Preparation method of low-methoxyl pectin-corn starch-based fat substitute

Abstract

The invention belongs to the technical field of fat substitute preparation, and particularly relates to a preparation method of a low-methoxyl pectin-corn starch based fat substitute. According to the invention, low-ester pectin and corn starch are mixed in a solution, a corn oil-based O / W emulsion is prepared through high-speed shearing, and a Ca < 2 + > slow-release system is added to induce formation of emulsion gel. The microstructure and rheological property of an emulsion gel system are regulated and controlled through different oil concentrations, and the relationship between the characteristic change of the emulsion gel system and the oxidation property of the emulsion gel is disclosed. The emulsion gel of the corn starch and the low-ester pectin is a sustainable material, so that a safe, healthy and innovative substitute is provided for food.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of fat substitute preparation, and more particularly to a preparation method of a low-ester pectin-corn starch-based fat substitute. BACKGROUND

[0002] With the enhancement of health diet consciousness, fat substitutes gradually develop into ideal substitutes for dietary fat, which not only can reduce the total fat content in food, but also can simulate the physicochemical properties of fat. The fat substitutes of carbohydrate matrix can reduce the fat content while ensuring the taste, flavor and texture. In actual production and application, the fat substitutes of carbohydrate matrix can form a gel system by water absorption to produce a taste and texture similar to fat.

[0003] However, the fat substitutes currently face some challenges in research and application, mainly in safety, functionality and cost, etc. Some fat substitutes are not easily absorbed by the human body, which may cause side effects on the digestive system and may affect the absorption of fat-soluble vitamins (such as vitamins A, D, E and K). Some fat substitutes have insufficient taste and flavor simulation, and high cost limits the large-scale production and application of fat substitutes. Therefore, how to provide a safe, healthy and innovative fat substitute has become a difficult problem for those skilled in the art to overcome. SUMMARY

[0004] The purpose of the present application is to provide a preparation method of a low-ester pectin-corn starch-based fat substitute to solve the problems existing in the prior art.

[0005] To achieve the above purpose, the present application provides the following solutions.

[0006] One of the technical solutions of the present application is to provide a preparation method of a low-ester pectin-corn starch-based fat substitute, which comprises the following steps:

[0007] Dissolve the low-ester pectin in water to prepare a pectin solution, then heat to 65-75℃, add corn starch, calcium carbonate and soybean oil, stir to form a uniform O / W emulsion, and obtain an emulsion system;

[0008] Pour the emulsion system into a gluconolactone solution, stand for reaction and rinse, and the obtained gel is the low-ester pectin-corn starch-based fat substitute.

[0009] Further, the concentration of the pectin solution is 3.5%-4.5% (w / v), preferably 4% (w / v).

[0010] Further, the concentration of the corn starch in the emulsion system is 5.5%-6.5% (w / v), preferably 6% (w / v).

[0011] Further, the concentration of calcium carbonate in the emulsion system is 0.2%-0.3% (w / v), preferably 0.25% (w / v).

[0012] Further, the concentration of soybean oil in the emulsion system is 0-50% (w / v) and is not 0; preferably 10-20% (w / v); more preferably 20% (w / v).

[0013] Further, the concentration of gluconolactone solution is 4.5%-5.5% (w / v), preferably 5% (w / v).

[0014] Further, the volume ratio of the gluconolactone solution and the emulsion system is 2:1.

[0015] Further, the standing reaction time is 10-14h, preferably 12h.

[0016] Technical solution two of the present application: provide a low ester pectin-corn starch-based fat substitute, the low ester pectin-corn starch-based fat substitute is prepared by the above preparation method.

[0017] Technical solution three of the present application: provide an application of the above low ester pectin-corn starch-based fat substitute in the preparation of low-fat food.

[0018] The emulsion gel (low ester pectin-corn starch based fat substitute) provided by the present application is a new gel system composed of a gel and an emulsion, and plant resources such as proteins, polysaccharides, emulsifiers and vegetable oils are used as raw materials for preparing the emulsion gel. The formation of the emulsion gel is that the emulsion droplets form a gel at a high concentration, or the water phase material forms a continuous gel support network structure, and the emulsion droplets are embedded in the gel matrix to form a stable system. In the latter case, the proteins or polysaccharides usually form a gel network structure in the emulsion system to increase the viscosity of the continuous phase, thereby reducing the movement of the droplets. Polysaccharides can be used as thickening agents and gelling agents, and can also be used as emulsifiers and emulsion stabilizers to form a protective layer at the oil-water interface to stabilize the system. Low ester pectin is a water-soluble dietary fiber extracted from natural plants (such as citrus peel and apple pomace), and the pectin molecule is a long chain composed of hundreds of galacturonic acid units. Some of the carboxyl groups on these units are methyl esterified (methyl groups are connected). When the esterification degree is less than 50%, it is called low ester pectin. The gelation of low ester pectin usually occurs at a relatively low pH (pH < 3.5) and a high sucrose concentration (usually > 65%) as a cosolute. In contrast, low ester pectin is divalent cationic and does not require a cosolute. The gelation of low ester pectin can be explained by the "egg-box" model, which describes the ionic bonds between two dissociated carboxyl sequences from adjacent pectin chains through calcium bridges to form a stable three-dimensional network structure, thereby encapsulating water molecules in it to form a gel. A small amount of starch particles can also stabilize the emulsion to form a mixed gel network system based on starch and low ester pectin.

[0019] The present application discloses the following technical effects:

[0020] The present application mixes low ester pectin and corn starch in a solution, prepares corn oil-based O / W emulsion by high-speed shearing, and adds Ca 2+ The slow-release system induces the formation of emulsion gel. By adjusting the microstructure and rheological properties of the emulsion gel system through different oil concentrations, the relationship between the characteristic changes and the oxidation performance of the emulsion gel is revealed. Since the emulsion gel of corn starch and low ester pectin is a sustainable material, it provides a safe, healthy and innovative alternative for food.

[0021] The present application provides a feasible fat replacement scheme for low-fat food development. BRIEF DESCRIPTION OF DRAWINGS

[0022] The accompanying drawings, which form a part of the present application, are used to provide a further understanding of the present application, and the illustrative embodiments of the present application and their description serve the purpose of explaining the present application. The accompanying drawings do not constitute an inappropriate limitation on the present application. In the drawings:

[0023] Figure 1Physical images of the low ester pectin-corn starch based fat substitute prepared for Example 1, Example 2 and Comparative Example 1.

[0024] Figure 2 Performance of the fat substitute prepared at different oil concentrations, where a is hardness, b is springiness, c is resilience, d is cohesiveness, e is chewiness, and f is cohesiveness.

[0025] Figure 3 Dynamic frequency sweep results for the products prepared for Example 1-2 and Comparative Example 1.

[0026] Figure 4 LAOS results for the products prepared for Example 1-2 and Comparative Example 1.

[0027] Figure 5 Water holding capacity for the products prepared for Example 1-2 and Comparative Example 1.

[0028] Figure 6 CLSM images for the products prepared for Example 1-2 and Comparative Example 1.

[0029] Figure 7 T2 relaxation spectra and relaxation parameters for the products prepared for Example 1-2 and Comparative Example 1.

[0030] Figure 8 Fourier transform infrared spectra for the products prepared for Example 1-2 and Comparative Example 1.

[0031] Figure 9 Zeta potential for the products prepared for Example 1-2 and Comparative Example 1.

[0032] Figure 10 SEM images of the products prepared for Example 1-2 and Comparative Example 1-2 after lyophilization.

[0033] Figure 11 Graphs of the degree of lipid oxidation over time for the products prepared for Example 1-2 and Comparative Example 1.

[0034] Figure 12 Cooking loss for the products prepared for Example 1-2 and Comparative Example 1. DETAILED DESCRIPTION

[0035] Various illustrative embodiments of the present application are now described in detail below. The detailed description is made with reference to the accompanying drawings, wherein like numerals indicate like parts throughout the several views. The detailed description is made with reference to the accompanying drawings, wherein like numerals indicate like parts throughout the several views. The detailed description is made with reference to the accompanying drawings, wherein like numerals indicate like parts throughout the several views.

[0036] It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present application. Additionally, for a range of values of, for example, the upper limit of the range and the lower limit of the range are each implicitly disclosed. Each intermediate value of is also, explicitly, individually and expressly included within the scope of the present application. The intermediate values of are each independent of the other values that might be stated or inferred. The same applies to any intervening, intermediate, or even similar values.

[0037] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. Although preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application. All documents mentioned herein are incorporated by reference to disclose and describe the methods and / or materials in connection with which the documents are cited. In case of conflict, the content of the present specification will control.

[0038] Many modifications and variations of the present application described in the specific embodiments of the application can be made by those skilled in the art without departing from the spirit or scope of the application. Other implementations of the application will be apparent to those skilled in the art from consideration of the specification and practice of the application disclosed herein. The specification and examples given are exemplary only.

[0039] As used herein, the terms "comprises", "comprising", "includes", "including", "has", "having", "contains", "containing", or variations thereof, are intended to be open-ended terms that mean including, but not limited to.

[0040] Unless otherwise specified, all raw materials and reagents involved in the specific embodiments of the present application are commercially available.

[0041] Unless otherwise specified, room temperature and normal temperature in the specific embodiments of the present application both refer to 20-30°C.

[0042] It should be noted that the present application does not describe in detail the conventional operation means in the art, and is not the focus of the present application.

[0043] In some specific embodiments, the present application provides a method for preparing a low-ester pectin-corn starch-based fat substitute, the steps comprising:

[0044] S1, mixing low-ester pectin with water, continuously stirring at 35-45°C for 25-35 min to make it fully hydrated and dissolved, and preparing a pectin solution with a concentration of 3.5%-4.5% (w / v);

[0045] S2, the pectin solution obtained in step S1 is heated to 65-75°C, corn starch, calcium carbonate and soybean oil are added, and stirring is performed at a rotation speed of 600-1000 rpm for 25-35 min to form a uniform O / W emulsion, thereby obtaining an emulsion system; wherein the concentration of corn starch in the emulsion system is 5.5%-6.5% (w / v); the concentration of calcium carbonate in the emulsion system is 0.2%-0.3% (w / v); and the concentration of soybean oil in the emulsion system is 0-50% (w / v) and is not 0;

[0046] S3, the emulsion system obtained in step S2 is poured into a solution of 4.5%-5.5% (w / v) of gluconolactone (GDI) (volume ratio: emulsion system: gluconolactone solution = 1:2), and is allowed to stand at room temperature for 10-14 h to solidify, the gel formed after solidification is taken out, and is washed with water for 10-20 s to remove the surface unbound substances, thereby obtaining the low-ester pectin-corn starch-based fat substitute.

[0047] Example 1

[0048] The preparation steps of the low-ester pectin-corn starch-based fat substitute include:

[0049] S1, low-ester pectin is mixed with water, and is continuously stirred at 40°C for 30 min to allow it to be fully hydrated and dissolved, thereby preparing a pectin solution with a concentration of 4% (w / v);

[0050] S2, the pectin solution obtained in step S1 is heated to 70°C, corn starch, calcium carbonate and soybean oil are added, and stirring is performed at a rotation speed of 800 rpm for 30 min to form a uniform O / W emulsion, thereby obtaining an emulsion system; wherein the concentration of corn starch in the emulsion system is 6% (w / v); the concentration of calcium carbonate in the emulsion system is 0.25% (w / v); and the mass fraction of soybean oil in the emulsion system is 20%;

[0051] S3, the emulsion system obtained in step S2 is poured into a solution of 5% (w / v) of gluconolactone (volume ratio: emulsion system: gluconolactone solution = 1:2), and is allowed to stand at room temperature for 12 h to solidify, the gel formed after solidification is taken out, and is washed with water for 15 s to remove the surface unbound substances, thereby obtaining the low-ester pectin-corn starch-based fat substitute.

[0052] Example 2

[0053] Compared with Example 1, the only difference is that the concentration of soybean oil in the emulsion system is 10% (w / v), 30% (w / v), 40% (w / v) or 50% (w / v).

[0054] Comparative Example 1

[0055] The only difference from Example 1 is that the concentration of soybean oil in the emulsion system is 0% (w / v), that is, no soybean oil is added.

[0056] Comparative Example 2

[0057] The only difference from Example 1 is that the concentration of calcium carbonate in the emulsion system is 0% (w / v), that is, no calcium carbonate is added.

[0058] Test case

[0059] Examples 1, 2, and Comparative Example 1 are fat substitutes prepared at different oil concentrations. In the accompanying drawings, "emulsion gel" refers to the final product / sample of each example and comparative example.

[0060] Appearance features:

[0061] Figure 1 The figures show physical images of the low-ester pectin-corn starch-based fat substitutes prepared in Examples 1, 2, and Comparative Example 1. As can be seen from the figures, due to the emulsifying properties of corn starch and low-ester pectin, they can be uniformly dispersed with corn oil after shearing. With the addition of calcium carbonate and GDI, a solid structure is formed, exhibiting gel-like behavior. In the presence of GDI, calcium carbonate slowly releases Ca2+ in an acidic environment. 2+ Ca 2+ Further gel formation occurs with low-ester pectin. Corn starch is evenly dispersed in the low-ester pectin, allowing the corn starch-low-ester pectin and Ca... 2+ Better gel formation is achieved through better binding. The corn oil concentration significantly affects the appearance of the sample. When the oil concentration is 0%-30% (w / v), the emulsion gel forms a stable and uniform gel structure without oil or water leakage. When the oil concentration is further increased to 40% and 50% (w / v), phase separation occurs between the emulsion gel and the oil. When the oil concentration reaches 50% (w / v), oil seepage is more extensive. This separation is due to insufficient coverage of the continuous phase in the gel microstructure, which fails to effectively separate oil droplets. An appropriate oil concentration can act as an active filler in the continuous network matrix, forming a stable system and enhancing the gel network.

[0062] Texture:

[0063] The mechanical properties of the lyophilized emulsion gel were determined using a texture analyzer. The gel was placed on a substrate, surface moisture was removed, and then compressed to 30% deformation using a probe at a speed of 1 mm / s and a contact force of 0.04 N. Six parallel measurements were taken for each sample, and the mean values ​​were used to obtain the hardness, elasticity, chewiness, adhesiveness, resilience, and cohesion. The results are as follows: Figure 2 As shown.

[0064] Figure 2The performance of the fat substitutes prepared at different oil concentrations, wherein a is hardness, b is elasticity, c is resilience, d is gumminess, e is chewiness, and f is cohesiveness. As can be seen from the figure, the hardness decreases with the increase of oil concentration, and the elasticity, gumminess, chewiness, resilience, and cohesiveness all increase with the increase of oil concentration. The gel texture characteristic parameters show a trend of first increasing and then decreasing, and the gel texture characteristic parameters reach the maximum value at an oil concentration of 20% (w / v), and the texture difference is significant compared with other oil concentrations. Hardness reflects the structural strength of the emulsion gel to a certain extent. Low-ester pectin and corn starch are tightly combined, and with the increase of oil, the stable structure is destroyed, and the hardness decreases from 1.689 N to 0.644 N, showing a gradual downward trend, with a difference of 1.045 N, and the texture becomes soft. Regardless of the oil concentration, the hardness decreases significantly, while the elasticity increases significantly. The elasticity reaches the maximum value of 0.878 at an oil concentration of 20% (w / v), and the minimum value of 0.788 at an oil concentration of 50% (w / v), with a difference of 0.09. The elasticity of the gel is positively correlated with the integrity of the gel network structure. The resilience reaches the maximum value of 0.643 at an oil concentration of 20% (w / v), and the minimum value of 0.554 at an oil concentration of 50% (w / v), with a difference of 0.089. Chewiness reflects the resistance of the gel to tooth chewing, and reaches the maximum value of 0.777 N at an oil concentration of 20% (w / v), and the minimum value of 0.409 N at an oil concentration of 50% (w / v), with a difference of 0.368 N. Adhesiveness refers to the binding force within the gel, reflecting the property of the gel resisting damage and maintaining integrity when people chew, and reaches the maximum value of 0.886 N at an oil concentration of 20% (w / v), and the minimum value of 0.478 N at an oil concentration of 50% (w / v), with a difference of 0.408 N. Cohesiveness reaches the maximum value of 0.869 at an oil concentration of 20% (w / v), and the minimum value of 0.739 at an oil concentration of 50% (w / v), with a difference of 0.13. This shows that the combination between oil and pectin molecules is best at an oil concentration of 20% (w / v), and the gel network structure is relatively stable. With the further increase of oil concentration, the electrostatic repulsion caused by the electronegativity of anions between oil and pectin molecules becomes stronger, interfering with the cross-linking of the gel network and the formation of ordered gel, and thus reducing the elasticity, gumminess, chewiness, resilience, and cohesiveness of the gel. Therefore, we conclude that the elasticity, gumminess, chewiness, resilience, and cohesiveness of the gel are the largest at an oil concentration of 20% (w / v).

[0065] Rheological characterization:

[0066] The rheological properties of the sample of the examples and the comparative example were measured by a rheometer, equipped with a rough surface parallel plate geometry of 40 mm in diameter, a gap of 1 mm was set between the geometry and the Peltier plate, after the sample was uniformly placed on the Peltier plate, the parallel plate was loaded to start the test. At a strain of 0.1%, a frequency range of 0.01-10 Hz, a linear viscoelastic region was established, a dynamic frequency sweep was carried out, and the changes of the storage modulus and the loss modulus with the angular frequency were recorded, and the results are shown in Figure 3 .

[0067] Figure 3 The dynamic frequency sweep results of the product prepared for examples 1-2 and comparative example 1 were obtained. Linear rheological behavior is considered as a sensitive probe of biopolymer interactions. Therefore, dynamic frequency sweep can help us to understand the interactions between the components of the emulsion gel. By carrying out dynamic frequency sweep on the gel, the indicators G', G'' reflecting the viscoelastic properties of the system can be determined. These two parameters represent the elasticity (i.e. the ability of solid behavior) and viscosity (i.e. the performance of fluid) of the sample in turn. The storage modulus and the loss modulus of all samples change with the change of frequency, and G' is greater than G'', which indicates that the sample exhibits solid-like behavior and is a typical solid gel network dynamic viscoelastic rheological spectrum. As can be seen from the figure, within the frequency range of 0.01-10 Hz, the storage modulus of the gel increases from 15978 Pa, 14306 Pa, 10746 Pa, 5705 Pa, 4686 Pa and 4893 Pa to 18833 Pa, 18135 Pa, 13656 Pa, 9786 Pa, 7827 Pa and 7318 Pa, respectively, and the loss modulus increases from 2846 Pa, 2305 Pa, 1483 Pa, 1009 Pa, 1041 Pa and 1001 Pa to 3195 Pa, 2891 Pa, 1875 Pa, 1320 Pa, 1053 Pa and 1007 Pa, respectively. In the gel, the low ester pectin and CA 2+ form a continuous gel matrix, and the corn starch and the low ester pectin form a stable network structure through hydrogen bond interaction, while the oil droplets are embedded in the network structure to form a high-strength emulsified gel. However, more oil is not completely embedded in the network, so that too much oil is in an aggregated state, forming an uneven network structure. In addition, when the oil content is high, the stability of the gel decreases, and the greater the oil concentration, the smaller the G' and G''.

[0068] Large amplitude oscillatory shear (LAOS) test:

[0069] The LAOS measurement of the sample was carried out by a rheometer under the condition of a strain scanning range of 0.01%-1000% and a frequency of 1 Hz, and the results are shown in Figure 4 .

[0070] Figure 4The LAOS experimental results of the products prepared for Examples 1-2 and Comparative Example 1 are shown in the figure. As can be seen from the figure, the emulsified gel is an animal fat analogue, which usually undergoes large and rapid stress in actual processing and application, and often exceeds the LVR (referring to the region where the material shows a stress-strain proportional relationship under a small deformation, the LVR is the basis for rheological study of semi-solid preparations, and it reflects the linear viscoelastic response of the material under a small deformation). Therefore, the structural changes and gel strength changes of the emulsified gel in the nonlinear viscoelastic region (NLVR) were further studied to evaluate the performance of the hydrogel under medium amplitude oscillatory shear (MAOS) and large amplitude oscillatory shear (LAOS). The dynamic equilibrium microstructure of the emulsified gel in the LVR is proved by the constant G' and G", and the gel shows a shear-resistant state before reaching the critical strain. The G' and G" values reach the highest at the oil concentration of 20% (w / v) and the lowest at the oil concentration of 50% (w / v), indicating that the gel strength reaches the highest at the oil concentration of 20% (w / v). This result is consistent with the result of frequency sweep. γ represents the critical strain of G', which indicates the transition of the rheological behavior of the gel from linear strain to nonlinear strain. γ represents the balance point between maintaining structural integrity and shear deformation of the sample, and the γ of the gel increases with the increase of the oil concentration, and reaches the maximum value of 6.87% when the oil concentration is 20% (w / v), forming a more elastic gel network structure. With the continuous increase of the strain in the NLVR, the G' of the emulsified gel decreases significantly, and the G'' increases first and then decreases. The appearance of G" overshoot behavior indicates that the formation speed of the gel network structure is greater than the destruction speed under MAOS, and there is a strong interaction in the network to resist shear force. With the further increase of the strain to LAOS, the decrease rate of G' is greater than that of G'', the degree of damage to the gel structure increases, and finally leads to permanent deformation and liquefaction.

[0071] Determination of water holding capacity (WHC):

[0072] The sample temperature was restored to room temperature before testing. A certain amount of sample was weighed into a 15 mL centrifuge tube, centrifuged at 3 000 r / min for 15 min at room temperature, the surface moisture was absorbed with filter paper, and then weighed again, each test was repeated 3 times, and the results are shown in Table 1. Figure 5 The water holding rate calculation formula is as follows:

[0073] ;

[0074] In the formula: w is the water holding rate, %; m0 is the mass of the centrifuge tube, g; m1 is the total mass of the sample and the centrifuge tube before centrifugation, g; m2 is the total mass of the sample and the centrifuge tube after centrifugation, g.

[0075] Figure 5The figure shows the water-holding capacity of the products prepared in Examples 1-2 and Comparative Example 1. As can be seen from the figure, water-holding capacity reflects the stability of the emulsion gel, directly affecting its quality, texture, and mouthfeel as an animal fat analog. Although the oil-free gel system also has high water-holding capacity, the absence of oil hinders its use as a fat substitute. Generally, water-holding capacity depends on the microscopic network structure and interactions within the gel. The emulsion gel containing 20% ​​(v / w) oil exhibits the highest water-holding capacity due to the presence of a denser low-ester pectin gel network. Higher oil concentrations lead to oil droplet aggregation, structural instability, and reduced water-holding capacity of the emulsion gel. This result is consistent with observations using cryo-scanning electron microscopy, indicating a denser gel network at an oil concentration of 20% (v / w).

[0076] Confocal laser scanning microscope (CLSM):

[0077] Before preparing the emulsion gel, the aqueous and oil phases were stained with FITC and Nile Red, respectively. Then, appropriate amounts of calcium carbonate and GDI were added to obtain the gel described in Example 1. The excitation wavelength for FITC was 488 nm, and for Nile Red, it was 550 nm. The stained emulsion gel was dropped onto a glass slide and photographed using a CLSM instrument with 40x objective magnification. The results are as follows: Figure 6 As shown.

[0078] Figure 6 CLSM images of the products prepared in Examples 1-2 and Comparative Example 1 are shown. Confocal laser scanning microscopy can analyze gel type, observe the distribution of gel matrix and emulsion droplets in the system, and reveal the microstructure of emulsion gels. As can be seen from the figures, red oil droplets are surrounded by a green aqueous phase. When Ca... 2+ When corn starch and low-ester pectin were induced to form a continuous and stable gel matrix, oil droplets were successfully dispersed in the continuous phase, forming a stable and homogeneous gel system. With increasing oil concentration, the oil droplets aggregated more densely in the system, and significant droplet shedding occurred at concentrations greater than 20% (v / w). This may be because the amount of continuous matrix formed by corn starch and low-ester pectin is insufficient to create a mechanical barrier between adjacent oil droplets to prevent aggregation.

[0079] Low-field nuclear magnetic resonance:

[0080] The moisture state of the samples was determined using low-field nuclear magnetic resonance (NMR). Attenuated signals were acquired using a CPMG sequence. The waiting time was 5000 ms, the sampling frequency was 200 kHz, the repetition waiting time was 0.3 s, and the number of repetitions was 16. The results are as follows: Figure 7 As shown

[0081] Figure 7T2 relaxation spectra and relaxation parameters of the products were prepared for Examples 1-2 and Comparative Example 1. In the figure, low-field nuclear magnetic resonance is used to detect the water distribution in food, and further applied to the quality control of food systems, T2 relaxation spectra are divided into three forms according to the relaxation time: 0.1-10 ms (T 21 ), 10-100 ms (T 22 ), and 100-1000 ms (T 23 ). Corresponding to three states of water in the gel system, i.e. bound water, water not easy to flow and free water. T 21 represents free water that can move freely in the gel system, T 22 represents water tightly bound to polysaccharide macromolecules. T 23 represents water distributed in the emulsion gel network, which fluctuates with the gel structure.

[0082] The T 22 of the gel without oil is higher, indicating that due to the absence of oil, there is a large amount of water in the network structure of the gel, and the loose network structure cannot hold water, making water more easily flow. Ca 2+ induced emulsion gel T 22 and T 23 are obviously shifted to the right of the relaxation time, indicating that the gel has a stronger water binding capacity. However, when the oil concentration is 50% (w / v), the two peaks of T 22 and T 23 are connected, and the water binding capacity of the gel is weakened, indicating that too much oil can affect the water binding capacity. However, due to the instability of the network structure and the uneven pore size caused by the excessive aggregation of oil droplets, part of the free water may be retained, resulting in no further increase in free water.P 21、 P 22 and P 23 represent the peak area percentage of T 21 , T 22 and T 23 , respectively. In all emulsion gel samples, P 22 is the largest, indicating that the gel network forms a more flexible structure to capture water, thereby increasing the proportion of water not easy to flow.

[0083] With the increase of storage time, the signal intensity becomes weaker. It can be obviously observed that T 22 becomes smaller and smaller when the oil concentration is 0% (w / v), indicating that the water tightly bound to the polysaccharide macromolecules is constantly lost, and the structure is unstable without the addition of oil. When the oil concentration is 40% (w / v) and 50% (w / v), the connection of T 22 and T 23 two peaks is more obvious, further proving that the loose network structure cannot hold water. When the oil concentration is 20% (w / v), the three states of water in the gel system are best maintained.

[0084] Fourier Transform Infrared Spectroscopy:

[0085] The sample was placed in the field of the attenuated total reflection device, and gently contacted. The scanning range was 4000 cm -1 - 400 cm -l -1, with a resolution of 4 cm -1 -1. The results are shown in Figure 8

[0086] Figure 8 Fourier transform infrared spectroscopy was prepared for the product of Examples 1-2 and Comparative Example 1. Infrared spectroscopy is a reliable technique for revealing intermolecular interactions by analyzing the functional groups and shifts in the substance. As can be seen from the figure, the corn starch-low ester pectin gel has a distinct absorption peak at 3000-3600 cm -1 , which is a characteristic peak of intermolecular and intramolecular hydrogen bonds, attributed to the stretching vibration of -OH groups. The peak near 3000 cm -1 corresponds to the stretching vibration of C-H bonds directly connected to C=C bonds in oil. The absorption peak near 930-1200 cm -1 is a characteristic peak of polysaccharide functional groups, in addition, 900-1200 cm -1 is the characteristic peak region of starch. Compared with the corn starch-low ester pectin dispersion, the O-H absorption peak of the Ca 2+ induced gel is obviously shifted to low wavenumber, indicating that the main interaction of emulsion gel formation is hydrogen bond. Hydrogen bond can form a knot region between the network and the oil, increasing the network strength. When the oil concentration exceeds 20% (w / v), the peak near 3000 cm -1 to 3690 cm -1 becomes gradually wider, which may be due to the excess oil aggregation hindering the hydrogen bond force, reducing the uniformity of the network. The FTIR of emulsion gel with different oil concentrations shows similar characteristic peaks, and the characteristic peak intensity of oil in the emulsion gel gradually increases with the increase of oil concentration. The FTIR results support the existence of hydrogen bond interaction in the gel network structure.

[0087] Zeta Potential Measurement:

[0088] The sample was diluted to 6% (w / v) with deionized water, and the Zeta potential was determined using a nanoparticle size and Zeta potential analyzer, using a folded capillary cell at 25°C, with an equilibrium time of 120 s, and the optical setting was applied with a scattering detector angle of 90°, and the sample was measured in parallel for 3 times. The results are shown in Figure 9

[0089] Figure 9 ​​Zeta potential of the product was prepared for Example 1-2 and Comparative Example 1-2. The s potential of emulsion gels with different oil concentrations was measured to determine the relative surface charge level, which can characterize the stability of the particle system in the solution. As can be seen from the figure, the emulsion gel containing oil droplets has a larger absolute s potential value compared with the system without oil droplets. This increase can be due to the electrostatic repulsion between the droplets preventing aggregation and sedimentation, thus forming a stable emulsion gel system. In addition, there is no significant difference in the potential distribution of emulsion gels with different oil concentrations, indicating that the formation of the gel system is not strongly dependent on electrostatic interactions. Therefore, the main interaction in the emulsion gel is the hydrogen bond formed between the low-quality pectin and the corn starch, Ca 2+ crosslinking with low ester pectin.

[0090] Freeze scanning electron microscopy (SEM):

[0091] The cross section of the gel after freeze drying was determined by scanning electron microscopy. The gel was frozen, dried, and the freeze-dried gel was fixed on a conductive table, the edges were embedded with liquid conductive glue, and after gold spraying with a gold spraying instrument, the sample was placed in the scanning electron microscope sample chamber. At an acceleration voltage of 5 kV, the scanning electron microscope was used to observe at a magnification of 200X. The results are shown in Figure 10

[0092] Figure 10 SEM images of the product after freeze drying were prepared for Example 1-2 and Comparative Example 1-2. As can be seen from the figure, the microstructure of the emulsion gel with different oil concentrations was observed under the freeze scanning electron microscope at 200 times, and it was found that compared with the control sample without oil, the sample with oil had a smooth and uniform texture. Without Ca 2＋ induction, the sample without oil and calcium had a smooth sheet morphology, and the starch structure was wrapped in low ester pectin, and the structure was enhanced. Under the Ca 2＋ release system, a uniform network structure was formed. With the addition of oil, the compactness of the gel structure increased, and the pore distribution was uniform and the network structure was tightly interwoven. That is, the corn starch and low-quality pectin form a continuous network structure, and the emulsion droplets are embedded in the gel matrix to form a stable system. When the oil concentration is 20% (w / v), the oil droplets are uniformly dispersed in the emulsion gel network in the form of small droplets, and the structure is more compact, and there is no excessive oil leakage phenomenon. When the oil concentration is 40% (w / v) and 50% (w / v), there is a significant oil leakage phenomenon.

[0093] Peroxide value test (POV):

[0094] ​A 3 g sample was dissolved in 30 mL of acetic acid and chloroform, and then 1 mL of potassium iodide solution was added. The well-mixed solution was placed in the dark for 10 minutes, and then 30 mL of distilled water and 1 mL of starch indicator were added. Titration was performed with a 0.02 mol / L sodium thiosulfate solution. The results are shown in Table 1. Figure 11 POV was calculated by the following formula:

[0095] ;

[0096] In the formula, Wo is the weight of the sample (g), Vi is the consumed sodium thiosulfate solution of the blank (mL), Vz is the consumed sodium thiosulfate solution of the sample (mL), and C is the molar concentration of the sodium thiosulfate standard solution (mol / L).

[0097] Figure 11 A graph showing the change in the degree of lipid oxidation of the products prepared in Examples 1-2 and Comparative Example 1 over time is shown in FIG. 1. The degree of lipid oxidation is an important quality deterioration indicator of edible fats and is also a basic property of emulsified gels as animal fat analogs. Lipid oxidation is accompanied by the formation of primary and secondary oxidation products, such as peroxides and aldehydes. The POV values of the samples stored for 0, 3, 7, and 14 days are shown in Table 1. Figure 11 During storage, the POV values of the samples gradually increased. However, the POV value of the sample containing 20% (v / w) oil after 7 days was lower than that of the other samples, indicating that the appropriate amount of oil embedded in the gel network inhibited oxygen induction. In addition, the dispersion of starch granules on the surface of the oil droplets improved the oxidative stability of the polyunsaturated fatty acids.

[0098] Cooking loss:

[0099] The emulsion gel samples were heated in a convection oven (SEZ-2YG, Zhuhai Sanmeili Co., Ltd., Guangdong, China) at 160°C for 25 min. The cooking loss was calculated by the following formula:

[0100] ;

[0101] In the formula, W a is the weight of the sample before cooking (g), and W a is the weight of the sample after cooking (g).

[0102] Figure 12Cooking loss of the product was prepared for Example 1-2 and Comparative Example 1. The cooking performance of emulsified gel can be used to evaluate its morphological changes during cooking and the ability to provide food flavor. The cooking changes of emulsified gel are shown in the figure, and heat treatment leads to oil melting and deformation of the shape of emulsified gel. In addition, with the increase of oil content, the melting behavior of emulsified gel gradually decreases. While the gel with 20% (v / w) oil concentration retains the original structure to some extent. This may be because the formation of a tight network inhibits the melting of emulsified gel. However, further increase of oil concentration does not enhance the structure of emulsified gel. The unstable network structure in emulsified gel leads to the accumulation of a large amount of oil, resulting in its loss during cooking. In addition, the gel with 20% (v / w) oil concentration has the minimum cooking loss.

[0103] In summary, the present application optimizes the performance of corn starch-low ester pectin-based fat substitute by regulating the oil concentration (0%-50%), revealing the significant influence of oil concentration on gel properties, rheological behavior and microstructure. When the oil concentration is 20%, the system exhibits optimal comprehensive performance, including higher hardness, good viscoelasticity and stable three-dimensional network structure, indicating that under this condition, starch, pectin and oil form a stable composite gel through hydrogen bonding and hydrophobic interaction. However, excessive oil (>20%) will destroy the gel continuity, leading to a decrease in water holding capacity and mechanical properties. This result provides a solid theoretical basis for the development of functional fat substitutes in low-fat foods.

[0104] The present application uses low ester pectin and corn starch as the matrix to prepare fat substitutes by composite gel method, and explores the influence of different oil concentrations (0%, 10%, 20%, 30%, 40%, 50%) on their physicochemical properties, rheological properties and microstructure. The results show that with the increase of oil concentration, the water holding capacity, viscoelasticity and emulsion stability of the composite system increase significantly, but excessive oil phase (>20%) will lead to loose gel network structure and decreased hardness. When the oil concentration is 20%, the substitute exhibits optimal textural properties and the lowest oil separation rate, and scanning electron microscopy shows that it forms a uniform three-dimensional network structure. Fourier transform infrared spectroscopy (FTIR) confirms that starch, pectin and oil form a stable composite system through hydrogen bonding and hydrophobic interaction. This provides a feasible fat replacement scheme for the development of low-fat foods, and clarifies the key role of oil concentration in regulating the performance of substitutes.

[0105] The various embodiments in the specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between various embodiments can be referred to each other.

[0106] The foregoing description of the disclosed embodiments enables a person skilled in the art to make or use the application. Modifications of these embodiments will occur to persons of skill in the art, and that the appended claims are intended to cover all such modifications that do not depart from the true spirit and scope of the application. Therefore, the application is not limited to the embodiments shown but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a low-ester pectin-corn starch-based fat substitute, characterized in that the steps include... include: Dissolve low-ester pectin in water to prepare a pectin solution, then heat to 65-75℃, add corn starch, calcium carbonate and soybean oil, and stir until a uniform O / W type emulsion is formed to obtain the emulsion system. The emulsion system is poured into a gluconolactone solution, allowed to stand for reaction, and then rinsed. The resulting gel is a low-ester pectin-corn starch-based fat substitute.

2. The preparation method according to claim 1, characterized in that, The concentration of the pectin solution is 3.5%-4.5%.

3. The preparation method according to claim 1, characterized in that, The concentration of corn starch in the emulsion system is 5.5%-6.5%.

4. The preparation method according to claim 1, characterized in that, The concentration of calcium carbonate in the emulsion system is 0.2%-0.3%.

5. The preparation method according to claim 1, characterized in that, The concentration of soybean oil in the emulsion system is 0-50%, and not 0.

6. The preparation method according to claim 1, characterized in that, The concentration of the gluconolactone solution is 4.5%-5.5%.

7. The preparation method according to claim 1, characterized in that, The volume ratio of the gluconolactone solution to the emulsion system is 2:

1.

8. The preparation method according to claim 1, characterized in that, The static reaction time is 10-14 hours.

9. A low-ester pectin-corn starch-based fat substitute, characterized in that, The low-ester pectin-corn starch-based fat substitute is prepared by the preparation method according to any one of claims 1-8.

10. The application of the low-ester pectin-corn starch-based fat substitute of claim 9 in the preparation of low-fat foods.

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