Diglyceride oleogel and preparation method thereof

Abstract

The invention belongs to the technical field of grease preparation, and particularly relates to diglyceride oleogel and a preparation method thereof. According to the diglyceride oleogel, the diglyceride oil is used as liquid oil, monoglyceride, gamma-oryzanol, beta-sitosterol and the like are used as composite gel, the diglyceride oleogel is prepared, and compared with triglyceride oleogel, the diglyceride oleogel is higher in efficacy; moreover, the experimental result of the invention shows that the diglyceride gel oil prepared only by adopting oryzanol and sitosterol as the composite gel has strong binding capacity but high hardness, and is limited in application, especially in a baking and smearing process; the oil gel prepared from the monoglyceride is low in hardness and low in oil binding capacity; therefore, in the invention, the diglyceride oleogel is prepared by compounding the three gels, and the obtained diglyceride oleogel has the characteristics of small hardness and strong oil binding capacity, makes up for the defects of a single gel, and greatly widens the application of diglyceride.

Description

Technical Field

[0001] The invention belongs to the technical field of oil preparation, and particularly relates to a diglyceride oil gel and a preparation method thereof. Background Art

[0002] Oil gel is a thermoplastic high-fat substance formed by liquid oil and gelling agent. As a new oil structuring technology, it can capture a large amount of liquid oil in the three-dimensional supramolecular network formed by the gelling agent, thereby improving the antioxidant capacity of the oil without changing the structure of fatty acids or producing trans fatty acids. It also retains the beneficial ingredients in vegetable oils to a large extent, such as vitamin E and sterols. It also has a flavor comparable to fatty foods in diet. It is regarded as a highly promising fat substitute and has attracted widespread attention in many fields such as food, cosmetics, and medicine.

[0003] However, different types of liquid oils have different chemical structures, and the chemical structure of the liquid oil, such as fatty acid composition, carbon chain length, and degree of unsaturation, can directly affect its interaction with the gelling agent and its gelation ability. In addition, the type of liquid oil can also change the network structure formed by the self-assembly of the gelling agent, thereby affecting the macroscopic properties of the oil gel.

[0004] At present, the research on oil gel is mostly concentrated on triglyceride oil system, and the mechanism and structure-activity relationship of diglyceride oil gel are still unclear. Compared with triglyceride oil, diglyceride oil has higher physiological activity. Based on this, the development of a diglyceride oil gel system can not only inject new members into the family of oil-based functional materials, but also construct a gel network with unique rheological properties through molecular self-assembly mechanism, opening up a new path for effectively broadening the application scope of oil gel materials and the high-value utilization of edible oils. Summary of the Invention

[0005] In order to solve the above technical problems, the present invention provides a diglyceride oil gel and a preparation method thereof.

[0006] The first aspect of the present invention is to provide a diglyceride oil gel, which includes diglyceride oil and a gelling agent accounting for 0.25%-15% by weight of the diglyceride oil, wherein the gelling agent is selected from at least one of ethyl cellulose, hydroxypropyl starch, chitosan, polymethyl methacrylate, polyvinyl alcohol, stearic acid, palmitic acid, γ-oryzanol, β-sitosterol, 12-hydroxystearic acid, lecithin, and monoglyceride.

[0007] Preferably, in the diglyceride oil, diglycerides account for 40%-80% of the mass of the diglyceride oil.

[0008] Preferably, the gelling agent is a complex of γ-oryzanol, β-sitosterol and monoglyceride, and the mass ratio of β-sitosterol:γ-oryzanol:monoglyceride is 1:1-3:30-40.

[0009] The second aspect of the present invention is to provide a method for preparing the diglyceride oleogel, comprising the following steps: (1) Monoglyceride is mixed with γ-oryzanol and β-sitosterol, and stirred continuously at 90-100°C for 20-30 min to obtain a composite gel, wherein the mass ratio of β-sitosterol:γ-oryzanol:monoglyceride is 1:1-3:30-40; (2) Add the composite gel prepared in (1) to the diglyceride oil, with the mass of the composite gel accounting for 0.25%-15% of the mass of the diglyceride oil. Mix and heat until the system forms a homogeneous transparent solution. Cool to room temperature and refrigerate at 4°C for 24 hours to obtain the diglyceride oil gel.

[0010] Preferably, in the above preparation method, the heating time is 20-60 min, and the heating temperature is 70-120°C.

[0011] As further preferred, in (2), the heating time is 20-40 min, and the heating temperature is 70-90°C.

[0012] The beneficial effects of the present invention are: In the present invention, a diglyceride oil gel is prepared using diglyceride oil as the liquid oil and monoglyceride, γ-oryzanol, β-sitosterol, etc. as composite gelling agents. Compared with triglyceride oil gel, the diglyceride oil gel has stronger efficacy. In addition, experimental results of the present invention show that the diglyceride gel prepared using only oryzanol and β-sitosterol as composite gelling agents has strong oil binding ability but high hardness, which limits its application, especially in baking and spreading processes. The oil gel prepared with monoglyceride has low hardness and weak oil binding ability. Therefore, in the present invention, three gelling agents are compounded to prepare diglyceride oil gel. The obtained diglyceride oil gel has the characteristics of low hardness and strong oil binding ability, which makes up for the shortcomings of a single gelling agent and greatly broadens the application of diglyceride. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 The diagram of the state of the diglyceride oil gel obtained by adding different amounts of γ-oryzanol / β-sitosterol composite gel in Example 1 (A) and the effect on the gel-oil binding rate (B); Figure 2 This is a graph showing the effect of heating time (A) and heating temperature (B) on oil binding rate in Example 2; Figure 3 A diagram showing the state of soybean diglyceride oleogel obtained at different addition amounts of the gelling agent monoglyceride in Example 3 (A) and a diagram showing the effect of the addition amount of monoglyceride on the oil binding rate and hardness of the oleogel (B); Figure 4 The state diagram of DAG and TAG oil gel (A) and the oil binding rate and hardness diagram (B) in Example 4; Figure 5 The figure shows the analysis results of the microstructure of DAG and TAG oil gels using a polarized light microscope in Example 4; Figure 6 is the Fourier infrared absorption spectrum of DAG and TAG oil gel in Example 4; Figure 7 This is a graph showing the thermal stability of DAG and TAG oil gels in Example 4; Figure 8 The rate scan (a), strain scan (b), and frequency scan (c) of the DAG and TAG oil gel in Example 4 are shown; Figure 9 This is an analysis chart of the oxidative stability of DAG and TAG oil gels and liquid oils in Example 4. DETAILED DESCRIPTION

[0014] In order to enable those skilled in the art to better understand the present invention, the present invention will be further described in conjunction with specific embodiments.

[0015] Example 1 (1) γ-oryzanol and β-sitosterol were mixed evenly and stirred at 90°C for 30 min to obtain a γ-oryzanol / β-sitosterol composite gel, wherein the mass ratio of γ-oryzanol to β-sitosterol was 6:4; (2) Weigh an appropriate amount of diglyceride oil and add the γ-oryzanol / β-sitosterol composite gel prepared in (1) to the diglyceride oil. The mass percentages of the composite gel in the diglyceride oil are 4%, 6%, 8%, 10%, 12%, and 14%, respectively, to obtain a mixed system in which the mass percentage of diglyceride in the diglyceride oil is 40%; The mixed system was placed in a constant temperature magnetic stirrer and heated until the system formed a homogeneous transparent solution, then naturally cooled to room temperature and transferred to a 5°C environment for 24 h.

[0016] Attachment Figure 1 The effect of the addition amount of γ-oryzanol / β-sitosterol composite gel on the state (A) and binding rate (B) of diacylglycerol oil gel is shown.

[0017] Figure 1It can be seen that when the addition amount of γ-oryzanol / β-sitosterol composite gel is below 8%, diglyceride oil cannot form oil gel and the system still appears as liquid oil. When the addition amount is 8%-14%, diglyceride oil can form oil gel, and the binding rate of gel oil is above 99%.

[0018] Example 2 A γ-oryzanol / β-sitosterol composite gel was obtained according to the method of Example 1, and the addition amount of the γ-oryzanol / β-sitosterol composite gel was set to 8%. On this basis, the key factors (heating time and heating temperature) in the preparation of the diglyceride oil gel were optimized.

[0019] The specific conditions are: heating time (20, 30, 40, 50, 60 min); heating temperature (70, 80, 90, 100, 110, 120°C). Other conditions are the same as in Example 1. Finally, the oil binding rate of the oil gel under each single factor condition is measured to determine the optimal process parameters.

[0020] Attachment Figure 2 Shows the effect of heating time (A) and heating temperature (B) on oil binding rate. Figure 2 It can be seen that during the preparation process of diglyceride oil gel, the binding rate of diglyceride oil gel continues to increase with the extension of heating time and the increase of heating temperature, especially when the heating time changes from 20 min to 30 min and the heating temperature changes from 70℃ to 90℃, the binding rate of diglyceride oil gel increases rapidly.

[0021] In addition, although extending the time and increasing the temperature are both beneficial to improving the diglyceride oil gel binding rate, considering the time cost and the fact that too high a temperature will cause the oil to become rancid, in the present invention, a heating time of 30 min and a heating temperature of 90°C were selected for subsequent experiments.

[0022] Example 3 A certain amount of soybean diglyceride oil (diaglyceride content 40%) was weighed, and monoglyceride was used as a gelling agent. Monoglyceride was added to the soybean diglyceride oil at concentrations of 0.25%, 0.5%, 1.0%, 1.5%, and 2.0% by weight of the soybean diglyceride oil, respectively. Monoglyceride gels of soybean diglyceride oil were prepared according to the same method as in Example 1.

[0023] The state of soybean diglyceride oil gel obtained by adding different amounts of monoglyceride as gelling agent is shown in the attached figure. Figure 3 As shown in (A), the effect of its addition amount on the binding rate and hardness of soybean diglyceride oil gel is shown in the attached figure. Figure 3 As shown in (B).

[0024] Figure 3The results show that after refrigeration for 24 h, soybean diglyceride oil gel can be formed when the addition amount of monoglyceride is less than 1.0%, and the binding rate is above 96%; when the addition amount of monoglyceride is above 1.0%, no gel can be formed or the formed gel quality is poor; when the addition amount of monoglyceride is 1.5%, the binding rate of the soybean diglyceride oil gel formed is 78.71%, and the hardness is only 60.14g. As the addition amount of monoglyceride increases, the hardness of the oil gel gradually decreases.

[0025] Example 4 A composite gel was prepared by mixing 1% monoglyceride with 8% γ-oryzanol / β-sitosterol. Then, a diglyceride (DAG) oil gel was prepared in exactly the same manner as in Example 1, and compared with a triglyceride (TAG) oil gel of the same gel type and addition amount.

[0026] Attachment Figure 4 The state diagram of DAG and TAG oil gel (A) and the oil binding rate and hardness (B) are shown.

[0027] Attachment Figure 4 In the table, OT8: γ-oryzanol / β-sitosterol TAG oil gel; OD8: γ-oryzanol / β-sitosterol DAG oil gel; M-OT8: γ-oryzanol / β-sitosterol / monoglyceride TAG oil gel; M-OD8: γ-oryzanol / β-sitosterol / monoglyceride DAG oil gel, and the same applies to the following.

[0028] Attachment Figure 4 It can be seen that compared with the oleogels without monoglyceride, the addition of monoglyceride has little effect on the oil binding rate, and the oil binding rates of the four oleogels are all above 98%. However, the addition of monoglyceride has a greater effect on the hardness of the oleogels. The hardness of DAG and TAG oleogels is reduced by 239.04 g and 86.20 g, respectively, compared with the oleogels without monoglyceride.

[0029] The reason for the above phenomenon may be that when the addition amount of γ-oryzanol / β-sitosterol composite gelling agent reaches a certain level, a DAG oil gel system with a stable structure and high hardness can be formed. The introduction of monoglyceride significantly changes the gel properties of the system. As a crystalline gelling agent, there is a mechanism conflict between monoglyceride and the self-assembly system. When the addition amount exceeds 1%, the gel becomes unstable. This instability phenomenon is due to the insufficient conversion efficiency of the crystallization system under refrigerated conditions. Only when the addition amount of monoglyceride reaches the critical threshold can a gel network dominated by crystallization be formed within a limited time. Figure 5 The results of polarized light microscopy analysis of the microstructure of DAG and TAG oil gels are shown.

[0030] Figure 5As can be seen, without the addition of monoglyceride, the crystal structure of DAG and TAG oleogels is primarily loose, needle-like. This morphological feature facilitates the construction of the gel network, and its large specific surface area enhances the interfacial interaction between the gelator and the liquid oil phase. The formation mechanism of this crystal structure can be attributed to the lateral growth advantage caused by the van der Waals interaction between the polar ester groups and the long-chain hydrocarbons. Furthermore, the crystal density of the OD8 oleogels is significantly lower than that of the OT8 system. This structural difference directly leads to the OT8 oleogels having a more stable three-dimensional network. The addition of monoglyceride causes the oleogels to transform into clusters. Furthermore, the number of crystals in the DAG oleogels is significantly smaller than that in the TAG oleogels.

[0031] Attachment Figure 6 This is the Fourier infrared absorption spectrum of DAG and TAG oil gel, where M is monoglyceride; O is γ-oryzanol; and B is β-sitosterol.

[0032] Figure 6 As can be seen, β-sitosterol is at 3428 cm -1 The hydroxyl stretching peaks appeared at 3532 cm -1 and 1683 cm -1 、3311 cm -1 and 1729 cm -1 The absorption peaks of hydroxyl and carbonyl groups are generated at 3200~4000 cm -1 The changes within this range are the result of hydrogen bonding between gel molecules. There is no change in the absorption peak within this range, indicating that there is no hydrogen bonding between molecules in the gel, which may be the result of other non-covalent bond interactions such as van der Waals forces.

[0033] Attachment Figure 7 The thermal stability of DAG and TAG oleogels is shown in the figure. All four oleogels exhibit a single melting peak within the experimental temperature range, with the OD8 oleogel having a lower melting temperature than the OT8 oleogel. Without the addition of monoglyceride, the melting temperature of OD8 is 50.90°C. However, with the addition of monoglyceride, the melting peaks of both OD8 and OT8 oleogels shift toward lower temperatures, reaching 47.34°C for M-OD8 and 57.65°C for M-OT8.

[0034] Attachment Figure 8 The rheological properties of DAG and TAG oil gels are shown, where (a) is the viscosity change diagram of different oil gels, (b) is the strain scanning diagram of DAG and TAG oil gels, and (c) is the effect of frequency scanning on the structure of DAG and TAG oil gels.

[0035] The internal network structure of the oil gel constructed by different gelling agents will significantly affect the viscosity of the system. As can be seen in (a), all types of gels exhibit shear behavior, that is, the apparent viscosity continues to decrease with the increase of shear rate, and has a high apparent viscosity at low shear rate. Compared with the oil gel without adding monoglyceride, the apparent viscosity decreases after adding monoglyceride.

[0036] Figure (b) shows that the maximum limit of the linear viscoelastic region ranges from 0.01% to 0.1%. Within this region, G′ is always greater than G′′, indicating that all oleogel samples exhibit solid-dominant behavior. Compared to OT8, the linear viscoelastic region of M-OT8 is shortened, and the associated strain value at the intersection (G′=G′′) is smaller. However, compared to OD8, ​​the addition of monoglyceride to M-OD8 does not affect the expansion of the linear viscoelastic region.

[0037] As can be seen from Figure (c), within the linear viscoelastic region, the G′ and G′′ values ​​of all gels slowly increase with increasing frequency, exhibiting weak oil gel behavior. At the same time, G′ is always greater than G′′, indicating that the three-dimensional network inside the gel is very stable and is less affected by the oscillation frequency.

[0038] The G′ and G′′ of OD8 are smaller than those of OT8, and that of M-OD8 is smaller than that of M-OT8, indicating that the OT8 oil gel system is more stable. After the addition of monoglyceride, the original network structure is destroyed but still has the characteristics of oil gel.

[0039] Attachment Figure 9 Comparison of the oxidative stability of DAG and TAG oil gels and liquid oils.

[0040] As can be seen from the figure, with the extension of storage time, the peroxide values ​​of oil gel and liquid oil increased to varying degrees. There was no significant difference in peroxide value at 5 days of storage. With the extension of storage time, the peroxide value of liquid oil increased more rapidly. The peroxide value of M-OD8 was lower than that of OD8. The same situation also existed for M-OT8 and OT8 at 15 days of storage. After 20 days of storage, the peroxide values ​​of OD8 and OT8 were 11.60 mmol / kg and 7.65 mmol / kg, respectively, which were lower than 14.35 mmol / kg and 13.10 mmol / kg of DAG and TAG liquid oils. Obviously, the oxidative stability of liquid oil prepared into oil gel was significantly improved compared with liquid oil.

Claims

1. A diglyceride oil gel, characterized in that The invention comprises diglyceride oil and a gelling agent accounting for 0.25% to 15% by weight of the diglyceride oil, wherein the gelling agent is selected from at least one of ethyl cellulose, hydroxypropyl starch, chitosan, polymethyl methacrylate, polyvinyl alcohol, stearic acid, palmitic acid, γ-oryzanol, β-sitosterol, 12-hydroxystearic acid, lecithin and monoglyceride.

2. A diglyceride oil gel according to claim 1, characterized in that In the diglyceride oil, diglyceride accounts for 40%-80% of the mass of the diglyceride oil.

3. A diglyceride oil gel according to claim 1, characterized in that The gel is a complex of gamma-oryzanol, beta-sitosterol and monoglyceride, and the mass ratio of beta-sitosterol:gamma-oryzanol:monoglyceride is 1:1-3:30-40.

4. The method for preparing the diglyceride oleogel according to claim 1, characterized in that: The following steps are involved: (1) Monoglyceride is mixed with γ-oryzanol and β-sitosterol, and stirred continuously at 90-100°C for 20-30 min to obtain a composite gel, wherein the mass ratio of β-sitosterol:γ-oryzanol:monoglyceride is 1:1-3:30-40; (2) Add the composite gel prepared in (1) to the diglyceride oil, with the mass of the composite gel accounting for 0.25%-15% of the mass of the diglyceride oil. Mix and heat until the system forms a homogeneous transparent solution. Cool to room temperature and refrigerate at 4°C for 24 hours to obtain the diglyceride oil gel.

5. The preparation method according to claim 4, wherein (2), the heating time is 20-60 min, and the heating temperature is 70-120°C.

6. The preparation method according to claim 5, wherein (2), the heating time is 20-40 min, and the heating temperature is 70-90°C.

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