JPH0195751A - Sterilization of drink - Google Patents

Abstract

PURPOSE:To exterminate sundry germs in a liquid drink without lowering the quality of the drink, by applying a high-voltage pulse of a specific electric field strength to a liquid drink. CONSTITUTION:A liquid drink such as soft drinks, liquid dairy products, liquid seasonings, etc., is continuously supplied between a pair of electrodes preferably having coaxial double-cylinder form. The drink between the electrodes is applied with high-voltage pulses having an electric field strength of 2-100kV/cm at the application of the pulse, a pulse rise time of 20nsec-1musec and a pulse width of 100nsec-1msec.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for sterilizing beverages. More specifically,
The present invention relates to a method for sterilizing germs in a beverage liquid by applying a high-voltage electric field pulse.

[Conventional technology]

BACKGROUND OF THE INVENTION When producing beverages batchwise or continuously, one of the most important factors is the prevention of bacterial contamination of beverage liquids, that is, beverage raw materials, semi-finished products, and finished products. Bacterial contamination is also regulated under the Food Sanitation Act. In particular, since it is customary to manufacture beverages by continuous operation for a long period of time, contamination with various bacteria would have a serious effect on continuous operation.

Therefore, various methods for preventing bacterial contamination of beverage liquids have been proposed and developed.

Common examples include heat sterilization and filter sterilization.

[Problem that the invention seeks to solve]

However, in the sterilization method by heating, the quality of the beverage may change due to heating, so temperature conditions and heating time are limited, making it difficult to perform satisfactory sterilization. In addition, the sterilization method using filters has high running costs and problems with longevity due to filter clogging.

On the other hand, as an electrical method, it is possible to sterilize by applying a high-voltage electric field (e.g., arc discharge, plasma discharge), but an excessive current flows through the object to be discharged, causing electrolysis or chemical changes, and even if Even if the desired sterilizing effect is achieved, the quality of the beverage will change.

This invention was made based on the above-mentioned background, and its purpose is to easily and economically prevent bacterial contamination of beverage raw materials, semi-finished products, and finished products, with minimal impact on beverage quality. The goal is to provide a method to do so.

[Means for solving problems]

As a result of conducting various research studies to solve this problem, the present inventors discovered that the application of high-voltage electric field pulses affects microorganisms [Akira Mizuno et al.: Collection of Lecture Abstracts at the Gunma Convention of the Society of Chemical Engineers (1988)] 2000) p. 211 and Akira Mizuno et al.: Collection of abstracts of the National Conference of the Institute of Electrical Engineers of Japan (1986) I), 709)
I got it. This is because the effect of applying a high-voltage electric field pulse is
This is thought to be because a shock wave or electric field is generated by applying a high-voltage electric field pulse in a liquid, and the generated shock wave or electric field causes physical damage to microorganisms (for example, damage to cell membranes or cell walls).

Furthermore, as a result of further testing and research, the inventors discovered that applying a high-voltage electric field pulse to a beverage liquid under predetermined conditions is effective in achieving the object of the present invention, leading to the completion of the present invention.

That is, in the beverage sterilization method of the present invention, a high-voltage electric field pulse is applied to a beverage liquid at a voltage of 2 kV/cm to 100 kV/cm.
Electric field strength when applying cm pulse, 20 nsec ~ 1μ
Rise of pulse waveform of See, 100 nsec~1
It is characterized in that it is applied with a pulse waveform width of m5ec.

In a preferred embodiment of the invention, a sterilization tank having coaxial double cylindrical electrodes is used, a high voltage electric field pulse is applied between the coaxial double cylindrical electrodes, and a beverage liquid is continuously supplied between the electrodes. can be sterilized by

[For production]

When a high-voltage electric field pulse is applied to a beverage liquid under the application conditions according to the present invention, as described above, the high-voltage electric field pulse generates shock waves or rapid fluctuations in the electric field in the liquid, and the generated shock waves or electric field fluctuations act against microorganisms. selectively causes physical damage (for example, damage to cell membranes and cell walls). On the other hand, various non-microbial components (proteins, carbohydrates, vitamins, etc.) in the beverage are not substantially affected by the pulsed shock waves or electric field fluctuations.

It should be noted that the above explanation is provided for the purpose of understanding the present invention, and does not limit the scope of the present invention.

This invention will be explained in more detail below.

The beverage sterilization method of this invention applies a high-voltage electric field pulse to a beverage liquid, the electric field strength when applying a pulse of 2 kV/Cm to 100 kV/am, the rise of the pulse waveform of 20 nsec to 1 μsec, and the pulse waveform of 100 nsec to 1 m5ec.
It is characterized in that it is applied with a pulse waveform width of .

Object to be sterilized The object to be sterilized in the present invention is a beverage liquid from which germs are preferably removed, that is, raw materials, semi-finished products, and finished products of the beverage. Examples of such products include soft drinks, alcoholic beverages, soy sauces, lactic acid drinks, milk, liquid dairy products, oils, coffee drinks, liquid seasonings, and their raw materials and manufacturing intermediates. .

Application of high-voltage electric field pulses/sterilization By applying high-voltage electric field pulses to the above-mentioned beverage liquid, bacteria in the liquid can be removed without altering the quality components of the beverage liquid (e.g., protein denaturation, chemical changes, etc.). annihilate. The application of high-voltage electric field pulses is usually carried out by applying a high voltage to an electrode immersed in a beverage liquid using a discharge switch so that a predetermined electric field strength is achieved.

In a preferred embodiment of the present invention, a sterilization tank having coaxial double cylindrical electrodes is used, a high voltage electric field pulse is applied between the coaxial double cylindrical electrodes, and a beverage liquid is continuously applied between the electrodes. can be supplied to sterilize.

(a) High-voltage electric field pulse The high-voltage electric field pulse used in this invention has a maximum electric field strength between electrodes of 2 kV/cm ~], 0
0 kV/am, and when the voltage between the electrodes at that time is monitored with an oscilloscope, the pulse waveform (waveform showing temporal changes in voltage) has a rise of approximately 20 n5e.
It is extremely fast at c-1μsec, and the width is about 100nsec~
It is a high speed pulse (or short time pulse) of 1 m5ec. This fast pulse is obtained by discharging the capacitor charging energy over a short period of time through a discharge switch. As the discharge switch, a static gap, a rotating gap, a thyristor, a thyratron, etc. can be used. Ordinary aqueous solutions contain large amounts of ions and are good electrical conductors, so when a direct current is applied to the immersed electrodes, a large current flows and electrolysis occurs.

However, when a pulse like the one described above is applied, the electrons run at high speed, but the ions that carry the current move slowly, so the aqueous solution exhibits properties similar to electrically insulating liquids. That is, it is characterized by being able to create a field with high electric field strength in a conductive aqueous solution [Masayuki Sato et al.: Collection of Lecture Abstracts of the Gunma Conference of the Society of Chemical Engineers (1988), p. 21B). Note that the polarity of the high-voltage electric field pulse can be positive or negative, and either can be used in the present invention.

(b) Electrode The type of electrode (for example, platinum, stainless steel, graphite, etc.) can be selected as long as the desired high-voltage electric field pulse can be applied.
There are no restrictions on the shape (for example, cylindrical, plate-like, wire-like, needle-like), size, or immersion position (for example, the distance between electrodes). However, since sterilization is actually carried out only in the area where the high-voltage electric field pulse is applied between the electrodes, these conditions must be selected so as to obtain the desired sterilization effect.

A preferable electrode in this invention is a coaxial double cylindrical electrode as shown in FIG. In this embodiment, a wide bubble reservoir (bubble removal) is provided between the electrodes at the top, and the beverage liquid can be continuously supplied between the electrodes to facilitate sterilization.

(c) Conditions for application of high-voltage electric field pulses In order to obtain the desired sterilizing effect with the high-voltage electric field pulses specified in (a), various application conditions, such as the number of applied pulses, are set. It is known that the killing characteristics of baker's yeast by the application of high-voltage electric field pulses are approximated to the Weipul distribution [Akira Mizuno et al.: Abstracts of the Gunma Conference of the Society of Chemical Engineers (1988) p. 211 and Mizuno et al. Akira et al.: Collection of lecture abstracts of the National Conference of the Institute of Electrical Engineers of Japan (1986), p. 709)
.

As for this application condition, if the bactericidal effect against each target germ is determined in advance in a preliminary experiment, the result will be derived from an experimental formula, so the various conditions to obtain the desired bactericidal effect can be determined by using that formula. It can be set arbitrarily within the range.

〔Effect of the invention〕

According to this invention, it is possible to sterilize bacteria in a beverage liquid without impairing the quality of the beverage, and it is also possible to reduce running costs in terms of energy, which is economical. By using a sterilization tank having coaxial double cylindrical electrodes, which is a preferred embodiment of the present invention, sterilization can be carried out by continuously supplying beverage liquid between the coaxial double cylindrical electrodes. Efficiently prevent bacterial contamination in the process.

〔Example〕

Reference Example A preliminary experiment was conducted on the relationship between the number of applied pulses and the survival rate of microorganisms when high-voltage electric field pulses were applied.

Here, we will use a coaxial double cylindrical electrode as shown in Figure 1 (outer cylinder inner dimensions: length 500 mm x inner diameter 60 + + + m x thickness 5 m).
m, inner cylinder outer dimensions, length 400+nm x outer diameter 50mm x thickness 2. 5+nm, 5ynm between electrodes),
Sterilization was carried out using the system shown in the electrical circuit schematic diagram shown in FIG. 2 with an applied electric field strength of 30 kV/cm.

The survival rate results are shown in Figure 3. In addition, the sterilization conditions when carrying out the present invention may be set so that the necessary sterilization effect can be obtained based on these results.

In this figure, no - initial number of bacteria (cells/ml), n
= Number of bacteria after high-speed pulse discharge (cells/ml), n
/no=survival rate, α=number of applied pulses (480 pulses/min).

Example I Lactobacillus brevjs (I F
Beer with suspension of microbial cells (1.0 3345) (raw i number 1.
9X102eel Is/ml) in the same system and sterilization tank as in the reference example, electric field strength Er) = 20 k
V/cm, residence time 11 minutes, number of applied pulses 5280 (
High voltage electric field pulses were applied continuously at a rate of 480 pulses/min). As a result, Lactobacillus grows at the exit of the sterilization tank.
us brevis died with Oeel Is/ml,
This bactericidal effect could be stably maintained during continuous sterilization.

The quality of the beer was tested before and after sterilization by high-pressure 74+IA pulses, and the results are shown in Table 1 along with the tasting results. As shown in Table 1, no change in quality was observed due to pulse application.

Table 1 Beer quality items Before sterilization After sterilization Side wort extract ('P) 11.0 1L, 0 Appearance extract ('P) 1.8 1.8α-Amino nitrogen (mg/l) 67, 67 Alcohol ( V/V%) 4.5 4.5 Chromaticity (
EBCunit) 8.0 B, 0
Tasting (blind number of correct answers) - No significant difference Example 2 Enterobacter aerogenes (I
FO1-3534) wort suspension (sugar content 11°P1 viable cell count 1.2 x 102 cells/
ml) in the same system and sterilization tank as in the reference example, electric field strength Ep = 20 kV/cm s residence time 11 minutes,
High-voltage electric field pulses were continuously applied at a number of applied pulses of 5280 (480 pulses/min). As a result, at the exit of the sterilization tank, Enterobacter aerogenes
el Is/ml, and this bactericidal effect could be stably maintained during continuous sterilization.

The quality of the wort liquid was tested before and after sterilization by high-voltage electric field pulses, and the results are shown in Table 2. As shown in Table 2, no change in quality was observed due to pulse application. In addition, beer was obtained by brewing using the sterilized wort liquid. This beer also had no quality problems.

Table 2 Wort quality items Before sterilization After sterilization Sugar content ('P
) 11.0 11.0 α-amino nitrogen (mg/l) 1.41 141 Chromaticity (EBCunit) 1G, (]
16. Q Example 3 SaccharoMyces cerevisiae
(I F O0259) in red wine (number of viable bacteria 5°1 × 103 cells/m+) was heated in the same system and sterilization tank as in the reference example at an electric field strength of Ep = 15.
kV/cm, residence time 18.7 minutes, number of applied pulses 89
High voltage electric field pulses were applied continuously at 76 (480 pulses/min).

As a result, saccharomyces at the outlet of the sterilization tank
ccrcvisiac was killed at Oeel Is/ml, and this bactericidal effect could be stably maintained during continuous sterilization.

The quality of red wine was tested before and after sterilization by high-voltage electric field pulses, and the results are shown in Table 3 along with the tasting results. As shown in Table 3, no change in quality was observed due to pulse application.

Table 3 Red wine quality items Before sterilization After sterilization Alcohol (
V/V%> 12.5 12.5 Total nitrogen (mg/l) 205 205 Acidity (g/I) 5.3 5.3 Tasting (number of blind correct answers) - No significant difference Example 4 Saccharomyces diastaticus
Grape juice (IF 01046) suspension of bacterial cells (sugar content 23%, number of viable bacteria 4.5 x 103ce)
lls/ml) in the same system and sterilization tank as in the reference example, electric field strength Ep = 15 kV/cIIls residence time 1
8.7 minutes, number of applied pulses 8976 (480 pulses/min)
A high-voltage electric field pulse was continuously applied. As a result, at the outlet of the sterilization tank, Saccharomyces djasta
ticus died with Oeel Is/m+, and this bactericidal effect could be stably maintained during continuous sterilization.

The quality of the grape juice liquid was tested before and after sterilization by high-voltage electric field pulses, and the results are shown in Table 4. As shown in Table 4, no change in quality was observed due to pulse application. In addition, wine was obtained by brewing using grape juice after sterilization.

This beer also had no quality problems.

Table 4 Grape juice quality items Before sterilization After sterilization Sugar content ('P)
, 23.0 23.0 acidity (g
/I) 4.0 4.0 Example 5 Lactobacillus Ius homohioch
i (H-42, kindly provided by the Department of Fermentation, Department of Agricultural Chemistry, Faculty of Agriculture, University of Tokyo) was suspended in sake (number of viable bacteria: 2.9).
x 10' cells/ml) in the same system and sterilization tank as in the reference example, with electric field strength Ep = 50 kV/
cm, residence time 5.2 minutes, number of applied pulses 2496 (4
High voltage electric field pulses were applied continuously at a rate of 80 pulses/min). As a result, at the exit of the sterilization tank, LacLobacillus
s homohjochj was killed with Ocel Is/ml, and this bactericidal effect could be stably maintained during continuous sterilization.

The quality of the sake was tested before and after sterilization by high-voltage electric field pulses, and the results are shown in Table 5 along with the tasting results.

As shown in Table 5, no change in quality was observed due to pulse application.

Table 5 Sake quality items Before sterilization After sterilization Sake level
+9+9 Acidity (g/I) 2.5 2.
5 amino acid content (g/I) 2.3 2
．． 3 original extract (%) 30.0 30
．． 0 Alcohol (V/V%) 12.5
12.5 Authentic Extract (%) 4.3
' 4.3 Tasting (Number of blind correct answers) - No significant difference Example 6 Bacillus megaterium (I P
Carbonated drink containing suspended bacteria (number of viable bacteria: 2.0 3003).
I
/cm2, residence time 9.4 minutes, number of applied pulses 4498 (
High voltage electric field pulses were applied continuously at a rate of 480 pulses/min). As a result, at the exit of the sterilization tank, Bacillus me
gaterium died at Oeel Is/ml, and this bactericidal effect could be stably maintained during continuous sterilization.

The quality of the carbonated beverages was tested before and after sterilization by high-voltage electric field pulses, and the results are shown in Table 6 along with the tasting results. As shown in Table 6, no change in quality was observed due to pulse application.

Table 6 Carbonated beverage quality items Before sterilization After sterilization Soluble solids (' Br1x) 9.5 9.5 Acidity (g
/l) 0.8 0.8 tasting (
Number of blind correct answers) - No significant difference Example 7 Enterobacter aerogenes I
Fruit juice drink in which bacterial cells of F 0 135 B 4 are suspended (70% tangerine juice, number of viable bacteria 1, 2 x 102c)
cells/ml) in the same system and sterilization tank as in the reference example, electric field strength Ep = 10 kV/cm, % residence time 22.0 minutes, number of applied pulses 10560 (480 pulses/ml).
High-voltage electric field pulses were applied continuously (minutes). the result,
Enterobacter aerolog at the exit of the sterilization tank
enes was killed to Oeel Is/ml, and this bactericidal effect could be stably maintained during continuous sterilization.

The quality of the fruit juice beverages was tested before and after sterilization by high-voltage electric field pulses, and the results are shown in Table 7 along with the tasting results. As shown in Table 7, no change in quality was observed due to pulse application.

Table 7 Fruit juice beverage quality items Before sterilization After sterilization Soluble solids ('Br1x) 12.0 12.0 Acidity (g
/I) 5.5 5.5α-amino nitrate (mg/l) 170 170 tasting (number of blind correct answers) - No significant difference

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of the sterilization tank used in the example, Figure 2 is a schematic diagram of the electric circuit of the device used in the example, and Figure 3 is
FIG. 2 is a diagram showing the relationship between the number of applied pulses and the survival rate of microorganisms. R1, R2, R3'' High voltage resistance, c,, c,,,. Capacitor (Cp is for discharge control), 1...Slidac, 2...High voltage transformer, 3.
...High voltage rectifier, 4...Copper plate, 5...Spark gap, 6...Sterilization tank (capacity 300m1), 7...
Earth wire, 11... Outer tube electrode, 12... Inner tube electrode,
13... Sterilization tank, 14... 0 ring Applicant's representative Mr. Sato Figure 1 Figure 2

Claims (1)

[Claims] 1. Applying high-voltage electric field pulses to the beverage liquid at 2 kV/cm to 1
Electric field strength when applying a pulse of 00 kV/cm, 20 nse
c~1μsec pulse waveform rise, 100nsec
A method for sterilizing beverage liquids, characterized in that application is performed with a pulse waveform width of c~1 msec. 2. The method according to claim 1, wherein a high voltage electric field pulse is applied between coaxial double cylindrical electrodes. 3. The method according to claim 2, wherein sterilization is carried out by continuously supplying a drinking liquid between coaxial double cylindrical electrodes.