 0.8 ± 0.5 cm. Cut the dough sheet into nine equal-sized dough pieces.

[0096] Table 1 Raw material ratio of puff pastry products

[0097]

[0098] Subsequently, place the dough pieces in a proofing box at a temperature of 29 ± 0.5 °C and a humidity of 80 ± 1% RH for a proofing time of 100 - 120 min. After the proofing is completed, place the dough pieces in a convection oven at a baking temperature of 190 ± 10 °C and a baking time of 16 - 18 min to obtain a puff pastry with a golden surface.

[0099] The laminated structure and shape of the obtained puff pastry products are as Figure 5 shown. It can be seen that after the rolling process, the structures of anhydrous butter, palm oil middle distillate, and commercial shortening are all significantly damaged. Consistent with the LAOS conclusion, the crystal network structures of the above-mentioned oils are not stable under large deformations, especially the palm oil middle distillate hardly has a shortening effect. In contrast, the puff pastry oil can still maintain a complete structure and form a good laminated structure with the dough sheet, obtaining an ideal shortening effect. In summary, by analyzing the non-linear rheological behavior of oils through LAOS, the use of plastic fats in laminated baking products can be effectively guided.

[0100] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not restrictive. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered within the scope of the present invention.

Claims

1. A method for determining the nonlinear rheological behavior of puff pastry oil for laminating systems, characterized in that: include, Prepare oil samples: roll out and cut the oil to be tested, and refrigerate it for later use; LAOS experiments were performed on oil samples to collect raw data of modulus, oscillation strain, and stress; Data processing, judging the linear and nonlinear regions of oil and fat according to the trend of modulus change, clarifying the critical strain value, and evaluating the nonlinear rheological behavior of oil and fat. When the critical strain is reached, the fat enters the nonlinear viscoelastic region.

2. The method according to claim 1, characterized in that: The oils to be tested include anhydrous butter, palm oil intermediate fraction, commercial shortening, and puff pastry oil.

3. The method according to claim 1, characterized in that: The grease to be tested is rolled, pressed and cut, wherein the height of the grease to be tested is 1950±50 μm and the diameter is 2.0-4.0 cm.

4. The method according to claim 1, characterized in that: The oil to be tested is cut and wrapped with silicone oil paper and then refrigerated.

5. The method according to claim 4, characterized in that: The refrigeration temperature is 4±0.5°C, and the refrigeration time is 24±1h.

6. The method according to claim 1, characterized in that: The measuring temperature of the LAOS experiment is 20±0.5° C., the testing gap is 1950±50 mm, the oscillation frequency f=1 Hz, and the strain range is 0.1% to 1000%.

7. The method according to claim 1, characterized in that: The raw data of modulus, oscillation strain and stress are collected, wherein data of 3 to 5 cycles after the strain response waveform reaches stability are selected, and the strain-time spectrum is plotted with time as the horizontal axis.

8. The method according to claim 1, characterized in that: The critical strain value is determined, wherein the critical strain is when the dynamic modulus is 90% of the initial value.

9. The method according to claim 7, characterized in that: The changes in the oscillating strain and stress are described by the Lissajous-Bowditch curve, where the abscissa is strain and the ordinate is stress; the shape of the curve reflects the structural characteristics of fat, appearing as an ellipse in the linear viscoelastic region and gradually forming other shapes as the strain increases.

10. A method for determining the nonlinear rheological behavior of puff pastry oil for laminating systems and its application in food baking.

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