JP3096730B2 - Grain sterilization method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for sterilizing cereals used as a raw material of processed foods , and more particularly to a method of uniformly irradiating the surface of rotating cereals with a low-energy electron beam. The present invention relates to a method for disinfecting microorganisms attached to a grain surface .

[0002]

2. Description of the Related Art In order to prevent spoilage of processed foods and food poisoning caused by processed foods, it is necessary to prevent microbial contamination of processed foods. Therefore, sterilization of raw materials is an important matter in preventing microbial contamination of processed foods.
Conventionally, food ingredients have been sterilized by chemical or physical methods, but the ethylene oxide, methyl bromide, hydrogen peroxide, etc. used in these methods have harmful effects on the human body and the environment. In addition to the effects, there are concerns about the effects of these residues on the human body,
Various problems have been pointed out in terms of safety, and many of them have been banned or their use has been restricted.

[0003]

By the way, many microorganisms contaminating the surface of dry food materials such as cereals are heat-resistant bacteria, and these bacteria are spores which are durable cells. Is formed. These spores are more resistant to heat, germicides or drying than the growing bacteria, so they cannot be easily sterilized even when heated while keeping the grain dry, affecting the quality. It is very difficult to heat sterilize without affecting. On the other hand, sterilization by radiation irradiation, which has an excellent sterilizing effect and can easily sterilize dry grains, is not susceptible to quality deterioration due to heat because the temperature rise of the food itself is slight, but for complete sterilization Since a relatively large dose is required, many foods are difficult to put into practical use, for example, causing component changes such as damage to starch and oxidation of lipids, thereby losing value as a raw material for processing. In this way, it is harmless to the human body and the environment, and without causing a change in components such as starch and lipids in the cereal,
In other words, no method has yet been developed for disinfection without causing a change in grain quality. Therefore, not only the human body and the environment, but also sterilize the grains without changing the quality,
There is a need for a method of providing sterile grains.

[0004]

The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and focused on the fact that the bactericidal effect of electron beams and the penetration power of electrons depend on energy.
The inventors of the present invention have completed the method of sterilizing grain using an electron beam, and have studied the grain rotating device used in the method.

A first aspect of the present invention is to provide brown rice, paddy, wheat,
Grain selected from wheat, red beans, black beans and soybeans,
A method for sterilizing cereals, comprising irradiating the surface of a rotating grain with a low-energy electron beam of 160 to 250 keV while simultaneously applying vibration and lateral shaking to rotate the grain. The second invention relates to brown rice, paddy, wheat, soba with shells.
An attempt to accommodate grains selected from wheat, red beans, black beans, and soy.
Tray, tray mounting table, arranged in series below it
Vibrator and shaker, generated from the vibrator and shaker
A transmission device for transmitting vibration and shaking to the tray mounting table,
Power switch for operating the vibrator and shaker and this
Switch for operation and speed control of vibration and shaking
Grain rotating device with rollers under the electron beam generator
The grain stored in the sample tray in the vertical
Irradiates with low energy electron beam while shaking
The sterilization method according to claim 1 .

[0006]

DETAILED DESCRIPTION OF THE INVENTION Currently used radiation includes:
Γ-rays (electromagnetic waves), which have strong penetration power and can sterilize deep foods,
There are electron beams obtained from an electron beam accelerator and X-rays (electromagnetic waves) generated by an X-ray generator. Among them, the electron beam used in the present invention has a property of being inherently weak in permeation power and capable of reaching only the surface layer of grain. As the electron beam source, there are a scan type electron beam irradiator and an area beam type electron beam irradiator. In the present invention, it is preferable to use an area beam type electron beam irradiator. In the present invention, low-energy electron beams, that is, soft electrons, are used because the purpose is to kill microorganisms growing on the surface layer of cereals. Here, the low-energy electron beam is preferably an electron beam having an energy of 160 to 250 keV, and an appropriate low-energy electron beam is selected within this range in consideration of the type and shape of the target grain. For example, 160-18 for brown rice, wheat, etc.
0 keV, 200 ~ 2 for paddy and buckwheat beans with shell
Irradiation with 50 keV soft electrons is appropriate. The irradiation time of the electron beam to the grain varies depending on the beam amount, but may be appropriately determined in consideration of the type, shape, amount, and the like of the grain. For example, the beam amount is 20 to 50 m
In the case of the practical machine of A, it may be about 1 to 10 seconds.

[0007] The grains targeted by the present invention are brown rice, paddy,
Selected from wheat, buckwheat noodles, red beans, black beans and soybeans
It is. Hereinafter, these are simply referred to as “cereals”. In addition,
The method of the present invention can be applied to grains, pepper, coriander,
It can be applied to spices such as sage.

[0008] In order to sterilize microorganisms attached to the grain surface, it is necessary to uniformly irradiate all grain surfaces with an electron beam. For this reason, in the present invention, the grain is simultaneously rotated by applying a vertical vibration and a horizontal vibration, and the grain is irradiated with an electron beam in this state. In this case, the intensity (speed) of the vibration or shaking given to the grain is adjusted appropriately. When either one of vibration and shaking is given alone, it is difficult not only to rotate all the grains but to irradiate the electron beam uniformly to the grain surface even if the speed is changed. In addition, a long time is required for the sterilization treatment, and the sterilization efficiency is significantly reduced.

[0009] For this reason, the present inventors have developed a grain rotating device which can rotate the grain by applying vibration and shaking. This apparatus can uniformly rotate grains by giving vibration and shaking at a speed suitable for each grain in consideration of the type, shape, specific gravity and the like of the grains. This grain rotation device has the structure shown in FIGS. 1 and 2, and includes a sample tray 1, a tray mounting table 2,
A vibrator 4 and a shaker 5, which are arranged in series thereunder,
A transmission 3 for transmitting vibration and shaking generated by the vibrator and the shaker to the tray mounting table, a power switch 6 for operating the vibrator and the shaker, and a switch 7 for operating these (for operating the vibrator) , 8 (for operating the shaker) and the speed controllers 9 and 10 of the shaker and the shaker are main components. Numeral 11 in the figure is an outer panel of the apparatus,
Various instruments are arranged on an outer panel (instrument panel) in front of the apparatus as shown in the figure. 12 is a power lamp, 13 is a vibrator lamp, 14 is a shaker lamp, 15 is a fuse,
6 is an adjustment bolt.

The material and dimensions of this device may be appropriately set according to the purpose of use and the like. The main body (the portion surrounded by the outer plate) of the device used in the examples described later has a width of 35 cm × 30 cm in depth. × height 30 cm (height to the top of the sample tray is 45 cm), and the tray is preferably made of plastic and has a width of 30 cm × depth 9 cm × depth 3.5 cm. The amplitude of the tray on the tray mounting table is 3
cm and the vertical movement were set to be 0.2 cm. Note that a spring is preferable as the transmission.

A method for sterilizing cereals using this apparatus will be described. First, the apparatus is placed under the electron beam generator and connected to a power supply (not shown) to start the apparatus. Next, the sample tray 1 containing the grains requiring sterilization so as not to overlap in two or more stages is mounted on the tray mounting table 2, and the power switch 6 is turned on. Further, the vibrator operating switch 7 and the shaker operating switch 8 are each turned on to operate. The vibration and shaking generated by the vibrator and the shaker are transmitted to the transmission 3
And the grain in the sample tray 1 is given vertical vibration and horizontal shaking, and rotates. The movement of the vibrator and the shaker can be adjusted by the speed controller 9 of the vibrator and the speed controller 10 of the shaker so that the grains in the sample tray 1 can be set to rotate uniformly and appropriately.

In this state, the grains are sterilized by irradiating soft electrons from the electron beam generator. In this case, the distance from the electron beam generator to the tray bottom is adjusted to about 30 cm, preferably 5 to 20 cm. If the distance is too short, it becomes difficult to uniformly sterilize the grain surface, and if the distance is too large, a sufficient sterilizing effect cannot be obtained. By the way, the energy when the soft electrons emitted from the electron beam generator hit the grain can be measured by the following formula.

[0013]

[Equation 1] Electron energy (keV) = Original energy (k
eV) - stopping power ^{(keV · cm 2 / g)} × material thickness (cm) × specific gravity (g / c
m ³ )

For example, if the distance from the electron beam generator to the bottom of the tray is 5 cm, and if the electron energy near the exit of the electron beam generator (inside the titanium window foil) is 160 keV, the device exit (titanium window foil) The electron energy at (outside) is calculated from the above equation, and the stopping power of titanium: 228
7keV ・ cm ² / g (ICRU REPORT 37, Stopping Powers for
Electrons and Positrons, page 84, published October 1, 1984), thickness of material (titanium window foil): 0.005 cm, specific gravity:
Substituting 4.54 g / cm ³ gives 108.1 keV. The electron energy at a position 5 cm away from the electron beam generator, that is, when hitting the grain, is the stopping power of air: 3637 keV · cm ² / g (IC
RU REPORT 37, Stopping Powers for Electrons and Po
sitrons, page 120, published on October 1, 1984), material thickness: 5 cm, specific gravity: 1.20 × 10 ^-3 g / cm ³ and 86.3 k
eV. The electron energy at a position 20 cm away from the device, that is, when hitting a grain, is calculated by the same calculation.
It becomes 20.8keV. On the other hand, when the electron energy from the electron beam generator is 250 keV, when the distance from the device to the tray bottom is 5 cm, the energy when hitting the grain is 194.2 keV by the same calculation, and the distance from the device to the tray bottom is Is 20 cm, the energy when hitting a grain is 149.6 keV.

After the sterilization of the grain surface is completed by irradiating soft electrons for a predetermined time, the operation switches 7 and 8 are turned on.
FF, and the power switch 6 is turned off. In the grain rotating device of the present invention, the amount of grain that can be processed in one operation basically depends on the bottom area of the tray, but is usually 10 to 70 g, preferably 20 to 40 g.

[0016]

Next, the present invention will be described in detail with reference to examples, but the present invention is not limited to these examples. Example 1 A sterilization test was separately performed on each of brown rice, paddy, wheat, and buckwheat with shells. That is, 20 g of each sample is accommodated in a sample tray, and while being rotated by the above-described operation with a grain rotating device (shown), low-energy electrons in the range of 160 to 230 keV using a Van de Graaff-type electron accelerator as a radiation source. After irradiating a line (soft electron) with a beam amount of 4 μA for 1 hour, the viable cell count on the grain surface and the grain viscosity were measured.

The viable cell count was measured by the following method.
5 g of a sample is homogenized in 25 ml of 0.9% aqueous sodium chloride solution (physiological saline) (manufactured by Nippon Seiki Co., Ltd.
"Ace homogenizer"). 0.2 ml of this suspension was applied on a normal agar medium (“Nissui Ordinary Agar Medium”, manufactured by Nissui Pharmaceutical Co., Ltd.).
After culturing at 0 ° C. for 48 hours, the number was determined from the number of colonies formed on the medium. When the number of viable bacteria was 100 or less, particularly 10 or less, it was determined that the bacteria had been almost sterilized. The number of viable bacteria present on the untreated grain surface was 1 as described below.
0 is ⁴ to 10 ⁷ or so. The measurement of the viscosity was performed by the following method. After pulverizing the sample using a coffee mill, purified water is added to the suspension to give a 7.5% aqueous suspension of 40 m.
and prepare 2 ml of 33% sodium hydroxide solution.
After stirring well, the mixture was heated in a boiling water bath for 30 minutes. Next, it was left at 25 ° C. for 3 hours and measured with a rotational viscometer (manufactured by Haake). In addition, as a control, the grain which was not irradiated with an electron beam (untreated) was measured in the same manner as described above.
Table 1 shows the results of measuring the viable cell count, and Table 2 shows the results of the viscosity measurement.

COMPARATIVE EXAMPLE 1 Instead of an electron beam, ⁶⁰ Co was used as a radiation source and one gamma ray was used.
Except that irradiation was performed at 0 kGy, the same procedure was performed as in Example 1. Table 1 shows the results of measuring the viable cell count, and Table 2 shows the results of the viscosity measurement.

[0019]

[Table 1] Table 1 Number of viable bacteria on grain surface エ ネ ル ギ ー Energy Brown rice paddy wheat buckwheat with shell 殻 No treatment 5.8 × 10 ⁶ 3.8 × 10 ⁷ 3.5 × 10 ⁴ 2.1 × 10 ⁶ 150 3.7 × 10 ⁴ 4.8 × 10 ⁶ 1.4 × 10 ³ 3.1 × 10 ⁵ 160 <10 7.3 × 10 ⁵ <10 6.0 × 10 ⁴ 170 <10 5.1 × 10 ⁵ <10 4.7 × 10 ³ 180 <10 8.8 × 10 ⁴ <10 3.8 × 10 ³ 190 <10 7.3 × 10 ³ <10 8.3 × 10 ² 200 <10 <10 <10 <10 210 <10 <10 <10 <10 220 <10 <10 <10 <10 230 <10 <10 <10 <10 γ-ray < 10 <10 0 <10 <10 ──────────────────────────────────── All units are pieces / g .

[0020]

[Table 2] Table 2 Grain viscosity エ ネ ル ギ ー Energy Brown rice Paddy Wheat Soba with shell ──────────────────────────────────── No treatment 208.0 154.9 291.7 223.8 150 207.2 155.7 291.6 211.6 160 210.8 153.0 292.8 221.9 170 205.9 159.1 290.2 218.1 180 205.5 152.0 291 .5 225.5 190 195.3 153.1 278.6 214.1 200 188.8 151.7 243.0 220.6 210 132.6 153.3 208.4 210.1 220 103.4 133. 9 194.3 194.5 230 96.6 1 1.9 145.8 133.5 γ-ray 21.1 31.9 34.6 26.8} ───────── All units are mpa. s.

From the viable cell count results in Table 1, the brown rice and wheat are 160 keV or more, and the rice and the buckwheat with husk are 200 keV.
By irradiating soft electrons with energy of V or more, the microorganisms existing on the surface could be almost completely killed. On the other hand, regarding the viscosity, as is clear from Table 2, a decrease in the viscosity was observed when the brown rice and wheat were irradiated with soft electrons of 190 keV or more and the rice and buckwheat with husks were irradiated with soft electrons of 220 keV or more. When γ-rays were irradiated instead of the electron beam, all the grains were almost sterilized, but the viscosity of the grains was significantly reduced. From the above, brown rice and wheat are 160-180k
It was shown that when eV, paddy and buckwheat with shells were irradiated with an electron beam of 200 to 210 keV, the starch could be sterilized almost without decomposition of starch.

Example 2 Using the above-described grain rotating device, while rotating 20 g of brown rice, a Van de Graaff type electron accelerator was used as a radiation source.
After irradiating with an electron beam of ~ 200 keV at a beam amount of 4 μA for 1 hour, thiobarbituric acid value (hereinafter, referred to as TBA value) is used as an index of lipid peroxidation in milled rice polished so as to have a yield of 90% or 88%. Was measured. In addition, unmilled rice was similarly tested as a control. T
The BA value was measured using a 250 mg sample in the usual manner (Kaneda
It was measured based on Naoshi and Nobuo Ueda, "Lipid Peroxide Experimental Method", published by Medical and Dental Medicine Publishing Co., Ltd., pp. 84-85).
Table 3 shows the results.

Comparative Example 2 The same procedure as in Example 2 was carried out except that no electron beam was irradiated. Table 3 shows the obtained results.

Comparative Example 3 Instead of an electron beam, ⁶⁰ Co was used as a radiation source and one gamma ray was used.
Everything was performed in the same manner as in Example 2 except that the irradiation was performed at 0 kGy. Table 3 shows the obtained results.

[0025]

[Table 3] Table 3 Ｔ TBA value of brown rice flour and milled rice flour ──────── ─────────────────── Non-milling Milling yield Energy 90% 88% (brown rice) (polished rice) (polished rice) ───────────── ────────────── No processing 18.3 4.5 4.4 160 27.6 4.7 4.5 170 170 29.8 4.9 4.7 180 34.2 28 .4 4.8 190 41.4 9.5 9.4 200 55.2 14.3 14.4 γ-ray 56.2 46.6 45.2} ─────────────

As apparent from Table 3, regardless of the energy of the soft electrons, the TBA value of unmilled (brown rice) treated with the soft electrons is 1.5% of that of the untreated rice.
~ 3.0 times. However, in the case of rice polished at a yield of 90% or 88% after treatment with energy of 160 to 170 keV, the same T as that of untreated rice is obtained.
The BA value was indicated. In addition, polished rice polished with a yield of 88% after treatment with an electron beam of 180 keV showed the same TBA value as that of the untreated rice. However, 190ke
Brown rice treated with soft electrons having an energy of V or more, when milled at a yield of 90% or 88%, showed a higher TBA value of 2.1 to 3.3 times than that of untreated rice. Therefore, for brown rice,
After the treatment with a low energy electron beam of 160 to 170 keV, the portion irradiated with the electron beam is removed by milling at a yield of 90%, so that the polished rice (endosperm)
Lipids are not affected by electron beams. In the case of milling at a yield of 88%, lipids in the polished rice (endosperm) are not affected by the electron beam if processed with an electron beam up to 180 keV. On the other hand, when γ-rays are irradiated instead of electron beams, unmilled brown rice has a 3.1 times higher yield and a yield of 9 times.
The milled rice polished at 0% or 88% exhibited a TBA value about 10 times that of the untreated rice, and it was revealed that the peroxidation of lipids was advanced in the milled rice after milling.

Example 3 A sterilization test was conducted in the same manner as in Example 1, except that beans were used instead of brown rice and the like. Table 4 shows the results of measuring the viable cell count on the grain surface.

[0028]

[Table 4] Table 4 Number of viable bacteria on grain surface ───────────────────────────── Energy Red beans Black beans Soy beans ──── ───────────────────────── No treatment 7.5 × 10 ³ 1.5 × 10 ⁴ 2.8 × 10 ³ 150 <100 <100 <100 160 <10 <10 <10 170 <10 <10 <10 180 <10 <10 <10 190 <10 <10 <10 200 <10 <10 <10 220 <10 <10 <10 230 <10 <10 < 10 γ-ray <10 <100 <10 ───────────────────────────── All units are units / g.

As is clear from the table, in the case of beans, 1
By irradiating soft electrons with energy of 60 keV or more, the microorganisms existing on the surface could be almost sterilized.

[0030]

According to the method of the present invention, the grain of starch is damaged by irradiating the electron beam with the minimum energy required for sterilization while rotating the grain uniformly and reliably. Therefore, microorganisms adhering to the grain surface can be efficiently sterilized. In addition, when brown rice is sterilized, by milling after the treatment, the site irradiated with the electron beam can be removed, so that the milled rice obtained from the brown rice sterilized by the method of the present invention contains lipids. Not oxidized. The method of the present invention can be efficiently implemented by using a grain rotation device.

[Brief description of the drawings]

FIG. 1 is a front view of one embodiment of a grain rotation device used in the present invention, and dotted lines indicate an internal vibrator and a shaker.

FIG. 2 is a side view of one embodiment of a grain rotating device used in the present invention, and dotted lines indicate an internal vibrator and a shaker.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 sample tray 2 tray mounting table 3 transmission device 4 vibrator 5 shaker 6 power switch 7 vibrator operation switch 8 shaker operation switch 9 vibrator speed controller 10 shaker speed controller

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroshi Okadome 2-11-804-402, Azuma, Tsukuba-shi, Ibaraki (56) References JP-A-5-57204 (JP, A) Food Industry, (1996) Vol. 39, No. 22, p. 45-51 (58) Field surveyed (Int. Cl. ⁷ , DB name) A23B 9/00 A23L 3/26

Claims (2)

(57) [Claims] (1) Brown rice, paddy, wheat, buckwheat with shell, red beans, black beans
And soybeans with vertical vibration and horizontal
A method for sterilizing grain, comprising irradiating the surface of the rotating grain with a low-energy electron beam of 160 to 250 keV while simultaneously shaking and rotating the grain. 2. Brown rice, paddy, wheat, buckwheat with shell, red beans, black beans
Trays and trays containing grains selected from
-The mounting table, the vibrator and the vibrator
Shaker, vibration and shaking generated from the shaker and the shaker.
A transmission device for transmitting to the tray mounting table, the vibrator and the shaker
Power switch to activate the
Switch and vibration and shaking speed controller
Place the grain rotation device under the electron beam generator and
The grain contained in the leh is subjected to vertical and horizontal shaking.
2. The method according to claim 1, wherein the irradiation is performed with a low energy electron beam.
Sterilization method.