Konjac glucomannan-based emulsion oil gel as well as preparation method and application thereof

Abstract

The invention discloses konjac glucomannan-based emulsion oil gel as well as a preparation method and application thereof, and belongs to the technical field of food processing. The preparation method comprises the following steps: (1) dissolving soybean protein isolate, whey protein isolate or gelatin and konjac glucomannan in water to prepare a composite solution; (2) adding camellia oil into the composite solution, and homogenizing to form an emulsion; and (3) freezing and drying the emulsion to obtain the konjac glucomannan-based emulsion oil gel. The konjac glucomannan is added to generate intermolecular hydrogen bonds and molecular chain entanglement with protein molecules to change the structure of the protein, and the konjac glucomannan and the protein molecules form a three-dimensional particle network in a continuous phase around liquid drops, so that the flowability of the liquid drops is limited, and the stability of the oil gel is enhanced. The oleogel compounded with the konjac glucomannan is more uniform in structure and better in oil holding effect. The method has the advantages of simple and feasible process route, short preparation time, easiness in industrial operation and wide application prospect.

Description

Technical Field

[0001] The invention relates to the technical field of food processing, and in particular to a konjac glucomannan-based emulsion oil gel and a preparation method and application thereof. Background Art

[0002] Oil gel refers to a certain amount of gelling agent that wraps liquid oil in a three-dimensional gel network, converting the liquid oil into a gel-like structure with the characteristics of solid fat. The combination of gelling factors self-assembles through hydrogen bonding, electrostatics and van der Waals interactions to form a network, capturing the liquid oil in it. It not only has the advantages of semi-solid oil viscoelasticity, low trans fatty acids and saturated fatty acids, but also can improve the shortcomings of oil oxidation and easy migration of oil. It has great potential in replacing plastic fats and is a new strategy for constructing zero-trans, low-saturated fatty acid plastic fat substitutes. At present, solidifying liquid vegetable oil to form oil gel to replace traditional plastic fats has become a hot topic that has attracted much attention.

[0003] The emulsion template method for preparing oil gel does not require very high temperatures and large amounts of surfactants. The preparation process is simple and safe, and it solves the problem that many large molecular hydrophilic biopolymer gel factors cannot be directly dispersed in hydrophobic oils. Therefore, the emulsion template method has great potential for constructing oil gel.

[0004] Proteins are food-grade hydrophilic biopolymers that can combine with oil to form a stable three-dimensional network structure during the formation of oil gels due to their intermolecular interactions and physical effects. They are considered to be excellent substances for preparing oil gels. For example, soy protein isolate (SPI) is a common high-quality plant protein. It has attracted widespread attention in the food industry due to its low cost, high utilization rate and high nutritional value. SPI has been successfully used in the development of oil gels using the emulsion template method. Whey protein isolate (WPI) is a by-product of the dairy industry. It contains a variety of effective ingredients, high nutritional content, biological value and a rich essential amino acid spectrum. WPI can be adsorbed onto the surface of liquid oil to form a solid interfacial film, which helps promote the formation of stable emulsions. Therefore, WPI has the ability to solidify liquid oils through the emulsion template method. Gelatin (gel) is derived from the partial hydrolysis of animal collagen, has excellent emulsification and gel properties, and has unique hydrophilicity and biocompatibility. It is widely used in the food industry.

[0005] Although proteins with amphiphilic properties can spontaneously diffuse and adsorb at the oil-water interface, the interfacial adsorption process is very slow and the interfacial film formed is not dense enough, resulting in poor stability of the emulsion and oil leakage in the prepared oil gel. At present, many studies have shown that the composite of multi-element systems can overcome the shortcomings of single-element systems. The composite of polysaccharides and proteins to prepare oil gels is an effective strategy to improve the stability of oil gels. The addition of polysaccharide particles not only changes the arrangement of proteins, but also forms a three-dimensional particle network in the continuous phase around the droplets, thereby limiting the fluidity of the droplets and enhancing the stability of the oil gel. The preparation of emulsion template oil gels by protein-polysaccharide and its application in food are widely used, but the performance of oil gels prepared by composites of different types of proteins and polysaccharides is widely debated.

[0006] Therefore, comparing different types of protein and polysaccharide composite oil gels in order to pursue oil gels with denser network structures, better oil holding capacity, and better texture is an issue that needs to be explored in the field of food processing. Summary of the invention

[0007] The purpose of the present invention is to prepare camellia oil gel with dense network structure, good oil holding capacity and excellent texture by screening an auxiliary agent with excellent performance suitable for preparing camellia oil gel.

[0008] To achieve the above object, the present invention adopts the following technical solution:

[0009] The present invention provides a method for preparing a konjac glucomannan-based emulsion oil gel, comprising the following steps:

[0010] (1) dissolving protein powder and konjac glucomannan in water to prepare a composite solution, wherein the protein is soy protein isolate, whey protein isolate or gelatin;

[0011] (2) adding camellia oil to the composite solution prepared in step (1) and homogenizing to form an emulsion;

[0012] (3) pre-freezing the emulsion and then freeze-drying it to obtain the konjac glucomannan-based emulsion oil gel.

[0013] The invention uses soybean protein isolate, whey protein isolate or gelatin as an oil gelling agent, konjac glucomannan as a thickener, and adopts an emulsion template method to prepare a camellia oil oil gel system. Studies have shown that compared with single protein-based oil gel, konjac glucomannan produces intermolecular hydrogen bonds and molecular chain entanglements with protein molecules, which enhances the network structure of the composite oil gel and improves the oil holding capacity and rheological properties.

[0014] In step (1), protein powder and konjac glucomannan are magnetically stirred at 800 rpm in an aqueous solution overnight to prepare a fully dispersed and uniform mixed solution.

[0015] Preferably, the mass percentage concentration of protein in the composite solution is 4%-8%, and the mass percentage concentration of konjac glucomannan is 0.4%-0.5%.

[0016] Preferably, the mass ratio of protein to konjac glucomannan in the composite solution is 10: 1. More preferably, the mass percentage concentration of protein in the composite solution is 4%, and the mass percentage concentration of konjac glucomannan is 0.4%.

[0017] In step (2), camellia oil is added to the composite solution prepared in step (1) and homogenized to fully mix the raw materials, and further homogenized at high speed to form a stable emulsion. Studies have shown that after adding konjac glucomannan, the particle size of the emulsion is reduced, and the stability and gel strength are significantly improved.

[0018] Preferably, the volume ratio of camellia oil to the composite solution is 0.5-0.8:1.

[0019] Preferably, the homogenizing conditions are: the speed of the homogenizer is 8000-12000 rpm and the temperature is 4°C.

[0020] More preferably, camellia oil is added to the composite solution, firstly homogenized at a rotation speed of 8000 rpm to fully mix the raw materials, and then homogenized at a rotation speed of 12000 rpm to form a stable emulsion.

[0021] In step (3), freeze-drying technology is used to remove water from the emulsion system to obtain a complex oil gel with a honeycomb network structure.

[0022] Preferably, the pre-freezing treatment conditions are: -80°C pre-freezing, and the treatment time is 24h.

[0023] Preferably, the freeze-drying treatment conditions are: freeze-drying at -80°C for 48 hours.

[0024] The present invention provides a konjac glucomannan-based emulsion oil gel prepared by the above-mentioned preparation method. The complex oil gel provided by the present invention has a dense spatial network structure, excellent texture performance, and good oil holding capacity. In particular, KGM has the best gain effect on plant-derived globular protein SPI, and the prepared oil gel has moderate hardness and is suitable for use as a substitute for solid fat; KGM and fibrous protein GE have the most dense network structure and the strongest hardness, and can be used to simulate the texture of meat products.

[0025] The present invention also provides the use of the konjac glucomannan-based emulsion oil gel as solid fat in processed meat products.

[0026] The present invention has the following beneficial effects:

[0027] (1) The present invention changes the structure of the protein by adding polysaccharide particles KGM to generate affinity and binding force with the protein, and combines with hydrogen, and the two also form a three-dimensional particle network in the continuous phase around the droplets, thereby limiting the fluidity of the droplets and enhancing the stability of the oil gel. The results show that the structure of the oil gel compounded with KGM is more uniform and the oil retention effect is better.

[0028] (2) The process of the present invention is simple and easy to implement, the preparation time is short, it is easy to industrialize and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Schematic diagram of the process flow for preparing emulsion oil gel using konjac glucomannan and protein composite.

[0030] Figure 2 These are the optical microscopy observation results of 4S(a), 4W(b), 4G(c), 4S0.4K(d), 4W0.4K(e), and 4G0.4K(f) emulsions prepared in Examples 1-6.

[0031] Figure 3 The particle size (a), particle size volume distribution diagram (b), potential diagram (c) and TSI value (d) of the emulsions prepared in Examples 1 to 6. Different lowercase letters indicate significant differences (P<0.05).

[0032] Figure 4 is the backscattered light (BS) intensity of the emulsions obtained in Examples 1-6.

[0033] Figure 5 Rheological properties of the emulsions obtained in Examples 1-6, (a) 0.1-100% strain scan to determine LVR, (b) tangent change (tanδ) as a function of strain scan, (c) viscosity-shear rate scan curve, (d) 0.1-100 Hz frequency scan.

[0034] Figure 6 Scanning electron micrographs of 4S(a), 4W(b), 4G(c), 4S0.4K(d), 4W0.4K(e), and 4G0.4K(f) oil gels prepared in Examples 1-6.

[0035] Figure 7 The oil gel prepared in Examples 1-6 is at 4000-500cm -1 FTIR spectrum of the oil gel in this area.

[0036] Figure 8 The test results of hardness (a), cohesion (b), chewiness (c), and oil storage capacity (d) of the oil gels prepared in Examples 1-6 are shown.

[0037] Fig. 9 The rheological properties of the oil gels obtained in Examples 1-6, wherein (a) is strain scanning; (b) is frequency scanning; (c) is the change of viscosity with shear rate; (d) is the thixotropic scanning curve; (e) is temperature scanning; and (f) is temperature scanning. DETAILED DESCRIPTION

[0038] The present invention will be further described below in conjunction with specific embodiments. The following embodiments are only used to illustrate the present invention and are not intended to limit the scope of application of the present invention. Without departing from the spirit and essence of the present invention, modifications or replacements made to the inventive method, steps or conditions all belong to the scope of the present invention.

[0039] Unless otherwise specified, the experimental methods used in the following examples are all conventional methods; the materials and reagents used are reagents and materials that can be obtained from commercial channels unless otherwise specified.

[0040] The soy protein isolate (dispersible reagent) and gelatin (dispersible reagent) used in the following examples were purchased from Hangzhou Bangyi Chemical Co., Ltd. (Hangzhou); whey protein isolate (purity = 80%) was purchased from Shanghai Yuanye Biotechnology Co., Ltd. (China); konjac glucomannan (purity> 90%) was purchased from Hubei Zhiyi Technology Biological Co., Ltd. Camellia oil (freezing point is -5 to 10 ° C) was purchased from a local supermarket. The water used in the entire experiment was distilled water.

[0041] The following example uses three different types of proteins and konjac glucomannan (KGM) to prepare oil gel by emulsion template method. Figure 1 shown.

[0042] Example 1: Preparation of soy protein isolate-based oil gel

[0043] Accurately weigh the required protein powder (prepare concentration gradient 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%) and dissolve it in a certain amount of water to ensure full dispersion and uniform mixing to prepare soy protein isolate (SPI) solutions of different mass concentrations.

[0044] Camellia oil was added to the SPI solution at a volume ratio of 0.8:1, and a high-speed homogenizer (T18, IKA, Germany) was used to homogenize for 3 minutes at 8000 rpm at 4°C to ensure that the camellia oil and protein were fully mixed, and then homogenized for 5 minutes at 12000 rpm to form a stable emulsion. Subsequently, the above sample was placed in an ultra-low temperature refrigerator at -80°C for pre-freezing for 12 hours, then freeze-dried at -80°C for 48 hours, and then subjected to a simple shearing treatment to obtain the SPI-based oil gel.

[0045] Example 2: Preparation of soy protein isolate-konjac glucomannan-based oil gel

[0046] Accurately weigh the required protein powder (prepare concentration gradient 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%) and konjac glucomannan (KGM) powder (the mass ratio of KGM to protein is 1:10) and dissolve them in a certain amount of water to ensure sufficient dispersion and uniform mixing, and prepare mixed solutions of soy protein isolate (SPI) and konjac glucomannan (KGM) with different mass concentrations.

[0047] An appropriate amount of camellia oil was added to the mixed solution at a volume ratio of 0.8:1, and a high-speed homogenizer (T18, IKA, Germany) was used to homogenize for 3 minutes at 4°C and 8000 rpm to ensure that the camellia oil and protein-polysaccharide were fully mixed, and then the homogenization was continued at 12000 rpm for 5 minutes to form a stable emulsion. Subsequently, the above sample was placed in an ultra-low temperature refrigerator at -80°C for pre-freezing, then freeze-dried for 48 hours, and then subjected to a simple shearing treatment to obtain the SPI-KGM-based oil gel.

[0048] Example 3: Preparation of whey protein isolate-based oil gel

[0049] Accurately weigh the required protein powder (prepare concentration gradient 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%) and dissolve it in a certain amount of water, ensuring full dispersion and uniform mixing to prepare whey protein isolate (WPI) solutions of different concentrations.

[0050] An appropriate amount of camellia oil was added to the WPI solution at a volume ratio of 0.8:1, and a high-speed homogenizer (T18, IKA, Germany) was used to homogenize for 3 minutes at 8000 rpm at 4°C to ensure that the camellia oil and protein were fully mixed, and then the homogenization was continued at 12000 rpm for 5 minutes to form a stable emulsion. Subsequently, the above sample was placed in an ultra-low temperature refrigerator at -80°C for pre-freezing, then freeze-dried for 48 hours, and then subjected to a simple shearing treatment to obtain a WPI-based oil gel.

[0051] Example 4: Preparation of whey protein isolate-konjac glucomannan-based oil gel

[0052] Accurately weigh the required protein powder (prepare concentration gradient 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%) and konjac glucomannan (KGM) powder (KGM to protein mass ratio is 1:10) and dissolve them in a certain amount of water to ensure full dispersion and uniform mixing. Prepare mixed solutions of whey protein isolate (WPI) and konjac glucomannan (KGM) of different mass concentrations.

[0053] An appropriate amount of camellia oil was added to the mixed solution at a volume ratio of 0.8:1, and a high-speed homogenizer (T18, IKA, Germany) was used to homogenize for 3 minutes at 4°C and 8000 rpm to ensure that the camellia oil and protein-polysaccharide were fully mixed, and then the homogenization was continued at 12000 rpm for 5 minutes to form a stable emulsion. Subsequently, the above sample was placed in an ultra-low temperature refrigerator at -80°C for pre-freezing, then freeze-dried for 48 hours, and then subjected to a simple shearing treatment to obtain a WPI-KGM-based oil gel.

[0054] Example 5: Preparation of gelatin-based oil gel

[0055] Accurately weigh the required protein powder (prepare concentration gradient 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%) and dissolve it in a certain amount of water, ensure full dispersion and uniform mixing, and prepare gelatin (GE) solutions of different concentrations.

[0056] An appropriate amount of camellia oil was added to the GE solution at a volume ratio of 0.8:1, and a high-speed homogenizer (T18, IKA, Germany) was used to homogenize for 3 minutes at 4°C and 8000 rpm to ensure that the camellia oil and protein were fully mixed, and then the homogenization was continued at 12000 rpm for 5 minutes to form a stable emulsion. Subsequently, the above sample was placed in an ultra-low temperature refrigerator at -80°C for pre-freezing, then freeze-dried for 48 hours, and then a simple shearing treatment was performed to obtain a GE-based oil gel.

[0057] Example 6: Preparation of gelatin-konjac glucomannan-based oil gel

[0058] Accurately weigh the required protein powder (prepare concentration gradient 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%) and konjac glucomannan (KGM) powder (the mass ratio of KGM to protein is 1:10) and dissolve them in a certain amount of water, ensuring full dispersion and uniform mixing, to prepare mixed solutions of gelatin (GE) and konjac glucomannan (KGM) with different concentrations.

[0059] An appropriate amount of camellia oil was added to the mixed solution at a volume ratio of 0.8:1, and a high-speed homogenizer (T18, IKA, Germany) was used to homogenize for 3 minutes at 4°C and 8000 rpm to ensure that the camellia oil and protein were fully mixed, and then the homogenization was continued at 12000 rpm for 5 minutes to form a stable emulsion. Subsequently, the above sample was placed in an ultra-low temperature refrigerator at -80°C for pre-freezing, then freeze-dried for 48 hours, and then a simple shear treatment was performed to obtain a GE-KGM-based oil gel. Test Example 1: Microstructural Characterization of Emulsion

[0060] 1. Test methods

[0061] A polarizing microscope (DM750P, Leica, Germany) equipped with a digital camera was used to capture images to explore the microstructure and particle size distribution of the emulsion samples prepared with different components.

[0062] First, the emulsion samples were diluted ten times to ensure the clarity and observability of the samples under the microscope. A small drop of the diluted sample was placed on a glass slide for the microscope, and then gently covered with a cover glass to observe the size and aggregation state of the emulsion droplets. In addition, in order to more accurately analyze the particle size, the Image J image analysis software was used to process and analyze the images taken under the microscope to obtain the average particle size of the emulsion particles.

[0063] 2. Results Analysis

[0064] According to the results of microscopic observation, the protein concentration is within the range of 3%-8% to form an oil-in-water emulsion, and the emulsion formed by 3% protein concentration is extremely unstable and breaks in a short time. In order to ensure the smooth progress of the experiment, a 4% protein concentration was selected. In addition, when the KGM concentration is too high (>1%), a hydrosol will be formed. When the concentration is >0.5%, the protein-KGM solution is too viscous, and it is difficult to achieve the desired homogenization effect during the preparation of the emulsion. A 0.4% KGM concentration was selected, and the subsequent experimental results were obtained according to the 4% protein and 0.4% KGM concentrations.

[0065] Figure 2 Schematic diagram of the microstructure of the emulsion prepared in Examples 1 to 6. The results show that the droplet size of the protein-based emulsion alone is large and unevenly distributed. After the addition of KGM, the particle size of the emulsion decreases. This is because KGM interacts with protein to promote the unfolding of the protein structure, exposing hydrophobic residues, increasing the affinity of the protein for the oil-water interface, and the complex adsorbs on the surface of the oil droplets to form a thicker adsorption layer, reducing the interfacial tension. In addition, the soy protein-based emulsion has the largest droplets because the molecular weight of the soy protein itself is large. The gelatin-based emulsion has the smallest droplet size and is severely aggregated because the molecular weight of the gelatin itself is small and the aqueous solution has a certain viscosity, making it more prone to aggregation. Test Example 2: Particle Size and Zeta-Potential of Emulsion

[0066] 1. Test methods

[0067] The droplet size of the emulsions of Examples 1-6 was evaluated using a Nano ZS90 dynamic laser scattering instrument (Malvern Instruments, Malvern, UK). The different component emulsions were diluted 1000 times with deionized water, and a small amount of the diluted solution was transferred to a measuring cup. The refractive index was set to 1.470 for particles and 1.330 for dispersion. Three measurements were performed at 25°C and the average value was taken.

[0068] 2. Results Analysis

[0069] like Figure 3 As shown in (a), after adding KGM, the particle size of the emulsion was significantly reduced compared with the single protein group, which corresponds to the results of the above microstructure diagram.

[0070] like Figure 3 As shown in (b), the peak of the emulsion prepared by single protein is in a larger particle size range, while the peak of the composite emulsion shifts to the left and the particle size tends to decrease; and the emulsion prepared by gelatin has a double peak, indicating that its particle size distribution is uneven and there are particles in two size ranges.

[0071] The zeta potential of different emulsions is Figure 3 As shown in (c), the potential values ​​of all components of the emulsion are negative. This is because the pH value of the emulsion is greater than 7, which is greater than the isoelectric point of the protein. At this time, the protein carries a negative charge; and under alkaline conditions, KGM deacetylation carries a negative charge, which in turn produces an electrostatic interaction with the protein. Therefore, after adding KGM, the absolute value of the potential of the emulsion increases.

[0072] Test Example 3: Emulsion Stability

[0073] 1. Test methods

[0074] Measurement of Turbiscan stability index TSI and backscattered BS value of emulsion: The stability of emulsion was quickly analyzed at 25°C using a multi-light scattering instrument (Turbiscan Tower, Formulaction, France). The prepared emulsion was transferred to a tube matched with the emulsion stability analyzer and scanned from bottom to top every 10 min for 12 h using built-in near-infrared light (880 nm). The changes in samples of different components were analyzed based on two synchronous optical detectors and monitoring of backscattered (BS) and Turbiscan stability index (TSI) of pulsed near-infrared light (λ = 880 nm).

[0075] 2. Results Analysis

[0076] According to the results of emulsification stability analysis, the water-in-oil emulsion formed in the protein concentration range of 4%-8% has better stability, while the emulsion formed by 3% protein concentration breaks within half an hour and is not suitable for experiments, so 4% protein concentration was selected. In addition, the emulsification stability is poor when the KGM concentration is <0.2, so 0.4% KGM concentration was selected, and the subsequent experimental results were obtained according to 4% protein and 0.4% KGM concentrations.

[0077] like Figure 3As shown in (d), the order of TSI is: 4W>4S>4W0.4k>4S0.4K>4G>4G0.4K, that is, the stability of the single protein emulsion is worse than that of the composite emulsion, and the stability of the GE-based emulsion is the best. This is consistent with the change law of ΔBS, that is, the stability of the emulsion is improved after adding KGM.

[0078] The backscattering results are as follows Figure 4 As shown in the figure: With the increase of time, the ΔBS at the bottom of all emulsion tubes decreases, the bottom is clear, the top is emulsified, and after reaching a stable state, the increase in backscattering of the upper emulsion decreases. After adding KGM compound, the emulsion layer of all emulsions is significantly reduced, and the emulsion layer of KGM-SPI is the smallest and has better stability. This is because the electrostatic repulsion of the KGM-SPI composite emulsion is the largest, and the aggregation and collision effect of hindering droplet shear is the most obvious; while the WPI-based emulsion has the worst stability.

[0079] Test Example 4: Rheological properties analysis of emulsion

[0080] 1. Test methods

[0081] The rheological measurements of the emulsions prepared in Examples 1-6 were performed using a rotational rheometer (MCR 302, Anton Paar, Austria) equipped with a temperature control system and aluminum plates (PP50, gap = 1.0 mm). The specific parameters were set as follows: the measurement temperature was 25°C, the equilibrium time was 60 s, the plate gap was set to 1 mm; the shear rate was set from 0.1 s -1 Up to 100s -1 During the process, 30 data points were taken to examine the variation of the emulsion viscosity with the shear rate; the amplitude of the applied scanning stress ranged from 0.01 to 100% to determine the linear viscoelastic region (frequency = 1 Hz). According to the amplitude scanning graph, the region where the modulus does not change with the amplitude is the linear viscoelastic region, so a strain of 0.1% was selected for the frequency scanning experiment, and the oscillation frequency was continuously increased from 0.1 Hz to 100 Hz.

[0082] 2. Results Analysis

[0083] like Figure 5 As shown in (a): G′ and G″ of KGM-GE composite emulsion show similar change trends and are basically equal, showing semi-solid characteristics; G′ and G″ of KGM-SPI are the largest, and G′ and G″ of KGM-GE are the smallest.

[0084] like Figure 5As shown in (b): At low shear stress, tanδ<1 (i.e., G′>G″), the emulsion exhibits solid-like properties; as the stress increases, G′ and G″ intersect (tanδ=1) or even G″ is greater than G′ (tanδ>1), indicating that under higher stress, the emulsion gradually changes from solid to liquid due to the destruction of its internal structure.

[0085] like Figure 5 As shown in (c): The initial viscosity values ​​of 4S0.4K and 4G0.4K composite emulsions are higher than those of the other groups, followed by 4W0.4K, while 4W has the lowest initial viscosity, indicating that KGM contributes to the viscosity of the emulsion.

[0086] like Figure 5 As shown in (d): With the addition of KGM, the elastic modulus and viscous modulus values ​​of the emulsion also increase, indicating that the gel strength of the emulsion is enhanced, and the gel structure is stable under high frequency and is not easily destroyed.

[0087] Test Example 5: SEM scanning electron microscope image of oil gel

[0088] 1. Test methods

[0089] The microstructure of the oil gel was observed using a scanning electron microscope (G300, Zeiss, Germany). The electro-carbon tape was attached to the stage holding the oil gel, and then the oil gel was attached to the electro-carbon tape. Subsequently, the sample was frozen in liquid nitrogen for 30 seconds. Using a low-temperature preparation transfer system, the oil gel was transferred to a preparation chamber under vacuum conditions for sublimation gold plating. After sublimation at -90 ° C for 10 minutes, gold was sputtered at a current of 10 mA for 60 seconds and high-magnification photography was performed at 3 kV.

[0090] 2. Results Analysis

[0091] The results are as follows Figure 6 As shown: n-hexane was used instead of the oil phase for SEM testing to analyze the structure of the oil gel. SPI, WPI and GE oil gels all showed honeycomb protein networks, and the GE oil gel honeycomb network was the densest and compact. SPI showed a sparse honeycomb structure, and the WPI network structure was weak. Under a high-power microscope, it appeared as a fault network structure with disconnections between the network layers. When magnified 1000 times, it only showed a planar lamellar effect, which resulted in the corresponding oil gel having poor performance. After adding KGM, KGM interacted with protein to enhance the network structure of the gel, the honeycomb pores increased, the pore size decreased, and the spatial network structure became denser.

[0092] Test Example 6: Oil gel FTIR analysis

[0093] 1. Test methods

[0094] The changes in the functional groups of the oleogels of Examples 1-6 were studied using an attenuated total reflection infrared spectrometer (Thermo Nicolet Ltd, USA) with a wavelength variation of 400 to 4000 cm -1 , with 4cm -1 The resolution was scanned 32 times.

[0095] 2. Results Analysis

[0096] like Figure 7 As shown in the figure, the absorption bands of the oil gel sample are related to the functional groups of protein and KGM. The SPI, WPI, GE and KGM powders are all pure structures. The protein powder has an absorption band of 1742 cm -1 There is an obvious characteristic peak of -C=O ester group at 1639cm -1 There is an obvious acetyl characteristic peak near it; in addition, the significant characteristic peak of protein powder is at 3200cm -1 It appears near the stretching vibration of -OH. After adding KGM to prepare the oil gel, the characteristic peak range of hydroxyl group becomes wider, at 3000~3500cm -1 The absorption peak of -OH stretching vibration shifts in the range of 2927cm -1 and 2853cm -1 The absorption band nearby is the stretching vibration of -CH. The -CH absorption peak of the oil gel shows obvious stretching. The protein powder has a peak at 1742cm -1 The absorption peak at 1750cm is caused by the stretching vibration of -C=O in triglyceride. -1 The C=O stretching vibration at 1072 cm -1 The nearby stretching vibration peaks are the result of CO and CC bonds within the molecule.

[0097] Test Example 7: Oil gel texture analysis

[0098] 1. Test methods

[0099] The texture characteristics of the oil gel were characterized by a texture analyzer (TA.XT Plus 100c, Stable Micro System, UK). A PP25 cylindrical probe (diameter = 25 mm) was used for compression mode. The probe descending speed was set to 2 mm / sec before the test, the ascending speed was 5 mm / sec, the trigger force was 5 g, the probe was inserted into the sample to a depth of 30%, and the sample was pressed down (at a rate of 1 mm / sec). Three parallel experiments were conducted for each oil gel, and the peak force during the pressing process was the hardness value.

[0100] 2. Results Analysis

[0101] Hardness Figure 8 As shown in (a): The SPI-based oil gel has the lowest hardness, only about 50g, while the GE oil gel has a hardness of up to 2324g, which is the hardest among the three groups of single-protein oil gels; the hardness of the oil gel prepared by adding KGM is significantly increased compared with the single-protein group, indicating that KGM can provide certain support for the structural strength of the three-dimensional network structure of the oil gel.

[0102] Cohesion Figure 8 (b) shows: KGM-composite oil gel has higher binding ability, the cohesion of KGM-SPI is increased from 0.4 to 0.51, the cohesion of KGM-WPI is slightly increased from 0.24 to 0.30, and that of KGM-GE is increased to 0.77. The above results show that the composite gel structure is stronger, but the internal network structure is relatively brittle and more easily damaged after the first pressure, while the gel prepared by single protein has relatively softer and tougher properties.

[0103] like Figure 8 (c) shows that chewiness is positively correlated with hardness, showing the same trend as hardness. In food products, when oil gel is used as a substitute for solid fat, its hardness and chewiness should not be too high. When oil gel is used to simulate the texture of meat products, it needs to meet certain hardness and chewiness standards.

[0104] As shown in Table 1, hardness, cohesion, and resilience all have the same trend, that is, with the addition of KGM, the texture performance is significantly improved. Chewiness has the same trend as hardness and adhesion.

[0105] Table 1. Texture parameters of protein / KGM-based oil gels

[0106]

[0107] Test Example 8: Oil retention analysis of oil gel

[0108] 1. Test methods

[0109] The oil holding rate of the oil gel was determined by centrifugation. 1.5-2.0 g of the oil gel was weighed into a 50 mL centrifuge tube and centrifuged at 12000 rpm for 15 min at 20 °C using a high-speed centrifuge (HC-3018R, ZONKIA, China). After centrifugation, the centrifuge tube was inverted for 20 min, and the unabsorbed oil was removed with filter paper and weighed (each sample was repeated 3 times). The oil content was calculated using the following formula:

[0110]

[0111] M1: mass of empty centrifuge tube; M2: total mass of centrifuge tube and oil gel; M3: total mass of centrifuge tube and oil gel after centrifugation to remove liquid oil.

[0112] 2. Results Analysis

[0113] According to the results of oil retention analysis, the oil retention is poor when the KGM concentration is <0.4. Compared with the oil retention of single protein (about 80%), it is only slightly improved by about 3%. Obviously, the poor gain effect is not comparable, so a KGM concentration of 0.4% was selected, and subsequent experimental results were obtained based on 4% protein and 0.4% KGM concentrations.

[0114] Oil gel oil holding capacity Figure 8 As shown in (d): When KGM is 0wt%, the OHC value is relatively low, the WPI oil gel is as low as 77.53%, and the GE oil gel has the largest oil holding rate, up to 99%; after adding KGM, the oil holding capacity of SPI is increased from 80% to 91.4%, and WPI is increased to 89.2%, but the oil holding rate of GE is only slightly increased after adding KGM because the original oil holding rate is very high.

[0115] Test Example 9: Rheological properties analysis of oil gel

[0116] (1) Strain sweep

[0117] The linear viscoelastic region was determined by analyzing the variation trends of the viscous modulus and elastic modulus in the range of 0.01 to 100% strain at a constant frequency of 1 Hz.

[0118] (2) Frequency sweep

[0119] The oscillation frequency sweep test mode was selected to study the frequency dependence of the oil gel. A strain value of 1% (within the linear region) and a frequency range of 0.1 to 100 Hz were selected to perform an oscillation sweep test to analyze the frequency dependence of the oil gel.

[0120] (3) Steady shear viscosity scan

[0121] At 25°C, by changing the shear rate (from 0.1 to 100 S -1 )Record the viscosity change trend, use logarithmic mode for data acquisition, and then study the relationship between sample viscosity and shear rate.

[0122] (4) Thixotropic recovery test

[0123] The low (0.1s) -1 ), high (10s -1 ) and low (0.1s -1) shear rate was used for continuous shear treatment, and the ratio of the initial viscosity to the final viscosity was recorded to determine the thixotropic recovery rate.

[0124] (5) Temperature scanning

[0125] The temperature sweep was performed with a heating rate of 5°C / min at a frequency (1 Hz) and a strain of 0.1% in the heating and cooling stages from 20 to 95°C.

[0126] 2. Results Analysis

[0127] like Fig. 9 As shown in (a): After adding KGM, the LVR limit of the oil gel was significantly extended, and the critical stress value was significantly higher than that of the single protein group, indicating that the addition of KGM improved the stability of the oil gel.

[0128] like Fig. 9 As shown in (b): The G′ of the oil gel of all components increases with the increase of frequency, and all show an elasticity-dominated trend that G′ is greater than G”. Among the three proteins, GE has the smallest rate of increase in G with frequency, the strongest structure, and the weakest frequency dependence. With the addition of KGM, the values ​​of G′ and G” will increase. This may be because KGM in the aqueous phase increases the attraction between oil droplets through a bridging effect, which is beneficial to enhancing the strength of the gel.

[0129] like Fig. 9 (c) 0.1~10S -1 Within the shear range, all component samples exhibited typical shear thinning behavior under high-speed shear, and GE had the largest initial viscosity value, indicating that it had a stronger ability to resist external shear; and the viscosity value increased after the addition of KGM. These results indicate that KGM and protein contribute to the viscosity of the oil gel.

[0130] Thixotropy Fig. 9 (d) shows: initial 0.1s -1 Within the range, each sample exhibited shear thinning behavior, and the addition of KGM led to an increase in viscosity, indicating that KGM had a certain contribution to the viscosity of the oil gel; the shear rate was rapidly increased to 10s -1 When the shear rate was restored to 0.1s -1 The recovery rate of the KGM-GE group was as high as over 80%, and its elastic network structure was the strongest, with better resistance to shear force, indicating that the network structure contributed significantly to the rheological properties of the oil gel, but there was no obvious improvement compared with the GE group, indicating that KGM had a poor gain effect on linear protein.

[0131] The results of the oil gel temperature scan are as follows Fig. 9As shown in (e) and (f): the modulus of WPI-based oil gel decreases rapidly at around 40°C, indicating that its thermal stability is the worst; the addition of KGM has no obvious effect on GE, but enhances the thermal stability of WPI and SPI; on the contrary, as the temperature drops from 95°C to 20°C, the G values ​​of the oil gels of all components show an upward trend, but have not fully recovered to the original G value, and the G recovery effect of the oil gel with the addition of KGM is better, indicating that the addition of KGM can improve the structure and thermal stability of the oil gel.

[0132] Summarize:

[0133] In the above experiment, three different types of proteins were used as oil gelling agents, KGM was used as a thickener, and the oil gel system was prepared by the emulsion template method. The results showed that compared with the single protein-based oil gel, KGM produced intermolecular hydrogen bonds and molecular chain entanglements with protein molecules, which enhanced the network structure of the composite oil gel, especially when KGM was compounded with GE (linear protein molecules), a highly dense honeycomb network structure was presented. The formed oil gel had the best OHC and the largest hardness value, which was more suitable for simulating the texture of meat products. However, there was no obvious gain effect compared with the single GE-based oil gel, and the oil gel prepared by KGM and SPI, WPI (globular protein) was denser than the single protein network structure, and the OHC and hardness values ​​were also larger, which was more suitable for solid fat replacement. The FTIR properties of the oil gel prepared by adding KGM also changed. In addition, the oil gel prepared by KGM and protein had better rheological properties (higher yield stress, stronger elasticity and thixotropic behavior). All the results showed that KGM and protein composite oil gel had a synergistic effect, and the gain effect on globular protein was better.

[0134] The embodiments described above provide a detailed description of the technical solutions and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, supplements and equivalent substitutions made within the scope of the principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a konjac glucomannan-based emulsion oil gel, characterized in that: The following steps are involved: (1) dissolving protein powder and konjac glucomannan in water to prepare a composite solution, wherein the protein is soy protein isolate, whey protein isolate or gelatin; (2) adding camellia oil to the composite solution prepared in step (1) and homogenizing to form an emulsion; (3) pre-freezing the emulsion and then freeze-drying it to obtain the konjac glucomannan-based emulsion oil gel.

2. The method for preparing a konjac glucomannan-based emulsion oil gel as claimed in claim 1, wherein: In step (1), the mass percentage concentration of protein in the composite solution is 4%-8%, and the mass percentage concentration of konjac glucomannan is 0.4%-0.5%.

3. The method for preparing a konjac glucomannan-based emulsion oil gel according to claim 1 or 2, wherein: The mass ratio of protein to konjac glucomannan in the composite solution is 10:1; the volume ratio of camellia oil to the composite solution is 0.5-0.8:

1.

4. The method for preparing a konjac glucomannan-based emulsion oil gel according to claim 1, wherein: In step (2), the homogenization conditions are: the speed of the homogenizer is 8000-12000 rpm and the temperature is 4°C.

5. The method for preparing the konjac glucomannan-based emulsion oil gel according to claim 1 or 4, wherein: In step (2), camellia oil is added to the composite solution, firstly homogenized at a rotation speed of 8000 rpm to fully mix the raw materials, and then homogenized at a rotation speed of 12000 rpm to form a stable emulsion.

6. The method for preparing the konjac glucomannan-based emulsion oil gel according to claim 1, wherein: In step (3), the pre-freezing treatment conditions are: -80°C pre-freezing, and the treatment time is 24h.

7. The method for preparing the konjac glucomannan-based emulsion oil gel according to claim 1, wherein: In step (3), the freeze-drying treatment conditions are: freeze-drying at -80°C for 48 hours.

8. A konjac glucomannan-based emulsion oil gel prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the konjac glucomannan-based emulsion oil gel as claimed in claim 8 as solid fat in processed meat products.

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