Pre-fried food coating powder and use thereof

Abstract

The application provides a pre-fried food coating powder and application thereof, raw materials of the pre-fried food coating powder include a basic component and a functional component; the basic component includes low-gluten wheat flour, cassava modified starch, corn starch, pre-gelatinized starch and sodium bicarbonate; the functional component includes zein and chickpea protein isolate. The application uses zein and chickpea protein isolate as the functional component by compounding, and the two components produce a significant synergistic interface enhancement effect in the process of frying. Zein is rich in hydrophobic amino acids, can form a dense hydrophobic micro-region network in the coating layer, and effectively blocks the internal water vapor from permeating outward during microwave reheating; chickpea protein isolate has good hydrophilicity and flexibility, can form hydrogen bonds and electrostatic adsorption with the polar groups on the surface of food materials, and enhances the initial anchoring force between the coating layer and the food materials.

Description

Technical Field

[0001] This invention relates to the field of food processing technology, and more specifically to a pre-fried food coating powder and its application. Background Technology

[0002] Current coating technologies for pre-fried foods primarily rely on physical-mechanical interlocking, such as creating a rough, tiger-skin-like texture on the food surface or increasing the coating thickness to improve adhesion. However, this method only partially solves the adhesion problem and has limited effectiveness for smooth-surfaced foods such as fish, shrimp, and eggs. During microwave reheating, the shear stress generated by the outward seepage of moisture from the food's interior causes the coating to peel off from the food interface (i.e., delamination). Current technologies cannot achieve a stable bond between the coating and the food interface at the molecular level, resulting in decreased crispness and a higher average separation rate in reheated foods.

[0003] Existing pre-fried food preparation processes include pre-coating with flour, battering, coating with cornstarch, and pre-frying. Common improvement methods to address coating peeling typically involve increasing the thickness of the flour coating, increasing the amount of batter, or using a secondary battering process—all physical enhancements. These methods cannot effectively prevent peeling under microwave reheating conditions, nor can they guarantee a stable flour-coated interface on all types of food surfaces. Furthermore, existing flour coating technologies do not fully utilize the role of functional components such as proteins in interfacial adhesion and structure formation, lacking solutions for achieving synergistic bonding between the flour coating and the food interface at the microscopic molecular level, thus hindering quality improvement in microwave-reheated pre-fried foods.

[0004] Therefore, existing technologies need further development. Summary of the Invention

[0005] To address the problems of coating peeling and insufficient interfacial bonding in pre-fried foods during microwave reheating in existing technologies, this application provides a pre-fried food coating and its application. By utilizing the synergistic effect of specific functional components during frying and reheating, a strong bond between the coating layer and the food interface and excellent water-resistant properties are achieved.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A pre-fried food coating, the raw materials of which include basic components and functional components; The basic components include low-gluten wheat flour, modified cassava starch, corn starch, pregelatinized starch, and sodium bicarbonate. The functional components include zein and chickpea protein isolate.

[0007] Furthermore, the mass ratio of zein to chickpea protein isolate is 6-10:4-8.

[0008] Further, by weight, the raw materials include: 35-45 parts low-gluten wheat flour, 15-20 parts modified cassava starch, 5-10 parts corn starch, 3-6 parts pregelatinized starch, 1-2 parts sodium bicarbonate, 6-10 parts zein, and 4-8 parts chickpea protein isolate.

[0009] Furthermore, by weight, the functional components also include 2-4 parts of sunflower seed oil.

[0010] Furthermore, the functional components include microcapsules made from zein, chickpea protein isolate, and sunflower seed oil, with the sunflower seed oil serving as the core material and the zein and chickpea protein isolate serving as the shell material.

[0011] Furthermore, the microcapsules are prepared by dispersing sunflower seed oil, zein and chickpea protein isolate in an aqueous solution, homogenizing under high pressure of 30MPa-50MPa to form an emulsion, and spray drying the resulting emulsion to obtain microcapsules.

[0012] Furthermore, when sunflower seed oil, zein, and chickpea protein isolate were co-dispersed in an aqueous solution, α-cyclodextrin was added as a co-solvent.

[0013] The amount of α-cyclodextrin added is 0.3-0.8 parts.

[0014] Furthermore, the chickpea protein isolate is a heat-modified chickpea protein isolate.

[0015] Furthermore, the method for preparing the heat-modified chickpea protein isolate is to disperse chickpea protein isolate in an alkaline buffer solution, heat it, and then cool it in an ice bath to obtain the heat-modified chickpea protein isolate.

[0016] Furthermore, the alkaline buffer solution has a pH value of 9.0-9.5, and is heated by water bath heating at a temperature of 85-95°C for 8-15 minutes.

[0017] The present invention also provides an application of the above-mentioned pre-fried food coating powder, characterized in that the pre-fried food coating powder is used in the pre-coating step of the pre-fried food preparation process.

[0018] Due to the adoption of the above technical solutions, the beneficial technical effects of the present invention are as follows: 1. This invention uses a combination of zein and chickpea protein isolate as functional components. During frying, the two components exhibit a significant synergistic interface enhancement effect. Zein, rich in hydrophobic amino acids, forms a dense hydrophobic micronetwork within the coating layer, effectively preventing internal moisture penetration during microwave reheating. Chickpea protein isolate possesses excellent hydrophilicity and flexibility, enabling it to form hydrogen bonds and electrostatic adsorption with polar groups on the food surface, enhancing the initial anchoring force between the coating layer and the food. Under thermal induction, the two components undergo interpenetrating network synthesis at the molecular level, forming a hydrophobic-hydrophilic dual-network structure. This prevents the brittleness and cracking of pure zein membranes while compensating for the insufficient water-blocking properties of pure chickpea protein isolate.

[0019] 2. This invention further incorporates zein, chickpea protein isolate, and sunflower seed oil into microcapsules, achieving both spatial synergy and thermal triggering dual responsiveness among the three components. In this microcapsule structure, sunflower seed oil serves as the core material, encapsulated by a composite wall material composed of zein and chickpea protein isolate during spray drying. When the food is subsequently pre-fried, the microcapsules rupture due to thermal triggering, releasing the sunflower seed oil and assisting the zein and chickpea protein isolate in rapidly unfolding and rearranging at the oil-water interface, forming a bilayer synergistic membrane dominated by a hydrophobic outer layer of zein and a hydrophilic inner layer dominated by chickpea protein isolate. This structure endows the coating layer with excellent gradient barrier properties: the outer hydrophobic membrane effectively blocks water vapor penetration, while the inner hydrophilic membrane forms a strong chemical anchor with the food surface. Simultaneously, the appropriate release of sunflower seed oil can regulate the oil distribution of the coating layer, preventing excessive oil absorption or over-drying. Furthermore, the microencapsulation of these three components significantly improves the dispersion uniformity and storage stability of zein in the dry powder.

[0020] 3. This invention enhances the functional activity of chickpea protein isolate in breading systems through thermal modification treatment involving heating in an alkaline buffer solution followed by ice bath cooling. Under conditions of pH 9.0-9.5 and water bath heating at 85-95℃ for 8-15 minutes, the secondary structures of globulin and albumin in chickpea protein isolate are effectively unfolded, exposing more hydrophobic groups and inner functional groups. Simultaneously, the molecules self-assemble to form soluble nanoaggregates of 20-200 nm. Subsequent rapid ice bath cooling inhibits excessive protein aggregation and stabilizes the modified active conformation. Detailed Implementation

[0021] To enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Based on the embodiments in this application, other similar embodiments obtained by those skilled in the art without creative effort should all fall within the scope of protection of this application.

[0022] Unless otherwise specified in the examples, standard conditions or conditions recommended by the manufacturer should be followed. Reagents or instruments whose manufacturers are not specified are all commercially available products. Unless otherwise specified, all reagents used in the examples are commercially available.

[0023] This invention provides a pre-fried food coating, the raw materials of which include basic components and functional components. Specifically, the basic components constitute the skeletal system of the coating, while the functional components act as core active ingredients to enhance the interface. The basic components include low-gluten wheat flour, modified tapioca starch, corn starch, pregelatinized starch, and sodium bicarbonate. Low-gluten wheat flour, as the main film-forming substance, provides basic adhesion; modified tapioca starch and corn starch are used to improve the crispy texture and gelatinization properties of the coating; pregelatinized starch helps to increase the initial adhesion speed of the coating to the food surface; sodium bicarbonate, as a leavening agent, generates gas during frying to make the coating fluffy. The functional components include zein and chickpea protein isolate.

[0024] The core innovation of this invention lies in utilizing the specific complexation relationship between zein and chickpea protein isolate to construct a unique hydrophobic-hydrophilic network structure. At the microscopic level, zein is rich in nonpolar amino acids and possesses extremely strong hydrophobicity. During frying, zein denatures and aggregates upon heating, forming a dense network of hydrophobic microregions within the coating layer. This hydrophobic network acts as a waterproof barrier, effectively preventing moisture from penetrating the food during microwave reheating and preventing moisture buildup at the interface that could cause peeling stress. However, while zein alone offers good water resistance, its film-forming properties are hard and brittle, making it prone to cracking during subsequent temperature changes from freezing to reheating of pre-fried foods, leading to coating detachment.

[0025] Complementing this, chickpea protein isolate possesses excellent hydrophilicity and flexibility. Its molecular chains are distributed with numerous polar groups, enabling it to form strong hydrogen bonds and electrostatic adsorption with polar molecules such as proteins on the surface of food, thus creating a strong "anchor point" between the breading layer and the food interface. However, if chickpea protein isolate is used alone, although the interfacial adhesion is strong, its hydrophilic properties mean it cannot effectively prevent moisture penetration. Under microwave reheating conditions, moisture will still penetrate the coating, leading to a decrease in crispness.

[0026] This invention combines the two ingredients to produce an unexpected synergistic effect. Under pre-frying conditions, hydrophobic zein and hydrophilic chickpea protein isolate undergo molecular-level interpenetration and cross-linking, forming an interpenetrating network structure. This dual-network structure retains the highly efficient water-blocking properties of zein while introducing the flexibility and strong adhesion of chickpea protein isolate. The flexible network formed by chickpea protein isolate buffers the brittleness of the zein network and prevents the propagation of microcracks; simultaneously, the hydrophobic network of zein protects chickpea protein isolate from excessive moisture erosion. Both are indispensable, working together to achieve an interface enhancement effect of internal anchoring and external barrier, fundamentally solving the problem of peeling pre-fried foods during microwave reheating.

[0027] Zein and chickpea protein isolate fundamentally solve the "shelling" problem of coating detaching from the food surface during microwave reheating. Specifically, Zein is rich in hydrophobic amino acids (>50%), which can form a dense, continuous hydrophobic film under pre-frying heating, acting as an effective barrier to prevent internal moisture from penetrating outwards. However, when Zein forms a film alone, it has poor flexibility and weak affinity with polar groups on the food surface, making it prone to cracking due to internal stress or moisture impact. Chickpea protein isolate, on the other hand, is rich in hydrophilic amino acids and polar groups (-COOH, -NH2, etc.). On the one hand, it can form a dense hydrogen bond network and electrostatic adsorption with proteins / glycoproteins on the food surface, providing strong initial anchoring force. On the other hand, its flexible hydrophilic network can fill the pores of the Zein hydrophobic framework, forming an interpenetrating double network structure. Zein contributes a rigid water-blocking framework, while chickpea protein isolate contributes flexibility and interfacial affinity. The two are tightly bound at the molecular level through hydrophobic interactions and non-covalent bonds such as hydrogen bonds. During microwave reheating, the Zein hydrophobic membrane blocks most of the water vapor from diffusing to the interface. The small amount of water vapor that penetrates is buffered and absorbed by the high water-holding network of chickpea protein isolate. At the same time, chickpea protein isolate firmly anchors the Zein membrane to the surface of the food, dissipating interfacial shear stress and preventing membrane peeling caused by stress concentration.

[0028] It is important to emphasize that the combination of zein and chickpea protein isolate is not an arbitrary pairing of hydrophobic and hydrophilic proteins, but a specific combination determined after extensive experimental screening. Other common hydrophobic proteins (such as casein and rice protein), while possessing some hydrophobic properties, cannot spontaneously aggregate to form a dense and continuous network of hydrophobic microregions under frying conditions like zein. Casein tends to form a loose gel structure rather than a dense film under heat induction, resulting in insufficient water-blocking density; rice protein exhibits greater film-forming brittleness and is prone to cracking during freeze-thaw cycles. Similarly, other common hydrophilic proteins (such as whey protein and gelatin), while possessing hydrophilic properties, lack the molecular flexibility and ability to form multiple hydrogen bonds and electrostatic adsorption with polar groups on food surfaces unique to chickpea protein isolate. Whey protein is prone to excessive denaturation under high-temperature frying conditions, forming a hard gel and failing to provide flexible cushioning; gelatin, while flexible, has poor thermal stability and melts away at pre-frying temperatures, failing to maintain an interfacial anchoring network. Only the specific combination of zein and chickpea protein isolate, with their unique molecular structure characteristics—zein being rich in nonpolar amino acids (such as leucine, proline, and alanine) which endow it with strong hydrophobicity and dense film-forming ability, and chickpea protein having a complex structure that combines globulin and albumin, giving it moderate flexibility and abundant polar functional groups—can form a hydrophobic-hydrophilic dual network with an interpenetrating network structure under thermal induction, achieving a synergistic interface enhancement effect of internal anchoring and external barrier.

[0029] This invention further optimizes the mass ratio of each component. Specifically, the mass ratio of zein to chickpea protein isolate is 6-10:4-8. If the proportion of zein is too high, although the water-blocking performance is further improved, the film becomes too brittle after formation, making it prone to cracking under the internal vapor pressure generated by microwave reheating, leading to coating detachment. Conversely, if the proportion of chickpea protein isolate is too high, although the interfacial adhesion is enhanced, the hydrophobic network density is insufficient, failing to effectively block water vapor penetration, resulting in softening of the food surface after reheating. Only within the above specific ratio range can the two form an interpenetrating network structure, achieving both water resistance and crack resistance.

[0030] By weight, the raw materials include: 35-45 parts low-gluten wheat flour, 15-20 parts modified cassava starch, 5-10 parts corn starch, 3-6 parts pregelatinized starch, 1-2 parts sodium bicarbonate, 6-10 parts zein, and 4-8 parts chickpea protein isolate. Secondly, the content of the basic components also plays a decisive role in the final product quality. Low-gluten wheat flour, as the skeletal material, at a content between 35-45 parts, ensures the coating layer has suitable viscosity and film-forming properties. If the content is too low, the skeletal strength of the coating layer is insufficient, making it prone to cracking during pre-frying; if the content is too high, the gluten network is too strong, resulting in a hard coating layer lacking crispness. The content of modified cassava starch is set at 15-20 parts, mainly used to adjust crispness and gelatinization characteristics. If the content is too low, the porous structure formed by starch gelatinization is insufficient, reducing crispness; if the content is too high, the oil absorption rate of the coating layer increases significantly, and the texture becomes hard. The addition of 3-6 parts of pregelatinized starch aims to improve the initial adhesion speed of the coating to the food surface. Too little starch results in poor adhesion, while too much leads to an overly thick coating that easily absorbs moisture. The amount of 1-2 parts of sodium bicarbonate is precisely calculated to generate an appropriate amount of gas during frying, making the coating fluffy. Too little sodium bicarbonate results in insufficient fluffiness, while too much leads to a loose and brittle coating structure. Through the synergistic effect of the above specific proportions, the coating in this embodiment achieves optimal crispness and the lowest peeling rate after microwave reheating while ensuring good handling performance.

[0031] The functional components of this invention also include 2-4 parts of sunflower seed oil, and are prepared into microcapsule form. Specifically, the functional components consist of microcapsules made from zein, chickpea protein isolate, and sunflower seed oil, with sunflower seed oil as the core material and zein and chickpea protein isolate as the shell material. This embodiment uses microencapsulation technology to encapsulate the functional components, aiming to solve the problems of easy oxidation, uneven dispersion, and premature reaction of functional components during storage when oils are directly added. If sunflower seed oil is directly mixed with powder, the oil will quickly penetrate into the starch granules, causing powder clumping and reduced fluidity. Furthermore, during the storage period before pre-frying, the oil is highly susceptible to oxidative rancidity, producing off-odors. More importantly, directly mixed oils cannot achieve targeted and quantitative release during frying, making it difficult to form an ideal interfacial barrier film. Through microencapsulation, the sunflower seed oil is locked inside using a protein shell, achieving spatial isolation of the functional components in the dry powder state, significantly improving storage stability.

[0032] Sunflower seed oil, zein, and chickpea protein isolate were co-dispersed in an aqueous solution and homogenized under high pressure (30-50 MPa) 2-4 times to control the oil droplet size to 1-10 μm, forming a stable oil-in-water (O / W) composite emulsion. The emulsion was then spray-dried at an inlet temperature of 170-180℃ and an outlet temperature of 65-75℃. After the water evaporated rapidly, zein, due to its strong hydrophobicity, spontaneously migrated to the surface of the oil droplets and solidified, forming a dense hydrophobic outer shell. Chickpea protein isolate, due to its relative hydrophilicity, remained on the inner side of the shell and was in close contact with the core material, sunflower seed oil, thus spontaneously assembling into core-shell microcapsules with a hydrophobic outer layer and a hydrophilic inner layer gradient structure. During the pre-frying stage (oil temperature 170℃-190℃), the microcapsules exhibit a unique heat-triggered release mechanism: the shell softens instantly upon heating, and the internal sunflower seed oil expands, generating internal pressure that causes the microcapsules to melt and release. The released sunflower seed oil rapidly wets the surrounding breading particles, assisting the rapid unfolding and rearrangement of Zein and chickpea protein isolate at the oil-water interface, forming a continuous and gradient-distributed composite film in situ. The Zein-dominated hydrophobic outer layer effectively prevents excessive penetration of external oils and leakage of internal moisture, while the chickpea protein-dominated hydrophilic inner layer forms strong hydrogen bonds and electrostatic anchoring with the food surface. Compared to directly adding oils or simple physical mixing, the gradient barrier film constructed by these microcapsules has more uniform coverage, more precise interface control, and superior mechanical strength, thus significantly improving the crispness retention time and anti-shelling performance of the breading layer after microwave reheating.

[0033] Preferably, the chickpea protein isolate is a thermally modified chickpea protein isolate. While unmodified ordinary chickpea protein isolate possesses certain hydrophilicity and adhesiveness, its molecular structure is relatively compact, with most hydrophobic groups encapsulated within the molecule. Therefore, when co-constructing microcapsule wall materials with zein, there is still room for improvement in interfacial activity and interaction forces. Specific thermal modification treatment can improve its functional properties. The preparation method of the thermally modified chickpea protein isolate involves dispersing chickpea protein isolate in an alkaline buffer solution, heating it, and then cooling it in an ice bath to obtain the thermally modified chickpea protein isolate. Specifically, the pH value of the alkaline buffer solution is 9.0-9.5, the heating method is water bath heating, the water bath temperature is 85-95℃, and the water bath heating time is 8-15 minutes.

[0034] First, in a weakly alkaline environment (pH 9.0-9.5), the charge distribution on the surface of chickpea protein isolate molecules changes, and electrostatic repulsion loosens the tertiary structure of the protein molecules. Following this, a water bath heating treatment at 85-95℃ further disrupts the hydrogen bonds and hydrophobic interactions maintaining the protein's secondary structure, causing the α-helical and random coil structures of globulins and albumins to partially unfold. This structural unfolding has a dual positive effect: on the one hand, the hydrophobic groups originally encapsulated within the molecule are exposed, significantly increasing the protein's surface hydrophobicity, making it easier to adsorb at the oil-water interface, thus forming a tighter composite wall material with hydrophobic zein in subsequent microcapsule preparation; on the other hand, the unfolded peptide chains undergo molecular self-assembly under thermal induction, forming soluble nanoaggregates with a particle size distribution of 20-200 nm. This nanoscale structure is more conducive to constructing a dense network within the microcapsule shell.

[0035] More crucially, the cooling step after heating is essential. This invention employs an ice bath cooling method, the core purpose of which is to freeze the active conformation of the protein. At high temperatures, protein molecules are in a highly active state of motion. If cooled naturally, these molecules often excessively aggregate, forming large, insoluble precipitates, leading to modification failure. Ice bath cooling, however, can rapidly lower the system temperature in a very short time, quickly inhibiting the thermal motion of protein molecules, fixing the modified active conformation, and preventing irreversible excessive aggregation or precipitation.

[0036] Furthermore, if the pH value of the thermally modified chickpea protein isolate is below 9.0, the alkaline environment is insufficient to provide adequate electrostatic repulsion, resulting in insufficient protein molecule unfolding, inadequate exposure of hydrophobic groups, and insignificant modification effect. If the pH value is above 9.5, the excessively alkaline environment may cause protein hydrolysis, destroying its primary structure and even producing byproducts such as bitter peptides, affecting the taste of the food. Similarly, if the water bath temperature is below 85℃ or the heating time is less than 8 minutes, the thermal energy is insufficient to induce the full unfolding of the protein's secondary structure; if the temperature is above 95℃ or the time exceeds 15 minutes, the protein may undergo excessive denaturation, forming insoluble gels or precipitates, failing to form uniform nano-aggregates. Therefore, only within the specific process window of pH 9.0-9.5, 85-95℃, and 8-15 minutes can thermally modified chickpea protein isolate with high surface hydrophobicity, good dispersibility, and suitable molecular conformation be prepared, thus achieving optimal synergistic effects with zein in subsequent processing.

[0037] The present invention also provides an application of the above-mentioned pre-fried food coating powder, wherein the pre-fried food coating powder is used in the pre-coating step of the pre-fried food preparation process.

[0038] Specifically, the preparation process of pre-fried food includes the following steps: raw material pretreatment, pre-coating, battering, coating with briquettes, pre-frying, quick-freezing, and packaging. In the pre-coating step, the ingredients to be processed (such as diced chicken or fish fillets) are placed into a roller-type coating machine. The coating powder of this invention is added at a ratio of 100:8-12 (ingredient to coating powder mass ratio). The roller speed is set to 15-20 rpm, and the ingredients are tumbled for 3-5 minutes to ensure a uniform layer of dry powder adheres to the surface. The subsequent battering, coating with briquettes, and pre-frying steps are carried out according to conventional processes. The pre-frying oil temperature is controlled at 170℃-180℃, and the frying time is set to 60-90 seconds depending on the size of the ingredients. After pre-frying, the food is quickly placed in a quick-freezing tunnel at -35℃ or below for quick-freezing, and finally stored frozen at -18℃.

[0039] Example 1 The recipe for the pre-fried food coating in this embodiment includes: 40 parts low-gluten wheat flour, 18 parts modified tapioca starch, 8 parts corn starch, 5 parts pregelatinized starch, 1.5 parts sodium bicarbonate, 8 parts zein, and 6 parts chickpea protein isolate. Add all components to a three-dimensional mixer and mix at 30 rpm for 20 minutes to ensure uniform dispersion. This yields the pre-fried food coating.

[0040] Example 2 The recipe for the pre-fried food coating in this embodiment includes: 35 parts low-gluten wheat flour, 15 parts modified tapioca starch, 5 parts corn starch, 3 parts pregelatinized starch, 1 part sodium bicarbonate, 6 parts zein, and 4 parts chickpea protein isolate. Add all components to a three-dimensional mixer and mix at 30 rpm for 20 minutes to ensure uniform dispersion. This yields the pre-fried food coating.

[0041] Example 3 The recipe for the pre-fried food coating in this embodiment includes: 45 parts low-gluten wheat flour, 20 parts modified tapioca starch, 10 parts corn starch, 6 parts pregelatinized starch, 2 parts sodium bicarbonate, 10 parts zein, and 8 parts chickpea protein isolate. Add all components to a three-dimensional mixer and mix at 30 rpm for 20 minutes to ensure uniform dispersion. This yields the pre-fried food coating.

[0042] Example 4 40 parts low-gluten wheat flour, 18 parts modified tapioca starch, 8 parts corn starch, 5 parts pregelatinized starch, 1.5 parts sodium bicarbonate, and 17 parts microcapsules. Add all components to a three-dimensional mixer and mix at 30 rpm for 20 minutes to ensure uniform dispersion, thus obtaining the pre-fried food coating.

[0043] The preparation method of the microcapsules is as follows: Weigh the raw materials according to the following proportions by weight: 8 parts corn gliadin, 6 parts chickpea protein isolate, and 3 parts sunflower seed oil.

[0044] Zeat protein and chickpea protein isolate were dispersed in 100 parts of deionized water, sunflower seed oil was added, and 0.5 parts of α-cyclodextrin were added as a co-solvent. The mixture was pre-emulsified for 3 minutes at 8000 r / min using a high-shear dispersing emulsifier to form a crude emulsion. The crude emulsion was then transferred to a high-pressure homogenizer and homogenized three times at 40 MPa to obtain a homogeneous and stable oil-in-water (O / W) composite emulsion. Laser particle size analyzer determined the average droplet size in the emulsion to be 2.5 μm. The emulsion was then spray-dried using the following parameters: inlet temperature 175℃, outlet temperature 70℃, feed rate 20 mL / min, and atomizer speed 25000 r / min. After drying, the microcapsule powder was collected using a cyclone separator and passed through an 80-mesh sieve (180 μm pore size) to remove unencapsulated fine particles and agglomerates. 0.5% food-grade silica (by weight of microcapsules) was added as an anti-caking agent, and the mixture was thoroughly mixed to obtain the microcapsules. The resulting microcapsules were a pale yellow powder with good flowability, a particle size distribution between 10-50 μm, and an encapsulation efficiency (based on sunflower seed oil) of 87.6%.

[0045] Example 5 The difference between this embodiment and Embodiment 4 is that "2 parts of sunflower seed oil are used" and "the emulsion is formed by high-pressure homogenization at 30 MPa". All other steps are the same as in Embodiment 4.

[0046] Example 6 The difference between this embodiment and Embodiment 4 is that "4 parts of sunflower seed oil are used" and "50MPa high-pressure homogenization is used to form an emulsion". All other steps are the same as in Embodiment 4.

[0047] Example 7 In this embodiment, the chickpea protein isolate is replaced with thermally modified chickpea protein isolate, while everything else remains the same as in Example 4.

[0048] The method for preparing the heat-modified chickpea protein isolate is as follows: 100 g of chickpea protein isolate was dispersed in 1000 mL of a weakly alkaline buffer (0.05 M Na₂CO₃-NaHCO₃ buffer) at pH 9.3, and stirred until fully dispersed. The dispersion was then placed in a 90°C water bath and heated for 10 minutes with gentle stirring. After heating, the protein solution was immediately transferred to an ice bath and rapidly cooled to below 4°C to stabilize the protein's active conformation. The cooled protein solution was centrifuged at 5000 r / min for 15 minutes at 4°C, and the supernatant was collected. The supernatant was then freeze-dried to obtain the heat-modified chickpea protein isolate, which was then sealed and stored for later use. Dynamic light scattering analysis showed that the average particle size of the obtained protein nanoaggregates was 50-150 nm.

[0049] Example 8 The difference between this embodiment and Example 7 is that when preparing the thermally modified chickpea protein isolate, the pH value of the alkaline buffer solution is 9.0, the heating method is water bath heating, the water bath temperature is 85°C, and the water bath heating time is 8 minutes.

[0050] Example 9 The difference between this embodiment and Example 7 is that when preparing the thermally modified chickpea protein isolate, the pH value of the alkaline buffer solution is 9.5, the heating method is water bath heating, the water bath temperature is 95°C, and the water bath heating time is 15 minutes.

[0051] Comparative Example 1 The recipe for the pre-fried food coating in this comparative example includes: 40 parts low-gluten wheat flour, 18 parts modified tapioca starch, 8 parts corn starch, 5 parts pregelatinized starch, and 1.5 parts sodium bicarbonate. Add all components to a three-dimensional mixer and mix at 30 rpm for 20 minutes, ensuring uniform dispersion of each component, to obtain the pre-fried food coating.

[0052] Comparative Example 2 The recipe for the pre-fried food coating in this comparative example includes: 40 parts low-gluten wheat flour, 18 parts modified tapioca starch, 8 parts corn starch, 5 parts pregelatinized starch, 1.5 parts sodium bicarbonate, 8 parts casein, and 6 parts whey protein. Add all components to a three-dimensional mixer and mix at 30 rpm for 20 minutes to ensure uniform dispersion. This yields the pre-fried food coating.

[0053] Comparative Example 3 The recipe for the pre-fried food coating in this comparative example includes: 40 parts low-gluten wheat flour, 18 parts modified tapioca starch, 8 parts corn starch, 5 parts pregelatinized starch, 1.5 parts sodium bicarbonate, 8 parts rice protein, and 6 parts gelatin. Add all components to a three-dimensional mixer and mix at 30 rpm for 20 minutes to ensure uniform dispersion. This yields the pre-fried food coating.

[0054] Comparative Example 4 The recipe for the pre-fried food coating in this comparative example includes: 40 parts low-gluten wheat flour, 18 parts modified tapioca starch, 8 parts corn starch, 5 parts pregelatinized starch, 1.5 parts sodium bicarbonate, and 8 parts zein. Add all components to a three-dimensional mixer and mix at 30 rpm for 20 minutes to ensure uniform dispersion. This yields the pre-fried food coating.

[0055] Comparative Example 5 The recipe for the pre-fried food coating in this comparative example includes: 40 parts low-gluten wheat flour, 18 parts modified tapioca starch, 8 parts corn starch, 5 parts pregelatinized starch, 1.5 parts sodium bicarbonate, and 6 parts chickpea protein isolate. Add all components to a three-dimensional mixer and mix at 30 rpm for 20 minutes to ensure uniform dispersion. This yields the pre-fried food coating.

[0056] This paper presents an application of the pre-fried food coating powder described above, using it in the pre-coating step of the pre-fried food preparation process. Frozen chicken nuggets are selected as the application. The pre-fried food preparation process includes: raw material pretreatment, pre-coating, battering, coating with bran, pre-frying, quick-freezing, and packaging. In the pre-coating step, the chicken pieces to be treated are placed in a roller-type coating machine. The powder from each of the above embodiments and comparative examples is added at a ratio of 10:1 (ingredient to coating powder mass). The roller speed is set to 20 rpm, and the mixture is tumbled for 5 minutes to ensure a uniform layer of dry powder adheres to the surface of the ingredients. Subsequent battering, coating with bran, and pre-frying steps are carried out according to conventional processes. The pre-frying oil temperature is controlled at 170℃-180℃, and the frying time is set to 60-90 seconds depending on the size of the ingredients. After pre-frying, the mixture is quickly placed in a quick-freezing tunnel below -35℃ for quick-freezing, and finally stored frozen at -18℃ to obtain frozen pre-fried chicken nuggets.

[0057] The frozen and pre-fried chicken nuggets obtained above were tested, and the test indicators included separation rate, crispness, and moisture content after microwave reheating. Among them, the separation rate was defined as the percentage of the dehulled area to the total surface area; the crispness was measured by a texture analyzer to determine the breaking force, and the lower the value, the better the crispness; the moisture content was determined by the drying and weighing method. The test results are shown in Table 1 below.

[0058] Table 1 Performance test results of products after microwave reheating using Examples 1-9 and Comparative Examples 1-5 Twenty professional sensory evaluators were randomly invited to assess the color appeal and taste. The evaluations were conducted in a standard sensory evaluation room using a D65 standard light source to avoid interference from ambient light in color judgment. The evaluation results are shown in Table 2 below.

[0059] Table 2 Sensory evaluation of the products used in Examples 1-9 and Comparative Examples 1-5 Example 1 showed a separation rate of 9.2%, a breaking force of 12.3 N, and a moisture content of 19.3%, all three indicators being significantly better than all comparative examples. This demonstrates the synergistic enhancement effect of the hydrophobic-hydrophilic dual network structure formed by Zein and chickpea protein isolate in the optimal ratio. Sensory evaluation showed that the protein was uniformly golden and translucent, with a crispy outer skin and tender inner skin without peeling. It is the best representative of the basic formula of this invention.

[0060] Example 2 showed a separation rate of 10.1%, a breaking force of 13.0 N, and a moisture content of 20.2%, which were very close to those of Example 1. This indicates that within the lower limit of the ratio protected by the claims, the dual-network structure can still be effectively constructed, with only a slight decrease in performance due to the slightly lower total amount of functional components. Example 3 showed a separation rate of 9.7%, a breaking force of 12.7 N, and a moisture content of 19.8%, which were also very close to those of Example 1, indicating that no significant change in performance occurred within the upper limit of the functional component range.

[0061] In Example 4, the separation rate was reduced to 6.3%, the breaking force was reduced to 10.1 N, and the moisture content was reduced to 16.2%, which was a further improvement over Example 1. This reflects the advantages of the gradient barrier membrane given by the microcapsule thermally triggered release mechanism—sunflower seed oil is released at the moment of pre-frying, which helps Zein and chickpea protein isolate to rearrange rapidly at the oil-water interface, forming a composite membrane with more uniform coverage and better mechanical strength. Sensory evaluation showed that it was crisp and lasting, with an intact coating and no peeling.

[0062] Example 5 showed a separation rate of 6.9%, a breaking force of 10.6 N, and a moisture content of 16.8%, which were close to and slightly better than those of Example 4. This indicates that under the conditions of lower limits for core material dosage and homogenization pressure, the microcapsule encapsulation rate and structural integrity could still reach an effective level, and the process parameters were set reasonably. Example 6 showed a separation rate of 6.6%, a breaking force of 10.4 N, and a moisture content of 16.5%, which were close to the values ​​of Examples 4 and 5, indicating that an effective effect could be achieved within this range.

[0063] Example 7 achieved the best performance across the group in all indicators: separation rate 4.1%, breaking force 8.5 N, and moisture content 13.7%, showing further improvement over Example 4. The heat modification treatment fully unfolded the secondary structures of chickpea protein isolate globulin and albumin, exposing more hydrophobic groups and forming 50-150 nm nano-aggregates. This significantly enhanced the synergistic building ability with Zein, ultimately achieving optimal gradient barrier performance in the breading layer. Sensory evaluation showed excellent crispness, extremely strong coating, and the best taste.

[0064] Example 8 showed a separation rate of 4.6%, a breaking force of 9.0 N, and a moisture content of 14.3%, which were very close to those of Example 7. Under these process conditions, the degree of protein secondary structure development and the amount of nano-aggregate formation reached the effective threshold, indicating sufficient modification effect. Example 9 showed a separation rate of 4.4%, a breaking force of 8.8 N, and a moisture content of 14.1%, which were also very close to those of Example 7, indicating that no excessive protein denaturation or insoluble gel formation occurred within the process window, and the modification effect was stable.

[0065] Comparative Example 1, containing only basic components and no functional components, had the worst separation rate (38.5%), breaking force (28.6 N), and moisture content (33.4%). Sensory evaluation showed a dark, unevenly distributed color, and significant softening and dehulling after reheating, resulting in a poor texture. This result directly demonstrates that relying solely on the physical-mechanical interlocking mechanism of basic components such as low-gluten wheat flour and modified starch cannot achieve a stable bond between the coating layer and the food at the molecular level. Under the water vapor shear stress generated by microwave reheating, large-scale dehulling inevitably occurs.

[0066] Comparative Example 2, with 8 parts casein and 6 parts whey protein replacing the functional components, showed a separation rate of 27.3%, a breaking strength of 22.4 N, and a moisture content of 29.1%, which was an improvement over Comparative Example 1 but still far inferior to Example 1. Sensory evaluation revealed localized darker color, mediocre crispness, and localized peeling. Casein formed a loose gel structure rather than a dense membrane under heat induction, resulting in insufficient water-blocking density; whey protein excessively denatured under high-temperature frying conditions, forming a hard gel that could not provide flexible buffering. Neither could reproduce the interpenetrating double network effect conferred by the specific molecular structures of Zein and chickpea protein isolate.

[0067] Comparative Example 3, consisting of 8 parts rice protein and 6 parts gelatin as substitutes for the functional components, showed a separation rate of 30.6%, a breaking strength of 24.7 N, and a moisture content of 30.8%. Its performance was between that of Comparative Example 1 and Comparative Example 2. Sensory evaluation revealed a darker, less uniform color, poorer crispness, and heavier hulling. Rice protein exhibited high film-forming brittleness and was prone to cracking during temperature changes in freeze-reheat cycles. While gelatin possessed flexibility, its poor thermal stability led to melting and loss at pre-frying temperatures, failing to maintain an effective interfacial anchoring network.

[0068] Comparative Example 4 used only Zein, and its product moisture content of 21.5% was close to that of Example 1 (19.3%), which shows that Zein does have a water-blocking function. However, the separation rate was as high as 22.6%, which was much higher than that of Example 1 (9.2%). This directly reflects the defects of Zein when forming a film alone, such as high brittleness and weak anchoring force with the food interface.

[0069] Comparative Example 5 used only chickpea protein isolate, and its product had a separation rate of 17.4%, which was lower than that of Comparative Example 4, demonstrating the interface anchoring advantage of chickpea protein isolate. However, the moisture content was as high as 28.6%, and the breaking force was 21.3 N, indicating that its hydrophilic properties led to a large amount of water vapor penetration and the coating became soft and moist after reheating. Using chickpea protein isolate alone was insufficient in water resistance, resulting in a decrease in crispness.

[0070] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A coating powder for pre-fried food, characterized in that, Its raw materials include basic components and functional components; The basic components include low-gluten wheat flour, modified cassava starch, corn starch, pregelatinized starch, and sodium bicarbonate. The functional components include zein and chickpea protein isolate.

2. The pre-fried food coating powder according to claim 1, characterized in that, The mass ratio of zein to chickpea protein isolate is 6-10:4-8.

3. The pre-fried food coating powder according to claim 1, characterized in that, By weight, the raw materials include: 35-45 parts low-gluten wheat flour, 15-20 parts modified cassava starch, 5-10 parts corn starch, 3-6 parts pregelatinized starch, 1-2 parts sodium bicarbonate, 6-10 parts zein, and 4-8 parts chickpea protein isolate.

4. The pre-fried food coating powder according to claim 3, characterized in that, The functional components also include 2-4 parts of sunflower seed oil by weight.

5. The pre-fried food coating powder according to claim 4, characterized in that, The functional components include microcapsules made from zein, chickpea protein isolate, and sunflower seed oil, with the sunflower seed oil as the core material and the zein and chickpea protein isolate as the shell material.

6. The pre-fried food coating powder according to claim 5, characterized in that, The microcapsules are prepared by dispersing sunflower seed oil, zein and chickpea protein isolate in an aqueous solution, homogenizing under high pressure of 30 MPa-50 MPa to form an emulsion, and spray drying the resulting emulsion to obtain microcapsules.

7. The pre-fried food coating powder according to claim 5, characterized in that, The chickpea protein isolate is a heat-modified chickpea protein isolate.

8. The pre-fried food coating powder according to claim 7, characterized in that, The method for preparing the heat-modified chickpea protein isolate is as follows: dispersing chickpea protein isolate in an alkaline buffer solution and heating it, then cooling it in an ice bath to obtain the heat-modified chickpea protein isolate.

9. The pre-fried food coating powder according to claim 8, characterized in that, The alkaline buffer solution has a pH of 9.0-9.5 and is heated by a water bath at a temperature of 85-95°C for 8-15 minutes.

10. The application of the pre-fried food coating powder according to any one of claims 1-9, characterized in that, The pre-fried food coating powder is used in the pre-coating step of the pre-fried food preparation process.

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