Low-temperature drying method of euphausia superba shipborne processing sample

Abstract

The invention belongs to the technical field of euphausia superba shipborne processing, and particularly relates to a supercritical fluid CO2 low-temperature drying method for an euphausia superba shipborne processing process sample. According to the method, a minced euphausia superba sample obtained after shipborne processing and solid-liquid separation of euphausia superba is used as a raw material, and dried euphausia superba powder can be obtained through supercritical fluid CO2 low-temperature drying. The method is simple to operate, low in drying temperature, low in consumption and environment-friendly, and the obtained shrimp meal is good in quality, high in protein utilization rate and suitable for land-based processing, is also suitable for direct on-site utilization after CO2 capture of ocean krill ships in the future, so that carbon emission of ships is reduced, and the method has very good application prospects and social and economic benefits.

Description

Technical Field

[0001] This invention belongs to the field of Antarctic krill deep processing technology, and relates to a drying method for Antarctic krill samples processed on a ship, specifically a supercritical fluid CO2 low-temperature drying method for Antarctic krill samples processed on a ship. Existing technology

[0002] Antarctic krill is a product of a small planktonic crustacean, primarily the Antarctic krill (Euphausia superba), caught in fishing areas such as FAO 48.1, 48.2, and 48.3 in the Southern Ocean. It is rich in high-quality lipids, proteins, chitin, and minerals, with reserves exceeding 600 million tons, demonstrating immense development and utilization value. Antarctic krill oil is sold in many countries worldwide and was approved as a new resource food in my country in 2013. Its main components include phospholipids and glycerides bound to polyunsaturated fatty acids such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which have cardiovascular health benefits, as well as free or bound astaxanthin, a powerful antioxidant. It has now been developed into a high-value food product highly regarded in the market. Antarctic krill oil is crude oil and its soft capsule products made from Antarctic krill powder produced on board ships as a single raw material through extraction, refining and other processes. It meets the requirements of SC / T 3506-2020 for qualified or superior products, among which EPA, DHA, phospholipids and astaxanthin are key quality indicators.

[0003] The quality of Antarctic krill oil products on the market varies greatly. While some products list ingredients from other sources as compound products, the main reason for the quality differences in pure Antarctic krill oil lies in the variations in krill powder raw materials and extraction processes, especially the quality of the krill raw materials caught during Antarctic shipboard processing and the differences in drying process parameters. In the existing shipboard processing of Antarctic krill powder on vessels such as the "Shenlan" and "Fuxinghai" in my country, the freshly caught krill raw materials undergo rapid cooking and solid-liquid separation using a horizontal centrifuge. Some krill powder production processes use atmospheric pressure high-temperature drying, while a more efficient technology is vacuum drying. This involves drying the krill paste with a moisture content of approximately 60% at a vacuum degree of -0.02 to -0.05 MPa and a temperature of 80 to 95℃ or even above 100℃ for 2 to 4 hours. The resulting krill powder meets the requirements of SC / T 3507-2022, with qualified products having a moisture content ≤12% or superior products having a moisture content ≤10% also meeting the corresponding protein and fat content indicators. However, prolonged high-temperature drying processes can easily cause oxidation and deterioration of key krill oil functional components such as EPA, DHA, and phospholipids. Therefore, it is necessary to develop a low-temperature drying method for Antarctic krill powder and promote its widespread application in the industry.

[0004] More importantly, CO2 capture and storage (CCS) is an indispensable technology for addressing global climate change. Large-scale CO2 capture and storage projects such as Huaneng Gansu Zhengning Power Plant and the Enping 15-1 Oilfield in the Pearl River Estuary have been successfully implemented. CO2 capture on large and medium-sized ocean-going vessels has also laid a solid foundation for industrial application. The 711 Research Institute of China Shipbuilding Industry Corporation in Shanghai has developed a closed-loop industrial chain for container ship CO2 capture systems, storage, transshipment, and reuse. Building on this foundation, the development of shipboard processing technology based on supercritical fluid CO2 utilization for Antarctic krill harvesting and processing vessels has the potential to become a key support for the green and low-carbon transformation of the entire industrial chain in the future. Supercritical fluid CO2 low-temperature drying is a technology that uses carbon dioxide in a supercritical state (critical temperature 31℃, critical pressure 7.39MPa) to dry materials. Its core principle is to use the low surface tension and high diffusion coefficient characteristics of supercritical CO2 to replace the solvent in materials under mild conditions (usually ≤80℃), avoiding the shrinkage or structural damage caused by traditional drying methods. Therefore, the production of Antarctic krill powder based on supercritical fluid CO2 low-temperature drying technology is expected to enable direct on-site utilization of CO2 after capture on ocean-going krill vessels in the future, thereby reducing ship carbon emissions and CO2 ocean transportation costs, and has good application prospects and social benefits. Summary of the Invention

[0005] To address the problems existing in the prior art, the purpose of this invention is to provide a low-temperature drying method for krill surimi samples with a moisture content of approximately 60% obtained during Antarctic krill shipboard processing, and to obtain krill powder products with qualified moisture content. This invention uses krill surimi samples with a moisture content of approximately 60% obtained after solid-liquid separation during Antarctic krill shipboard processing as raw material, and dries them at low temperature using supercritical fluid CO2 to obtain dried krill powder. This method is simple to operate, uses low drying temperatures, and yields high-quality krill powder, showing promising application prospects.

[0006] To achieve the above-mentioned objectives, the technical solution adopted by this invention is a low-temperature drying method for shipboard processing samples of Antarctic krill, comprising the following steps:

[0007] (1) Pretreatment of shrimp paste samples;

[0008] (2) The pretreated shrimp paste samples were dried at low temperature using supercritical fluid CO2;

[0009] (3) Pack the dried shrimp powder into bags and seal them, then refrigerate them. At the same time, take a sample of the shrimp powder to determine its moisture content.

[0010] Furthermore, in step (1), the pretreatment includes taking frozen shrimp paste samples from a land-based processing workshop and thawing them at room temperature for 1-2 hours until they can be dispersed into naturally loose particles, or directly using a horizontal centrifuge to separate the solid and liquid components of the shrimp paste samples in a ship-based processing workshop.

[0011] Furthermore, in step (1), the pretreated shrimp paste sample has a water content of 60% to 66%.

[0012] Further, in step (2), the shrimp paste sample pretreated in step (1) is weighed, filled into the extraction vessel, and after the cap is tightened, it is connected to the supercritical fluid CO2 equipment; the extraction container pressure and temperature, as well as the separation pressure, separation temperature, CO2 flow rate and other parameters are set for drying.

[0013] Furthermore, in step (2), the volume of the extraction vessel is 5L, the amount of shrimp paste sample is 0.8-1.3 kg, the pressure of the extraction vessel is 30-39 MPa, the temperature is 45-60 ℃, the separation pressure of separation I is 8-10 MPa, the temperature is 40-45 ℃, the separation pressure of separation II is 6-7 MPa, the temperature is 35-40 ℃, and the drying time is 3-4 h.

[0014] Furthermore, in step (2), the amount of shrimp paste sample loaded is 1.0 kg, the extraction vessel pressure is 39 MPa and the temperature is 60℃, the separation pressure of separation I is 9 MPa and the temperature is 45℃, the separation pressure of separation II is 7 MPa and the temperature is 38℃, and the drying time is 4 h.

[0015] Furthermore, the volume of the extraction vessel is 29L, the amount of shrimp paste sample filled is 4.5-5.5kg, the pressure of the extraction vessel is 45-60MPa, the temperature is 50-60℃, the separation pressure of separation I is 9-10MPa, the temperature is 40-45℃, the separation pressure of separation II is 6-7MPa, the temperature is 35-40℃, and the drying time is 3-4h.

[0016] Furthermore, the shrimp paste sample was loaded with 5.0 kg, the extraction vessel pressure was 50 MPa and the temperature was 55 ℃, the separation pressure of separation I was 10 MPa and the temperature was 45 ℃, the separation pressure of separation II was 7 MPa and the temperature was 35 ℃, and the drying time was 3.5 h.

[0017] Furthermore, in step (2), the material in the drying process is in supercritical fluid CO2 and the temperature is ≤60℃.

[0018] Furthermore, in step (2), the material temperature during the drying process is ≤60℃.

[0019] The drying method for shipboard processed Antarctic krill samples described in this invention has the following significant technical advantages:

[0020] 1. During the drying process, the material is in supercritical fluid CO2 at a temperature ≤60℃, which can effectively prevent the oxidation and deterioration of heat-sensitive components such as phospholipids and polyunsaturated fatty acids.

[0021] 2. During the drying process, the material temperature is ≤60℃, which preserves the activity of the main protein components well, allowing for subsequent enzymatic hydrolysis and improving the yield of bioactive peptides.

[0022] 3. The drying process uses supercritical fluid CO2 as the main solvent, and the drying temperature is ≤60℃, which saves a lot of energy required for high-temperature heating, high vacuum or other microwave and hot air drying. The production process is clean and environmentally friendly.

[0023] 4. Based on the application of CO2 capture in large and medium-sized ocean-going vessels, if the supercritical fluid CO2 low-temperature drying technology of this invention is introduced into Antarctic krill fishing and processing vessels in the future, it is expected to realize the direct on-site utilization of CO2 after capture, which will significantly reduce the carbon emissions of ships in Antarctic waters, protect the local environment, and have extremely high social benefits.

[0024] In summary, the method described in this invention creatively utilizes supercritical fluid CO2 low-temperature drying technology in the drying method of Antarctic krill shipborne processing samples. It is simple to operate, produces high-quality products, and is low-consumption and environmentally friendly, thus possessing very high production application value. Attached Figure Description

[0025] Figure 1 This is a flowchart of a method for drying Antarctic krill samples on a ship, as described in a specific embodiment of the present invention.

[0026] Figure 2 This is a schematic diagram of a supercritical fluid CO2 extraction system (TH12-5 type) in a specific embodiment of the present invention. Detailed Implementation

[0027] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments and accompanying drawings, but they should not be construed as limiting the scope of protection of the present invention.

[0028] In the specific embodiment of the present invention, the Antarctic krill seaborne processed shrimp paste sample came from the "Shenlan" ship of Jiangsu Shenlan Ocean Fishery Co., Ltd. The Thar SFC supercritical fluid chromatograph was manufactured by Agilent Technologies Inc., and the supercritical fluid CO2 extraction system (TH12-5 type, TH32-29×3 type) was manufactured by Shanghai Chengdong Technology Co., Ltd.

[0029] like Figure 1 As shown, a low-temperature drying method for shipboard processing samples of Antarctic krill includes the following steps:

[0030] (1) Pretreatment of shrimp paste samples;

[0031] In this embodiment, the pretreatment includes taking frozen shrimp paste samples from a land-based processing workshop, thawing them at room temperature for 1-2 hours until they can be dispersed into naturally loose particles, or directly using a horizontal centrifuge to separate the solid and liquid components in a ship-based processing workshop. The pretreated shrimp paste samples have a water content of 60%-66%.

[0032] (2) The pretreated shrimp paste samples were dried at low temperature using critical fluid CO2;

[0033] In this embodiment, the shrimp paste sample after pretreatment in step (1) is weighed, filled into the extraction vessel, and connected to the supercritical fluid CO2 equipment after the cap is tightened; the extraction container pressure and temperature, as well as separation pressure, separation temperature, CO2 flow rate and other parameters are set for drying.

[0034] In this embodiment, when the volume of the extraction vessel is 5L, the amount of shrimp paste sample loaded is 0.8-1.3 kg, the extraction vessel pressure is 30-39 MPa, the temperature is 45-60 ℃, the separation pressure of separation I is 8-10 MPa, the temperature is 40-45 ℃, the separation pressure of separation II is 6-7 MPa, the temperature is 35-40 ℃, and the drying time is 3-4 h.

[0035] The volume of the extraction vessel can also be 29L, the amount of shrimp paste sample filled is 4.5-5.5kg, the pressure of the extraction vessel is 45-60MPa, the temperature is 50-60℃, the separation pressure of separation I is 9-10 MPa, the temperature is 40-45℃, the separation pressure of separation II is 6-7 MPa, the temperature is 35-40℃, and the drying time is 3-4 h.

[0036] During the drying process, the material is in supercritical fluid CO2 at a temperature ≤60℃.

[0037] (3) After the drying process is stopped, take out the extraction vessel, open the lid, put the dried shrimp powder into a bag and seal it, and store it in the refrigerator. At the same time, take a shrimp powder sample to determine the moisture content.

[0038] Example 1: Collection and Moisture Content Detection of Antarctic Krill Paste Samples

[0039] Ten different batches of "Deep Blue" Antarctic krill sludge samples were collected and labeled as samples 1-10. Sample information is shown in Table 1. The water content a and b were determined using a rapid moisture analyzer and the first method of GB 5009.236-2016, respectively.

[0040] Table 1. Information on 10 Antarctic krill paste samples from the "Deep Blue" research vessel.

[0041]

[0042] Meanwhile, 100 g of each loose shrimp paste sample was weighed, its natural bulk volume was measured, and its average bulk density was calculated to be 0.26 ± 0.07 kg / L.

[0043] Example 2: Supercritical fluid drying of a small sample of Antarctic krill paste

[0044] Using the krill paste sample from the "Deep Blue" ship No. 3 in Example 1 as raw material, 15 g of krill paste sample was placed in a cylindrical stainless steel container (10×250 mm), sealed, and then connected to a Thar SFC supercritical fluid chromatograph for drying. The parameter settings and extraction pressure readings from the instrument for each of the nine drying experiments are shown in Table 2. After each drying process, the shrimp powder sample was taken out, mixed, bagged, sealed, and refrigerated. At the same time, the moisture content of the shrimp powder sample was determined by a rapid moisture analyzer. The data of each dried sample are shown in Table 2.

[0045] Table 2. Results of supercritical fluid drying of small sample sizes.

[0046]

[0047] Observations revealed a significant difference in the degree of dryness between the upper and lower sections of the stainless steel container (10 mm in diameter and 250 mm in length), indicating that the length-to-diameter ratio of the container affects the drying of the samples.

[0048] Example 3: Supercritical fluid CO2 drying of Antarctic krill paste samples using a small-scale device.

[0049] Using the krill paste sample from the "Deep Blue" ship No. 3 in Table 1 of Example 1 as raw material, 1.0 kg of krill paste sample was placed into a 5 L extraction vessel, sealed, and then inoculated with... Figure 2 The small-scale TH12-5 supercritical fluid CO2 extraction system was used for drying. The instrument parameters for the four experiments are shown in Table 3, with a CO2 flow rate of approximately 60 L / h. After the drying process was stopped, the shrimp powder samples were taken out, mixed, bagged, sealed, and refrigerated. At the same time, the moisture content of the shrimp powder samples was randomly selected and measured using a rapid moisture analyzer. The sample data are shown in Table 3.

[0050] Table 3. Results of supercritical fluid CO2 drying of Antarctic krill paste samples using small-scale equipment.

[0051]

[0052] Observations revealed that the difference in the degree of sample drying between the upper and lower sections of the 5L extraction vessel (approximately 10 cm in diameter and 60 cm in length) was small, indicating that the short and thick container is beneficial for sample drying.

[0053] Example 4: Supercritical fluid CO2 drying of Antarctic krill paste samples in a medium-sized equipment

[0054] Using the krill paste sample from the "Deep Blue" ship No. 3 in Example 1 as raw material, 4.0, 5.0, and 6.0 kg of krill paste samples were placed in a 29 L extraction vessel for three experiments. After sealing, the samples were connected to a pilot-scale TH32-29×3 supercritical fluid CO2 extraction system for drying. The parameters of each experimental instrument are shown in Table 4, and the CO2 flow rate was approximately 500 L / h. After the drying process was stopped, the shrimp powder sample was taken out, mixed, bagged, sealed, and refrigerated. At the same time, the moisture content of the shrimp powder sample was determined by a rapid moisture analyzer. The sample data are shown in Table 4.

[0055] Table 4. Results of supercritical fluid CO2 drying of Antarctic krill paste samples from the pilot plant.

[0056]

[0057] Example 5: Determination of acid value and peroxide value of dried krill powder samples

[0058] 50g of the dried krill powder sample obtained in Experiment 4-2 of Example 4 and 50g of two commercially available Antarctic krill powder samples were weighed into conical flasks. 150 mL of anhydrous ethanol was added and the samples were extracted at room temperature for 4 h. After centrifugation at 4500 rpm for 10 min at room temperature, the supernatant was collected into a 500 mL heart-shaped flask. 150 mL of anhydrous ethanol was added to the precipitate and the above operation was repeated. The supernatants were combined and the solvent was completely evaporated at 50 °C to obtain Antarctic krill powder oil samples. The acid value and peroxide value of the two krill oil samples were determined according to the provisions of Method II of GB5009.229-2025 and Method I of GB5009.227-2023, respectively. The data results are shown in Table 5.

[0059] Table 5. Acid value and peroxide value data after krill powder extraction.

[0060]

[0061] The results showed that the acid value and peroxide value of krill powder dried by supercritical fluid CO2 at low temperature were lower than those of krill powder dried by vacuum heating, indicating that supercritical fluid CO2 at low temperature can effectively prevent the oxidation and deterioration of heat-sensitive components such as phospholipids and polyunsaturated fatty acids, resulting in better quality.

[0062] Example 6: Enzymatic hydrolysis of dried krill powder samples and frozen Antarctic krill

[0063] In three 2L Erlenmeyer flasks, 100 g of dried krill powder obtained in Experiment 4-2 of Example 4 and 1400 g of commercially available Antarctic krill powder were added to each flask, along with 500 g of frozen Antarctic krill and 1000 g of pure water. 6 g of trypsin was then added to each flask for hydrolysis. The temperature was controlled at 50℃, and after 6 h of enzymatic hydrolysis, the temperature was raised to 90℃ for 10 min to inactivate the enzyme. The flasks were then centrifuged at 10000 rpm for 10 min at room temperature. The supernatant was collected in a 2L round-bottom flask, and the solvent was completely evaporated at 50℃ to obtain Antarctic krill active peptide samples. The yield was calculated by weighing, and the proportion of protein fragments with a molecular weight <1000 u was determined using the high-performance gel filtration chromatography method in Appendix A of GB / T 22729-2008. The results are shown in Table 6.

[0064] Table 6. Data on the yield of active peptides and content of oligopeptides after protease hydrolysis of krill meal.

[0065]

[0066] Note: The yield for 500 g of frozen Antarctic krill is also calculated based on 100 g of dry matter.

[0067] The results showed that the yield of bioactive peptides from krill powder dried at low temperature with supercritical fluid CO2 was significantly higher than that from krill powder dried by vacuum heating, and the proportion of oligopeptides was also higher; however, it was lower than that from frozen Antarctic krill. This indicates that krill powder dried at low temperature with supercritical fluid CO2 can effectively prevent protein denaturation, making it more suitable for subsequent enzymatic hydrolysis to prepare bioactive peptide products.

[0068] In supercritical fluid CO2 low-temperature drying technology, the CO2 gas compression and recovery rate is as high as 70% or more, while vacuum heating drying temperature reaches 80 or even 100 ℃, requiring a large amount of energy from equipment such as heating steam, condensate cooling, and vacuum pumps. This technology is more environmentally friendly. In particular, the direct application of this technology for onboard processing and drying of krill meal after CO2 capture on ocean-going fishing vessels can save energy, reduce emissions, and conserve freshwater, resulting in more significant economic and social benefits.

[0069] As can be seen from the above embodiments, the present invention provides a method for low-temperature drying of Antarctic krill shipborne processing samples based on existing commercial supercritical CO2 fluid extraction equipment. During the drying process, the material is in supercritical fluid CO2 at a temperature ≤60℃, which can effectively prevent the oxidation and deterioration of heat-sensitive components such as phospholipids and polyunsaturated fatty acids, as well as protein denaturation.

[0070] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for low-temperature drying of Antarctic krill samples processed on board a ship, comprising the following steps: (1) Pretreatment of shrimp paste samples; (2) The pretreated shrimp paste samples were dried at low temperature using supercritical fluid CO2; (3) Pack the dried shrimp powder into bags and seal them, then refrigerate them. At the same time, take a sample of the shrimp powder to determine its moisture content.

2. The low-temperature drying method for shipborne processing samples of Antarctic krill as described in claim 1, characterized in that: In step (1), the pretreatment includes taking frozen shrimp paste samples from a land-based processing workshop and thawing them at room temperature for 1-2 hours until they can be dispersed into naturally loose particles, or directly using a horizontal centrifuge to separate the solid and liquid components of the shrimp paste samples in a ship-based processing workshop.

3. The low-temperature drying method for shipborne processing samples of Antarctic krill as described in claim 2, characterized in that: In step (1), the pretreated shrimp paste sample has a water content of 60% to 66%.

4. The low-temperature drying method for shipborne processed samples of Antarctic krill as described in claim 1, characterized in that: In step (2), weigh the shrimp paste sample after pretreatment in step (1), fill it into the extraction vessel, tighten the cap and connect it to the supercritical fluid CO2 equipment; set the extraction container pressure, temperature, separation pressure, separation temperature, CO2 flow rate and other parameters, and dry it.

5. The low-temperature drying method for shipborne processing samples of Antarctic krill as described in claim 1, characterized in that: In step (2), the volume of the extraction vessel is 5L, the amount of shrimp paste sample is 0.8-1.3 kg, the pressure of the extraction vessel is 30-39 MPa, the temperature is 45-60 ℃, the separation pressure of separation I is 8-10 MPa, the temperature is 40-45 ℃, the separation pressure of separation II is 6-7 MPa, the temperature is 35-40 ℃, and the drying time is 3-4 h.

6. The low-temperature drying method for shipborne processed samples of Antarctic krill as described in claim 5, characterized in that: In step (2), the amount of shrimp paste sample loaded is 1.0 kg, the extraction vessel pressure is 39 MPa and the temperature is 60℃, the separation pressure of separation I is 9 MPa and the temperature is 45℃, the separation pressure of separation II is 7 MPa and the temperature is 38℃, and the drying time is 4 h.

7. The low-temperature drying method for shipborne processed samples of Antarctic krill as described in claim 1, characterized in that: The extraction vessel has a volume of 29L, the amount of shrimp paste sample loaded is 4.5-5.5 kg, the extraction vessel pressure is 45-60 MPa and the temperature is 50-60℃, the separation pressure of separation I is 9-10 MPa and the temperature is 40-45℃, the separation pressure of separation II is 6-7 MPa and the temperature is 35-40℃, and the drying time is 3.5-4 h.

8. The low-temperature drying method for shipborne processed samples of Antarctic krill as described in claim 7, characterized in that: The shrimp paste sample was loaded with 5.0 kg. The extraction vessel pressure was 50 MPa and the temperature was 55 ℃. Separation I was carried out at a pressure of 10 MPa and a temperature of 45 ℃, and separation II was carried out at a pressure of 7 MPa and a temperature of 35 ℃. The drying time was 3.5 h.

9. A low-temperature drying method for shipboard processed samples of Antarctic krill as described in any one of claims 1 to 8, characterized in that: In step (2), the material is in supercritical fluid CO2 and the temperature is ≤60℃ during the drying process.

10. A method for low-temperature drying of Antarctic krill samples processed on a ship, as described in any one of claims 1 to 8, characterized in that: In step (2), the material temperature during the drying process is ≤60℃.

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