Preparation method of dried soft-centered abalone

Abstract

This invention discloses a method for preparing dried abalone with a soft center, belonging to the field of aquatic product processing and dried product processing technology. This method utilizes β-cyclodextrin and citric acid to synergistically remove fishy odors and reduce the adverse effects of off-flavor components. Through sequential enzymatic regulation of the central region after tenderization followed by cross-linking, a textural gradient is constructed, resulting in a sticky, glutinous center and a supportive outer layer. Day and night cyclic temperature and humidity controlled drying establishes a reasonable moisture gradient between the inner and outer layers, reducing the risk of surface crusting, curling, and cracking. Intermittent UVC surface sterilization treatment reduces the microbial load on the sample surface, improving processing safety and storage stability. This invention combines low-temperature deodorization, sequential enzymatic regulation of the central region, day and night cyclic drying, and intermittent sterilization treatment, achieving a synergistic improvement in flavor purification, the construction of a soft-centered texture, and processing stabilization. This method is technologically sound and highly operable, providing technical support for the quality improvement and standardized processing of dried abalone with a soft center, and has promising application prospects.

Description

Technical Field

[0001] This invention belongs to the field of aquatic product processing and dried product processing technology, specifically relating to a processing method for dried abalone with soft center. Background Technology

[0002] Abalone is one of my country's important high-value marine shellfish, characterized by its high protein content, unique flavor, and high nutritional value. Besides being eaten fresh, abalone can be processed into frozen, cooked, and dried products. Dried products are particularly important due to their ease of storage and transport, and their long shelf life. Dried abalone typically has a rich, lasting aroma and a sweet aftertaste, thus possessing high commercial value and market acceptance. Soft-centered dried abalone, a specialty product among dried abalone, is considered a high-end dried seafood delicacy due to its superior quality, unique flavor, and texture. Its typical characteristics include a gelatinous central area that becomes noticeably sticky and glutinous after rehydration and cooking, while the outer layer retains a certain degree of toughness and shape retention.

[0003] Traditional processing methods for soft-boiled dried abalone typically rely on manual experience, often involving washing, pre-cooking, sun-drying, or hot-air drying. These methods are time-consuming and highly susceptible to seasonal, climatic, and environmental conditions. Patent CN113519793A discloses a method for processing soft-boiled dried abalone, which uses a compound enzyme solution soaking combined with a drying process to prepare the product, improving its soft texture. However, its enzyme treatment primarily uses a whole-body soaking method, making it difficult to precisely control the central area of ​​the abalone. This can lead to uneven processing between the central and outer layers, poor stability of the soft-boiled texture, and problems such as curling and cracking during the drying process. Patent CN106262034A discloses a heat pump drying process for abalone, which mainly improves the rehydration properties and quality consistency of abalone products by controlling drying temperature and humidity. However, this method mainly focuses on optimizing drying parameters, and the control of odor-related substances is still mainly based on salting or seasoning to cover them up, lacking source purification methods; at the same time, it involves less control over surface sterilization, mold prevention and hygiene and safety stabilization during processing and storage, and the storage stability of the product still needs to be improved.

[0004] Based on the current state of the dried abalone industry, several problems still exist in standardized and continuous production: First, abalone easily produces or accumulates fishy-smelling substances during pre-treatment and drying. Conventional salting or spice treatment mainly masks these odors, failing to reduce the adverse effects of these substances at the source. Second, the key to the quality of dried abalone lies in the formation of a texture gradient between a supportive outer layer and a sticky, glutinous center. Current treatments mainly employ methods such as whole-body soaking, whole-body enzymatic hydrolysis, or conventional drying. These methods lack sufficient control over the central region, easily leading to unstable softness in the center or excessive softening of the outer layer. Third, simple hot air drying or shortening the drying time can easily increase the surface microbial load and decrease storage stability. Therefore, it is particularly necessary to develop a method for preparing dried abalone with low fishy odor, prominent abalone flavor, a sticky, glutinous center, stable quality, high safety, and long shelf life. Summary of the Invention

[0005] To address the aforementioned problems, this invention aims to provide a method for preparing dried abalone with a soft, sticky texture in the center, while maintaining the outer layer's support, resulting in a dried abalone product that combines a soft, sticky texture in the center with excellent flavor purity, good rehydration quality, and strong processing stability.

[0006] To achieve the above objectives, the present invention provides a method for preparing dried abalone with a soft center, comprising the following steps: Step 1: Remove the shell and viscera from fresh abalone or thawed abalone that meets food processing requirements, and wash and drain them.

[0007] Step 2: Salt washing to remove the black membrane. Add salt to the surface of the abalone meat and rub it to remove the surface mucus and black membrane. Then, salt it. After salting, rinse it and drain it briefly to remove the salt.

[0008] Step 3: Low-temperature deodorization treatment. The salted and desalted abalone meat is soaked in a deodorizing solution at low temperature to reduce the adverse effects of hydrophobic odor components and volatile nitrogenous odor substances on the flavor of the finished product.

[0009] Step 4: Targeted injection in multiple stages. First, inject protease solution at multiple points in the central area of ​​the abalone foot and let it stand to form a tenderizing window. Then, inject cross-linking enzyme solution at the same or similar points and let it stand to form a cross-linking window, promoting the reconstruction of the protein network in the central area and forming a structure with a sticky center and a supportive outer layer.

[0010] Step 5: Pre-cooking for enzyme inactivation and fixation. The abalone that has undergone injection regulation is pre-cooked to inactivate enzymes and fix the tissue structure. The cross-linked abalone meat is placed in a water bath at 75℃~85℃ for 15~20 minutes, ensuring that the core temperature reaches 75℃~80℃ and is maintained for 2~5 minutes to simultaneously inactivate enzymes and fix the structure. After pre-cooking, it is immediately cooled with ice water and drained.

[0011] Step Six: Day and Night Cyclic Temperature and Humidity Control Drying. The pre-cooked abalone is placed in a temperature and humidity controlled drying device for cyclic drying. During the daytime stage, dehydration drying is carried out, and at night, moisture reabsorption and equalization are carried out to create a reasonable moisture gradient between the inner and outer layers of the product.

[0012] Step 7: During the day-and-night temperature and humidity controlled drying process, intermittent UVC irradiation is also performed to reduce microorganisms on the sample surface. After drying, the sample is cooled and packaged using vacuum packaging or modified atmosphere packaging to obtain the dried abalone product.

[0013] In one embodiment of the present invention, in step one, the abalone is a wrinkled abalone or a similar edible abalone, and the net weight of a single abalone after shelling and viscera removal is 30-100g.

[0014] In one embodiment of the present invention, in step two, the amount of salt added during the salt washing of the black membrane is 8% to 15% of the abalone meat mass, and the kneading time is 3 to 15 minutes. Salt curing is performed using a sodium chloride solution or dry salt; when brine curing is used, the brine mass-volume fraction is 6% to 15%, the temperature is 0 to 8°C, and the time is 4 to 16 hours; preferably, the brine mass-volume fraction is 8% to 12%, the temperature is 2 to 6°C, and the time is 6 to 10 hours. Desalting time is 5 to 10 minutes, and the desalting temperature is 0 to 8°C.

[0015] In one embodiment of the present invention, in step three, the deodorizing soaking solution is composed of β-cyclodextrin, citric acid and water, with a content of 0.30%~0.80% (w / v, g / 100 mL) of β-cyclodextrin and 0.10%~0.30% (w / v, g / 100 mL) of citric acid; the conditions for soaking abalone meat in the deodorizing soaking solution are: solid-liquid ratio 1:3~1:5 (m / v, g:mL), temperature 0℃~5℃, and soaking time 1~3h.

[0016] In one embodiment of the present invention, in step four, the protease solution is a food industry protease solution, preferably kiwi protease (Actinidin) or its equivalent protease, and the mass-volume fraction of kiwi protease powder (800 U / g) in the protease solution is 4.0%–12.0% (w / v, g / 100 mL). Multiple injection points are used, ranging from 5 to 15 points, with an injection depth of 40%–80% of the foot thickness. The total injection volume of protease solution for each abalone is 0.8–2.5 mL. The tenderizing window temperature is 8–15°C, and the time is 10–60 min.

[0017] The cross-linking enzyme solution was a microbial transglutaminase (mTG) solution, with a mass-volume fraction of 4.0%–12.0% (w / v, g / 100 mL) of microbial transglutaminase powder (100 U / g) in the solution. The total injection volume of the cross-linking enzyme solution for each abalone was 0.3–1.5 mL. The cross-linking window temperature was 18–30℃, and the time was 40–240 min. A sequence of "protease pretreatment followed by mTG cross-linking" was used to regulate the process, resulting in a synergistic effect of "moderate initial deconstruction followed by stable cross-linking" in the central region of the abalone. This improved the consistency of the soft-boiled texture in the center and reduced the risk of excessive softening of the outer layer.

[0018] In one embodiment of the present invention, step six consists of a 24-hour cycle, including 8-14 hours of daytime and 10-16 hours of nighttime; the daytime temperature is 18-30°C and the relative humidity is 50%-75%, and the nighttime temperature is 8-15°C and the relative humidity is 75%-95%, with the product being turned over 1-3 times during the day-night cycle and mid-day. Preferably, at the drying endpoint, the finished product has a moisture content of 15%-20%, an outer layer water activity (aw) of 0.60-0.70, and a core water activity (aw) of 0.68-0.78.

[0019] In one embodiment of the present invention, in step seven, the center wavelength of UVC is 254 nm, and the irradiation intensity is 0.5~0.8 mW / cm². 2 The lamp spacing is 15-30 cm; irradiate 1-2 times during the day, each time for 2-5 minutes. After each irradiation, flip the lamp or adjust its placement to reduce shaded areas; do not irradiate at night. Preferably, the UVC intermittent surface sterilization treatment is performed 1-3 days before drying.

[0020] This invention provides dried soft-boiled abalone prepared by the method described above.

[0021] Beneficial effects: (1) This invention innovates the low-temperature deodorization formula and process of β-cyclodextrin combined with citric acid, which can not only weaken the adverse effects of fishy-related hydrophobic small molecules and volatile amines on flavor, but also reduce the adverse effects of acidic environment on the abalone tissue structure and soft texture formation, thereby achieving both deodorization and soft texture preservation.

[0022] (2) This invention overcomes the structural collapse problem caused by traditional global soaking by centrally and sequentially injecting protease and microbial transglutaminase. It allows for differentiated control of the abalone's central area, which is beneficial for forming a stable, sticky texture in the center and better maintaining the shape and support of the outer layer. The heat pump day and night circulating drying process used in this invention simulates the traditional daytime sun drying and nighttime rehydration moisture migration mechanism, establishing a reasonable water activity gradient between the outer layer and the center. This significantly reduces the risk of surface crusting, curling, and cracking caused by continuous drying in strong winds, ensuring the product's appearance integrity and rehydration uniformity.

[0023] (3) The present invention creatively adopts intermittent UVC irradiation, which has a good surface sterilization effect, significantly reduces the risk of microorganisms and mold on the surface of abalone, and helps to improve processing safety and storage stability. At the same time, the combination of β-cyclodextrin and citric acid low-temperature deodorization and day and night circulating temperature and humidity control drying reduces the adverse effects of oxidation in subsequent processing, so that the final product is safe while the odor of oil oxidation is greatly reduced, significantly improving the overall quality of product processing and storage. Attached Figure Description

[0024] Figure 1 Sensory evaluation of dried soft-boiled abalone from different treatment groups.

[0025] Figure 2 Total bacterial count of dried soft-boiled abalone in different treatment groups.

[0026] Figure 3 Peroxide value (POV) of dried soft-boiled abalone from different treatment groups.

[0027] Figure 4 Thiobarbituric acid reactants (TBARS) for dried soft-boiled abalone in different treatment groups.

[0028] Figure 5 Moisture content of dried abalone with soft center in different treatment groups.

[0029] Figure 6 The rehydration rate of dried soft-boiled abalone in different treatment groups.

[0030] Figure 7 Electronic nose flavor profiles for dried soft-boiled abalone in different treatment groups.

[0031] Figure 8 Volatile flavor compounds of dried soft-boiled abalone in different treatment groups.

[0032] Figure 9 This is a flowchart of the technical solution of the present invention. Detailed Implementation

[0033] The present invention will be further explained below with reference to the accompanying drawings and specific embodiments. The following embodiments and comparative examples all use Dalian abalone (wrinkled abalone) as raw material. The net weight of each abalone after shelling and visceration was controlled to be 60-70g / abalone. Further screening was performed on samples used for central injection, with a weight of 65±2g / abalone to ensure consistency between injection volume and injection site. Each batch consisted of 1300g of shelled and viscerated abalone meat. The protease solution used in this embodiment was prepared from commercially available food-grade protease preparations. The protease was food-grade kiwi protease provided by Tianhe Food Biotechnology Co., Ltd.; the cross-linking enzyme solution was prepared from food-grade microbial transglutaminase preparations provided by Xiasheng Enzyme Biotechnology Co., Ltd.

[0034] The testing methods used in this invention: All samples underwent the same raw material grading and basic pretreatment process, and were randomly assigned to different treatment groups under the same batch conditions to reduce the impact of individual raw material differences on the results. The dried product was used for the determination of total bacterial count and moisture content. In addition to these two items, all other physicochemical, oxidation, flavor-related indicators, and sensory evaluations were performed after a unified rehydration and cooking procedure. The rehydration process used purified water at a temperature of 4℃, maintaining a consistent solid-liquid ratio. The total rehydration time was 72 hours, with purified water replaced every 24 hours to minimize the interference of water quality changes on the results. After rehydration, the samples were placed in a gently boiling water bath (95~98℃) and heated for 12 hours, maintaining a constant water level and replenishing water to maintain a constant solid-liquid ratio. After cooking, the samples were removed, drained of surface moisture, and allowed to stand at 25℃ for 30 minutes for equilibration before subsequent testing. For the determination of textural properties (TPA), samples were taken from the outer layer and the center: the outer layer was the tissue approximately 2-3 mm inward from the surface, and the center was the tissue in the central region along the thickness direction of the foot, used to evaluate the gradient structure of the soft center and its differences in texture after ripening. All experiments were performed in triplicate (n=3).

[0035] Total bacterial count determination: Take 25g of the outer layer tissue of each group of dried finished products, cut it into small pieces, add 225mL of sterile phosphate buffer or sterile physiological saline, and homogenize in a homogenizer at 8000~10000r / min for 1~2min to prepare 10 -1 The homogenized solution was then serially diluted 10-fold. Selecting an appropriate dilution, 1.0 mL of the diluted solution was pipetted into a sterile Petri dish, and 15-20 mL of plate counting agar (PCA) cooled to 46-50°C was added. The mixture was poured in, mixed thoroughly, and allowed to solidify before incubation upside down. Incubation conditions were performed according to GB 4789.2-2022, i.e., incubation at 30±1°C for 72±3 h. Plates with colony counts between 30 and 300 CFU were selected for counting, and the results were converted to CFU / g using standard methods. The results can be further converted to log CFU / g.

[0036] Moisture content determination: Take the dried finished product samples from each group, first cut them longitudinally, then take equal mass of the outer layer and the central tissue, mix them, cut them into small pieces, and mix thoroughly. Weigh 2.0~5.0g of the sample and place it in a pre-weighed weighing dish, spreading the sample into a thin layer, with a thickness controlled below 5mm. Place the weighing dish in a 105℃ oven to dry to constant weight, weighing it every 1 hour. The difference between two consecutive weighings should not exceed 0.002g to be considered constant weight. Record the sample mass before drying as m1 and the mass after constant weight as m2. Calculate the moisture content according to the formula (m1-m2) / m1×100, expressed as a percentage.

[0037] Rehydration rate determination: Weigh the initial mass m0 of each group of dried abalone samples, accurate to 0.01g, and place them in purified water at 4℃ for 72h. Replace the purified water every 24h during the rehydration process. Samples were removed at 12h, 24h, 36h, 45h, 60h, and 72h, and after gently pressing with filter paper to absorb the surface free water, they were weighed and recorded as m. t According to formula (m) t The rehydration rate is calculated as (-m0) / m0×100, and the rehydration rate at 72h is taken as the final rehydration rate.

[0038] Peroxide value (POV) determination: The rehydrated and boiled sample was chopped and mixed thoroughly. Total lipids were extracted using chloroform / methanol (2:1, v / v), and the solvent was removed by rotary evaporation to obtain the oil. Accurately weigh 0.50–1.00 g of oil into an iodine flask, add 30 mL of glacial acetic acid / chloroform mixture (3:2, v / v) to dissolve, then add 0.5 mL of freshly prepared saturated KI solution. After reacting in the dark for 1 min, add 30 mL of deionized water and titrate with 0.01 mol / L Na₂S₂O₃ standard solution until a pale yellow color is obtained. Add 1% starch indicator and continue titrating until the blue color just disappears. A blank test was performed simultaneously. POV (meq / kg) was calculated using the formula: POV = (V – V₀) × N × 1000 / m, where V is the sample titration volume, V₀ is the blank titration volume, N is the Na₂S₂O₃ concentration, and m is the oil mass.

[0039] The determination of thiobarbituric acid reactants (TBARS) was performed according to the method of Wang et al. (2002). The rehydrated and boiled sample was chopped and mixed thoroughly. 5.0 g of the sample was weighed and 15 mL of extraction buffer (7.5% (w / v) TCA + 0.1% (w / v) EDTA + 0.1% (w / v) propyl gallate) was added. After homogenization and centrifugation, the supernatant was filtered. 2.0 mL of the filtrate was mixed with 2.0 mL of 80 mM TBA solution and incubated at 40 °C for 90 min. The absorbance was measured at 532 nm. A standard curve for MDA was prepared using 1,1,3,3-tetraethoxypropane (TEP) for quantitative conversion. The results are expressed as mg MDA / kg sample.

[0040] Texture properties (TPA) determination: Samples were rehydrated for 72 hours according to a standardized procedure, then boiled in a low-boiling water bath (95~98℃) for 12 hours. After removing and drying the surface moisture, samples were equilibrated at 25℃ for 30 minutes. Samples were taken from the outer layer and the center, with the outer layer being the 2~3 mm tissue from the surface inward and the center being the central region in the foot thickness direction. Samples were cut into 10 mm × 10 mm × 10 mm cubes; when the sample size was insufficient, they were uniformly prepared into φ10 mm × 10 mm cylinders to ensure consistent sample size. The texture analyzer was used for determination in dual compression mode, with the following parameters: probe P / 36, trigger force 5g, pre-test speed 2.0 mm / s, test speed 1.0 mm / s, post-test speed 2.0 mm / s, compression ratio 50%, and an interval of 5 seconds between the two compressions. The measured indicators include hardness, gumminess, chewiness, adhesiveness, springiness, and resilience. The results of the measurements in the outer and central areas were recorded separately to characterize the differences in texture of the soft-boiled texture.

[0041] Sensory evaluation methods: Sensory evaluations were conducted on uniformly rehydrated and standardized cooked samples. After cooking, samples were removed, surface moisture was absorbed, and the samples were equilibrated at 25°C for 30 minutes before being sliced. The slice thickness was approximately 5 mm, and the middle section of the foot was uniformly selected to ensure that the sample contained both the central and outer tissues. Samples were presented blindly using a three-digit randomized code, and the sampling order was randomized. The sensory evaluation team consisted of 20 members (10 males and 10 females) selected and trained according to ISO 8586:2023, aged 25-35 years. Evaluations were conducted in separate cubicles or quiet laboratory environments with white light illumination and room temperature controlled at 22-25°C. Patients were cleansed with warm water and unsalted soda crackers between evaluations. Evaluation indicators included fishy odor intensity, rancid odor, umami flavor, hard outer shell texture, soft and sticky central texture, elasticity, and overall acceptability, using a 9-point scoring system, where 0 represents none or very poor, and 9 represents very strong or very good. Each batch of samples underwent a complete evaluation, and the final result was expressed as the mean ± standard deviation of three independent batches.

[0042] Determination of volatile flavor compounds: HS-SPME-GC-MS method was used. The central tissue of the rehydrated and boiled sample was chopped and mixed thoroughly. 3.0 g of sample was weighed into a 20 mL headspace vial, and 1.0 g NaCl and internal standard 2-methyl-3-heptanone (10 μL, 10 mg / L) were added. The vial was immediately sealed. After equilibration at 50 °C for 20 min, the sample was extracted at 50 °C for 30 min using a DVB / CAR / PDMS 50 / 30 μm extraction fiber, followed by desorption at a 250 °C injection port for 5 min. GC conditions were: DB-Wax column (30 m × 0.25 mm × 0.25 μm), carrier gas He, flow rate 1.0 mL / min; temperature program: 40 °C held for 3 min, increased to 120 °C at 5 °C / min, then increased to 230 °C at 10 °C / min and held for 5 min. MS conditions included an EI ion source, electron energy 70 eV, and a scan range of m / z 35–350. Compounds were qualitatively analyzed by NIST library matching and retention index-assisted identification, and semi-quantitative or relative quantitative analysis was performed using the internal standard peak area ratio.

[0043] Flavor profile analysis using an electronic nose: Flavor fingerprint analysis of each group of samples was performed using a PEN3 electronic nose (Airsense Analytics GmbH, Germany). 5g of sample was placed in a 20mL sealed headspace vial and incubated at 50℃ for 20min; subsequently, it was equilibrated at 25℃ for 30min before electronic nose detection. Detection parameters were: single sample testing time 70s, injection flow rate 200mL / min, and a sampling frequency of recording the response value every 1s; after each measurement, the sensor cavity was cleaned with clean air for 70s to restore the baseline. The sensor array and its representative compounds were: W1C, aromatic compounds; W1S, methyl compounds; W5S, nitrogen oxides; W1W, inorganic sulfides; W3C, ammonia and aromatic compounds; W2S, alcohols, aldehydes, and ketones; W6S, hydrogen compounds; W2W, organic sulfides and aromatic compounds; W5C, short-chain alkanes and aromatic alkenes; W3S, long-chain alkanes. The electronic nose output signal is represented by G / G0, where G is the sensor conductivity value under the action of sample gas and G0 is the baseline conductivity value of clean air. The 70s stable segment feature value is selected for pattern recognition analysis such as PCA or LDA.

[0044] Statistical analysis: All experiments were performed in triplicate, and results are expressed as mean ± standard deviation. Plotting was performed using Origin software, and one-way ANOVA was conducted using SPSS software. P <0.05 indicates a significant difference.

[0045] Example According to the method for preparing dried soft-boiled abalone disclosed in this invention, the product of the example is prepared.

[0046] 1. Raw material selection and cleaning: Select fresh Dalian abalone (wrinkled abalone), temporarily keep it in oxygenated seawater at 15℃ for 12 hours, remove the shell, take out the meat and internal organs, rinse with running cold water for 2 minutes, and drain. Add 12% (w / w) sea salt according to the weight of abalone meat and rub the surface for 3 minutes to remove the black membrane and mucus layer, rinse with cold water for 30 seconds and drain. 2. Saltwater pickling: Place the processed abalone meat in 10% (w / v) sodium chloride brine at 4℃ and soak and pickle for 8 hours at a solid-liquid ratio of 1:3 (m / v, g:mL). Turn the meat over once after 4 hours of pickling. After the pickling is finished, rinse with cold water for 10 seconds and desalinate in cold water at 4℃ for 10 minutes, then drain.

[0047] 3. Low-temperature deodorization: Place the abalone meat in a 4℃ deodorization soaking solution and soak for 2 hours at a solid-liquid ratio of 1:4 (m / v, g:mL). The deodorization soaking solution is a mixed solution of 0.50% (w / v) β-cyclodextrin and 0.20% (w / v) citric acid. Gently shake at 60 rpm. After soaking, rinse with 4℃ cold water for 10 seconds and pat dry.

[0048] 4. Centralized Enzymatic Hydrolysis and Cross-linking: Abalone with a net weight of 65±2g / animal were selected for centralized, fractionated injection. Using a 23G needle, a 9-point grid injection of protease solution was performed into the central area of ​​the foot, to a depth of 60% of the foot thickness. The protease solution contained 8.0% (w / v) of kiwifruit protease powder (800U / g), prepared with 10 mM phosphate buffer (pH 6.0). 0.18 mL was injected at each point (1.62 mL per abalone). After degassing and sealing, the sample was incubated at 12℃ for 30 min. Subsequently, the sample was cooled at 4℃ for 10 min, and cross-linking enzyme solution was injected at the same location and depth. The cross-linking enzyme solution contained 8.0% (w / v) of microbial transglutaminase powder (100U / g), prepared with 10 mM phosphate buffer (pH 6.5). 0.09 mL was injected at each point (0.81 mL per abalone). After degassing and sealing, the sample was incubated at 25℃ for 120 min.

[0049] 5. Pre-cooking and shaping: Place the cross-linked abalone meat in an 80℃ water bath for 18 minutes to ensure that the center temperature reaches 78℃ and is maintained for 3 minutes. After removing it, immediately cool it in ice water for 5 minutes and drain it.

[0050] 6. Heat pump day and night cycle drying: Place the sample flat on the tray and put it in the heat pump drying system. Dry according to the 24-hour cycle program: Day 1-2: run at 22℃ / 65%RH for 12 hours during the day and at 12℃ / 85%RH for 12 hours at night; Day 3-5: run at 22℃ / 60%RH for 12 hours during the day and at 12℃ / 80%RH for 12 hours at night; Day 6 and thereafter: run at 22℃ / 55%RH for 12 hours during the day and at 12℃ / 78%RH for 12 hours at night; turn the sample over once during the day-night cycle, and once at the 6th hour of the day, for a total of 3 times every 24 hours.

[0051] 7. UVC Irradiation: During Day 1-2, intermittent surface sterilization treatment with 254 nm UVC was introduced. Irradiation conditions were: lamp distance 20 cm from sample surface, surface irradiance 0.7 mW / cm². 2 The sample was irradiated twice a day, at the 3rd and 8th hour of the day. Each time, one side of the sample was irradiated for 2 minutes, followed by irradiation of the other side for 2 minutes. This was counted as one irradiation, and a total of 2 irradiations were performed per day. On Day 3, the sample was irradiated again at the 5th hour of the day under the same conditions. During the irradiation process, the position of the sample was adjusted as needed based on its placement to reduce the shaded area. No irradiation was performed at night. 8. Dry until the moisture content of the finished product is 17.0%, cool the sample at room temperature for 30 minutes and vacuum pack it to obtain the product of the example.

[0052] Comparative Example 1 Prepare the product of Comparative Example 1. Follow steps 1 and 2 as in the Example. In step 3, only citric acid solution was used for deodorization; the abalone meat was placed in a 0.20% (w / v) citric acid aqueous solution at 4 ℃ and soaked for 2 h at a solid-liquid ratio of 1:4 (m / v, g:mL). After soaking, it was rinsed with cold water at 4 ℃ for 10 s and then dried. The remaining steps, including the center-directed fractional injection in step 4, the pre-cooking and shaping in step 5, the day-night cyclic drying in step 6, and the intermittent UVC irradiation in step 7, were the same as in the Example.

[0053] Comparative Example 2 Prepare the product of Comparative Example 2. Complete steps 1, 2, and 3 according to the example. In step 4, instead of the sequential control method of "protease treatment first, mTG cross-linking later," the protease solution and cross-linking enzyme solution were mixed and injected simultaneously. Specifically, 8.0% (w / v) of food-grade kiwi protease powder preparation solution and 8.0% (w / v) of food-grade microbial transglutaminase powder preparation solution were mixed according to the corresponding injection volume in the example to obtain a mixed enzyme solution. A 23G needle was used to perform a 9-point grid injection into the central area of ​​the foot, with an injection depth of 60% of the foot thickness. The total injection volume at each point was 0.27 mL, for a total of 2.43 mL per abalone. After injection, the abalone was allowed to stand at 18 ℃ for 150 min. The remaining steps, including the pre-cooking and shaping in step 5, the day-night cyclic drying in step 6, and the intermittent UVC irradiation in step 7, were the same as in the example.

[0054] Comparative Example 3 Prepare Comparative Example 3 product. Follow the steps 1, 2, 3 (β-cyclodextrin + citric acid low-temperature deodorization), 4 (center-directed enzyme injection), and 5 (pre-cooking and shaping) as in the example. The difference lies in step 6: instead of using a day-and-night cyclic temperature and humidity controlled drying method, conventional continuous hot air drying was employed. Specifically, the pre-cooked abalone meat was laid flat on a tray and placed in a hot air drying system, continuously dried at 22 ℃ and 55% RH, turning it over every 6 hours until the finished product moisture content reached 17.0%. In step 7, UVC intermittent surface sterilization treatment was performed under the same conditions as in the example. After drying, the samples were cooled at room temperature for 30 min and then vacuum-packed.

[0055] Comparative Example 4 Prepare the product of Comparative Example 4. Complete steps 1 and 2 as in Example 1. Then skip the low-temperature deodorization treatment in step 3, the center-directed enzymatic hydrolysis and cross-linking steps in step 4, and the intermittent UVC irradiation treatment in step 7, and directly proceed to step 5 of Example 1 for pre-cooking and setting at 80 °C followed by cooling. The difference is that step 6 does not employ a day-and-night cyclic temperature and humidity controlled drying method, but instead uses the same conventional continuous hot air drying method as Comparative Example 3. After drying, the sample is cooled at room temperature for 30 min and then vacuum-packed.

[0056] The textural properties (TPA) of the dried soft-boiled abalone prepared in the examples and comparative examples 1-4 are shown in Table 1.

[0057] Table 1

[0058] As shown in Table 1, the hardness of the central region in the example was 323.96±14.87, which was lower than that of Comparative Example 1 (347.82±13.68), Comparative Example 2 (336.24±12.54), Comparative Example 3 (365.78±15.86), and Comparative Example 4 (392.47±16.91). This indicates that the process of the present invention can reduce the hardness of the central region of abalone, making the central tissue more soft and tender. The adhesiveness of the central region in the example was -35.62±3.87, which was higher than that of Comparative Example 1 (29.63), Comparative Example 2 (31.47), Comparative Example 3 (23.58), and Comparative Example 4 (17.86). This indicates that the central tissue in the example had stronger adhesiveness, which is more in line with the sticky and glutinous texture of the center of dried abalone.

[0059] Meanwhile, the edge region hardness of the example was 402.44±14.02, significantly higher than the central region's 323.96±14.87, indicating the formation of a texture gradient with a hard outer layer providing support and a soft, sticky center. In contrast, the central region hardness of Comparative Example 4 was as high as 392.47±16.91, with a small difference between the center and edge hardness, indicating insufficient softening of the center and difficulty in forming a distinct soft-core structure. The springiness and resilience of the central region of the example were 0.98±0.03 and 0.88±0.03, respectively, both higher than Comparative Example 4's 0.90±0.04 and 0.77±0.02, indicating that the protease-based tenderizing followed by microbial transglutaminase cross-linking treatment used in this invention can maintain good springiness and resilience while reducing central hardness. The above results demonstrate that the process of this invention can effectively construct a soft-core texture with a sticky center and a well-formed outer layer providing support.

[0060] Depend on Figure 1 It is evident that the overall sensory quality of the Example is superior to that of the comparative examples. The overall acceptability of the Example is 8.40, higher than that of Comparative Example 1 (7.33), Comparative Example 2 (7.12), Comparative Example 3 (6.70), and Comparative Example 4 (6.10), indicating that the process of the present invention can significantly improve the overall sensory acceptability of the product. The center soft and sticky texture of the Example is 7.90, higher than that of the comparative examples, indicating that the phased enzymatic regulation of the center is more conducive to forming a soft and sticky texture. The fishy smell intensity of the Example is lower than that of Comparative Example 1 and Comparative Example 4; the oxidized rancid smell is 2.90, lower than that of Comparative Example 3 and Comparative Example 4, indicating that low-temperature synergistic deodorization and day-night cyclic drying help reduce undesirable flavors. Comparative Example 4 has an outer hard shell texture of 7.81, but a center soft and sticky texture of only 4.52, indicating that conventional processes tend to result in a hard outer shell and insufficient center softness. The above results show that the process of the present invention can improve flavor cleanliness, center soft texture, and overall acceptability.

[0061] Depend on Figure 2 As can be seen, the total bacterial counts of the Examples, Comparative Examples 1, 2, and 3 were not significantly different, but were significantly lower than the 3.30 log CFU / g of Comparative Example 4. Comparative Example 4, which did not employ a comprehensive treatment including low-temperature synergistic deodorization, central enzymatic regulation, and intermittent UVC sterilization, had the highest total bacterial count, indicating that conventional processes are insufficient in controlling surface microorganisms during drying. Although Comparative Example 3 used UVC treatment, its total bacterial count under continuous hot air drying conditions was still higher than that of the Examples, indicating that day-night cyclic temperature and humidity control drying is more conducive to processing stabilization. The above results demonstrate that the process of this invention can effectively reduce the surface microbial load of dried abalone and improve product processing safety.

[0062] Depend on Figure 3 As can be seen, the peroxide value (POV) of the example was 3.97 meq / kg, which was lower than that of Comparative Example 1 (4.24 meq / kg), Comparative Example 2 (4.15 meq / kg), Comparative Example 3 (4.76 meq / kg), and Comparative Example 4 (4.98 meq / kg). Comparative Example 3 used continuous hot air drying, resulting in a significantly higher POV, indicating that continuous dehydration processes more easily promote the accumulation of primary lipid oxidation products. Comparative Example 4 lacked synergistic deodorization and drying stabilization treatments, resulting in the highest degree of oxidation. The example had the lowest POV, indicating that low-temperature deodorization with β-cyclodextrin-citric acid and 24-hour cyclic drying helped reduce the level of primary lipid oxidation.

[0063] Depend on Figure 4 As can be seen, the thiobarbituric acid reactants (TBARS) in the example were 0.59 mg MDA / kg, lower than 0.66 mg MDA / kg in Comparative Example 1, 0.63 mg MDA / kg in Comparative Example 2, 0.75 mg MDA / kg in Comparative Example 3, and 0.81 mg MDA / kg in Comparative Example 4. Comparative Examples 3 and 4 showed significantly higher TBARS, indicating that continuous hot air drying and a lack of comprehensive regulation make it easier to form secondary lipid oxidation products such as malondialdehyde. Although Comparative Examples 1 and 2 showed lower levels than Comparative Examples 3 and 4, they were still higher than the example, indicating that single deodorization or simultaneous enzyme treatment is less effective than the present invention in controlling oxidative off-odors. The above results demonstrate that the process of the present invention can reduce the level of secondary lipid oxidation and decrease the formation of oxidative rancidity.

[0064] Depend on Figure 5As can be seen, the final moisture content of each treatment group was quite similar, with no significant differences. Specifically, the moisture content of Examples 1, 2, and 3 was generally within the range of 16.69%–16.88%, while Comparative Example 4 was slightly lower, but overall all were close to the drying endpoint. This result indicates that the treatment groups were compared under similar endpoint moisture conditions. Subsequent differences in texture, rehydration rate, oxidation index, and flavor profile mainly stemmed from differences in deodorization methods, enzymatic regulation methods, drying methods, and UVC intermittent sterilization treatment, rather than solely from differences in endpoint moisture content. Therefore, these moisture results support the comparability of the effects of different processing techniques.

[0065] Depend on Figure 6 As can be seen, the embodiments exhibited high rehydration rates at each rehydration stage. After 12 hours of rehydration, the embodiment achieved 85.1±2.6%, higher than Comparative Examples 1, 2, and 3; after 36 hours of rehydration, the embodiment reached 198.6±3.1%, significantly higher than Comparative Example 1's 160.7±2.1% and Comparative Example 3's 155.6±3.1%; after 72 hours of rehydration, the embodiment achieved 255.7±4.0%, still higher than Comparative Examples 1 and 3. This demonstrates that the day-and-night cyclic temperature and humidity controlled drying of the present invention can reduce surface densification, promote moisture reinfiltration, and improve rehydration performance.

[0066] Depend on Figure 7 As can be seen, there are significant differences in the electronic nose response profiles among the different treatment groups. The overall response of the examples is relatively balanced, with a response of 6.0 on the nitrogen oxide response sensor (W5S), which is significantly lower than that of Comparative Examples 1 and 4, indicating that the examples have less accumulation of nitrogen-containing or irritating volatiles. Meanwhile, the response of the examples on the methyl compound response sensor (W1S) is 1.60, which is lower than that of Comparative Examples 1, 3, and 4, indicating that the process of the present invention can reduce the release of methyl volatiles and related odor substances. The sensor responses of Comparative Example 3 are higher than those of the examples, indicating that continuous hot air drying easily aggravates the formation of oxidation or odor-related volatiles; Comparative Example 4 shows high responses on both W5S and W1S, indicating that the accumulation of undesirable volatiles is more obvious under conventional processes. Overall, the electronic nose flavor profile of the examples is more balanced, indicating that low-temperature synergistic deodorization, central fractional enzymatic regulation, and day-night cyclic drying help reduce the contribution of undesirable odors and improve the flavor harmony of the finished product.

[0067] Depend on Figure 8It is evident that the composition of volatile flavor compounds in dried soft-boiled abalone from different treatment groups differs significantly. In the examples, furfural, 2-ethylpyrazine, phenolic derivatives, benzaldehyde derivatives, phenethyl alcohol, methylthion, and 2,3-butanedione exhibited high responses, indicating that the process of the present invention is beneficial for forming sweet, cooked, roasted, and moderately umami aromas. Meanwhile, hexanal, heptanal, octanal, nonanal, trans-2-octenal, trans-2-nonenal, 2,4-decadienal, 1-penten-3-ol, octen-3-ol, and 2-pentylfuran, which are related to lipid oxidation and fishy odor, showed low overall responses, indicating that the examples can reduce the accumulation of oxidized off-odors and fishy odors.

[0068] Compared to the examples, Comparative Example 1 used only citric acid for deodorization, resulting in enhanced responses from some aldehydes, alcohols, and ketones, indicating that citric acid treatment alone has limited effectiveness in controlling fishy and oxidized off-flavors. Comparative Example 2 used simultaneous injection of protease and microbial transglutaminase; although some cooked and sweet aroma compounds were retained, lipid oxidation-related aldehydes increased compared to the examples, indicating that simultaneous enzyme treatment is not conducive to maintaining a stable flavor structure. Comparative Example 3 used continuous hot air drying, resulting in enhanced responses from unsaturated aldehydes, ketones, and alcohols, indicating that continuous dehydration processes more readily promote lipid oxidation. In Comparative Example 4, oxidation-related volatiles such as hexanal, heptanal, octanal, nonanal, and 2-pentylfuran showed the strongest responses, while sweet and cooked aroma compounds were relatively insufficient, indicating that conventional processes resulted in significant accumulation of oxidized fishy odors and the worst flavor quality. These results demonstrate that the process of this invention can optimize the volatile flavor composition of dried abalone with a soft center, reduce undesirable oxidized flavors, and improve the flavor harmony of the finished product.

[0069] The embodiments provided above are not intended to limit the scope of the invention, nor are the described steps intended to limit the order of execution. Any obvious modifications made to the invention by those skilled in the art based on existing common knowledge also fall within the scope of protection defined by the claims.

Claims

1. A method for preparing dried abalone with a soft center, characterized in that, Includes the following steps: S1. Raw material pretreatment and low-temperature deodorization: After removing the shells and internal organs of the abalone and cleaning them, they are washed with salt to remove the black membrane, salted and desalted, and then placed in a deodorizing soaking solution composed of β-cyclodextrin, citric acid and water for low-temperature soaking. S2. Centralized enzymatic regulation and pre-cooking shaping: The central area of ​​the abalone foot after deodorization is injected at multiple points in a directional manner. First, protease solution is injected and allowed to stand to form a tenderizing window. Then, cross-linking enzyme solution is injected at the same or similar points and allowed to stand to form a cross-linking window. After that, pre-cooking enzyme inactivation shaping treatment is performed. S3. Day and night cycle temperature and humidity controlled drying: The abalone is placed in a temperature and humidity controlled drying equipment for cycle drying, with dehydration drying during the daytime stage and moisture rehydration and equalization control at night; S4. Intermittent UVC irradiation and finished product acquisition: During the drying process, abalone is subjected to intermittent UVC irradiation for sterilization. After drying, it is cooled and packaged to obtain dried soft-boiled abalone products.

2. The method according to claim 1, characterized in that, In S1, the content of β-cyclodextrin in the deodorizing soaking solution is 0.30%~0.80%, and the content of citric acid is 0.10%~0.30%; the low-temperature soaking temperature is 0~5℃, and the time is 1~3h.

3. The method according to claim 1, characterized in that, In S2, the protease solution is kiwi protease, the cross-linking enzyme solution is microbial transglutaminase solution, and the injection points are 5 to 15 points, with an injection depth of 40% to 80% of the thickness of the abalone foot.

4. The method according to claim 1, characterized in that, In S2, the protease solution is prepared from 800 U / g food-grade kiwi protease powder at a concentration of 4.0% to 12.0%; based on a net weight of 60 to 70 g for a single abalone, the total injection volume of protease solution for each abalone is 0.8 to 2.5 mL.

5. The method according to claim 1, characterized in that, In S2, the cross-linking enzyme solution is prepared by 4.0% to 12.0% of 100 U / g food-grade microbial transglutaminase powder; based on a net weight of 60 to 70 g for a single abalone, the total injection volume of cross-linking enzyme solution for each abalone is 0.3 to 1.5 mL.

6. The method according to claim 1, characterized in that, In S2, the tenderizing window temperature is 8~15℃ and the time is 10~60min; the cross-linking window temperature is 18~30℃ and the time is 40~240min.

7. The method according to claim 1, characterized in that, In S2, the pre-cooking temperature is 75~85℃, so that the center temperature of the abalone reaches 75~80℃ and is maintained for 2~5 minutes.

8. The method according to claim 1, characterized in that, In S3, the day and night temperature and humidity control drying cycle is in 24-hour intervals. The daytime temperature is 18~30℃ and the relative humidity is 50%~75%, while the nighttime temperature is 8~15℃ and the relative humidity is 75%~95%.

9. The method according to claim 1, characterized in that, In S4, the center wavelength of the UVC is 254 nm, and the irradiation intensity is 0.5~0.8 mW / cm². 2 The lamp distance is 15~30 cm; during the daytime, irradiate 1~2 times, each time for 2~5 minutes. After each irradiation, turn the sample over or adjust its placement. Do not irradiate at night.

10. Dried soft-boiled abalone prepared by any one of the methods described in claims 1 to 9.

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