A green preservation method for triploid rainbow trout

Abstract

This invention provides a method for the cold storage and preservation of triploid rainbow trout, specifically a method combining plant extracts with dielectric barrier discharge low-temperature plasma followed by modified atmosphere packaging. This method belongs to the field of rainbow trout cold storage and preservation technology. The invention involves first treating roasted radish seeds (after degreasing and water extraction) with dielectric barrier discharge low-temperature plasma technology for 1 minute, then soaking the degreased roasted radish seed water extract in a 4°C refrigerator for 10 minutes, and finally using modified atmosphere packaging (90% CO2 + 10% N2) followed by cold storage. First, dielectric barrier discharge rapidly kills microorganisms on the surface of the triploid rainbow trout. Then, the antioxidant and antibacterial functions of polyphenols in radish seeds are utilized to further sterilize and remove strong oxidizing substances generated by plasma treatment. Finally, modified atmosphere packaging isolates oxygen, inhibiting microbial growth and meat cell respiration, maintaining the natural shape, color, and moisture content of the meat. The application of modified atmosphere packaging solves the technical problems of reduced preservation effect caused by meat compression, rapid moisture loss, and accelerated color deterioration during cold storage after low-temperature plasma treatment and plant preservative treatment.

Description

Technical Field

[0001] This invention belongs to the field of rainbow trout cold storage and preservation technology. Specifically, it relates to modified atmosphere packaging, a green cold storage and preservation method for triploid rainbow trout using plant extracts and dielectric barrier discharge low-temperature plasma. Background Technology

[0002] Triploid rainbow trout are polyploid rainbow trout produced based on genetic characteristics and production practices. Compared with ordinary diploid rainbow trout, they have advantages such as faster growth rate, larger size, stronger disease resistance, finer flesh, and shorter breeding cycle. They account for more than 80% of rainbow trout farming and have become one of the most widely farmed freshwater fish species in my country's market in recent years. Due to the characteristics of triploid rainbow trout flesh and its color and texture similar to salmon, it is usually processed into sashimi. Its color and moisture retention have a significant impact on its eating quality. Therefore, it is important to improve its shelf life and maintain good color and appropriate moisture content.

[0003] The dielectric barrier discharge (DBD) low-temperature plasma treatment process generates strong oxidizing substances such as reactive oxygen species and reactive nitrogen species, including ·OH, O3, H2O2, NO·, and ONOO. - This method damages the cell membranes of microorganisms, thereby rapidly reducing their numbers. As a novel green cold sterilization technology, it has advantages such as being environmentally friendly, efficient, and residue-free. It has been widely used in the processing and preservation of aquatic products and can extend their shelf life. However, strong oxidizing substances can also cause lipid oxidation and degradation in aquatic products, leading to a decline in quality characteristics such as whitening.

[0004] Plant extracts possess unparalleled advantages over chemical antioxidants due to their superior antibacterial and antioxidant properties, as well as their natural and green characteristics. Radish seeds (Raphanus sativus L. seeds) are the dried, mature seeds of the radish plant and are considered both food and medicine. Roasted radish seeds have a mild aroma, can be eaten directly, and contain natural antibacterial components.

[0005] Modified atmosphere packaging (MAP) refers to replacing the original air inside the packaging with a mixture of gases in different proportions. By utilizing the barrier and permeability of the packaging materials, the product is kept in a suitable gaseous environment. This isolates the product from external microorganisms, preventing secondary contamination, and inhibits quality deterioration and microbial growth, thereby extending shelf life. High concentrations of CO2 play a crucial role in maintaining the color of meat products; appropriate gas combinations can regulate meat color and reduce moisture loss. Summary of the Invention

[0006] In view of this, the present invention provides a green cold storage preservation method for triploid rainbow trout after modified atmosphere packaging following treatment with stir-fried radish seed extract combined with dielectric barrier discharge low-temperature plasma treatment. This method can solve the technical problem in the prior art where the color and moisture content of triploid rainbow trout meat decreases during cold storage after treatment with low-temperature plasma and plant extracts.

[0007] This invention is achieved as follows: After mechanically pressing and grinding roasted radish seeds to extract oil, an appropriate amount of water is added to the residue for soaking and extraction. The extract is then obtained through vacuum rotary evaporation to obtain a suitable concentration of roasted radish seed aqueous extract. Triploid rainbow trout are gutted and skinned, then cut into uniformly sized pieces and treated in a dielectric barrier discharge device. The sterilized roasted radish seed aqueous extract is then added according to the liquid-to-solid ratio for soaking. The treated triploid rainbow trout are then packaged in sterile plastic boxes, filled with a pre-prepared gas, sealed, and stored in a refrigerated environment, with preservation indicators measured periodically. A unique gas combination maintains the color and moisture content of the meat.

[0008] In the triploid rainbow trout cold storage preservation method, the voltage of the dielectric barrier discharge device is 130kV, the frequency is 80Hz, the electrode spacing is 60mm, and the treatment time is 1 minute. The total number of colonies and the thiobarbituric acid value are determined by measuring different parameter combinations on the 3rd day after treatment.

[0009] In the triploid rainbow trout cold storage preservation method, the plant preservative is the water extract of fried radish seeds after pressing to remove oil, with a concentration of 1g plant dry weight / mL. The liquid-to-material ratio of the plant preservative and the fish pieces is 5:1, and the soaking time is 10min. The total bacterial count and thiobarbituric acid value are determined by measuring the total bacterial count and thiobarbituric acid value on the 3rd day under different parameter combinations.

[0010] In the modified atmosphere preservation method, the gas composition is 90% CO2 + 10% N2, which is determined by measuring the total bacterial count, color parameters and juice loss rate on the 6th day after treatment with different gas combinations.

[0011] In the modified atmosphere packaging method, the packaging box is a polypropylene (PP) plastic box, and the film is made of polyethylene (PE). The packaging is done using an automatic modified atmosphere packaging machine (MTK-580) manufactured by Suzhou Yahe Preservation Technology Co., Ltd. The method was determined by measuring the juice loss rate and color of the fish meat on day 6 using different packaging materials.

[0012] The refrigerated environment temperature is 4°C, and the total bacterial count, volatile basic nitrogen value, and thiobarbituric acid value are measured every 3 days or every 2 days.

[0013] The measurement frequency is determined every 3 days or every 2 days by analyzing the changing trends of preservation indicators at different time points.

[0014] The preservation indicators include total bacterial count, volatile basic nitrogen (TVB-N) and thiobarbituric acid (TBA) values. Storage is stopped when the total bacterial count (TVC) exceeds 6 log CFU / g (first threshold), the volatile basic nitrogen (TVB-N) exceeds 20 mg / 100g (second threshold), or the thiobarbituric acid (TBA) value exceeds 2 mg / kg (third threshold).

[0015] This invention first presses fried radish seeds to remove oil, then uses water extraction to prepare a green plant preservative, with no organic solvents involved throughout the process. The dielectric barrier discharge plasma treatment is short and free of chemical pollution. Modified atmosphere packaging uses a combination of naturally occurring gases in the air, ensuring a pollution-free process. After dielectric barrier discharge plasma treatment, triploid rainbow trout are soaked in the plant preservative and then sealed in a packaging box filled with a specific gas. Modified atmosphere packaging isolates oxygen, while the high concentration of carbon dioxide helps maintain the color of the meat. The PE coating material provides suitable air and water permeability for triploid rainbow trout, reducing moisture loss and maintaining a reasonable moisture content. This invention first treats the fish with dielectric barrier discharge plasma to directly kill microorganisms on the surface of the fish. Then, soaking in the plant preservative neutralizes and removes residual strong oxidizing substances, and the antibacterial activity compensates for unevenness in the plasma treatment area, further achieving comprehensive sterilization. Finally, the treated fish is placed in a modified atmosphere packaging box for refrigeration, protecting its color and moisture content. In summary, this invention extends the shelf life of triploid rainbow trout and improves the quality of the fish meat during storage by combining three technologies: plant preservatives, plasma treatment, and modified atmosphere packaging. Modified atmosphere packaging solves the technical problems of color deterioration and moisture loss in triploid rainbow trout after the first two treatments. Attached Figure Description

[0016] Figure 1 This is a flowchart of the method of the present invention.

[0017] Figure 2 This graph shows the changes in TVC in triploid rainbow trout during storage.

[0018] Figure 3 A graph showing the changes in TVB-N values ​​of triploid rainbow trout during storage.

[0019] Figure 4 This graph shows the changes in TBA values ​​of triploid rainbow trout during storage.

[0020] Figure 5 This graph shows the change in juice loss rate of triploid rainbow trout during storage.

[0021] Figure 6 This graph shows the changes in color parameters of triploid rainbow trout during storage.

[0022] Figure 7 The effect of different modified atmosphere packaging parameters on the taste of electronic tongues

[0023] Figure 8 The Influence of Different Modified Atmosphere Packaging Parameters on the Odor of Electronic Nose Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below.

[0025] like Figure 1 The diagram shows a flowchart of a green cold storage preservation method for triploid rainbow trout, which involves modified atmosphere packaging after treatment with radish seed extract combined with dielectric barrier discharge low-temperature plasma, provided by this invention. The method includes the following steps:

[0026] S01. After removing the internal organs and skin of the triploid rainbow trout, cut it into fish pieces of uniform size. Place the processed triploid rainbow trout pieces in a dielectric barrier discharge device for processing. Set the voltage to 130kV, the frequency to 80Hz, the electrode spacing to 60mm, and the processing time to 1 minute.

[0027] S02. Grind and press the fried radish seeds to ensure that the oil content after pressing does not exceed 1% of the total radish seed content. Add distilled water at a material-to-liquid ratio of 1:10, soak for 10 minutes, then boil for 10 minutes. Filter the solution and concentrate the filtrate to 1 g / mL by rotary evaporation. After autoclaving and cooling to room temperature, obtain the plant preservative. Add the plasma-treated triploid rainbow trout to the plant preservative at a liquid-to-material ratio of 5:1 and soak for 10 minutes.

[0028] S03. After soaking the triploid rainbow trout in the plant preservative, absorb the moisture and place it in a PP (polypropylene) plastic box three times its volume. Fill the remaining space with 90% CO2 + 10% N2 and seal the box opening with a PE (polyethylene) film.

[0029] S04. Store the packaging box at 4°C. Measure the total bacterial count, volatile basic nitrogen, and thiobarbituric acid every 3 days. Stop storage when the total bacterial count exceeds the first threshold, the volatile basic nitrogen exceeds the second threshold, or the thiobarbituric acid exceeds the third threshold.

[0030] like Figure 2 Total bacterial count experiments showed that DBD primarily reduced the initial bacterial count, but its antibacterial effect weakened over time; while radish seed, as a natural antibacterial agent, provided sustained inhibition throughout the storage period. The combined use of radish seed and DBD enhanced the antibacterial effect. The optimal treatment group was radish seed + DBD + 90% CO2 + 10% N2, remaining below the first threshold until day 12, and only slightly exceeding it on day 15. This means that, based on TVC results, its shelf life can be extended to at least 12-15 days. Figure 3The results of volatile basic nitrogen determination showed that under 90% CO2 + 10% N2 conditions, the TVB-N value of radish seed + DBD remained at 13.77 mg / 100g on day 15, far below the second threshold. From the perspective of TVB-N, its shelf life exceeds 15 days. Figure 4 The results of the thiobarbituric acid value determination showed that the combined treatment of radish seed + DBD + (90% CO2 + 10% N2) showed the best effect in controlling lipid oxidation. Under this combination, the TBARS value was 0.81 mg / kg after 15 days of storage, which was far below the third threshold, and the shelf life was extended to more than 15 days.

[0031] Juice loss rate is also an important indicator for evaluating changes in fish quality, directly affecting the product's weight, juiciness, texture, and consumer acceptance. For example... Figure 5 The combined treatment of radish seed and DBD showed the lowest juice loss rate across all gas conditions and time points, demonstrating strong water retention capacity. This may be because certain components in the radish seed extract help stabilize protein structure or indirectly protect muscle tissue through their antibacterial effects. DBD treatment also showed some water retention effect, possibly due to its slight alteration of cell structure or inactivation of enzymes, but the effect was not as long-lasting as radish seed. The 90% CO2 + 10% N2 group showed slightly lower juice loss than other controlled atmosphere groups. This may be because the anaerobic environment slows down the damage to muscle tissue by microorganisms and enzymes, thus better maintaining the integrity of cell structure. The combined treatment of radish seed + DBD + 90% CO2 + 10% N2 showed the best results, maximizing the water-holding capacity of rainbow trout.

[0032] In addition, the color of fish meat is a major indicator of its quality, as it forms the consumer's first impression and determines their acceptance level. A brighter appearance of fish meat is usually related to changes in the muscle tissue's ability to scatter light, which may stem from protein denaturation, juice loss, or the formation of surface microbial colonies. For example... Figure 6 Radish seed + DBD combined treatment is the most effective way to suppress the increase in brightness and maintain a low L in most cases. * Value. a * The myoglobin value is a key indicator of the bright red color of meat and fish. A decrease in the myoglobin value usually means that myoglobin has been oxidized, and the color changes from bright red to brown, which is an important visual signal of deterioration in quality. * The value is a color index that measures the yellow aspect of a sample. In fish storage, b... * An increase in the value is usually associated with the accumulation of lipid oxidation products, Maillard reactions, or the generation of certain microbial metabolites, and is another important signal of quality deterioration. *The color temperature generally increases with prolonged storage time, indicating that rainbow trout gradually yellows during storage. An anaerobic environment of 90% CO2 + 10% N2 has proven to be the optimal environment for maintaining color. Anaerobic conditions fundamentally prevent the oxidation of myoglobin and fats, which is crucial for maintaining color. * Values ​​and control b * The values ​​are all crucial. In an oxygen-containing environment, the b values ​​for all treatment groups are... * The values ​​(yellowness) were all higher, which directly proves that O2 promotes the oxidation reaction that causes yellowing. The combined treatment of radish seeds + DBD + 90% CO2 + 10% N2 can most effectively maintain the color of fish meat that is closest to its fresh state, that is, prevent excessive brightening, maintain bright red, and inhibit abnormal yellowing.

[0033] This method achieves multiple objectives—antibacterial activity, reduced juice loss, and preservation of fish color—by optimizing the processing sequence and parameter control. First, surface sterilization is performed using dielectric barrier discharge treatment to rapidly eliminate microorganisms on the fish surface. Next, the fish is immersed in a plant-based preservative, which, upon plasma treatment, immediately forms an antioxidant protective layer, neutralizing residual strong oxidizing substances, preventing excessive oxidation of lipids and proteins, and further achieving comprehensive sterilization of the natural plant components. Finally, modified atmosphere packaging further protects the original color of the fish and reduces juice loss. The results show that the synergistic effect of these three technologies significantly extends the cold storage shelf life of triploid rainbow trout and delays quality deterioration, providing technical support for high-quality storage of aquatic products.

[0034] The specific implementation methods of the above steps are described in detail below.

[0035] The voltage (130kV), frequency (80Hz), electrode spacing (60mm), and treatment time (1 minute) of the dielectric barrier discharge device in step S01 were determined through the following experiments. Triploid rainbow trout were treated with voltages of 70kV, 100kV, 130kV, and 150kV, frequencies of 60Hz, 80Hz, and 100Hz, electrode spacings of 60mm, 80mm, and 100mm, and treatment times of 0.5 minutes, 1 minute, and 2 minutes, respectively. The total bacterial count and thiobarbituric acid value were measured on the third day after treatment. Experimental data show that when treated for 1 minute at a voltage of 70kV, a frequency of 60Hz, and a spacing of 80mm, the total bacterial count was 4.15 logCFU / g and the thiobarbituric acid value was 1.21 mg / kg. At a voltage of 100kV, a frequency of 80Hz, and a spacing of 80mm, the total bacterial count was 4.06 logCFU / g and the thiobarbituric acid value was 1.27 mg / kg. At a voltage of 130kV, a frequency of 100Hz, and a spacing of 80mm, the total bacterial count was 3.98 logCFU / g and the thiobarbituric acid value was 1.32 mg / kg. Local overheating occurred at a voltage of 70kV, a frequency of 80Hz, and a spacing of 60mm. At a spacing of 100mm, the discharge efficiency decreased, and the total bacterial count was 4.12 logCFU / g. When treated for 1 minute at a voltage of 130kV, a frequency of 80Hz, and a plate spacing of 60mm, the total bacterial count was 3.75 logCFU / g and the thiobarbituric acid value was 1.37 mg / kg. After 2 minutes of treatment, the total bacterial count was 3.45 logCFU / g and the thiobarbituric acid value was 1.45 mg / kg. After 0.5 minutes of treatment, the total bacterial count was 3.95 logCFU / g and the thiobarbituric acid value was 1.24 mg / kg. Considering both the antibacterial effect and lipid oxidation control, the optimal parameter combination was 130kV, 80Hz, 60mm plate spacing, and 1 minute treatment time.

[0036] In step S02, the fried radish seeds need to be de-oiled before water extraction to improve their activity. This is based on the following experimental results: Equal amounts of fried radish seeds were weighed and extracted for oil and protein, respectively. Equal amounts of fried radish seeds and those after oil extraction were then subjected to water extraction. The oil, protein, fried radish seed water extract, and de-oiled radish seed water extract were prepared into equal volumes of solution. All samples were autoclaved. Fish meat was soaked for 10 minutes in equal volumes of oil, protein, and radish seed water extract and de-oiled radish seed water extract, respectively. Distilled water was used as a control. The samples were stored at 4℃. On the third day, TVC, TVB-N, and TBA values ​​were measured. The total bacterial count was 3.67 log CFU / g in the CK group, 2.99 log CFU / g in the oil group, 3.61 log CFU / g in the protein group, and 2.93 log CFU / g in the water extract. The concentrations of the protein and the oil-free aqueous extract were log CFU / g and 2.56 log CFU / g, respectively. The TVB-N values ​​were 4.1 mg / 100g for the CK group, 3.8 mg / 100g for the aqueous extract, 8.53 mg / 100g for the oil, 17.87 mg / 100g for the protein group, and 5.03 mg / 100g for the oil-free aqueous extract. The TBA values ​​were 1.38 mg / kg for the CK group, 0.91 mg / kg for the oil, 0.61 mg / kg for the protein, 0.41 mg / kg for the aqueous extract, and 0.25 mg / kg for the oil-free aqueous extract. On day 12, the total bacterial count was 7.31 log CFU / g in the CK group, 6.99 log CFU / g in the oil group, 6.8 log CFU / g in the protein group, 6.2 log CFU / g in the water extract, and 6.02 log CFU / g in the defatted water extract. The TVB-N values ​​were 17.03 mg / 100g in the CK group, 13.3 mg / 100g in the water extract, 17.73 mg / 100g in the oil group, 27.53 mg / 100g in the protein group, and 12.37 mg / 100g in the defatted water extract. The TBA values ​​were 1.38 mg / kg in the CK group, 0.91 mg / kg in the oil group, 0.61 mg / kg in the protein group, 0.41 mg / kg in the water extract, and 0.25 mg / kg in the defatted water extract. Experimental results showed that radish seed oil and protein had poor antibacterial, protein and lipid oxidation inhibition activities. The overall effect of the de-oiled radish seed aqueous extract was better than that of the radish seed aqueous extract. Considering that the pungent odor of radish seeds mostly comes from oil, the de-oiled radish seed aqueous extract was selected.

[0037] In step S02, the concentration of the stir-fried radish seed water extract was 1 g / mL, the liquid-to-solid ratio of the plant preservative and the fish pieces was 5:1, and the treatment time was 10 min. This was determined through the following experiments: The concentration of the plant preservative was set to 0.5 g / mL, 1 g / mL, and 2 g / mL; the liquid-to-solid ratio was set to 3:1, 5:1, and 7:1; and the treatment time was set to 5 min, 10 min, 20 min, and 30 min. The total bacterial count and thiobarbituric acid value were measured on the third day under different parameter combinations. When the liquid-to-solid ratio was 5:1 and the treatment time was 10 minutes, the bacterial count of the fish on day 3 was 3.61 log CFU / g and the thiobarbituric acid value was 0.35 mg / kg when the concentration of the plant preservative was 0.5 g / mL; when the concentration of the plant preservative was 1 g / mL, the bacterial count on day 3 was 3.41 log CFU / g and the thiobarbituric acid value was 0.29 mg / kg; and when the concentration of the plant preservative was 2 g / mL, the bacterial count on day 3 was 3.39 log CFU / g and the thiobarbituric acid value was 0.28 mg / kg. Considering economic factors, a plant preservative concentration of 1 g / mL was selected to treat triploid rainbow trout. The experiment continued, with the concentration of the stir-fried radish seed water extract fixed at 1 g / mL and the treatment time at 10 min. When the liquid-to-solid ratio was 3:1, some areas of the fish pieces were not completely submerged, resulting in uneven treatment and a total bacterial count of 4.58 log CFU / g. When the liquid-to-solid ratio was 5:1, the fish pieces were completely submerged and treated evenly, with a total bacterial count of 3.42 log CFU / g and a water absorption rate of 6.2%. When the liquid-to-solid ratio was 7:1, the total bacterial count was 3.40 log CFU / g and the water absorption rate was 6.5%. Considering the uniformity of treatment and the amount of solution used, a liquid-to-solid ratio of 5:1 was determined to be the optimal parameter, as it ensured complete submersion of the fish pieces while avoiding excessive waste of solution. The experiment continued, with the concentration of the stir-fried radish seed water extract fixed at 1 g / mL, and the liquid-to-material ratio of plant preservative to fish pieces at 5:1. When the soaking time was set to 5 min, the bacterial count on the third day was 3.57 log CFU / g, and the thiobarbituric acid value was 0.31 mg / kg; when the soaking time was 10 min, the bacterial count on the third day was 3.42 log CFU / g, and the thiobarbituric acid value was 0.27 mg / kg; when the soaking time was 20 min, the bacterial count on the third day was 3.41 log CFU / g, and the thiobarbituric acid value was 0.28 mg / kg; when the soaking time was 30 min, the fish meat absorbed too much water, and the texture became significantly softer, with a bacterial count of 3.42 log CFU / g and a thiobarbituric acid value of 0.26 mg / kg on the third day. The results showed that soaking for 10 min was sufficient to maintain the bacterial count at a certain level, and extending the soaking time only worsened the texture of the fish meat.

[0038] In step S03, the gas composition of the modified atmosphere packaging was 90% CO2 + 10% N2, determined through the following experiments. Gas combinations of 90% CO2 + 10% N2, 60% CO2 + 30% N2 + 10% O2, and 90% CO2 + 10% O2 were selected, and the total bacterial count, color parameters, and juice loss rate were measured on day 6 after treatment with different gas combinations. When the gas combination was 90% CO2 + 10% N2, the total bacterial count on day 6 was 3.85 logCFU / g, and the color parameter L... * The value is 69.67, a * The value is 27.51, b * The value was 37.53, and the juice loss rate was 1.60%; when the gas combination was 60% CO2 + 30% N2 + 10% O2, the total colony count on day 6 was 4.46 log CFU / g, and the color parameter L... * The value is 71.98, a * The value is 26.32, b * The value was 38.39, and the juice loss rate was 1.83%; when the gas combination was 90% CO2 + 10% O2, the total colony count on day 6 was 4.37 log CFU / g, and the color parameter L... * The value is 72.63, a * The value is 25.27, b * The value was 38.43, and the juice loss rate was 2.17%. In summary, the 90% CO2 + 10% N2 gas combination had the fewest colony counts, the lowest juice loss rate, lower fish meat brightness, higher redness, and lower yellowness, and the best overall performance. Therefore, 90% CO2 + 10% N2 was selected as the filler gas.

[0039] In step S03, the modified atmosphere packaging box is generally made of PP (polypropylene), and the laminating material is determined through the following experiments. Materials PE (polyethylene), PP (polypropylene), and PS (polystyrene) were selected, and the compressive strength, juice loss rate, and color of different materials were measured on day 6 after sealing. When the laminating material was PS, the juice loss rate on day 6 was 2.17%, and the color parameter L... * The value is 74.28, a * The value is 25.36, b * The value is 38.62; when the material is PE, the juice loss rate on day 6 is 1.60%, and the color parameter L... * The value is 67.67, a * The value is 27.51, b * The value is 37.53; when the material is PP, the juice loss rate on day 6 is 1.83%, and the color parameter L... * The value is 72.43, a * The value is 25.79, b *The value was 37.63. This may be due to the high permeability of PS, resulting in a high juice loss rate. PP's permeability and moisture permeability are about half that of PE, leading to excessive water droplets inside the packaging box, which affects the quality of the fish. Based on the above experiments, and considering that PE has moderate tensile strength, PE was chosen as the coating material.

[0040] In step S03, the volume ratio of the modified atmosphere packaging box to the fish meat volume was 3:1, which was determined through the following experiment. The volume ratios of the packaging box to the fish meat volume were selected as 1:1, 3:1, and 5:1, and the juice loss rate and color were determined on the 6th day after treatment. When the volume ratio was 1:1, the proportion of fish meat was higher, and the gas volume was lower; the juice loss rate on the 6th day was 1.77%, and the color parameter L... * The value is 75.84, a * The value is 20.40, b * The value was 38.53; when the volume ratio was 3:1, the juice loss rate on day 6 was 1.82%, and the color parameter L... * The value is 75.52, a * The value is 23.67, b * The value was 38.46; when the volume ratio was 5:1, the juice loss rate on day 6 was 1.85%, and the color parameter L... * The value is 75.46, a * The value is 23.69, b * The value was 38.57. The results indicate that the more gas used in modified atmosphere packaging, the better the color parameters, but the higher the juice loss rate. Based on the above experimental results, and considering that packaging space should not be wasted excessively, a packaging box volume to fish volume ratio of 3:1 was chosen.

[0041] In step S04, the first threshold is 6 log CFU / g. A value exceeding 6 log CFU / g indicates severe microbial contamination, rendering the product unsuitable for consumption. The second threshold, derived from GB2733-2015 National Food Safety Standard for Fresh and Frozen Freshwater Aquatic Products (Fresh and Frozen Animal-Derived Aquatic Products), indicates that a volatile basic nitrogen value not exceeding 20 mg / 100g signifies compliance with national standards. The national standard GB / T 35252-2017 Determination of 2-Thiobarbituric Acid Value in Animal and Vegetable Oils—Direct Method, provides a standardized method for detecting the third threshold. Generally, a TBA value of 2 mg / kg is considered an important warning value for flavor deterioration, indicating detectable lipid oxidation in the meat, but not yet reaching a level of severe spoilage.

[0042] The frequency of measuring preservation indicators every 3 days in step S04 was determined through the following experiment. Triploid rainbow trout samples that had undergone complete treatment were refrigerated at 4°C, and the total bacterial count, volatile basic nitrogen, and thiobarbituric acid values ​​were measured on days 0, 3, 6, 9, 12, and 15. Experimental data showed that the total bacterial count increased little from 2.50 logCFU / g to 3.43 logCFU / g from days 0 to 3; it also slowly increased to 3.85 logCFU / g from days 3 to 6; it increased to 4.16 logCFU / g from days 6 to 9; it rapidly increased to 5.23 logCFU / g from days 9 to 12; and it increased to 6.53 logCFU / g from days 12 to 15. The volatile basic nitrogen value increased slowly in the first 3 days, from 2.80 mg / 100g to 5.13 mg / 100g; it also increased slowly to 7.23 mg / 100g from days 3 to 6; it rose to 10.73 mg / 100g from days 6 to 9; it rose to 13.30 mg / 100g from days 9 to 12; and it rose steadily to 13.77 mg / 100g from days 12 to 15. The thiobarbituric acid value increased evenly throughout the storage period: from 0 to 3 days, it increased from 0.18 mg / kg to 0.32 mg / kg; it also increased slowly to 0.375 mg / kg from days 3 to 6; it rose to 0.623 mg / kg from days 6 to 9; it rose to 0.720 mg / kg from days 9 to 12; and it rose steadily to 0.806 mg / kg from days 12 to 15. Analysis of the experimental data revealed that measuring every 3 days not only allows for timely monitoring of quality changes but also avoids sample consumption and operational costs associated with frequent measurements. Therefore, the measurement frequency was determined to be every 3 days.

[0043] The dielectric barrier discharge treatment in step S01 is a method of generating non-equilibrium plasma by isolating electrodes with an insulating dielectric layer and applying high-frequency, high-voltage alternating current to ionize the gas. The hydroxyl radicals, hydrogen peroxide, reactive oxygen species, and reactive nitrogen species generated during the discharge process attack the nucleic acids and proteins of microorganisms, causing them to denature and become inactive, thus achieving a sterilization effect. Smaller electrode spacing results in better performance; excessive spacing reduces discharge efficiency. A treatment time of one minute represents a balance between antibacterial effect and avoiding excessive oxidation; longer treatment times accelerate the oxidative degradation of polyunsaturated fatty acids in triploid rainbow trout.

[0044] Step S02 employs a sequential treatment process: first, dielectric barrier discharge treatment, followed by immersion in a plant-based preservative. This utilizes the fluidity and antibacterial / antioxidant activity of the plant-based preservative to overcome the uneven treatment caused by the irregular surface of the sample when directly treated with dielectric barrier discharge. During immersion, the polyphenolic compounds in the plant-based preservative penetrate into the fish tissue, forming an antioxidant protective layer and providing antibacterial properties. A liquid-to-material ratio of 5:1 ensures the fish pieces are completely submerged. Insufficient immersion time affects the penetration of active substances, while excessive immersion time causes the fish to absorb water and swell, affecting its texture.

[0045] In step S03, the gases are introduced in proportion by a specialized modified atmosphere packaging machine. Both CO2 and N2 are inert gases. CO2 inhibits the growth of microorganisms and suppresses the respiration of meat cells, thus extending shelf life. N2 maintains the balance in the packaging container by preventing collapse caused by the consumption of carbon dioxide, and also isolates oxygen to prevent the oxidation of lipids and proteins.

[0046] The total bacterial count in step S04 reflects the degree of microbial contamination, while the volatile basic nitrogen value reflects the degree of protein degradation. During refrigeration, the endogenous enzymes and microorganisms in triploid rainbow trout cause protein degradation into alkaline nitrogenous substances such as ammonia and amines, and the volatile basic nitrogen value increases with prolonged storage time. A total bacterial count exceeding the first threshold indicates that the product is severely contaminated with microorganisms and is no longer suitable for consumption, while a volatile basic nitrogen value exceeding the second threshold indicates that a large amount of protein has decomposed. A thiobarbituric acid value exceeding the third threshold indicates that fat spoilage is already severe. Measure preservation indicators every 3 days to promptly monitor the quality changes of triploid rainbow trout. A refrigeration temperature of 4℃ inhibits microbial growth and enzyme activity, extending shelf life.

[0047] Specifically, the principle of this invention is as follows: Low-temperature plasma treatment sterilizes microorganisms by generating hydroxyl radicals, hydrogen peroxide, reactive oxygen species, and reactive nitrogen species that attack their nucleic acids and proteins. However, these strong oxidizing substances simultaneously attack the polyunsaturated fatty acids in triploid rainbow trout, triggering lipid peroxidation and generating oxidation products such as malondialdehyde, leading to increased thiobarbituric acid levels and off-flavors. A strategy of immediately soaking the radish seeds in a plant preservative solution after plasma treatment is employed. The sulforaphane in the stir-fried radish seeds has a destructive effect on microbial cell membranes, enhancing the antibacterial effect. The antioxidant properties of polyphenols neutralize the peroxidation reaction generated by the low-temperature plasma. Degreasing treatment makes the radish seeds more refreshing to use, with higher antioxidant and antibacterial activity. A 10-minute soaking time allows the active ingredients to fully penetrate the fish meat tissue. A 1-minute dielectric barrier discharge treatment balances the antibacterial effect with the avoidance of excessive oxidation. Modified atmosphere packaging is then used, which uses a suitable gas composition to keep the fish meat in a sealed, shaped space, maintaining its natural shape, preventing it from being squeezed or oxidized, and extending its shelf life. It also helps to retain the moisture and color of the fish meat. 90% CO2 + 10% N2 can better reduce oxidation and inhibit the respiration of meat cells and the growth of microorganisms.

[0048] To better understand and implement this invention, the following is an embodiment 1 of a specific application scenario: Embodiment

[0049] In optimizing the cold storage and preservation technology for triploid rainbow trout, a technical team addressed the problems of short shelf life and rapid quality deterioration associated with traditional preservation methods by applying the preservation technology of this invention. The team purchased 15 kg of fresh triploid rainbow trout from a breeding farm, with an average weight of 2.5 kg. After transporting the triploid rainbow trout to the processing workshop, the internal organs and skin were immediately removed on a sterile operating table, and the trout were cut into pieces 80 mm long, 60 mm wide, and 12-13 mm thick, yielding approximately 180 fish piece samples.

[0050] The technical team first prepared the plant preservative according to the method of this invention. 3 kg of roasted radish seeds were weighed, and the oil content was reduced to less than 1% of the total weight using mechanical pressing. 1 kg of the de-oiled roasted radish seeds were weighed, soaked in 10 L of distilled water for 10 minutes, boiled for 10 minutes, and filtered through four layers of gauze to remove solid residue. The filtrate was transferred to a rotary evaporator, and the water bath temperature was set to 60℃ and the vacuum degree to 0.10 MPa. After rotary evaporation and concentration for 40 minutes, approximately 1000 mL of concentrated solution was obtained. The concentrated solution was diluted to a 1000 mL volumetric flask to obtain a 1 g / mL de-oiled radish seed (radish seed) preservative. The preservative was transferred to an autoclave and sterilized at 121℃ and 0.1 MPa for 20 minutes. After sterilization, it was cooled to room temperature for later use.

[0051] The technical team randomly divided 120 triploid rainbow trout pieces into 12 groups of 15 pieces each. First, they used DBD (Dielectric Barrier Discharge) treatment, placing the fish pieces in a dielectric barrier discharge device. The samples were arranged in a single-layer configuration (layer thickness 12.22±0.84mm) in a sealed polypropylene box (outer diameter 215(L)×125(W)×40(H)mm). Then, the box containing the rainbow trout samples was placed at the center of a quartz plate above a grounding electrode. The distance between the box surface and the upper electrode was 20mm to ensure uniform distance between the fish piece surface and the upper electrode plate. The voltage was set to 130KV, the frequency 80Hz, the electrode spacing 60mm, and the dielectric barrier discharge treatment time to 1 minute. Uniform discharge was observed during the treatment, with no localized overheating or sparking. Subsequently, a plant-based preservative was immediately added at a liquid-to-material ratio of 5:1 (5000mL of soaking solution per kg of fish pieces) for 10 minutes. After soaking, the fish pieces were removed and drained of surface liquid for approximately 2 minutes. Then, 7-8 pieces of fish per box were packed into PP (polypropylene) packaging boxes, each measuring 22*13*4cm. After the fish were placed in, the fish occupied approximately 1 / 3 of the box space. Next, the boxes were placed on a modified atmosphere packaging machine (model: MTK-580) from Suzhou Yahe Fresh Preservation Technology Co., Ltd., which then filled the boxes with gases of 60% CO2 + 30% N2 + 10% O2, 10% O2 + 90% CO2, and 10% N2 + 90% CO2 respectively. The boxes were then wrapped with PE film and stored in a 4℃ refrigerator. The specific processing plan is shown in Table 1.

[0052] Table 1 Treatment schemes for different treatment groups

[0053]

[0054]

[0055] The technical team developed a detailed quality monitoring plan, taking samples on days 0, 3, 6, 9, 12, and 15 of storage to determine the total bacterial count, volatile basic nitrogen, and thiobarbituric acid levels. Figure 2 As shown, the total bacterial count was determined using the plate count method. 10g of fish meat sample was added to 90mL of sterile 0.85% saline to make a homogenate. After serial dilution with 0.85% saline, 0.1mL of the appropriate dilution was spread on plate count agar medium and incubated at 37±1℃ for 48h before calculating the total bacterial count (TVC) of rainbow trout.

[0056] like Figure 3As shown, the volatile basic nitrogen value was determined using the micro-diffusion method. 10g of fish sample was extracted with 75mL of water for 30 minutes. After filtration, 1mL of the extract was placed in the outer chamber of a diffusion dish. Boric acid absorbent was added to the inner chamber, and saturated potassium carbonate solution was added to the outer chamber. The dish was then sealed and diffused for 2 hours. The volatile basic nitrogen value was calculated by titration with a standard hydrochloric acid solution. The thiobarbituric acid value was determined using spectrophotometry. 10g of fish sample was extracted with trichloroacetic acid solution and filtered. After the filtrate reacted with thiobarbituric acid reagent, the absorbance was measured at 532nm. The thiobarbituric acid value was calculated based on the standard curve.

[0057] Depend on Figure 2 It is evident that the TVC values ​​of each group gradually increased with increasing storage time. Under a controlled atmosphere environment of 60% CO2 + 30% N2 + 10% O2, the initial TVC value of the CK group was 3.10 logCFU / g, while those of the DRS, DBD, and DRS+DBD groups were 2.71 logCFU / g, 3.03 logCFU / g, and 2.50 logCFU / g, respectively. The CK group showed a rapid increase, reaching 8.55 logCFU / g by day 15, indicating the fastest microbial proliferation rate. Among them, the TVC of the DRS group on day 15 was 7.13 logCFU / g, and that of the DBD group was 8.19 logCFU / g. The DRS+DBD group showed the best inhibitory effect, with its TVC consistently significantly lower than other groups, reaching only 6.77 logCFU / g on day 15, significantly delaying microbial proliferation. Under a high CO2, low-oxygen controlled environment of 90% CO2 + 10% N2, the overall TVC increase rate of each group was lower than that of the 60% CO2 + 30% N2 + 10% O2 group. The TVC of the CK group on day 15 was 8.10 log CFU / g, indicating that high concentrations of CO2 had a certain inhibitory effect on microbial proliferation. Both the DRS and DBD groups significantly inhibited the increase of TVC, with the TVC of the DRS group on day 15 being 6.75 log CFU / g and the DBD group being 7.75 log CFU / g. The DRS + DBD synergistic treatment group showed the best effect, with a TVC of 6.53 log CFU / g on day 15, which was significantly lower than that of other treatment groups, and the preservation effect was stable. In a hyperoxic environment of 90% CO2 + 10% O2, the hyperoxic conditions weakened the antibacterial effect of CO2 to some extent. The CK group showed the fastest increase in TVC, reaching 8.88 logCFU / g on day 15, significantly accelerating the putrefaction process. The DRS group effectively offset the negative effects of the hyperoxic environment, with a TVC of 7.04 logCFU / g on day 15, significantly lower than the CK group. The DBD group showed a weakening inhibitory effect in the later stages, with a TVC of 8.24 logCFU / g on day 15. The DRS+DBD synergistic treatment group still showed a significant antibacterial advantage, with a TVC of 6.76 logCFU / g on day 15, effectively delaying the proliferation of microorganisms under hyperoxic conditions.

[0058] Depend on Figure 3It is evident that under a controlled atmosphere environment of 60% CO2 + 30% N2 + 10% O2, the initial TVB-N value in the CK group was 4.20 mg / 100g, while those in the DRS, DBD, and DRS+DBD groups were 2.57 mg / 100g, 3.03 mg / 100g, and 2.80 mg / 100g, respectively. The CK group showed the fastest increase, reaching 20.27 mg / 100g TVB-N by day 15, exceeding the spoilage limit for aquatic products. The DRS group had a TVB-N of 14.47 mg / 100g, the DBD group had a TVB-N of 17.03 mg / 100g, and the DRS+DBD synergistic treatment group had a TVB-N of only 14.93 mg / 100g by day 15, significantly lower than the CK and the single treatment groups, effectively delaying the spoilage process. Under a controlled atmosphere environment of 90% CO2 + 10% N2, high concentrations of CO2 showed a basic inhibitory effect on TVB-N formation. The TVB-N level on day 15 was 19.10 mg / 100g in the CK group, 14.47 mg / 100g in the DRS group, and 16.57 mg / 100g in the DBD group. The TVB-N level on day 15 in the DRS+DBD synergistic treatment group was 13.77 mg / 100g, which was the lowest among all groups, indicating the best preservation effect. Under a controlled atmosphere of 90% CO2 + 10% O2, the hyperoxia accelerated TVB-N formation. On day 15, the TVB-N level in the CK group reached 20.03 mg / 100g; in the DRS group, it was 14.47 mg / 100g; and in the DBD group, it was 17.03 mg / 100g. The synergistic treatment of DRS and DBD effectively inhibited spoilage, with TVB-N at 14.23 mg / 100g on day 15, significantly better than the single-treatment groups. The results showed that the long-term effect of DRS was again superior to DBD. This further confirms that radish seed extract can inhibit protein-degrading microorganisms through its sustained antibacterial activity, thereby slowing down TVB-N formation at its source. The combined application of DRS and DBD showed a significant effect. Its reduction in TVB-N was greater than the average effect of either treatment alone, indicating that the combined treatment can more effectively control protein spoilage throughout the storage period.

[0059] The changes in TBARS values ​​of rainbow trout samples after different treatments at 4℃ are as follows: Figure 4As shown, under a controlled atmosphere environment of 60% CO2 + 30% N2 + 10% O2, the oxidative stress (TOS) levels were 0.60 mg / kg in the CK group, 0.46 mg / kg in the DRS group, 0.44 mg / kg in the DBD group, and only 0.18 mg / kg in the DRS+DBD group. DRS, DBD, and their synergistic treatments had already affected the fish meat before storage. The polyphenols in DRS have antioxidant activity, and the low-temperature plasma in DBD can inactivate lipoxygenase. The synergistic effect of these two treatments significantly reduced the initial oxidation level, laying a low-oxidation foundation for subsequent storage. By day 15, the TBARS in the CK group reached a peak of 2.39 mg / kg, indicating that lipid oxidation had entered a severe stage. Although the TBARS in the DRS, DBD, and DRS+DBD groups were lower than those in the CK group, they were still at a relatively high level, at 1.57 mg / kg, 1.89 mg / kg, and 1.24 mg / kg, respectively. The DRS+DBD group effectively controlled lipid oxidation and significantly delayed the lipid oxidation process. Under a controlled atmosphere of 90% CO2 + 10% O2, the hyperoxic environment provided ample reactants for lipid oxidation, significantly accelerating the oxidation process. The TBARS increase rates were fastest in the CK and DBD groups, at 2.41 mg / kg and 2.05 mg / kg, respectively, indicating the most severe oxidation at the end of storage. The DRS and DRS+DBD treatment groups had lower TBARS values ​​than the other two groups, at 1.58 mg / kg and 1.46 mg / kg, respectively. Under a controlled atmosphere of 90% CO2 + 10% N2, the TBARS value of the CK group reached 1.99 mg / kg, while the TBARS values ​​of the DRS, DBD, and DRS+DBD groups were 1.40 mg / kg, 1.49 mg / kg, and 0.81 mg / kg, respectively. An anaerobic environment can inhibit the initiation of lipid oxidation at its source, and high concentrations of CO2 can also reduce oxidase activity. Therefore, the TBARS increase rates of all groups under this controlled atmosphere were the lowest, and the combined treatments also showed excellent antioxidant capacity.

[0060] Based on a comprehensive analysis of the changing trends of various indicators, the technical team determined that the triploid rainbow trout after composite treatment can have a shelf life of 12-15 days under refrigeration at 4℃.

[0061] like Figure 5The figure shows the juice loss rate of triploid rainbow trout during storage. Under a controlled atmosphere environment of 60% CO2 + 30% N2 + 10% O2, the juice loss rate of the CK group was 2.03% at the beginning of storage (DO); it increased to 2.80% on day 3; further increased to 4.03% on day 6 (D6); reached 5.03% on day 9; increased significantly to 7.17% on day 12; and reached a peak of 8.33% at the end of storage (D15). The CK group showed the fastest rate of increase throughout the storage period, with the highest juice loss rate at each time point, indicating the most severe deterioration in water retention. The juice loss rates of the DRS and DBD treatment groups were 1.20% and 1.75% on day 0, respectively, while the DRS+DBD treatment group had a loss rate of only 0.73%. By day 15, the DRS group had increased to 4.10%, and the DBD group to 5.27%. The DRS+DBD group had the slowest rate of increase, reaching 3.37% by day 15, significantly better than the CK, DRS, and DBD groups, demonstrating the best water retention effect. Under a controlled atmosphere environment of 90% CO2 + 10% N2, the DRS group reached 7.97% by day 15. Its initial rate of increase was slightly lower than the CK group (60% CO2 + 30% N2 + 10% O2). The DRS group reached 3.67% by day 15, with a gradual increase, and its juice loss rate at each time point was significantly lower than the CK group, maintaining better water retention than the DBD group in the later stages. The DBD group reached 4.97% by day 15. The DRS+DBD group reached 2.97% by day 15, with the slowest rate of increase throughout, and the lowest juice loss rate at each time point, making it the group with the best synergistic treatment effect among all controlled atmosphere groups. The sap loss rate reached a peak of 8.57% on day 15 under a controlled atmosphere environment of 90% CO2 + 10% N2, showing the fastest rate of increase throughout the treatment. From day 3 onwards, the sap loss rate was significantly higher than that of the control group (CK), indicating that the high-oxygen environment significantly accelerated the deterioration of water retention. The DRS group reached 4.43% on day 15, which could offset the negative effects of the high-oxygen environment to some extent. The sap loss rate at each time point was significantly lower than that of the CK group, but higher than that of the other two controlled atmosphere groups (DRS group). The DBD group reached 5.27% on day 15, and the DRS+DBD group reached 3.50% on day 15. The sap loss rate at each time point was the lowest within the group, and although affected by the high-oxygen environment, it was still significantly better than that of the other treatment groups within the group. The 90% CO2 + 10% N2 anaerobic high CO2 group had the lowest overall juice loss rate, followed by the 60% CO2 + 30% N2 + 10% O2 low oxygen group, and the 90% CO2 + 10% O2 high oxygen group had the highest. High oxygen environment significantly accelerates the deterioration of water retention and weakens the water retention advantage of high CO2 and synergistic treatment. The combined effect of anaerobic high CO2 environment and synergistic treatment is the most significant and can maintain the water retention of rainbow trout to the greatest extent.

[0062] The technical team measured the color characteristics of fish meat treated with different methods on days 0, 3, 6, 9, 12, and 15 of storage. Figure 6 As shown. After 15 days of storage, the brightness L of all groups... *The values ​​generally increased with prolonged storage time. The brightening of fish flesh is usually related to changes in the ability of muscle tissue to scatter light, which may stem from protein denaturation, juice loss, or surface microbial colony formation. The CK group showed the most significant increase in brightness, reaching its peak on day 15 (77.10-79.02), indicating severe deterioration in appearance. The combined DRS+DBD treatment most effectively suppressed the increase in brightness in most cases, maintaining a lower L value. * Value. a * The myoglobin value is a key indicator of the bright red color of meat and fish. A decrease in the myoglobin value usually means that myoglobin has been oxidized, and the color changes from bright red to brown, which is an important visual signal of quality deterioration. (All groups a) * The values ​​of a and b in the control group all decreased continuously with prolonged storage time, indicating that the bright red color of rainbow trout was gradually lost as myoglobin was gradually oxidized to methemoglobin, resulting in a duller color. * The value decreased most drastically, reaching its lowest point on day 15 (17.69-18.25), with severe color deterioration. The DRS+DBD combined treatment exhibited the highest a value across all gas conditions and time points. * The value indicates the strongest color retention capability. * The value is an indicator of the yellow color of a sample. In fish storage, b * An increase in the value is usually associated with the accumulation of lipid oxidation products, Maillard reactions, or the formation of certain microbial metabolites, and is another important signal of quality deterioration. All groups b * The values ​​all increased continuously with prolonged storage time, indicating that rainbow trout gradually turned yellow during storage. (CK's b...) * The value increased most significantly, reaching its peak on day 15 (42.56-42.99), with the most severe yellowing. The combined DRS+DBD treatment was the most effective at suppressing b in most cases (especially under optimal gas conditions). * The value increases. The DRS+DBD combination performs best in all three dimensions of color. It also achieves the lowest possible brightness (L). * ), highest redness (a * ) and the lowest yellowness (b * This means that the treated rainbow trout maintained their ideal color—bright red, natural, and not overly grayish-white or yellowish—even after 15 days. A 90% CO2 + 10% N2 anaerobic environment proved to be the optimal environment for maintaining color. Anaerobic conditions fundamentally prevent the oxidation of myoglobin and fats, which is crucial for maintaining the α value and controlling the β value. In an aerobic environment, the β values ​​of all treatment groups... *The values ​​(yellowness) were all higher, which directly proves that O2 promotes the oxidation reaction that causes yellowing. The combined treatment of DRS+DBD+90%CO2+10%N2 can most effectively maintain the color of fish meat that is closest to its fresh state, that is, prevent excessive brightening, maintain bright red, and inhibit abnormal yellowing.

[0063] The technical team used an electronic tongue to measure the flavor characteristics of fish treated with different methods on days 0 and 15 of storage. The measured indicators included PCA and various flavor parameters. The flavor characteristics of fish treated with 90% CO2 + 10% N2 were best preserved compared to those treated with 60% CO2 + 30% N2 + 10% O2 and 90% CO2 + 10% O2. Under the 90% CO2 + 10% N2 condition, the bitterness values ​​of DRS + DBD (0.85) and DBD (0.68) were significantly lower than those of CK (1.22). This indicates that the treatment, especially DBD, effectively inhibits the formation of bitter substances. There was little difference in astringency among the treatment groups, but the DRS + DBD and DRS groups maintained relatively low astringency. The DRS + DBD (16.96) group had the highest umami value, superior to CK (16.46), indicating that the combined treatment best preserved umami substances. The DRS+DBD (2.01) group exhibited the highest richness, significantly outperforming other groups, indicating its most mellow and full-bodied flavor. Under optimal gas conditions, the DRS+DBD combined treatment achieved the best balance across all dimensions of flavor, maximally suppressing bitterness caused by deterioration while best preserving the umami and richness of the fish itself. The DRS+DBD+90%CO2+10%N2 combined treatment most effectively maintained the good flavor profile of rainbow trout during storage, particularly significantly suppressing the production of bitterness and astringency, and better preserving umami and richness.

[0064] The technical team used an electronic nose to measure the odor characteristics of the fish meat on days 0 and 15 of storage. The measurement indicators included the response values ​​of PCA and different types of gas sensors. Figure 8As shown, most sensors (especially W2W, W5C, W1S, etc.) exhibit low response values, indicating that the odor quality is better maintained and closer to freshness. However, W1W, W2W, and W5S are more sensitive. After 15 days of storage, the response values ​​of W1W, W2W, and W5S using DRS+DBD are significantly lower than those using DRS alone, but still higher than CK and DBD, indicating that DBD offsets some of the effects of DRS. This shows that DBD alone performs very well in controlling the response values ​​of W5S and W2W sensors, comparable to or close to CK, indicating that it can effectively suppress the generation of nitrogenous odors and alcohol, aldehyde, and ketone odors. The effect of the DRS+DBD combined treatment is between that of DBD and DRS alone; it corrects some odor characteristic changes that DRS alone may cause, but compared to CK, the response values ​​of some sensors are still higher. This may be related to the volatile components contained in radish seed extract itself. Among the treatment groups operating in an oxygen-free environment of 90% CO2 + 10% N2, the sensor response values ​​for various odor substances were the lowest. The results indicate that oxygen-free controlled packaging is the most fundamental and effective measure for controlling the generation of putrid odors.

[0065] In conclusion, DBD+DRS combined with 90% CO2+10% N2 modified atmosphere packaging can maximize the protection of rainbow trout from deterioration in texture, color, aroma and taste during refrigeration, and the effect is better than that of any single technology.

[0066] The advancements of this invention compared to traditional single preservation technologies are reflected in the following aspects: First, dielectric barrier discharge treatment provides instantaneous surface sterilization under low-temperature, pollution-free conditions. Then, the polyphenolic compounds in the plant preservatives possess free radical scavenging capabilities, neutralizing the strong oxidizing substances generated by plasma treatment and preventing excessive oxidation of polyunsaturated fatty acids. Modified atmosphere packaging, by controlling the ratio of CO2, N2, and O2 gases, achieves this. High concentrations of CO2 inhibit the metabolic reproduction of spoilage bacteria and reduce enzyme activity; N2, as an inert filling gas, maintains the packaging shape and isolates it from external contamination; and a suitable low-oxygen or anaerobic environment slows down lipid oxidation and protein hydrolysis. This creates a low-deterioration storage microenvironment, delaying juice loss, microbial proliferation, and the formation of spoilage substances, thus extending the product's shelf life at both room temperature and low temperatures. The synergistic effect of these three technologies inhibits microbial growth while controlling lipid oxidation, solving the problem of accelerated lipid oxidation caused by single plasma treatment. The treatment sequence of first applying dielectric barrier discharge, then soaking in plant preservatives, and finally modifying atmosphere packaging overcomes the problem of uneven processing caused by the irregularity of the sample surface when directly processed. It reduces the oxidative damage of proteins caused by dielectric barrier discharge, maintains the good texture, flavor, and color characteristics of the fish, preserves the natural shape of the fish, and achieves multiple preservation goals of antibacterial, antioxidant, and maintenance of texture, flavor, and color characteristics.

[0067] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for cold storage and preservation of triploid rainbow trout using plant extracts combined with dielectric barrier discharge low-temperature plasma technology, characterized in that, After removing the oil from stir-fried radish seeds, water extraction was used to prepare a plant preservative. Triploid rainbow trout were gutted and skinned, then cut into uniform pieces. They were first treated in a dielectric barrier discharge device, then soaked in the de-oiled stir-fried radish seed extract according to the liquid-to-material ratio. Excess water was absorbed, and the treated triploid rainbow trout were sealed in a box filled with 90% CO2 + 10% N2 and stored in a refrigerated environment with regular testing of preservation indicators. Modified atmosphere packaging was used to address the problems of reduced preservation effect caused by meat being squeezed, rapid moisture loss, and accelerated color deterioration.

2. The method for cold storage and preservation of triploid rainbow trout according to claim 1, characterized in that, The dielectric barrier discharge device has a voltage of 130kV, a frequency of 80Hz, an electrode spacing of 60m, and a treatment time of 1 minute. The total number of colonies and the thiobarbituric acid value were determined by measuring different parameter combinations on the 3rd day after treatment.

3. The method for cold storage and preservation of triploid rainbow trout according to claim 2, characterized in that, The plant preservative is an aqueous extract of stir-fried radish seeds after oil removal. The oil removal method is pressing, and the oil content is less than 1%. The concentration of the preservative is 1 g / mL. The liquid-to-material ratio of the plant preservative and the fish pieces is 5:

1. The treatment time is 10 min. The total bacterial count and thiobarbituric acid value are determined by measuring the total bacterial count and thiobarbituric acid value on the 3rd day under different parameter combinations.

4. The method for cold storage and preservation of triploid rainbow trout according to claim 3, characterized in that, The modified atmosphere packaging uses a gas composition of 90% CO2 + 10% N2, which is determined by measuring the total bacterial count, color parameters, and juice loss rate on day 6 after treatment with different gas combinations.

5. The method for cold storage and preservation of triploid rainbow trout according to claim 4, characterized in that, The modified atmosphere packaging box is a PP (polypropylene) plastic box, and the film is made of PE (polyethylene). The determination is made by measuring the compressive strength of different materials and the juice loss rate and color on the 6th day after the packaging material is sealed.

6. The method for cold storage and preservation of triploid rainbow trout according to claim 5, characterized in that, The volume ratio of the modified atmosphere packaging box to the volume occupied by the fish meat is 3:1, which is determined by measuring the juice loss rate and color on the 6th day after treatment for different volume ratios.

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