Freeze-dried kelp egg drop soup block as well as preparation method and application thereof

Abstract

The invention provides a freeze-dried kelp egg drop soup block as well as a preparation method and application thereof. The freeze-dried kelp egg flower soup block is prepared from the following raw materials in parts by weight: 16 to 80 parts of kelp, 40 to 104 parts of eggs, 0.2 to 3.4 parts of table salt, 0.8 to 2.4 parts of starch, 2 to 18 parts of fresh ginger, 0.6 to 3.8 parts of sodium carboxymethyl cellulose, 1.2 parts of monosodium glutamate and 1.6 parts of chopped green onion. The kelp egg flower soup block prepared by the method is delicious in taste, rich in nutrition and good in rehydration property, the preparation method is scientific and reasonable, and the nutritional ingredients and flavor of the raw materials can be effectively reserved.

Description

Technical Field

[0001] The invention relates to the technical field of food processing, and in particular to a freeze-dried kelp and egg drop soup cube, a preparation method and application thereof. Background Art

[0002] Kelp, a seaweed used for both medicinal and edible purposes, is rich in various nutrients and physiologically active ingredients, including iodine, vitamins, minerals, protein, fatty acids, mannitol, fucoidan, and seaweed polyphenols. It has a good laxative effect, a strong sense of satiety, and is low in calories, making it a great choice for dieters. It is also known as a longevity vegetable. my country is the world's largest producer of kelp, but currently, the main processed products are dried kelp, salted kelp, and seasoned kelp shreds. The lack of innovative processed products limits kelp's market potential.

[0003] Pre-prepared meals have already undergone most of the cooking steps during production, allowing consumers to simply heat or process them before eating, making them ideal for today's fast-paced lifestyles. Currently, most kelp pre-prepared meal products on the market use a small amount of kelp as an ingredient, while pre-prepared meals using kelp as the primary ingredient are relatively rare.

[0004] Vacuum freeze-drying technology effectively preserves nutrients and flavor in food, making it particularly suitable for the production of pre-prepared meals. Applying this technology to the intensive processing of kelp to develop ready-to-use freeze-dried kelp sprout egg drop soup cubes holds significant market potential and practical significance. Summary of the Invention

[0005] In order to solve the problems mentioned in the background technology, the present application provides a freeze-dried kelp egg drop soup cube and a preparation method and application thereof.

[0006] The first aspect of the present invention provides a freeze-dried kelp egg drop soup cube, which comprises the following raw materials, by weight: 16-80 parts of kelp, 40-104 parts of eggs, 0.2-3.4 parts of salt, 0.8-2.4 parts of starch, 2-18 parts of ginger, 0.6-3.8 parts of sodium carboxymethyl cellulose, 1.0-1.4 parts of monosodium glutamate, and 1.4-1.8 parts of chopped green onions.

[0007] In this technical solution, by limiting the weight ranges of each ingredient, we can accommodate different taste preferences and production needs while maintaining the basic flavor and quality of the product. Kelp provides a unique taste and nutrition, eggs enrich nutrients and improve texture, salt adds flavor, starch improves structure and rehydration, ginger removes fishy smell and enhances flavor, CMC-Na aids in forming and stabilizing, and MSG and chopped green onions enhance flavor.

[0008] Furthermore, the kelp is tender kelp. Compared with ordinary kelp, tender kelp has a fresher taste, a relatively lighter fishy smell, and richer nutrients. It can bring better taste and higher nutritional value to soup cubes, thereby improving product quality and market competitiveness.

[0009] Furthermore, the freeze-dried kelp egg drop soup cubes also include 0.05-0.4 parts of kelp powder. Kelp powder is made by drying kelp with hot air at 55-65°C and then grinding it through a 180-220 mesh sieve. Preferably, the kelp powder is made by drying young kelp with hot air at 60°C and then grinding it through a 200 mesh sieve. The addition of kelp powder further enhances the kelp flavor and compensates for any flavor loss during the freeze-drying process. Passing through a 200 mesh sieve ensures the kelp powder's fineness, allowing it to be more evenly dispersed throughout the soup cube, improving the flavor stability and taste consistency of the soup cube.

[0010] Furthermore, the soup cube comprises the following ingredients, by weight: 64 parts kelp, 56 parts eggs, 2.6 parts salt, 1.2 parts starch, 10 parts ginger, 1.4 parts sodium carboxymethyl cellulose, 0.05-0.1 parts kelp powder, 1.2 parts monosodium glutamate, and 1.6 parts chopped green onions. Through optimized proportions, the synergistic effect of the ingredients results in a soup cube that achieves an optimal balance in taste, flavor, and texture. The soup cube has a rich kelp flavor, a suitable saltiness, a good egg aroma, and a harmonious fragrance, with a delicate texture and a stable structure.

[0011] Furthermore, the starch is tapioca starch. Tapioca starch has good gelatinization properties, which can make the soup cube structure firm and disperse well during rehydration, helping to form a delicate and uniform soup, improving the rehydration performance and taste of the soup cube, making it thicker and smoother.

[0012] A second aspect of the present invention provides a method for preparing freeze-dried kelp and egg drop soup cubes, the method comprising:

[0013] S1, cooking soup, dissolving sodium carboxymethyl cellulose in 800-1000 mL of boiling water, adding ginger and cooking for 1-3 minutes, adding pretreated kelp segments, cooking for 1-5 minutes, and separating the kelp segment raw material and soup;

[0014] S2, soup base processing, slowly adding the pre-treated egg liquid to the stirring soup, cooking for 2-5 minutes, adding chopped green onion, salt, starch, monosodium glutamate, and kelp powder to make the finished soup base, separating the finished soup base to obtain the original soup and soup base raw materials;

[0015] S3, forming and drying, the original soup is subjected to rotary evaporation to obtain concentrated soup, the soup raw materials, kelp segment raw materials and concentrated soup are mixed and molded for pre-freezing, and then vacuum freeze-dried to obtain freeze-dried kelp egg drop soup cubes.

[0016] In the above technical solution, in step S1, the cooking time and water amount are precisely controlled to fully blend the raw materials while retaining their respective characteristics; in step S2, egg liquid is added while stirring to ensure uniform formation of egg flowers, and the order and timing of adding each seasoning ensure uniform release of flavor; in step S3, rotary evaporation concentration, pre-freezing and vacuum freeze-drying are used to effectively remove moisture and maintain the nutrition, flavor and shape of the product.

[0017] Furthermore, before step S1, the process also includes desalting the salted kelp, drying it, and cutting it into 3-6 cm strips to obtain kelp segments; beating eggs to produce egg liquid. The desalting process effectively removes excess salt from the salted kelp, ensuring the broth has a moderate flavor; cutting the segments into appropriate lengths facilitates subsequent cooking and handling; and beating the eggs evenly to form a uniform and delicate egg drop soup, ensuring the texture and taste of the broth.

[0018] Furthermore, the S3 step includes:

[0019] S31, concentrating the original soup by rotary evaporation at a vacuum degree of -0.10 to -0.08 MPa to 45-55% of the original volume to obtain a concentrated soup;

[0020] S32, after the concentrated soup, kelp segment raw materials and soup base raw materials are molded, they are placed in a refrigerator for pre-freezing for more than 12 hours, transferred to a vacuum freeze dryer, further pre-frozen at a pre-freezing temperature of -20°C for 1-2 hours, vacuum frozen at a sublimation temperature of -5 to -4.8°C, and freeze-dried and analyzed at 50-70°C to a moisture content of ≤4%, to obtain freeze-dried kelp egg drop soup cubes.

[0021] In the above technical solution, S31 effectively removes moisture and increases the concentration of the soup, which is conducive to subsequent drying and molding; S32 accurately controls the pre-freezing, sublimation temperature and freeze-drying analysis temperature range to ensure that the soup cubes form a good structure during the drying process, avoid collapse, deformation and other problems, and effectively remove moisture to the appropriate content to ensure the shelf life and quality of the product.

[0022] Furthermore, the temperature rise scheme of the vacuum freeze drying process of S32 includes:

[0023] S321, prefreezing stage, maintained at -20 °C for 1 h;

[0024] S322, first sublimation stage, start vacuum 20Pa, increase temperature to -10℃ at a rate of 0.5℃ / min, and maintain for 2h;

[0025] S323, the second sublimation stage, heating to -5°C at a rate of 0.3°C / min for 2 h;

[0026] S324, the analytical drying stage, heating to 60°C at a rate of 1°C / min, maintaining the vacuum degree at 10 Pa, and drying to a moisture content of ≤4% to obtain freeze-dried kelp egg drop soup cubes.

[0027] In this technical solution, the temperature ramp during the vacuum freeze-drying process utilizes precise, step-by-step temperature control and a gradient vacuum level to prevent material collapse, forming a uniform, porous structure and shortening rehydration time. Slow temperature ramping during the sublimation phase ensures directional sublimation of ice crystals, ultimately precisely controlling the moisture content to ≤4%. This high percentage of bound water ensures a long shelf life and a taste similar to fresh soup after rehydration.

[0028] In a third aspect, the present invention proposes an application of freeze-dried kelp egg drop soup cubes, and the application of the freeze-dried kelp egg drop soup cubes described in the first aspect or the freeze-dried kelp egg drop soup cubes prepared by the method described in the second aspect in the preparation of instant soups.

[0029] Compared with the prior art, the present invention has the following advantages:

[0030] (1) The present invention uses fresh and tender kelp sprouts as the core raw material, and combines it with eggs, tapioca starch and other ingredients to form a synergistic system. By systematically optimizing the raw material ratio, not only does it retain the unique crisp and tender taste and rich nutrition of the kelp sprouts, but it also utilizes the emulsifying properties of eggs and the thickening properties of starch to make the soup cubes present a uniform egg-shaped structure after rehydration, with a smooth and harmonious taste. This solves the problems of loose texture and lack of flavor of traditional kelp soups, and provides a new product form for kelp deep processing.

[0031] (2) The present invention forms a gradient temperature increase scheme by precisely controlling the process parameters of the pre-freezing, sublimation, and analysis stages. This process can maximize the retention of heat-sensitive components such as iodine and fucoidan in kelp under low-temperature conditions, while also forming a loose and porous microstructure in the soup cubes. After rehydration, the soup cubes quickly return to the state of fresh soup, with a taste close to that of freshly cooked soup. Compared with traditional processes, the soup cubes prepared by this method have better rehydration properties and avoid nutrient degradation caused by high temperatures, achieving dual optimization of quality and nutrition.

[0032] (3) The freeze-dried soup cubes of the present invention adopt a block design. A single block can be brewed into soup, and can also be used as a seasoning in various scenarios such as instant noodles and self-heating foods. By optimizing the packaging process, the shelf life of the product is greatly extended while maintaining the convenience of "ready to eat". This not only meets consumers' demand for healthy fast food, but also develops high-value-added terminal products for the kelp industry, promotes the technological upgrade of kelp processing from primary processing to deep processing, and has significant market application value and industrial promotion significance. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The accompanying drawings provide a further understanding of the embodiments and are incorporated into and constitute a part of this specification. The accompanying drawings illustrate the embodiments and, together with the description, serve to explain the principles of the invention. Other embodiments and many of the intended advantages of the embodiments will be readily apparent as they become better understood by reference to the following detailed description. The elements of the drawings are not necessarily to scale with respect to each other. Like reference numerals designate corresponding similar parts.

[0034] Figure 1 This is a flow chart of a method for preparing freeze-dried kelp and egg drop soup cubes according to one embodiment of the present invention;

[0035] Figure 2 This is a process flow chart of a freeze-dried kelp egg drop soup cube according to one embodiment of the present invention;

[0036] Figure 3 The effect of the amount of kelp sprout added on sensory evaluation according to the present invention;

[0037] Figure 4 is the effect of the amount of egg added on sensory evaluation according to the present invention;

[0038] Figure 5 The effect of the amount of salt added on sensory evaluation according to the present invention;

[0039] Figure 6 The effect of the amount of starch added on sensory evaluation according to the present invention;

[0040] Figure 7 The effect of the amount of ginger added on sensory evaluation according to the present invention;

[0041] Figure 8 The effect of the amount of CMC-Na added on the sensory score according to the present invention;

[0042] Figure 9 The effect of the amount of kelp powder added according to the present invention on sensory scores;

[0043] Figures 10a-10b The DSC curve of the exothermic and endothermic processes of the tender sprout kelp and egg drop concentrated soup according to the present invention;

[0044] Figure 11 The curves of dry basis moisture content change during freeze-drying of soup cubes according to different processes of the present invention and the corresponding time of freeze-drying endpoint;

[0045] Figure 12 This is the transverse relaxation time T2 inversion spectrum of freeze-dried soup cubes made according to different processes of the present invention. DETAILED DESCRIPTION

[0046] The following will be combined with the accompanying drawings of the present invention to clearly and completely describe the technical solutions in the embodiments. Similar component numbers in the drawings represent similar components. Obviously, the embodiments described below are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0047] It will be understood that when used in this specification and the appended claims, the terms “comprises” and “comprising” indicate the presence of described features, integers, steps, operations, elements and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups thereof.

[0048] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the present invention. As used in the specification and appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms unless the context clearly indicates otherwise.

[0049] In the first aspect, the present invention provides a method for preparing freeze-dried kelp egg drop soup cubes, such as Figure 1 As shown, the preparation method of the freeze-dried kelp egg drop soup cube comprises:

[0050] S100, soup cooking: dissolve carboxymethyl cellulose sodium (CMC-Na) in boiling water to form a solution with a mass concentration of 0.175%-0.475%, add ginger and cook for 1-3 minutes, then add pretreated kelp segments and cook for 1-5 minutes to separate the kelp segment raw material and soup.

[0051] In some specific embodiments, before step S1, the method further includes desalting the salted kelp and then cutting it into segments to obtain kelp segments; and beating eggs to prepare egg liquid.

[0052] S200, soup base processing, slowly adding the pre-treated egg liquid to the stirring soup liquid, cooking for 2-5 minutes, adding onions, salt, starch, monosodium glutamate, and kelp powder to prepare the finished soup base, separating the finished soup base to obtain the original soup and soup base raw materials;

[0053] S300, forming and drying, the soup material, the kelp segment material and the original soup are subjected to rotary evaporation to obtain concentrated soup, which is mixed and pre-frozen in a mold, and then vacuum-freeze-dried to obtain freeze-dried kelp egg drop soup cubes.

[0054] In some specific embodiments, step S300 includes:

[0055] S310, concentrating the original soup by rotary evaporation at a vacuum degree of -0.10 to -0.08 MPa to 45-55% of the original volume to obtain a concentrated soup, preferably concentrating to 50% at a vacuum degree of -0.09 MPa;

[0056] S320, after the concentrated soup, kelp segment raw materials and soup base raw materials are molded, placed in a refrigerator for pre-freezing for more than 12 hours, transferred to a vacuum freeze dryer, further pre-frozen at a pre-freezing temperature of -20°C for 1-2 hours, vacuum frozen at a sublimation temperature of -5 to -4.8°C, and dried at a temperature of 50-70°C to a moisture content of ≤4%, thereby preparing freeze-dried kelp egg drop soup cubes.

[0057] In some specific embodiments, the temperature increase scheme of the vacuum freeze-drying process in S320 includes:

[0058] S321, prefreezing stage, maintained at -20 °C for 1 h;

[0059] S322, first sublimation stage, start vacuum 20Pa, increase temperature to -10℃ at a rate of 0.5℃ / min, and maintain for 2h;

[0060] S323, the second sublimation stage, heating to -5°C at a rate of 0.3°C / min for 2 h;

[0061] S324, the analytical drying stage, heating to 60°C at a rate of 1°C / min, maintaining the vacuum degree at 10 Pa, and drying to a moisture content of ≤4% to obtain freeze-dried kelp egg drop soup cubes.

[0062] In a second aspect, an embodiment of the present invention provides a freeze-dried kelp and egg drop soup cube, which is prepared by the preparation method described in the first aspect.

[0063] In some specific embodiments, the freeze-dried kelp egg drop soup cubes include the following ingredients in parts by weight: 16-80 parts kelp, 40-104 parts eggs, 0.2-3.4 parts salt, 0.8-2.4 parts starch, 2-18 parts ginger, 0.6-3.8 parts sodium carboxymethyl cellulose, 1.0-1.4 parts monosodium glutamate, and 1.4-1.8 parts chopped green onions, wherein the kelp is tender kelp.

[0064] In some specific embodiments, the freeze-dried kelp egg drop soup cube further comprises 0.05-0.4 parts of kelp powder.

[0065] In some specific embodiments, the freeze-dried kelp egg drop soup cubes are composed of the following raw materials in parts by weight: 64 parts of kelp, 56 parts of eggs, 2.6 parts of salt, 1.2 parts of starch, 10 parts of ginger, 1.4 parts of sodium carboxymethyl cellulose, 0.05-0.1 parts of kelp powder, 1.2 parts of MSG, and 1.6 parts of chopped green onions.

[0066] Example

[0067] The freeze-dried kelp egg drop soup cubes are composed of the following raw materials in parts by weight: the added amounts of tender kelp are 16, 32, 48, 56, 64, 72 and 80 parts respectively; the added amounts of eggs are 40, 56, 72, 88 and 104 parts respectively; the added amounts of salt are 0.2, 1.0, 1.8, 2.6, 3 and 3.4 parts respectively; the added amounts of starch are 0.8, 1.2, 1.6, 2.0 and 2.4 parts respectively; the added amounts of ginger are 2, 6, 10, 14 and 18 parts respectively; the added amounts of CMC-Na are 0.6, 1.4, 1.8, 2.2, 3.0 and 3.8 parts respectively; the added amounts of tender kelp powder are 0, 0.05, 0.1, 0.2, 0.3 and 0.4 parts respectively; monosodium glutamate is 1.2 parts; and chopped green onion is 1.6 parts, wherein 1 part by weight corresponds to 1g.

[0068] Its preparation method reference Figure 2 , Figure 2 A process flow chart of freeze-dried kelp and egg drop soup cubes according to an embodiment of the present invention is shown. As shown in the figure, the process flow chart of freeze-dried kelp and egg drop soup cubes includes the following steps:

[0069] Step 201: Add 800-1000 mL of water to a pot, boil the water, add CMC-Na and stir until it is completely dissolved, then add washed ginger and cook for 1 minute to obtain soup base 1.

[0070] Step 202: Select frozen, salted young kelp sprouts of good appearance and similar size, rinse the surface with tap water until no salt particles remain, and then rinse thoroughly with clean water. Take an appropriate amount of the cleaned young kelp sprouts, soak them in tap water, and continuously rinse with a small amount of running water, changing the water every 3 hours. Soak for 12 hours to desalinate, removing most of the salt and obtaining desalted kelp. Wipe the desalted kelp dry and cut into 5 cm long, uniform strips, i.e., kelp segments. Add the kelp segments to soup base 1 and cook for 2 minutes to obtain soup base 2.

[0071] Step 203: Separate the kelp segments from the soup base 2 to obtain the kelp segment raw material, and set aside for later use.

[0072] In step 204, the eggs are beaten into a liquid egg and slowly poured into the boiling soup base 2, stirring while pouring to form an egg drop. The egg drop is then cooked for 3 minutes until the egg drop is solidified. Salt, starch, monosodium glutamate, chopped green onions, and kelp powder are then added and stirred evenly to prepare the finished soup base. The kelp powder is prepared by drying young kelp sprouts in a 60°C oven with hot air, grinding them into a powder, and filtering them through a 200-mesh sieve.

[0073] In step 205, the finished soup stock is separated into stock and stock ingredients. The stock is poured into a round-bottom flask and rotary evaporated until the stock is reduced to 50% of its original mass to obtain a concentrated soup. The concentrated soup is mixed with the reserved kelp segments from step 203 and the stock ingredients separated from the finished soup stock from step 204, and then placed in a mold. The mixture is then pre-frozen in a refrigerator for at least 12 hours, then transferred to a vacuum freeze dryer and further pre-frozen at -20°C for 1-2 hours.

[0074] In step 206, the pre-frozen soup stock is subjected to vacuum freeze drying to obtain freeze-dried kelp and egg drop soup cubes. The sublimation temperature of the vacuum freeze drying is -5°C, and the freeze drying desorption temperatures are set at 50°C, 60°C, and 70°C, respectively.

[0075] Single-factor experiments, orthogonal experiments, and sensory evaluations were carried out on the freeze-dried kelp and egg drop soup cubes prepared in the examples. The optimal freeze-drying process for the freeze-dried kelp and egg drop soup cubes was determined by measuring the eutectic point and eutectic point of the concentrated kelp and egg drop soup before pre-freezing, as well as the freeze-drying time, moisture content, sensory score, texture characteristics, and moisture distribution of the product.

[0076] refer to Figure 3 , Figure 3 The effect of the amount of kelp sprout added according to the present invention on sensory evaluation is shown. As the key raw material of freeze-dried kelp sprout egg drop soup cubes, the amount of kelp sprout added has a significant impact on product quality. Figure 3 It can be seen that as the amount of kelp sprouts added increases, the sensory score shows a trend of first rising and then falling. When the addition amount is 16g, the sensory score is the lowest. This is because the amount of kelp sprouts added is too small, the taste of the kelp sprouts in the soup is not obvious, the soup cubes mainly have the texture of egg drop soup, and the appearance and flavor are simple, resulting in low taste and flavor scores. When the addition amount reaches 80g, the excessive kelp sprouts make the soup cubes dark in color, and some kelp extends beyond the range of the soup cube wrapping, resulting in irregular shape of the soup cubes, affecting the appearance. When the amount of kelp sprouts added is 64g, the sensory score is the highest. At this time, the appropriate amount of kelp sprouts makes the soup cubes more plump, rich in color, and diverse in flavor, making them more likely to be favored by consumers.

[0077] refer to Figure 4 , Figure 4 The effect of the amount of egg added according to the present invention on sensory evaluation is shown. Eggs are one of the main ingredients of freeze-dried kelp and egg drop soup cubes, and the amount of egg added is crucial to the sensory evaluation of the soup cubes. An appropriate amount of egg can improve the color, flavor and taste of the soup cubes, enhance the product's appeal, and is also an important filler to maintain the shape of the soup cubes. Figure 4As can be seen, sensory scores did not show a clear trend with increasing egg addition. This may be due to varying levels of egg acceptance among sensory evaluators: some felt that adding eggs enhanced the soup's eggy flavor, while others felt that the added eggy flavor overshadowed the delicate fragrance of the young kelp sprouts. Taking all these factors into consideration, 56g, which had the highest sensory score, was selected as the optimal egg addition amount.

[0078] Continue to refer Figure 5 , Figure 5 The effect of the amount of salt added on sensory evaluation according to the present invention is shown. Figure 5 As shown, as the amount of salt added increases, the sensory score initially increases and then decreases. The sensory score reaches its highest value when the salt addition level is 2.6g. Among the sensory evaluation indicators, the effect of salt addition on the taste score is the most significant, indicating that salt serves primarily as a flavoring in this product.

[0079] refer to Figure 6 , Figure 6 The effect of the amount of starch added according to the present invention on sensory evaluation is shown. The present invention uses cassava starch, which can make the soup cube structure firm and have good rehydration dispersibility. Figure 6 As can be seen, as the amount of starch added increased, the sensory score first increased and then decreased. When the starch addition level was 2.4g, the sensory score was significantly lower than the other groups. This is because the excessive starch addition resulted in a strong starchy flavor in the soup. There were no significant differences between the other addition levels, so the 1.2g starch addition level, which had the highest sensory score, was selected as the optimal starch addition level.

[0080] refer to Figure 7 , Figure 7 The effect of ginger addition on sensory evaluation according to the present invention is shown. The fishy smell of kelp is the main reason why some consumers do not accept kelp. Although the fishy smell of young kelp is lighter than that of mature kelp, it still needs to be deodorized to improve the flavor and eating experience. Figure 7 As shown, sensory scores initially increased and then decreased with increasing ginger addition. While an appropriate amount of ginger can remove the fishy smell and enhance the flavor, an excessive amount can make the soup too spicy, masking the aroma of other ingredients and disrupting the overall flavor balance. Therefore, the optimal ginger addition level of 10g, which gave the highest sensory score, was selected.

[0081] Further references Figure 8 , Figure 8 The effect of the amount of CMC-Na added according to the present invention on the sensory score is shown. In the production process of freeze-dried kelp and egg drop soup cubes, the addition of CMC-Na helps the soup cubes to form, improve stability, and make the soup richer and more flavorful. Figure 8As can be seen, as the amount of CMC-Na added increases, the sensory scores initially increase and then decrease. When the amount of CMC-Na added is too low, the stability of the soup cubes is limited, and the cubes are fragile. However, when the amount is too high, the cubes clump together, becoming difficult to dissolve and the soup tastes too sticky. Overall, the product acceptance is higher when the amount of CMC-Na added is 1.4g.

[0082] refer to Figure 9 , Figure 9 The effect of the amount of kelp sprout powder added according to the present invention on the sensory score is shown. The flavor of the kelp sprout will be weakened after freeze-drying, which may lead to insufficient kelp flavor in the soup cubes, which is easily masked by the flavor of other ingredients. However, adding too much kelp sprout will make the soup cubes dark in color and irregular in shape. Therefore, grinding the kelp sprout into powder as a seasoning can increase the flavor of the soup cubes without affecting the appearance. Figure 9 As shown, as the amount of kelp powder added increased, the sensory scores initially increased and then decreased. When 0.1g of kelp powder was added, the sensory score was significantly higher than that of the control group without kelp powder. While adding a moderate amount of kelp powder can enhance the flavor and taste of the broth, adding too much can turn the broth dark green, reducing appetite, and creating an unpleasant overpowering flavor. It can also make the broth too sticky, affecting its delicate texture and balance.

[0083] Based on single-factor experiments, we selected kelp powder (A), CMC-Na (B), salt (C), and kelp (D) additions as key factors influencing the performance of freeze-dried kelp egg drop soup cubes. We then conducted an orthogonal experiment using the optimal extensions of each single-factor experiment. The results are shown in Table 1. The range analysis in Table 1 shows that the order of factors influencing the sensory evaluation of kelp egg drop soup cubes is CMC-Na addition > kelp addition > kelp powder > salt. Based on the K and R values, the optimal formula for kelp egg drop soup cubes is A1B2C2D2, with 0.05g of kelp powder, 1.4g of CMC-Na, 2.6g of salt, and 64g of kelp. In Table 1, Group 2 had the highest sensory score, with a score of 86.84, higher than the other groups, consistent with the results obtained from the K and R values. Therefore, A1B2C2D2 was determined to be the optimal combination, and the formulation parameters for the freeze-dried kelp sprout soup cubes were 0.05g of kelp powder, 1.4g of CMC-Na, 2.6g of salt, and 64g of freeze-dried kelp sprouts.

[0084] Table 1 Orthogonal test results of the recipe of tender kelp and egg drop soup cube

[0085]

[0086]

[0087] The optimal recipe, derived from orthogonal optimization, was: 0.05g of kelp powder, 1.4g of CMC-Na, 2.6g of salt, and 64g of kelp. The sensory scores of the freeze-dried kelp egg drop soup cubes in three replicates were 84.91, 86.77, and 86.95, with an average of 86.21. The relative error compared to the orthogonal experiment's result (sensory score of 86.84) under the same conditions was 0.73%. This demonstrates the high reproducibility of the optimal process parameters derived from the orthogonal experiment. The optimal recipe for freeze-dried kelp sprout egg drop soup cubes was determined through single-factor and orthogonal experiments: 1.4g CMC-Na, 0.05g kelp sprout powder, 64g kelp sprout, 2.6g salt, 10g ginger, 56g egg, 1.2g starch, 1.2g MSG, and 1.6g chopped green onion. The kelp sprout egg drop soup cubes prepared using this recipe exhibit a well-structured, loose interior that resists breakage and discoloration, maintaining a vibrant, appetizing color. After rehydration, the soup is rich, smooth, and delicious, with a full flavor and the unique kelp flavor. The raw materials are inexpensive, making it a healthy and delicious instant soup with great development prospects.

[0088] Furthermore, the tender sprout kelp egg drop concentrated soup prepared with the above optimal formula was freeze-dried by setting the temperature of the parsing stage to 50, 60, and 70°C according to the programmed temperature scheme in Table 2 to obtain tender sprout kelp egg drop soup cubes for subsequent experiments.

[0089] Table 2 Vacuum freeze drying program temperature rise scheme

[0090]

[0091]

[0092] During the pre-freezing stage, setting the correct temperature helps ensure that moisture is evenly distributed throughout the material, forming finer ice crystals. This is crucial for improving the quality of freeze-dried products. If the pre-freezing temperature is too high, the ice crystals may become too large, increasing the porosity of the product during the freeze-drying process and affecting the appearance and structure of the final product. Therefore, it is necessary to analyze the physical properties of the material, such as the eutectic point and eutectic point, and optimize the freeze-drying process accordingly. The final temperature of the material pre-freezing is generally 5-10°C lower than the eutectic point. The sublimation drying temperature is based on the eutectic point. While avoiding melting and disintegration of the soup cube, the sublimation interface temperature should be increased as much as possible to speed up the drying process and reduce the energy consumption of freeze-drying. During the exothermic process, the end point of the last exothermic peak corresponds to the eutectic point; during the endothermic process, the starting point of the first endothermic peak corresponds to the eutectic point. Figure 10a and Figure 10bThe DSC curves of the exothermic and endothermic processes of the condensed kelp and egg drop soup of the present invention are shown respectively. Figure 10a and 10b As shown, the exothermic peak end point (eutectic point) of the tender sprout, kelp, and egg drop condensed soup is -12.6°C, and the endothermic peak start point (eutectic point) is -4.8°C. Based on this, it is recommended to set the optimal prefreezing temperature at -20°C and control the sublimation drying temperature below -4.8°C, that is, to -5°C. In production practice, food production plants are generally equipped with conventional freezers capable of reaching -20°C. This temperature is sufficient to meet the prefreezing requirements of the soup cube production involved in this study, so there is no need to build an additional prefreezing warehouse.

[0093] Table 3 Moisture content, breaking force, tissue morphology, and appearance sensory scores of tender kelp and egg drop soup cubes

[0094]

[0095] Continue to refer Figure 11 , Figure 11 The curves showing the change in dry basis moisture content during the freeze-drying process of soup cubes according to different processes of the present invention and the corresponding time of the freeze-drying endpoint are shown. Moisture content is a key factor affecting the quality of freeze-dried food. A lower moisture content can effectively extend the shelf life of food, inhibit microbial growth and enzyme activity, and prevent food from spoiling; at the same time, too high a moisture content will accelerate the oxidative decomposition of nutrients in freeze-dried food, reduce nutritional value, and affect rehydration. Generally speaking, it is more appropriate to control the moisture content of freeze-dried products at around 4%, because a final moisture content within the range of 3%-5% can effectively extend the shelf life of the product, which is crucial to the quality characteristics and stability of the product. Therefore, the freeze-drying endpoint of this freeze-drying process is set to 4%±0.5%. From Figure 11It can be seen that when the drying temperature is set to 50, 60, and 70°C, the time for the moisture content of the soup cube to reach 4% is 29.15, 27.12, and 26.9 hours, respectively. The freeze-drying endpoint time at a drying temperature of 50°C is significantly longer than that of the other two drying temperatures. As shown in Table 3, after the product is dried to absolute dryness, the moisture content of the 50°C group is significantly higher than that of the other two groups, indicating that the freeze-drying rate and freeze-drying capacity of the 50°C group are worse than those of the other two groups. The fracture force value of freeze-dried soup cubes is an important indicator for evaluating their texture characteristics. High fracture force indicates high hardness and dense structure, which means that the product is more resistant to mechanical damage during transportation or packaging, but the rehydration time may be longer. Low fracture force indicates that the product is crispy and fragile, rehydrates quickly, and has a light taste, which is suitable for products that require instant dissolution. However, it is easy to produce debris during transportation, affecting the appearance integrity and user experience. As can be seen from Table 3, the rupture force of the soup cubes in the 70℃ group was significantly higher than those in the other two temperatures, while the scores of the tissue morphology and appearance in the sensory evaluation were significantly lower in the 70℃ group than in the other two temperatures. This is because the temperature rose too quickly from sublimation to decomposition, causing the porous structure to be destroyed and the product to collapse. As a result, the rupture force increased abnormally and the sensory score decreased.

[0096] Table 4 Moisture distribution of freeze-dried soup cubes

[0097]

[0098] Figure 12 The transverse relaxation time T2 inversion maps of freeze-dried soup cubes according to different processes of the present invention are shown. The length of relaxation time and the corresponding signal amplitude displayed by the T2 inversion map can be used to quantitatively analyze the water phase and change process. According to the difference in peak area covered by the relaxation absorption peak of the water system at the transverse relaxation time T2, water is roughly divided into strongly bound water (1ms>T2>0.1ms), weakly bound water (10ms>T2>1ms), non-flowing water (100ms>T2>10ms) and free water (T2>100ms). Strongly bound water and weakly bound water can be collectively referred to as bound water, which refers to water that is very tightly bound to molecular structures (such as cell walls, proteins, etc.), has the lowest degree of freedom, and is generally difficult to remove. By Figure 12As shown in Table 4, the bound water content of the final broth cubes increases with increasing temperature. The 50°C broth cubes had the lowest bound water content, significantly lower than the other broth cubes. Non-mobile water is typically strongly bound to solid components (such as proteins and sugars) in a substance, making it, like bound water, less susceptible to volatilization or migration. A higher proportion of non-mobile water can increase the stability of freeze-dried products during storage and transportation and reduce their potential for microbial utilization. The three broth cubes in the table all had the highest proportion of non-mobile water among all water forms, indicating that all three groups have good resistance to spoilage. Free water refers to the water content in a freeze-dried product that is not bound to solid components. This water content significantly impacts the quality and stability of freeze-dried products and is one of the most important indicators of freeze-dried products. A high free water content can promote microbial growth in food, increasing the risk of spoilage and spoilage. From the data in the table, we can see that as the parsing temperature increases, the proportion of free water in the soup cubes decreases accordingly. The free water content in the 50℃ group is the highest and is significantly different from that in the other groups, indicating that the risk of deterioration and corruption in the 50℃ group is higher than that in the other two groups, and its safety is poor.

[0099] The eutectic point of concentrated soup is -12.6°C, and the eutectic point is -4.8°C. The optimal pre-freezing temperature should be -20°C, and the sublimation temperature should be -5°C. When the desorption temperature was set at 50, 60, and 70°C, the time for the soup cubes to reach 4% moisture was 29.15, 27.12, and 26.9 hours, respectively. The freeze-drying endpoint time at 50°C was significantly longer than at the other two desorption temperatures, and the freeze-drying rate was the slowest. The rupture force of the soup cubes at 70°C was significantly higher than at the other two temperatures, while the sensory evaluation scores for both morphology and appearance were significantly lower at 70°C. The 50°C group had the lowest percentage of bound water and the highest percentage of free water, indicating that the risk of deterioration and corruption in the 50°C group was higher than that in the other two groups, indicating poor safety. In summary, the pre-freezing temperature for freeze-dried kelp sprout and egg drop soup cubes is -20°C, the sublimation temperature is -5°C, and the freeze-drying desorption temperature is set at 60°C. Under this temperature group, the freeze-drying rate of soup cubes is fast, the sensory quality is excellent, and the rehydration property is good.

[0100] Obviously, those skilled in the art can make various modifications and changes to the embodiments of the present invention without departing from the spirit and scope of the present invention. In this way, if these modifications and changes are within the scope of the claims of the present invention and their equivalents, the present invention is also intended to cover these modifications and changes. The word "comprising" does not exclude the presence of other elements or steps not listed in the claims. The simple fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be considered as limiting the scope.

Claims

1. A freeze-dried kelp egg drop soup cube, characterized in that: The invention comprises the following raw materials in parts by weight: 16-80 parts of kelp, 40-104 parts of eggs, 0.2-3.4 parts of salt, 0.8-2.4 parts of starch, 2-18 parts of ginger, 0.6-3.8 parts of sodium carboxymethyl cellulose, 1.0-1.4 parts of monosodium glutamate, and 1.4-1.8 parts of chopped green onion.

2. The freeze-dried kelp egg drop soup cube according to claim 1, characterized in that: The kelp is tender sprout kelp.

3. The freeze-dried kelp egg drop soup cube according to claim 1, characterized in that: The freeze-dried kelp egg drop soup cubes also include 0.05-0.4 parts of kelp powder, which is prepared by drying kelp with hot air at 55-65° C. and then crushing it through a 180-220 mesh sieve. Preferably, the kelp powder is prepared by drying young kelp with hot air at 60° C. and then crushing it through a 200 mesh sieve.

4. The freeze-dried kelp egg drop soup cube according to claim 1, characterized in that The invention is composed of the following raw materials by weight: 64 parts of kelp, 56 parts of eggs, 2.6 parts of salt, 1.2 parts of starch, 10 parts of ginger, 1.4 parts of sodium carboxymethyl cellulose, 0.05-0.1 parts of kelp powder, 1.2 parts of monosodium glutamate, and 1.6 parts of chopped green onions.

5. The freeze-dried kelp egg drop soup cube according to claim 1, characterized in that: The starch is tapioca starch.

6. The method for preparing the freeze-dried kelp and egg drop soup cube according to any one of claims 1 to 5, characterized in that: The preparation method comprises: S1, cooking soup, dissolving sodium carboxymethyl cellulose in 800-1000 mL of boiling water, adding ginger and cooking for 1-3 minutes, adding pretreated kelp segments, cooking for 1-5 minutes, and separating the kelp segment raw material and soup; S2, soup base processing, slowly adding the pre-treated egg liquid to the stirring soup liquid, cooking for 2-5 minutes, adding chopped green onion, salt, starch, monosodium glutamate, and kelp powder to prepare a finished soup base, separating the finished soup base to obtain the original soup and soup base raw materials; S3, forming and drying, the original soup is subjected to rotary evaporation to obtain concentrated soup, the soup material, the kelp segment material and the concentrated soup are mixed and molded for pre-freezing, and then vacuum freeze-dried to obtain the freeze-dried kelp egg drop soup cubes.

7. The method for preparing freeze-dried kelp and egg drop soup cube according to claim 6, characterized in that: Before the step S1, the method further includes desalting the salted kelp, drying and cutting the kelp into 3-6 cm strips to obtain the kelp segments; and beating eggs to prepare the egg liquid.

8. The method for preparing freeze-dried kelp and egg drop soup cube according to claim 6, characterized in that: The S3 step includes: S31, concentrating the original soup by rotary evaporation at a vacuum degree of -0.10 to -0.08 MPa to 45-55% of the original volume to obtain the concentrated soup; S32, after the concentrated soup, the kelp segment raw material and the soup base raw material are molded, they are placed in a refrigerator for pre-freezing for more than 12 hours, transferred to a vacuum freeze dryer, further pre-frozen at a pre-freezing temperature of -20°C for 1-2 hours, vacuum frozen at a sublimation temperature of -5 to -4.8°C, and freeze-dried and analyzed at 50-70°C until the moisture content is ≤4%, thereby obtaining the freeze-dried kelp egg drop soup cubes.

9. The method for preparing freeze-dried kelp and egg drop soup cube according to claim 8, characterized in that: The temperature raising scheme of the vacuum freeze drying procedure of S32 includes: S321, prefreezing stage, maintained at -20 °C for 1 h; S322, first sublimation stage, start vacuum 20Pa, increase temperature to -10℃ at a rate of 0.5℃ / min, and maintain for 2h; S323, the second sublimation stage, heating to -5°C at a rate of 0.3°C / min for 2 h; S324, the analytical drying stage, heating to 60°C at a rate of 1°C / min, maintaining the vacuum degree at 10Pa, and drying to a moisture content of ≤4%, thereby obtaining the freeze-dried kelp egg drop soup cubes.

10. Use of the freeze-dried kelp and egg drop soup cube according to any one of claims 1 to 5 or the freeze-dried kelp and egg drop soup cube prepared by the method for preparing the freeze-dried kelp and egg drop soup cube according to any one of claims 6 to 9 in preparing instant soups.

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