Method for preparing instant sea bass cooking product by combining subacid electrolyzed water with ultrahigh pressure technology

Abstract

The invention belongs to the technical field of aquatic product processing, and discloses a method for preparing instant-cooking jewfish products by combining subacid electrolyzed water with an ultrahigh pressure technology. According to the invention, a subacid electrolyzed water process, a pickling and fishy smell removal process, a seasoning process and an ultrahigh pressure sterilization treatment process are successfully optimized. The SAEW treatment can maintain the color and texture stability of the fish meat. The content of fishy smell substances such as hexanal, heptanal and dimethyl trisulfide is remarkably reduced through pickling and cooking, aromatic substances such as limonene and alpha-terpilenol are generated, and the finished product is more harmonious in flavor and distinct in layer. The ultrahigh-pressure treatment can prolong the storage period and maintain the texture and taste of the fish meat. Results show that the process flow can significantly improve the product quality, prolong the shelf life and maintain good sensory quality, and a scientific basis is provided for industrial production of instant-cooking weever products.

Description

Technical Field

[0001] This invention belongs to the field of aquatic product processing technology, and more specifically relates to a method for preparing ready-to-cook sea bass products using a combination of slightly acidic water electrolysis and ultra-high pressure technology. Background Technology

[0002] Sea bass is a common and economically valuable marine fish found along my country's coast. Its flesh is delicate and delicious, rich in high-quality protein, unsaturated fatty acids, and various trace elements, making it highly valuable in dietary nutrition. Sea bass has been used in traditional medicine for its nourishing properties, documented in numerous herbal texts throughout history, offering benefits such as improving liver and spleen health, strengthening the stomach, and fortifying muscles and bones. Currently, the main forms of distribution for sea bass in the market are still fresh sales or initial frozen processing. However, these two methods are gradually revealing limitations in the industry's development, failing to meet the demands of modern consumers for convenient, high-quality aquatic products. Because sea bass is rich in nutrients and water, its muscle tissue is susceptible to endogenous enzymatic reactions and microbial contamination, leading to quality degradation and even spoilage. Therefore, optimizing sea bass processing and preservation techniques to improve product stability, extend shelf life, and enhance added value has become a key focus of current research.

[0003] With the fast pace of modern life, consumer demand for ready-to-eat and ready-to-cook aquatic products is increasing. The distinctive fishy smell of sea bass often affects its taste and quality. Traditional deodorization methods primarily rely on salt curing. However, during the curing process, parameters such as salt concentration, curing time, and spice concentration are easily affected by the quality of raw materials and the instability of processing techniques, making it difficult to maintain consistent product quality. Therefore, optimizing the curing process and scientifically and rationally controlling process conditions to improve the deodorization effect is of great significance to the food processing industry.

[0004] Slightly acidic electrolyzed water (SAEW) is a novel non-thermal sterilization technology that has garnered widespread attention in the food industry both domestically and internationally due to its safety, environmental friendliness, high efficiency, broad-spectrum antibacterial properties, and ability to effectively maintain food quality. SAEW is prepared by electrolyzing saturated saline or dilute hydrochloric acid. It possesses a certain oxidizing capacity, effectively killing bacteria, viruses, and other microorganisms while maintaining high safety for humans and the environment. Compared to traditional chemical disinfectants, slightly acidic electrolyzed water features low chlorine residue and no secondary pollution. It has demonstrated broad application potential in various fields, including food processing, medical and health care, and agriculture. Especially in the field of food safety, slightly acidic electrolyzed water is considered a highly promising non-thermal sterilization method.

[0005] Ultra-high pressure (UHPP) sterilization is a technology that sterilizes food under high pressure. Its advantage lies in its ability to process food at low temperatures, avoiding the loss of nutrients and alterations in taste associated with traditional heat treatment. However, studies have indicated that high-pressure treatment can cause irreversible denaturation of myofibrillar proteins and thiol oxidation. Other research has found that under specific conditions, high-pressure treatment may induce lipid oxidation and increase free radical oxidase (FFA), necessitating careful control of treatment intensity and environmental conditions.

[0006] Therefore, how to provide a method for preparing ready-to-cook sea bass products using slightly acidic water electrolysis combined with ultra-high pressure technology is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0007] In order to overcome the shortcomings and deficiencies of the existing technology, the present invention provides a method for preparing ready-to-cook sea bass products using slightly acidic water electrolysis combined with ultra-high pressure technology.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: A method for preparing ready-to-cook sea bass products using slightly acidic water electrolysis combined with ultra-high pressure technology, characterized by comprising the following steps: (1) Remove the head, tail, scales, gills and internal organs from the fresh sea bass, cut it in half and remove the backbone. Remove the muscles on both sides along the main bone, clean them and get fish fillets for later use. (2) Using a slightly acidic electrolyzed water generator, add electrolytes to prepare slightly acidic electrolyzed water with a certain effective chlorine concentration; soak the fish fillets in the slightly acidic electrolyzed water for treatment, then take out the fish fillets, drain them until there are no water droplets on the surface, and place them in the marinating solution for marinating; (3) After marinating, drain the fish fillets, wipe off the surface water droplets, place the fish fillets in a container filled with cooling water, and perform ultra-high pressure sterilization. (4) Add oil, garlic and onion to the pot and stir-fry. Then add the sauce, heat and stir-fry, cool, and obtain the sauce packet. Seal and store. (5) To cook, add the sterilized fish fillets and sauce packet to the pot, mix well and heat, simmer to obtain the ready-to-cook sea bass product, and seal and store.

[0009] Preferably, the effective chlorine concentration of the slightly acidic electrolyzed water in step (2) is 70-80 mg / L, and the treatment time is 30 min.

[0010] Preferably, in step (2), the ratio of fish fillets to marinade is 1g:2mL, the temperature is 4℃, and the time is 119min.

[0011] Preferably, the marinating liquid in step (2) includes the following ingredients: salt solution, scallion and ginger cooking wine, Sichuan peppercorns, and rice vinegar.

[0012] Preferably, the salt concentration in the pickling solution is 4%; Based on the weight of the fish fillets, the amount of scallions, ginger, and cooking wine added is 3.7%, the amount of Sichuan peppercorns added is 3%, and the amount of rice vinegar added is 1%.

[0013] Preferably, the pressure of the ultra-high pressure sterilization process in step (3) is 500 MPa and the time is 5 min.

[0014] Preferably, the amount of oil added in step (4) is 6% of the mass of the fish fillet.

[0015] Preferably, the sauce in step (4) includes the following ingredients: water, broad bean paste, sweet bean sauce, brewed soy sauce, oyster sauce, white sugar, aged vinegar, chicken essence, pepper powder, yeast extract, and disodium 5'-inosinate.

[0016] Preferably, based on the weight of the fish fillets, the amount of fermented soybean paste added is 3%, the amount of sweet bean sauce added is 4%, and the amount of brewed soy sauce added is 1.5%.

[0017] Preferably, the heating and frying temperature in step (4) is 150-210℃ and the time is 8min.

[0018] Preferably, the mixing and heating temperature in step (5) is 120-150℃, and the simmering time is 10 min.

[0019] As can be seen from the above technical solutions, this invention deeply explores the processing technology and preservation technology of ready-to-cook sea bass products, and successfully optimizes the slightly acidic electrolytic water process, the marinating and deodorizing process, the seasoning process, and the ultra-high pressure sterilization process. The results show that the above process can significantly improve product quality, extend shelf life, and maintain good sensory quality, providing a scientific basis for the industrial production of ready-to-cook sea bass products and a valuable reference for processing and preservation technologies in related fields. It has the following beneficial effects: (1) This invention investigated the antibacterial and preservative effects of slightly acidic electrolyzed water (SAEW) treatment on sea bass raw materials during refrigeration. Experimental results showed that SAEW treatment with high effective chlorine concentrations (70 mg / L and 80 mg / L) significantly inhibited the growth of microorganisms in the fish meat, delayed fat oxidation and protein degradation, and effectively extended the shelf life of the fish meat. SAEW treatment can maintain the color and texture stability of the fish meat, providing a good foundation for subsequent steps such as pickling, sterilization, packaging, and storage, and ensuring the quality of the product.

[0020] (2) The marinating and deodorizing process and seasoning optimization of sea bass were studied. The optimal marinating formula for sea bass was determined by response surface methodology: marinating time 119 minutes, salt concentration 4%, scallion, ginger and cooking wine 3.7%, and Sichuan pepper 3%. The seasoning process was optimized by orthogonal experiments, and the final seasoning formula significantly improved the sensory score of the product. The changes of key flavor compounds during marinating and cooking were analyzed by GC-MS and GC-IMS. The results showed that marinating and cooking significantly reduced the content of fishy substances such as hexanal, heptanal, and dimethyl trisulfide, and generated aromatic substances such as limonene and α-terpineol, making the flavor of the finished product more harmonious and layered.

[0021] (3) The preservation effect of ultra-high pressure sterilization (HPP) on ready-to-cook sea bass products was studied. Experiments showed that HPP treatment at 500 MPa and 600 MPa effectively delayed fish spoilage, reduced the accumulation of volatile basic nitrogen, slowed lipid oxidation, and significantly extended the shelf life of the product. It also showed excellent results in maintaining the color and texture of the fish meat. The 500 MPa treatment group exhibited the best overall performance, extending the storage period while maintaining the texture and taste of the fish meat. This provides green and efficient preservation technology support for the industrial processing and cold chain storage of ready-to-cook sea bass products. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. The drawings in this description are merely embodiments of the present invention.

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0024] Figure 1 The effect of SAEW treatment on total bacterial count during fish refrigeration.

[0025] Figure 2 The effect of SAEW treatment on TVB-N during fish refrigeration.

[0026] Figure 3 The effect of SAEW treatment on the thiobarbituric acid value of fish during cold storage.

[0027] Figure 4 The effect of SAEW treatment on pH during fish refrigeration.

[0028] Figure 5The effect of SAEW treatment on the hardness of fish meat during refrigeration.

[0029] Figure 6 The effect of SAEW treatment on the elasticity of fish meat during cold storage.

[0030] Figure 7 The effect of HPP treatment on the total bacterial count of ready-to-cook sea bass products during refrigeration.

[0031] Figure 8 The effect of HPP treatment on TVB-N during refrigeration of ready-to-cook sea bass products.

[0032] Figure 9 The effect of HPP treatment on the thiobarbituric acid value of ready-to-cook sea bass products during refrigeration.

[0033] Figure 10 The effect of HPP treatment on pH during refrigeration of ready-to-cook sea bass products.

[0034] Figure 11 The effect of HPP treatment on the hardness of ready-to-cook sea bass products during refrigeration.

[0035] Figure 12 The effect of HPP treatment on the elasticity of ready-to-cook sea bass products during refrigeration.

[0036] Figure 13 The effect of HPP treatment on water retention during refrigeration of ready-to-cook sea bass products.

[0037] Figure 14 Principal component analysis (PCA) plots of untreated, marinated, and cooked fish samples.

[0038] Figure 15 The GC-MS total ion chromatograms of three fish samples are shown; where A is untreated, B is marinated, and C is cooked.

[0039] Figure 16 Comparison of GC-IMS fingerprints of untreated, pickled and cooked fish samples. Detailed Implementation

[0040] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0041] Experiment 1: Study on the antibacterial and preservative effects of slightly acidic electrolyzed water treatment on sea bass 1.1 Experimental Methods 1.1.1 Preparation of slightly acidic electrolyzed water A slightly acidic electrolyzed water generator was used, with 3% HCl solution and 0.5% NaCl solution as electrolytes. The voltage and current of the equipment were adjusted according to the required electrolyzed water parameters to prepare electrolyzed water with different available chlorine concentrations (ACC). Based on the national standard GB 28234-2020 "Slightly Acidic Electrolyzed Water Generator" and experimental feasibility, 40, 50, 60, 70, and 80 mg / L were selected as the available chlorine concentration gradient. pH and redox potential were measured using a pH meter and an ORP meter, respectively, and the available chlorine concentration was determined using iodometric titration. The prepared electrolyzed water was stored in sealed bags at 4°C and used within 1-2 days. The pH and ORP values ​​corresponding to slightly acidic electrolyzed water with different available chlorine concentrations are shown in Table 1.

[0042] Table 1. pH and ORP values ​​corresponding to SAEW with different ACC values.

[0043] 1.1.2 Sample Preparation Fresh sea bass were deheaded, tailed, scaled, gilled, and viscerated. The fish was halved, the spine removed, and the muscles on both sides were carefully removed along the main bone. The fillets were cleaned, dried, and randomly divided into 6 groups according to storage days, with 3 parallel experiments per group. Samples were immersed in sterile distilled water (CK) and SAEW solutions with different effective chlorine concentrations for 30 minutes each. After draining until no water remained on the surface, the samples were placed in sterile bags, labeled, and refrigerated at 4℃. Finally, the fillets were cut into 8×2×1 cm (40±1 g) pieces, and relevant indicators were measured at 0, 2, 4, 6, 8, and 10 days.

[0044] 1.1.3 Determination of total bacterial count The assay method followed GB4789.2-2016 "Microbiological Examination of Food - Determination of Total Colony Count". 25 g of fish sample was weighed and placed in a sterile homogenizing cup containing 225 mL of sterile physiological saline. The homogenate was homogenized at 10000 r / min for 1 min to prepare a 1:10 sample homogenate. Subsequently, a 10-fold serial dilution was performed using a sterile pipette and sterile water. 1 mL of each dilution was inoculated into sterile Petri dishes, with two replicates for each dilution. PCA counting agar was then added to the Petri dishes, and the dishes were incubated at 37℃ for 48 h before the results were observed.

[0045] 1.1.4 Determination of TVB-N value The determination method follows GB5009.228-2016 "Determination of Volatile Basic Nitrogen in Food". Weigh 10g of fish sample, crush it evenly, and use it. Use an automatic Kjeldahl nitrogen analyzer for determination, with 0.1000 mol / L hydrochloric acid standard titration solution as the standard solution. Set the boric acid receiving liquid volume to 30 mL, and the distillation conditions to 180 s or 200 mL (whichever comes first). The titration endpoint is determined using a mixed indicator solution.

[0046] 1.1.5 Determination of Thiobarbituric Acid Value The determination method was performed according to GB5009.181-2016 "Determination of Malondialdehyde in Food". Weigh 5 g of sample into a 100 mL Erlenmeyer flask, add 50 mL of trichloroacetic acid mixture (37.50 g trichloroacetic acid and 0.50 g disodium ethylenediaminetetraacetate, dissolved and diluted with water to 500 mL), shake well, seal, and shake in a 50°C constant temperature shaker for 30 min. Remove and cool to room temperature, filter, and collect the filtrate. Take 5 mL of the filtrate and the standard series solutions into a 25 mL colorimetric tube, and take another 5 mL of the trichloroacetic acid mixture as a sample blank. Add 5 mL of thiobarbituric acid (TBA) solution to each, mix well, and react in a 90°C water bath for 30 min, then cool to room temperature. For the determination, zero the instrument with the sample blank and measure the absorbance of the sample solution and the standard solution at a wavelength of 532 nm. Plot a standard curve with the mass concentration of the standard solution on the x-axis and the absorbance on the y-axis.

[0047] 1.1.6 pH value determination pH was determined according to GB5009.237-2016 "Determination of pH Value in Food". A 5 g sample of fish meat was homogenized, and 50 mL of 0.1 mol / L potassium chloride solution was added. The mixture was thoroughly mixed using a homogenizer. The pH was then measured using a pH meter, and after the reading stabilized, it was accurately recorded to a value of 0.01. The same sample should be measured twice to ensure accuracy.

[0048] 1.1.7 Determination of colorimetric values Take 3 g of fish paste, homogenize it, and place it in a 12-well plate. Use a handheld colorimeter to measure the color of the fish paste (using the sample from day 0 of the control group as the standard color, and calculate the ΔE value). Take 3 samples for each group, and obtain 3 sets of data for each measurement. Take the average value. The formula for calculating the ΔE value is as follows:

[0049] 1.1.8 Determination of texture The hardness and elasticity of the fish fillets were measured using a texture analyzer (TPA) (hardness was measured in gF, and elasticity was expressed as the recovery of deformation after the first compression, in mm). Six parallel samples were tested for each sample. Before testing, the samples were allowed to equilibrate at room temperature for a period of time, and then the fish fillets were cut into small cubes of 2×2×1 cm. The texture testing parameters were set as follows: (1) Probe type TA-10; (2) Triggering force 5.0 g; (3) Measurement speed 1 mm / s; (4) Compression ratio 30%; (5) Interval between two compressions 3 s.

[0050] 1.1.9 Data Analysis Experimental data were organized using Microsoft Excel 2016, plotted using Origin 2022, and analyzed using SPSS 20.

[0051] 1.2 Results and Discussion 1.2.1 Effect of SAEW treatment on total bacterial count in sea bass during cold storage Total bacterial count (TVC) is an important indicator for assessing the microbial safety of food and a commonly used standard for reflecting the degree of spoilage of aquatic products. Generally, referring to national standards, when the TVC reaches 6 logCFU / g, the microbial contamination of aquatic products is close to an unacceptable level; products exceeding this threshold are not suitable for consumption. Therefore, assessing the impact of SAEW on the TVC of fish samples can provide a valid basis for evaluating preservation effectiveness. Figure 1 Overall, the total bacterial count in all groups increased with prolonged storage time. In the experimental groups, the rate of increase in total bacterial count gradually slowed with increasing effective chlorine concentration of SAEW, indicating that higher concentrations of SAEW had a stronger inhibitory effect on microbial growth. Among the experimental groups, the 70 mg / L and 80 mg / LACC SAEW treatments showed the best antibacterial effects, with no significant difference between the two groups (P>0.05). By day 10 of storage, the total bacterial count was below 6 logCFU / g, significantly lower than the 40 mg / L and 50 mg / L groups (P<0.05). The 40 mg / L group also showed some antibacterial effect in the early stages (first 4 days), but the total bacterial count increased rapidly after day 6, reaching 6.84 logCFU / g, and its antibacterial effect was significantly weaker than the 70 mg / L and 80 mg / L groups. In summary, high concentrations (70 mg / L and 80 mg / L) of SAEW treatment can significantly inhibit the growth of total bacterial count in fish samples during refrigeration, effectively extending the storage period.

[0052] 1.2.2 Effects of SAEW treatment on TVB-N during sea bass refrigeration TVB-N (volatile basic nitrogen) is an important physicochemical indicator reflecting the protein decomposition and spoilage degree of aquatic products. According to national standards and related research, when the TVB-N value exceeds 30 mg / 100 g, the aquatic products have entered the spoilage stage and are no longer suitable for consumption. Evaluating the impact of SAEW treatment on the TVB-N value of fish samples is of great significance for determining the preservation effect. Figure 2 As can be seen, the TVB-N values ​​of all groups increased with prolonged storage time. The TVB-N value of the control group (CK) increased the fastest during storage, reaching 30.93 mg / 100 g on day 10, which was higher than that of the experimental groups. This indicates that under untreated conditions, the fish samples spoiled faster, microbial activity increased, and protein decomposition was significant. With increasing SAEW concentration, the increase in TVB-N values ​​of all treatment groups gradually slowed down. In the experimental groups, the 40 mg / L SAEW treatment had a better inhibitory effect on TVB-N values ​​than the CK group, but the TVB-N value increased significantly in the later stage of storage, reaching 26.92 mg / 100 g. The TVB-N values ​​of the 70 mg / L and 80 mg / L treatment groups remained at a relatively low level during storage, only slightly exceeding 18 mg / 100 g on day 10, which was significantly lower than other experimental groups (P<0.05). This indicates that high concentrations of SAEW treatment can effectively inhibit the decomposition of fish protein and delay spoilage. In summary, high concentrations of SAEW treatment (70 mg / L and 80 mg / L) significantly reduced TVB-N accumulation in fish samples during refrigeration, extending shelf life. Electrolyzed water treatment effectively inhibited protein degradation, slowed spoilage of aquatic products, and improved storage stability and shelf life.

[0053] 1.2.3 Effect of SAEW treatment on thiobarbituric acid value of sea bass during cold storage TBARS (Thiobarbituric Acid Reactive Materials) is an important indicator for assessing the degree of fat oxidation in aquatic products, reflecting the content of substances such as thiobarbituric acids produced during fat oxidation during storage. It is generally believed that the degree of fat oxidation in aquatic products gradually increases with prolonged storage time; an elevated TBARS value indicates severe fat oxidation, affecting the flavor and quality of the product. Figure 3As can be seen, the TBARS values ​​of all groups increased with prolonged storage time. The control group (CK) had the highest TBARS value during storage, reaching 0.79 mg / kg on day 10, significantly higher than all SAEW treatment groups, indicating that the control group experienced higher and faster fat oxidation during refrigeration. In the SAEW treatment groups, the rate of increase in TBARS values ​​gradually slowed down with increasing available chlorine concentration. The 40 mg / L group had a slightly higher TBARS value than the other experimental groups, reaching 0.65 mg / kg on day 10. The 50 mg / L treatment group had the lowest degree of fat oxidation, maintaining a TBARS value of 0.54 mg / kg on day 10, significantly lower than the other treatment groups (P<0.05). This indicates that 50 mg / L SAEW treatment can effectively slow down fat oxidation and extend the shelf life of fish samples. The reason why the TBARS values ​​at concentrations of 40, 60, 70, and 80 mg / L are higher than those at 50 mg / L may be that lower available chlorine concentrations (ACC) are insufficient to effectively inhibit lipid oxidation, while higher ACC may accelerate oxidation and increase its oxidation products. In summary, SAEW treatment significantly inhibits lipid oxidation in fish samples during refrigeration, maintains the quality and flavor of aquatic products, and extends their shelf life.

[0054] 1.2.4 Effect of SAEW treatment on pH during sea bass refrigeration pH value is a commonly used physicochemical indicator for evaluating the quality of aquatic products, and its changes are closely related to the freshness and spoilage of fish. The pH value of fish is usually affected by both the accumulation of lactic acid and the alkaline substances produced by protein decomposition. Figure 4 In the study, the pH values ​​of different treatment groups showed a trend of first decreasing and then increasing with the increase of storage days, and the pH values ​​of each treatment group showed significant differences at different time points. Figure 4As shown, on day 0, the pH value of all experimental groups treated with SAEW was significantly lower than that of the control group (P<0.05), which may be due to the acidic effect of the electrolyzed water treatment and the acidic substances produced by the initial ATP decomposition. During days 0-4, the pH value decreased slightly due to the accumulation of lactic acid and the formation of acidic substances such as phosphoric acid in the fish meat. With prolonged storage, the fish meat entered the autolysis stage, and proteins gradually decomposed into alkaline substances such as amino acids and amines, causing the pH value to rise. From day 4 to day 10 of storage, the pH value of all treatment groups rebounded. The control group showed the fastest pH increase, reaching 7.325 on day 10, indicating that the fish meat was already in a relatively severe spoilage stage at this time. The 70 mg / L and 80 mg / L SAEW treatment groups showed a slower rate of pH increase, and the pH value remained below 7 on day 10, significantly lower than the control group (P<0.05). In summary, SAEW treatment significantly reduced the pH value of fish meat in the early stages of storage and maintained a relatively stable pH level during refrigeration. Higher concentration treatments showed even more significant effects. SAEW treatment plays a crucial role in delaying autolysis and spoilage of fish meat, effectively maintaining the stability of fish meat quality.

[0055] 1.2.5 Effect of SAEW treatment on color of sea bass during cold storage During the storage of aquatic products, reactions such as fat oxidation, protein denaturation, and pigment degradation lead to changes in their color. Table 2 shows the changes in color values ​​of each group with prolonged storage time. The values ​​in Table 2 are mean ± standard deviation (n = 3), and different lowercase letters in the same row indicate significant differences (P < 0.05). The L value represents the brightness of the sample. As can be seen from Table 2, the L values ​​of all samples generally showed a decreasing trend with prolonged storage time, but the differences between the treatment groups were significant (P < 0.05). On day 0, the 70 mg / L treatment group had the highest L value, reaching 60.49 ± 0.43, significantly higher than other treatment groups. This indicates that high-concentration SAEW treatment can maintain high brightness in the early stages of storage. The decrease in brightness is usually related to fat oxidation and protein denaturation in the fish meat. After fat oxidation produces peroxides, these react with proteins in the fish meat, causing a decrease in brightness. The decrease in L values ​​for other groups was relatively small. The L value of the 60 mg / L treatment group was 51.77±0.51 on day 10, maintaining a relatively high brightness, indicating that moderate ACC SAEW treatment had a good effect on maintaining brightness. The a value reflects the red-green change of the sample. As can be seen from the table, the a value of all treatment groups showed a decreasing trend with the extension of storage time. On day 0, the a value of the CK group was -1.42±0.23, while by day 10 it decreased to -2.68±0.08, indicating a significant weakening of redness. This change may be related to the decomposition of red pigment by free radicals generated during lipid oxidation. Among all treatment groups, the decrease in a value of the 40 mg / L and 60 mg / L groups was relatively gradual. The 60 mg / L group indicates that moderate concentration SAEW treatment can effectively inhibit the rapid decrease in redness. This shows that moderate SAEW treatment can delay the loss of redness. The b value represents the yellow-blue change of the sample. According to the data in the table, the changes in b values ​​showed significant differences among different treatment groups. The b-value of the 80 mg / L group increased continuously during storage, rising from -0.31 ± 0.17 on day 0 to 0.95 ± 0.13 on day 10. This indicates that high-concentration SAEW treatment led to the gradual accumulation of yellow pigment. The b-values ​​of the 60 mg / L and 70 mg / L treatment groups also fluctuated during storage, but the changes were small. This suggests that moderate concentrations of SAEW treatment can effectively inhibit the formation of yellow pigment and maintain the color stability of the samples. The ΔE value was used to measure the difference between the sample and its initial color. According to the data in the table, the ΔE value of all treatment groups gradually increased with the extension of storage time. On day 0, the ΔE value of the 80 mg / L treatment group was 2.74 ± 0.54, indicating little color change in the early stage of storage; on day 10, the ΔE value of this group rose to 13.20 ± 0.42, indicating a significant difference from the initial color. The ΔE value of the 60 mg / L treatment group changed little in the early stage of storage, and the ΔE value was 6.72±0.41 on the 10th day of storage, with little color change.This indicates that a moderate concentration of SAEW treatment can effectively delay changes in color difference and maintain the color stability of sea bass. In summary, SAEW treatment has a significant impact on the color changes of sea bass samples. The 80 mg / L treatment group showed the most significant decrease in brightness, weakening of redness, and increase in yellowness during storage, indicating that high-concentration SAEW treatment exacerbates lipid oxidation and protein denaturation. The 60 mg / L treatment group showed relatively smaller color changes, indicating that this concentration of SAEW treatment can better maintain the color stability of the samples and delay the occurrence of oxidation reactions.

[0056] Table 2. Effects of SAEW treatment on color of fish during cold storage.

[0057] 1.2.6 Effects of SAEW treatment on the texture of sea bass during cold storage Firmness is an important indicator of a fish fillet's ability to retain its shape. It is directly related to the muscle tissue structure and the strength of the protein gel network, and is also a crucial parameter for assessing fillet quality. During refrigeration, the firmness of fish typically decreases gradually due to protein degradation, muscle fiber separation, and water migration. Figure 5 As can be seen, during refrigeration, the hardness of all treatment groups showed a gradual decreasing trend with the extension of storage time, but the degree of decrease was closely related to the concentration of slightly acidic electrolyzed water. In the early stage of refrigeration (0-4 days), the hardness changes of each treatment group were relatively small, with the 70 mg / L treatment group showing the highest hardness at approximately 4860.90±16.00 gF, while the control group had a slightly lower hardness than the other treatment groups, at approximately 4207.45±116.05 gF. This indicates that high-concentration slightly acidic electrolyzed water had a relatively significant effect on maintaining the hardness of fish fillets in the early stage of refrigeration, possibly related to its inhibition of microbial activity and protein oxidation. In the later stage of refrigeration, the hardness of each treatment group continued to decrease, but the high-concentration treatment group still maintained a certain advantage. On day 10, the hardness of the control group had dropped to the lowest level, approximately 2675.08±157.59 gF, while the hardness of the 80 mg / L treatment group was still maintained at approximately 2921.16±37.46 gF, significantly higher than the control group (P<0.05). The hardness of the 40 mg / L treatment group decreased to approximately 2548.61 ± 50.93 gF, which was not significantly different from the control group. This indicates that high-concentration slightly acidic electrolyzed water treatment has a more significant effect on maintaining hardness in the later stages of refrigeration, while the protective effect of low-concentration treatment tends to weaken in the later stages.

[0058] from Figure 6As can be seen, the elasticity of all treatment groups gradually decreased with prolonged refrigeration time, but the magnitude of elasticity change varied significantly among different concentration treatment groups. Initially, the elasticity of all treatment groups was at a high level. As the storage time increased, the elasticity of the fish fillets gradually decreased, with the control group showing the fastest rate of decrease. On day 10, the elasticity of the control group dropped to approximately 1.45±0.01 mm, the lowest among all treatment groups. The 70 mg / L treatment group exhibited the best elasticity retention throughout the refrigeration period, maintaining approximately 1.47±0.04 mm on day 10, significantly higher than other treatment groups (P<0.05). The elasticity of the 60 mg / L treatment group was close to that of the 70 mg / L group, lower than 70 mg / L but significantly better than the control group. The elasticity decrease trend of the low concentration treatment group was closer to that of the control group, and the protective effect was significantly weakened in the later stages of refrigeration. In conclusion, slightly acidic electrolyzed water has a significant effect on the hardness and elasticity of fish fillets during refrigeration, and its effect increases with increasing concentration. The 70 mg / L treatment group exhibited the best retention of firmness and elasticity throughout the refrigeration process, effectively delaying the decrease in firmness and reduced elasticity of the fish fillets caused by protein degradation, moisture loss, and damage to muscle tissue structure. In contrast, the low-concentration treatment groups (such as 40 mg / L and 50 mg / L) had limited preservation effects in the later stages. Overall, high-concentration slightly acidic electrolyzed water can significantly improve the textural properties of fish fillets during refrigeration, making it suitable for use in extending the shelf life of aquatic products.

[0059] 1.3 Conclusion In summary, this experiment systematically verified the significant preservation effect of SAEW treatment on sea bass. At higher concentrations, it effectively slowed down microbial growth, lipid oxidation, and protein degradation, maintaining the physicochemical quality and sensory characteristics of the fish fillets. The SAEW sterilization treatment effectively reduced the microbial load of the raw fish, laying a solid foundation for subsequent processing steps. Treatment with slightly acidic electrolyzed water inhibited microbial growth and significantly delayed spoilage of the fish during refrigeration. This sterilization treatment improved the hygienic quality of the raw materials, creating more favorable conditions for subsequent marinating, sterilization, packaging, and storage processes. The reduction in microbial load extends the product's shelf life, ensuring that the quality of the fish is maintained throughout the entire processing and storage cycle, thus improving the overall quality of ready-to-cook sea bass pre-prepared products.

[0060] Experiment 2: Study on the Preservation Effect of Ultra-High Pressure Sterilization on Ready-to-Cook Sea Bass Products 2.1 Experimental Methods 2.1.1 Sample Preparation Fresh sea bass were deheaded, tailed, scaled, gutted, and gutted. The fish was halved and the backbone removed. The muscles on both sides were carefully removed along the main bone. The fillets were cleaned and then soaked in a SAEW solution with an effective chlorine concentration of 70 mg / L for 30 min. After treatment, the samples were drained until no water droplets remained on the surface and then placed in a marinating solution (solid-to-liquid ratio 1:1, marinating time 119 min, salt concentration 4%, scallion, ginger, and cooking wine 3.7%, Sichuan peppercorns 3%, rice vinegar 1%) at 4℃ for marinating. After marinating, the samples were drained, surface droplets were wiped off with kitchen paper, and the samples were vacuum-packed in PVC bags and clearly labeled and grouped.

[0061] 2.1.2 Ultra-high pressure sterilization treatment Samples without ultra-high pressure (UHPP) treatment served as the control group. The experimental group samples underwent UHPP sterilization at pressures of 300, 400, 500, and 600 MPa for 5 minutes. Preliminary experiments revealed that longer treatment times (e.g., 10 minutes) could damage the muscle tissue, affecting texture and sensory quality. Therefore, this study selected 5 minutes for the treatment time to balance sterilization effectiveness and tissue integrity. UHPP sterilization employed a water inlet treatment method, placing the samples in a container filled with cooling water. This water inlet treatment helps absorb the heat generated during compression, thus inhibiting temperature rise and preventing thermal damage, effectively preserving texture and sensory quality. After sterilization, all samples were divided into 8×2×1 cm (40±1 g) blocks and stored at 4℃ for further analysis. All indicators were measured on days 0, 4, 8, 12, 16, and 20. Each measurement was repeated three times.

[0062] 2.1.3 Determination of total bacterial count The experimental method is the same as in 1.1.3.

[0063] 2.1.4 Determination of TVB-N value The experimental method is the same as in 1.1.4.

[0064] 2.1.5 Determination of Thiobarbituric Acid Value The experimental method is the same as in 1.1.5.

[0065] 2.1.6 pH value determination The experimental method is the same as in 1.1.6.

[0066] 2.1.7 Determination of colorimetric values The experimental method is the same as in 1.1.7.

[0067] 2.1.8 Determination of texture The experimental method is the same as in 1.1.8.

[0068] 2.1.9 Determination of water holding capacity Take 3 g of sample, wrap it in filter paper, place it in a centrifuge tube, centrifuge at 3000 r / min for 10 min, drain the surface moisture, weigh it, repeat 3 times, and take the average value. The formula for calculating water holding capacity is:

[0069] Where: M—initial sample mass, g; m—sample mass after centrifugation, g.

[0070] 2.1.10 Data Analysis Experimental data were organized using Microsoft Excel 2016, plotted using Origin 2022, and analyzed using SPSS 20.

[0071] 2.2 Results and Discussion 2.2.1 Effect of ultra-high pressure treatment on total bacterial count of ready-to-cook sea bass during refrigeration Figure 7 The experimental results showed that the total bacterial count in all treatment groups increased with prolonged refrigeration time. The control group (CK) exhibited the fastest bacterial growth, reaching 7.10 logCFU / g on day 12 of refrigeration, rapidly rising to 7.80 logCFU / g on day 16, and reaching 8.95 logCFU / g on day 20, far exceeding food safety standards. This indicates that the control group samples entered the spoilage stage at the initial stage of refrigeration. Among the experimental groups, the 300 MPa treatment group had a total bacterial count close to 6.50 logCFU / g on day 16 of refrigeration and reached 7.19 logCFU / g on day 20. Although lower than the control group, it had already begun the initial stage of spoilage. The 400 MPa group's total bacterial count decreased to 6.94 logCFU / g on day 20 of refrigeration. The 500 MPa and 600 MPa groups showed better antibacterial effects, with total bacterial counts of 6.45 logCFU / g and 6.36 logCFU / g respectively on day 20 of refrigeration, significantly lower than the other groups. The results show that ultra-high pressure sterilization can significantly inhibit bacterial growth during refrigeration and significantly extend the shelf life of products. The higher the pressure, the more significant the antibacterial effect. The 500 MPa and 600 MPa treatment groups showed the best results, with a shelf life extended by approximately 8 days compared to the control group. This indicates that HPP technology disrupts the cell membranes and key enzymes of microorganisms, effectively inhibiting their growth and reproduction.

[0072] 2.2.2 Effects of Ultra-High Pressure Processing on TVB-N During Cold Storage of Ready-to-Cook Sea Bass Figure 8The experimental results showed that the TVB-N values ​​of different treatment groups gradually increased with prolonged storage time, and the rate of increase differed significantly. The control group (CK) showed the fastest TVB-N accumulation rate throughout the storage period, reaching 38.98 mg / 100 g on day 20, exceeding the spoilage threshold. The 300 MPa and 400 MPa treatment groups showed some inhibitory effect in the early stage (0-8 days), with TVB-N values ​​of 14.88 mg / 100 g and 13.26 mg / 100 g on day 8, respectively, significantly lower than the CK group's 18.35 mg / 100 g. However, with increasing storage time, the inhibitory effect of both groups gradually weakened. By day 20, TVB-N reached 27.52 mg / 100 g and 26.60 mg / 100 g, respectively, showing significant improvement compared to the control group, but the spoilage process was not completely inhibited. The 500 MPa and 600 MPa groups showed strong inhibitory effects during storage, especially the 600 MPa group, which exhibited the lowest TVB-N growth rate, reaching only 23.36 mg / 100 g on day 20, significantly lower than other treatment groups (P<0.05). These results indicate that higher pressure treatment has a more significant inhibitory effect on microbial activity and more effectively delays the spoilage process. In summary, high-pressure treatment can significantly reduce TVB-N accumulation during refrigeration, extending the storage period, and the higher the pressure, the more pronounced the inhibitory effect. Treatments at 300 MPa and 400 MPa slowed the spoilage process of fish meat, while the 600 MPa treatment was the most effective, significantly extending the shelf life of the fish meat.

[0073] 2.2.3 Effect of Ultra-High Pressure Processing on Thiobarbituric Acid Value of Ready-to-Cook Sea Bass During Cold Storage Thiobarbituric acid (TBA) value is an important indicator for evaluating the degree of lipid oxidation in aquatic products. Lipid oxidation degrades fish quality, produces off-flavors, and affects food safety. A TBA value of 1-2 mg MDA / kg or higher indicates spoilage of the fish. Figure 9As can be seen, the TBARS values ​​of different treatment groups gradually increased with the extension of storage time, but the rate of increase varied significantly. The TBARS value of the control group (CK) increased the fastest during storage, reaching 1.481 mg / kg on day 20, which was significantly higher than that of all high-pressure treatment groups (P<0.05), indicating that lipid oxidation was more intense in untreated fish samples during cold storage. The TBARS value of the high-pressure treatment groups increased significantly at a slower rate, and the inhibitory effect increased with increasing treatment pressure. In the early stage of storage (0-8 days), all treatment groups showed significant inhibitory effects on lipid oxidation. The TBARS values ​​of the 300 MPa and 400 MPa treatment groups on day 8 were 0.488 mg / kg and 0.493 mg / kg, respectively, which were significantly lower than that of the control group (0.570 mg / kg) (P<0.05). In the later stage of storage (12-20 days), the 500 MPa and 600 MPa treatment groups showed better effects. On day 20, the TBARS values ​​were 1.081 mg / kg and 1.136 mg / kg, respectively, significantly lower than the control group and also lower than the 300 MPa and 400 MPa treatment groups (P<0.05). The results indicate that high-pressure treatment can significantly delay lipid oxidation in fish samples during refrigeration, effectively reduce TBARS values, and extend storage period, with the 500 MPa treatment showing the best effect. This demonstrates that high-pressure treatment inhibits lipid oxidation and improves the preservation effect of aquatic products.

[0074] 2.2.4 Effect of ultra-high pressure treatment on pH during refrigeration of ready-to-eat sea bass products Figure 10As can be seen, with the extension of storage time, the pH values ​​of the treatment groups under different pressures showed a trend of first decreasing and then increasing. In the early stage of storage (0-4 days), the pH values ​​of all groups decreased significantly. This was due to the accumulation of lactic acid and the formation of acidic substances such as phosphoric acid in the fish meat, leading to a decrease in pH. On day 4, the pH value of the CK group dropped to 6.357, significantly lower than the initial value, indicating that the untreated sample developed significant acidity during storage. The pH decrease in the treatment groups was smaller; the pH value of the 400 MPa treatment group was 6.515, significantly higher than that of the CK group (P<0.05). In the later stage of storage (8-20 days), the pH values ​​of all groups gradually increased, possibly due to the accumulation of alkaline substances (such as ammonia and amine compounds) produced by protein degradation. On day 20, the pH value of the CK group increased to 7.415, significantly higher than that of the ultra-high pressure treatment group. This indicates that ultra-high pressure treatment effectively inhibited microbial growth and fish spoilage, delaying the increase in pH value. Among the treatment groups, the 500 MPa group showed the slowest pH increase, reaching 7.139 on day 20, significantly lower than the control group (CK) and slightly lower than the other high-pressure treatment groups (P<0.05). In conclusion, high-pressure treatment effectively inhibits pH changes during fish storage, delays spoilage, and maintains fish quality. The 500 MPa treatment group showed the best inhibitory effect. This demonstrates that high-pressure treatment can inhibit microbial growth and metabolic activity to improve product preservation.

[0075] 2.2.5 Effect of Ultra-High Pressure Processing on Color Difference of Ready-to-Cook Sea Bass Products During Refrigeration During storage, protein decomposition and fat oxidation typically cause color changes in aquatic products, and various factors, including refrigeration conditions, also play a significant role in these color variations. In this experiment, the changes in L, a, b values ​​and ΔE values ​​of fish samples from different high-pressure treatment (HPP) groups during storage are shown in Table 3, and the specific analysis is as follows: Table 3. Effects of HPP treatment on the color of ready-to-cook sea bass products during refrigeration.

[0076] The values ​​in Table 3 are mean ± standard deviation (n = 3). Different lowercase letters in the same row indicate significant differences (P < 0.05). The L value reflects the brightness of the sample. As can be seen from the table, the L values ​​of all groups of samples decreased with prolonged storage time, and the overall changes were relatively similar, with no significant differences (P < 0.05). Initially, the differences in L values ​​among the treatment groups were small. The L value of the CK group was 57.80 ± 0.29, and the L values ​​of other treatment groups were similar, indicating that high-pressure treatment had a weak effect on initial brightness. The decrease in L values ​​during storage may be mainly related to fatty acid oxidation and protein denaturation. The production of oxidation products and protein cross-linking reactions can cause changes in the surface structure of fish, leading to a decrease in brightness. The decrease in L values ​​of the treatment groups was slightly lower in the later stages of storage, but the overall trend was similar to that of the CK group, indicating that high-pressure treatment had a relatively small effect on brightness changes, and the differences between groups were not significant. The a value reflects the red-green change of the sample. Experimental data show that with prolonged storage time, the a value of each group of samples showed a decreasing trend, and the redness gradually weakened. The initial a value of the CK group was -0.21±0.42, which significantly decreased to -1.39±0.45 on day 20. In the high-pressure treatment groups, the a value decreased relatively slowly in the 300 MPa and 400 MPa groups, while the decrease in the 600 MPa group increased to -1.43±0.22 on day 20. The reduction in redness may be related to the decomposition of red pigment by free radicals caused by lipid oxidation. The results indicate that high-pressure treatment appropriately delayed the loss of red pigment, but higher pressure (600 MPa) caused significant damage to the tissue structure, potentially exacerbating the degradation of red pigment. The b value represents the change in yellow-blue color of the sample. The experimental results show that the b value increased during storage. The b value of the CK group increased from the initial -0.33±0.52 to 0.94±0.37 on day 20, and the b value of the 600 MPa group increased from the initial -0.44±0.46 to 0.93±0.26, showing a similar trend. The b-values ​​of the high-pressure treated groups fluctuated less during storage, especially the 500 MPa group. At the end of storage, the b-value was only 0.87±0.45, indicating that high-pressure treatment effectively inhibited the excessive accumulation of yellow pigment. The increase in b-value may be related to the generation of yellow metabolites during lipid oxidation; high-pressure treatment inhibited the oxidation reaction and delayed the formation of yellow pigment. The ΔE value is used to represent the difference between the sample and its initial color. As can be seen from the table, the ΔE values ​​of each group gradually increased with prolonged storage time, indicating a significant change in sample color. On day 20, the ΔE value of the CK group reached 2.87±0.40, the highest among all groups. Among the high-pressure treated groups, the ΔE values ​​of the 300 MPa and 400 MPa groups showed relatively small increases during storage, at 2.60±0.30 and 2.69±0.46 respectively on day 20. The ΔE value of the 600 MPa group was 2.45±0.36, showing the lowest degree of change.This indicates that high-pressure treatment has a certain effect on delaying color changes. In summary, ultra-high pressure treatment can delay color changes in aquatic products; under high pressure, it can slow down the loss of red pigments and the excessive accumulation of yellow pigments. The impact of high-pressure treatment on color changes is closely related to the treatment pressure, storage time, and degree of fat oxidation. The research results provide a useful reference for optimizing product sterilization processes, showing that ultra-high pressure sterilization technology can effectively maintain the color of fish meat and extend the shelf life of products.

[0077] 2.2.6 Effects of Ultra-High Pressure Processing on the Texture of Ready-to-Cook Sea Bass During Cold Storage Firmness reflects the internal binding force that helps fish maintain its shape and is an important indicator of its texture, closely related to consumers' sensory experience. During processing and storage, the firmness of fish is mainly affected by factors such as muscle tissue tightness, changes in protein structure, and water migration. Studying the effects of ultra-high pressure treatment on fish firmness can explore the role of high pressure in the structure of fish muscle tissue, providing theoretical support for product sensory quality evaluation and preservation technology optimization. Figure 11It can be seen that during storage, the hardness of different pressure treatment groups decreased over time, and the pressure level had a significant impact on the initial value and magnitude of the hardness decrease. After ultra-high pressure treatment, the hardness of the treatment groups was significantly higher than that of the control group (CK), with the hardness of the 600 MPa treatment group reaching 7051.28±29.01 gF. This may be because the high-pressure treatment compacted the fish muscle tissue, significantly increasing its hardness. It is worth noting that the samples had all undergone pickling and deodorization treatment before high-pressure treatment. Salt osmosis may have loosened the muscle fiber structure of the fish meat and partially dissolved the protein, thus leading to a decrease in the base hardness value. After applying ultra-high pressure on this basis, the muscle tissue was further compacted, the gaps between muscle fibers narrowed, and free water was expelled, resulting in an increase in hardness. However, excessive hardness is not necessarily an ideal quality characteristic, as it may make the fish meat too firm and difficult to chew, which may negatively affect consumer acceptance. With the extension of storage time, the hardness of each treatment group gradually decreased, and the degree of decrease was closely related to the pressure level. The 600 MPa treatment group showed the fastest decrease in hardness during the initial storage period, reaching 5671.75 ± 46.75 gF by day 4. This may be related to protein degradation, moisture loss, and muscle tissue relaxation that occur during storage. In summary, high-pressure treatment has a significant impact on hardness, but it is important to note that the choice of pressure level significantly affects the palatability of the final product. High-pressure treatment can indeed compress muscle tissue to increase hardness, but excessive pressure may make the fish too firm, losing its tender texture. For example, the 600 MPa treatment group had the highest hardness value during the initial storage period, and some samples were compressed too tightly, which may increase the burden on consumers when chewing. The 400 MPa and 500 MPa treatment groups, on the other hand, had moderate hardness and showed good hardness retention in the later stages of storage, better meeting the ideal texture requirements of fish products.

[0078] Elasticity is an important indicator of a fish's ability to recover under pressure, directly affecting its texture and the consumer's chewing experience. The elasticity of fish is influenced by the structural integrity of the muscle tissue, the strength of the protein gel network, and the activity of microorganisms and enzymes during storage. Figure 12It can be seen that the elasticity of the fish samples decreased significantly with increasing pressure levels. At 0 days, the control group (CK) had the highest elasticity, approximately 2.17 ± 0.05 mm, while the elasticity of the 300, 400, 500, and 600 MPa treatment groups gradually decreased. The elasticity of the 600 MPa treatment group was only 1.85 ± 0.04 mm, significantly lower than the control group (P < 0.05). This indicates that ultra-high pressure treatment significantly enhances the compaction effect on fish muscle tissue, reducing the recovery ability of the compressed samples. Increased pressure may exacerbate the compression and breakage between muscle fibers, reducing the elasticity of the fish meat. With prolonged storage time, the elasticity of all treatment groups showed a decreasing trend, but the magnitude of the decrease was related to the initial pressure level. At the end of storage, the elasticity value of the high-pressure treatment group was still lower than that of the control group, while the 600 MPa treatment group showed the most significant decrease in elasticity, maintaining only around 1.06 ± 0.06 mm, far lower than the 1.25 ± 0.01 mm of the control group. This indicates that excessively high pressure treatment damages the elastic structure of fish tissue, leading to deterioration of the fish meat texture. This result is consistent with observations during the experiment. In summary, ultra-high pressure treatment improves the firmness of fish meat, but this treatment inevitably damages the muscle tissue, significantly reducing its elasticity and overall texture. Increased pressure levels exacerbate this damage, making the fish meat firmer and less elastic during chewing. This indicates that when applying ultra-high pressure treatment, the pressure level should be carefully selected to balance the trade-off between structural improvement and structural damage. Based on the results of this study, treatment groups of 400 MPa or 500 MPa may be better choices, effectively maintaining the quality stability of fish meat during storage and avoiding texture problems caused by over-compaction.

[0079] 2.2.7 Effect of Ultra-High Pressure Processing on Water Holding Rate of Ready-to-Cook Sea Bass During Cold Storage Water-holding capacity (WHC) refers to the ability of fish muscle tissue to retain internal water when subjected to external mechanical forces. It is an important indicator reflecting the structural integrity of muscle tissue and protein function. The WHC content directly affects the texture, mouthfeel, and yield of fish meat. Factors such as protein denaturation and damage to muscle tissue structure can decrease water-holding capacity, accelerating the deterioration of aquatic product quality. Therefore, studying changes in water-holding capacity during storage is of great significance for evaluating quality changes and preservation effects of aquatic products during storage. Figure 13As can be seen, the water-holding capacity (WHC) of all treatment groups decreased with prolonged storage time, but the degree of decrease varied considerably. The water-holding capacity of the samples treated with 600 MPa pressure decreased the fastest during storage, dropping to 57.4% after 20 days, significantly lower than other groups. This indicates that higher pressure may damage muscle tissue fibers, and protein denaturation and dehydration are more severe during storage. All samples were pickled before ultra-high pressure treatment. The high-salt environment induced partial denaturation and dissolution of myofibrillar proteins, leading to loose muscle tissue, a significant decrease in firmness, and changes in water-holding capacity. This process may be closely related to protein conformational changes and water migration induced by salt ion osmosis. The decrease in water-holding capacity in the control group was relatively smaller, and gradually decreased with increasing pressure. The initial WHC of the high-pressure treated samples was generally lower than that of the control group, and decreased with increasing pressure. For example, the initial WHC of the 300 MPa and 400 MPa treatment groups were 84.8% and 83.9%, respectively, while the initial WHC of the 500 MPa and 600 MPa treatment groups were 82.4% and 80.1%, respectively. This indicates that the compression effect of high-pressure treatment on muscle fibers can cause local damage to the muscle structure and reduce its initial water-holding capacity.

[0080] 2.3 Chapter Summary This experiment demonstrated the significant role of ultra-high pressure sterilization technology in slowing down fish spoilage, extending shelf life, and maintaining physicochemical quality. The results showed that the 500 MPa treatment group exhibited the best overall performance, significantly extending shelf life and effectively balancing shelf life and textural properties. While the 600 MPa treatment group showed good antibacterial and preservation effects, it had a more significant impact on the texture of the fish. In summary, ultra-high pressure sterilization technology provides important technical support for the industrial processing, handling, and storage of ready-to-cook sea bass products, effectively extending their shelf life.

[0081] Experiment 3: Optimization of pickling and seasoning processes and flavor analysis 3.1 Experimental Instruments and Materials The sea bass used in the experiment were 30±1 cm in length and weighed 1.50±0.10 kg; the seasonings and spices were purchased commercially.

[0082] 3.2 Experimental Methods 3.2.1 Sample Preparation (1) Sample pickling Fresh sea bass was cleaned by removing the head, tail, scales, and viscera, and then drained. The muscles on both sides were completely removed along the main bone. The fish fillets were then rinsed and soaked in slightly acidic electrolyzed water. The fillets were removed and drained until there were no water droplets on the surface. They were then marinated in a marinade at 4°C. The marinade consisted of the following ingredients: salt solution, scallions, ginger, cooking wine, Sichuan peppercorns, and rice vinegar. The marinated samples were placed in food-grade sample bags and sealed at 4°C for sensory evaluation and determination of volatile flavor compounds.

[0083] (2) Sauce packet sample Add a suitable amount of oil to a pot, then add 50g of garlic and 50g of onion, and sauté until fragrant. Next, add the sauce packet (water, fermented bean paste, sweet bean sauce, brewed soy sauce, oyster sauce, white sugar, aged vinegar, chicken bouillon, pepper, yeast extract, and disodium 5'-inosinate) and heat and stir-fry. After cooling, place in a food-grade sample bag and seal at 4°C for later use in food preparation.

[0084] (3) Samples of pre-prepared products The prepared sauce packet and marinated fish fillets are mixed and heated in a pot (temperature between 120℃ and 150℃) and simmered for 10 minutes to obtain a pre-prepared product sample. After cooling, the sample is sealed and stored in a food-grade sample bag at 4℃ for subsequent sensory evaluation and determination of volatile flavor compounds.

[0085] 3.2.2 Single-factor experiment on pickling and deodorization process Based on the results of preliminary experiments, sea bass fillets were marinated. Single-factor experiments were conducted to investigate the effects of several factors on the flavor of the fish fillets, including marinating time, liquid-to-marinate ratio, salt concentration, amount of scallions, ginger, cooking wine, and Sichuan peppercorns. Each factor was designed with 5 levels, and each level was repeated 3 times.

[0086] Initial conditions for the single-factor experiment: At 4℃±2℃, the ratio of fish fillets to marinade was 1g:2mL, the marinating time was 120 min, the salt concentration in the marinade was 4%, and the ingredients per fish fillet weight were 4% scallion, ginger, cooking wine, Sichuan peppercorns, and rice vinegar. Based on these conditions, the following factors were successively varied: marinating time (40 min, 80 min, 120 min, 160 min, 200 min); ratio of fish fillets to marinade (1:1, 1:2, 1:3, 1:4, 1:5); salt concentration (2%, 4%, 6%, 8%, 10%); amount of scallion, ginger, and cooking wine added (2%, 4%, 6%, 8%, 10%); amount of Sichuan peppercorns added (1%, 2%, 3%, 4%, 5%); amount of rice vinegar added (1%, 2%, 3%, 4%, 5%). After the first single-factor experiment was completed, the optimal value was selected as the experimental conditions for the next single-factor experiment.

[0087] 3.2.3 Response Surface Experiment of Pickling and Deodorization Process Based on the results of the single-factor experiments, a Central Component Experimental Design was conducted. Marinating time (A), salt concentration (B), amount of scallion, ginger, and cooking wine added (C), and amount of Sichuan peppercorns added (D) were used as independent variables, with sensory rating (R) as the response value. Regression fitting and analysis of variance were performed on the experimental results using Design Expert software. The experimental factor levels for the 4-factor, 5-level response surface methodology are shown in Table 4. Sensory evaluation analysis was used to determine the optimal marinating process.

[0088] Table 4 Response Surface Experiment Factors and Levels

[0089] 3.2.4 Single-factor experiment on sauce packet manufacturing process Based on the results of preliminary experiments, the sauce packets were stir-fried. Single-factor experiments were conducted to investigate the effects of several factors on the flavor of the sauce, including oil temperature, heating time, amount of oil added, amount of broad bean paste added, amount of sweet bean sauce added, and amount of brewed soy sauce added (based on the percentage of fish mass). Five levels were designed for each factor, and each level was repeated three times.

[0090] Initial conditions for the single-factor experiment: Oil temperature of 150℃, heating time of 10 min, oil addition of 6%, 20g of broad bean paste, 20g of sweet bean sauce, and 20g of brewed soy sauce. Based on these conditions, the following factors were successively varied: oil temperature (120℃, 150℃, 180℃, 210℃, 240℃); heating time (4 min, 8 min, 12 min, 16 min, 20 min); oil addition (2%, 4%, 6%, 8%, 10%); broad bean paste addition (1%, 2%, 3%, 4%, 5%); sweet bean sauce addition (1%, 2%, 3%, 4%, 5%); brewed soy sauce addition (0.5%, 1.0%, 1.5%, 2.0%, 2.5%). After each single-factor experiment, the optimal value was selected as the experimental conditions for the next single-factor experiment.

[0091] 3.2.5 Orthogonal Experiment on Sauce Packet Manufacturing Process Based on the results of the single-factor experiments, heating time (A), oil addition (B), and fermented bean paste addition (C) were each set with three levels. An orthogonal experiment was conducted using the L9 (33) orthogonal experimental method to optimize the process parameters of the sauce frying. The experimental factor levels of the orthogonal experimental design are shown in Table 5. The optimal processing technology was determined by sensory evaluation analysis.

[0092] Table 5. Factors and levels of orthogonal experiment

[0093] 3.2.6 Sensory evaluation methods (1) Sensory evaluation of marinated fish fillets Ten participants were selected for sensory evaluation; all were professionally trained and randomly chosen. The odor evaluation method was direct olfaction, where evaluators inhaled the volatile odors. The taste evaluation method was tasting; after the fish slices were steamed at 100℃, the evaluators tasted them directly and evaluated their flavor according to the standards. Specific evaluation indicators and methods are shown in Table 6.

[0094] Table 6 Sensory Quality Evaluation Criteria for Marinated Sea Bass

[0095] (2) Sensory evaluation of sauce seasoning For the sensory evaluation, 10 personnel were selected, all of whom were professionally trained and randomly chosen. The evaluation method was tasting; after the fish fillets were mixed with the sauce packet and cooked, the evaluators tasted them directly and evaluated their flavor and texture according to the standards. Specific evaluation indicators and methods are shown in Table 7.

[0096] Table 7 Sensory Quality Evaluation Criteria for Prepared Sea Bass

[0097] 3.2.7 GC-IMS determination of volatile flavor compounds in samples Accurately weigh 2.0 g of sample into a 20 mL headspace vial. Set the incubation temperature to 60℃, the rotation speed to 500 r / min, and the incubation time to 20 min. Inject the sample using a headspace autosampler with an injection volume of 200 μL. Set the injection needle temperature to 65℃ and use splitless injection mode. GC conditions: Use an MXT-5 column (15 m × 0.53 mm, coating thickness 1 μm), set the column temperature to 60℃, use N2 (purity ≥99.99%) as the carrier gas (see Table 8 for the carrier gas flow rate control program), set the migration tube temperature to 45℃, and the analysis time to 30 min. The carrier gas / drift gas is N2.

[0098] Table 8 Carrier gas velocity control program

[0099] 3.2.8 GC-MS determination of volatile flavor compounds in samples First, after mincing the experimental sample, 2 g of fish meat was placed in a 20 mL headspace vial, and 5 mL of saturated saline solution was quickly added and mixed thoroughly. The vial was then sealed and placed on a magnetic stirrer for heating at 65°C for 20 min. Next, a 100 μm PDMS extraction tip was inserted into the headspace portion of the vial, its position adjusted and fixed, maintaining the temperature at 65°C for 30 min, followed by analysis.

[0100] After extraction, the extraction head was inserted into the injection port of the gas chromatograph, and the injection port temperature was set to 250℃. After analyzing for 20 min, it was removed. The gas chromatographic conditions were as follows: column DB-5MS (30 m × 0.25 mm, 0.25 μm); injection port temperature 250℃; temperature program: initial temperature 35℃ held for 3 min, then increased to 70℃ at a rate of 3℃ / min, held for 1 min, then increased to 200℃ at a rate of 10℃ / min, held for 1 min, and finally increased to 260℃ at a rate of 20℃ / min, held for 5 min; the carrier gas was helium, with a flow rate of 1.0 mL / min, using constant linear velocity, and a split ratio of 5:1.

[0101] The mass spectrometry conditions were set as follows: ion source temperature 200℃; electron energy 70 eV; mass scan range m / z 35-350.

[0102] 3.2.9 Data Processing Methods Microsoft Excel was used to organize the data, SPSS software was used for statistical analysis, Origin and Python were used for data visualization and plotting, and Design Expert software was used for response surface methodology design and data analysis.

[0103] 3.3 Results and Analysis 3.3.1 Results of Single-Factor Experiment on Deodorization during Pickling 3.3.1.1 Effect of pickling time on deodorization: The sensory score reached its highest value of 94.3 points when the pickling time was 120 minutes; while the sensory scores were lower at 40 minutes and 200 minutes, at approximately 82.5 points and 72.4 points, respectively. Appropriate pickling time allows the product to achieve its optimal flavor and texture, while pickling times that are too short or too long are detrimental to improving sensory quality.

[0104] 3.3.1.2 Effect of the liquid-to-material ratio on deodorization: The sensory score was highest at a ratio of 1:1, reaching 93.5 points. As the ratio increased, the sensory score gradually decreased, reaching its lowest at a ratio of 1:5, at 78.2 points. An excessively high ratio may result in uneven seasoning and affect the overall flavor of the product.

[0105] 3.3.1.3 Effect of salt concentration on deodorization effect: The sensory score was highest at a salt concentration of 4%, reaching 89.3 points; the sensory scores were lowest at salt concentrations of 2% and 10%, at 66.3 points and 61.4 points, respectively. Both excessively low and excessively high salt concentrations significantly reduced the sensory score because the seasoning effect of salt was poor or the product was too salty, affecting its taste.

[0106] 3.3.1.4 Effect of the amount of scallion, ginger, and cooking wine added on the deodorizing effect: The sensory score was highest at 4% (91.1 points), while the lowest (65.5 points) was achieved at 10%. Both excessively low and high additions significantly reduced the sensory score, indicating that the flavoring effect of the scallion, ginger, and cooking wine was poor or too concentrated, affecting the product's taste.

[0107] 3.3.1.5 Effect of Sichuan pepper addition on deodorization effect: The sensory score was highest at 3% Sichuan pepper addition, reaching 90.3 points; the sensory scores were lower at 1% and 5% Sichuan pepper addition, at 75.4 points and 64.5 points respectively. Too little or too much Sichuan pepper addition is detrimental to improving sensory quality because insufficient or excessive aroma of Sichuan pepper affects the overall flavor balance.

[0108] 3.3.1.6 Effect of Rice Vinegar Addition on Deodorizing Effect: The sensory score gradually decreased with increasing rice vinegar addition. The highest sensory score (93.5 points) was achieved at 1% rice vinegar addition, while the lowest score (78.2 points) was achieved at 5%. Excessive rice vinegar significantly reduced the sensory score because its acidity masked other flavors at higher concentrations.

[0109] 3.3.2 Response Surface Optimization Experiment of Fish Fillet Marinating and Deodorization Process Based on the results of the single-factor experiment, a response surface optimization experiment with four factors and five levels was designed, with a total of 28 experimental points set up and three repeated experiments conducted to evaluate the experimental error.

[0110] Based on regression analysis of the experimental data using Design-Expert software, the second-order fitting equation of the model was obtained: R=95.75-0.82A+0.4B-1.77C+0.47D-0.13AB-0.23AC+0.99AD+0.19BC+0.22BD-2.01CD-4.72A 2 -2.85B 2 -2.97C 2 -3.41D 2 .

[0111] The statistical results show that the model is highly statistically significant. P<0.01), and the p-value of the lack-of-fit term (0.0517) is greater than 0.05, indicating a high goodness of fit. Furthermore, the model's corrected coefficient of determination R²adj reaches 0.9782, indicating that it can explain 97.82% of the response variable changes; the coefficient of variation CV is 1.03% (less than 5%), indicating good equation stability; and the signal-to-noise ratio is 32.3769 (greater than 4), further verifying the good fit of the equation. Therefore, this regression equation can accurately describe the changing trend of the experimental data. The influence of each factor on the deodorization effect of fish meat was assessed by the F-value, and the order of influence was C (amount of scallion, ginger, and cooking wine added) > A (marinating time) > D (amount of Sichuan pepper added) > B (salt concentration). Further analysis showed that the marinating time, the amount of Sichuan pepper added, the amount of scallion, ginger, and cooking wine added, and their quadratic terms (A², B², C², D²) all had extremely significant effects on the model. P <0.01). In addition, there is a strong interaction between the variables AD (marinating time × amount of Sichuan pepper added) and CD (amount of scallion, ginger and cooking wine added × amount of Sichuan pepper added).

[0112] Using the highest sensory score as the optimization target, the optimal formula for marinating and deodorizing sea bass was determined to be: marinating time 119 minutes, salt concentration 4%, scallion, ginger, cooking wine 3.7%, and Sichuan peppercorns 3%, with a sensory score of 96.2. To verify the feasibility of the model, this combination was repeated three times, with a sensory score of 95.5, close to the predicted result, indicating that the model can effectively optimize the marinating and deodorizing process of the product.

[0113] 3.3.3 Results of Single-Factor Experiment on Seasoning Process of Sauce Packets 3.3.3.1 Effect of oil temperature on sensory scores of sauces: Within the range of 120℃ to 240℃, sensory scores showed a trend of first increasing and then decreasing, with the highest score occurring at 180℃, reaching 89.75±3.90 points. At a moderate oil temperature, the aroma is fully released, and the texture and color of the fish are also well presented, resulting in the best overall flavor.

[0114] 3.3.3.2 Effect of heating time on the sensory score of the sauce: The score gradually increased with the extension of heating time. At 8 minutes, the sensory score reached its highest point, 93.20±3.39 points. Under appropriate heating time, the aroma was fully released, and the texture and color of the fish were well presented, resulting in the best overall flavor.

[0115] 3.3.3.3 Effect of oil addition on sensory scores of sauces: Within the range of 2% to 10%, sensory scores showed a trend of first increasing and then decreasing, with the highest score occurring at approximately 6% oil addition, at 93.20 ± 2.70 points. Appropriate oil addition can enhance aroma release and improve mouthfeel, resulting in the best overall flavor.

[0116] 3.3.3.4 Effect of Doubanjiang Addition Amount on Sensory Score of Sauce: Within the range of 1% to 5%, the sensory score showed a trend of first increasing and then decreasing, with the highest score occurring when the doubanjiang addition amount was 3%, at 93.20±2.70 points. An appropriate amount of doubanjiang can increase the flavor depth, enhance the overall sensory experience, and bring the product to its optimal state in terms of color, aroma, and taste.

[0117] 3.3.3.5 Effect of Sweet Bean Sauce Addition Amount on Sensory Score: Within the range of 1% to 5%, the sensory score showed a trend of first increasing and then decreasing, with the highest score occurring when the sweet bean sauce addition amount was 4%, at 90.20±3.46 points. An appropriate amount of sweet bean sauce can add a moderate sweetness and rich flavor layers to the product, enhancing the overall sensory experience.

[0118] 3.3.3.6 Effect of soy sauce addition on sensory score of sauce: In the range of 0.5% to 2.5%, the sensory score showed a trend of first rising and then falling with the change of soy sauce addition, and reached the highest value of 89.60±2.80 points at about 1.5%. Appropriate amount of soy sauce can add salty and umami flavor to the ingredients and enrich the overall flavor.

[0119] 3.3.4 Orthogonal Experiment on Sauce Production Process Based on single-factor experiments, this study investigated six key process factors of the sauce packet. To further improve experimental efficiency and clarify the influence of key variables, three factors—heating time, oil addition amount, and fermented bean paste addition amount—were subsequently selected for orthogonal experimental design, with three level ranges set up, using an L9 (3... 3 The process was optimized using an orthogonal array. Based on the main effect analysis, the optimal combination was A3B2C2: heating time 10 min, oil addition 6%, and fermented bean paste addition 3%. This combination was not included in the orthogonal scheme. To verify the effectiveness of this formula, three parallel experiments were conducted to ensure its stability and repeatability. The sensory scores obtained from the parallel experiments were 95.80 points, all higher than other combinations in the orthogonal scheme, verifying the superiority of this formula combination.

[0120] Based on the basic formula, orthogonal experiments were used to optimize and determine the seasoning formula and process parameters. The final seasoning process is as follows: heating time 10 minutes, oil 6%, garlic 40%, onion 40%, broad bean paste 3%, sweet bean sauce 4%, brewed soy sauce 1.5%, white sugar 1.5%, oyster sauce 1.5%, aged vinegar 1%, chicken essence 1%, pepper powder 1%, yeast extract and disodium 5'-inosinate 0.1% (calculated as a percentage of fish weight). After weighing the ingredients according to the proportions, oil is added first and heated to a suitable temperature (180℃), then scallions, ginger and other spices are added and sautéed until fragrant. Then, broad bean paste, sweet bean sauce, soy sauce and other seasonings and an appropriate amount of water are added in sequence to dissolve and form a uniform seasoning liquid. Finally, the fish is placed in the seasoning liquid and simmered over low heat for 10 minutes to allow it to fully absorb the flavor of the seasoning liquid.

[0121] 3.3.5 GC-IMS Analysis Results of Volatile Flavor Compounds Before and After Pickling and Processing GC-IMS technology combines gas chromatography and ion mobility spectrometry to provide detailed information about volatile flavor compounds in a sample.

[0122] To analyze the changes in volatile flavor compounds in samples from different treatment groups, qualitative analysis was performed using the GC-IMS database built into the VOCal software. Effective characteristic peaks were selected from the chromatograms of the three sample groups and matched with the GC-IMS database, identifying a total of 44 volatile flavor compounds, including 5 aldehydes, 10 ketones, 5 alcohols, 7 esters, and 4 alkenes. The types and composition of these volatile compounds play a crucial role in the flavor characteristics of food, imparting different sensory properties. Five aldehydes were identified: pentanal, hexanal, heptanal, (E)-2-hexenal, and 2-methyl-2-pentenal. Aldehydes are often closely related to the sweetness, aroma, and odor of food, especially during cooking, where chemical reactions often alter their composition, affecting the final aroma characteristics. Pentanal and hexanal are commonly found in fruity and floral aromas, while (E)-2-hexenal, generated during cooking, is associated with the aroma of fried and baked foods. There are 10 types of ketones, including 2-pentanone, 2-octanone, 2-heptanone, 3-pentanone, 2,3-pentanedione, and 2,3-butanedione. Ketones are widely present in food, especially closely related to the formation of creamy, nutty, fruity, and roasted aromas. For example, 2,3-pentanedione is considered to have creamy and caramel flavors. 2-octanone and 2-heptanone are associated with fruity, blue cheese, and coconut aromas. Ketones have a significant impact during cooking; many react at high temperatures to generate new volatile flavor compounds, enhancing the aroma of food. Five types of alcohols were included in this experiment, such as 1-butanol, 2-hexanol, and 2-methyl-1-pentanol. Alcohols have a significant influence on the aroma of food, usually possessing a sweet odor, and they tend to be highly volatile during cooking. For example, 2-hexanol is considered a fruity and floral aroma compound, frequently found in the aroma components of fruit and vegetable products. Seven ester compounds were detected, including methyl acetate, propyl acetate, and butyl acetate. Esters are among the most common aroma compounds in food, widely found in fruits, flowers, and fermented foods, primarily contributing fruity, sweet, and floral aromas. These substances are typically synthesized during brewing, fermentation, or cooking. Four olefin compounds were detected, including limonene, α-phellandrene, α-isoterpinene, and γ-terpinene. Olefin compounds mainly impart fresh, sweet aromas to food and are commonly found in the aromas of citrus fruits. Three aromatic compounds were detected. Aromatic compounds are often key components of complex food flavors, giving foods unique aromatic odors, especially during ripening and cooking. Three organic acids were detected, including 3-methylbutyric acid, hexanoic acid, and methyl methacrylate. Organic acids can affect the acidity of food and work in conjunction with other flavor compounds to improve the overall flavor of the food. The other class included seven substances, which accounted for a smaller proportion in the study and played a negative or auxiliary role in the formation of specific flavors.

[0123] The flavor fingerprint spectrum obtained after extracting characteristic peaks using the "Gallery plot" plugin in VOCal software is shown below. Figure 16 As shown, the signal intensity representing volatile flavor compounds in the fingerprint spectrum changed significantly, indicating significant differences in the flavor composition of samples from different treatment groups. After pickling and cooking, the content of flavor compounds in the samples was generally higher than that in the control group. This indicates that the types and concentrations of flavor compounds increased during pickling and cooking, with the diversity and concentration changes of flavor compounds being more pronounced in the cooked group samples. The increase in flavor compound content during pickling and cooking may be closely related to factors such as chemical reactions, lipid oxidation, and protein degradation caused by heat treatment. In particular, thermal decomposition, Maillard reaction, and lipid oxidation reactions during cooking can promote the formation of new volatile flavor compounds, significantly increasing the concentration and types of flavor compounds. Enzymatic hydrolysis and the combination of spices during pickling also help to enhance the release of flavor compounds and improve the overall flavor of the samples. This study shows that pickling and cooking treatments can significantly enhance the volatile flavor compounds in sea bass samples, with the most significant changes in the types and concentrations of flavor compounds observed in the cooked group samples. This provides strong data support for flavor optimization and applications in food processing.

[0124] Principal component analysis (PCA) of volatile flavor compounds was performed on three groups of samples (untreated, pickled, and cooked) using the "Dynamic PCA" plugin in VOCal software. The results are as follows: Figure 14 As shown, the cumulative variance contribution rate is 90%, indicating that it covers the vast majority of the odor information of the fish samples. There are significant differences between the CK group and the marinated and cooked groups, while the distributions of the marinated and cooked groups are relatively similar, indicating that their volatile compounds are quite similar. The marinating process has a significant impact on the volatile flavor compounds of the samples, possibly due to the penetration and reaction of spices, salt, and other components during marinating, resulting in significant changes in the sample flavor. The cooking process, based on this, slightly alters the flavor of the samples, producing slight differences in flavor types and content. This may be related to the formation and interaction of volatile compounds at high temperatures during cooking.

[0125] To analyze the contribution of different flavor compounds to the flavor of the samples, OPLS-DA analysis screened 18 characteristic differential flavor compounds based on the criteria of P<0.05 and VIP>1. These included 5 aldehydes, 4 alcohols, and 3 esters. According to the OPLS-DA score curve, the contribution rate on the X-axis (61.1%) was higher than that on the Y-axis (27.4%), indicating that the differences between groups of volatile flavor compounds were greater than the differences within groups. Aldehydes were the most abundant class of volatile flavor compounds detected, mainly including pentanal, hexanal, heptanal, 2-methyl-2-pentenal, and (E)-2-hexenal. Hexanal and (E)-2-hexenal imparted a distinct grassy aroma to the samples, while heptanal had fruity and citrus aromas, giving the product a pleasant fruity flavor. The detected alcohols included 1-butanol, 2-hexanol, 3-octen-1-ol (Z), and 3-hydroxy-2-butanone. 1-Butanol possesses aromas of alcohol and banana, while 2-hexanol exhibits mild floral and fruity notes; these substances may enhance the fruity characteristics of the sample. 3-Octen-1-ol (Z) imparts mushroom and earthy notes to the sample, potentially affecting the overall flavor balance. 3-Hydroxy-2-butanone, on the other hand, has aromas of butter and cream, contributing a smoother mouthfeel. Esters and aromatic compounds typically impart sweet fruity aromas to food; detected esters and aromatic substances include propyl acetate and butylbenzene, which contribute a certain sweet and aromatic character to the sample. Detected olefins such as α-phellandrene, R / S-limonene, and γ-terpinene possess spicy, citrus, and spice aromas, potentially playing a harmonizing role in the overall flavor profile and enhancing flavor complexity. Other key flavor compounds may also influence the overall flavor perception of the final sample, providing important references for subsequent product flavor optimization.

[0126] 3.3.6 GC-MS Analysis Results of Volatile Flavor Compounds Before and After Pickling and Processing Figure 15 The images show the GC-MS total ion chromatograms of three fish samples; where A represents untreated fish, B represents marinated fish, and C represents cooked fish. GC-MS analysis identified 57 flavor compounds, largely consistent with GC-IMS results. Of these, 38 compounds were detected by both methods, 6 by GC-IMS alone, and 13 by GC-MS alone. This difference reflects the complementarity of GC-MS and GC-IMS and their different advantages in detecting volatile flavor compounds. The 38 compounds detected by both GC-MS and GC-IMS encompass a wide range of compounds, including aldehydes (such as pentanal, hexanal, and heptanal), ketones (such as 2-pentanone and 2-heptanone), alcohols (such as 1-butanol and 2-hexanol), and esters (such as methyl acetate and propyl acetate), indicating that these compounds have high concentrations and stability in sea bass samples and can be effectively captured by both techniques.

[0127] GC-IMS rapidly screens highly volatile flavor compounds (such as ketones and alcohols) generated during marinating and cooking, helping to monitor the dynamic impact of processes on flavor in real time; while GC-MS reveals in-depth changes in complex compounds (such as olefins and aromatics), providing strong support for understanding the contribution of flavor addition and thermal reactions to flavor.

[0128] In summary, analysis of the changes in various flavor compounds before and after marinating and cooking reveals that the flavor improvement is achieved through the synergistic effect of deodorization and seasoning intervention. The marinating process, by inhibiting fat oxidation and protein degradation, reduces the accumulation of odor-causing aldehydes and sulfides, creating a "cleaner" flavor base. Meanwhile, olefins and aromatic compounds derived from spices in the seasonings significantly enhance the product's fruity and floral sensory characteristics, enriching the overall flavor structure. Therefore, deodorization plays a fundamental role in flavor optimization, while seasoning plays a dominant role in the final flavor formation. The two complement each other, jointly achieving an overall improvement in the product's flavor.

[0129] 3.4 Chapter Summary This experiment investigated the optimization of marinating, deodorizing, and seasoning processes for sea bass. Response surface methodology was used to determine the optimal marinating formula: marinating time 119 minutes, salt concentration 4%, scallion, ginger, cooking wine 3.7%, and Sichuan peppercorns 3%. Orthogonal experiments were used to optimize the seasoning process, and the final formula significantly improved the sensory score of the product. GC-MS and GC-IMS were used to analyze the changes in key flavor compounds during marinating and cooking. The results showed that marinating and cooking significantly reduced the content of fishy odor compounds such as hexanal, heptanal, and dimethyl trisulfide, while generating aromatic compounds such as limonene and α-terpineol, resulting in a more harmonious and layered flavor in the finished product. This study provides important data support for improving product flavor, market acceptance, and consumer experience.

[0130] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing ready-to-cook sea bass products using slightly acidic water electrolysis combined with ultra-high pressure technology, characterized in that, Includes the following steps: (1) Remove the head, tail, scales, gills and internal organs of the fresh sea bass, cut it in half and remove the backbone. Remove the muscles on both sides along the main bone, clean them and get fish fillets for later use. (2) Using a slightly acidic electrolyzed water generator, add electrolytes to prepare slightly acidic electrolyzed water with a certain effective chlorine concentration; soak the fish fillets in the slightly acidic electrolyzed water for treatment, then take out the fish fillets, drain them until there are no water droplets on the surface, and place them in the marinating solution for marinating; (3) After marinating, drain the fish fillets, wipe off the surface water droplets, place the fish fillets in a container filled with cooling water, and perform ultra-high pressure sterilization. (4) Add oil, garlic and onion to the pot and stir-fry. Then add the sauce, heat and stir-fry, cool, and obtain the sauce packet. Seal and store. (5) To cook, add the sterilized fish fillets and sauce packet to the pot, mix well and heat, simmer to obtain the ready-to-cook sea bass product, and seal and store.

2. The method for preparing ready-to-cook sea bass products using slightly acidic water electrolysis combined with ultra-high pressure technology according to claim 1, characterized in that, The effective chlorine concentration of the slightly acidic electrolyzed water in step (2) is 70-80 mg / L, and the treatment time is 30 min.

3. The method for preparing ready-to-cook sea bass products using slightly acidic water electrolysis combined with ultra-high pressure technology according to claim 1, characterized in that, In step (2), the ratio of fish fillets to marinade is 1g:2mL, the temperature is 4℃, and the time is 119min.

4. The method for preparing ready-to-cook sea bass products using slightly acidic water electrolysis combined with ultra-high pressure technology according to claim 1, characterized in that, The marinade mentioned in step (2) includes the following ingredients: salt solution, scallion and ginger cooking wine, Sichuan peppercorns, and rice vinegar.

5. The method for preparing ready-to-cook sea bass products using slightly acidic water electrolysis combined with ultra-high pressure technology according to claim 4, characterized in that, The salt concentration in the pickling solution is 4%; Based on the weight of the fish fillets, the amount of scallions, ginger, and cooking wine added is 3.7%, the amount of Sichuan peppercorns added is 3%, and the amount of rice vinegar added is 1%.

6. The method for preparing ready-to-cook sea bass products using slightly acidic water electrolysis combined with ultra-high pressure technology according to claim 1, characterized in that, The ultra-high pressure sterilization process in step (3) is performed at a pressure of 500 MPa for 5 minutes.

7. The method for preparing ready-to-cook sea bass products using slightly acidic water electrolysis combined with ultra-high pressure technology according to claim 1, characterized in that, The amount of oil added in step (4) is 6% of the fish fillet mass.

8. The method for preparing ready-to-cook sea bass products using slightly acidic water electrolysis combined with ultra-high pressure technology according to claim 1, characterized in that, The sauce mentioned in step (4) includes the following ingredients: water, broad bean paste, sweet bean sauce, brewed soy sauce, oyster sauce, white sugar, aged vinegar, chicken essence, pepper powder, yeast extract, and disodium 5'-inosinate.

9. The method for preparing ready-to-cook sea bass products using slightly acidic water electrolysis combined with ultra-high pressure technology according to claim 8, characterized in that, Based on the weight of the fish fillets, the amount of fermented soybean paste added is 3%, the amount of sweet bean sauce added is 4%, and the amount of brewed soy sauce added is 1.5%.

10. The method for preparing ready-to-cook sea bass products using slightly acidic water electrolysis combined with ultra-high pressure technology according to claim 1, characterized in that, The heating and frying temperature in step (4) is 150-210℃ and the time is 8 minutes.

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