JP2019115308A - Sterilization method of food product - Google Patents

Abstract

To provide a sterilization method having sufficiently high sterilization capability, and executable inexpensively in a short period, which is a sterilization method unaccompanied by heating.SOLUTION: A sterilization method of a food product 1 has a freezing step 12 for freezing a mixture 3 containing a food product 1 and ethanol 2 at -10°C or lower, and a pressing step 13 for holding the frozen mixture 3 at 100-400 MPa, in which an ethanol 2 percentage content in the mixture 3 is 0.08-8 wt%.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method of sterilizing food.

  Food and drink generally cause problems such as food poisoning due to the contamination of harmful microorganisms. In addition, during storage and transportation of products such as food and drink, unintended changes in the flavor and aroma of the product may occur due to the occurrence of unintended fermentation by the producer due to the action of microorganisms. Furthermore, in the case where the product is packaged in a sealed state, the internal pressure of the container is increased by carbon dioxide generated during fermentation, which may lead to breakage of the container. Therefore, in the manufacture of products such as food and drink, a method of killing the microorganisms present in the food and drink and the like, that is, a sterilization method is required.

  As a method of sterilizing microorganisms present in food and drink and the like, a method by heating and a method by food additives having a bactericidal action have been used conventionally. However, these methods may impair or change the flavor and aroma originally possessed by foods and the like. Therefore, sterilization methods without heating and a large amount of additives have been studied.

As such a sterilization method, for example, in JP-A-2-186967 (patent document 1), a pressure of 100 to 10000 kgf / cm ² (that is, 9.81 to 981 MPa) is added to food of 0 ° C. or less. A method of sterilizing food is disclosed. According to the method, the frozen food can be sterilized without thawing the frozen food by heating.

  Japanese Patent Application Laid-Open No. 58-170471 (Patent Document 2) discloses a method of sterilizing brewed liquor by rapid freezing. According to the said method, since microorganisms, such as a blight fungus, can be disinfected without being accompanied by a burning process, it can suppress that the original flavor which brewing liquor has changes.

JP-A-2-186967 Japanese Patent Application Laid-Open No. 58-170471

However, the conventional techniques relating to sterilization involving pressurization have room for improvement in terms of sterilization ability when the pressure applied is relatively low. According to the example disclosed in Patent Document 1, the bactericidal effect at 2500 to 6500 kgf / cm ² (245 to 637 MPa) remains such that the number of viable cells decreases by one to two digits, and its bactericidal activity is insufficient It is.

  In addition, if a method requiring special equipment for pressurization and cryogenic temperature is adopted among the prior art, there is a possibility that the manufacturing cost may increase. For example, the method described in Patent Document 2 exemplifies dry ice-acetone (-70.degree. C.) and liquid nitrogen (-140.degree. C.) as cooling means because it is rapidly frozen. That is, since the special freezing equipment which realizes the cryogenic temperature below -70 ° C is needed when carrying out the method concerned, when the cost required for installing, operating and maintaining the equipment concerned is high There is.

  In view of the above problems, it is desired to realize a sterilization method that does not involve heating, which has a sufficiently high sterilization ability and can be implemented at low cost.

  The method of sterilizing food according to the present invention includes freezing step of freezing a mixture containing food and ethanol at -10 ° C. or lower, and pressurizing step of holding the frozen mixture at 100 to 400 MPa, in the mixture Is characterized in that it has an ethanol content of 0.08 to 8% by weight.

  According to this sterilization method, a sufficiently high sterilization ability can be realized without heating. When the temperature of the freezing step is in the above range, freezing can be carried out using equipment generally used for frozen storage or frozen transportation. That is, no cryogenic equipment is required. Furthermore, because the equipment is common, freezing can be performed simultaneously while storing or transporting the food to be sterilized. Therefore, the new equipment for the freezing step is also efficient both in terms of equipment and period, without requiring a separate period. When the pressure in the pressurizing step is in the above range, the pressure resistance required of the pressure equipment can be made relatively low, and the equipment cost can be reduced.

  Hereinafter, preferred embodiments of the present invention will be described. However, the scope of the present invention is not limited by the examples of preferred embodiments described below.

  In one aspect, it is preferable that the pressurizing step is performed for 10 minutes or less.

  According to this configuration, since the pressurizing step can be performed for a relatively short time, it is possible to reduce the power consumed for maintaining the high pressure and to reduce the cost. In addition, since the time required for the sterilization process can be made relatively short, the manufacturing process can be shortened. Furthermore, it is possible to prevent discoloration and denaturation of the food by holding under high pressure.

  In one embodiment, it is preferred that the pH of the mixture is less than 7.0.

  According to this configuration, the bactericidal effect of the present invention can be further enhanced.

  In one embodiment, the food is suitably fruit juice.

  According to this configuration, the sterilizing method of the present invention can be used as a sterilizing method of the raw material in the manufacturing process of a product using fruit juice as a raw material.

  In one embodiment, the mixture preferably comprises an organic acid.

  According to this configuration, since the bactericidal effect by ethanol and pressure and the bactericidal effect by the organic acid can be used additively, the bactericidal effect of the present invention can be further enhanced.

  In one embodiment, it is preferred that the organic acid is citric acid.

  According to this configuration, the bactericidal effect of the present invention can be further enhanced. In addition, when the food-based product to be sterilized by the sterilization method of the present invention contains citric acid, the citric acid added for sterilization can be used as part of the product, so the citric acid is removed There is no need to provide

  According to the present invention, it is possible to realize a sterilization method which does not involve heating, which has a sufficiently high sterilization ability and which can be implemented at low cost and in a short period of time. According to this sterilizing method, there is no risk of impairing the flavor and aroma originally possessed by food and drink and the like, which contributes to the production of a food having both safety and high quality.

  Further features and advantages of the invention will become more apparent from the following description of exemplary and non-limiting embodiments.

The flow figure showing one embodiment of the sterilization method concerning the present invention.

  Embodiments of the method of sterilizing food according to the present invention will be described in detail with reference to the drawings.

  The following embodiment demonstrates the example which applied the disinfection method of the foodstuff which concerns on this invention to the disinfection of the fruit juice 1 which is an example of the foodstuff used as a raw material of an alcoholic beverage. In the method of sterilizing food according to the present embodiment, as shown in FIG. 1, mixing step 11 in which ethanol 2 is added to fruit juice 1 and mixed, freezing step 12 in which mixture 3 obtained in mixing step 11 is frozen, and freezing And a pressing step 13 of holding the mixture 3 under pressure. The fruit juice 1 sterilized through these steps is sent to the subsequent step (not shown) of producing an alcoholic beverage.

  First, mixing step 11 for obtaining a mixture 3 containing fruit juice 1 and ethanol 2 is performed. Fruit juice 1 contains citric acid and water. As the mixing step 11, a known mixing method can be used. For example, it may be a method of charging the above-mentioned respective materials into a mixing tank provided with a stirring blade and rotating the stirring blade to mix these materials. The contents of ethanol 2 and citric acid contained in the mixture 3 obtained in the mixing step 11 can be controlled by appropriately selecting the amounts of the respective raw materials to be added in the mixing step 11.

  The content of ethanol 2 in the mixture 3 is preferably 0.08 to 8% by weight. When the content of ethanol 2 is in the above range, a good bactericidal effect can be obtained. The content of ethanol 2 is more preferably 0.8 to 8% by weight, and still more preferably 4 to 8% by weight. In addition, since the mixture 3 contains the ethanol 2 and the water which fruit juice 1 contains, it has the property as an ethanol aqueous solution.

  The content of citric acid in the mixture 3 is preferably 0.01 to 10% by weight. When the content of citric acid is in the above range, the bactericidal effect can be further enhanced. The content of citric acid is more preferably 0.1 to 10% by weight, and still more preferably 1 to 10% by weight. At this time, citric acid may be mixed with the fruit juice 1 in the mixing step 11 so that the content of citric acid in the mixture 3 falls within a suitable range. In addition, since it is an additive which brings about a bactericidal effect and is also a raw material of the alcoholic beverage manufactured, it is not necessary to provide the process which removes citric acid.

  The pH of the mixture 3 is preferably less than 7.0, more preferably less than 3.5, and still more preferably less than 2.5. When the pH is within the above range, the bactericidal effect can be further enhanced.

  Next, the freezing step 12 of freezing the mixture 3 obtained by the mixing step 11 is performed. A well-known thing can be used for the cooling installation which concerns on the freezing process 12. FIG. For example, it may be a frozen storage facility or a frozen transportation facility.

  The freezing temperature in the freezing step 12 is preferably −10 ° C. or less. When the freezing temperature is in the above range, a good bactericidal effect can be obtained. The freezing temperature is more preferably −15 ° C. or less. The lower limit of the freezing temperature is not particularly limited, but is preferably −50 ° C. or higher, more preferably −30 ° C. or higher, and still more preferably −25 ° C. or higher. When the freezing temperature is in the above range, freezing is possible at a temperature at which general freezing storage or freezing transportation is performed.

  The duration of the freezing step 12 is not particularly limited as long as it is sufficient to freeze the whole of the mixture 3. For example, the duration of the freezing step 12 may be within 100 hours, more preferably within 70 hours, and even more preferably within 48 hours. Within this range, the time required for the sterilization step can be made short. Also, the duration of the freezing step 12 may be 24 hours or more, and within this range the whole mixture 3 will freeze sufficiently.

  Subsequently, a pressurizing step 13 of holding the frozen mixture 3 under pressure is performed. The pressurizing equipment related to the pressurizing step 13 may be a known one, and may be, for example, a high pressure processing apparatus for food.

  The pressure in the pressurizing step 13 is preferably 100 to 400 MPa. When the pressure is in the above-mentioned range, a sufficient sterilizing effect can be obtained, and the pressure resistance required of the pressure equipment can be made relatively low, so that the equipment cost can be reduced. The pressure is more preferably 100 to 300 MPa, and still more preferably 100 to 200 MPa.

  The duration of the pressurization step 13 is preferably within 10 minutes. When the duration of the pressurizing step 13 is within the above range, the pressurizing step can be made into a short period, so power consumption for maintaining high pressure can be reduced and cost can be reduced. . In addition, since the time required for the sterilization process can be shortened, the manufacturing process can be shortened. Furthermore, it is possible to prevent discoloration and denaturation of the food by holding under high pressure. The duration of the pressurizing step 13 is more preferably 5 minutes or less, further preferably 2 minutes or less.

  Here, in the method of sterilizing food according to the first embodiment, the principle of effective sterilization will be described. In the following description, the case where the content of ethanol 2 in the mixture 3 is 8% by weight will be described as an example.

  Aqueous ethanol solutions have different freezing points depending on their mixing ratio. The mixture 3 in this embodiment contains 8% by weight of ethanol 2, and its freezing point is approximately -10 ° C. At this time, when the mixture 3 is frozen under the environment of freezing temperature -20 ° C (freezing step 12), as the temperature of the mixture 3 decreases, a solid phase in which only water is precipitated and a liquid phase which is a mixture To separate. Since only water precipitates on the solid phase and ethanol 2 does not precipitate and remains in the liquid phase, the ethanol content in the liquid phase increases. Finally, the ethanol content of the liquid phase reaches 16% by weight, which is the ethanol content with a freezing point of −20 ° C. (ie coinciding with the freezing temperature).

  Thus, freezing a mixture containing ethanol at a freezing temperature below the freezing point determined by its ethanol content will increase the ethanol content of the liquid phase. That is, ethanol is concentrated by freezing.

  At this time, in the process of water precipitation, the microorganisms contained in the mixture 3 are extracted in the liquid phase. Therefore, concentrated ethanol 2 and microorganisms are present in the liquid phase, and the microorganisms are sterilized by the bactericidal effect of ethanol 2. By the way, the sterilizing effect by ethanol 2 becomes high, so that the ethanol content rate is high. Therefore, the bactericidal effect in the liquid phase (ethanol content 16% by weight) frozen at -20 ° C. is higher than the bactericidal effect in mixture 3 (ethanol content 8% by weight) before the freezing step 12. In other words, it can be said that a higher bactericidal effect than expected from the amount of ethanol 2 originally contained in the mixture 3 is obtained by freezing.

  The microorganisms targeted for sterilization in the method of sterilizing food according to the present embodiment are not particularly limited, but may be known microorganisms such as yeast, E. coli, staphylococcal bacteria, and lactic acid bacteria.

Other Embodiments
Next, another embodiment of the method of sterilizing food according to the present invention will be described. The configurations disclosed in each of the following embodiments can be applied in combination with the configurations disclosed in the other embodiments as long as no contradiction arises.

  In the above embodiment, the case where the food to be sterilized is fruit juice 1 has been described as an example. However, the food to be sterilized is not limited to fruit juice, and may be, for example, fruits, vegetables, meats, fish and shellfish. At this time, the aspect of the fruit is not particularly limited, and the whole of the fruit, the peel of the fruit, the fruit of the fruit, the one obtained by cutting the fruit, the one obtained by crushing the fruit, or a mixture of two or more selected from these It may be. A known method can be used as a method of grinding the fruit, but freeze grinding is preferable.

  In the above embodiment, the food to be sterilized is fruit juice 1, ie, the case where the food contains citric acid has been described as an example. However, the food to be sterilized may not contain an organic acid. Regardless of whether or not the food contains an organic acid, the organic acid may be mixed with the food in the mixing step such that the content of the organic acid in the mixture falls within a preferred range.

  In the above embodiment, the case where the mixture 3 contains fruit juice 1 and ethanol 2 and the fruit juice 1 contains citric acid has been described as an example. However, the organic acid is not limited to citric acid, and may be an organic acid selected from the group consisting of citric acid, malic acid, fumaric acid, tartaric acid, benzoic acid, lactic acid and ascorbic acid, and a mixture of plural organic acids It may be The mixture may or may not further contain other optional ingredients such as sugar, preservatives, antioxidants and pH adjusters. In addition, water may be added to each of the components described above to adjust the concentration of the components in the mixture.

  In the above embodiment, the case where the mixture 3 is obtained by the mixing step 11 which is a known mixing method has been described as an example. However, the mixture does not necessarily have to be obtained by the mixing process. For example, brewing a mixture containing sugar may be used as a mixture as it results in a brewed product in which a portion of the sugar is converted to ethanol.

  With regard to the other configurations, it is to be understood that the embodiments disclosed herein are illustrative in all respects, and the scope of the present invention is not limited by them. Those skilled in the art will easily understand that appropriate modifications can be made without departing from the spirit of the present invention. Therefore, other embodiments modified within the scope of the present invention are naturally included in the scope of the present invention.

  EXAMPLES The present invention will be described by way of examples, but the present invention is not limited to the following examples.

[Test bacteria]
In the tests shown in the following examples, as test bacteria, yeasts which were detected from plants in the past and were stored in the L dried state were used.

〔reagent〕
The following reagents were used in the tests shown in the following examples.
Ethanol: Nacalai Tesque, Inc., Grade EP, Purity 99.5
Citric acid: Nacalai Tesque, Inc., grade EP, purity 9 99.0
Buffer solution (pH 3.5): manufactured by Nacalai Tesque, Inc., prepared with citric acid and sodium dihydrogen phosphate, concentration 0.13 M
Buffer solution (pH 7.0): manufactured by Nacalai Tesque, Inc., prepared with citric acid and sodium dihydrogen phosphate, concentration 0.18 M

[Fruit juice]
Commercially available grapefruit was directly squeezed with a super hand juicer TW-001 to obtain a grapefruit juice having a pH of 3.3.

[Inoculation step]
9.9 mL of a sample solution (alone or mixed) was collected, 0.1 mL of a test strain adjusted to 10 ⁹ cells / mL was added, and uniformly mixed to obtain an inoculum.

[Freezing process]
10 mL of the inoculating solution was held for 72 hours in a refrigerator storage facility (manufactured by Hoshizaki, commercial refrigerator-freezer) in which the temperature in the refrigerator was kept at -20. +-. 4.degree. C. to obtain a frozen sample.

[Refrigeration process]
10 mL of the inoculum was held for 72 hours in a refrigerator storage facility (manufactured by Hoshizaki, commercial refrigerator-freezer) in which the temperature inside the refrigerator was kept at 4 ± 1 ° C. to obtain a refrigerated sample.

[Pressing process]
Hold 10 mL of frozen sample or refrigerated sample for 10 minutes in the storage of pressure equipment (Kobe Steel Co., Ltd., high pressure processing equipment for research and development) maintained at 10 ° C and the environment in the storage for 10 minutes, and measure the sample Obtained.

[Thawing process]
10 mL of the frozen sample was kept at atmospheric pressure and room temperature 25 ° C. for 30 minutes to obtain a measurement sample.

Viable count analysis
0.1 mL of a measurement sample was collected and diluted with sterile water to obtain a diluted sample. Using a sterile pipette, 0.1 mL of the diluted sample was solidified and evenly spread on a surface of the dried agar medium with a Conlage bar. The culture was carried out for 96 hours in an incubator maintained at 35 ° C.
For the culture medium, the number of colonies formed was measured, and the obtained measurement value was multiplied by the dilution factor at the time of sample preparation to calculate the number N of bacteria per 1 mL of the measurement sample. Assuming that the number of bacteria per 1 mL of the sample measured by the same method for the sample before the sterilization step was N ₀ , the logarithmic reduction value LRV (D) of the number of bacteria after the sterilization step was calculated according to the following formula (I).
LRV (D) = Log ₁₀ (N ₀ / N) (I)

Example 1
8.9 mL of grapefruit juice (pH 3.3) was uniformly mixed with 1.0 mL of ethanol to obtain a mixture containing 8% by weight of ethanol. The said inoculation step, the said freezing process, and the said pressurization process were implemented in order with respect to the said mixture, and the measurement sample was obtained. With respect to the measurement sample, viable count analysis was performed by the method described above to obtain LRV (D) value.

Example 2
8.9 mL of buffer solution (pH 3.5) and 1.0 mL of ethanol were mixed uniformly to obtain a mixture containing 8% by weight of ethanol and 4.7% by weight of citric acid. The said inoculation step, the said freezing process, and the said pressurization process were implemented in order with respect to the said mixture, and the measurement sample was obtained. With respect to the measurement sample, viable count analysis was performed by the method described above to obtain LRV (D) value.

[Example 3]
8.9 mL of buffer solution (pH 7.0) and 1.0 mL of ethanol were mixed uniformly to obtain a mixture containing 8% by weight of ethanol and 1.2% by weight of citric acid. The said inoculation step, the said freezing process, and the said pressurization process were implemented in order with respect to the said mixture, and the measurement sample was obtained. With respect to the measurement sample, viable count analysis was performed by the method described above to obtain LRV (D) value.

Comparative Example 1-1
The said inoculation step, the said freezing step, and the said pressurization process were implemented in order with respect to 10 mL of grapefruit juice (pH 3.3), and the measurement sample was obtained. With respect to the measurement sample, viable count analysis was performed by the method described above to obtain LRV (D) value.

Comparative Example 1-2
In Example 1, the thawing step was performed instead of the pressing step, and a measurement sample not subjected to the pressing step was obtained. With respect to the measurement sample, viable count analysis was performed by the method described above to obtain LRV (D) value.

Comparative Example 1-3
In Example 1, it replaced with the said freezing process and implemented the said refrigeration process, and obtained the measurement sample which does not pass through the freezing process. With respect to the measurement sample, viable count analysis was performed by the method described above to obtain LRV (D) value.

Comparative Example 1-4
In the comparative example 1, it changed to the said pressurization process and implemented the said thawing | decompression process, and the measurement sample which did not pass through the pressurization process was obtained. With respect to the measurement sample, viable count analysis was performed by the method described above to obtain LRV (D) value.

[Comparative Example 1-5]
In the comparative example 1, it replaced with the said freezing process and implemented the said refrigeration process, and the measurement sample which did not pass a freezing process was obtained. With respect to the measurement sample, viable count analysis was performed by the method described above to obtain LRV (D) value.

Comparative Example 2-1
The said inoculation step, the said freezing step, and the said pressurization process were implemented in order with respect to 10 mL of buffer solutions (pH 3.5) which is an aqueous solution containing 5.3 weight% of citric acid, and the measurement sample was obtained. With respect to the measurement sample, viable count analysis was performed by the method described above to obtain LRV (D) value.
Comparative Example 2-2
In Example 2, the thawing step was performed instead of the pressing step, and a measurement sample not subjected to the pressing step was obtained. With respect to the measurement sample, viable count analysis was performed by the method described above to obtain LRV (D) value.

[Comparative example 2-3]
In Example 2, it replaced with the said freezing process and implemented the said refrigeration process, and the measurement sample which did not pass through the freezing process was obtained. With respect to the measurement sample, viable count analysis was performed by the method described above to obtain LRV (D) value.

Comparative Example 2-4
In Comparative Example 2-1, the thawing step was performed instead of the pressing step, and a measurement sample not subjected to the pressing step was obtained. With respect to the measurement sample, viable count analysis was performed by the method described above to obtain LRV (D) value.

[Comparative Example 2-5]
In the comparative example 2-1, it replaced with the said freezing process and implemented the said refrigeration process, and the measurement sample which did not pass a freezing process was obtained. With respect to the measurement sample, viable count analysis was performed by the method described above to obtain LRV (D) value.

Comparative Example 3-1
The said inoculation step, the said freezing step, and the said pressurization process were implemented in order with respect to 10 mL of buffer solutions (pH 7.0) which is an aqueous solution containing 1.3 weight% of citric acid, and the measurement sample was obtained. With respect to the measurement sample, viable count analysis was performed by the method described above to obtain LRV (D) value.

Comparative Example 3-2
In Example 3, the thawing step was performed instead of the pressing step, and a measurement sample not subjected to the pressing step was obtained. With respect to the measurement sample, viable count analysis was performed by the method described above to obtain LRV (D) value.

Comparative Example 3-3
In Example 3, it replaced with the said freezing process and implemented the said refrigeration process, and the measurement sample which did not pass a freezing process was obtained. With respect to the measurement sample, viable count analysis was performed by the method described above to obtain LRV (D) value.

Comparative Example 3-4
In Comparative Example 3-1, the thawing step was performed instead of the pressing step, and a measurement sample not subjected to the pressing step was obtained. With respect to the measurement sample, viable count analysis was performed by the method described above to obtain LRV (D) value.

[Comparative Example 3-5]
In Comparative Example 3-1, the refrigeration step was performed instead of the freezing step to obtain a measurement sample not subjected to the freezing step. With respect to the measurement sample, viable count analysis was performed by the method described above to obtain LRV (D) value.

[Bactericidal effect in grapefruit juice]
The results of Example 1 and Comparative Examples 1-1 to 1-5 are shown in Table 1. Example 1 which added ethanol and implemented a freezing process and a pressurization process showed the highest bactericidal effect.

[Bactericidal effect in buffer solution]
The results of Examples 2 and 3 and Comparative Examples 2-1 to 2-5 and 3-1 to 3-5 are shown in Table 2. Examples 2 and 3 in which ethanol was added and the freezing step and the pressing step were performed showed high bactericidal effects.

The present invention can be used, for example, to sterilize juice used as a raw material of liquors and soft drinks.

Claims (6)

Freezing the mixture containing food and ethanol below -10 ° C .;
Holding the frozen mixture at 100 to 400 MPa;
The ethanol content in the mixture is 0.08 to 8% by weight.   The method of sterilizing food according to claim 1, wherein the pressurizing step is performed for 10 minutes or less.   The method according to claim 1 or 2, wherein the pH of the mixture is less than 7.0.   The method for sterilizing a food according to any one of claims 1 to 3, wherein the food is fruit juice.   The method for sterilizing a food according to any one of claims 1 to 4, wherein the mixture contains an organic acid. The method for sterilizing food according to claim 5, wherein the organic acid is citric acid.

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