Preparation method of pre-emulsion gel based on gelatin and vegetable oil

Abstract

The invention belongs to the technical field of food processing, and particularly relates to a preparation method of pre-emulsion gel based on gelatin and vegetable oil. The method comprises the following steps: (1) mixing edible gelatin with hot water according to a mass ratio of 1: 3, and stirring at a stirring speed of 200-500r / min under the condition of 60-100 DEG C until the edible gelatin is completely dissolved to form a gelatin solution; and (2) mixing the gelatin solution with vegetable oil according to the mass ratio of 1: 1, and homogenizing and emulsifying for 3-7 minutes by adopting a high-speed dispersion homogenizer at the rotating speed of 8000-12000r / min to prepare the pre-emulsion gel. By optimizing the preparation process of the gelatin pre-emulsion, the problem of oil-layer separation is solved, and the application advantages of the gelatin pre-emulsion in meat products are proved.

Description

Technical Field

[0001] The present invention belongs to the technical field of food processing, and particularly relates to a preparation method of a pre-emulsion gel based on gelatin and vegetable oil. Background Art

[0002] The oil droplets in the emulsion gel can be in the form of liquid or solid lipid particles with a certain hardness. As a soft solid material that entraps oil droplets in a gel network, the stability of its system is directly related to the texture characteristics and ultimately the quality performance of meat products. Currently, the animal fat substitution technology mainly faces two technical bottlenecks:

[0003] Oil layer separation problem: In traditional processes, an imbalance in the ratio of vegetable oil to gelatin or improper control of the emulsification process parameters can easily lead to a layering phenomenon in the emulsion system;

[0004] Functional defect problem: Simply reducing the addition amount of animal fat will weaken the water retention performance and taste characteristics of meat products, while over-reliance on high-salt and phosphate additives may trigger the risk of flocculation in the pre-emulsion system.

[0005] In recent years, the research on using emulsion gels with special structural functions as new animal fat substitutes has been increasing.

[0006] Existing research shows that the emulsion stability can be improved through a polysaccharide matrix or a composite colloid system, but there are still the following technical limitations:

[0007] A systematic optimization method for the synergistic action of multiple factors (such as ratio, temperature, rotation speed) has not been established;

[0008] There is a lack of a quantitative correlation analysis model between the rheological property parameters of the emulsion system and the sensory quality indexes.

[0009] To address the above technical problems, the present invention optimizes the key process parameters of the gelatin pre-emulsion through an orthogonal experimental design, constructs a multi-dimensional index system of oil holding rate, whiteness value and sensory evaluation, and proposes a technical solution for a highly stable emulsion gel that can be prepared on a large scale. Summary of the Invention

[0010] The object of the present invention is to provide a preparation method of a pre-emulsion gel based on gelatin and vegetable oil, which effectively solves the oil layer separation problem in traditional processes and achieves in the development of low-fat meat products: a reduction in saturated fatty acid content of more than 40%; no significant difference in texture characteristics (hardness, elasticity) compared with traditional products; a 15%-20% increase in sensory score; and provides an innovative solution for the industrial production of healthy meat products.

[0011] In order to achieve the above object of the invention, the technical solution adopted by the present invention is as follows:

[0012] A preparation method of a pre-emulsion gel based on gelatin and vegetable oil, comprising the following steps:

[0013] (1) Mix edible gelatin and hot water at a mass ratio of 1:3, and stir at a stirring speed of 200-500 r / min under the condition of 60°C - 100°C until completely dissolved to form a gelatin solution;

[0014] (2) Mix the gelatin solution and vegetable oil at a mass ratio of 1:1, and homogenize and emulsify at a rotation speed of 8000-12000 r / min for 3-7 minutes using a high-speed dispersion homogenizer to obtain the pre-emulsion gel.

[0015] Furthermore, the vegetable oil is selected from at least one of sunflower oil, olive oil, and rapeseed oil.

[0016] Preferably, in the step (1), the dissolution temperature of the gelatin solution is 80°C.

[0017] Preferably, in the step (2), the emulsification time is 5 minutes.

[0018] The present invention also provides the application of the pre-emulsion gel prepared by the above method in meat products. The pre-emulsion gel is used as an animal fat substitute, and the addition amount in meat products is 10% - 25%.

[0019] Furthermore, the addition amount of the pre-emulsion gel in meat products is 15%.

[0020] Furthermore, the meat products are emulsified sausage, frankfurter sausage, or beef ball.

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] By optimizing the preparation process of the gelatin pre-emulsion, the present invention solves the problem of oil layer separation and proves its application advantages in low-fat sausages. Among them, the oil holding rate of the pre-emulsion gel of the present invention is increased to 1969.33 cP, and the whiteness value reaches 82.61%; after the pre-emulsion gel of the present invention is applied to meat products, the saturated fatty acid content of the sausage is reduced by 40%, and the texture characteristics are superior to traditional products, providing a technically feasible solution for the large-scale production of healthy meat products. Description of the Drawings

[0023] Figure 1 is the state diagram of the pre-emulsion gel before centrifugation (from right to left, in groups of three, and the group numbers are T1 - T9 in sequence);

[0024] Figure 2 is the state diagram of the pre-emulsion gel after centrifugation (from right to left, in groups of three, and the group numbers are T1 - T9 in sequence). Detailed Embodiments

[0025] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0026] Example

[0027] 1 Materials and Methods

[0028] 1.1 Experimental Materials

[0029] Gelatin: food-grade gelatin (a company in Henan Province); vegetable oil: first-grade sunflower oil (a grain and oil group in Guangdong Province); the experimental water is deionized water.

[0030] 1.2 Experimental Methods

[0031] A three-factor and three-level orthogonal experimental design (L9(3 4 )) was adopted to investigate the effects of the ratio of gelatin solution to vegetable oil (1:1, 1:2, 1:3), dissolution temperature (60 °C, 80 °C, 100 °C), and emulsification time (3 min, 5 min, 7 min) on the properties of pre-emulsion gels. By measuring viscosity, whiteness, color difference, and sensory scores, the appearance characteristics, microstructure, and rheological characteristics of the emulsion gels were comprehensively evaluated.

[0032] The orthogonal experimental design is shown in Table 1.

[0033] Table 1

[0034] Group Gelatin: Oil (mass ratio) Dissolution temperature (°C) Emulsification time (min) Homogenization speed (r / min) T1 1：1 60 3 8000 T2 1：1 80 5 10000 T3 1：1 100 7 12000 T4 1：2 60 7 12000 T5 1：2 80 3 8000 T6 1：2 100 5 10000 T7 1：3 60 5 10000 T8 1：3 80 7 12000 T9 1：3 100 3 8000

[0035] 1.2.1 Homogenizer Parameters

[0036] An FJ200-SH digital display high-speed dispersion homogenizer was used, with technical parameters: rotation speed range 300 - 23000 r / min, processing capacity 30 - 1500 mL, input power 280 W, and output power 200 W. The rotation speed gradients for the orthogonal experiment were set at 8000 r / min, 10000 r / min, and 12000 r / min.

[0037] 1.2.2 Determination of Oil Retention of Vegetable Oil Oleogel

[0038] Take 2.0 g of the gel sample and place it in a 10 mL centrifuge tube. Symmetrically place it in a centrifuge (Sigma3K15) and centrifuge at 3000 r / min, 4000 r / min, and 5000 r / min for 5 min (25 °C) respectively. Each group was repeated 3 times, and the layering phenomenon was recorded.

[0039] 1.2.3 Viscosity Measurement

[0040] Refer to the method of Qian Feng et al., and use the RVA-TecMaster rapid viscosity analyzer for determination. Take 25 g of the pre-emulsified sample, pour it into an aluminum sample cylinder, insert the stirring paddle into it, ensure that the stirring paddle is immersed below the liquid level of the sample, and fully connect the stirring paddle to the connector. Adjust the rotation direction of the stirring paddle to avoid scratching between the stirring paddle and the sample cylinder during sample measurement. Then, set the parameters such as heating temperature, stirring speed, and heating time change during the determination process through the software of the RVA computer terminal, and the viscosity can be detected. The gelatinization temperature (°C), peak viscosity (cP), trough viscosity (cP), final viscosity (cP), breakdown value (cP), and retrogradation value (cP) can be detected. Conduct 3 parallel tests.

[0041] 1.2.4 Color difference determination

[0042] Use a CR-400 color difference meter to measure the whiteness of the gelatin pre-emulsion gel. Place it at room temperature for 1 h to form a gel before measurement, then cut it into slices about 1 cm thick, and use the CR-400 color difference meter for measurement. Before measurement, calibrate it with a white board, and then measure the L*, a*, and b* values of the sample. Repeat three times and take the average value.

[0043] The L* value represents brightness. The larger the L* value, the greater the brightness.

[0044] The a* value represents the red-green bias of the colored substance. The larger the positive value, the greater the degree of deviation towards red, and the larger the negative value, the greater the degree of deviation towards green.

[0045] The b* value represents the yellow-blue bias of the colored substance. The larger the positive value, the greater the degree of deviation towards yellow, and the larger the negative value, the greater the degree of deviation towards blue.

[0046] Use ΔE (color difference value) to describe the degree of color change of the sample, with the white board color difference of the sample as the reference color difference values L0*, a0*, and b0*. The larger the color difference value, the greater the color change of the sample. The calculation formula (1) is as follows.

[0047]

[0048] 1.2.5 Sensory evaluation

[0049] A panel of 10 food professionals was formed to conduct double-blind scoring according to the criteria in Table 2. The evaluation indicators include odor (30 points), appearance (20 points), stability (20 points), color and luster (15 points), and texture (15 points), with a total score of 100 points.

[0050] Table 2 Sensory evaluation form of vegetable oil gelatin pre-emulsion

[0051]

[0052]

[0053] 2 Results and Analysis

[0054] 2.1 Influence of Homogenizer Emulsification on Gelatin Separation Performance

[0055] From Figure 1 and Figure 2 it can be seen that except for T2 which did not show layering before and after centrifugation, layering occurred in other groups before and after centrifugation. Obviously, it is because the proportion of gelatin solution and vegetable oil is not appropriate, and the balance of the emulsified oil is not adjusted well. It has poor antioxidant properties and a long storage time. From an environmental perspective, layering occurs at room temperature, mainly due to problems with the formula. There are problems with the emulsion system. At this time, the internal substances should be adjusted to reach a certain equilibrium state. Compared with the layering of semi-synthetic products, it is very likely that the base oil is not suitable, or it is very likely that the hydrophilic-lipophilic balance is not adjusted within a reasonable range, and the critical micelle equilibrium is not reached, so the oil and water molecules cannot be stably adsorbed. When the oil phase content is high, the emulsifier content is not enough to completely wrap the oil phase.

[0056] 2.2 Influence of Homogenizer Emulsification on the Viscosity of Gelatin Pre-emulsion

[0057] As can be seen from Table 3, as the vegetable oil in the system continuously increases, the peak viscosity, final viscosity, resilience value, and breakdown value of the vegetable oil pre-emulsion gel continuously decrease, and the shear force becomes worse. Referring to Luo Yu's experimental conclusions, this may be because during the heating process, the network structure of polysaccharides will coat the vegetable oil pre-emulsion gel, inhibiting the diffusion and swelling gelatinization of vegetable oil gel particles, resulting in a decrease in viscosity.

[0058] This study shows that the T2 gel has good physical and chemical properties. To obtain an oil gel emulsion with better stability, vegetable oil is selected as the oil phase, and the stability of emulsions with different oil phase contents is analyzed. The change in the particle size of the emulsion is one of the bases for judging its stability. According to Stokes' law, the smaller the particles, the more stable the emulsion.

[0059] Table 3 Analysis of the Viscosity Characteristics of Gelatin Pre-emulsion

[0060]

[0061]

[0062] 2.3 Analysis of the Whiteness Value of Gelatin Pre-emulsion Whiteness is a major index for evaluating the quality of gelatin pre-emulsion, which reflects the color and quality of gelatin pre-emulsion. The change in the internal structure of gelatin pre-emulsion is a direct reaction of whiteness, and it is closely related to protein composition, protein denaturation, aggregation degree, crosslinking degree, surface optical properties, etc.

[0063] As can be seen from Table 4, the decrease in the whiteness of the gel may be related to the oxidation of proteins during processing, which leads to the cross-linking of muscle proteins and pigment proteins. Of course, the change in the whiteness of the gel may also be caused by the color of the additive itself.

[0064] Table 4 Effects of Different Production Methods on the Color of Vegetable Oil Pre-emulsion Gel

[0065]

[0066] Note: The same uppercase letter superscript in the same column indicates that there is no significant difference between the two (p > 0.05); different lowercase letter superscripts in the same row indicate that there is a significant difference between the two (p < 0.05).

[0067] 2.4 Effects of Different Vegetable Oil Additions on the Stability of Gelatin Pre-emulsion

[0068] Oil-holding capacity represents the ability of the oil gel to retain liquid oil and can reflect the density of the gel structure. From Figure 1 and Figure 2 it can be seen that too high a content of vegetable oil will lead to delamination after emulsification of vegetable oil and gelatin solution, and the decrease in the oil-holding capacity of the oil gel. It may be that the amount of vegetable oil added is too much, and the gelatin molecules are not close enough to attract each other to form a more compact structure, with poor adsorption ability to the oil-water interface, a rapid decrease in the interfacial tension, and the loss of the ability to stabilize oil droplets, resulting in the precipitation of liquid oil. When the ratio of gelatin solution to vegetable oil is 1:2, the oil-holding capacity has decreased significantly, probably because the gelatin has reached saturation in the vegetable oil and its structure is affected when dissolved at a higher temperature and for a longer time. Some studies have shown that the ability of a gelling agent to form a gel is an equilibrium of the solubility of the gelling agent in the solvent. If the gelling agent is too soluble or too insoluble in a given solvent, it will affect the formation of the gel. Therefore, the most suitable ratio of gelatin solution to vegetable oil is 1:1. When the ratio of gelatin solution to vegetable oil is 1:3, the vegetable oil gelatin pre-emulsion has no oil-holding capacity. Therefore, the lower the content of the vegetable oil phase in the emulsion, the smaller the particle size, the more stable the emulsion system, and the lower the creaming index, but the separated oil gel system is unstable.

[0069] 2.5 Effects of Different Gelatin Dissolution Temperatures on the Stability of Gelatin Pre-emulsion

[0070] When the dissolution temperature is 80 °C, the dispersed oil droplets are in the best state, and the emulsifying property of the product is the highest, thus endowing the gel meat products with good texture and taste. According to the research of Li Jihong et al., it is found that curdlan gum can form two types of gels under different heating conditions. Heating its aqueous solution to 55 - 60 °C and then cooling it below 40 °C gives a thermoreversible gel (Thermalreversible curdlan gum, TRC); when the solution is heated above 80 °C, a thermoirreversible gel (Thermalirreversible curdlan gum, TIRC) is obtained. Therefore, based on the above findings, we made a statistical prediction that temperature is one of the most important influencing factors for the thermal-induced gel of vegetable oil gelatin pre-emulsion. Excessive heating temperature will cause gel deterioration. When the temperature increases, the kinetic energy of gel molecules increases, resulting in a decrease in intermolecular hydrogen bonds, and then leading to the destruction of the network structure and the phase transition of the gel. The change in dissolution temperature may be due to the increase in the mass fraction of gelatin, which enhances the non-covalent bond interactions such as hydrogen bonds and π-π stacking between gelatin molecules, making the gel network tighter. A higher temperature is required to break the non-covalent bonds. The change in crystallization temperature also indicates that the higher the mass fraction of gelatin, the tighter the structure of the oleogel, the closer the distance between gelatin molecules, and it is easier to form hydrogen bonds and π-π bonds, and thus it is easier to form oleogel.

[0071] Obviously, the oil-holding capacity of the oleogel with gelatin dissolved at 80 °C is higher than that of the gelatin dissolved at 60 °C and 100 °C, indicating that the dissolution temperature of 80 °C can make the structure of the oleogel tighter, thus showing a higher oil-holding capacity. And at 80 °C, due to the slower movement of gelatin molecules, the three-dimensional network structure formed by their aggregation is not easily changed, the gel crystallization structure is stable, and the liquid oil can be effectively encapsulated, resulting in an increase in the oil-holding capacity of the vegetable oil pre-emulsion gel.

[0072] 2.6 Influence of different homogenizer speeds on the stability of gelatin pre-emulsion

[0073] Through experiments, it is found that when the emulsification speed is 12000 r / min or 8000 r / min, the hardness of the gel oil decreases slightly, and the increasing trend of the oil-holding rate slows down. This may be because although a higher stirring rate promotes the formation of the oil gel, to a certain extent, the relaxation degree of the oil system is also affected by the interaction between the carbon chains of the microstructure. Therefore, a higher emulsification speed may affect the cross-linking of adjacent carbon chain structures, thus affecting the quality of the gel oil. Considering that too high an emulsification speed leads to high energy consumption, a suitable stirring speed of 10000 r / min is selected, at which the oil-holding rate of the gel oil is the highest.

[0074] 2.7 Influence of different emulsification times on the stability of gelatin pre-emulsion

[0075] With the increase of gelation time, the gel strength, breaking force and breaking distance all showed a trend of increasing first, then decreasing and then increasing, and reached the maximum value at 5 min. At this time, the gel strength was the highest, the breaking force was the lowest, and the breaking distance was the closest. The research of Liu Haimei et al. showed that for silver carp surimi added with 10 U / g TGase, the gel strength was the highest when the gelation time was 2.0 h, which was 544.15 g / cm 2 . As can be seen from the figure, the oil holding rate was the largest when the gelation time was 5 min, but there was no significant difference between different groups (P>0.05), which indicated that the gelation time had no significant effect on water holding capacity.

[0076] 3 Conclusions

[0077] Good gel properties can improve the water and oil holding rate of products, and at the same time better disperse oil droplets, improve the emulsification of meat products such as sausages, thus endowing gel meat products with good texture and taste.

[0078] From the analysis and summary of the results of the orthogonal experiment, the following conclusions were drawn: By analyzing the viscosity value, whiteness value, color difference and sensory evaluation of gelatin, the best ratio of vegetable oil gelatin pre-emulsion was obtained for the appearance, microstructure and rheological properties of the emulsion gel. The ratio of gelatin boiling water mixture to vegetable oil was 1:1, the rotation speed of the emulsifier was 10,000 r / min, and the emulsification time of the emulsifier was 5 min. The gel surface of the emulsion gel system constructed by completely dissolving gelatin and boiling water at 80 °C was more uniform, showing the texture of yogurt, with the highest oil holding rate, the strongest and most stable dense rheological viscoelasticity.

[0079] It can be seen from this that the primary and secondary order of factors affecting the oil holding rate of vegetable oil gel is: the ratio of gelatin boiling water mixture to vegetable oil > gelatin dissolution temperature > emulsification time > emulsification rotation speed.

[0080] The viscosity of the vegetable oil pre-emulsion gel product prepared under these conditions was 1969.33 cP, the whiteness value was 82.61%, and it was known from the sensory evaluation that the oil holding rate was the highest at this time.

[0081] Gelatin forms a kind of thermoreversible gel. Usually, the main force stabilizing the thermoreversible gel network structure is hydrogen bond, and the formation and destruction of hydrogen bond depend on temperature. Heating is one of the main factors affecting the formation process of vegetable oil pre-emulsion gel. The thermally induced gel properties of vegetable oil pre-emulsion gel are crucial for the texture and sensory quality of meat products. Appropriate temperature can enhance the gel network structure and finally improve the gel properties.

[0082] By optimizing the preparation process of the gelatin pre-emulsion, the present invention solves the problem of oil layer separation and demonstrates its application advantages in low-fat sausages. Among them, the oil holding rate of the pre-emulsion gel of the present invention is increased to 1969.33 cP, and the whiteness value reaches 82.61%; after the pre-emulsion gel of the present invention is applied to meat products, the saturated fatty acid content of the sausage is reduced by 40%, and the texture characteristics are superior to those of traditional products, providing a technically scalable production solution for the development of healthy meat products.

[0083] The above description is a detailed description of the preferred and feasible embodiments of the present invention, but the embodiments are not intended to limit the scope of the patent application of the present invention. Any equivalent changes or modifications made under the technical spirit disclosed by the present invention shall fall within the scope of the patent covered by the present invention.

Claims

1. A method for preparing a pre-emulsified gel based on gelatin and vegetable oil, characterized in that: The following steps are involved: (1) mixing edible gelatin and hot water in a mass ratio of 1:3, stirring at 60°C-100°C and at a stirring speed of 200-500 r / min until completely dissolved to form a gelatin solution; (2) The gelatin solution and the vegetable oil are mixed in a mass ratio of 1:1, and homogenized and emulsified for 3-7 minutes at a speed of 8000-12000 r / min using a high-speed dispersing homogenizer to obtain the pre-emulsified gel.

2. The preparation method according to claim 1, characterized in that: The vegetable oil is selected from at least one of sunflower oil, olive oil and rapeseed oil.

3. The preparation method according to claim 1, characterized in that: In the step (1), the dissolving temperature of the gelatin solution is 80°C.

4. The preparation method according to claim 1, characterized in that: The emulsification time in step (2) is 5 minutes.

5. Use of the pre-emulsified gel prepared by the method according to any one of claims 1 to 4 in meat products, characterized in that: The pre-emulsion gel is used as an animal fat substitute and is added in a meat product in an amount of 10%-25%.

6. The use according to claim 5, characterized in that: The pre-emulsion gel is added in an amount of 15% in the meat product.

7. The use according to claim 5, characterized in that: The meat product is emulsified sausage, frankfurter sausage or beef meatball.

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