Preparation method of low-salt dry-boiled heart dried abalones and three-microbe compound fermentation method thereof

Abstract

The present application relates to the technical field of aquatic dried food processing, and particularly relates to a preparation method of low-salt soft-core dried abalone and a three-microbe compound fermentation method thereof. In the present application, endogenous protease and exogenous three-microbe extracellular enzyme are used to sequentially and cooperatively degrade the protein of the abalone column in layers, so that a complete and permeable amber soft-core structure can be formed in each finished product, and defects such as solid hard core and local soft core are eliminated. The rate of superior products of the finished product soft core is increased from about 65% in the traditional process to more than 95%, and the added value of the product is significantly improved. At the same time, with the synergistic effect of the differential metabolic pathways of Pediococcus pentosaceus, Lactobacillus plantarum and Kluyveromyces marxianus, the characteristic aroma of the original fresh sweetness and amber caramel of the abalone is enriched in a targeted manner, and the adverse flavors such as sour and dirty smell generated by the traditional natural and disordered fermentation are effectively eliminated. After the finished product is rehydrated, the soft core is full of gelatinous, soft and sticky, and the overall sensory quality is better than that of the traditional sun-dried abalone products on the market.

Description

Technical Field

[0001] This invention relates to the field of dried aquatic food processing technology, and in particular to a method for preparing low-salt soft-boiled dried abalone and its three-strain compound fermentation method. Background Technology

[0002] Existing abalone processing technology suffers from four major industry pain points, hindering the stable industrial production of high-quality abalone: 1. Traditional natural sun-drying combined with spontaneous fermentation by environmental microorganisms results in an uncontrollable microbial community: Traditional dried abalone relies on ambient airborne bacteria for spontaneous maturation after drying. The system is mixed with Aspergillus, Penicillium, and histamine-producing spoilage bacteria, resulting in a spoilage rate of over 22% for moldy, sour, and unusable finished products. The disordered metabolism of these bacteria produces a strong earthy and fishy smell, with a weak natural abalone aroma. There are also significant differences in the color, texture, and softness between batches. The entire process involves sun-drying for 30 to 60 days and natural post-fermentation for more than 2 years, which is entirely dependent on sunny weather. Production is impossible on rainy days, making it impossible to achieve continuous industrial mass production throughout the year.

[0003] 2. Existing industrial processes without exogenous microbial strains rely solely on the abalone's endogenous enzymes for autolysis, resulting in poor soft-boil formation and low uniformity. A few industrialized processes on the market do not add exogenous fermentation bacteria, but rely solely on the abalone's own endogenous proteases to slowly degrade myofibril protein. The protein decomposition efficiency is low, and the proportion of translucent and soft-bodied adductor muscle is less than 60%. Due to the differences in the endogenous enzyme activity of individual abalone, a large number of finished products in the same batch have solid cores, hard cores, local soft-bodied parts, and inconsistent color, with the rate of superior products being less than 65%.

[0004] 3. Existing fermentation strains have poor adaptability and cannot simultaneously meet the requirements for promoting soft core formation in low-salt, low-moisture dry curd environments: Existing aquatic fermentation systems only use a single Lactobacillus plantarum strain or a combination of Lactobacillus plantarum and Saccharomyces cerevisiae. Both strains have weak tolerance to low salt and low moisture content, making it difficult for them to colonize the surface of dried abalone. The metabolic pathways of the microbial community are disordered, which easily produces a sour and rancid odor. They can only achieve basic preservation and cannot selectively degrade collagen to enrich the soft core and generate an amber sweet aroma. The three requirements of antibacterial, quality improvement and aroma enhancement cannot be met simultaneously.

[0005] Meanwhile, existing fermentation processes generally use 10% to 30% high salt for pickling. High salt content inhibits the activity of microbial proteases, hinders the formation of soft center, and the finished product has excessive sodium content, which does not meet the modern demand for salt reduction and healthy consumption.

[0006] 4. The existing drying process is a single constant temperature drying, which cannot form a layered, soft-on-the-outside, loose-on-the-inside structure: Conventional constant temperature drying simply removes surface moisture, and the rate at which moisture migrates from the inside out is uncontrollable. This can easily result in a hard, dry outer shell and a sticky, wet interior, or excessive dehydration leading to a tough, dry texture. It is difficult to stably form the unique texture of amber with a dense outer layer and a semi-fluid, soft center. Furthermore, the lack of waste heat recovery design results in high energy consumption during production.

[0007] In summary, existing technologies lack a complete industrial process adapted to low-moisture, low-salt dried abalone bodies, synergistic sequential fermentation of three bacteria, and segmented gradient drying coupling. It is impossible to simultaneously achieve a significantly shortened fermentation cycle, uniform and stable soft center, low salt content, pure flavor, low mold loss, and standardized mass production throughout the year. Summary of the Invention

[0008] The purpose of this invention is to provide a method for preparing low-salt soft-boiled dried abalone and a method for fermentation with three types of bacteria, so as to solve the problems mentioned in the background art.

[0009] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a method for preparing low-salt soft-shelled dried abalone, comprising the following steps: (1) Fresh abalone are temporarily kept to expel sand, and the shells and internal organs are removed to obtain abalone blanks; (2) Tumble the abalone blanks at low temperature to activate the abalone's endogenous enzymes, and then wash them; (3) The tumbled abalone blanks are marinated at low temperature in a sodium chloride solution with a mass concentration of 2.5% to 3.5%, and then rinsed with gradient water to desalinate, so as to obtain abalone blanks with a surface salt content of 1.5% to 2.5%. (4) The desalted abalone blanks are blanched in a water bath in sections, first kept at 75℃, then at 85℃, and finally at 95℃, and then cooled. (5) The blanched abalone blanks are subjected to a three-stage gradient drying process, which includes high-temperature shaping drying, medium-temperature water-locking balance drying and low-temperature pre-cooking conversion drying, to obtain abalone blanks with a water activity of 0.82 to 0.88. (6) A compound bacterial solution is sprayed onto the surface of the dried abalone blank by atomization. The compound bacterial solution contains Pediococcus pentosacchari, Lactobacillus plantarum and Kluyveromyces marx. The inoculated dried abalone blank is then placed in a sealed environment for constant temperature and humidity post-fermentation. (7) The fermented abalone blanks are subjected to low-temperature ultraviolet antibacterial treatment, and then non-destructive grading and vacuum nitrogen-filled packaging are used to obtain low-salt soft-core dried abalone.

[0010] Preferably, in step (2), the low-temperature tumbling temperature is 16-20°C, the rotation speed is 10-15 r / min, the time is 40-60 min, and it is carried out in the presence of edible coarse salt.

[0011] Preferably, in step (3), the temperature of low-temperature pickling is 15-20°C and the time is 1-2 hours; the gradient water rinsing is a three-stage water rinsing.

[0012] Preferably, in step (4), the specific conditions for the segmented water bath scalding are: 75℃ for 5 minutes, 85℃ for 8 minutes, 95℃ for 12 minutes, followed by rapid cooling in ice water at 0-4℃.

[0013] Preferably, in step (5), the specific conditions for the three-stage gradient drying are as follows: the temperature of the high-temperature shaping zone is 50-55℃, the relative humidity is 55%-65%, the wind speed is 0.6m / s, and the negative pressure hot air penetration drying is carried out for 2-3 hours; the temperature of the medium-temperature water-locking balance zone is 40-45℃, the relative humidity is 45%-55%, and the drying is carried out for 3-4 hours; the temperature of the low-temperature pre-curing conversion zone is 28-35℃, the relative humidity is 35%-45%, and the drying is carried out for 2-3 hours.

[0014] Preferably, in step (6), the ratio of viable bacteria of Pediococcus pentosaceus, Lactobacillus plantarum, and Kluyveromyces martensii in the compound bacterial solution is 7:2:1, and the viable bacterial concentration of each strain is ≥1×10⁻⁶. 9 The total amount of bacterial solution added was 0.10% to 0.15% of the weight of the dried abalone, at a concentration of CFU / mL.

[0015] Preferably, in step (6), the temperature of the constant temperature and humidity post-fermentation is 37°C, the relative humidity is 65% to 75%, the fermentation cycle is 12 to 18 days, and the fermentation is turned over every 3 days.

[0016] Preferably, in step (7), the temperature of the low-temperature ultraviolet sterilization is ≤30℃; the non-destructive grading adopts machine vision combined with near-infrared detection to automatically grade and screen the soft core area, color and single weight; after vacuum nitrogen filling packaging, it is stored in a constant temperature and light-proof environment of 16~20℃.

[0017] This invention also provides a three-strain fermentation method for preparing low-salt soft-boiled abalone, characterized in that the three-strain fermentation method corresponds to step (6) in claim 1 and includes the following steps: S1: A compound fermentation liquid is provided, wherein the compound fermentation liquid contains Pediococcus pentosacchari, Lactobacillus plantarum and Kluyveromyces martensii, and the ratio of live bacteria of the three is 7:2:1; S2: The compound fermentation liquid is evenly inoculated onto the surface of the abalone dried carcass obtained by steps (1) to (5) in claim 1 by atomization spraying, so that the liquid is only thinly covered on the surface, and the total amount of liquid added is 0.10% to 0.15% of the mass of the abalone dried carcass; S3: Place the inoculated dried abalone in a sealed environment with a temperature of 37℃ and a relative humidity of 65% to 75% for constant temperature and humidity post-fermentation for 12 to 18 days. Turn the abalone over every 3 days during fermentation to promote even contact of the bacteria and slow penetration into the interior to form a soft center.

[0018] Preferably, in step S1, the *Pediococcus pentosaceus*, *Lactobacillus plantarum*, and *Kluyveromyces martensii* are activated separately by liquid, and the viable cell concentration of each strain is ≥1×10⁻⁶. 9 The concentration of CFU / mL was then mixed according to the stated ratio to prepare the composite fermentation broth.

[0019] As can be seen from the above description of the structure of the present invention, compared with the prior art, the present invention has the following advantages: 1. This invention adopts a three-stage gradient drying coupled with three-strain closed directional fermentation process. The entire post-ripening process only takes 12 to 18 days, while the traditional sun-dried natural post-ripening process has a complete production cycle of more than 2 years. The efficiency of the fermentation stage is improved by about 48 times. At the same time, the production process is not constrained by natural environments such as rain and seasons, and can realize continuous production line operation throughout the year, increasing the overall production capacity by more than 3 times.

[0020] 2. This invention utilizes the time-dependent synergistic layering degradation of clam protein by endogenous proteases and exogenous extracellular enzymes from three bacteria to form a complete and transparent amber core structure in each finished product, eliminating defects such as solid hard cores and localized soft cores. The yield of high-quality soft core products has increased from approximately 65% ​​in traditional processes to over 95%, significantly enhancing the added value of the product.

[0021] 3. This invention utilizes the synergistic effect of differentiated metabolic pathways of Pediococcus pentosaceus, Lactobacillus plantarum, and Kluyveromyces martensii to selectively enrich the original sweetness and amber caramel aroma of abalone, effectively eliminating unpleasant flavors such as sourness and earthiness produced by traditional natural and disordered fermentation. After soaking and rehydration, the finished product has a plump, soft, and sticky texture, and its overall sensory quality is superior to that of traditional sun-dried abalone products on the market.

[0022] 4. The ternary compound lactic acid bacteria system of this invention continuously metabolizes lactic acid and penicillin to construct a natural antibacterial microenvironment, which effectively inhibits the proliferation of harmful microorganisms such as Aspergillus, Penicillium, and histamine-producing putrefactive bacteria. The spoilage rate of mold and sourness during the fermentation stage is reduced from about 22% in the traditional process to less than 3%. The biogenic amine content of the finished product is reduced by more than 40% compared with the existing dual-strain fermentation process, and no chemically synthesized preservatives need to be added throughout the process, achieving a low-sodium natural fermentation clean label.

[0023] 5. The lactic acid, antibacterial peptides and other metabolites generated during the fermentation process of this invention can continuously inhibit the oxidation of oils and the secondary reproduction of miscellaneous bacteria during the storage stage; after 18 months of vacuum nitrogen-filled packaging and storage at room temperature in the dark, the abalone skin is not easy to turn black and lose its luster, the soft gelatinous core is not easy to harden, the characteristic fresh and fragrant flavor decay rate is significantly lower than that of traditional sun-dried abalone, and the shelf life quality maintenance ability is outstanding. Detailed Implementation

[0024] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0025] The present invention will now be described in detail with reference to embodiments.

[0026] A method for preparing low-salt, soft-boiled dried abalone includes the following steps: (1) Fresh abalone are temporarily kept to expel sand, and the shells and internal organs are removed to obtain abalone blanks; (2) The abalone blanks are tumbled at low temperature to activate the endogenous enzymes of the abalone, and then washed; the temperature of low temperature tumbling is 16-20℃, the speed is 10-15r / min, the time is 40-60min, and it is carried out in the presence of edible coarse salt; (3) The tumbled abalone blanks are marinated at low temperature in a sodium chloride solution with a mass concentration of 2.5% to 3.5%, and then desalted by rinsing with gradient water to obtain abalone blanks with a surface salt content of 1.5% to 2.5%; the low temperature marinating temperature is 15 to 20°C and the time is 1 to 2 hours; the gradient water rinsing is a three-stage water rinsing. (4) The desalted abalone body is blanched in a segmented water bath. First, it is kept at 75℃, then at 85℃, and finally at 95℃, and then cooled. The specific conditions for the segmented water bath blanching are: 75℃ for 5 minutes, 85℃ for 8 minutes, and 95℃ for 12 minutes, followed by rapid cooling in ice water at 0-4℃. (5) The blanched abalone blanks are subjected to a three-stage gradient drying process, which includes high-temperature shaping drying, medium-temperature water-locking balance drying and low-temperature pre-cooking conversion drying, to obtain abalone blanks with a water activity of 0.82 to 0.88. The specific conditions for the three-stage gradient drying are as follows: the temperature of the high-temperature shaping zone is 50 to 55°C, the relative humidity is 55% to 65%, the wind speed is 0.6 m / s, and the negative pressure hot air penetration drying is carried out for 2 to 3 hours; the temperature of the medium-temperature water-locking balance zone is 40 to 45°C, the relative humidity is 45% to 55%, and the drying is carried out for 3 to 4 hours; the temperature of the low-temperature pre-cooking conversion zone is 28 to 35°C, the relative humidity is 35% to 45%, and the drying is carried out for 2 to 3 hours. (6) A compound bacterial solution containing *Pediococcus pentosaceus*, *Lactobacillus plantarum*, and *Kluyveromyces martensii* is sprayed onto the surface of the dried abalone. The inoculated dried abalone is then placed in a sealed environment for constant temperature and humidity fermentation. The ratio of live bacteria of *Pediococcus pentosaceus*, *Lactobacillus plantarum*, and *Kluyveromyces martensii* in the compound bacterial solution is 7:2:1, and the concentration of live bacteria of each strain is ≥1×10⁻⁶. 9 The total amount of bacterial solution added was 0.10% to 0.15% of the weight of the dried abalone. The temperature for constant temperature and humidity fermentation was 37℃, the relative humidity was 65% to 75%, the fermentation period was 12 to 18 days, and the abalone was turned over every 3 days. (7) The fermented abalone dried blanks are subjected to low-temperature ultraviolet antibacterial treatment, and then subjected to non-destructive grading and vacuum nitrogen-filled packaging to obtain low-salt soft-core dried abalone; the low-temperature ultraviolet antibacterial temperature is ≤30℃; the non-destructive grading adopts machine vision combined with near-infrared detection to automatically grade and screen the soft-core area, color and single weight; after vacuum nitrogen-filled packaging, it is stored in a constant temperature and light-proof environment of 16~20℃.

[0027] This invention provides a three-strain fermentation method for preparing low-salt soft-boiled abalone, characterized by comprising the following steps: S1: A compound fermentation liquid is provided, wherein the compound fermentation liquid contains Pediococcus pentosacchari, Lactobacillus plantarum and Kluyveromyces martensii, and the ratio of live bacteria of the three is 7:2:1; S2: The compound fermentation liquid is evenly inoculated onto the surface of the dried abalone blanks by atomization spraying, so that the liquid only thinly covers the surface layer. The total amount of liquid added is 0.10% to 0.15% of the mass of the dried abalone blanks. S3: The inoculated dried abalone blanks are placed in a sealed environment at 37℃ and 65%–75% relative humidity for constant temperature and humidity post-fermentation for 12–18 days. During fermentation, the abalone are turned over every 3 days to promote even contact of the bacteria and slow penetration into the interior, forming a soft center. The Pediococcus pentosaceus, Lactobacillus plantarum, and Kluyveromyces martensii are activated separately in liquid, and the viable cell concentration of each strain is ≥1×10⁻⁶. 9 The concentration of CFU / mL was then mixed according to the stated ratio to prepare the composite fermentation broth.

[0028] Example 1 This application is made using the following steps: Step (1): Select 2-3 fresh abalone of good size, without damage and with full vitality, and temporarily keep them in clean seawater at 20℃ for 18 hours to allow them to fully expel the mud and sand in their bodies; use a flexible mechanical shelling method to completely remove the internal organs and obtain the abalone blank, avoiding scratching the adductor meat during the operation.

[0029] Step (2): Place the abalone blank in a tumbler, add an appropriate amount of coarse salt, and tumble at low speed for 50 minutes at 18℃ and 12r / min to remove melanin and mucus from the body surface and activate the abalone's endogenous tissue protease; after tumbling, rinse thoroughly with running water and drain the surface water.

[0030] Step (3): Immerse the tumbled abalone blanks in a 3.0% sodium chloride solution and statically marinate them at 18°C ​​for 1.5 hours. After marinating, rinse them in three separate pools of clear water in a gradient manner to control the salt content on the surface of the abalone blanks to 2.0%.

[0031] Step (4): Place the desalted abalone blanks in a jacketed kettle and blanch them in a water bath in sections without boiling. The specific conditions are: keep warm at 75℃ for 5 minutes → keep warm at 85℃ for 8 minutes → keep warm at 95℃ for 12 minutes; after blanching, immediately transfer them to ice water at 0-4℃ for rapid cooling.

[0032] Step (5): The blanched and cooled abalone blanks are dried using a three-stage negative pressure gradient drying process. High-temperature setting zone: temperature 52℃, relative humidity 60%, wind speed 0.6m / s, negative pressure hot air penetration drying for 2.5h; Medium-temperature water-locking balance zone: temperature 42℃, relative humidity 50%, drying time 3.5h; Low-temperature pre-cooking conversion zone: temperature 30℃, relative humidity 40%, drying for 2.5h; the drying process is combined with hot air waste heat recovery and recycling to obtain abalone blanks with a water activity of 0.85.

[0033] Step (6): Prepare the compound fermentation broth by separately activating Pediococcus pentosaceus, Lactobacillus plantarum, and Kluyveromyces martensii into liquid culture until the viable cell concentration is ≥1×10⁻⁶. 9 CFU / mL, mixed with live bacteria in a ratio of 7:2:1 to prepare a compound bacterial solution; the compound bacterial solution was evenly sprayed onto the surface of the abalone dried blank obtained in step (5) through a low-pressure atomizing nozzle, and the total amount of bacterial solution added was 0.1% of the mass of the abalone dried blank; the inoculated abalone dried blank was placed in a clean, light-proof, and sealed fermentation chamber at a temperature of 37℃ and an ambient relative humidity of 70%, with low air volume and slight ventilation, and was subjected to constant temperature and humidity post-fermentation for 15 days, turning it over once every 3 days.

[0034] Step (7): After fermentation, the abalone is subjected to low-temperature ultraviolet instantaneous antibacterial treatment at ≤30℃; machine vision combined with near-infrared online non-destructive testing is used to automatically grade and screen the abalone based on the surface area, amber color and weight of each abalone; qualified products are sealed in vacuum nitrogen-filled composite bags and stored at 18℃ under constant temperature and light-proof conditions to obtain the low-salt dried abalone product.

[0035] Test results: Total fermentation cycle 15 days; 96% of the product was of superior quality with soft center; mold loss 2.1%; histamine content <30mg / kg; sensory score 92 points.

[0036] Comparative Example 1 (Traditional Sun-Dried Natural Post-Ripe Fermentation Process) Fresh abalone of the same specifications and batch as in Example 1 were used. After shelling and eviscerating, the abalone was sun-dried in the open air for 45 days using traditional methods, and then naturally fermented in a natural environment for 24 months.

[0037] Test results: 63% of the products were of excellent quality; 23.5% were lost due to mold; histamine content was 112 mg / kg; the product had a strong earthy smell and a sensory score of 68.

[0038] Comparative Example 2 (Existing dual-strain fermentation process: Lactobacillus plantarum and Saccharomyces cerevisiae, with added bacteria during the pickling stage) Fresh abalone of the same specifications and batch as in Example 1 were used, and step (1) was the same as in Example 1. The difference was that in step (3), a mixed bacterial solution of Lactobacillus plantarum and Saccharomyces cerevisiae was added to a 3.0% sodium chloride solution during the marinating stage; conventional constant temperature drying was used (without three-stage gradient partitioning); and only the above-mentioned two bacteria were used in the fermentation stage, with fermentation at 37°C for 15 days. The remaining steps were basically the same as in Example 1.

[0039] Test results: 71% of the products were of excellent quality; 10.2% were lost due to mold; histamine content was 76 mg / kg; there was a slight sour smell; sensory score was 76 points.

[0040] Comparative Example 3 (fermentation with Pediococcus pentosacchari, 30% high-salt curing) Fresh abalone of the same specifications and batch as in Example 1 were used, and step (1) was the same as in Example 1. The difference was that step (3) used a 30% sodium chloride solution for marinating; and step (6) was inoculated only with Pediococcus pentosaceus (live bacteria concentration ≥1×10⁻⁶). 9 The inoculum was 0.1% (CFU / mL), and fermentation was carried out at 37°C for 15 days. The remaining steps were basically the same as in Example 1.

[0041] Test results: High salinity of the body inhibits protease, poor permeability of the soft center, and the rate of excellent products is 74%; mold loss is 7.8%; histamine content is 63mg / kg; the meat is relatively tough, the amber aroma is weak, and the sensory score is 79 points.

[0042] The comparison and summary table (1) is as follows: The data above demonstrate that the preparation method provided by this invention, while shortening the production cycle to 15 days, simultaneously achieves a high yield of 96% of high-quality soft-boiled products, a low mold loss of only 2.1%, a low histamine content of 28 mg / kg, and a high sensory score of 92 points. This simultaneous and significant optimization of four key indicators is unattainable by any of the comparative examples. In particular, Comparative Example 2, using double-strain pickling and inoculation, failed to effectively control mold and histamine, while Comparative Example 3, by reducing the fermentation cycle, sacrificed the quality and flavor of the soft-boiled product. This invention, by coupling specific three-strain compounding, low-salt pickling, post-drying inoculation, and three-stage negative pressure gradient drying, breaks through the technical bottleneck of simultaneously achieving a high yield of high-quality soft-boiled products, high safety, and excellent flavor within a short period. Such comprehensive technical effects are beyond the reasonable expectations of those skilled in the art.

[0043] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing low-salt, soft-boiled dried abalone, characterized in that, Includes the following steps: (1) Fresh abalone are temporarily kept to expel sand, and the shells and internal organs are removed to obtain abalone blanks; (2) Tumble the abalone blanks at low temperature to activate the abalone's endogenous enzymes, and then wash them; (3) The tumbled abalone blanks are marinated at low temperature in a sodium chloride solution with a mass concentration of 2.5% to 3.5%, and then rinsed with gradient water to desalinate, so as to obtain abalone blanks with a surface salt content of 1.5% to 2.5%. (4) The desalted abalone blanks are blanched in a water bath in sections, first kept at 75℃, then at 85℃, and finally at 95℃, and then cooled. (5) The blanched abalone blanks are subjected to a three-stage gradient drying process, which includes high-temperature shaping drying, medium-temperature water-locking balance drying and low-temperature pre-cooking conversion drying, to obtain abalone blanks with a water activity of 0.82 to 0.

88. (6) A compound bacterial solution is sprayed onto the surface of the dried abalone blank by atomization. The compound bacterial solution contains Pediococcus pentosacchari, Lactobacillus plantarum and Kluyveromyces marx. The inoculated dried abalone blank is then placed in a sealed environment for constant temperature and humidity post-fermentation. (7) The fermented abalone blanks are subjected to low-temperature ultraviolet antibacterial treatment, and then non-destructive grading and vacuum nitrogen-filled packaging are used to obtain low-salt soft-core dried abalone.

2. The method for preparing low-salt, soft-boiled dried abalone according to claim 1, characterized in that: In step (2), the low-temperature tumbling temperature is 16-20°C, the rotation speed is 10-15 r / min, the time is 40-60 min, and it is carried out in the presence of edible coarse salt.

3. The method for preparing low-salt, soft-boiled dried abalone according to claim 1, characterized in that: In step (3), the temperature for low-temperature pickling is 15-20°C and the time is 1-2 hours; the gradient water rinsing is a three-stage water rinsing.

4. The method for preparing low-salt, soft-boiled dried abalone according to claim 1, characterized in that: In step (4), the specific conditions for the segmented water bath scalding are: 75℃ for 5 minutes, 85℃ for 8 minutes, 95℃ for 12 minutes, followed by rapid cooling in ice water at 0-4℃.

5. The method for preparing low-salt, soft-boiled dried abalone according to claim 1, characterized in that: In step (5), the specific conditions for the three-stage gradient drying are as follows: the temperature of the high-temperature shaping zone is 50-55℃, the relative humidity is 55%-65%, the wind speed is 0.6m / s, and the negative pressure hot air penetration drying is carried out for 2-3 hours; the temperature of the medium-temperature water-locking balance zone is 40-45℃, the relative humidity is 45%-55%, and the drying is carried out for 3-4 hours; the temperature of the low-temperature pre-curing conversion zone is 28-35℃, the relative humidity is 35%-45%, and the drying is carried out for 2-3 hours.

6. The method for preparing low-salt, soft-boiled dried abalone according to claim 1, characterized in that: In step (6), the ratio of viable bacteria of Pediococcus pentosaceus, Lactobacillus plantarum, and Kluyveromyces martensii in the compound bacterial solution is 7:2:1, and the viable bacterial concentration of each strain is ≥1×10⁻⁶. 9 The total amount of bacterial solution added was 0.10% to 0.15% of the weight of the dried abalone, at a concentration of CFU / mL.

7. The method for preparing low-salt, soft-boiled dried abalone according to claim 1, characterized in that: In step (6), the temperature of the constant temperature and humidity post-fermentation is 37°C, the relative humidity is 65% to 75%, the fermentation cycle is 12 to 18 days, and the fermentation is turned over every 3 days.

8. The method for preparing low-salt, soft-boiled dried abalone according to claim 1, characterized in that: In step (7), the temperature of the low-temperature ultraviolet sterilization is ≤30℃; the non-destructive grading adopts machine vision combined with near-infrared detection to automatically grade and screen the soft core area, color and single weight; after vacuum nitrogen filling packaging, it is stored in a constant temperature and light-proof environment of 16~20℃.

9. A three-strain fermentation method for preparing low-salt soft-boiled abalone according to claim 1, characterized in that, The three-strain fermentation method corresponds to step (6) in claim 1 and includes the following steps: S1: A compound fermentation liquid is provided, wherein the compound fermentation liquid contains Pediococcus pentosacchari, Lactobacillus plantarum and Kluyveromyces martensii, and the ratio of live bacteria of the three is 7:2:1; S2: The compound fermentation liquid is evenly inoculated onto the surface of the abalone dried carcass obtained by steps (1) to (5) in claim 1 by atomization spraying, so that the liquid is only thinly covered on the surface, and the total amount of liquid added is 0.10% to 0.15% of the mass of the abalone dried carcass; S3: Place the inoculated dried abalone in a sealed environment with a temperature of 37℃ and a relative humidity of 65% to 75% for constant temperature and humidity post-fermentation for 12 to 18 days. Turn the abalone over every 3 days during fermentation to promote even contact of the bacteria and slow penetration into the interior to form a soft center.

10. The method for fermentation of three strains according to claim 9, characterized in that: In step S1, *Pediococcus pentosaceus*, *Lactobacillus plantarum*, and *Kluyveromyces martensii* are activated separately by liquid, and the viable cell concentration of each strain is ≥1×10⁻⁶. 9 The concentration of CFU / mL was then mixed according to the stated ratio to prepare the composite fermentation broth.

Images