Preparation method of high-amylose corn starch emulsion gel with high gel strength

Abstract

The invention discloses a method for preparing emulsion gel from high-amylose corn starch, and relates to the technical field of emulsion gel preparation. The OSA modified product of the high-amylose corn starch is applied to the emulsion gel, the oil holding capacity and the stability of the emulsion gel are synergistically improved by utilizing the high amylose content and the amphipathy of the high-amylose corn starch, and the high-amylose corn starch has very good gel strength. Through combination of microwave-assisted rapid gelatinization and cold-induced gelatinization, more uniform starch particle expansion and gelatinization are realized by using rapid penetrability of microwaves and a molecular friction heat effect, energy consumption is reduced, and molecular chain degradation caused by long-time heating is avoided; the cold retrogradation characteristic (amylose recrystallization) of high amylose is utilized, and a stable three-dimensional space network gel structure is spontaneously formed in the low-temperature refrigeration process. The invention establishes a high-efficiency and low-energy-consumption emulsion gel preparation method, the process is milder and simpler, and heat-sensitive nutrients can be better retained.

Description

Technical Field

[0001] The present invention relates to the technical field of emulsion gel preparation, and specifically to a method for preparing emulsion gel using high amylose corn starch. Background Art

[0002] As a novel colloidal dispersion system, the construction of emulsion gels is usually based on the emulsification of the water phase and the oil phase, and then the emulsion is structured through mechanisms such as thermal induction, enzymatic catalysis or ionic crosslinking to finally form a gel matrix with a three-dimensional network skeleton. This system exhibits unique application potential in the field of fat substitutes by integrating the interfacial stability characteristics of the emulsion and the continuous phase support ability of the gel. However, traditional emulsion gel systems mostly rely on chemically synthesized surfactants (such as Tween, Span, etc.) to achieve emulsion stabilization. Such artificial synthetic substances pose a risk of causing food safety concerns. Therefore, emulsion gels based on natural biopolymers such as polysaccharides and proteins have gradually become the focus of research in recent years. However, to improve the mechanical strength of the gel, most current studies prepare high internal phase emulsion gels. However, the high oil phase content (≥75%) conflicts with the low-fat and healthy diet concept advocated by modern dietary guidelines. In systems with a low oil phase ratio, researchers usually need to introduce exogenous colloids such as gelatin, carrageenan or pectin to compensate for the insufficient gel strength, or rely on high-temperature treatment, Ca 2 + / Mg2+ ionic crosslinking means to achieve gelation. Such methods not only complicate the formulation and increase production costs, but also go against the consumption trend of "clean label" in the food industry.

[0003] As a novel starch resource, high amylose corn starch has the advantages of safety, non-toxicity, renewable and degradable. Its amylose content usually exceeds 50%. During the heating process, the helical straight-chain molecules in the starch granules will gradually dissolve out. As the temperature decreases, these dissolved starch molecules will rearrange and combine to form a stable and ordered gel structure. Based on this property, high amylose corn starch is considered an ideal emulsion gel material. The emulsion gel prepared from it has the advantages of good stability, low oil phase volume, simple preparation process, high gel strength and environmental friendliness.

[0004] Nevertheless, the research on preparing emulsion gels with high amylose corn starch as the raw material in the food field is still in its infancy, and relevant research is relatively scarce. This is mainly because the unmodified high amylose starch granules have low adsorption efficiency at the oil-water interface due to their strong hydrophilicity on the surface and dense crystal structure, and it is difficult to effectively reduce the interfacial tension, resulting in the emulsion gel stability not meeting the requirements of commercial applications. Summary of the Invention

[0005] The object of the present invention is to provide a method for preparing emulsion gels using high amylose corn starch as a raw material, so as to solve the problems of poor stability of the existing emulsion gel system, low gel strength, high oil phase content being unfavorable to health, complex preparation process, complex formula and insufficient cleanliness and safety.

[0006] To achieve the above object, the present invention provides the following technical solution. A preparation method of a high amylose corn starch emulsion gel with high gel strength includes the following steps:

[0007] (1) Water and high amylose corn starch are mixed to form a 30-40 wt% suspension, and octenyl succinic anhydride (OSA) is added for reaction while maintaining the pH at 8.3. The addition amount of OSA is 2-9% of the dry starch mass. Then the pH is adjusted to 6.5, and it is washed alternately with ethanol and water. After centrifugation, the precipitate is dried, crushed, and sieved to obtain OSA starch;

[0008] The oil-water interface of the particle-stabilized emulsion needs to have an appropriate hydrophilic-hydrophobic balance property. Due to the rich hydroxyl groups on the surface of high amylose corn starch particles and the high proportion of internal crystalline regions, they show strong hydrophilicity and low hydrophobicity, resulting in insufficient adsorption efficiency at the oil-water interface and difficulty in forming a stable emulsion system. To solve this problem, the present invention esterifies the native starch with octenyl succinic anhydride (OSA): through the esterification reaction, a hydrophobic octenyl long chain and a hydrophilic carboxylic acid group are introduced into the starch molecular chain, endowing the modified starch with amphiphilicity.

[0009] (2) The OSA starch prepared in step (1) is formulated into a 2-15 wt% suspension and heated in a microwave reactor at 200W-800W for 1-5 min and then cooled for 0.2-2 h to room temperature to obtain a starch solution;

[0010] The starch particles treated only by OSA esterification are still limited by their dense crystal structure, and the molecular chains are difficult to fully stretch to cover the interface. Existing technologies usually further treat with enzymatic hydrolysis or heat gelatinization, but there are significant defects: enzymatic hydrolysis (such as hydrolysis by α-amylase) will uncontrollably cut the starch chain, resulting in a wider molecular weight distribution and reducing the continuity of the gel network; traditional water bath gelatinization requires long-time high-temperature treatment (≥95°C for 30 minutes), which not only has high energy consumption but also causes significant degradation of the amylose molecular chain and destroys the long-chain entanglement ability required for subsequent cold-induced gelation.

[0011] The present invention innovatively adopts microwave-assisted rapid gelatinization technology: utilizing the penetrating heating property of microwaves to promote the instantaneous vaporization and expansion of water inside the starch particles, while reducing the degradation rate of amylose molecular chains. This step lays a structural foundation for the molecular movement and entanglement in the subsequent low-temperature standing stage.

[0012] (3) The starch solution prepared in step (2) is mixed with soybean oil and then subjected to high-speed shear homogenization treatment to obtain an emulsion;

[0013] The oil phase droplet size is reduced by high-speed shear homogenization, and the OSA-modified starch rapidly adsorbs on the interface of the newly formed droplets, forming a dense interfacial film to prevent the gel network from loosening due to overly large droplets.

[0014] (4) Transfer the emulsion prepared in step (3) to a low-temperature environment and let it stand to obtain an emulsion gel.

[0015] During the low-temperature storage stage, the linear molecular chains of high amylose starch undergo orientation rearrangement due to their high mobility, and through hydrophobic association and hydrogen bonding, they cooperate to construct a three-dimensional continuous network. As time goes by, the molecular chains continuously adjust to the thermodynamic equilibrium state, forming an emulsion gel with good oil-holding capacity.

[0016] Compared with ordinary corn starch (amylopectin content > 70%), its highly branched structure results in high molecular chain rigidity and low entanglement efficiency, and it is difficult to form a strong emulsion gel structure even after OSA modification under the condition of low oil phase concentration. While the amylose content of high amylose corn starch is usually above 50%, and the linear molecules have strong mobility and are prone to entanglement when reaching a certain concentration, making it a good material for forming gels.

[0017] In one embodiment, step (1) is specifically as follows: Mix high amylose corn starch with water to prepare a 35 wt% starch milk, add octenyl succinic anhydride dropwise within 2 h, and the amount of octenyl succinic anhydride accounts for 5 wt% of the starch dry basis in the starch milk. Continue the reaction for 2 h, maintain the pH value at 8.3 during the reaction, adjust the pH value to 6.5 after the reaction ends, wash it alternately with ethanol and deionized water 4 times, centrifuge at 4000 rpm for 10 min, crush and sieve the dried precipitate to obtain OSA starch.

[0018] In one embodiment, step (2) is specifically as follows: Prepare an 8 wt% starch milk with OSA starch, place it in a microwave reactor, heat it at 800 W for 5 min, and wait for it to cool to room temperature after heating, and use it as the water phase of the emulsion.

[0019] In one embodiment, in step (3), the mixing mass ratio of the starch solution and the oil phase is 100:20 - 50, and the high-speed shear homogenization treatment in step (3) means shearing at 8000 - 18000 r / min for 2 - 8 min.

[0020] In one embodiment, in step (4), the low-temperature environment refers to -20 - 10 °C, and the standing time in step (4) is 0.5 - 5 d.

[0021] The second object of the present invention is to provide a high amylose corn starch emulsion gel with high gel strength prepared according to the above method.

[0022] The third object of the present invention is to provide an application of a high amylose corn starch emulsion gel with high gel strength in the production fields such as meat products, baked products, dairy products, etc.

[0023] Compared with the existing technologies, the present invention has the following advantages and beneficial effects:

[0024] (1) Material and formula innovation: The present invention first applies the OSA-modified product of high amylose corn starch to emulsion gels, and utilizes its high amylose content and amphiphilicity to synergistically improve the oil-holding capacity and stability characteristics of the emulsion gels, with good gel strength. The formula only relies on OSA starch as the emulsifier and gel matrix, without synthetic emulsifiers (such as monoglyceride) or colloid additives (such as exogenous colloids like gelatin, pectin, etc.), meeting the "clean label" trend. The present invention expands new development space for the scientific research exploration and practical application of high amylose corn starch.

[0025] (2) Process innovation: By combining microwave-assisted rapid gelatinization and cold-induced gelation, an efficient and low-energy consumption method for preparing emulsion gels is established. Traditional starch gelatinization requires long-time water bath heating, while the present invention uses short-time microwave treatment. Utilizing the rapid penetration and molecular friction heat effect of microwaves, more uniform swelling and gelatinization of starch granules are achieved, reducing energy consumption and avoiding the degradation of molecular chains caused by long-time heating. Utilizing the cold retrogradation property of high amylose starch (recrystallization of amylose), a stable three-dimensional network gel structure is spontaneously formed during low-temperature refrigeration. Compared with thermally induced gels and ion-induced gels, the present invention realizes gelation through physical cold treatment, with a milder and simpler process, and can better retain heat-sensitive nutrients.

[0026] (3) Application value: The all-starch-based emulsion gel developed by the present invention is superior to traditional emulsion gels in texture simulation and clean label, meets the requirements of green and sustainable development, and shows extremely broad application potential. Description of the Drawings

[0027] Figure 1 Are the appearance diagrams of three examples and three comparative examples;

[0028] Figure 2 Are the graphs of the relationship between the storage modulus and loss modulus of three examples and the angular frequency;

[0029] Figure 3 Are the graphs of the relationship between the storage modulus and loss modulus of three comparative examples and the angular frequency;

[0030] Figure 4 Are the gel strengths of three examples and three comparative examples. Detailed Embodiments

[0031] Example 1

[0032] S1. Material preparation: Prepare high amylose corn starch, deionized water and soybean oil.

[0033] S2. Preparation of OSA starch: Mix high amylose corn starch with water to form a 35% (m / m) starch milk. Drop the octenyl succinic anhydride reagent (the dosage accounts for 5% of the starch dry basis) into the starch milk within 2 h, and continue to react for 2 h. During the reaction, the pH value is maintained at 8.3. Then adjust the pH value to 6.5, wash it alternately with ethanol and deionized water 4 times, centrifuge at 4000 rpm for 10 min, crush and sieve the dried precipitate to obtain OSA starch.

[0034] S3. Preparation of starch solution: Prepare an 8% (m / m) starch milk with OSA starch, place it in a microwave reactor, heat it at 800 W for 5 min, and wait for it to cool to room temperature after heating, which is used as the water phase of the emulsion.

[0035] S4. Preparation of emulsion gel: Use soybean oil as the oil phase of the emulsion, mix the water and oil phases in a ratio of 6:4 (m / m), and shear with a high-speed shear machine at 18000 r / min for 5 min to obtain an emulsion. Then place the emulsion in a 4 °C environment and refrigerate it for 3 d for gelation to obtain an emulsion gel.

[0036] Example 2

[0037] The difference from Example 1 is:

[0038] S3. Preparation of starch solution: Prepare a 4% (m / m) starch milk with OSA starch.

[0039] Example 3

[0040] The difference from Example 1 is:

[0041] S3. Preparation of starch solution: Prepare a 12% (m / m) starch milk with OSA starch.

[0042] S4. Preparation of emulsion gel: Mix the water and oil phases in a ratio of 8:2 (m / m).

[0043] Comparative Example 1

[0044] The difference from Example 1 is:

[0045] S1. Material preparation: Prepare ordinary corn starch, deionized water and soybean oil.

[0046] Comparative Example 2

[0047] The difference from Example 1 is:

[0048] S3. Preparation of starch solution: Prepare an 8% (m / m) starch milk with OSA starch, place it in a boiling water bath and heat for 5 min. After heating, let it cool to room temperature and use it as the aqueous phase of the emulsion.

[0049] Comparative Example 3

[0050] The difference from Example 1 is as follows:

[0051] S3. Preparation of starch solution: Prepare a 1% (m / m) starch milk with OSA starch.

[0052] Figure 1 Figs. are the appearance diagrams of three examples and three comparative examples.

[0053] As Figure 1 shown, the emulsion gels prepared in Examples 1-3 all maintained a good shape after demolding and had good self-supporting ability, indicating that their gel structures were strong. However, the emulsion gels prepared in Comparative Examples 1-3 did not form, collapsed immediately after demolding, and had weak gel structures.

[0054] Figure 2 And Figure 3 are the diagrams showing the relationships between the storage modulus and loss modulus and angular frequency of three examples and three comparative examples respectively.

[0055] As Figure 2 And Figure 3 shown, the storage modulus G' of the emulsion gels prepared in Examples 1-3 was much higher than their corresponding loss modulus G", and the two moduli were hardly affected by the shear frequency, indicating that the emulsion formed a highly elastic gel network structure. However, for the emulsion gels prepared in Comparative Examples 1-3, the difference between G' and G" was not significant, indicating weak elasticity, poor solid-like properties, and weak internal gel structures.

[0056] Figure 4 Gel strengths of three examples and three comparative examples.

[0057] As Figure 4As shown, the gel strengths of the emulsion gels prepared in Examples 1-3 far exceed those of the emulsion gels prepared in Comparative Examples 1-3. The former are maintained at 124.2-147.5 g, while the latter are less than 5.0 g, and the former is nearly 30 times greater than the latter. First, the gel strength of Comparative Example 1 is the lowest, less than 1 g, indicating that using high amylose corn starch as a raw material can significantly improve the gel structure strength, while ordinary corn starch cannot. From the perspective of starch structure, this is because the content of long-chain amylose in high amylose corn starch is high. Compared with amylopectin, amylose has stronger entanglement ability, strong molecular mobility, can fully move and adjust the molecular configuration, and entangle with other molecules; while amylopectin has poor molecular mobility and it is not easy for molecules to entangle with each other, resulting in a weak gel structure strength. Secondly, the gel structure of the emulsion gel prepared by the traditional water bath heating method in Comparative Example 2 is also very low, far lower than each of the examples using microwave treatment. This is because high amylose corn starch granules are a semi-crystalline structure, and starch molecules are arranged in the granules in a certain order. External energy is required to overcome the intermolecular interaction forces, causing the granules to expand and the molecular chains to stretch out, providing the possibility of movement and entanglement, which is a prerequisite for gelation. Finally, Comparative Example 3 uses a starch concentration of 1%, and its gel structure is still relatively low. The reason is that the prerequisite for the mutual overlap and entanglement of polymer macromolecules (here referring to starch molecules) is to reach a certain concentration, and a concentration of 1% is too low to meet this condition.

[0058] The above are only the embodiments of the present invention, and do not limit the patent scope of the present invention accordingly. Any equivalent transformation made using the content of the specification of the present invention, directly or indirectly applied in related technical fields, shall be equally included in the patent protection scope of the present invention.

Claims

1. A method for preparing a high-amylose corn starch emulsion gel with high gel strength, characterized in that: The following steps are involved: (1) mixing water and high-amylose corn starch to form a 30-40 wt% suspension, adding octenyl succinic anhydride OSA to react and maintaining the pH at 8.3, wherein the amount of OSA added is 2-9% of the dry weight of the starch, and then adjusting the pH to 6.5, washing with ethanol and water alternately, drying, crushing, and sieving the precipitate after centrifugation to obtain OSA starch; (2) preparing a 2-15 wt% suspension of the OSA starch obtained in step (1), heating the suspension at 200 W to 800 W in a microwave reactor for 1-5 min, and then cooling the suspension to room temperature for 0.2 to 2 h to obtain a starch solution; (3) mixing the starch solution obtained in step (2) with soybean oil and subjecting the mixture to high-speed shear homogenization to obtain an emulsion; (4) The emulsion obtained in step (3) is transferred to a low temperature environment and allowed to stand to obtain an emulsion gel.

2. The method for preparing a high-amylose corn starch emulsion gel with high gel strength according to claim 1, characterized in that: The step (1) specifically comprises: mixing high-amylose corn starch with water to prepare a 35 wt% starch milk, adding octenyl succinic anhydride dropwise within 2 hours, wherein the amount of octenyl succinic anhydride is 5 wt% of the starch dry basis to the starch milk, continuing the reaction for 2 hours, maintaining the pH value at 8.3 during the reaction, adjusting the pH value to 6.5 after the reaction, washing with ethanol and deionized water alternately for 4 times, centrifuging at 4000 rpm for 10 minutes, and crushing and sieving the dried precipitate to obtain OSA starch.

3. The method for preparing a high-amylose corn starch emulsion gel with high gel strength according to claim 1, characterized in that: The step (2) specifically comprises: preparing 8 wt % starch emulsion with OSA starch, placing the emulsion in a microwave reactor, heating it at 800 W for 5 min, and cooling it to room temperature after heating to use it as the aqueous phase of the emulsion.

4. The method for preparing a high-amylose corn starch emulsion gel with high gel strength according to claim 1, characterized in that: In the step (3), the starch liquid and the oil phase are mixed in a mass ratio of 100:20-50, and the high-speed shear homogenization treatment in the step (3) refers to shearing at 8000-18000 r / min for 2-8 min.

5. The method for preparing a high-amylose corn starch emulsion gel with high gel strength according to claim 1, characterized in that: The low temperature environment in step (4) refers to -20 to 10°C, and the standing time in step (4) is 0.5 to 5 days.

6. A high gel strength, high amylose corn starch emulsion gel with low oil content and high gel strength, characterized in that: The preparation is obtained by the preparation method according to any one of claims 1 to 5.

7. Use of the high-amylose corn starch emulsion gel with high gel strength as claimed in claim 6 in the production fields of meat products, baked products, dairy products, etc.

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