JP7694192B2 - Packaging method - Google Patents

Description

The present invention relates to a packaging method.

So far, so-called gas replacement packaging has been known, in which the air in a packaging container is replaced with an inert gas such as nitrogen while the contents are filled and sealed in order to prevent deterioration of the contents due to oxidation and deterioration of quality due to the proliferation of aerobic bacteria, and to enable long-term storage. Regarding gas replacement packaging, JIS Z 0108:2012 states, "When filling the contents, air is sucked out from the container and replaced with an inert gas such as nitrogen or carbon dioxide before sealing, or the air in the container is forcibly replaced with an inert gas and sealed, with the aim of preventing deterioration of the product. The container is made of a packaging material with excellent gas barrier properties" (No.: 1079).

In addition, since it is difficult to completely remove oxygen from within the container in this type of gas replacement packaging, for example, Patent Document 1 proposes that the contents be gas replacement packaged in a packaging container made of a laminate that has an oxygen barrier layer and a resin layer that has an oxygen absorbing function.

Japanese Patent Application Publication No. 8-133345

However, according to the inventors' research, even when the contents are gas-exchanged packaged in a packaging container with oxygen absorbing function, the oxygen concentration in the container increases after gas-exchange packaging. After extensive research focusing on this point, the inventors found that the oxygen contained in the contents had an effect. Therefore, the inventors conducted further extensive research to reduce the amount of oxygen remaining in the container after gas-exchange packaging by removing as much oxygen as possible from the contents, which had not been taken into consideration at all in the past, and as a result, they completed the present invention.

The packaging method of the present invention is a method for gas-flux packaging of contents in a packaging container, comprising the steps of: placing the contents in a vacuum chamber and sealing it; evacuating the vacuum chamber to reduce the pressure inside the vacuum chamber to a first reduced pressure; then, while continuing the exhaust, flowing an inert gas into the vacuum chamber; thereafter, while continuing the exhaust, stopping the flow of inert gas into the vacuum chamber and further reducing the pressure inside the vacuum chamber to a second reduced pressure; then, stopping the exhaust of the vacuum chamber and flowing inert gas into the vacuum chamber again to make the pressure inside the vacuum chamber equivalent to atmospheric pressure; and then removing the contents from the vacuum chamber and performing gas-flux packaging.

According to the present invention, by efficiently removing oxygen from the contents prior to gas-exchange packaging the contents in a packaging container, it is possible to further reduce the amount of oxygen remaining in the container after gas-exchange packaging.

The packaging method according to the present invention will be described below with reference to an embodiment.

The packaging method shown as an embodiment of the present invention is a packaging method that efficiently removes oxygen from the contents before gas-exchange packaging the contents in a packaging container, thereby further reducing the amount of oxygen remaining in the container after gas-exchange packaging, allowing the contents to be stored for a longer period of time.

In this embodiment, typical examples of the contents to be packaged include food items such as buns, rolls, steamed bread, monaka, and rice crackers, but are not limited to these. Non-food items whose preservation may be adversely affected by oxygen remaining in the container can also be packaged.

In this embodiment, the contents to be packaged are first placed under atmospheric pressure in a reduced pressure chamber connected to a vacuum pump. When placing the contents to be packaged in the reduced pressure chamber, the contents may be placed together or individually depending on the size of the contents and the volume of the reduced pressure chamber.

Then, the vacuum chamber is closed, the contents are sealed inside the vacuum chamber, and the vacuum pump is operated to evacuate the inside of the vacuum chamber. Then, when the pressure inside the vacuum chamber has been reduced to the first degree of vacuum, an inert gas is introduced into the vacuum chamber while continuing to evacuate.

The inert gas is not particularly limited as long as it is chemically inert to the contents, but for example, at least one inert gas selected from the group consisting of nitrogen, carbon dioxide, argon, and helium can be used.

In this way, by flowing inert gas into the reduced pressure chamber, the atmosphere surrounding the contents is replaced with inert gas, and a difference in the partial pressure of oxygen gas occurs between the inside of the contents and the outer periphery of the contents. As a result, the oxygen contained inside the contents is effectively diffused and released into the atmosphere around the contents, where the oxygen gas partial pressure is relatively low. Moreover, because gas is continuously evacuated from inside the chamber, the oxygen diffused and released to the outer periphery of the contents is effectively discharged outside the reduced pressure chamber.

When a vacuum pump connected to a vacuum chamber is operated to evacuate the inside of the vacuum chamber, the exhaust speed of the vacuum pump is generally fast when the degree of vacuum inside the vacuum chamber is low, and the exhaust speed gradually slows down as the degree of vacuum inside the vacuum chamber increases. For this reason, if you try to replace the outer periphery of the contents with an inert gas when the degree of vacuum is low, it is necessary to increase the amount of inert gas flowing in. In order to flow an amount of inert gas into the vacuum chamber that matches the exhaust speed of the vacuum pump while preventing large fluctuations in the degree of vacuum inside the vacuum chamber, not only is it complicated to adjust the flow rate, but it also results in more inert gas than necessary being flowed in, which is cost-inefficient.

On the other hand, when gas replacement is performed at a high degree of reduced pressure, the efficiency of removing oxygen contained in the contents tends to decrease. This is thought to be because the inflowing inert gas is given priority for being discharged outside the reduced pressure chamber before the oxygen contained inside the contents diffuses and is released into the surrounding inert gas atmosphere. Furthermore, continuing gas replacement around the periphery of the contents at a high degree of reduced pressure also promotes the removal of components that affect the flavor and quality of the contents, such as moisture and flavor components that are inherent to the contents, which may lead to a deterioration in the quality of the contents.

Taking these factors into consideration, the primary pressure reduction degree, in terms of absolute pressure, is preferably 20 kPa to 80 kPa, and more preferably 30 kPa to 70 kPa, as a condition for selectively removing oxygen remaining inside the contents.

The exhaust speed V1 [L/min] for exhausting the inside of the reduced pressure chamber varies depending on the performance of the vacuum pump (exhaust speed at standard atmospheric pressure, achieved vacuum) and the volume of the reduced pressure chamber, and the inflow speed V2 [L/min] for introducing the inert gas into the reduced pressure chamber is also determined in relation to the exhaust speed V1 for exhausting the inside of the reduced pressure chamber.

In this embodiment, after the pressure inside the vacuum chamber is reduced to the primary reduced pressure, the inert gas is introduced into the vacuum chamber while continuing to evacuate. The degree of reduced pressure (absolute pressure) inside the vacuum chamber is measured with a vacuum gauge, and the inlet speed of the inert gas (inlet speed of the inert gas under the primary reduced pressure) V2 can be adjusted while monitoring the fluctuation. In this case, if V1=V2, the degree of reduced pressure inside the vacuum chamber remains constant. If V1>V2, the degree of reduced pressure inside the vacuum chamber increases, and if V1<V2, the degree of reduced pressure inside the vacuum chamber decreases. In any case, it is preferable to adjust the inert gas inlet speed V2 under the primary reduced pressure so that the fluctuation of the degree of reduced pressure inside the vacuum chamber falls within the aforementioned range specified for the primary reduced pressure, that is, preferably within the range of 20 kPa to 80 kPa, more preferably 30 kPa to 70 kPa in absolute pressure.

When inert gas is introduced into the vacuum chamber, the inflow time (inert gas inflow time under the primary reduced pressure) is preferably 5 to 1200 seconds, and more preferably 10 to 600 seconds. If the inert gas inflow time under the primary reduced pressure is short, such as less than 5 seconds, the gas surrounding the contents may not be sufficiently replaced with inert gas, and the efficiency of removing oxygen contained in the contents may decrease. On the other hand, if the inert gas inflow time under the primary reduced pressure is longer than 1200 seconds, the removal of moisture and flavor components from the contents may be accelerated, resulting in a deterioration in the quality of the contents.

In this way, by reducing the pressure inside the vacuum chamber appropriately and replacing the gas around the outer periphery of the contents with an inert gas, it is possible to selectively remove the oxygen contained in the contents without impairing the flavor of the contents. However, since oxygen is also adsorbed or sorbed on the inner walls of the vacuum chamber device, which are made of metal, it is also necessary to remove the oxygen adsorbed or sorbed on the inner walls of the vacuum chamber device. This is because there is a risk that the oxygen adsorbed or sorbed on the inner walls of the vacuum chamber device will be released in a subsequent process and transferred to the contents.

In this embodiment, in order to effectively avoid such a problem, after the inert gas flow into the vacuum chamber is stopped at the first vacuum level, the vacuum chamber is continuously evacuated until the vacuum level in the vacuum chamber reaches a second vacuum level with a higher vacuum level. This exhaust increases the vacuum level in the vacuum chamber to a higher vacuum level, and promotes the release and removal of oxygen adsorbed or sorbed on the inner wall of the vacuum chamber from the inner wall of the vacuum device. As a result, oxygen adsorbed or sorbed on the inner wall of the vacuum chamber can be discharged to the outside of the vacuum chamber, which promotes the removal of oxygen that may migrate to the contents.

The degree of secondary vacuum can be set appropriately according to the performance of the vacuum pump, so long as it does not impair the appearance of the contents or promote the removal of moisture and flavor components from the contents. For example, the degree of secondary vacuum is preferably 0.1 kPa to 10 kPa, and more preferably 1 kPa to 8 kPa, in absolute pressure.

After the degree of vacuum in the vacuum chamber reaches the second degree of vacuum, exhausting the vacuum chamber is stopped and the inert gas is again introduced into the vacuum chamber to restore the pressure in the vacuum chamber to atmospheric pressure. At this time, the flow rate of the inert gas into the vacuum chamber is not particularly limited, as long as the contents in the vacuum chamber are not deformed, disintegrated, or scattered by the inflow of the inert gas, resulting in a loss of appearance or quality of the contents. Alternatively, the pressure in the vacuum chamber may be returned to atmospheric pressure by opening the vacuum chamber under an inert gas atmosphere.

After the pressure inside the vacuum chamber is made equal to atmospheric pressure, an inert gas can be introduced into the vacuum chamber to raise the pressure inside the vacuum chamber above atmospheric pressure. In this case, the oxygen remaining in the contents is further replaced with the inert gas, and it is expected that more oxygen can be removed from the contents. However, it goes without saying that the pressure inside the vacuum chamber is reduced to equal to atmospheric pressure before the contents are removed.

The contents are then removed from the vacuum chamber and packaged in gas replacement packaging. As the packaging container used for gas replacement packaging, it is preferable to use a known packaging container that has been given an oxygen absorbing function so that the oxygen remaining in the container can be absorbed, but it is also possible to enclose a known oxygen absorber in the container without using such a packaging container so that the oxygen remaining in the container can be absorbed.

According to this embodiment, by efficiently removing oxygen from the contents before packaging the contents in a packaging container with gas replacement, even when the contents to be packaged are bulky and contain a large amount of oxygen, the amount of oxygen released from the contents and remaining in the container can be reduced, and the oxygen can be sufficiently absorbed by the oxygen absorption function provided to the packaging container or the oxygen absorbing material enclosed in the container, allowing the contents to be preserved for a longer period of time.

The present invention will be explained in more detail below with specific examples.

[Examples 1 to 7, Comparative Examples 1 to 7]
A vacuum pump with a volume of 70 L was connected to the vacuum chamber, which had an exhaust speed of 200 L/min under standard atmospheric pressure and an ultimate vacuum of 0.067 Pa. One bun weighing 50 g was placed in the vacuum chamber, and the vacuum chamber was sealed, and then the inside of the vacuum chamber was evacuated.

When the pressure in the vacuum chamber was reduced to the first reduced pressure, nitrogen gas was allowed to flow into the vacuum chamber at an inflow rate V2 and for an inflow time T while continuing evacuation.
Tables 1 and 2 show the primary reduced pressure, the inflow velocity V2, the inflow time T, and whether the inflow of the inert gas under the primary reduced pressure was stable or unstable.

Thereafter, evacuation was continued until the pressure in the vacuum chamber was reduced to the secondary vacuum level, and after evacuation was stopped, nitrogen gas was allowed to flow into the vacuum chamber at the same inflow rate as the inert gas in the primary vacuum level, thereby restoring the pressure in the vacuum chamber to the same level as atmospheric pressure.
The degree of secondary pressure reduction at this time is shown in Tables 1 and 2.
In Comparative Example 7, the pressure in the vacuum chamber was restored to the same level as atmospheric pressure without reducing the pressure to the second reduced pressure level.

After the pressure inside the vacuum chamber was restored to atmospheric pressure with nitrogen gas, the buns were removed from the vacuum chamber under a nitrogen gas atmosphere and gas-replaced packaging was performed with nitrogen gas (pillow packaging using an oxygen-absorbing film (Oxydec (registered trademark) manufactured by Toyo Seikan Co., Ltd.)).
In Comparative Example 1, only the gas replacement packaging with nitrogen gas was performed, and no operation for removing oxygen from the contents was performed.

The head space in the container after the gas replacement packaging was 82 mL. The oxygen concentration in the container immediately after the gas replacement packaging and the oxygen concentration in the container after storage at 5° C. for 24 hours are shown in Tables 1 and 2.
The oxygen concentration was measured using an oxygen concentration meter (LC-750F) manufactured by Toray Engineering.

In addition, the appearance of the contents after the gas replacement packaging and the flavor of the contents after storage at 5° C. for 24 hours were evaluated according to the following criteria.
[Evaluation Criteria]
⊚: All five evaluators rated it as acceptable.
Good: Three or more of the five evaluators rated it as good.
×: Two or less of the five evaluators rated it as "pass."
The evaluation results are shown in Tables 1 and 2.

The present invention has been described above with reference to preferred embodiments, but it goes without saying that the present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the present invention.

Claims (7)

When packaging the contents in a packaging container,
The contents are placed in a vacuum chamber and sealed;
The inside of the decompression chamber is evacuated to reduce the pressure inside the decompression chamber to a first decompression level, and then an inert gas is introduced into the decompression chamber while continuing the evacuation;
Thereafter, while continuing the evacuation, the inlet of the inert gas into the vacuum chamber is stopped, and the pressure in the vacuum chamber is further reduced to a second reduced pressure;
Next, the exhaust of the vacuum chamber is stopped, and the inert gas is again introduced into the vacuum chamber to make the pressure in the vacuum chamber equal to atmospheric pressure. Thereafter, the contents are removed from the vacuum chamber and gas replacement packaging is performed. The packaging method according to claim 1, wherein the primary reduced pressure is 20 kPa to 80 kPa absolute. The packaging method according to claim 2, in which, after the pressure inside the vacuum chamber is reduced to the first reduced pressure, the inert gas is introduced into the vacuum chamber while continuing to evacuate, and the inlet rate of the inert gas is adjusted so that the fluctuation in the reduced pressure inside the vacuum chamber is within the range of 20 kPa to 80 kPa absolute pressure. The packaging method according to any one of claims 1 to 3, wherein after the pressure inside the vacuum chamber is reduced to the first reduced pressure, the inert gas is introduced into the vacuum chamber while continuing to evacuate, and the inert gas is introduced for a period of time ranging from 5 seconds to 1200 seconds. The packaging method according to any one of claims 1 to 4, wherein the degree of secondary reduced pressure is 0.1 kPa to 10 kPa in absolute pressure. The packaging method according to any one of claims 1 to 4, wherein the degree of secondary reduced pressure is 1 kPa to 8 kPa in absolute pressure. The packaging method according to any one of claims 1 to 6, wherein the inert gas is at least one selected from the group consisting of nitrogen, carbon dioxide, argon and helium.