A closed-loop nitrogen flushing gas replacement deoxygenation preservation method for roasted coffee beans

Abstract

This application relates to the field of coffee preparation technology, specifically disclosing a closed-loop nitrogen-flushing gas replacement method for preserving roasted coffee beans by deoxygenation. The method includes the following steps: S1, placing roasted and cooled roasted coffee beans into a sealed container, and then evacuating the container to create a negative pressure state; S2, while maintaining the negative pressure, injecting carbon dioxide gas into the sealed container in a pulsed manner, then maintaining a constant pressure, and extracting the resulting gas mixture from the sealed container under negative pressure; S3, repeating S2 to obtain roasted coffee beans treated with carbon dioxide pulse circulation; S4, filling the sealed container with nitrogen gas for pressurization and backfilling, resulting in roasted coffee beans ready for sealing; S5, subjecting the sealed container to a second negative pressure treatment, and then sealing the container. This deoxygenation preservation method can be used for the long-term storage of roasted coffee beans, and it has the advantage of sealing and displacing oxygen from the internal pores of the bean.

Description

Technical Field

[0001] This application relates to the field of coffee preparation technology, and more specifically, it relates to a closed-loop nitrogen flushing gas replacement deoxygenation and preservation method for roasted coffee beans. Background Technology

[0002] Coffee preparation technology is adaptable to various scenarios such as home consumption, offline stores, food processing, and retail sales, encompassing multiple processes including hand-drip extraction, Italian high-pressure brewing, low-temperature cold brewing, vacuum freeze-drying, and intelligent brewing. This technology can accurately extract coffee flavor compounds, weaken bitterness, retain natural aroma, and effectively improve beverage quality. Intelligent preparation equipment can standardize output, improve production efficiency, and reduce labor and operating costs. Freeze-drying technology can also lock in flavor activity, extend storage time, and meet the needs of ready-to-drink consumers. Various processes can adapt to different drinking preferences, taking into account taste quality, production efficiency, and ease of use, and promoting coffee consumption towards a higher quality of life.

[0003] Coffee preparation methods involve preserving roasted coffee beans through vacuum sealing. However, this physical isolation method can only create a low-oxygen environment inside the packaging container and cannot penetrate deep into the dense honeycomb-like pore structure inside the bean. It cannot effectively replace the residual oxygen adsorbed on the oil layer and the inner wall of the micropores. As a result, even when the coffee beans are sealed, they will still slowly oxidize due to the continuous presence of oxygen inside during storage and shelf life, causing degradation of flavor substances, loss of aroma, and deterioration of taste. Summary of the Invention

[0004] To address the issues of flavor degradation, aroma loss, and taste deterioration caused by vacuum preservation of roasted coffee beans, this application provides a closed-loop nitrogen flushing gas replacement deoxygenation preservation method for roasted coffee beans.

[0005] This application provides a closed-loop nitrogen flushing gas replacement deoxygenation and preservation method for roasted coffee beans, employing the following technical solution: A closed-loop nitrogen flushing gas replacement method for preserving roasted coffee beans by deoxygenation, comprising the following raw materials in parts by weight: S1. Place the roasted and cooled coffee beans into a sealed container, and vacuum the sealed container to create a negative pressure state inside the sealed container. S2. While maintaining the negative pressure state, carbon dioxide gas is injected into the sealed container in a pulse manner to increase the pressure inside the container and form a pressure pulse. Then, the pressure is kept constant, and the sealed container is quickly evacuated to make the pressure drop back to the negative pressure state. The generated mixed gas is then extracted from the sealed container under negative pressure. S3. Repeat S2 several times to obtain roasted coffee beans after carbon dioxide pulse cycle treatment; S4. Nitrogen gas is introduced into the sealed container for pressurization and backfilling, so that the pressure inside the container is restored to atmospheric pressure or slightly higher than atmospheric pressure, and roasted coffee beans to be sealed are obtained. S5. Perform a secondary negative pressure treatment on the sealed container: after evacuating again, quickly backfill with nitrogen to the target sealing pressure; then seal the sealed container.

[0006] By adopting the above technical solution, this method integrates deep negative pressure suction, carbon dioxide pulse injection and microbubble disturbance cleaning, nitrogen pressurization backfilling, and secondary negative pressure breathing into a multi-stage cyclic processing flow. First, a significant pressure difference is established inside and outside the container using deep negative pressure, driving the oxygen-containing gas sealed in the pore network of roasted coffee beans to escape outward along the pressure drop direction, extending the deoxygenation range from the external space between beans to the pore scale inside the bean. Then, under the condition of maintaining negative pressure, carbon dioxide is injected in a pulse manner, using pressure pulses to force the carbon dioxide deep into the pores of the bean. During the period of constant pressure maintenance, carbon dioxide, due to its high solubility in coffee oils, dissolves into the oil micro-regions attached to the inner wall of the pores, displacing and displacing the oxygen originally dissolved in the oils and occupying active sites in a dissolved state. During rapid vacuuming, the sudden pressure drop causes the dissolved carbon dioxide to reach supersaturation and rapidly escape from the oils, generating a large number of microbubbles in situ within the confined pore space. The nucleation, growth, and outward release of these bubbles generate oxygen-containing gas remaining in the pores. The physical entrainment and dragging action expels oxygen-containing gases from the deep pores of the coffee bean; multiple pulse cycles form a progressive sweeping and cleaning process, cleaning pore layers at different depths layer by layer; after carbon dioxide has completed the pore displacement and sweeping, nitrogen is introduced for pressurized backfilling. Nitrogen, as a chemically inert main protective gas, fills the gaps between beans and the space at the top of the container, creating a protective atmosphere for long-term storage; the secondary negative pressure treatment added before sealing triggers an additional breathing cycle in the pores of the coffee bean in the nitrogen environment, finally diluting and removing the extremely deep residual oxygen that was not fully reached in the previous steps; after sealing, the trace amounts of dissolved carbon dioxide remaining in the oils on the inner wall of the coffee bean pores are continuously and slowly released during storage, forming a local high carbon dioxide micro-atmosphere in the microenvironment of the bean, which together with the nitrogen protective atmosphere in the container space constitutes a dual protection system inside and outside; the entire process fundamentally solves the problem that a single nitrogen rinsing only acts on the space between beans and cannot effectively remove oxygen from the pores inside the bean, overcoming the bottleneck of replacement efficiency caused by the similar physical properties of nitrogen and oxygen.

[0007] Preferably, before step S1, the process further includes: cooling the roasted coffee beans to 20°C to 35°C before placing them into the sealed container for vacuum treatment.

[0008] By adopting the above technical solution, the roasted coffee beans are cooled to a suitable temperature range before being placed in a sealed container for subsequent processing. This temperature range is higher than room temperature but does not cause accelerated thermal oxidation of oil components. This allows the gas in the pores of the coffee beans to maintain high molecular activity when the beans enter the negative pressure processing stage. This facilitates the smoother escape of pore gas to the outside under the pressure difference during subsequent vacuuming. At the same time, it avoids excessive loss of volatile aromatic substances caused by the high-temperature beans directly entering the deep negative pressure environment, thus establishing a balance between deoxygenation efficiency and aroma preservation.

[0009] Preferably, in step S1, the absolute pressure of the negative pressure state is 5 kPa to 30 kPa; after reaching the target negative pressure, the negative pressure state is maintained for 5 to 30 minutes.

[0010] By adopting the above technical solution, the absolute pressure inside the sealed container is reduced to the negative pressure range to establish a significant pressure difference sufficient to drive the gas inside the bean pores to migrate outward along the interconnected pores. This causes the oxygen-containing gas sealed in the pore network to be released outward through a viscous flow mechanism, which significantly improves the gas discharge rate compared to the passive mass transfer method that relies solely on concentration diffusion. After reaching the target negative pressure, a constant pressure is maintained for a period of time, providing a sufficient time window for the gas inside the bean to continuously migrate from the deep pores to the external space under the drive of the pressure difference. This allows the vacuuming not only to dilute the air in the container space but also to have a deeper effect on the pore scale of the bean.

[0011] Preferably, in step S2, when carbon dioxide gas is injected in a pulse manner, a single pulse injection increases the pressure inside the container by 10 kPa to 50 kPa.

[0012] By adopting the above technical solution, carbon dioxide is injected in a pulse manner and the pressure rise of each pulse is controlled to form intermittent pressure fluctuations in the container. This allows carbon dioxide to penetrate into the pore network of the coffee bean in stages under the pressure difference of each pulse. Compared with continuous constant pressure injection, pulse injection avoids the formation of stable airflow short-circuit channels in the gaps between beans, allowing carbon dioxide to reach the surface of roasted coffee beans in the stack of beans more effectively and improving the uniformity of carbon dioxide distribution in the whole bean.

[0013] Preferably, in step S2, the pressure after pulse injection is maintained at a constant value for 30 seconds to 5 minutes.

[0014] By adopting the above technical solution, a constant pressure holding period is set after pulse injection, allowing sufficient time for the carbon dioxide gas injected into the pores of the bean to come into gas-liquid contact with the oil micro-regions attached to the inner wall of the pores. Carbon dioxide molecules cross the gas-liquid interface and dissolve into the oil phase, completing the replacement and dissipation of the molecular oxygen originally dissolved in the oil. This constant pressure dissolution stage is the step in which carbon dioxide is transformed from a simple gas phase filling medium into a dissolved functional medium. The retention of dissolved carbon dioxide in the oil provides a material basis for the microbubble nucleation in the subsequent rapid vacuuming stage.

[0015] Preferably, in step S2, a rapid vacuum is performed to reduce the pressure to a negative pressure level of 5 kPa to 30 kPa.

[0016] By adopting the above technical solution, rapid vacuuming causes the pressure inside the container to drop rapidly to a deep negative pressure level in a short time, resulting in a sudden supersaturation of dissolved carbon dioxide in the oil phase. Carbon dioxide molecules rapidly aggregate and nucleate in the porous oil and grow into microbubbles. As these in-situ generated bubbles expand and release outward within the confined space of the pores, they exert a physical entrainment and dragging effect on the remaining free oxygen-containing gas in the pores, actively carrying out oxygen from the bean body in narrow pores and oil-covered micro-areas that are difficult to reach by simply relying on external pressure difference suction. The rapid pressure drop rate is conducive to the nucleation of bubbles deep in the pore network rather than just precipitation in the surface pores, thus expanding the coverage depth of bubble disturbance cleaning.

[0017] Preferably, in step S3, step S2 is repeated 3 to 8 times.

[0018] By adopting the above technical solution, a progressive sweeping cleaning mechanism is formed by repeatedly performing cyclic operations of carbon dioxide pulse injection, constant pressure dissolution and maintenance, and rapid vacuuming. In each cycle, the trace dissolved carbon dioxide remaining in the pore grease after the previous cycle provides a pre-dissolution channel for the carbon dioxide injected in the new cycle, reducing the mass transfer resistance at the gas-liquid interface and allowing the carbon dioxide dissolution and penetration of the subsequent cycle to be more profound. At the same time, the clean pore space cleared by the bubble sweep in the previous cycle provides a new free volume for the nucleation of the bubble in the new cycle, allowing the bubble disturbance in the subsequent cycle to reach the finer pore areas that were not fully developed in the previous cycle. The multiple cycles are not simply repeated and accumulated, but rather show a coupled progressive effect of increasing penetration depth and expanding sweeping coverage with the number of cycles.

[0019] Preferably, in step S4, nitrogen gas is introduced to restore the pressure inside the container to 105 kPa to 120 kPa; the nitrogen gas introduced is food-grade high-purity nitrogen gas.

[0020] By adopting the above technical solution, after deep pore cleaning is completed by carbon dioxide pulse circulation, food-grade high-purity nitrogen is used for pressurized backfilling to restore the pressure inside the container to a slightly positive pressure level slightly higher than atmospheric pressure. Nitrogen, as the main chemically inert protective gas, fills the gaps between beans and the space at the top of the container. At the same time, the backfill airflow further dilutes and pushes out the mixture of carbon dioxide and oxygen remaining in the gaps between beans and the container space in the previous steps. The slightly positive pressure sealing state slightly higher than atmospheric pressure forms an outward pressure gradient inside and outside the container, which inhibits the infiltration of external ambient air into the interior due to container micro-leakage during storage, thereby enhancing the sealing reliability for long-term storage.

[0021] Preferably, in step S5, the specific operation of the secondary negative pressure treatment is as follows: the sealed container is evacuated again to reduce the pressure to 60kPa to 80kPa, and then quickly backfilled with nitrogen to the target sealing pressure.

[0022] By adopting the above technical solution, a secondary negative pressure treatment is inserted after nitrogen backfilling to the target pressure and before sealing. An additional pressure fluctuation cycle is performed in the established main nitrogen protective atmosphere. When vacuuming is performed again, the space inside the bean pores that was occupied by nitrogen in the previous step re-forms a pressure gradient from the inside to the outside, causing the trace amount of oxygen remaining in the deepest part of the pores to migrate to the outside of the pores and mix with the nitrogen in the container space. Then, nitrogen is quickly backfilled, and the repeated entry and exit of nitrogen is used to finally dilute and remove the deep layers of pores. This secondary negative pressure treatment takes advantage of the premise that the previous carbon dioxide pulse cycle has removed most of the oxygen in the pores, and precisely intervenes in the most difficult-to-reach residual oxygen at the end of the deoxygenation stage.

[0023] Preferably, step S5 also includes the following storage requirement: trace amounts of dissolved carbon dioxide remain in the oil on the inner wall of the coffee bean pores inside the sealed container.

[0024] By adopting the above technical solution, the trace amount of dissolved carbon dioxide remaining in the oil on the inner wall of the pores of the sealed roasted coffee beans is slowly released from the oil phase into the pore microspace during long-term storage, continuously forming a local low-oxygen, high-carbon dioxide micro-atmosphere around the bean, which continuously buffers and blocks the trace oxygen that slowly escapes from the very deep pores inside the bean during storage; the residual dissolved carbon dioxide and the nitrogen protective atmosphere in the main space of the container form a complementary dual protection system on a spatial scale, which continuously plays an anti-oxidation and antibacterial role throughout the entire storage period before the packaging is opened, delaying the oxidative decay of flavor substances in the roasted coffee beans.

[0025] In summary, this application has the following beneficial effects: 1. Because this application adopts a cyclic processing method that combines deep negative pressure suction with carbon dioxide pulse injection and rapid vacuuming, the pressure difference drives the oxygen-containing gas in the pores of the roasted coffee bean to escape outward, and the carbon dioxide dissolution-precipitation process in the pore oil generates microbubbles in situ to sweep away the deep pores, thus achieving the effect of sealing and displacing the oxygen in the pores of the bean.

[0026] 2. In this application, a process combining multiple pulse cycles with secondary negative pressure treatment under nitrogen is preferred. After the pre-cycle removes most of the oxygen from the pores, the secondary negative pressure causes nitrogen to repeatedly enter and exit the pores to dilute and remove residual oxygen in the deep layers. Therefore, the deoxygenation depth is gradually increased from the shallow to the deep pores, resulting in a more thorough removal of gas inside the bean.

[0027] 3. The method of this application uses carbon dioxide as a transitional treatment medium for pore permeation and displacement. After oxygen displacement is completed, nitrogen is introduced to construct the main protective atmosphere. The trace amount of dissolved carbon dioxide remaining in the pore oil after sealing is continuously released during storage to form a local high carbon dioxide micro-atmosphere. Therefore, internal and external protection is obtained by combining nitrogen protection in the container space with carbon dioxide buffering in the bean microenvironment, thus extending the shelf life of roasted coffee beans. Attached Figure Description

[0028] Figure 1 This is a flowchart of a closed-loop nitrogen flushing gas replacement deoxygenation and preservation method for roasted coffee beans proposed in this application. Detailed Implementation

[0029] The present application will be further described in detail below with reference to the accompanying drawings and embodiments.

[0030] Technical concept: Coffee preparation methods involve preserving roasted coffee beans through vacuum sealing. However, this physical isolation method can only create a low-oxygen environment inside the packaging container and cannot penetrate deep into the dense honeycomb-like pore structure inside the bean. It cannot effectively replace the residual oxygen adsorbed on the oil layer and the inner wall of the micropores. As a result, even when the coffee beans are sealed, they will still slowly oxidize due to the continuous presence of oxygen inside during storage and shelf life, causing degradation of flavor substances, loss of aroma, and deterioration of taste.

[0031] This application discloses a closed-loop nitrogen-purging gas replacement method for preserving roasted coffee beans. The method includes the following steps: S1, placing roasted and cooled coffee beans into a sealed container, and evacuating the container to create a negative pressure state; S2, while maintaining the negative pressure, injecting carbon dioxide gas into the sealed container in a pulsed manner, then maintaining a constant pressure, and extracting the resulting gas mixture from the sealed container under negative pressure; S3, repeating S2 to obtain roasted coffee beans treated with carbon dioxide pulse circulation; S4, filling the sealed container with nitrogen gas for pressurization and backfilling to obtain roasted coffee beans to be sealed; S5, subjecting the sealed container to a second negative pressure treatment, and then sealing the container.

[0032] This application employs a cyclic processing method that combines deep negative pressure suction with carbon dioxide pulse injection and rapid vacuuming. It utilizes the pressure difference to drive the oxygen-containing gas inside the pores of roasted coffee beans to escape outward, and uses the dissolution and precipitation process of carbon dioxide in the pore oils to generate microbubbles in situ to sweep away the deep pores. Therefore, it achieves the effect of sealing in the pores of the bean and displacing and expelling the oxygen.

[0033] Example 1: This example provides a closed-loop nitrogen flushing gas replacement deoxygenation and preservation method for roasted coffee beans, comprising the following steps: S1. Place the roasted and cooled coffee beans into a sealed container and vacuum the container to create a negative pressure environment. The process involves cooling the roasted coffee beans to 20°C and then placing them in a sealed container for vacuum treatment. The absolute pressure of the negative pressure state is 5 kPa; after reaching the target negative pressure, the negative pressure state is maintained for 30 minutes.

[0034] S2. While maintaining a negative pressure, inject carbon dioxide gas into the sealed container in a pulse manner to increase the pressure inside the container and form a pressure pulse. Then maintain the pressure constant, and then quickly evacuate the sealed container to make the pressure drop back to a negative pressure state. The resulting mixed gas is then extracted from the sealed container under negative pressure. When carbon dioxide gas is injected in a pulse manner, a single pulse injection increases the pressure inside the container by 10 kPa. The pressure after pulse injection is maintained at a constant value for 5 minutes. Among these measures, a rapid vacuum was implemented to reduce the pressure to a negative pressure level of 5 kPa.

[0035] S3. Repeat S2 to obtain roasted coffee beans after carbon dioxide pulse circulation treatment; S2 is repeated 3 times.

[0036] S4. Pressurize and backfill the sealed container with nitrogen gas to restore the pressure inside the container to atmospheric pressure or slightly higher than atmospheric pressure, and obtain roasted coffee beans to be sealed. Nitrogen gas is introduced to restore the pressure inside the container to 105 kPa; the nitrogen gas introduced is food-grade high-purity nitrogen.

[0037] S5. Perform secondary negative pressure treatment on the sealed container: After evacuating the vacuum again, quickly backfill with nitrogen to the target sealing pressure; then seal the sealed container. The specific operation of the secondary negative pressure treatment is as follows: the sealed container is evacuated again to reduce the pressure to 60 kPa, and then nitrogen is quickly used to backfill to the target sealing pressure. This also includes the following storage requirements: in the sealed container, trace amounts of dissolved carbon dioxide remain in the oils on the inner walls of the coffee beans' pores.

[0038] Example 2: This example provides a closed-loop nitrogen flushing gas replacement deoxygenation and preservation method for roasted coffee beans, comprising the following steps: S1. Place the roasted and cooled coffee beans into a sealed container and vacuum the container to create a negative pressure environment. The process involves cooling the roasted coffee beans to 27.5°C and then placing them in a sealed container for vacuum treatment. The absolute pressure under negative pressure is 17.5 kPa; after reaching the target negative pressure, the negative pressure state is maintained for 17.5 minutes.

[0039] S2. While maintaining a negative pressure, inject carbon dioxide gas into the sealed container in a pulse manner to increase the pressure inside the container and form a pressure pulse. Then maintain the pressure constant, and then quickly evacuate the sealed container to make the pressure drop back to a negative pressure state. The resulting mixed gas is then extracted from the sealed container under negative pressure. Among them, when carbon dioxide gas is injected in a pulse manner, a single pulse injection increases the pressure inside the container by 30 kPa. The pressure was kept constant after the pulse injection for 2.75 minutes. Among these measures, rapid vacuuming was implemented to reduce the pressure to a negative pressure level of 17.5 kPa.

[0040] S3. Repeat S2 to obtain roasted coffee beans after carbon dioxide pulse circulation treatment; S2 is repeated 5 times.

[0041] S4. Pressurize and backfill the sealed container with nitrogen gas to restore the pressure inside the container to atmospheric pressure or slightly higher than atmospheric pressure, and obtain roasted coffee beans to be sealed. Nitrogen gas was introduced to restore the pressure inside the container to 112.5 kPa; the nitrogen gas introduced was food-grade high-purity nitrogen.

[0042] S5. Perform secondary negative pressure treatment on the sealed container: After evacuating the vacuum again, quickly backfill with nitrogen to the target sealing pressure; then seal the sealed container. The specific operation of the secondary negative pressure treatment is as follows: the sealed container is evacuated again to reduce the pressure to 70 kPa, and then nitrogen is quickly used to backfill to the target sealing pressure. This also includes the following storage requirements: in the sealed container, trace amounts of dissolved carbon dioxide remain in the oils on the inner walls of the coffee beans' pores.

[0043] Example 3: This example provides a closed-loop nitrogen flushing gas replacement deoxygenation and preservation method for roasted coffee beans, comprising the following steps: S1. Place the roasted and cooled coffee beans into a sealed container and vacuum the container to create a negative pressure environment. The process involves cooling the roasted coffee beans to 35°C and then placing them in a sealed container for vacuum treatment. The absolute pressure of the negative pressure state is 30 kPa; after reaching the target negative pressure, the negative pressure state is maintained for 5 minutes.

[0044] S2. While maintaining a negative pressure, inject carbon dioxide gas into the sealed container in a pulse manner to increase the pressure inside the container and form a pressure pulse. Then maintain the pressure constant, and then quickly evacuate the sealed container to make the pressure drop back to a negative pressure state. The resulting mixed gas is then extracted from the sealed container under negative pressure. When carbon dioxide gas is injected in a pulse manner, a single pulse injection increases the pressure inside the container by 50 kPa. The pressure after pulse injection is maintained at a constant value for 30 seconds. Among these measures, a rapid vacuum was implemented to reduce the pressure to a negative pressure level of 30 kPa.

[0045] S3. Repeat S2 to obtain roasted coffee beans after carbon dioxide pulse circulation treatment; S2 is repeated 8 times.

[0046] S4. Pressurize and backfill the sealed container with nitrogen gas to restore the pressure inside the container to atmospheric pressure or slightly higher than atmospheric pressure, and obtain roasted coffee beans to be sealed. Nitrogen gas is introduced to restore the pressure inside the container to 120 kPa; the nitrogen gas introduced is food-grade high-purity nitrogen.

[0047] S5. Perform secondary negative pressure treatment on the sealed container: After evacuating the vacuum again, quickly backfill with nitrogen to the target sealing pressure; then seal the sealed container. The specific operation of the secondary negative pressure treatment is as follows: the sealed container is evacuated again to reduce the pressure to 80 kPa, and then nitrogen is quickly used to backfill to the target sealing pressure. This also includes the following storage requirements: in the sealed container, trace amounts of dissolved carbon dioxide remain in the oils on the inner walls of the coffee beans' pores.

[0048] Comparative Example 1: This comparative example refers to the content of Example 1, except that the roasted coffee beans were cooled to 10°C and then placed in a sealed container for vacuum treatment. The rest of the content is the same as Example 1.

[0049] Comparative Example 2: This comparative example refers to the content of Example 1, except that the absolute pressure of the negative pressure state in S1 is 3 kPa, and the negative pressure state is maintained for 30 minutes. The rest of the content is the same as Example 1.

[0050] Comparative Example 3: This comparative example refers to the content of Example 1, except that when carbon dioxide gas is injected in a pulse manner in S2, a single pulse injection increases the pressure inside the container by 5 kPa. The rest of the content is the same as that of Example 1.

[0051] Comparative Example 4: This comparative example refers to the content of Example 1, except that the pressure after pulse injection is maintained constant for 15 seconds in S2, and the rest is the same as Example 1.

[0052] Comparative Example 5: This comparative example refers to the content of Example 1, except that S2 is repeated once in S3, and the rest of the content is the same as that of Example 1.

[0053] Comparative Example 6: This comparative example refers to the content of Example 1, except that the specific operation of the secondary negative pressure treatment in S5 is as follows: the sealed container is evacuated again to reduce the pressure to 40 kPa, and then nitrogen is quickly used to backfill to the target sealing pressure. The rest of the content is the same as that in Example 1.

[0054] Performance testing Sample preparation: Roasted coffee beans from the same batch in the Colombian Huilan region, cooled to room temperature after roasting, were selected as raw materials. Gas replacement deoxygenation treatment was performed according to the methods described in the examples and comparative examples, and the beans were sealed in airtight containers of the same specifications. Three parallel samples were prepared for each treatment group. A blank control group was also set up. In the blank control group, roasted and cooled coffee beans were directly placed into airtight containers and sealed without vacuuming, gas injection, or any replacement treatment. After sealing, all samples were stored in a constant temperature and humidity environment at 25°C and 50% relative humidity, protected from light, for subsequent testing of various performance indicators.

[0055] Oxygen concentration detection in the container after storage: After the sealed sample is stored under constant temperature, humidity and light-proof conditions for 30 days, the oxygen concentration in the headspace gas inside the container is detected using a headspace gas analyzer equipped with an oxygen sensor; during the detection, a sampling needle is inserted through the sealed part of the container to extract the headspace gas sample, and the volume percentage value of the oxygen concentration is recorded; this detection is used to reflect the actual effect of each processing method on the displacement and discharge of oxygen in the pores of roasted coffee beans and the degree of slow release of residual oxygen in the beans into the container space during storage; the oxygen concentration detection is carried out in accordance with GB / T6285 "Determination of Trace Oxygen in Gases - Electrochemical Method".

[0056] Determination of flavor retention rate of roasted coffee beans after storage: After storing the sealed samples under constant temperature, humidity and light-proof conditions for 90 days, the roasted coffee beans were opened and removed. The content of characteristic volatile flavor compounds in the roasted coffee beans was detected by headspace solid-phase microextraction combined with gas chromatography-mass spectrometry. The same mass of roasted coffee bean samples were weighed, ground to the same particle size, placed in headspace vials and sealed. After adsorption of volatile components by the solid-phase microextraction fiber head under the same temperature and time conditions, the adsorbed components were injected into the gas chromatography-mass spectrometry instrument for analysis. Pyrazines, furans, aldehydes and ketones, which are characteristic aroma compounds of coffee, were selected for qualitative and quantitative analysis. At the same time, freshly roasted coffee beans that have not been stored were used as a flavor benchmark control. The determination of flavor retention rate was carried out in accordance with GB / T28971 "Aroma Evaluation Method of Flavorings" and GB / T27525 "Determination of Volatile Flavor Compounds in Food by Gas Chromatography-Mass Spectrometry".

[0057] Gas replacement completion time detection: During the gas replacement deoxygenation process in each embodiment and comparative example, the oxygen concentration in the container was monitored in real time using a container pressure gauge and a headspace gas analyzer. Timing started from the vacuuming in step S1 and ended when the oxygen concentration in the container dropped to the lowest stable level achievable by each method, and the fluctuation of the values ​​in three consecutive sampling tests did not exceed 10% of the lowest value. The total processing time required was recorded. This detection is used to reflect the influence of the pulse cycle number, constant pressure holding time, and secondary negative pressure treatment steps on the gas replacement efficiency. The determination of oxygen concentration and time during the treatment process was carried out in accordance with GB / T6285 "Electrochemical Method for the Determination of Trace Oxygen in Gases".

[0058] Sealing reliability testing: The sealed samples were stored under constant temperature, humidity and light-proof conditions for 180 days. The oxygen concentration inside the container was sampled and tested every 30 days using a headspace gas analyzer, and the change curve of oxygen concentration over storage time was recorded. At the same time, the container sealing condition was observed for obvious deformation or signs of gas leakage. This test is used to reflect the effect of nitrogen pressurization backfilling and micro-positive pressure sealing on inhibiting the infiltration of external air during long-term storage, as well as the ability of the dual protection system formed by the continuous release of dissolved carbon dioxide in the pore grease to maintain the stability of the microenvironment. The sealing performance was tested in accordance with GB / T15171 "Test Method for Sealing Performance of Flexible Packaging".

[0059] Table 1: Performance Test Results Comparison Table ; Example Conclusion: As can be seen from Examples 1 to 3 and Comparative Example 1, and Table 1, cooling the roasted coffee beans to the temperature range defined in this application before vacuuming facilitates the smooth escape of gas from the pores of the beans under pressure difference, while avoiding the increase in oil viscosity due to excessively low temperature, which would hinder the dissolution and penetration of carbon dioxide in subsequent steps, thus affecting the deoxygenation efficiency and flavor retention rate.

[0060] As can be seen from Examples 1 to 3 and Comparative Example 2, and in conjunction with Table 1, controlling the absolute pressure of the negative pressure state in step S1 within the range defined in this application can establish a sufficient pressure difference to drive the pore gas to migrate outward while avoiding adverse effects on the porous structure of the coffee beans due to excessive vacuuming, thus balancing the deoxygenation depth and aroma retention effect.

[0061] As can be seen from Examples 1 to 3 and Comparative Example 3, and Table 1, when the pressure increase in the container caused by a single pulse injection in step S2 is within the range defined in this application, the pulse pressure is sufficient to effectively push carbon dioxide into the depth of the bean pores, so that the subsequent dissolution, displacement and microbubble sweeping effects can be fully utilized. If the pressure is insufficient, the penetration depth of carbon dioxide in the bean will be limited, and the oxygen displacement effect will be significantly weakened.

[0062] Based on Examples 1 to 3 and Comparative Example 4, and in conjunction with Table 1, it can be seen that maintaining a constant pressure for a sufficient time after pulse injection in step S2 is a condition for carbon dioxide to fully dissolve and enter the porous grease, thereby replacing and displacing dissolved oxygen in the grease. If the constant pressure holding time is too short, the amount of dissolved carbon dioxide generated will be insufficient, which will weaken the microbubble entrainment and sweeping effect in the subsequent rapid vacuuming stage and affect the overall deoxygenation depth.

[0063] As can be seen from Examples 1 to 3 and Comparative Example 5, and in conjunction with Table 1, the number of repeated pulse cycles in step S3 is within the range defined in this application. It is possible to gradually clean the pore layers at different depths through multiple progressive sweeps. A single cycle cannot effectively reach the deep layers where oxygen is trapped. Multiple cycles are the factor that enables the oxygen removal depth to be progressively increased from shallow to deep layers and makes the gas inside the bean more thoroughly removed.

[0064] As can be seen from Examples 1 to 3 and Comparative Example 6, and Table 1, the pressure drop of the secondary negative pressure treatment in step S5 is within the range defined in this application. It can accurately dilute and remove the residual oxygen in the deep layer in the established main nitrogen protective atmosphere. When the secondary negative pressure is too large, it will destroy the pore gas balance state formed in the previous steps, which is not conducive to maintaining the microenvironment stability and flavor substance retention effect during long-term storage.

[0065] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A closed-loop nitrogen flushing gas replacement method for preserving roasted coffee beans by deoxygenation, characterized in that, Includes the following steps: S1. Place the roasted and cooled coffee beans into a sealed container, and vacuum the sealed container to create a negative pressure state inside the sealed container. S2. While maintaining the negative pressure state, carbon dioxide gas is injected into the sealed container in a pulse manner to increase the pressure inside the container and form a pressure pulse. Then, the pressure is kept constant, and the sealed container is quickly evacuated to make the pressure drop back to the negative pressure state. The generated mixed gas is then extracted from the sealed container under negative pressure. S3. Repeat S2 several times to obtain roasted coffee beans after carbon dioxide pulse cycle treatment; S4. Nitrogen gas is introduced into the sealed container for pressurization and backfilling, so that the pressure inside the container is restored to atmospheric pressure or slightly higher than atmospheric pressure, and roasted coffee beans to be sealed are obtained. S5. Apply a secondary negative pressure treatment to the sealed container; then seal the sealed container.

2. The method for preserving roasted coffee beans using a closed-loop nitrogen flushing gas replacement deoxygenation method according to claim 1, characterized in that, Before step S1, the process includes: cooling the roasted coffee beans to 20°C to 35°C, and then placing them into the sealed container for vacuum treatment.

3. The method for preserving roasted coffee beans using a closed-loop nitrogen flushing gas replacement deoxygenation method according to claim 1, characterized in that, In step S1, the absolute pressure of the negative pressure state is 5 kPa to 30 kPa; after reaching the target negative pressure, the negative pressure state is maintained for 5 to 30 minutes.

4. The method for preserving roasted coffee beans using a closed-loop nitrogen flushing gas replacement deoxygenation method according to claim 1, characterized in that, In step S2, when carbon dioxide gas is injected in a pulse manner, a single pulse injection increases the pressure inside the container by 10 kPa to 50 kPa.

5. The method for preserving roasted coffee beans using a closed-loop nitrogen flushing gas replacement deoxygenation method according to claim 1, characterized in that, In step S2, the pressure after pulse injection is maintained at a constant level for 30 seconds to 5 minutes.

6. The method for preserving roasted coffee beans using a closed-loop nitrogen flushing gas replacement deoxygenation method according to claim 1, characterized in that, In step S2, a rapid vacuum is applied to reduce the pressure to a negative pressure level of 5 kPa to 30 kPa.

7. The method for preserving roasted coffee beans using a closed-loop nitrogen flushing gas replacement deoxygenation method according to claim 1, characterized in that, In step S3, S2 is repeated 3 to 8 times.

8. The method for preserving roasted coffee beans using a closed-loop nitrogen flushing gas replacement deoxygenation method according to claim 1, characterized in that, In step S4, nitrogen gas is introduced to restore the pressure inside the container to 105 kPa to 120 kPa; the nitrogen gas introduced is food-grade high-purity nitrogen gas.

9. The method for preserving roasted coffee beans using a closed-loop nitrogen flushing gas replacement deoxygenation method according to claim 1, characterized in that, In step S5, the specific operation of the secondary negative pressure treatment is as follows: the sealed container is evacuated again to reduce the pressure to 60kPa to 80kPa, and then nitrogen is quickly used to backfill to the target sealing pressure.

10. The method for preserving roasted coffee beans using a closed-loop nitrogen flushing gas replacement deoxygenation method according to claim 1, characterized in that, Step S5 also includes the following storage requirement: trace amounts of dissolved carbon dioxide remain in the oils on the inner wall of the coffee beans after sealing the sealed container.

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