A complex method for improving the floating property of egg white in freeze-dried egg soup

Abstract

This invention discloses a composite method for improving the floating property of egg drop soup in freeze-dried egg drop soup, belonging to the field of food processing technology. This method solves the problems of egg drop settling and uneven dispersion after brewing in existing freeze-dried egg drop soups through the synergistic effect of egg liquid pretreatment, composite colloid addition, egg drop-soup pre-cooking, and integrated freeze-drying process optimization (including partition heating temperature control). Simultaneously, it achieves integrated freeze-drying of the egg drop and soup base. Freeze-dried egg drop soup treated by this method, when brewed in hot water at 85-95℃, exhibits an egg drop floating rate of over 90%, with high integration of the egg drop and soup base, maintaining good taste and appearance, significantly improving the product's eating experience and market competitiveness.

Description

Technical Field

[0001] This invention relates to the field of food processing technology, specifically to a composite method for improving the floating property of egg flowers in freeze-dried egg drop soup, which is particularly suitable for instant food products where egg flowers and soup base are freeze-dried as a whole. Background Technology

[0002] Freeze-dried egg drop soup has become an important category in the instant food market due to its convenient preparation and good nutrient retention. Currently, existing patents mostly focus on flavor and rehydration. For example, patent CN 120501209 A invented a freeze-dried kelp egg drop soup block and its preparation method and application, mainly improving the flavor of kelp and the rehydration of freeze-dried kelp egg drop soup. In addition, patent CN116671617 A invented a preparation method and production line for seaweed egg drop soup, also focusing on its flavor, texture, and nutrition. Another patent, CN202010973019.X, discloses a frozen egg drop processing method and an egg drop cooking device. This product uses vegetable oil, whole egg liquid, pregelatinized starch, and xanthan gum as its base ingredients, combined with various phosphates. It achieves industrial-scale production of frozen egg drop soup through an emulsification-separate cooking-quick freezing process. The core objective is the emulsification stability and preservation of the egg drop soup itself. The product is individually frozen egg drop soup, requiring subsequent use with a soup base. It lacks a design to prevent egg drop soup from floating, relying solely on quick freezing (≤-30℃). Without vacuum drying and structural protection processes, it easily sinks after rehydration due to its dense structure. Existing freeze-dried egg drop soups suffer from poor egg drop soup formation due to the lack of a pre-cooking process. Furthermore, the single heating temperature of the partitions in the original freeze-drying process easily causes uneven moisture loss from the egg drop soup, leading to structural collapse, increased density, and ultimately, the egg drop soup sinking easily and having a poor taste. Currently, the industry mostly improves the overall system stability by adding stabilizers (such as single colloids) to the soup base, but no patent has specifically addressed the problem of excessively rapid egg drop soup settling. Therefore, there is an urgent need to develop a composite method that includes pre-cooking process, adapts to integrated freeze-drying, and optimizes freeze-drying process, so as to significantly improve the floating property of egg flowers while ensuring the integration of egg flower formation with soup base. Summary of the Invention

[0003] This invention aims to solve the problems of existing freeze-dried egg drop soup where the egg drop tends to sink to the bottom after brewing, low compatibility between the egg drop and soup base in freeze-drying, and easy collapse of the egg drop structure during the freeze-drying process. It provides a method with "egg liquid pretreatment - egg drop and soup base pre-cooking - staged freeze-drying" as the core, and constructs a porous structure of egg drop through intermittent ultrasound, constant temperature water bath pre-cooking, and temperature-controlled freeze-drying with partitions, so as to ensure the floating property and the degree of integration with the soup base, and achieve a balance between high floating rate of egg drop, good shapeability and high degree of integration with the soup base.

[0004] The technical solution of the present invention:

[0005] A compound method for improving the buoyancy of egg drop soup in freeze-dried egg drop soup includes the following steps:

[0006] (1) Modified starch pregelatinization: Modified starch is mixed with water and heated to gelatinize to obtain pregelatinized starch;

[0007] (2) Preparation of composite colloid: Guar gum and xanthan gum are mixed and added to egg liquid, and stirred until completely dissolved to form egg liquid-colloid mixture;

[0008] (3) Egg liquid-auxiliary material premixing: Egg liquid-colloidal mixture is mixed and stirred with pregelatinized starch, and then subjected to intermittent ultrasonic treatment to obtain egg liquid-auxiliary material mixture;

[0009] (4) Soup base preparation: Add dextrin to water and stir to dissolve. Add salt, monosodium glutamate and chicken essence in sequence, continue stirring, and finally add kelp sprouts and stir to make the basic soup base.

[0010] (5) Egg drop-soup base fusion and cooking: Pour the egg liquid-auxiliary ingredients mixture into the base soup base at a constant temperature of 80-95℃ at a slow rate, and keep stirring to make the egg liquid form uniform semi-cooked egg drop, thus obtaining the egg drop-soup base mixture.

[0011] (6) Integrated molding and pre-freezing: Pour the egg drop soup base mixture into a molding mold for pre-freezing;

[0012] (7) Stage freeze-drying: After pre-freezing, the freeze-drying is carried out in stages in a vacuum environment by using a partition heating method;

[0013] (8) Post-freeze-drying treatment: After freeze-drying, cool the finished product and remove the mold;

[0014] (9) Moisture-proof packaging: Vacuum packaging of finished products.

[0015] Further, in step (1), the mass ratio of modified starch to water is 0.06-0.12:1; the temperature for gelatinization is 80-85℃, and the gelatinization time is 8-12 min; the stirring rate for pregelatinization is 200-300 r / min to avoid starch particle agglomeration and ensure uniform gelatinization; the modified starch is hydroxypropyl distarch phosphate, and the degree of substitution of the modified starch is 0.02-0.05.

[0016] Furthermore, in step (2), the mass ratio of guar gum to xanthan gum is 4-2:1; the total mass of guar gum and xanthan gum accounts for 0.3-0.8% of the mass of the egg liquid; and the stirring and dissolving temperature is 40-50 ℃.

[0017] Further, in step (3), the mass ratio of the egg liquid-colloid mixture to the pregelatinized starch is 3-1:1; the stirring speed is 300-500 r / min, and the stirring time is 10-15 min; the pregelatinized starch needs to be cooled to 40-45 ℃ for use; the ultrasonic power is 200-250 W, and the total ultrasonic treatment time is 3-6 min; the specific method is to ultrasonically treat for 1 min, pause for 30 s, and repeat 4-6 times.

[0018] Furthermore, in step (4), the order of adding salt, monosodium glutamate, and chicken essence is as follows: first add salt and stir until dissolved, then add monosodium glutamate, and finally add chicken essence. During the addition process, the soup temperature is kept at 45-55℃ to avoid the volatilization of flavor substances in chicken essence due to high temperature. Before adding kelp seedlings, they need to be blanched in boiling water for 5-10 seconds and then cooled immediately to remove the fishy smell of kelp seedlings while retaining their texture. The proportions of each substance in the basic soup base by mass are as follows: dextrin 5-8%, salt 1-3%, monosodium glutamate 1-3%, chicken essence 1-4%, and kelp seedlings 2-5%.

[0019] Further, in step (5), the mass ratio of egg liquid-auxiliary ingredient mixture to basic soup base is 1~20:100~200; the egg flower-soup base fusion and cooking is carried out by constant temperature water bath heating, with a temperature fluctuation range of ≤±1℃, and real-time monitoring by temperature controller to avoid temperature fluctuations causing egg flowers to clump or not form; the pouring rate of egg liquid-auxiliary ingredient mixture is 5-10 mL / min, and by controlling the pouring rate, it is ensured that the egg liquid is evenly dispersed in the soup base to form semi-cooked egg flowers of uniform size, and to avoid egg flowers from agglomerating; the stirring rate is 300-600 r / min.

[0020] Furthermore, in step (6), the pre-freezing temperature is -42 to -38℃; the pre-freezing time is 4-6 h; the mold is a food-grade polytetrafluoroethylene shaping mold with a specification of 35mm×35mm×15mm; the inner wall is provided with a polytetrafluoroethylene non-stick coating (thickness 5-6 μm), and it is sterilized by high-pressure steam at 121℃ for 15-20 min before use to ensure the hygiene and safety of the product and prevent egg curd sticking.

[0021] Furthermore, in step (7), the total freeze-drying time is 11-15 h; in step (8), the cooling conditions are: temperature 25-28℃, relative humidity 30-35%, and cooling time 25-35 min.

[0022] Further, in step (7), the temperature control of the partition heating during the staged freeze-drying is as follows: the partition temperature is controlled at 25-30℃ in the first stage (6-8 h), the partition temperature is raised to 30-40℃ in the second stage (2-3 h), and the partition temperature is controlled at 45-50℃ in the third stage (3-4 h), with the temperature increase rate in each stage not exceeding 5℃ / h. The vacuum degree is maintained at 60-100 Pa in the first stage (6-8 h), the vacuum degree is reduced to 40-60 Pa in the second stage (2-3 h), and the vacuum degree is maintained at 10-20 Pa in the third stage (3-4 h). Through the coordinated control of vacuum degree and partition temperature, the collapse of the egg-shaped structure is avoided.

[0023] Furthermore, in step (9), the vacuum packaging uses a PET / AL / PE three-layer composite film, the vacuum degree of the vacuum packaging is -0.095 to -0.1 MPa, the film thickness is 80-120 μm, and 1~3 g of food-grade desiccant (montmorillonite or silica gel) is added inside the packaging to further prevent the finished product from absorbing moisture.

[0024] The core of this invention lies in improving the floating property, integrated freeze-drying adaptability, and structural stability of egg drop soup through a five-step synergistic process:

[0025] Egg liquid pretreatment (including intermittent ultrasonic operation): Modified starch (with a specific degree of substitution) is combined with intermittent ultrasonic treatment. The modified starch forms a porous structure on the surface of the egg liquid, reducing the density of egg curds. Intermittent ultrasonic treatment avoids local overheating of the egg liquid and promotes uniform mixing of starch and egg liquid, laying the foundation for uniform dispersion of egg curds after pre-cooking.

[0026] Synergistic effect of composite colloids: Guar gum increases the viscosity of egg liquid and enhances the dispersion stability of egg curds, while xanthan gum forms a three-dimensional network structure and reduces the settling speed of egg curds.

[0027] Egg drop and soup base pre-cooking (including rate control): By stabilizing the temperature through water bath heating and controlling the rate at which the egg liquid is poured in, the egg liquid is made into semi-cooked egg drops of uniform size. The semi-cooked state ensures that the egg drops are not easily broken and at the same time allows them to be integrated with the soup base in advance.

[0028] Integrated molding: The non-stick mold with ventilation holes accelerates the release of moisture, prevents the egg-shaped structure from collapsing due to moisture retention, and improves freeze-drying efficiency.

[0029] Optimization of freeze-drying process (including staged temperature control of the partition): The addition of a partition heating temperature control in stages, with low temperature (25-30 ℃) in the early stage of sublimation to prevent the surface of the egg curd from hardening too early and preventing internal moisture from escaping, and high temperature (30-40 ℃) in the middle and late stages of sublimation to accelerate moisture removal, and high temperature (45-50 ℃) in the desorption stage to reduce residual moisture; at the same time, the vacuum degree is adjusted to ensure the stability of the porous structure of the egg curd, further reducing the density and improving buoyancy.

[0030] The beneficial effects of this invention are as follows:

[0031] (1) Excellent in both buoyancy and structural stability: Egg flowers treated by this method can achieve a buoyancy rate of over 90% after brewing, and can float for more than 5 minutes. Moreover, the egg flowers have an intact structure without collapsing and are evenly dispersed.

[0032] (2) High integration of egg drop and soup base: The combination of pre-cooking and integrated freeze-drying results in no separation of egg drop and soup base, good rehydration effect, and consistent taste when eaten;

[0033] (3) Strong controllability of process details: From the intermittent ultrasonic treatment of egg liquid and the compound colloidal stabilization system to the staged temperature control of freeze-drying partition, the parameters of each link are clear and suitable for large-scale industrial production;

[0034] (4) Long shelf life: Through temperature control during the analysis stage, vacuum packaging and desiccant synergy, the residual moisture of the finished product is ≤3%, the risk of moisture absorption is low, and the shelf life is extended to more than 12 months;

[0035] (5) High-quality egg drop soup: Avoid oxidation of egg liquid and local overheating, keep the egg drop soup fresh in color and soft in texture, without stickiness or clumping. Attached Figure Description

[0036] Figure 1 The rehydration effect is compared between the control group and the sample in Example 1. Detailed Implementation

[0037] The technical solution of the present invention will be further illustrated by the following embodiments.

[0038] Example 1

[0039] (1) Starch pregelatinization: Hydroxypropyl distarch phosphate (degree of substitution 0.03) was mixed with water at a mass ratio of 1:10 and stirred at 240 r / min for 10 min in a water bath at about 85℃ until a transparent paste was formed. The mixture was then cooled to 43℃ to obtain pregelatinized starch.

[0040] (2) Preparation of composite colloid: Take 8 g of fresh egg liquid, add 0.5% composite colloid (guar gum: xanthan gum mass ratio = 2:1), stir at 45℃ for 13 min; stir until completely dissolved to form egg liquid-colloid mixture;

[0041] (3) Egg liquid-auxiliary material premixing: Egg liquid-colloidal mixture is mixed and stirred with pregelatinized starch (stirring speed is 400 r / min, stirring time is 12 min), and then subjected to intermittent ultrasonic treatment (250 W, treatment for 1 min, pause for 30 s, cycle 5 times) to obtain egg liquid-auxiliary material mixture;

[0042] (4) Soup base preparation: Add 6.5% dextrin to water and stir at 55℃ for 5 min until dissolved. Then add 2% salt, 2% monosodium glutamate, and 1.8% chicken essence in sequence and continue stirring for 5 min. Finally, add 3% kelp sprouts (which need to be blanched in boiling water at 100℃ for 6 s and then cooled immediately) and stir for 3 min to make the basic soup base.

[0043] (5) Egg drop-soup base fusion and cooking: The soup base temperature is maintained at 90℃ (fluctuation ±1℃) by water bath heating. The egg liquid-colloid mixture and the base soup base are poured slowly into the soup base at a mass ratio of 15:180 at a rate of 8 mL / min, while stirring at 500 r / min for 6 min to form semi-cooked egg drops with a diameter of 3-4 mm, thus obtaining the egg drop-soup base mixture.

[0044] (6) Integrated molding and pre-freezing: Pour the egg drop soup base mixture into a food-grade polytetrafluoroethylene molding mold (35mm×35mm×15mm) after high pressure steam sterilization, with a material thickness of 1 cm, and pre-freeze at -40℃ for 5 h;

[0045] (7) Stage freeze drying: The freeze dryer was then started and the temperature was controlled in stages: the first stage was 7 h (partition temperature 28℃, vacuum degree 80 Pa), the second stage was 3 h (partition temperature 35℃, vacuum degree 45 Pa), the third stage was 3 h (partition temperature 48℃, vacuum degree 15 Pa), the temperature rise rate was 4 ℃ / h, and the total freeze drying time was 13 h.

[0046] (8) Post-freeze-drying treatment: Place the finished product in an environment with a temperature of 26℃ and a relative humidity of 30% for 30 min to cool, and then demold to obtain the finished product.

[0047] (9) Moisture-proof packaging: PET / AL / PE composite film (100 μm thick) is used for packaging under a vacuum of -0.098 MPa. 1 g of montmorillonite desiccant is added to each bag and stored away from light.

[0048] Tests showed that when the finished product was steeped in 90℃ hot water, the egg flowers had a high floating rate, intact structure, and were evenly integrated with the soup base. The residual moisture content was less than 2.5%, and the texture was soft and non-sticky.

[0049] Example 2

[0050] (1) Modified starch pregelatinization: Hydroxypropyl distarch phosphate with a degree of substitution of 0.03 was selected as the modified starch. The starch and water were mixed at a mass ratio of 0.08:1 and heated and gelatinized for 10 min at 82℃ and 250 r / min to obtain pregelatinized starch. The starch was then cooled to 42℃ for later use.

[0051] (2) Preparation of composite colloid: Guar gum and xanthan gum are mixed at a mass ratio of 3:1. Take 0.5% of the total mass of the mixed colloid as the mass of the egg liquid and add it to the fresh egg liquid. Stir at 45°C until completely dissolved to form an egg liquid-colloid mixture.

[0052] (3) Egg liquid-additive premixing: The cooled pregelatinized starch and egg liquid-colloid mixture were mixed at a mass ratio of 2.5:1 and stirred at 400 r / min for 12 min. Then, intermittent ultrasonic treatment was performed with an ultrasonic power of 220W. Specifically, the ultrasonic treatment was performed for 1 min, paused for 30 s, and repeated 5 times for a total ultrasonic time of 5 min to obtain egg liquid-additive mixture.

[0053] (4) Soup base preparation: Add dextrin to deionized water and stir to dissolve, maintaining the soup base temperature at 45℃; add salt, monosodium glutamate (MSG) and chicken essence in sequence (add salt first and stir until dissolved, then add MSG, and finally add chicken essence), and continue stirring until evenly mixed; blanch kelp seedlings in boiling water for 8 seconds and cool immediately, then add them to the above system and stir to prepare the basic soup base. The mass ratio of each substance in the basic soup base is as follows: dextrin 6%, salt 2%, MSG 2%, chicken essence 3%, and kelp seedlings 3%.

[0054] (5) Egg drop-soup base fusion and cooking: The egg liquid-auxiliary ingredients mixture and the base soup base are poured into the base soup base at a mass ratio of 15:180 at a rate of 7 mL / min. The mixture is heated in a constant temperature water bath and monitored in real time by a temperature controller. The temperature fluctuation range is controlled within ±0.8℃. At the same time, the mixture is continuously stirred at a rate of 450 r / min to make the egg liquid form uniform semi-cooked egg drop, thus obtaining the egg drop-soup base mixture.

[0055] (6) Integrated molding and pre-freezing: Pour the egg drop soup base mixture into a food-grade polytetrafluoroethylene molding mold (35mm×35mm×15mm) that has been sterilized by high-pressure steam at 121℃ for 18 min, and pre-freeze at -40℃ for 5 h.

[0056] (7) Staged freeze-drying: After pre-freezing, the freeze-drying is carried out in stages under vacuum using a partition heating method. The total freeze-drying time is 13 h. The specific control parameters are as follows: In the first stage, the partition temperature is controlled at 28℃ and the vacuum degree is maintained at 80 Pa for 6 h; in the second stage, the partition temperature is raised to 35℃ for 2 h, the heating rate is 4℃ / h, and the vacuum degree is reduced to 50 Pa; in the third stage, the partition temperature is controlled at 48℃ for 5 h, the heating rate is 5℃ / h, and the vacuum degree is maintained at 15 Pa.

[0057] (8) Post-freeze-drying treatment: After freeze-drying, place the finished product in an environment with a temperature of 26℃ and a relative humidity of 35% for 30 minutes to cool, and then demold.

[0058] (9) Moisture-proof packaging: PET / AL / PE composite film (100 μm thick) is used for packaging under a vacuum of -0.098 MPa. 1 g of montmorillonite desiccant is added to each bag and stored away from light.

[0059] Example 3

[0060] (1) Modified starch pregelatinization: Hydroxypropyl distarch phosphate with a degree of substitution of 0.04 was selected as the modified starch. The starch and water were mixed at a mass ratio of 0.11:1 and heated and gelatinized at 84℃ and 280 r / min for 11 min to obtain pregelatinized starch. The starch was then cooled to 44℃ for later use.

[0061] (2) Preparation of composite colloid: Guar gum and xanthan gum are mixed at a mass ratio of 2:1. Take 0.7% of the total mass of the mixed colloid as the mass of the egg liquid and add it to the fresh egg liquid. Stir at 48°C until completely dissolved to form an egg liquid-colloid mixture.

[0062] (3) Egg liquid-additive premixing: The cooled pregelatinized starch and egg liquid-colloid mixture were mixed at a mass ratio of 1.5:1 and stirred at 480 r / min for 14 min. Then, intermittent ultrasonic treatment was performed with an ultrasonic power of 240W. Specifically, the ultrasonic treatment was performed for 1 min, paused for 30 s, and repeated 6 times for a total ultrasonic time of 6 min to obtain the egg liquid-additive mixture.

[0063] (4) Soup base preparation: Add dextrin to deionized water and stir to dissolve, maintaining the soup base temperature at 50℃; add salt, monosodium glutamate (MSG) and chicken essence in sequence (add salt first and stir until dissolved, then add MSG, and finally add chicken essence), and continue stirring until evenly mixed; blanch kelp seedlings in boiling water for 9 seconds and immediately cool them, then add them to the above system and stir to prepare the basic soup base. The proportions of each substance in the basic soup base by mass are as follows: dextrin 7%, salt 3%, MSG 1%, chicken essence 4%, and kelp seedlings 4%.

[0064] (5) Egg drop-soup base fusion and cooking: The egg liquid-auxiliary ingredients mixture and the base soup base are poured into the base soup base at a constant temperature of 93℃ at a mass ratio of 10:200. The mixture is heated in a constant temperature water bath and monitored in real time by a temperature controller. The temperature fluctuation range is controlled within ±0.5℃. At the same time, the mixture is continuously stirred at a rate of 550 r / min to make the egg liquid form uniform semi-cooked egg drop, thus obtaining the egg drop-soup base mixture.

[0065] (6) Integrated molding and pre-freezing: Pour the egg drop soup base mixture into a food-grade polytetrafluoroethylene molding mold (35mm×35mm×15mm, with 3 1mm diameter vent holes at the bottom and a 5.8μm thick polytetrafluoroethylene non-stick coating on the inner wall) that has been sterilized by high-pressure steam at 121℃ for 19 min, and pre-freeze it at -39℃ for 5.5 h.

[0066] (7) Stage-by-stage freeze-drying: After pre-freezing, the freeze-drying is carried out in stages under vacuum using a partition heating method. The total freeze-drying time is 14 h. The specific control parameters are as follows: During the sublimation stage (0-6 h), the partition temperature is controlled at 29 °C and the vacuum degree is maintained at 90 Pa; during the middle and late stages of sublimation (6-8 h), the partition temperature is raised to 38 °C, the heating rate is 4.5 °C / h, and the vacuum degree is reduced to 55 Pa; during the desorption stage (8-14 h), the partition temperature is controlled at 49 °C, the heating rate is 4.8 °C / h, and the vacuum degree is maintained at 18 Pa.

[0067] (8) Post-freeze-drying treatment: After freeze-drying, place the finished product in an environment with a temperature of 27°C and a relative humidity of 34% for 33 minutes to cool, and then remove the mold.

[0068] (9) Moisture-proof packaging: PET / AL / PE composite film (100 μm thick) is used for packaging under a vacuum of -0.098 MPa. 1 g of montmorillonite desiccant is added to each bag and stored away from light.

[0069] Comparative Example 1

[0070] Egg drop soup with 0.5% xanthan gum added alone, prepared using conventional freeze-drying methods without partition temperature control or pre-cooking, served as a control group and was compared with Example 1 of this invention.

[0071] Comparative Example 2

[0072] Except for step (2), in which guar gum and xanthan gum were not added to the egg liquid, the other steps were exactly the same as in Example 1.

[0073] Comparative Example 3

[0074] In step (3), only mechanical stirring is used to mix the egg liquid-colloid mixture with the pregelatinized starch, without ultrasonic treatment. The remaining steps are the same as in Example 1.

[0075] 1. Indicator Measurement

[0076] 1.1 Determination of the rehydration effect of egg drop soup

[0077] Take 15 g of each of the control group and the sample from Example 1, and redissolve them in 300 mL of hot water at 95°C. Record the floating state of the egg drop soup.

[0078] 1.2 Determination of rehydration ratio

[0079] Take 2g of each sample from the control group and Example 1, immerse them in room temperature deionized water for 5 minutes, then remove them, drain the surface water, and weigh them. The rehydration ratio is calculated using the following formula:

[0080]

[0081] In the formula, m1 is the weight after rehydration, in g; m2 is the weight before rehydration, in g.

[0082] 1.3 Texture determination

[0083] Appropriate amounts of the control group and the freeze-dried egg flowers prepared in Example 1 were taken for TPA full texture determination. The texture characteristics of the egg flowers were determined using a TA / 2 probe. The test parameters were: pre-test speed 2.00 mm / s, test speed 1.00 mm / s, post-test speed 2.00 mm / s, compression deformation 50%, and triggering force 5.0 g.

[0084] 2. Test Results

[0085] 2.1 Rehydration effect

[0086] The rehydration effects of the control group and the sample in Example 1 are as follows: Figure 1 As shown, the results indicate that most of the egg flowers in the freeze-dried egg drop soup prepared by this patent remained floating after 5 minutes, while more than 70% of the egg flowers in the control group had settled, proving the effectiveness of this patent in improving the buoyancy of egg flowers.

[0087] 2.2 Results of the rehydration ratio

[0088] The rehydration ratios of the freeze-dried egg drop soup and the freeze-dried samples are shown in Table 1. The results show that the freeze-dried egg drop soup prepared in Example 1 has a higher rehydration ratio, which indicates that it has a more porous internal structure, which can better provide buoyancy and prevent rapid sinking caused by poor internal rehydration after brewing.

[0089] Table 1. Rehydration ratio of freeze-dried egg drop soup and freeze-dried samples

[0090]

[0091] 2.3 Texture Results

[0092] As shown in Table 2, the control group had higher hardness, indicating that its structure was more compact after freeze-drying, consistent with the results of buoyancy and rehydration. This suggests that egg drop soup prepared by traditional freeze-drying process has a higher density and poorer rehydration due to its more compact structure, making water diffusion more difficult during rehydration, which may cause most of the egg drop soup to sink.

[0093] Table 2. Texture properties of the control group and the sample from Example 1

[0094]

Claims

1. A composite method for improving the buoyancy of egg drop soup in freeze-dried egg drop soup, characterized in that, Includes the following steps: (1) Modified starch pregelatinization: Modified starch is mixed with water and heated to gelatinize to obtain pregelatinized starch; (2) Preparation of composite colloid: Guar gum and xanthan gum are mixed and added to egg liquid, and stirred until completely dissolved to form egg liquid-colloid mixture; (3) Egg liquid-auxiliary material premixing: Egg liquid-colloidal mixture is mixed and stirred with pregelatinized starch, and then subjected to intermittent ultrasonic treatment to obtain egg liquid-auxiliary material mixture; (4) Soup base preparation: Add dextrin to water and stir to dissolve. Add salt, monosodium glutamate and chicken essence in sequence, continue stirring, and finally add kelp sprouts and stir to make the basic soup base. (5) Egg drop-soup base fusion and cooking: Pour the egg liquid-auxiliary ingredients mixture into the base soup base at a constant temperature of 80-95℃ at a slow rate, and keep stirring to make the egg liquid form uniform semi-cooked egg drop, thus obtaining the egg drop-soup base mixture. (6) Integrated molding and pre-freezing: Pour the egg drop soup base mixture into a molding mold for pre-freezing; (7) Stage freeze-drying: After pre-freezing, the freeze-drying is carried out in stages in a vacuum environment by using a partition heating method; (8) Post-freeze-drying treatment: After freeze-drying, cool the finished product and remove the mold; (9) Moisture-proof packaging: Vacuum packaging of finished products.

2. The composite method for improving the buoyancy of egg drop soup in freeze-dried egg drop soup according to claim 1, characterized in that, In step (1), the mass ratio of modified starch to water is 0.06-0.12:1; the temperature for gelatinization is 80-85℃, and the gelatinization time is 8-12 min; the stirring rate for pregelatinization is 200-300 r / min, and the modified starch is hydroxypropyl distarch phosphate, with a degree of substitution of 0.02-0.

05.

3. The composite method for improving the buoyancy of egg drop soup in freeze-dried egg drop soup according to claim 1, characterized in that, In step (2), the mass ratio of guar gum to xanthan gum is 4-2:1; the total mass of guar gum and xanthan gum accounts for 0.3-0.8% of the mass of the egg liquid; and the stirring and dissolving temperature is 40-50 ℃.

4. The composite method for improving the buoyancy of egg drop soup in freeze-dried egg drop soup according to claim 1, characterized in that, In step (3), the mass ratio of egg liquid-colloid mixture to pregelatinized starch is 3-1:1; the stirring speed is 300-500 r / min and the stirring time is 10-15 min; the pregelatinized starch needs to be cooled to 40-45 ℃ for use; the ultrasonic power is 200-250 W and the total ultrasonic treatment time is 3-6 min.

5. The composite method for improving the buoyancy of egg drop soup in freeze-dried egg drop soup according to claim 1, characterized in that, In step (4), the order of adding salt, monosodium glutamate and chicken essence is as follows: first add salt and stir until dissolved, then add monosodium glutamate, and finally add chicken essence. During the addition process, the soup temperature is kept at 45-55℃ to avoid the volatilization of flavor substances in chicken essence due to high temperature. Before adding kelp seedlings, they need to be blanched in boiling water for 5-10 seconds and then cooled immediately to remove the fishy smell of kelp seedlings while retaining their texture. The proportion of each substance in the basic soup base is as follows: dextrin 5-8%, salt 1-3%, monosodium glutamate 1-3%, chicken essence 1-4%, and kelp seedlings 2-5%.

6. The composite method for improving the buoyancy of egg drop soup in freeze-dried egg drop soup according to claim 1, characterized in that, In step (5), the mass ratio of egg liquid-auxiliary ingredient mixture to basic soup base is 1~20:100~200; the egg flower-soup base fusion and cooking is carried out by constant temperature water bath heating, with a temperature fluctuation range of ≤±1℃. The temperature is monitored in real time by a temperature controller to avoid temperature fluctuations causing the egg flower to clump or not form properly; the pouring rate of egg liquid-auxiliary ingredient mixture is 5-10 mL / min. By controlling the pouring rate, it is ensured that the egg liquid is evenly dispersed in the soup base to form semi-cooked egg flowers of uniform size, avoiding egg flower aggregation; the stirring rate is 300-600 r / min.

7. The composite method for improving the buoyancy of egg drop soup in freeze-dried egg drop soup according to claim 1, characterized in that, In step (6), the pre-freezing temperature is -42 to -38℃; the pre-freezing time is 4-6 h.

8. The composite method for improving the buoyancy of egg drop soup in freeze-dried egg drop soup according to claim 1, characterized in that, In step (7), the total freeze-drying time is 11-15 h; in step (8), the cooling conditions are: temperature 25-28℃, relative humidity 30-35%, and cooling time 25-35 min.

9. A composite method for improving the buoyancy of egg drop soup in freeze-dried egg drop soup according to claim 8, characterized in that, In step (7), the temperature control of the partition heating in the staged freeze-drying is as follows: the partition temperature in the first stage is controlled at 25-30℃ for 6-8 hours; the partition temperature in the second stage is raised to 30-40℃ for 2-3 hours; the partition temperature in the third stage is controlled at 45-50℃ for 3-4 hours, and the temperature increase rate in each stage does not exceed 5℃ / h; the vacuum degree in the first stage is maintained at 60-100 Pa, the vacuum degree in the second stage is reduced to 40-60 Pa, and the vacuum degree in the third stage is maintained at 10-20 Pa. Through the coordinated control of vacuum degree and partition temperature, the collapse of the egg-shaped structure is avoided.

10. A composite method for improving the buoyancy of egg drop soup in freeze-dried egg drop soup according to claim 1, characterized in that, In step (9), the film thickness is 80-120 μm.

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