A runny yolk tea leaf egg and a preparation method thereof

Abstract

This invention discloses a soft-boiled tea egg and its preparation method. The preparation method includes: rapidly cooling the eggs after high-temperature boiling using sterile air at 19.5~20.5℃ to close the micropores of the eggshell and reduce subsequent microbial contamination; adding a compound antibacterial agent composed of ε-polylysine hydrochloride, nisin, and lysozyme to the brine; constructing an isothermal processing system that controls the entire process—from cooling endpoint, brine storage, vacuum filling, and water bath sterilization—at 66.0~68.0℃, and simultaneously performing hot filling with the shell under vacuum negative pressure. This invention achieves a 90-day shelf life at room temperature for pre-packaged soft-boiled tea eggs by constructing a synergistic sterilization barrier of "gentle heat + biological preservation," without exceeding the yolk coagulation threshold and perfectly preserving the natural liquid soft-boiled texture and tender taste.

Description

Technical Field

[0001] This invention belongs to the field of food processing technology, and in particular relates to a soft-boiled tea egg and its preparation method. Background Technology

[0002] Most existing tea egg products are made from fully cooked eggs, which have hard egg whites and coarse yolks. They are dry and hard to eat. Furthermore, the high-temperature sterilization process leads to nutrient loss and a dull, grayish-yellow yolk color, resulting in poor overall quality and low perceived value for the tea egg products. Although they can be stored at room temperature for 6 months after high-temperature sterilization, making them easy to store and transport, market demand is gradually decreasing.

[0003] Soft-boiled eggs are eggs cooked until the egg white is completely set and the yolk is a soft, orange-yellow runny yolk. This method better preserves the original flavor of the egg, resulting in a delicate and smooth texture that is more popular with consumers. To improve the texture, "soft-boiled egg" products (i.e., eggs with a completely set egg white and a soft, orange-yellow yolk) have appeared on the market. However, most of these are simply shelled soft-boiled eggs that have been marinated. Because there is no eggshell to protect them, the egg white loses more water during the marinating process, resulting in a firmer, more bouncy texture. Furthermore, the edges of the yolk are prone to overcooking, losing the unique aroma and consumer experience of traditional whole-shell tea eggs when peeled.

[0004] For the "soft-boiled tea eggs in their shells," which are more favored by consumers, the current market almost exclusively offers them in convenience stores or restaurants using a "made-to-order" model, making it difficult to achieve industrial-scale mass production of pre-packaged eggs. The fundamental reason lies in a significant physical-thermodynamic contradiction in the pre-packaged production of soft-boiled tea eggs: the critical temperature for the yolk's coagulation is 69-70℃. To preserve the authentic "soft-boiled" texture, traditional industrial high-temperature, high-pressure sterilization equipment cannot be used; however, conventional low-temperature, gentle sterilization methods are ineffective in killing heat-resistant microorganisms and spores due to the micropores and susceptibility to contamination on the eggshell surface, leading to easy spoilage. Therefore, limited by sterilization technology, existing soft-boiled tea eggs in their shells cannot operate outside of a cold chain system, and long-term storage and distribution at room temperature are impossible, severely restricting the development of this product. Summary of the Invention

[0005] The purpose of this invention is to overcome the technical difficulties in the existing technology, namely, that "conventional pre-packaged tea eggs are tough and dry" and that "soft-boiled tea eggs in their shells can only be made and sold immediately due to limitations in sterilization technology, and cannot have a long shelf life at room temperature." This invention provides a method for preparing soft-boiled tea eggs, which constructs a non-thermal sterilization barrier technology that combines a "67℃ isothermal processing system" with "multi-target biological compound antibacterial" technology. Without exceeding the critical point of yolk ripening, it preserves the orange-yellow soft-boiled texture and the natural tender taste of the shell, and also achieves a shelf life of up to 90 days at room temperature for pre-packaged soft-boiled tea eggs in their shells.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A method for preparing soft-boiled tea eggs includes the following steps:

[0008] Step 1: Raw Egg Processing

[0009] Select standard raw eggs that are safe to eat raw, with a single egg weight of 55-60g, and sterilize and disinfect the raw eggs.

[0010] Step 2: Precise high-temperature cooking

[0011] Place the raw eggs from step 1 in water and boil them at a temperature of 96.5~97.5℃ for 6.5~7.5 minutes.

[0012] Step 3: Aseptic air-cooling sterilization

[0013] The eggs cooked in step 2 are cooled using sterile clean air until the core temperature reaches 66.0~68.0℃.

[0014] Step 4: Isothermal brine preparation

[0015] Prepare a brine containing a compound antibacterial agent, and maintain the temperature of the brine at 66.0~68.0℃;

[0016] Step 5: Isothermal vacuum hot filling

[0017] The eggs obtained in step 3 and the brine obtained in step 4 are simultaneously vacuum-filled, with the temperature of the eggs and the brine controlled at 66.0~68.0℃.

[0018] Step 6: Gentle water bath sterilization and simultaneous osmosis

[0019] The product after filling in step 5 is sterilized in a water bath at a temperature of 66.5~67.5℃ for 44.0~46.0 min. Then it is cooled until the center temperature of the egg is below 40℃ to obtain soft-boiled tea eggs.

[0020] Preferably, in step 1, the raw eggs are selected from eggs laid 4-6 days ago, with a freshness HU≥80, and the total bacterial count of the raw eggs is controlled to be <100CFU / g.

[0021] Preferably, in step 2, the temperature is dynamically adjusted by an infrared thermometer during the cooking process to ensure that the temperature difference fluctuation of the water is ≤ ±0.5℃.

[0022] Preferably, in step 3, the temperature of the sterile clean air is 19.5~20.5℃, and the cooling time is 5.0~6.0min.

[0023] Preferably, in step 4, the ingredients of the brine include, by weight percentage: 3% brewed soy sauce, 3% edible salt, 3% Da Hong Pao tea leaves, 1% white sugar, 0.06% compound antibacterial agent, and the remainder purified water.

[0024] Preferably, the compound antibacterial agent comprises ε-polylysine hydrochloride, nisin, and lysozyme.

[0025] The present invention also provides a soft-boiled tea egg, wherein the tea egg is made by any of the preparation methods described above.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1. This invention employs an isothermal processing system maintained at 66.0~68.0℃ throughout the entire process, from cooling to brine storage, vacuum filling, and water bath sterilization. This constant temperature approaches but does not exceed the critical point of egg yolk coagulation. Combined with a compound antibacterial agent containing ε-polylysine hydrochloride, nisin, and lysozyme, a synergistic sterilization barrier of "mild heat + biological preservation" is constructed. The thermal environment at approximately 67℃ effectively kills vegetative microorganisms, while the compound antibacterial agent targets and destroys heat-resistant spores and residual bacterial cell structures. The synergistic effect of these two factors achieves a shelf life of up to 90 days at room temperature (25℃) for tea eggs while preserving the liquid, runny texture of the egg yolk.

[0028] 2. This invention uses sterile air at 19.5~20.5℃ to cool eggs after high-temperature cooking. Compared with traditional water cooling, gas phase cooling avoids the reverse penetration of microorganisms caused by water phase contact, promotes the contraction and closure of micropores on the eggshell surface, reduces the risk of external microorganisms penetrating into the egg through micropores in subsequent processes, thereby maintaining a low initial colony level and improving the stability of the overall preservation system.

[0029] 3. In this invention, both the eggs and the brine are vacuum-filled and bathed in the same temperature water at 67°C. With the help of vacuum negative pressure and the thermal molecular motion at 67°C, the flavor substances and antibacterial components of the brine penetrate the eggshell and egg membrane and permeate into the egg white. At the same time, retaining the eggshell reduces the outward loss of egg white moisture, improves the flavor absorption efficiency of the shell-on eggs, and the finished product has a high egg white moisture retention rate, a soft and tender texture, and maintains the integrity of the egg surface and easy peeling. Attached Figure Description

[0030] Figure 1 This is a product image of the soft-boiled tea egg from Embodiment 1 of the present invention after 90 days at room temperature;

[0031] Figure 2 This is a schematic diagram of a soft-boiled tea egg product with shell according to Embodiment 1 of the present invention. Detailed Implementation

[0032] The technical solutions in the embodiments of the present invention will be clearly and completely described below, so that those skilled in the art can better understand the advantages and features of the present invention, thereby making a clearer definition of the scope of protection of the present invention. The embodiments described in this invention are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0033] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments of the present invention. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0034] This invention provides a soft-boiled tea egg and its preparation method. The overall technical concept is as follows: Select raw eggs of a specific weight and with low initial bacterial count; employ high-temperature, short-time cooking to solidify the egg white while maintaining the soft-boiled yolk; subsequently, use sterile air cooling to reduce the risk of secondary contamination from the cooling medium; and control the temperature of key processes such as the cooling endpoint, temporary storage of the brine, vacuum filling, and water bath sterilization at approximately 67°C. This constant temperature is lower than the yolk's curdling point (69-70°C). Combined with a compound antibacterial agent and vacuum packaging, while maintaining the soft-boiled physical state of the yolk, conditions are achieved to kill and inhibit microbial growth, thus enabling the resulting soft-boiled tea egg to be stored at room temperature.

[0035] Example 1

[0036] This embodiment provides a method for preparing soft-boiled tea eggs, the overall steps of which are as follows:

[0037] Step 1: Raw Egg Pretreatment

[0038] The raw eggs are selected from our own farms and are suitable for raw consumption. The raw materials are controlled, and these eggs undergo strict management from chick breeding and raising to the production process. They also undergo sterilization and disinfection to ensure a total bacterial count of <100 CFU / g, meeting raw consumption standards. The eggs are used for 5 days from the laying date to guarantee freshness with a Haugh unit (HU) ≥80. Compared to regular eggs, there is no risk of Salmonella and no fishy smell. Furthermore, because the size of the eggs is not significantly different, the weight of each egg is strictly selected within the range of 57.5 ± 0.5 g / egg to ensure consistency in the soft-boiled texture during cooking.

[0039] Step 2: Precise high-temperature cooking

[0040] Place the raw eggs from step 1 into the cooking equipment, set the cooking temperature to 97.0℃ and the time to 7.0min; during the cooking process, the temperature is dynamically adjusted by an infrared thermometer and a PLC controller to ensure that the temperature difference fluctuation is ≤±0.5℃, so that the egg white is completely solidified and the yolk is orange-yellow and soft.

[0041] Step 3: Aseptic air-cooling sterilization

[0042] After boiling in step 2, the eggs were quickly transferred into the air-cooling channel and cooled with sterile clean air at a temperature of 20.0℃ for 5.5 minutes, precisely cooling the eggs to 67.0℃. After testing, the total number of bacterial colonies inside the eggs after this step was <10 CFU / g.

[0043] Step 4: Isothermal brine preparation

[0044] Weigh the following ingredients by weight percentage: 3% brewed soy sauce, 3% edible salt, 3% Da Hong Pao tea leaves, 1% white sugar, 0.06% compound antibacterial agent (the compound antibacterial agent proportions are: ε-polylysine hydrochloride accounts for 0.04% of the total weight of the brine, nisin accounts for 0.01%, and lysozyme accounts for 0.01%), and the remainder is purified water.

[0045] Add water, tea leaves, and seasonings to a braising pot and bring to a boil over high heat. Maintain a simmer for 25 minutes, then filter through a 60-mesh filter. Cool the braising liquid through a plate heat exchanger and transfer it to a temporary storage container. Add a compound antibacterial agent and precisely control the temperature of the braising liquid to 67.0℃ for later use. The braising liquid must be used within 2 hours, and the total bacterial count must be controlled to be <10 CFU / g.

[0046] Step 5: Isothermal vacuum hot filling

[0047] The eggs obtained in step 3 at a temperature of 67.0℃ and the brine obtained in step 4 at a temperature of 67.0℃ are simultaneously vacuum-filled. The vacuum degree is -0.06MPa. The packaging specifications are 60g of brine per bag for each egg. The bags are sealed and the seals are checked to ensure they are flat, tight, and free of air bubbles.

[0048] Step 6: Gentle water bath sterilization and simultaneous osmosis

[0049] After filling, the products are placed in a water bath sterilizer within 20 seconds for sterilization. The sterilization temperature is set at 67.0℃ for 45.0 minutes. The sterilization time is based on the optimal window determined through heat penetration experiments using a single product weight of 55-60g, ensuring that the core temperature reaches the set value and is maintained for a sufficient lethal time. During sterilization, the temperature is dynamically adjusted using an infrared thermometer and a PLC controller to ensure that the temperature difference fluctuation is ≤±0.5℃, guaranteeing the sterilization effect. Thermodynamic penetration is used to accelerate the infusion of the brine; subsequently, the products are cooled with 20.0℃ cooling water until the core temperature drops below 40℃.

[0050] Example 2

[0051] The steps in Example 2 are basically the same as in Example 1, except for the different process parameters. The isothermal temperature throughout the entire process is uniformly set at 66.5℃ to verify the robustness of the isothermal system near its lower limit: In step 1, eggs with a single weight of 55.5 ± 0.5 g are selected. In step 2, the boiling water temperature is 96.5℃, and the boiling time is 7.5 min. In step 3, the aseptic air temperature is 19.5℃, and the cooling time is 5.0 min, allowing the eggs to cool to 66.5℃. In step 5, the vacuum degree is set to -0.05 MPa. In step 6, the water bath sterilization temperature is 66.5℃, and the time is 46 min.

[0052] The parameters in Example 2 should ensure that the temperature of all isothermal elements is completely consistent to verify the robustness of the isothermal system.

[0053] Example 3

[0054] The steps in Example 3 are basically the same as in Example 1, the difference being the different process parameters, and the isothermal temperature throughout the process is uniformly set at 67.5℃: In step 1, eggs with a single weight of 59.5±0.5g are selected. In step 2, the boiling water temperature is 97.5℃, and the boiling time is 6.5min. In step 3, the aseptic air temperature is 20.5℃, and the cooling time is 6.0min, to cool the eggs to 67.5℃. In step 6, the water bath sterilization temperature is 67.5℃, and the time is 44min.

[0055] Initial physicochemical, sensory, and microbiological comparative tests were conducted on the soft-boiled tea eggs prepared in Examples 1, 2, and 3 (day 0).

[0056] 1. Evaluation criteria: A panel of 5 food sensory evaluation experts will evaluate the product’s shell integrity, egg white state, yolk ripeness and flavor; microbiological indicators will be tested in accordance with GB 2749-2015.

[0057] 2. Test Result Recording

[0058]

[0059] 3. Data Analysis and Conclusions: The experimental results show that Example 1 is the optimal example. Examples 2 and 3, due to the use of the upper and lower limits of the parameter range of this invention, although showing slight differences in the runny texture of the egg yolk, did not exceed the critical point of complete yolk maturation and maintained excellent "soft-boiled" characteristics. Simultaneously, their initial microbial indicators all reached extremely low levels. This proves that the entire process parameter window of this invention is truly effective and has high industrialization value, meeting the prerequisites for long-term room temperature preservation.

[0060] Example 4

[0061] This embodiment tests and verifies the shelf life of the soft-boiled tea egg product from Embodiment 1 at room temperature (25°C).

[0062] ① The Q10 value was determined using the dual-test temperature method, and the shelf life was also determined.

[0063] ② Take the soft-boiled tea egg product prepared in Example 1 (taking the production batch of 2025.07.02 as an example), and put it into a constant temperature and humidity (RH75%) incubator at 37℃ and 47℃ respectively. At the same time, sample retention tests were also carried out under room temperature conditions. Sensory and microbiological determinations were performed on the samples in accordance with GB2749.

[0064] ③ Based on the shelf life test cycle being 1.25 times the expected shelf life, assuming a shelf life of 90 days at room temperature and a shelf life ratio Q10=2, then θ(25℃)=θ(37℃)*Q10ΔT / 10=90 days, the storage period at 37℃ is 39 days, and 1.25 times the shelf life is 49 days; θ(25℃)=θ(47℃)*Q10ΔT / 10=90 days, the storage period at 47℃ is 20 days, and 1.25 times the shelf life is 25 days.

[0065] Table 1: Test temperature: 37℃

[0066]

[0067] Table 2: Test temperature: 47℃

[0068]

[0069] Table 3: Test Temperature: 25℃

[0070]

[0071] ④ Data Analysis: Under dual-temperature test conditions, the egg yolk color darkens slightly after 55 days of storage at 37℃, indicating a shelf life of 50 days at 37℃; the egg yolk color darkens slightly after 27 days of storage at 47℃, indicating a shelf life of 25 days at 47℃. The shelf life ratio under dual-temperature testing can be confirmed as: Q10 = θ(37℃) / θ(47℃) = 2. Calculating θ(25℃) = θ(37℃) * Q10ΔT / 10 = 114 days, the actual shelf life at 25℃ is 112 days, which is close to the theoretical value.

[0072] ⑤ Conclusion: Experimental results show that under normal temperature conditions of 25℃, please refer to... Figures 1-2 The product of this invention maintains stable performance across all indicators within 112 days, and its actual shelf life fully covers the expected 90-day requirement. Figure 1 The results showed that the soft-boiled tea eggs, after being stored at room temperature for 90 days, still had perfectly orange-yellow runny yolks, without being overcooked or dried out.

[0073] As a preferred pre-shipment quality control measure, the cooled product can be placed in a constant temperature environment of 37°C and 75% RH for 3-7 days to remove defective products such as those with bulging bags due to packaging cracks or poor sealing. However, this step is not a necessary step in the preparation method, and the product can achieve the stated shelf life at room temperature without this treatment.

[0074] The descriptions and practices disclosed in this invention are readily apparent and understandable to those skilled in the art, and various modifications and refinements can be made without departing from the principles of this invention. Therefore, any modifications or improvements made without departing from the spirit of this invention should also be considered within the scope of protection of this invention.

Claims

1. A method for preparing soft-boiled tea eggs, characterized in that, Includes the following steps: Step 1: Raw Egg Processing Select standard raw eggs that are safe to eat raw, with a single egg weight of 55-60g, and sterilize and disinfect the raw eggs. Step 2: Precise high-temperature cooking Place the raw eggs from step 1 in water and boil them at a temperature of 96.5~97.5℃ for 6.5~7.5 minutes. Step 3: Aseptic air-cooling sterilization The eggs cooked in step 2 are cooled using sterile clean air until the core temperature reaches 66.0~68.0℃. Step 4: Isothermal brine preparation Prepare a brine containing a compound antibacterial agent, and maintain the temperature of the brine at 66.0~68.0℃; Step 5: Isothermal vacuum hot filling The eggs obtained in step 3 and the brine obtained in step 4 are simultaneously vacuum-filled, with the temperature of the eggs and the brine controlled at 66.0~68.0℃. Step 6: Gentle water bath sterilization and simultaneous osmosis The product after filling in step 5 is sterilized in a water bath at a temperature of 66.5~67.5℃ for 44.0~46.0 min. Then it is cooled until the center temperature of the egg is below 40℃ to obtain soft-boiled tea eggs.

2. The preparation method according to claim 1, characterized in that, In step 1, the raw eggs are selected from eggs laid 4-6 days ago, with a freshness HU≥80, and the total bacterial count of the raw eggs is controlled to be <100CFU / g.

3. The preparation method according to claim 1, characterized in that, In step 2, the temperature is dynamically adjusted using an infrared thermometer during the cooking process to ensure that the temperature difference fluctuation is ≤ ±0.5℃.

4. The preparation method according to claim 1, characterized in that, In step 3, the temperature of the sterile clean air is 19.5~20.5℃, and the cooling time is 5.0~6.0min.

5. The preparation method according to claim 1, characterized in that, In step 4, the ingredients of the braising liquid include, by weight percentage: 3% brewed soy sauce, 3% edible salt, 3% Da Hong Pao tea leaves, 1% white sugar, 0.06% compound antibacterial agent, and the remainder purified water.

6. The preparation method according to claim 5, characterized in that, The compound antibacterial agent contains ε-polylysine hydrochloride, nisin, and lysozyme.

7. A soft-boiled tea egg, characterized in that, The tea eggs are made by any one of the preparation methods described in claims 1 to 6.

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