JPH06319499A - Heat sterilization of fluid food by joule heat and apparatus therefor - Google Patents

Abstract

PURPOSE:To provide a heat sterilization method carried out by uniformly heating a fluid food such as liquid egg without spoiling the properties thereof and capable of overcoming or reducing the problems in the conventional technique. CONSTITUTION:This method for heat sterilization of a fluid food is carried out characteristically by using a cylindrical tank equipped with two or more electrodes on the inner surface and electrically charging a fluid food accommodated in the tank to be treated with stirring.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for heat-sterilizing a fluid food product by utilizing Joule heat. INDUSTRIAL APPLICABILITY The present invention is particularly useful for heat sterilization of liquid eggs (unless particularly required, whole eggs, egg yolk and egg white are referred to as liquid eggs).

In the present invention, the "cylindrical body" means
It is not limited to a container or a tubular body whose cross section is a perfect circle,
It also includes oval shapes.

[0003]

2. Description of the Related Art A heat sterilization method for foods utilizing Joule heat is already known. However, there are major problems in applying this method to heat sterilization of liquid eggs.

In recent years, the number of food poisoning due to Salmonella has been increasing, and in Japan, it has reached the first place in the number of food poisoning. Among them, the number of Salmonella poisoning caused by eggs is rapidly increasing. Therefore, reliable sterilization of liquid eggs is extremely important.

The heating conditions required for sterilizing Salmonella are usually 58 ° C. for 5 minutes or 63 ° C. for 3 minutes (Japanese Patent Publication No. 60-4813).
No. 6 publication).

[0006] Conventionally, sterilization of liquid eggs has been carried out by using hot water or steam by external heating using a stainless steel pipe or panel heater. However, in the prior art, it is extremely difficult to heat-treat a large amount of liquid eggs at a uniform temperature because of physical properties peculiar to liquid eggs. That is, since the temperature difference in the liquid egg becomes large, when trying to completely sterilize, the protein in the liquid egg in the locally heated part becomes a denatured gel and the flavor is deteriorated. There is a drawback that it ends up.

[0007]

DISCLOSURE OF THE INVENTION The present invention solves or alleviates the problems of the prior art and provides a technique for uniformly heating and sterilizing liquid food such as liquid egg without impairing the characteristics thereof. The main purpose is to do.

[0008]

The inventors of the present invention have conducted various studies in order to solve the above-mentioned problems, and as a result, arranged at least two electrodes on the inner surface of a cylindrical container and It has been found that, when the fluid food to be treated is housed in and the electricity is applied to the food while stirring, the fluid food containing the liquid egg can be heat-sterilized while controlling the temperature conditions strictly.

That is, the present invention provides the following heat sterilization treatment method for fluid food and its method: Place at least two electrodes on the inner surface of the cylinder,
A method for heat sterilization of a fluid food, characterized in that the fluid food to be treated contained in the cylinder is energized under stirring.

2. Item 2. The heat sterilization method according to Item 1, wherein the fluid food to be treated is a liquid egg.

3. A heating and sterilizing apparatus for a fluid food by Joule heat, comprising a cylindrical body for containing a fluid food to be treated, at least two electrodes arranged on the inner surface of the cylindrical body, and a stirring mechanism.

4. A cylindrical body containing the fluid food to be treated and an agitator provided in the cylindrical body are provided, and an electrode having a conductive ceramic coating formed on a metal or carbon base material on the inner surface of the cylindrical body and the agitator surface of the agitator. A heat-sterilization device for fluid foods by Joule heat, which is characterized by being provided.

5. A cylindrical body containing a fluid food to be treated and at least a pair of blades for scraping the inner peripheral wall of the cylindrical body are provided, and the inner wall surface of the blade is coated with a conductive ceramics on a metal or carbon base material. A heat-sterilization device for fluid foods by Joule heat, which is provided with formed electrodes.

6. It has a cylindrical body through which the fluid food to be treated passes and an electrode provided on the cylindrical body, and the electrode has a conductive ceramic coating formed on a metal or carbon base material, and is formed on the inner peripheral surface of the cylindrical body. A heat sterilizer for fluid foods by Joule heat, which is characterized in that it is extended in the form of multiple threads.

7. The heat sterilizer according to any one of claims 3 to 6, wherein the fluid food to be treated is a liquid egg.

The present invention will be described in detail below with reference to the drawings.

FIG. 1 is a perspective view showing an outline of a heat sterilizer used in the present invention. The apparatus shown in FIG. 1 includes a cylindrical container 1 for containing a liquid food to be treated, two electrodes arranged on the inner surface thereof, and two electrodes respectively connected to the two electrodes.
Book leads 7, 9 are provided. The cylindrical container 1 is made of a non-conductive or low-conductive material such as glass, polypropylene or fluororesin. Stirring mechanism (not shown)
Is not particularly limited, and may be a propeller-type stirrer arranged inside the container, or may be a magnetic stirrer arranged outside the container.

The electrodes 3 and 5 are not particularly limited, but from the viewpoint of hygiene, metals such as titanium, iron, aluminum and stainless steel, and metals having a conductive ceramic coating (titanium, Copper, aluminum, stainless steel, etc.), a carbon material coated with a conductive ceramics, and the like. Examples of the carbon material include molded sintered bodies such as graphite and isotropic carbon.

Examples of the material for forming the conductive ceramic coating on metals or carbon materials include titanium oxide, titanium nitride, silicon carbide, and mixed or composite materials thereof. However, the conductive ceramic coating is required to have various electrical characteristics such as conductivity depending on the situation.
There is no particular limitation on the material composition, the mixing ratio in the mixture or the composite material, and the like. These conductive ceramics can be formed in layers by thermal spraying on the above metals or carbon materials. The thermal spraying may be carried out according to a conventional method, and if necessary, various undercoating treatments may be carried out or two or more kinds of conductive ceramic materials may be used in combination. The thickness of the conductive ceramics coating is not particularly limited as it may vary depending on the resistance value of the ceramics and the like, but is usually about 30 to 300 μm.

When the conductive ceramic coating formed by thermal spraying is used as the electrodes 3 and 5, the surface is porous. Therefore, by containing a heat-resistant material that is harmless to food hygiene in the surface voids, it improves the water repellency of the electrode surface and enhances the separability of liquid or pasty fluid food from the electrode to improve workability. Can be improved. Examples of such heat-resistant materials include synthetic resins such as cellulose-based resins, fluorine-based resins, silicone-based resins, olefin-based resins, polyester-based resins, and calcined products such as zirconia and titania sol. The filling of the electrode surface voids with such a synthetic resin is performed by forming a conductive ceramics film on the electrode surface in advance, immersing it in an organic solvent solution or water dispersion of these resins, drying, and if necessary heat treatment. It can be done by doing.

FIGS. 2, 3 and 4 show yet another aspect of the present invention.

The apparatus 11 of FIG. 2 is provided with a stirrer 15 inside the container 13, and one electrode A,
A is formed, and the other electrodes B and B are formed on the entire surface of the stirring blade that is the stirring body of the stirrer 15. The electrodes A, A
Each of B and B has a structure in which a conductive ceramic coating is formed on a metal or carbon base material.

The apparatus 21 shown in FIG. 3 has a pair of vanes 25 inside the container 23 that are in contact with or close to the inner peripheral wall of the container and are opposed to each other.
And 27, and the electrodes A ′ and B ′ are formed on the inner wall surfaces of the vanes 25 and 27, respectively. The electrodes A ′ and B ′ have substantially the same configuration as the electrodes A and B in FIG.

In the device 31 of FIG. 4, a cylindrical container 33 is used.
2 have electrodes A "and B" formed in a multi-threaded shape on the inner peripheral surface thereof, and the electrodes A "and B" are also electrodes A and B in FIG.
It has substantially the same configuration as.

The heat sterilization treatment of the fluid food (hereinafter represented by a liquid egg) by each of the above-mentioned devices 11, 21 and 31 is performed as follows.

In the device 11 shown in FIG. 2, the cylindrical container 13
The liquid egg contained therein is sterilized by heating with Joule heat by applying an alternating voltage between the electrodes A and B. In the process of this treatment, the stirrer 15 stirs the liquid egg. The stirrer 15 uniformly heats the liquid egg with respect to the electrode A on the container 13 and the electrode B on the stirrer to prevent the liquid egg from staying near the electrodes. As a result, the liquid egg to be heat-treated is
Satisfactorily sterilized without gelling and accumulating in the vicinity of B and B.

In the device 21 shown in FIG. 3, the liquid eggs in the cylindrical container 21 are heated by Joule heat by the energization from the electrodes A'and B'on the blades 25 and 27 while the blades 25 and 27 are rotating. Be sterilized. In this type of device, vanes 2
Since 5 and 27 scratch the inner wall surface of the container and also act as a stirring blade, the stirrer 1 in the apparatus of FIG.
It has the same function as 5. Therefore, the same result as above can be obtained by the apparatus of FIG.

In the device 31 shown in FIG. 4, a cylindrical container 33 is used.
While passing the liquid egg through the inside, the liquid egg is heated and sterilized by energizing the electrodes A ″ and B ″. In this device, since the electrodes A ″ and B ″ are formed in a multi-threaded shape, the liquid egg does not stay near the electrodes A ″ and B ″ when flowing through the container 33. Also, with this type of electrode, the current flow is uniform and the same excellent results as in the device shown in FIGS. 2 and 3 are obtained.

Since the device of the present invention has the above-mentioned effects, it is possible to sterilize whole eggs and egg yolk under the required severe heating conditions. In addition, sterilization treatment of egg white under required heating conditions can be performed in the same manner.

The electrodes used in the device of the present invention shown in FIGS. 2 to 4 are composed of a metal or carbon base material coated with a conductive ceramics. Therefore, there is no risk of discoloration of the liquid egg and dropping of carbon particles due to metal ions accompanying the energization.

[0031]

EFFECTS OF THE INVENTION According to the present invention, the problems of the prior art are eliminated or greatly reduced, and heat sterilization treatment of liquid foods (liquid egg, white sauce, custard, etc.) utilizing Joule heat is effectively performed. Can be done.

Further, according to the present invention, the temperature control during heat sterilization is performed by adjusting the current, voltage, time, etc.
Since it can be carried out very easily, the quality of the fluid food to be processed is hardly deteriorated.

[0033]

EXAMPLES The results of the heat sterilization treatment by Joule heat according to the present invention for liquid eggs are shown below.

Example 1 Egg white liquor and whole egg liquor were heat-sterilized by using the apparatus according to the present invention shown in FIG.

That is, a magnetic bar is housed inside a glass cylinder 1 having a diameter of 10 cm and a height of 10 cm and opened upward, four thermistors are inserted, and a magnetic stirrer is closely attached to the outside of the bottom of the glass cylinder. The egg liquid to be sterilized in the glass cylinder was rotated at an arbitrary speed.

On the inner surface of the glass cylinder, two titanium foils (thickness: 2 μm, width: 10 c) sprayed with a conductive ceramic were sprayed.
m, height 11 cm) were vertically opposed to each other, and an alternating current (50 to 100 V, 400 Hz) was passed. 15 egg white liquor or 10 whole egg liquor at room temperature was housed in such a device, and the mixture was stirred at 240 rpm while Salmonella enteritidis KF1 was used as a test bacterium.
0799) culture solution 1 ml (18 with tryptoso-yavillon)
Time culture, viable cell count 2.0 × 10 ⁸ / ml) was transplanted.
Energization is performed at a voltage in the range of 50 to 100 V depending on the rate of temperature rise, and the temperature is maintained at 58 ° C in the case of egg white liquid and 62 ° C in the case of whole egg liquid so as to maintain the same temperature. The electric current was adjusted to 10 minutes, and each was kept for 10 minutes for sterilization.

After completion of sterilization, egg white liquid and whole egg liquid were collected and subjected to enrichment culture and confirmation culture according to a conventional method, but no typical colony was generated. The same operation was repeated 10 times to confirm reproducibility.

[0038] From the above results, a proportion of the total Tamagoeki the viable count of Salmonella enteritidis utility disk is 2.0 × 10 ^8/15 pieces of egg white liquid egg and 2.0 × 10 ^8/10 pieces of eggs It was confirmed that sterilization can be performed on both contaminated egg white liquid and whole egg liquid.

Further, the temperature measurement at the time of temperature rise is measured by
The measurement was performed at three points in the vicinity of the electrode and on the side surface where the electrode was not arranged. The temperature rising curve at this time is shown in FIG. As is clear from FIG. 5, the temperature rising curves at the three locations were almost the same, and the temperature difference was within 0.5 ° C.

Example 2 Using the same apparatus as in Example 1, Salmonella enteritidis was transplanted into egg white liquor for 14 eggs and heat sterilization was performed.

Table 1 shows the viable cell count, the holding temperature, the holding time and the results.

[0042]

[Table 1]

From the results shown in Table 1, it is clear that sterilization (complete sterilization) can be performed even under the condition of lower temperature and shorter time than in Example 1.

Example 3 Using the same apparatus as in Example 1 and conducting electricity under the same conditions as in Example 1, the whole egg liquid for 9 eggs was heated to 80 ° C. and the test bacteria were immediately transplanted. did. The viable cell count at the time of transplantation calculated from the viable cell count of the transplanted cell and the volume of the whole egg solution was 4.0 × 10 ⁶ /
It was ml. When the viable cell count in the whole egg solution after holding at 60 ° C. for 1 minute was determined by the 10-fold dilution method, it was 10 / ml or less. Therefore, according to the present invention, in the case of the above-mentioned viable cell count of the test bacteria, if it is kept at 60 ° C. for 1 minute,
It can be 1 or less.

Comparative Example 1 Heat treatment of egg white liquor was carried out in the same manner as in Example 1 except that electrodes were arranged vertically opposite to each other on two inner wall surfaces of a square glass container (one side 10 cm, height 10 cm) which face each other. I did.
Egg white liquor could not be sterilized in 8 out of 9 cases. It is considered that this is because the four corners of the bottom of the container were cooled from the outside, the temperature rise was delayed, and the stirring at the four corners of the container was insufficient.

[Brief description of drawings]

FIG. 1 is a perspective view showing an example of a heating device using Joule heat according to the present invention.

2A is a cross-sectional plan view showing an example of an apparatus according to the present invention, and FIG. 2B is a vertical cross-sectional view thereof.

3A is a cross-sectional plan view showing another embodiment of the device of the present invention, and FIG. 3B is a vertical cross-sectional view thereof.

4A is a cross-sectional plan view showing another embodiment of the present invention, and FIG. 4B is a vertical cross-sectional view thereof.

FIG. 5 is a graph showing a temperature rising curve during heat sterilization treatment in Example 1.

[Explanation of symbols]

 1 ... Cylindrical container 3, 5 ... Electrode 7, 9 ... Lead 11 ... Inventive device 13 ... Cylindrical container 15 ... Stirrer A ... Electrode B ... Electrode 21 ... Inventive device 23 ... Cylindrical container 25, 27 ... Blade Plate A '... Electrode B' ... Electrode 31 ... Device of the present invention 33 ... Cylindrical container A "... Electrode B" ... Electrode

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoko Okuda 2-9-9 Iko, Takarazuka-shi, Hyogo (72) Inventor Yoshiyoshi Inui 3-6-8, Kutaro-cho, Chuo-ku, Osaka-shi, Osaka Toyo Aluminum Co., Ltd. In the company

Claims (7)

[Claims] 1. A heat sterilization method for fluid foods, characterized in that at least two electrodes are disposed on the inner surface of a cylindrical body, and the fluid food to be treated contained in the cylindrical body is energized with stirring. 2. The heat sterilization method according to claim 1, wherein the fluid food to be treated is liquid egg. 3. A heat sterilization device for fluid food by Joule heat, comprising a cylindrical body for containing a fluid food to be treated, at least two electrodes arranged on the inner surface of the cylindrical body, and a stirring mechanism. . 4. A cylindrical body containing a fluid food to be treated and a stirrer disposed inside the cylindrical body, wherein the inner surface of the cylindrical body and the stirrer surface of the stirrer are coated with a conductive ceramic on a metal or carbon base material. A heat-sterilization device for fluid foods by Joule heat, which is provided with electrodes formed with. 5. A cylindrical body containing a fluid food to be treated and at least a pair of blades for scraping the inner peripheral wall of the cylindrical body, wherein the inner wall surface of the blade is coated with a conductive ceramic on a metal or carbon base material. A heat-sterilization device for fluid foods by Joule heat, which is provided with electrodes formed with. 6. A cylindrical body through which a fluid food to be treated passes, and an electrode provided on the cylindrical body, wherein the electrode has a metal or carbon base material and a conductive ceramic coating formed thereon. An apparatus for heat sterilization of fluid foods by Joule heat, characterized in that it is extended in a multi-threaded shape on the inner peripheral surface of. 7. The heat sterilizer according to claim 3, wherein the fluid food to be treated is a liquid egg.