JP2002191334A - Food sterilization method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a food sterilization method capable of killing highly pressure-resistant sporaceous bacteria universally existing in foods such as Bacillus subtilis to a level of causing no putrefaction to foods under their normal-temperature distribution. SOLUTION: This food sterilization method comprises the preheating step of heating a food (5) to >=50 deg.C and the step of pressurizing thus preheated food (5) under a pressure of >=300 MPa, wherein the food (5) is pressurized in a condition of containing it in a thermally insulated vessel (4).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for sterilizing food.

[0002]

2. Description of the Related Art Conventionally, a method of applying an ultra-high pressure to food to sterilize it (ultra-high pressure sterilization method) is known. For example, International Publication WO97 / 21361 states that low acid foods are canned, heated to 80 to 99 ° C., and then 50,000 to 15 ° C.
0000 psi (about 340 MPa to about 1020 MPa)
For heating at an ultrahigh pressure. Japanese Patent Application Laid-Open No. 2000-83633 discloses that a low-acid food having a pH of 4.5 or more is preheated to about 70 ° C.
A method of applying pressure at an ultrahigh pressure of 0 MPa or more is disclosed. According to these methods, sterilization is performed instantaneously by applying an ultra-high pressure, so that a change in fine aroma and texture of food can be remarkably suppressed.

[0003] However, these food sterilization methods are:
Weakly resistant spores, such as Clostridium sporogene
s or Bacillus cereus is effective in disinfecting, but is widely present in foods and greatly contributes to the spoilage of foods, and is a highly pressure-resistant spore bacterium, such as Bacillus subtilis. It is very difficult to sterilize to a level that does not cause spoilage. In addition, the sterilization effect may be uneven (sterilization unevenness) depending on the location in the processing pressure vessel.

[0004]

SUMMARY OF THE INVENTION Accordingly, the present invention has been made in view of the above-mentioned problems of the prior art, and has a high pressure-resistant spore bacterium commonly present in foods, such as Bacillus subti.
An object of the present invention is to provide a food sterilization method capable of sterilizing lis under a normal temperature distribution to a level at which food does not spoil.

[0005]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that the above-mentioned problems can be solved by the following means. That is, the present invention includes a preheating step of heating the food 5 to a temperature of 50 ° C. or higher, and a pressurizing step of pressurizing the preheated food 5 at a pressure of 300 MPa or higher. And a food sterilization method in which pressurization is performed in a state where the food is stored in the food container. The present invention also relates to a food 5
A preheating step of heating the preheated food 5 to a temperature of 50 ° C. or more, a pressurizing step of pressurizing the preheated food 5 with a pressure of 300 MPa or more, a pause step of releasing the pressurization, and a further 300MPa.
a pressurizing step of pressurizing at a pressure equal to or higher than a, and pressurizing the food 5 in a state where the food 5 is stored in the heat insulating container 4. Furthermore, the present invention provides a food sterilization method in which the pressurized medium 6 inside the pressurized tank 2 and the inside of the heat insulating container 4 is oil when the food 5 is pressurized.

[0006] The food sterilizing method according to the present invention includes a preheating step and a pressurizing step, and pressurizes the food 5 in a state of being stored in the heat insulating container 4. Spores having a high pressure resistance such as Bacillus subtilis can be sterilized to a level that does not spoil food even under a long-term normal temperature distribution. In addition, the food sterilization method according to the present invention includes a pause step of loosening the pressurization during the pressurization step, and pressurizes while the food 5 is stored in the heat insulating container 4.
Sterilization unevenness depending on the position inside the sterilization apparatus 1 can be further reduced. Furthermore, in the food sterilization method according to the present invention, since the pressurized medium 6 inside the pressurized tank 2 and the inside of the heat insulating container 4 is oil, the preheating temperature can be reduced.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. -First embodiment The first embodiment is a preheating step of heating the food 5 to a temperature of 50 ° C. or more, and the preheated food 5 is heated to 300 MPa.
And a pressurizing step of pressurizing with the above-mentioned pressure.
Is pressurized in a state where is stored in the heat insulating container 4.

As shown in FIG. 1, a sterilizing apparatus 1 used in the food sterilizing method according to the present invention has a box-shaped metal pressurizing tank 2 having an open upper surface, and an opening of the pressurizing tank 2. A pressurizing piston 3 made of metal that can block the portion and push the pressurizing tank 2 toward the inside. Then, at the time of pressurization, the heat insulating container 4 filled with the food 5 to be sterilized and the pressurized medium 6 was put into the pressurized tank 2, and the pressurized tank 2 was further filled with the pressurized medium 6. Used in state. Less than,
The steps will be described in the order of the food sterilization method.

(Preliminary heating step) The food 5 to be sterilized is heated before being sterilized by pressure. The temperature at which the food 5 is heated (preliminary heating temperature) is not particularly limited as long as it is 50 ° C. or higher.
In the case of distributing the food after sterilization at room temperature, the temperature is preferably 70 ° C. or more, and particularly preferably 70 to 100 ° C., from the viewpoint of the quality of the food and commercial sterilization of the food. In addition, when the food is chilled, the temperature is usually 50 ° C. or higher, but is preferably 60 ° C. or higher, and particularly preferably 60 ° C. to 100 ° C., from the same viewpoint as in the case of normal temperature distribution. Note that the heating time is preferably determined by measuring heat transfer. The method of heating is not particularly limited, but a method of placing the food 5 in an environment heated to a temperature equal to or higher than the preheating temperature, for example, placing the food 5 inside a heated water bath is used. Can be

Further, from the viewpoint that the cost required for sterilization can be reduced by efficiently using heat (energy),
A method of performing preheating using the reduced heat insulating container 4, that is, putting the food 5 inside the heat insulating container 4, further closing the heat insulating container 4 with the inside of the heat insulating container 4 filled with the pressure medium 6, Can be used to heat the whole to the preheating temperature. The heat-insulating container 4 is formed in a shape that can accommodate the food 5 with a resin having heat-insulating properties. Specifically, such a resin is not particularly limited as long as it has a heat insulating property. For example, a polyethylene resin, a polybutylene terephthalate resin, a Teflon (registered trademark) resin, a fluororesin, or the like is used.
The thermal conductivity of the resin is preferably 1 W / m · ° C. or less, and the thickness of the heat-insulating container 4 (the thickness of the resin forming the heat-insulating container 4) can be reduced. From the viewpoint that pressure sterilization becomes possible, 0.5
W / m · ° C. or lower is more preferable. Furthermore, by blending a plurality of resins having a heat insulating property, laminating a plurality of resins having a heat insulating property, laminating a resin having a heat insulating property and a metal or other resin having no heat insulating property. In addition, the heat insulating property of the heat insulating container 4 can be compatible with the ease of molding processing, the stability of the shape, and the like. Further, the shape of the heat insulating container 4 can be opened / closed and has a shape such as a bag shape / tubular shape / container shape capable of accommodating the food 5, that is, the food 5 is formed into a general pouch bag or the like. Insulated container 4 in stored state
It is formed in a shape that can be housed inside and further sealed or covered. Furthermore, it is desirable that the shape of the heat insulating container 4 be substantially similar to the shape of the inside of the pressurized tank 2 in order to improve productivity. The pressure medium 6 is not particularly limited as long as it is a liquid such as water or oil. For example, oil such as salad oil is preferably used from the viewpoint that the preheating temperature can be reduced. Here, salad oil refers to edible rapeseed oil, edible soybean oil, and a mixture thereof.

(Pressurizing Step) Next, the preheated food 5 is pressurized under an ultra-high pressure and sterilized. Specifically, in the pre-heating step, when the food 5 is put in a pouch bag or the like and is not put in the heat insulating container 4, first, the pre-heated food 5 is put in a pouch bag, and 4, the heat insulating container 4 is filled with the pressure medium 6, and the heat insulating container 4 is closed. Then, the heat-insulating container 4 containing the food 5 is put into the inside of the pressurized tank 2, and the pressurized tank 2 is filled with the pressurized medium 6. Then, the food 3 is pressurized by pushing the piston 3 toward the inside of the pressurized tank 2 to increase the pressure inside the pressurized tank 2. At this time, the pressure applied is 3
Although it is not particularly limited as long as it is 00 MPa or more, it is preferably 700 MPa or more from the viewpoint of food quality and sterilization.
00 MPa or less is preferable. The pressurizing time is a time sufficient for the food 5 to become commercially sterile according to the pressurizing pressure, the preheating temperature, and the like. There is no particular limitation as long as it is longer than the moment (0 seconds) when the pressurization ends, but specifically, from 1 second to 200 minutes, more preferably 1 minute to 10 minutes, from the viewpoint of food quality. Here, the term “commercial aseptic” means that no pathogenic bacteria are recognized,
It is defined as a food that is mildly degraded during a suitable storage period of up to 24 months and does not cause fermentation or microbial growth.

After the food 5 is maintained at an ultra-high pressure in the pressurizing step, the food 5 (inside the pressurizing tank 2) is rapidly reduced to atmospheric pressure.

Second Embodiment In the second embodiment, the sterilized food obtained in the first embodiment is maintained at the temperature after sterilization or cooled to a normal temperature after sterilization, and then further pressurized. Is repeated. Specifically, after the pressurizing step in the first embodiment is completed, the pressurization is relaxed (pause step), and the food 5 is pressurized again inside the pressurizing tank 2 under an ultra-high pressure of 300 MPa or more. These pause and pressurizing operations may be repeated two or more times as necessary. Here, the pause step is preferably performed at a pressure lower than the pressure applied in the pressurizing step, preferably at atmospheric pressure. In addition, the time for relaxing the pressurization may be from instant to 5 minutes or more, preferably at least 1 second to 5 minutes, more preferably at least 5 seconds to 1 minute.

In the above-described embodiment, the pressure medium 6 inside the heat insulating container 4 uses a liquid different from the food 5.
From the viewpoint of improving the efficiency of the pressure sterilization treatment, the food 5 itself can be used as the pressure medium 6. Further, a food 5 which can be sterilized by the food sterilization method according to the present invention.
Although not particularly limited, the method is particularly effective for foods having delicate aroma and texture. Such foods include, for example, cheese sauces, vegetables, soups, stews, curries, and soft beef, fish, pork, and other meats, dairy products, pasta,
Cooked rice, potato products, staple food entrees, desserts, beverages, chocolate milks, cottage cheeses, and the like. Furthermore, in the food sterilization method according to the present invention, in addition to foods that are generally stored at room temperature, for example, chilled foods and the like can be used.

Hereinafter, the present invention will be described more specifically with reference to examples.

Example 1 Preparation of Test Sample Food 5 for the test was cheese sauce (pH 5.5), white sauce (pH 6.2), and corn puree (pH 7.
7) A solution obtained by diluting sauteonion (pH 5.4) twice with water was used. Forty grams of these foods are placed in a normal pouch bag (two polyethylene films and two polypropylene films).
Bacillus subtilis spores as a bacterium for measuring the bactericidal effect was placed in a pouch bag at 1 × 10 ⁵ CFU / g, and sealed without air. Made a sample. Hereinafter, the processing conditions of each test sample will be described in order (some of the processing conditions are described in Table 1). (Preliminary heating step) A test sample was placed in warm water of 80 ° C for 10 minutes.
Heated by soaking for minutes. (Pressurizing Step) Next, the preheated test sample was pressurized and sterilized. As the sterilizer 1, an ultra-high pressure plant manufactured by Kobe Steel Ltd. was used. Further, as the heat insulating container 4, a cylindrical polybutylene terephthalate container (thermal conductivity, 0.3 W / m · ° C.) provided with a lid through which a test sample (pouch bag) can be taken in and out was used. Among the test samples to be pressurized using the heat insulating container 4, the preheated test sample is put in the heat insulating container 4, water is added as the pressure medium 6, and after filling the heat insulating container 4, the lid of the heat insulating container 4 is closed. After closing and putting the heat insulating container 4 into the inside of the pressurized tank 2,
The same pressure medium 6 as used when filling the heat insulating container 4
(Water) filled the inside of the pressurized tank 2. On the other hand, in the test sample without using the heat insulating container 4, the test sample is directly put into the inside of the pressurized tank 2, and then the pressurized tank 2 with water as the pressure medium 6.
Filled inside. Table 1 summarizes the pressure applied during the autoclaving, the applied time, and the pressure medium 6 used.
After autoclaving the test sample under each condition, the inside of the pressurized vessel 2 was depressurized and taken out of the pressure vessel, and the test sample was quenched with ice water. (Evaluation method) After the above treatment, each test sample was heated to 35 ° C.
For 4 weeks, a sterility test was performed, and the number of spoilage was measured. (Evaluation Results) The evaluation results are shown in Table 1.

[Table 1] The sterilized retort pouch food was stored at room temperature for one month, but no spoilage was observed in the sample using the insulated container. On the other hand, in the sample without the insulated container,
Bacillus subtilis was decaying.

[0016]

Example 2 (Preliminary heating step) The test sample prepared in Example 1 was heated by immersing it in hot water at 80 ° C for 10 minutes. (Pressurizing Step (First Pressing Step)) Next, the preheated test sample was pressurized and sterilized. As the sterilizer 1, an ultra-high pressure plant manufactured by Kobe Steel Ltd. (same as in Example 1) was used. Further, as the heat insulating container 4, a cylindrical container made of polybutylene terephthalate (similar to that of Example 1) having a lid at one end thereof with which a test sample (pouch bag) can be taken in and out was used. Among the test samples to be pressurized using the heat insulating container 4, the preheated test sample is put in the heat insulating container 4, water is added as the pressure medium 6, and after filling the heat insulating container 4, the lid of the heat insulating container 4 is closed. After closing and putting the heat insulating container 4 into the inside of the pressurized tank 2, the inside of the pressurized tank 2 was further filled with the same pressure medium 6 (water) as used when filling the heat insulating container 4. On the other hand, in the test sample without using the heat insulating container 4, the test sample was directly put into the inside of the pressurized tank 2, and then the inside of the pressurized tank 2 was filled with water as the pressure medium 6. Table 2 summarizes the pressure applied during the autoclaving, the applied time, and the pressure medium 6 used. (Pause step) After the test sample was autoclaved under each condition, the pressure inside the autoclave 2 was reduced to atmospheric pressure. The time was set to 10 seconds. (Pressurizing Step (Re-Pressing Step)) Further, pressurization was performed in the same manner as in the above-described pressing step (initial pressing step). Table 2 summarizes the pressure applied during the autoclaving, the applied time, and the pressure medium 6 used. After the test sample was autoclaved under each condition, the inside of the pressurized vessel 2 was depressurized, taken out of the pressure vessel, and then quenched with ice water. (Evaluation method) After the above treatment, each test sample was heated to 35 ° C.
For 4 weeks, a sterility test was performed, and the number of spoilage was measured. (Evaluation Results) The evaluation results are shown in Table 2.

[Table 2] The sterilized retort pouch food was stored at room temperature for one month, but no spoilage was observed in the sample using the insulated container. On the other hand, in the sample without the insulated container,
Bacillus subtilis was decaying.

[0017]

Example 3 The procedure of Example 1 was repeated except that the pressure was 300 MPa, the initial temperature was 100 ° C., and the pressurizing time was 20 minutes.
Ultra high pressure sterilization was performed. The sterilized food was stored at room temperature for one month, but no spoilage was observed. In addition, the flavor and aroma maintained a favorable state equivalent to that before sterilization.

[0018]

Example 4 Example 1 except that the pressure medium was oil (salad oil) and the temperature in the preheating step was changed from 80 ° C. to 75 ° C.
Ultra-high pressure sterilization was performed in the same manner as described above. (Evaluation method) After the above treatment, each test sample was heated to 35 ° C.
For 4 weeks, a sterility test was performed, and the number of spoilage was measured. (Evaluation results) The evaluation results are shown in Table 3.

[Table 3] In the sample in which the pressure medium was salad oil, the same sterilization effect was obtained even when the preheating temperature was lowered as compared with the water sample in which the pressure medium was water.

[0019]

The food sterilizing method according to the present invention includes a preheating step and a pressurizing step, and pressurizes the food 5 in a state where the food 5 is stored in the heat insulating container 4, so that the sterilizing power is dramatically increased. Spores having a high pressure resistance such as Bacillus subtilis can be sterilized to a level that does not spoil food even under a long-term normal temperature distribution.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional view of a sterilizer according to the present invention.

[Explanation of symbols]

 2 ... Pressurized tank, 4 ... Insulated container, 5 ... Food, 6 ... Pressurized medium

Claims (3)

[Claims] 1. A preheating step of heating a food (5) to a temperature of 50 ° C. or higher, and a step of heating the preheated food (5) to 300 ° C.
A food sterilization method comprising: a pressurizing step of pressurizing at a pressure of not less than MPa, wherein the food (5) is pressurized in a state of being stored in a heat insulating container (4). 2. A preheating step of heating the food (5) to a temperature of 50 ° C. or higher, and a step of heating the preheated food (5) to 300 ° C.
A food sterilization method comprising a pressurizing step of pressurizing at a pressure of not less than MPa, a pause step of releasing the pressurizing, and a pressurizing step of pressurizing the food (5) at a pressure of not less than 300 MPa,
A food sterilization method comprising pressurizing the food (5) in a state where the food (5) is housed in a heat insulating container (4). 3. The pressure medium (6) inside the pressurizing tank (2) and the inside of the heat insulating container (4) when pressurizing the food (5) is oil. Food sterilization method.