A process for retarding oxidation of pet food and apparatus therefor
Patent Information
- Application Number
- CN202611304127.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-08-26
- Publication Date
- 2026-11-03
AI Technical Summary
Existing technologies cannot effectively identify and remove oxygen trapped in the pores inside freeze-dried meat particles before mixing them with puffed particles coated with oil, leading to accelerated oxidation after packaging and affecting food quality.
By applying pressure reduction, pressure holding, and low-oxygen gas back pressure in a low-oxygen sealed cavity, a pore oxygen release response chain is established to identify pore-retained oxygen. When the oxygen concentration rebound amplitude and peak value after two consecutive pressure pulses meet the limit, mixing and sealing are allowed. Differential treatments such as incremental pressure difference and low-speed agitation are used to ensure complete oxygen discharge.
It effectively identifies and removes oxygen from inside freeze-dried meat particles, reducing the risk of oxidation and off-flavors after packaging, improving food quality, and reducing breakage of freeze-dried meat particles and consumption of low-oxygen gas.
Smart Images
Figure CN123023674A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of food technology, and in particular to a process and equipment for delaying the oxidation of pet food. Background Technology
[0002] In pet food, freeze-dried meat particles are often mixed with puffed pellets coated with oil to balance nutrition, flavor, and palatability. Since oils are easily oxidized in the presence of oxygen, current processing methods typically employ low-oxygen treatments such as vacuuming or nitrogen filling before mixing or packaging. The oxygen concentration in the processing or packaging space is then monitored to determine if the packaging conditions are met.
[0003] However, freeze-dried meat particles contain numerous interconnected pores. While the oxygen concentration in the detection space can be rapidly reduced during vacuuming and low-oxygen gas replacement, oxygen located deep within the pores or obscured by the particle contact surface may not be released simultaneously and may be slowly released after gas supply is stopped, particle agitation, mixing, or packaging. Existing technologies release products based solely on the instantaneous oxygen concentration at the end of the low-oxygen treatment, easily leading to the acceptance of freeze-dried meat particles still containing oxygen trapped in the pores. This oxygen continues to be released after mixing with oil-containing puffed particles on the surface, causing a rebound in the oxygen concentration inside the packaged food and accelerating oil oxidation. Therefore, we propose a process and equipment for delaying oxidation in pet food. Summary of the Invention
[0004] The purpose of this invention is to provide a process and equipment for delaying the oxidation of pet food, so as to solve the problems mentioned in the background art.
[0005] To achieve the above objectives, the present invention provides the following technical solution: a process for delaying the oxidation of pet food, comprising:
[0006] Before the two types of particles were mixed, representative samples were obtained from freeze-dried meat particles. Pressure reduction, pressure holding and low oxygen gas back pressure were applied sequentially in a low oxygen closed cavity. The pressure change in the cavity was correlated with the rise, peak and fall of oxygen concentration to establish a pore oxygen release response chain.
[0007] The freeze-dried meat particles to be processed are fed into the pulse deoxygenation chamber, and the pressure is repeatedly reduced and the oxygen is restored by increasing pressure difference. The oxygen concentration rebound process obtained after stopping the gas supply after each restoration is compared with the pore oxygen release response chain.
[0008] When the oxygen concentration rises again after the gas supply is stopped, and the rising sequence is consistent with the pore oxygen release response chain, it is determined that there is pore retained oxygen, and mixing with oil-containing expanded particles on the surface is prohibited. The corresponding pressure holding stage is extended according to the delay stage of the rebound.
[0009] When the oxygen concentration rebound after two consecutive pressure pulses is no greater than 0.15 percentage points and the rebound peak is no higher than 0.5%, the mixing restriction is lifted, and the processed freeze-dried meat particles are mixed with the oil-containing puffed particles on the surface in a low-oxygen buffer zone and then packaged.
[0010] Preferably, when establishing the pore oxygen release response chain, the oxygen concentration in the low-oxygen sealed cavity is adjusted to below 1%, reduced from atmospheric pressure to 35-55 kPa and held for 8-20 seconds, and then back-pressurized to 80-95 kPa with a gas with an oxygen concentration not higher than 0.5%; after the back-pressurization is completed, the inlet valve is closed and held for 30-120 seconds, and the oxygen concentration decrease segment during the decompression period, the oxygen concentration rise segment after back-pressurization, and the tail segment after the rise are recorded in the order of occurrence.
[0011] Preferably, the same pressure pulse is applied simultaneously to the empty low-oxygen sealed cavity and the low-oxygen sealed cavity containing non-porous inert particles of the same volume as the freeze-dried meat particles, and the oxygen concentration changes of the two are used to determine the residual gas replacement baseline of the cavity and the pipeline return baseline; only the increase and tailing of the oxygen concentration of the representative sample relative to the two baselines are registered as the pore oxygen release response of the freeze-dried meat particles.
[0012] Preferably, based on the time of occurrence after the back pressure ends, the pore oxygen release response is divided into a rapid oxygen release segment of 0-10s, a delayed oxygen release segment of 10-45s, and a trailing oxygen release segment after 45s; when the cumulative increase in oxygen concentration in the delayed oxygen release segment or the trailing oxygen release segment accounts for more than 40% of the cumulative increase in oxygen concentration in this batch, the batch of freeze-dried meat particles is marked as a batch with risk of oxygen rebound after packaging.
[0013] Preferably, an incremental differential pressure pulse is applied to the batch with the risk of oxygen rebound after packaging. The minimum pressure of the first pressure pulse is 55-65 kPa, and the minimum pressure of each subsequent pressure pulse is reduced by 5-10 kPa. The next pressure pulse is started only after the oxygen release phase of the previous pressure pulse has entered a continuous decreasing state, so as to avoid the oxygen release process of adjacent pressure pulses from overlapping.
[0014] Preferably, after the oxygen concentration rebound is identified, a pressure difference verification pulse with a pressure difference of 50% to 70% of the previous pressure difference is applied; if the oxygen concentration rise in the verification pulse still occurs after the pressure return ends, and no corresponding rise occurs in the empty low oxygen sealed cavity, it is confirmed that the oxygen concentration rebound originates from the connecting pores of the freeze-dried meat particles, rather than from air leakage in the cavity or residual oxygen in the gas supply.
[0015] Preferably, the deoxygenation action is selected based on the oxygen release segment with the highest proportion in the pore oxygen release response: when the rapid oxygen release segment has the highest proportion, the instantaneous replacement flow rate of low-oxygen gas is increased; when the delayed oxygen release segment has the highest proportion, the freeze-dried meat particles are turned over at low speed and the pressure holding is extended under the lowest pressure; when the tailing oxygen release segment has the highest proportion, two short-term backpressures are used instead of one backpressure, and a no-gas-supply residence period is set between the two backpressures.
[0016] Preferably, the low-speed turning is achieved by intermittent rotation of the porous bearing cylinder. Each rotation causes the freeze-dried meat particles to loosen and rearrange once and then stops. The oxygen concentration is collected in the stopped state. When the oxygen concentration rises after rotation but remains stable before rotation, the oxygen amount corresponding to this rise is included in the oxygen retained in the pores blocked by the particle contact surface, and an additional low-speed turning and pressure holding combination action is added.
[0017] Preferably, the freeze-dried meat particles are transferred to a low-oxygen buffer zone isolated from the outside environment and left to stand for 60–180 seconds, during which the supply of low-oxygen gas is stopped; when the oxygen concentration rebounds by more than 0.15 percentage points or the peak exceeds 0.5%, the freeze-dried meat particles are sent back to the pulse deoxygenation chamber through the reflux channel; when the limit is met for two consecutive standing periods, the isolation gate is opened, allowing the freeze-dried meat particles to mix with the oil-containing puffed particles on the surface and directly enter the packaging station.
[0018] An apparatus for delaying the oxidation of pet food, for carrying out a process for delaying the oxidation of pet food as described in any of the preceding claims.
[0019] The technical effects and advantages of this invention are as follows:
[0020] (1) This invention sequentially applies decompression, pressure holding and low oxygen back pressure to representative samples of freeze-dried meat particles, and associates the pressure changes with the order of rise, peak and fall of oxygen concentration after the back pressure stops to form a pore oxygen release response chain. This response chain is used to identify the oxygen concentration rebound caused by the release of oxygen from the pores of freeze-dried meat particles during batch processing, and can distinguish between the instantaneous low oxygen state in the processing space and the actual residual oxygen state inside the freeze-dried meat particles. The mixing restriction is lifted only when the rebound amplitude and peak value after two consecutive pressure pulses meet the limit, thereby avoiding the misjudgment of the processing as qualified before the oxygen in the pores is discharged, reducing the risk of oxygen concentration rebound after packaging and oxidation, off-flavor and decreased palatability of oil-containing puffed particles on the surface.
[0021] (2) The present invention establishes the cavity residual gas replacement baseline and pipeline return baseline by using an empty low oxygen sealed cavity and non-porous inert particles, and uses a pressure difference verification pulse to verify the source of oxygen concentration rise again. This can eliminate the interference of cavity dead zone residual oxygen, gas supply residual oxygen, pipeline return and cavity leakage on the detection results, improve the accuracy of pore oxygen release judgment, and reduce misprocessing or misrelease caused by equipment fluctuations.
[0022] (3) Based on the proportion of the rapid oxygen release section, the delayed oxygen release section and the tailing oxygen release section, the present invention selects to increase the instantaneous replacement flow rate, extend the pressure holding or segmented back pressure and other deoxygenation actions according to the proportion of the rapid oxygen release section, the delayed oxygen release section and the tailing oxygen release section. It also performs pre-packaging verification by having the low oxygen buffer zone stand without gas supply. It can implement differentiated treatment for different pore oxygen release characteristics. While improving the oxygen discharge effect of deep pores and contact surface shielding oxygen, it reduces unnecessary deep vacuuming, low oxygen gas consumption and continuous turning, and reduces the possibility of freeze-dried meat particles breaking. Attached Figure Description
[0023] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention, but do not constitute a limitation thereof. In the drawings:
[0024] Figure 1 This is a flowchart illustrating the establishment and risk identification process for the pore oxygen release response of the present invention.
[0025] Figure 2 This is a flowchart illustrating the progressive deoxidation and hybrid packaging release process of the present invention. Detailed Implementation
[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0027] This invention provides, for example Figures 1-2 A process for delaying oxidation in pet food, as shown, includes:
[0028] Before the two types of particles were mixed, representative samples were obtained from freeze-dried meat particles. Pressure reduction, pressure holding and low oxygen gas back pressure were applied sequentially in a low oxygen closed cavity. The pressure change in the cavity was correlated with the rise, peak and fall of oxygen concentration to establish a pore oxygen release response chain.
[0029] The freeze-dried meat particles to be processed are sent into the pulse deoxygenation chamber, and the pressure is repeatedly reduced and the oxygen is restored by increasing pressure difference. The oxygen concentration rebound process obtained after stopping the gas supply after each restoration is compared with the pore oxygen release response chain.
[0030] When the oxygen concentration rises again after the gas supply is stopped, and the rising sequence is consistent with the pore oxygen release response chain, it is determined that there is pore retained oxygen. Mixing with oil-containing expanded particles on the surface is prohibited, and the corresponding pressure holding stage is extended according to the delay stage of the rebound.
[0031] When the oxygen concentration rebound after two consecutive pressure pulses is no greater than 0.15 percentage points and the rebound peak is no higher than 0.5%, the mixing restriction is lifted, and the processed freeze-dried meat particles are mixed with the oil-containing puffed particles on the surface in a low-oxygen buffer zone and then packaged.
[0032] In practice, the representative sample is preferably obtained by taking samples from the upper, middle and lower parts of the same batch of freeze-dried meat particles and mixing them. The particle size, moisture content and stacking thickness of the representative sample correspond to the freeze-dried meat particles to be processed. The representative sample is placed in a low-oxygen sealed chamber. First, it is replaced with nitrogen gas or a mixture of nitrogen and carbon dioxide with an oxygen volume fraction of no more than 0.5% until the oxygen concentration in the chamber is below 1%. Then, depressurization, pressure holding and pressure return are performed in sequence. The absolute pressure after depressurization can be set to 40-65 kPa, pressure holding for 10-30 s, and pressure return to 90-100 kPa. After pressure return is completed, the air inlet valve is closed and the pressure and oxygen concentration are continuously recorded for 30-120 s. Based on the end of pressure return, the time when the oxygen concentration begins to rise, the highest value and the time when it falls back to the stable value are recorded. A pore oxygen release response chain is formed according to the sequential relationship of "pressure recovery - oxygen concentration rise - peak appearance - gradual decline".
[0033] During batch processing, freeze-dried meat particles are loaded into a breathable carrier cylinder, and pulse deoxygenation is performed sequentially using pressure differentials from small to large. For example, the minimum absolute pressure is decreased in increments of 60 kPa, 50 kPa, and 40 kPa. Each time, the gas supply is cut off after the pressure returns and the cylinder is left to stand for testing. If the oxygen concentration rise time corresponds to the representative sample response chain and the chamber pressure does not rise abnormally, it is determined that the oxygen comes from the pores of the freeze-dried meat particles, rather than from external leakage. For batches where the rise occurs earlier, the depressurization and holding time is extended. For batches where the rise occurs later after the pressure returns, the no-gas-supply standing time after the pressure returns is extended. Each time, the time is extended by 10 to 30 seconds before testing again. When two consecutive tests show that the rebound amplitude is not greater than 0.15 percentage points and the peak value is not higher than 0.5%, the freeze-dried meat particles are transferred to a buffer zone to maintain a low-oxygen state, mixed with oil-containing puffed particles on the surface, and immediately packaged.
[0034] The above-described implementation method utilizes the characteristic of repeated time sequence of oxygen release from the pores of freeze-dried meat particles, and combines pressure changes with oxygen concentration rebound to make judgments, which can avoid false acceptance caused by judging solely based on the instantaneous oxygen concentration before packaging. By adjusting the holding pressure or standing time for different oxygen release stages, ineffective vacuuming and over-processing can be reduced, and the reduction of fat oxidation, off-flavor, and palatability caused by the migration of pore oxygen to oil-containing puffed particles after packaging can be reduced.
[0035] When establishing the pore oxygen release response chain, the oxygen concentration in the low-oxygen sealed cavity is adjusted to below 1%, reduced from atmospheric pressure to 35-55 kPa and held for 8-20 seconds, and then back-pressurized to 80-95 kPa with a gas with an oxygen concentration not exceeding 0.5%. After the back-pressurization is completed, the inlet valve is closed and held for 30-120 seconds. The oxygen concentration decrease segment during the decompression period, the oxygen concentration rise segment after back-pressurization, and the tailing segment after the rise are recorded in the order of occurrence.
[0036] In practice, a representative sample of freeze-dried meat particles from the same batch is laid flat in a low-oxygen sealed chamber, ensuring its thickness is roughly the same as during batch processing. The oxygen concentration inside the chamber is reduced to below 1% through low-oxygen gas replacement. The vacuum system is then activated to reduce the absolute pressure inside the chamber from atmospheric pressure to 35–55 kPa and maintain this pressure for 8–20 seconds, allowing gas to migrate outwards from the pores of the freeze-dried meat particles. Nitrogen gas or a mixture of nitrogen and carbon dioxide with an oxygen concentration not exceeding 0.5% is then introduced to restore the pressure inside the chamber to 80–95 kPa. After the pressure return is complete, the inlet and outlet valves are closed, and the chamber is kept sealed for 30–120 seconds. Pressure and oxygen concentration are recorded synchronously at sampling intervals not exceeding 1 second.
[0037] Using the start of decompression, the end of backpressure, and the end of the sealed state as segment nodes, the section where the oxygen concentration decreases with pumping during decompression is registered as the oxygen concentration decrease segment; the section where the oxygen concentration changes from a stable state to a continuous increase and reaches a peak after the backpressure ends is registered as the oxygen concentration rise segment; and the section where the oxygen concentration gradually decreases or tends to stabilize after the peak is registered as the tailing segment after the rise. According to the occurrence sequence of the decrease segment, rise segment, and tailing segment, and recording the duration, oxygen concentration change, and peak occurrence time of each segment, a pore oxygen release response chain for the corresponding batch is formed.
[0038] The above treatment can distinguish between the immediate deoxygenation process caused by low-oxygen gas replacement and the delayed release process of oxygen retained in the pores of freeze-dried meat particles, avoiding misjudgment based solely on the instantaneous oxygen concentration at the end of the backpressure, and providing a basis for subsequent determination of decompression depth, holding time, and number of repeated deoxygenation cycles.
[0039] The same pressure pulse was applied simultaneously to an empty low-oxygen sealed chamber and a low-oxygen sealed chamber containing non-porous inert particles of the same volume as freeze-dried meat particles. The oxygen concentration changes of the two chambers were used to determine the residual gas replacement baseline and pipeline return baseline. Only the oxygen concentration increase and tailing of the representative sample relative to the two baselines were registered as the pore oxygen release response of the freeze-dried meat particles.
[0040] In practice, three low-oxygen sealed chambers with the same structure, volume and sampling pipeline are used as an empty control chamber, an inert particle control chamber and a representative sample test chamber, respectively. Alternatively, the same sealed chamber can be used to complete three sets of tests in sequence, and the same cleaning and low-oxygen replacement are performed before each set of tests. The inert particles are glass beads, ceramic beads or stainless steel beads, which do not adsorb oxygen on their surface and do not have interconnected pores inside. By adjusting the number of particles, their stacking volume and loading height are made consistent with the freeze-dried meat particle representative sample.
[0041] The same decompression, pressure holding, and low-oxygen backpressure procedures were applied to the three sets of sealed cavities, while maintaining consistent vacuum pipeline length, valve switching sequence, gas flow rate, and oxygen concentration sampling intervals. The oxygen concentration change after backpressure in the empty sealed cavity was used to characterize the displacement baseline caused by dead corners in the cavity wall and residual gas in the cavity. The increase in oxygen concentration change in the inert particle control cavity relative to the empty sealed cavity was used to characterize the backflow baseline caused by gas trapped between particles and backflow during pipeline switching. The oxygen concentration change in the representative sample test cavity at the corresponding time point was calculated by subtracting the displacement baseline and backflow baseline in sequence, and only the portion that continued to rise and formed a tail after subtraction was recorded as the pore oxygen release response.
[0042] This eliminates the interference of residual oxygen in the cavity, interparticle gas, and valve switching backflow on the test results, making the obtained response more accurately reflect the delayed oxygen release characteristics of the interconnected pores inside the freeze-dried meat particles, and reducing the possibility of misjudging equipment disturbances as oxygen retention in pores.
[0043] Based on the time of occurrence after the back pressure ends, the oxygen release response in the pores is divided into a rapid oxygen release segment of 0–10s, a delayed oxygen release segment of 10–45s, and a trailing oxygen release segment after 45s. When the cumulative increase in oxygen concentration in the delayed oxygen release segment or the trailing oxygen release segment accounts for more than 40% of the cumulative increase in oxygen concentration in this batch, the batch of freeze-dried meat particles is marked as a batch with risk of oxygen rebound after packaging.
[0044] In practice, the timing zero point is set at the moment when the low-oxygen gas back pressure ends and the intake valve is closed. Oxygen concentration is continuously collected at sampling intervals of no more than 1 second. The positive increase in oxygen concentration generated after baseline subtraction within 0-10 seconds is assigned to the rapid oxygen release segment, the positive increase within 10-45 seconds is assigned to the delayed oxygen release segment, and the positive increase from 45 seconds to the end of the detection is assigned to the tailing oxygen release segment. The cumulative increase in oxygen concentration for each segment is obtained by sequentially accumulating the oxygen concentration differences that are greater than zero between adjacent sampling points. The newly added cumulative increase in oxygen concentration is the sum of the cumulative increases of the three oxygen release segments to avoid local fluctuations or peak drops offsetting the amount of oxygen already released.
[0045] Calculate the proportion of the cumulative increase in oxygen concentration in the delayed oxygen release stage and the tailing oxygen release stage to the cumulative increase in oxygen concentration in this batch. When either proportion reaches 40% or more, it indicates that more pore oxygen cannot be quickly discharged in the early stage after back pressure and may continue to be released during subsequent standing, mixing or encapsulation processes. Therefore, the corresponding production batch is marked as a batch with risk of oxygen rebound after encapsulation and is prohibited from directly entering the mixing and encapsulation process. Instead, it is transferred to extended pressure holding, increased pressure pulse or standing verification process.
[0046] By segmenting the oxygen release time and using the cumulative increment ratio for judgment, the misjudgment caused by the influence of sensor fluctuations on a single peak can be reduced, and freeze-dried meat particles with low instantaneous oxygen concentration but still showing a continuous oxygen release trend can be identified, thereby reducing the risk of oxygen concentration rebound in the bag after packaging and oxidation of oil-containing puffed particles.
[0047] Among them, incremental differential pressure pulses are applied to batches with oxygen rebound risk after packaging. The minimum pressure of the first pressure pulse is 55-65 kPa, and the minimum pressure of each subsequent pressure pulse is reduced by 5-10 kPa. The next pressure pulse is only started after the tail oxygen release section of the previous pressure pulse has entered a continuous downward state, so as to avoid the oxygen release process of adjacent pressure pulses from overlapping.
[0048] In practice, the freeze-dried meat particles from the batch with the risk of oxygen rebound after packaging are placed in the pulse deoxygenation chamber. First, low-oxygen gas is introduced to restore the pressure inside the chamber to the preset back pressure. Then, the vacuum component is activated to implement the first pressure pulse, which reduces the absolute pressure inside the chamber to 55-65 kPa and holds the pressure for 8-20 seconds. After the pressure returns, the air inlet valve is closed, and the oxygen concentration is continuously collected at intervals of no more than 1 second. When further processing is required, the minimum pressure of subsequent pressure pulses is reduced by 5-10 kPa from the previous one, for example, successively reduced to 60 kPa, 50 kPa, and 40 kPa, thereby gradually increasing the pressure difference inside and outside the pores of the freeze-dried meat particles.
[0049] The controller identifies the peak oxygen concentration and its subsequent tailing changes after each backpressure. When the oxygen concentration is lower than the previous sampling point for 5 to 10 consecutive sampling points and the cumulative decrease is greater than the allowable fluctuation value of the oxygen concentration sensor, it is determined that the tailing oxygen release segment has entered a continuous decreasing state, and then the next pressure pulse can be started. If the oxygen concentration continues to rise, remains in a plateau state, or fluctuates repeatedly, it will continue to be kept sealed and stationary, and the next pressure reduction will not be performed.
[0050] By using incremental pressure differential, easily migratable pore oxygen can be released first, and then gradually applied to deeper or narrower pores, reducing particle breakage and ineffective energy consumption caused by the initial deep decompression. Using the oxygen release of the previous pulse as the starting condition for the next pulse can avoid the overlap of two oxygen release responses, making it easier to accurately judge the deoxygenation effect of each pressure pulse, and reducing the risk of entering the mixing and packaging process before the residual oxygen is fully released.
[0051] When the oxygen concentration rebound is identified, a pressure difference verification pulse with a pressure difference of 50% to 70% of the previous pressure difference is applied. If the oxygen concentration rise in the verification pulse still occurs after the pressure return ends, and no corresponding rise occurs in the empty low oxygen sealed cavity, it is confirmed that the oxygen concentration rebound comes from the connecting pores of the freeze-dried meat particles, rather than from air leakage in the cavity or residual oxygen in the gas supply.
[0052] In practice, the difference between the pressure at the end of the previous pressure pulse and the minimum pressure is taken as the previous pressure differential. When a rebound in oxygen concentration is detected after the end of the back pressure, a verification pulse is applied to the same batch of freeze-dried meat particles after the rebound enters a decreasing state. The verification pulse maintains the low oxygen gas concentration, back pressure end pressure, valve switching sequence, and sampling interval unchanged. By increasing the minimum pressure, the verification pressure differential is made to be 50% to 70% of the previous pressure differential. For example, if the previous pressure differential is reduced from 90 kPa to 40 kPa, the verification pressure differential is set to 25 to 35 kPa, and the minimum pressure is set to 55 to 65 kPa accordingly.
[0053] Simultaneously, the same verification pulse is applied to the empty low-oxygen sealed chamber. Taking the end of the back pressure as the starting point, if the oxygen concentration in the freeze-dried meat particle test chamber rises continuously for 3-5 sampling points after the back pressure ends, and the cumulative increase exceeds the sensor's allowable fluctuation value, while the empty chamber does not show a rise in the same direction during the corresponding period, and the pressure in the test chamber remains stable, it is confirmed that the rebound originates from the connecting pores of the freeze-dried meat particles. If both chambers rise synchronously, it is preferentially determined to be residual oxygen in the gas supply or pipeline backflow; if the oxygen concentration rises while the pressure continues to rise, a chamber sealing check is performed.
[0054] Using a smaller pressure differential for verification allows for the validation of the repeatability of the oxygen release response without repeated strong vacuuming. Furthermore, the use of an unloaded control eliminates interference from equipment and gas sources, thereby reducing the risk of misjudgment and preventing the freeze-dried meat particles from breaking and energy consumption from being erroneously prolonged in the deoxygenation process.
[0055] Among them, the deoxygenation action is selected according to the oxygen release segment with the highest proportion in the pore oxygen release response: when the rapid oxygen release segment has the highest proportion, the instantaneous replacement flow rate of low oxygen gas is increased; when the delayed oxygen release segment has the highest proportion, the freeze-dried meat particles are turned over at low speed and the pressure holding is extended under the lowest pressure; when the tailing oxygen release segment has the highest proportion, two short-term backpressures are used instead of one backpressure, and a no-gas-supply residence period is set between the two backpressures.
[0056] In practice, the cumulative increase in oxygen concentration in the rapid oxygen release stage, the delayed oxygen release stage, and the tailing oxygen release stage is calculated as the proportion of the cumulative increase in oxygen concentration in this instance. The oxygen release stage with the highest proportion is used to determine the deoxygenation action. When the rapid oxygen release stage has the highest proportion, the back pressure termination pressure is kept unchanged, and the opening of the low-oxygen gas valve or the gas supply flow rate is increased to 1.2 to 1.8 times the normal back pressure flow rate to shorten the back pressure time and ensure that the oxygen released near the pore orifice is replaced in time.
[0057] When the delayed oxygen release section accounts for the highest proportion, after the lowest pressure is reached in the cavity, the porous support cylinder is rotated at 1-5 r / min or the freeze-dried meat particles are turned over intermittently. After each turning, the cycle is stopped for 3-10 seconds, and the pressure holding time is extended by 10-30 seconds to change the contact position of the particles and expose the hidden pore channels.
[0058] When the tailing oxygen release section accounts for the highest proportion, the back pressure is split into two short-term back pressures. After the first back pressure reaches 50% to 70% of the target pressure, the gas supply is stopped and maintained for 10 to 30 seconds. Then, the second back pressure is executed to reach the target pressure. Oxygen concentration is continuously collected between the two back pressures to allow oxygen in the deep pores to migrate outwards before being replaced.
[0059] By selecting the corresponding action based on different oxygen release periods, the same deep decompression treatment can be avoided for all batches. Gas replacement, particle rearrangement, or segmented backpressure can be applied to different types of retained oxygen, improving the specificity of deoxygenation and reducing the breakage of freeze-dried meat particles, excessive processing time, and consumption of low-oxygen gas.
[0060] The low-speed turning is achieved by intermittent rotation of the porous support cylinder. Each rotation causes the freeze-dried meat particles to loosen and rearrange once and then stops. The oxygen concentration is collected in the stopped state. When the oxygen concentration rises after rotation but remains stable before rotation, the oxygen amount corresponding to this rise is included in the oxygen retained in the pores blocked by the particle contact surface, and a combination of low-speed turning and pressure holding is added.
[0061] In practice, freeze-dried meat particles are loaded into a porous support cylinder, with the loading volume being 30%–60% of the cylinder's effective volume. The cylinder wall pore diameter is smaller than the minimum external dimensions of the freeze-dried meat particles to allow gas passage and prevent particle leakage. Under minimum pressure, the porous support cylinder is driven to rotate at 1–5 r / min for 5–20 s or rotate 30°–90° before stopping, causing the previously adhered freeze-dried meat particles to separate, reposition, and undergo a loose rearrangement. After stopping rotation, the cylinder is held for 5–30 s, and oxygen concentration is collected at intervals of no more than 1 s to avoid airflow disturbance caused by cylinder movement affecting the detection.
[0062] If the oxygen concentration changes at 5-10 consecutive sampling points before rotation do not exceed the sensor's allowable fluctuation value, it is determined that the system is stable before rotation. If the oxygen concentration increases at 3-5 consecutive sampling points after rotation stops, and the cumulative increase exceeds the allowable fluctuation value, it is determined that new pore oxygen is released after the particle contact surface changes. Based on the positive increase in oxygen concentration, the effective gas volume of the cavity, and the pressure during detection, the corresponding oxygen release is determined, and the pore oxygen trapped by the particle contact surface is included. Then, a combination of low-speed tumbling and pressure holding is added.
[0063] This allows for the proactive exposure of blocked pore openings during stacking, distinguishing between natural tailing oxygen release and oxygen release triggered by particle displacement, reducing the situation where oxygen remains undetected on local contact surfaces before entering the packaging process, and avoiding continuous agitation that could cause freeze-dried meat particles to break and detection signal fluctuations.
[0064] The freeze-dried meat particles are transferred to a low-oxygen buffer zone isolated from the outside environment and left to stand for 60–180 seconds. During the standing period, the supply of low-oxygen gas is stopped. When the oxygen concentration rebounds by more than 0.15 percentage points or the peak exceeds 0.5%, the freeze-dried meat particles are sent back to the pulse deoxygenation chamber through the reflux channel. When the limit is met for two consecutive standing periods, the isolation gate is opened to mix the freeze-dried meat particles with the oil-containing puffed particles on the surface and directly enter the packaging station.
[0065] In practice, after pulse deoxygenation is completed, the transfer channel between the pulse deoxygenation chamber and the low-oxygen buffer is kept in a closed state. The transfer valve is opened to allow the freeze-dried meat particles to enter the low-oxygen buffer under the action of gravity, a closed conveyor belt, or a closed spiral conveyor mechanism. Then the transfer valve is closed to isolate the low-oxygen buffer from the outside world and the pulse deoxygenation chamber. The initial oxygen concentration of the low-oxygen buffer is preferably not higher than 0.5%. After the freeze-dried meat particles enter, the supply of low-oxygen gas is stopped and the buffer is left to stand for 60 to 180 seconds. The oxygen concentration is collected at intervals of no more than 1 second.
[0066] Using the oxygen concentration at the point when gas supply is stopped as a benchmark, the difference between the highest oxygen concentration during the settling period and this benchmark is taken as the oxygen concentration rebound amplitude. When the rebound amplitude exceeds 0.15 percentage points, or the highest oxygen concentration exceeds 0.5%, the mixing side isolation gate is kept closed, and the return channel is opened to send the freeze-dried meat particles back to the pulse deoxygenation chamber for further processing. After deoxygenation is completed again, the settling test is repeated. Only when the rebound amplitude is not greater than 0.15 percentage points and the peak value is not higher than 0.5% after two consecutive settling tests can the isolation gate be opened to allow the freeze-dried meat particles to fall into the oil-containing puffed particles on the surface. After mixing is completed, the particles are directly sent to the packaging station through the closed conveyor channel.
[0067] This static verification can simulate the gas-free environment after freeze-dried meat particles are packaged, and identify the slowly released residual oxygen in advance; using two consecutive qualified tests as release conditions can reduce false releases caused by accidental fluctuations, and direct packaging after mixing reduces the reabsorption of oxygen and oxidation of oil-containing particles.
[0068] An apparatus for delaying the oxidation of pet food, for implementing any of the above-mentioned processes for delaying the oxidation of pet food.
[0069] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.
Claims
1. A process for delaying the oxidation of pet food, characterized in that, include: Before the two types of particles were mixed, representative samples were obtained from freeze-dried meat particles. Pressure reduction, pressure holding and low oxygen gas back pressure were applied sequentially in a low oxygen closed cavity. The pressure change in the cavity was correlated with the rise, peak and fall of oxygen concentration to establish a pore oxygen release response chain. The freeze-dried meat particles to be processed are fed into the pulse deoxygenation chamber, and the pressure is repeatedly reduced and the oxygen is restored by increasing pressure difference. The oxygen concentration rebound process obtained after stopping the gas supply after each restoration is compared with the pore oxygen release response chain. When the oxygen concentration rises again after the gas supply is stopped, and the rising sequence is consistent with the pore oxygen release response chain, it is determined that there is pore retained oxygen, and mixing with oil-containing expanded particles on the surface is prohibited. The corresponding pressure holding stage is extended according to the delay stage of the rebound. When the oxygen concentration rebound after two consecutive pressure pulses is no greater than 0.15 percentage points and the rebound peak is no higher than 0.5%, the mixing restriction is lifted, and the processed freeze-dried meat particles are mixed with the oil-containing puffed particles on the surface in a low-oxygen buffer zone and then packaged.
2. The process for delaying the oxidation of pet food according to claim 1, characterized in that, When establishing the pore oxygen release response chain, the oxygen concentration in the low-oxygen sealed cavity is adjusted to below 1%, reduced from atmospheric pressure to 35-55 kPa and held for 8-20 seconds, and then back-pressurized to 80-95 kPa with a gas with an oxygen concentration not exceeding 0.5%. After the back-pressurization is completed, the inlet valve is closed and held for 30-120 seconds. The oxygen concentration decrease segment during the decompression period, the oxygen concentration rise segment after back-pressurization, and the tail segment after the rise are recorded in the order of occurrence.
3. The process for delaying the oxidation of pet food according to claim 2, characterized in that, The same pressure pulse was applied simultaneously to an empty low-oxygen sealed chamber and a low-oxygen sealed chamber containing non-porous inert particles of the same volume as freeze-dried meat particles. The oxygen concentration changes of the two chambers were used to determine the residual gas replacement baseline and pipeline return baseline. Only the increase and tailing of oxygen concentration in the representative sample relative to the two baselines were recorded as the pore oxygen release response of the freeze-dried meat particles.
4. The process for delaying the oxidation of pet food according to claim 3, characterized in that, Based on the time of occurrence after the back pressure ends, the oxygen release response in the pores is divided into a rapid oxygen release segment of 0–10s, a delayed oxygen release segment of 10–45s, and a trailing oxygen release segment after 45s. When the cumulative increase in oxygen concentration in the delayed oxygen release segment or the trailing oxygen release segment accounts for more than 40% of the cumulative increase in oxygen concentration in this batch, the batch of freeze-dried meat particles is marked as a batch with a risk of oxygen rebound after packaging.
5. The process for delaying the oxidation of pet food according to claim 4, characterized in that, An incremental differential pressure pulse is applied to the batch with the risk of oxygen rebound after packaging. The minimum pressure of the first pressure pulse is 55-65 kPa, and the minimum pressure of each subsequent pressure pulse is reduced by 5-10 kPa. The next pressure pulse is started only after the oxygen release phase of the previous pressure pulse has entered a continuous decreasing state, so as to avoid the oxygen release process of adjacent pressure pulses from overlapping.
6. The process for delaying the oxidation of pet food according to claim 5, characterized in that, Once the oxygen concentration rebound is identified, a pressure differential verification pulse with a pressure difference of 50% to 70% of the previous pressure difference is applied. If the oxygen concentration rise in the verification pulse still occurs after the pressure return ends, and no corresponding rise occurs in the empty low-oxygen sealed cavity, it is confirmed that the oxygen concentration rebound originates from the interconnecting pores of the freeze-dried meat particles, rather than from air leakage in the cavity or residual oxygen in the gas supply.
7. The process for delaying the oxidation of pet food according to claim 6, characterized in that, The deoxygenation action is selected based on the oxygen release segment that accounts for the highest proportion in the pore oxygen release response: when the rapid oxygen release segment accounts for the highest proportion, the instantaneous replacement flow rate of low-oxygen gas is increased; when the delayed oxygen release segment accounts for the highest proportion, the freeze-dried meat particles are turned over at low speed and the pressure holding is extended under the lowest pressure; when the tailing oxygen release segment accounts for the highest proportion, two short-term backpressures are used instead of one backpressure, and a no-gas-supply residence period is set between the two backpressures.
8. The process for delaying the oxidation of pet food according to claim 7, characterized in that, Low-speed turning is achieved by intermittent rotation of the porous support cylinder. Each rotation causes the freeze-dried meat particles to loosen and rearrange once and then stops. Oxygen concentration is collected in the stopped state. When the oxygen concentration rises after rotation but remains stable before rotation, the oxygen amount corresponding to this rise is included in the oxygen retained in the pores blocked by the particle contact surface, and an additional low-speed turning and pressure holding combination action is added.
9. The process for delaying the oxidation of pet food according to claim 8, characterized in that, The freeze-dried meat particles are transferred to a low-oxygen buffer zone isolated from the outside environment and left to stand for 60–180 seconds. During the standing period, the supply of low-oxygen gas is stopped. When the oxygen concentration rebounds by more than 0.15 percentage points or the peak exceeds 0.5%, the freeze-dried meat particles are sent back to the pulse deoxygenation chamber through the reflux channel. When the limit is met for two consecutive standing periods, the isolation gate is opened to mix the freeze-dried meat particles with the oil-containing puffed particles on the surface and directly enter the packaging station.
10. A device for delaying the oxidation of pet food, characterized in that, A process for delaying the oxidation of pet food as described in any one of claims 1-9.