Protein-polysaccharide-based composite oil gel as well as preparation method and application thereof

Abstract

The invention relates to the technical field of food processing, in particular to protein-polysaccharide-based composite oil gel as well as a preparation method and application thereof. The invention provides a preparation method of protein-polysaccharide-based composite oil gel, which comprises the following steps: mixing protein and water, adding polysaccharide, and adjusting the pH value to obtain a blended emulsion; carrying out Maillard reaction on the blended emulsion to obtain hydrogel; the hydrogel is subjected to freeze drying, and aerogel is obtained; the aerogel is soaked in vegetable oil, and the protein-polysaccharide based composite oil gel is obtained. According to the preparation method, the protein-polysaccharide-based composite oil gel which is safe, healthy, good in stability and uniform in texture and has healthy and nutritional characteristics can be prepared.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of food processing, and particularly relates to a protein-polysaccharide-based composite oil gel and a preparation method and application thereof. BACKGROUND

[0002] Solid fat is crucial in the food processing and nutrition product industry, which can ensure the textural properties, sensory quality and processing stability of food. With the improvement of public health awareness, the health risks caused by excessive intake of hydrogenated oil and saturated fatty acids, such as cardiovascular diseases, obesity and other problems, are attracting more and more attention. Therefore, exploring a fat substitute that can maintain the characteristics of food while reducing health risks has become a problem to be solved in the food industry. SUMMARY

[0003] Therefore, the purpose of the present application is to provide a protein-polysaccharide-based composite oil gel and a preparation method and application thereof. The preparation method can prepare a protein-polysaccharide-based composite oil gel which is safe and healthy, has good stability, uniform texture and both health and nutritional characteristics.

[0004] In order to achieve the above-mentioned purpose of the application, the present application provides the following technical solutions: The present application provides a preparation method of a protein-polysaccharide-based composite oil gel, comprising the following steps: Mixing protein and water, adding polysaccharide, adjusting pH value to obtain a blended emulsion; Carrying out Maillard reaction on the blended emulsion to obtain a hydrogel; Freeze-drying the hydrogel to obtain an aerogel; Soaking the aerogel in vegetable oil to obtain the protein-polysaccharide-based composite oil gel.

[0005] Preferably, the protein includes one or more of whey protein isolate, protein pea protein isolate and soy protein isolate; The molecular weight of the whey protein isolate is 10-20 kDa; The molecular weight of the protein pea protein isolate is 25-55 kDa; The molecular weight of the soy protein isolate is 65-75 kDa.

[0006] Preferably, the polysaccharide is konjac glucomannan.

[0007] Preferably, the mass ratio of the protein and the polysaccharide is 1:1.

[0008] Preferably, the Maillard reaction is carried out under heating conditions; The temperature of the heating is 90℃, and the time is 3h.

[0009] Preferably, the method further comprises cooling after the Maillard reaction is completed. The cooling is performed by ice water cooling.

[0010] Preferably, the method further comprises pre-cooling before the freeze-drying. The pre-cooling is performed at a temperature of -80℃ for 24 hours. The freeze-drying is performed at a temperature of -40℃ for 30 hours.

[0011] Preferably, the plant oil is camellia oil. The soaking is performed at room temperature for 12 hours.

[0012] The application further provides a protein-polysaccharide-based composite oil gel prepared by the method.

[0013] The application further provides the use of the protein-polysaccharide-based composite oil gel in the field of food processing.

[0014] The application provides a method for preparing a protein-polysaccharide-based composite oil gel, comprising the following steps: mixing a protein and water, adding a polysaccharide, adjusting the pH value, and obtaining a blended emulsion; performing a Maillard reaction on the blended emulsion to obtain a hydrogel; performing freeze-drying on the hydrogel to obtain an aerogel; and soaking the aerogel in a plant oil to obtain the protein-polysaccharide-based composite oil gel. In the method, the carbonyl groups in the polysaccharide and the amino groups in the protein will undergo a non-enzymatic browning reaction (Maillard reaction). The Maillard reaction improves the physical properties of the composite, including hardness and chewiness. The protein-polysaccharide composite obtained after the Maillard reaction exhibits good thermal stability and texture properties, and the rheological properties of the composite oil gel formed by the composite are also relatively good. The Maillard reaction product can also promote the cross-linking between proteins, further changing the structure and function of the proteins. The high-temperature treatment in the Maillard reaction helps to stretch the protein molecules, promotes the cross-linking reaction between the proteins and the polysaccharides, and thus enhances the intermolecular interaction force and improves the overall structural strength of the composite oil gel. At the same time, the Maillard reaction also promotes the formation of chemical bonds between the proteins and the sugar substances, resulting in a more compact protein structure and improved resistance to external pressure. In addition, the improvement in chewiness also reflects the improvement in the taste of the composite oil gel, making it more chewy. The optimization of these texture properties expands the possibility of the application of the composite oil gel in the food industry, especially in food formulations that require high hardness and good chewiness. The oil gel treated by the Maillard reaction exhibits its unique advantages. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 A flow chart for preparing the protein-polysaccharide-based composite oil gel according to the present application; Figure 2 SEM images of the aerogels according to Examples 1-3 and Comparative Examples 1-3; Figure 3 Infrared spectra of SPI, PPI, WPI and KGM (a), infrared spectra of the protein-polysaccharide-based composite oil gels according to Examples 1-3 and the oil gels according to Comparative Examples 1-3 (b), and infrared secondary structure distribution of the protein-polysaccharide-based composite oil gels according to Examples 1-3 and the gelled oil according to Comparative Examples 1-3 (c); Figure 4 DSC curves of the aerogels according to Examples 1-3 and Comparative Examples 1-3; Figure 5 LAOS elastic curve graphs of the protein-polysaccharide-based composite oil gels according to Examples 1-3 and the oil gels according to Comparative Examples 1-3; Figure 6 LAOS viscosity curve graphs of the protein-polysaccharide-based composite oil gels according to Examples 1-3 and the oil gels according to Comparative Examples 1-3; Figure 7 Comparison graphs of oil absorption capacity of the aerogels according to Examples 1-3 and Comparative Examples 1-3; Figure 8 Oil retention capacity graphs of the protein-polysaccharide-based composite oil gels according to Examples 1-3 and the oil gels according to Comparative Examples 1-3; Figure 9 Amplitude sweep graphs of the protein-polysaccharide-based composite oil gels according to Examples 1-3 and the oil gels according to Comparative Examples 1-3; Figure 10 Frequency sweep graphs of the protein-polysaccharide-based composite oil gels according to Examples 1-3 and the oil gels according to Comparative Examples 1-3. DETAILED DESCRIPTION

[0016] As shown in the accompanying drawings, Figure 1 the present application provides a preparation method of a protein-polysaccharide-based composite oil gel, comprising the following steps: mixing the protein and water, adding the polysaccharide, adjusting the pH value, and obtaining a blended emulsion; subjecting the blended emulsion to a Maillard reaction to obtain a hydrogel; subjecting the hydrogel to freeze-drying to obtain an aerogel; immersing the aerogel in vegetable oil to obtain the protein-polysaccharide-based composite oil gel.

[0017] In the present application, all the preparation raw materials are commercially available products well known to those skilled in the art, unless otherwise specified.

[0018] In the present application, the protein and water are mixed, then polysaccharide is added, pH value is adjusted, and a blending emulsion is obtained.

[0019] In the present application, the protein preferably comprises one or more of whey protein isolate (WPI), protein pea protein isolate (PPI) and soy protein isolate (SPI), and more preferably comprises whey protein isolate (WPI), protein pea protein isolate (PPI) or soy protein isolate (SPI). When the protein is two or more of the above specific choices, the present application does not have any special limitation on the ratio of the above specific substances, and the mixing can be performed in any ratio. In the present application, the molecular weight of the whey protein isolate is preferably 10-20 kDa; the molecular weight of the protein pea protein isolate is preferably 25-55 kDa; and the molecular weight of the soy protein isolate is preferably 65-75 kDa. In the present application, the above protein is a protein with high nutritional value existing in nature and easy to obtain.

[0020] In the present application, the water is preferably distilled water.

[0021] In the present application, the mass ratio of the protein to water is preferably 1:100.

[0022] In the present application, the mixing is preferably performed under stirring, the stirring speed is preferably 500 rpm, and the time is preferably 3 h. In the present application, the stirring speed is also preferably adjusted according to the viscosity of the mixed solution obtained after mixing.

[0023] In the present application, the polysaccharide is preferably konjac glucomannan.

[0024] In the present application, the mass ratio of the protein to polysaccharide is preferably 1:1.

[0025] The present application does not have any special limitation on the adding method of the polysaccharide, and the protein and polysaccharide can be mixed uniformly by using a method well known to those skilled in the art.

[0026] After the polysaccharide is added, a process of continuing stirring is also preferably included, and the present application does not have any special limitation on the process of continuing stirring, and the process can be performed by using a process well known to those skilled in the art.

[0027] In the present application, the pH value adjusting method preferably adopts the method of adding sodium hydroxide solution, and the concentration of the sodium hydroxide solution is preferably 1 mol / L. The present application does not have any special limitation on the amount of the sodium hydroxide solution, and the amount of the sodium hydroxide solution is the amount known to those skilled in the art so that the pH value of the obtained blended emulsion is 9. After adding the sodium hydroxide solution, the present application also preferably includes the method of stirring to obtain a uniformly dispersed mixed emulsion.

[0028] After obtaining the blended emulsion, the present application carries out Maillard reaction on the blended emulsion to obtain a hydrogel.

[0029] In the present application, the Maillard reaction is preferably carried out under heating conditions, and the heating temperature is preferably 90℃, and the time is preferably 3h. The heating method is preferably water bath heating.

[0030] After the completion of the Maillard reaction, the present application also preferably includes cooling, and the cooling is preferably carried out by ice water cooling.

[0031] After obtaining the hydrogel, the present application carries out freeze-drying on the hydrogel to obtain an aerogel.

[0032] In the present application, the pre-cooling is preferably carried out before the freeze-drying, and the pre-cooling temperature is preferably-80℃, and the time is preferably 24h. In the present application, the freeze-drying temperature is preferably-40℃, and the time is preferably 30h. In the present application, the pre-cooling is preferably carried out in a refrigerator, and the freeze-drying is preferably carried out in a freeze-drying machine.

[0033] After obtaining the aerogel, the present application carries out soaking in vegetable oil to obtain the protein-polysaccharide-based composite oil gel.

[0034] In the present application, the vegetable oil is preferably camellia oil.

[0035] In the present application, the soaking temperature is preferably room temperature, and the time is preferably 12h. The above soaking conditions can achieve an equilibrium state. In the present application, the room temperature can be understood as not being subjected to additional heating or cooling.

[0036] The present application also provides the protein-polysaccharide-based composite oil gel prepared by the preparation method described in the above technical solution, which includes a protein-polysaccharide-based aerogel and vegetable oil dispersed in the protein-polysaccharide-based aerogel.

[0037] In the present application, the protein in the protein-polysaccharide-based aerogel is preferably one or more of whey protein isolate, protein pea protein isolate and soy protein isolate, and more preferably whey protein isolate, protein pea protein isolate or soy protein isolate; when the protein is two or more of the above specific choices, the present application does not have any special limitation on the ratio of the above specific substances, and mixing in any ratio can be carried out.

[0038] In the present application, the polysaccharide in the protein-polysaccharide-based aerogel is preferably konjac glucomannan.

[0039] The present application also provides the use of the protein-polysaccharide-based composite oil gel described in the above technical solutions in the field of food processing. The present application does not have any special limitation on the method of the use, and the method well known to those skilled in the art can be used.

[0040] The technical solutions in the present application will be described clearly and completely in combination with the embodiments in the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0041] The raw materials in the following examples and comparative examples are as follows: Konjac glucomannan (KGM): Hubei Yizhi Konjac Biotechnology Co., Ltd.; Whey protein isolate (WPI): Shanghai Yuan Ye Biotechnology Co., Ltd.; Pea protein isolate (PPI): Shanghai Yuan Ye Biotechnology Co., Ltd.; Soy protein isolate (SPI): Shanghai Maikelin Biotechnology Co., Ltd.; Sodium hydroxide: National Medicine Group Chemical Reagent Co., Ltd.; Camellia oil: commercially available; Example 1 1g of whey protein isolate (molecular weight of 10-20kDa) was dispersed in 100g of distilled water, and after stirring at a speed of 500rpm for 3h, 1g of KGM was added, and the stirring was continued until the mixture was uniform. After adding 1mol / L of sodium hydroxide solution, stirring was carried out, and the mixture was placed in a water bath at 90℃ for 3h, and then rapidly cooled in ice water to obtain a gel; The gel was pre-cooled in a refrigerator at-80℃ for 24h, and then dried in a freeze dryer at-40℃ for 30h to obtain an aerogel; The aerogel was soaked in camellia oil at room temperature for 12h to reach an equilibrium state to obtain a protein-polysaccharide-based composite oil gel (denoted as WK90 or W90).

[0042] Example 2 1 g of pea protein isolate (molecular weight of 25-55 kDa) was dispersed in 100 g of distilled water, stirred at a speed of 500 rpm for 3 h, then 1 g of KGM was added and stirred until mixed evenly, 1 mol / L sodium hydroxide solution was added and stirred, then placed in a water bath at 90°C for 3 h, and then quickly placed in ice water for cooling. A gel was obtained; The gel was pre-cooled in a refrigerator at -80°C for 24 h, then dried in a freeze dryer at -40°C for 30 h to obtain an aerogel; The aerogel was soaked in camellia oil at room temperature for 12 h to reach an equilibrium state to obtain a protein-polysaccharide-based composite oil gel (denoted as PK90 or P90).

[0043] Example 3 1 g of soybean protein isolate (molecular weight of 65-75 kDa) was dispersed in 100 g of distilled water, stirred at a speed of 500 rpm for 3 h, then 1 g of KGM was added and stirred until mixed evenly, 1 mol / L sodium hydroxide solution was added and stirred, then placed in a water bath at 90°C for 3 h, and then quickly placed in ice water for cooling. A gel was obtained; The gel was pre-cooled in a refrigerator at -80°C for 24 h, then dried in a freeze dryer at -40°C for 30 h to obtain an aerogel; The aerogel was soaked in camellia oil at room temperature for 12 h to reach an equilibrium state to obtain a protein-polysaccharide-based composite oil gel (denoted as SK90 or S90).

[0044] Comparative Example 1 Reference Example 1, except that "placed in a water bath at 90°C for 3 h, and then quickly placed in ice water for cooling" was omitted to obtain an oil gel (denoted as WK or W).

[0045] Comparative Example 2 Reference Example 2, except that "placed in a water bath at 90°C for 3 h, and then quickly placed in ice water for cooling" was omitted to obtain an oil gel (denoted as PK or P).

[0046] Comparative Example 3 Reference Example 3, except that "placed in a water bath at 90°C for 3 h, and then quickly placed in ice water for cooling" was omitted to obtain an oil gel (denoted as SK or S).

[0047] Test Example 1. Maillard reaction degree analysis: Test method: The concentration of the gels described in Examples 1~3 and Comparative Examples 1~3 was diluted to 5 mg / mL using distilled water, and the browning index was determined at a wavelength of 420 nm; the glycosylation level of the KGM and protein copolymer was evaluated by the O-Phthalaldehyde (OPA) method; the specific preparation method of the OPA reagent was as follows: 40 mg of OPA was dissolved in 1 mL of methanol and 25 mL of a 0.1 mol / L sodium borate buffer (pH = 9.85), 100 μL of β-mercaptoethanol, and 2.5 mL of a 20% (w(g) / v(mL)) SDS solution were mixed, and deionized water was added to dilute it to a total volume of 50 mL; then, 4 mL of the OPA reagent and 200 μL of the sample solution to be tested were mixed in a test tube, and then reacted in a water bath at 35°C for 2 min, and the absorbance of the reaction solution was measured at 340 nm by an enzyme marker, and a standard curve of 0.5~3 mmol / L lysine was prepared; Result analysis: Under normal temperature and high temperature conditions, the grafting degree (DG) of gels formed by three different molecular weight proteins (whey protein isolate, pea protein isolate, and soy protein isolate) and KGM is shown in Table 1. After the Maillard reaction at high temperature, the grafting degree of WK90 is lower than that of PK90 and SK90. Combined with the browning degree of the Maillard reaction, it can be found that low molecular weight whey protein isolate is more prone to intermolecular crosslinking and polymerization with KGM. However, an excessively prolonged glycosylation reaction time can trigger the degradation of heat amino acids or the breaking of peptide chains, thereby resulting in a decrease in DG. This makes the grafting degree of WK90 lower than that of the other two complexes. By comparing the BI values in the table, it can be concluded that low molecular weight proteins exhibit a higher browning degree, and this difference can be attributed to the inherent amino acid activity of the peptides.

[0048] Table 1 Grafting degree (DG) and browning index (BI) of the gels described in Examples 1~3 and Comparative Examples 1~3

[0049] 2. Aerogel scanning electron microscope (SEM) analysis: Test method: Field emission scanning electron microscopy was used to analyze the surface and cross-sectional morphology of the aerogel. Before imaging, the sample was vacuum sputtered to reduce current influence; Result analysis: Figure 2 SEM images of the aerogels described in Examples 1~3 and Comparative Examples 1~3 are shown in Figure 2It can be seen that at 100 times magnification, we can clearly see the effect of different processing methods on the structure of aerogel. For those composite-based aerogels that have not been treated by Maillard reaction, their structure appears relatively weak, lacking sufficient strength and stability. However, the aerogel treated by Maillard reaction (Example 1) shows significant improvement, with uniform pore structure and good morphology. In contrast, the aerogel described in Example 2 forms a more complex layered structure, with complex boundaries between layers, resulting in a large number of interlayer pores and cracks, and uneven pore distribution, which may affect its performance. As for the aerogel described in Example 3, it presents a poor lamellar structure, with relatively tight pores, but insufficient uniformity and stability of the overall structure. 3. Fourier Transform Infrared Spectroscopy (FTIR) Analysis: Test method: Scan about 1 mg of lyophilized sample mixed with 100 mg of potassium bromide using an infrared spectrum analyzer, scan range 4000~400 cm -1 . Use PeakFit v4.12 software to perform baseline correction, deconvolution, second derivative analysis and Gaussian curve fitting on the amide I band 1600~1700 cm -1 . Calculate the proportion of secondary structure components and quantitatively analyze the amide I band. Test results: Figure 3 The infrared spectra of SPI, PPI, WPI and KGM (a), the infrared spectra of the protein-polysaccharide-based composite oil gels of Examples 1-3 and the oil gels of Comparative Examples 1-3 (b), and the infrared secondary structure distribution of the protein-polysaccharide-based composite oil gels of Examples 1-3 and the gels of Comparative Examples 1-3 (c) are shown in Figure 3 (a) and (b) of the above figures, the characteristic peak of KGM at 1670 cm -1 disappeared significantly, indicating that the protein and polysaccharide complexation was good. Compared with KGM powder and WPI powder, near the wave number 3400 cm -1 , which is usually related to the formation of hydrogen bonds, this may be due to the involvement of N-H stretching vibration on the peptide bond of WPI in the formation of KGM hydrogen bonds, resulting in a shift in the absorption peak. At the same time, near 1646 cm -1 , the peak value reached, at the amide I band 1529 cm -1 , compared with WPI powder, the peak intensity increased significantly, which further confirmed that the interaction between the protein molecules or between the protein and the gel network was strengthened. At the wave number 1024 cm -1 , compared with KGM powder, the peak value increased significantly, which may also be due to the enhanced interaction between KGM and WPI.

[0050] The infrared spectrum of the PK90 of Example 2 and the PK of Comparative Example 2 was analyzed. In the wave number range of 3500~3200 cm -1 , the free stretching vibration peak of N-H bond was observed, which is usually related to the amino group in proteins and polypeptides. Meanwhile, in the wave number range of 3100 cm -1 ~2900 cm -1 , the symmetric and asymmetric stretching vibration peaks of C-H bond were observed, which are irregular in shape in the spectrum. At 1630 cm -1 , a clear absorption peak was observed, which is usually related to the β-sheet structure. The amide II band appears in the wave number range of 1550-1500 cm -1 , which is mainly caused by the in-plane stretching vibration of N-H bond and C-N bond in proteins. Finally, in the wave number range of 1100 cm -1 ~900 cm -1 , the stretching vibration peaks of C-O and C-C bond were observed, which are usually related to the backbone structure of PPI and polysaccharides, nucleic acids and some organic compounds. SK and SK90 have a broad and strong absorption peak around 3200~3600 cm -1 . This broad peak represents the O-H stretching vibration and N-H stretching vibration of hydrogen bonding, indicating that there is hydrogen bonding between polysaccharide and protein molecules. Another weak peak is found near 2950 cm -1 , which is related to C-H stretching and bending vibration. After the Maillard reaction, SK90 has a stronger C=C stretching in the wave number range of 1630~1670 cm -1 . The amide I band (1600~1700 cm -1 ) is an important indicator region for the change of protein secondary structure. As shown in (c) of FIG. Figure 3 , through infrared spectrum analysis, it can be observed that the absorption peak of amide I band in this wavelength range changes, which is closely related to the secondary structure of protein. As shown in (c) of FIG. Figure 3 , the main feature of α-helix structure is the high strength of intramolecular hydrogen bond between carbonyl (-CO) and amino (NH2 - ), and the existence of this hydrogen bond helps to stabilize the helical structure. Compared with the complex aerogel formed at room temperature, the α-helix in the complex aerogel after the Maillard reaction is reduced, indicating that the hydrogen bond inside the material is damaged or interfered to a certain extent, and the structural stability is weakened to a certain extent.

[0051] 4. Thermal performance test (DSC) analysis Test method: The thermal behavior of the aerogels described in Examples 1-3 and Comparative Examples 1-3 was studied using a differential scanning calorimeter. The aerogels were placed in an aluminum pot and N2 atmosphere was blown at a flow rate of 50 mL / min. The heating rate was set to 10 °C / min and the temperature range was 25-250 °C. Test results: Figure 4 The DSC curves of the aerogels described in Examples 1-3 and Comparative Examples 1-3 are obtained from... Figure 4 As can be seen, only a single endothermic peak was observed in the DSC curve, indicating that WPI, PPI, and SPI were uniformly mixed with KGM. The temperature corresponding to this endothermic peak is defined as the melting temperature (T0). m The corresponding enthalpy change is called the denaturation enthalpy (ΔH); the aerogel treated with the Maillard reaction (Example 1) has a melting temperature T that is higher than that of the aerogel not treated with the Maillard reaction (Comparative Example 1). m The temperature was increased from 125.81℃ to 146.94℃, and the To of the aerogel described in Comparative Example 2 was... m The Tg of the aerogel described in Example 2 after the Maillard reaction was 139.41°C. m The T value of the aerogel described in Comparative Example 3 was 167.01℃. m The Tg of the aerogel described in Example 3 after the Maillard reaction was 96.61°C. m The melting temperature was 135.12℃. This indicates that the aerogel formed by the Maillard reaction exhibits a significant improvement in thermal stability. This phenomenon may be attributed to the changes in the spatial conformation and molecular structure of the protein caused by the Maillard reaction, leading to an increase in the endothermic peak temperature. Comparing proteins of different molecular weights, it was found that the melting temperature of the medium-molecular-weight PPI was higher than that of the other two proteins, indicating that PPI has relatively better thermal stability. This may be related to its unique molecular structure and more complex molecular weight distribution, which allows PPI to better maintain structural stability during heating. 5. Large Amplitude Oscillation Shear (LAOS) Analysis: Test method: An Anton Paar rotational rheometer was used to subject the test sample to large-scale oscillation. The probe model was PP50, the parallel plate diameter was 50 mm, and the spacing was set to 1.0 mm. At a frequency of 1 Hz, strain data were collected at 1%, 10%, 100%, 500%, 800%, and 1000%, with the plate temperature set at 25℃ and 90℃ respectively. Test results: Figure 5 The LAOS elasticity curves of the protein-polysaccharide composite oleogels described in Examples 1-3 and the oleogels described in Comparative Examples 1-3 are shown in the figure. Figure 5Analysis of the LAOS Elastic Lissajous curves reveals that in the linear viscoelastic region, the total stress (blue closed curve) is close to the elastic stress (red curve). At a strain of 10%, the composite gel is in the linear viscoelastic region, and the Elastic Lissajous curve is almost a straight line, representing a perfect elastic response to stress and strain. The figure shows that even at 100% strain, the gel formed at 25°C (comparative example) still exhibits high-stiffness linear viscoelastic solid properties. However, in the gel tested at 90°C (example), a significant competition exists between elasticity and viscosity, leading to a significant change in the Lissajous curve. This indicates that increasing temperature makes the gel's internal structure more fragile and susceptible to damage. In the 90°C gel sample (example), as the strain range increases from 1% to 100%, the decomposed elastic stress shows a continuously increasing trend, indicating that under high-temperature conditions, the gel retains more elastic response and exhibits a slight intra-ring strain hardening phenomenon to some extent. Figure 6 The LAOS viscosity curves of the protein-polysaccharide composite oleogels described in Examples 1-3 and the oleogels described in Comparative Examples 1-3 are shown below. Figure 6 As can be seen, the integral area within the graph reflects energy dissipation, thus reflecting the level of viscous response. At lower strain levels, the gels all exhibit a good elliptical shape. As strain increases, the ellipse gradually narrows into an S-shape, and the closed area decreases, indicating elastic decay. This transition from an elastically dominated state to a viscous-dominated state signifies the destruction of the gel structure and an increase in energy dissipation. When the viscosity is at 100% strain, the gel treated at high temperature exhibits a strong competitive relationship. With increasing strain, viscosity becomes dominant, and elasticity decays. The shear stress-strain rate curve gradually changes from an elliptical shape to an approximately S-shape, indicating highly nonlinear viscoelastic behavior with shear thinning at high strain rates. When the strain is greater than 500%, the viscosity curves of all samples exhibit a secondary ring, and the appearance of the secondary ring is due to the complex microstructure of the samples. Notably, SK90 (Example 3) forms almost a single line at strain ranges of 500%–1000%, at which point SK90 exhibits almost purely viscous behavior. 6. Basic Properties Analysis of Olegels: Test methods: 1) Oil absorption capacity of aerogel: First, the aerogel was completely immersed in camellia oil for 24 hours until the adsorption process reached equilibrium, and an oil gel was obtained; the obtained oil gel was suspended in the air for 30 seconds to remove excess surface oil, and then the oil gel was weighed immediately to determine the oil absorption capacity (OAC) of the aerogel: Formula 1; In Formula 1, M is the weight of the oleogel after absorbing camellia oil, in g; M0 is the weight of the aerogel before absorbing camellia oil, in g; 2) Oil-holding capacity of oleogels: The oil gel obtained in step 1) was placed in a 50 mL centrifuge tube and centrifuged at 12000 rpm for 15 min. The tube was then inverted to remove the oil gel. The camellia oil on the surface of the oil gel after centrifugation was removed using absorbent paper. The calculation equation for OHC is shown in Equation 2. Formula 2; In Formula 2, m0 is the weight of the oleogel after absorbing camellia oil, in g; m1 is the weight of the oleogel after centrifugation, in g.

[0052] Test results: Figure 7 This is a comparison chart of the oil absorption capacity of the aerogels described in Examples 1-3 and Comparative Examples 1-3. Figure 7 As can be seen, by comparing the composite aerogels before and after the Maillard reaction, we can clearly observe that the composite aerogel prepared under room temperature conditions exhibits more significant oil absorption performance. Specifically, the oil absorption capacity of the aerogel in Comparative Example 1 reached 40.17 g / g, while the oil absorption capacity of the aerogel in Example 1 after Maillard reaction treatment decreased to 29.28 g / g. Similarly, the oil absorption capacity of the aerogel in Comparative Example 2 was 40.09 g / g, while the oil absorption capacity of the aerogel in Example 2 was 33.26 g / g. Furthermore, the oil absorption capacity of the aerogel in Comparative Example 3 was 39.77 g / g, while the oil absorption capacity of the aerogel in Example 3 was 36.26 g / g. This difference in oil absorption capacity may be attributed to the relatively simple structure of the untreated composite aerogel and its more uniform void distribution. This structural characteristic is closely related to the microstructure of the aerogel, thus showing a significant difference in oil absorption performance. This result also demonstrates that all aerogel templates exhibit good oil adsorption capacity, indicating that no high level of structural collapse occurred in the aerogels. The internal structure of the aerogels formed through the Maillard reaction is relatively compact, with increased steric hindrance, resulting in a decrease in the weight of oil entering the gel interior. A comparative study of the oil absorption capacity of composite aerogels treated at high temperatures showed that the aerogel described in Example 1 exhibited lower oil absorption performance, while the aerogels described in Examples 2 and 3 exhibited higher oil absorption performance. This result indicates that under high-temperature conditions, the chemical reaction between WPI and KGM leads to enhanced intermolecular entanglement, resulting in a compact internal structure. Figure 8 This is a graph showing the oil holding capacity of the protein-polysaccharide composite oleogels described in Examples 1-3 and the oleogels described in Comparative Examples 1-3. Figure 8It can be seen that the oil holding capacity of the protein-polysaccharide composite oleogel in Example 1 is 83.98%, the oil holding capacity of the oleogel in Comparative Example 1 is 70.54%, the oil holding capacity of the protein-polysaccharide composite oleogel in Example 2 is 86.29%, the oil holding capacity of the oleogel in Comparative Example 2 is 79.50%, the oil holding capacity of the protein-polysaccharide composite oleogel in Example 3 is 87.51%, and the oil holding capacity of the oleogel in Comparative Example 3 is 84.43%. By comparing these data, we can clearly see that the oil holding capacity of the composite aerogel after Maillard reaction treatment is significantly improved. In addition, the results also show that small molecule proteins (WPIs) are not as good as large molecule proteins in adsorbing oil.

[0053] 7. Rheological property analysis of olegel: Test method: The rheological properties of the protein-polysaccharide composite oleogels described in Examples 1-3 and the oleogels described in Comparative Examples 1-3 were tested using an Anton Paar rotational rheometer. The probe model was PP50, the diameter of the parallel plates was 50 mm, and the spacing was set to 1.0 mm. 1) Amplitude scanning: When conducting amplitude scanning experiments, a rheometer was used to test the protein-polysaccharide composite oleogels described in Examples 1-3 and the oleogels described in Comparative Examples 1-3 to determine their linear viscoelastic region (LVR). This region was mainly determined by scanning the strain range of 0.01-100% at a fixed frequency of 1Hz. 2) Frequency sweep: The oscillation frequency sweep test is conducted within a defined LVR range, with a frequency range of 0.1% and a strain of 1~100 rad·s. -1 All rheological measurements were performed at 25°C, and the measurement software recorded the elastic modulus (G') and loss modulus (G'') for further analysis. Test results: Figure 9 The amplitude scan images are of the protein-polysaccharide composite oleogels described in Examples 1-3 and the oleogels described in Comparative Examples 1-3, obtained by... Figure 9As observed in the amplitude scanning experiment, the oleogel exhibited linear viscoelastic behavior within a strain range of 0.01% to 0.1%. Within this range, the storage modulus (G') and loss modulus (G'') of the oleogel remained relatively constant, suggesting that its structure did not suffer significant structural damage within this strain range. However, when the strain exceeded 0.1%, the internal structure of the oleogel could not maintain its original stability, its viscoelastic properties changed, and ultimately, the gel structure was completely destroyed. Within the linear viscoelastic region (LVR), the oleogel prepared by the Maillard reaction at 90°C (Example) exhibited higher storage modulus (G') and loss modulus (G'') than the control group without Maillard reaction treatment (Comparative Example), and also had a larger critical strain value. This indicates that the oleogel treated by the Maillard reaction (Example) has a more compact internal network structure, resulting in enhanced mechanical strength and stability. These results reveal that the Maillard reaction can not only improve the thermal stability of oleogels and the compactness of their internal network, but also enhance their ability to resist external stress, thereby delaying the structural failure process caused by excessive strain. Figure 10 The frequency scans are of the protein-polysaccharide composite oleogels described in Examples 1-3 and the oleogels described in Comparative Examples 1-3, obtained by... Figure 10 It can be seen that in the small amplitude frequency scan, the G' of all oleogels is higher than G''. As the frequency increases, the rheological properties of the oleogels remain almost unchanged, indicating that the oleogels have the ability to resist high-frequency oscillations, and high-frequency oscillations do not destroy the semi-solid properties of the oleogels. With the increase of frequency, the storage modulus G' and loss modulus G'' of different oleogel samples both show a slight upward trend, exhibiting a slight frequency dependence. When the same protein undergoes a Maillard reaction with KGM at a high temperature of 90℃, a significant increase in modulus can be observed, indicating that the reacted sample has superior elasticity and viscosity. When comparing oleogels formed by different proteins, the protein-polysaccharide composite oleogel described in Example 1 exhibits the largest modulus, indicating that the internal structure of the protein-polysaccharide composite oleogel described in Example 1 is more compact, and its reaction in the Maillard reaction may be more complete. 8. Texture property analysis: Test method: Data was collected using a texture analyzer with a 25mm diameter probe. The protein-polysaccharide composite oleogels described in Examples 1-3 and the oleogels described in Comparative Examples 1-3 were compressed in TPA test mode. The test speed was 2.0mm / s before the test, 1.0mm / s after the test, and 5.0mm / s after the test. The deformation value was 50%. Test results: Table 2. TPA data of the protein-polysaccharide composite oleogels described in Examples 1-3 and the oleogels described in Comparative Examples 1-3.

[0054] In Table 2, there are significant differences in the values ​​represented by different lowercase letters (P<0.05).

[0055] In summary, 1) low molecular weight whey protein isolate (WK90) exhibits lower grafting degree at high temperatures, indicating that it is more prone to intermolecular cross-linking; however, excessive glycosylation may lead to amino acid degradation or peptide chain breakage. Browning analysis shows that low molecular weight protein has higher activity and is more likely to participate in the Maillard reaction; 2) SEM images showed that the pore structure of the aerogel after the Maillard reaction was more uniform compared to that without the high-temperature reaction. FTIR analysis revealed a strong interaction between the protein and KGM, and secondary structure results showed that the α-helices of the aerogel decreased at high temperatures, and the protein structure expanded, enhancing its composite properties. Furthermore, DSC thermal analysis revealed that the Maillard reaction products exhibited high thermal stability, further confirming the formation of a stable complex between the protein and KGM. DSC analysis indicated that the Maillard reaction improved the thermal stability of the composite aerogel. LAOS testing showed that the gel treated at high temperatures exhibited stronger elastic response and viscous behavior under high strain. 3) Oil gels after the Maillard reaction have stronger oil retention capacity. Rheological tests of oil gels show that oil gels after the Maillard reaction have higher storage modulus and loss modulus. Oil gels after the Maillard reaction (especially WK90) exhibit excellent performance in terms of texture properties such as hardness and chewiness.

[0056] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a protein-polysaccharide-based composite oleogel, characterized in that, Includes the following steps: After mixing protein and water, polysaccharide is added, and the pH value is adjusted to obtain a blended emulsion. The blended emulsion was subjected to a Maillard reaction to obtain a hydrogel; The hydrogel was freeze-dried to obtain an aerogel; The aerogel was soaked in vegetable oil to obtain the protein-polysaccharide composite oleogel.

2. The preparation method according to claim 1, characterized in that, The protein includes one or more of whey protein isolate, pea protein isolate, and soy protein isolate; The molecular weight of the whey protein isolate is 10~20kDa; The molecular weight of the pea protein isolate is 25-55 kDa; The molecular weight of the soy protein isolate is 65-75 kDa.

3. The preparation method according to claim 1, characterized in that, The polysaccharide is konjac glucomannan.

4. The preparation method according to any one of claims 1 to 3, characterized in that, The mass ratio of the protein to the polysaccharide is 1:

1.

5. The preparation method according to claim 1, characterized in that, The Maillard reaction is carried out under heating conditions; The heating temperature is 90℃ and the time is 3 hours.

6. The preparation method according to claim 1, characterized in that, The Maillard reaction is further followed by cooling after completion; The cooling process uses ice water.

7. The preparation method according to claim 1, characterized in that, Pre-cooling is also included before freeze-drying; The precooling temperature is -80℃, and the time is 24 hours; The freeze-drying temperature is -40℃ and the time is 30h.

8. The preparation method according to claim 1, characterized in that, The vegetable oil is camellia oil; The soaking temperature was room temperature, and the soaking time was 12 hours.

9. The protein-polysaccharide-based composite oleogel prepared by the preparation method according to any one of claims 1 to 8, characterized in that, It includes a protein-polysaccharide aerogel and a vegetable oil dispersed in the protein-polysaccharide aerogel.

10. The application of the protein-polysaccharide composite oleogel according to claim 9 in the food processing field.

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