JP2003215097A - Method and apparatus for measuring freshness of food - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To increase ORP sensitivity in an ORP meter to the freshness of food to utilize the simple ORP meter as a freshness-measuring apparatus for the food, and to decrease an error in measurement. <P>SOLUTION: Perishable food surrounds a portion around a platinum pole being the sensitive electrode of an ORP meter by a gas permeation film for permeating only a multicomponent gas such as oxygen and hydrogen dissolving in a food constituent, and an ORP value of the multicomponent gas is detected, thus increasing the sensitivity of change in ORP due to deterioration in the freshness of the perishable food. Additionally, two platinum electrodes are set to be the sensitive electrode, one platinum electrode is surrounded by the gas permeation film, and the potential of the platinum electrode at an exposure side is detected with the platinum electrode that is surrounded by the permeation film as a reference voltage, thus reducing variation in the error of ORP, and further obtaining freshness information according to the change rate of the ORP value due to a factor other than a dissolved gas constituent. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an apparatus for quantitatively and hierarchically determining the freshness of fresh food such as vegetable meat. Further, the present invention can be utilized as an apparatus for quantitatively determining the activity of general living cells such as humans and animals.

[0002]

2. Description of the Related Art Judgment of freshness of fish meat, livestock meat, etc. is the basis for judging the quality of meat. The K value is recognized as one of the criteria for food freshness determination, which is difficult to objectively determine. The K value is the ATP concentration of the muscle component of meat and the ATP concentration.
Is calculated from the ratio of changed amino acid concentrations, and is currently used by companies, food inspections, and research institutions that treat meat as a value that is closest to the freshness index of meat. However, the determination of freshness based on the K value is a spectroscopic analysis and measurement of molecular components contained in muscles that are foods, is a large-scale device, requires skill to operate, and has a difficulty in installation cost. As a method that is slightly easier than the K value measurement, there are a method of measuring the amount of histamine and ammonia in meat, a method of measuring the concentration of spoilage gas in the air generated in the spoilage denaturation process, and the like. However, these methods also have a problem in terms of handling and cost because they take a long time for measurement and the measurement is based on extraction of a specific molecular component.

On the other hand, there is an attempt to use a commercially available oxidation-reduction potentiometer to measure the oxidation-reduction potential of food as a criterion for freshness because it is inexpensive as a measuring device and is easy to operate. For example, Japanese Patent Laid-Open Publication "Food quality determination method and food oxidation-reduction potential measurement method: Japanese Patent Laid-Open No. 08-136500" shows a case where the oxidation-reduction potential of vegetables decreases with time. Further, according to the published patent publication "Redox potential measuring function visceral health care analyzer: Japanese Patent Laid-Open No. 09-327443", the possibility of determining the freshness of foods as well as the method of determining the activity of a general living body by measuring the redox potential is doing. However, the oxidation-reduction potential measurement is generally susceptible to the sample aqueous solution and the outside air gas, and especially the mixing or disappearance of oxygen gas in the atmosphere having high oxidation activity has a significant adverse effect on the measurement accuracy. In addition, since the measurement error is large due to the electric disturbance element, it has not reached the practical range as a freshness measuring instrument.

[0004]

[Problems to be Solved by the Invention] Oxidation-reduction potentiometer (hereinafter referred to as ORP meter) characterized by its simplicity and low cost
There are many problems to be solved before it can be used as a freshness determination device. FIG. 1 is an example of a measured value showing a change with time of a redox potential (hereinafter referred to as ORP) of tuna meat representing fish meat. The initial value shows immediately after thawing, and thereafter the room temperature is fixed at 25 degrees Celsius in order to accelerate the deterioration of freshness.
According to FIG. 1, the ORP value of tuna meat starts from about 0 millivolt when fresh and clearly shows a spoilage state.
It shows a monotonous decreasing tendency up to minus 350 millivolts after the elapse of time. This tendency shows the correlation between the freshness level and the ORP value, and suggests the possibility of utilizing the freshness meter of the ORP meter. However, it is understood that the freshness determination by the ORP meter has not reached the practical range due to the following reasons.

In the measurement result of FIG. 1, there is no external disturbing change in the measurement value because the measurement probe is fixed to the tuna meat to be measured during the measurement period, and the probe is not actually measured. Since the probe is constantly reattached to a new sample, the measured value of the probe is not stable and shows a fluctuation range above a certain level. That is, generally, in ORP measurement of food, an error occurs between the measured values depending on the shape of the measuring probe and the sampling method of the sample, and the value may be from plus or minus 20 millivolts to plus or minus 50 millivolts or more. Further, the ORP measurement basically needs to be carried out in an aqueous solution system, and for food whose surface is dried or whose water content is low, it is necessary to partially collect a sample and dissolve it in some water. For this reason, O
A change in RP causes an error of plus or minus 50 millivolts or more even if the same sample is used. Furthermore, the meat to be measured has an individual-specific difference in the initial value of ORP not only between different kinds of meat but also between different kinds of meat, and this difference in basic value cannot be distinguished from the measurement error. .
According to the measurement by the present inventor, the electrode potential of fresh fish meat against silver / silver chloride is from -50 millivolts to +150 millivolts.
It is in the millivolt range, and it is about 2 depending on the fish species and measurement site.
There is a width of 00 millivolts. The individual difference of the same kind of fish meat is plus or minus 20 millivolts. If the above-mentioned error factors are added, even if the same type of meat is to be measured, it is necessary to consider plus or minus about 70 to 80 millivolts as a fixed measurement error in ORP measurement.
On the other hand, in order to increase the number of levels of freshness classification as freshness information, it is necessary to increase the ratio between the sensor sensitivity and the measurement error. From this point of view, the ORP value fluctuation range of FIG. If the measurement error is 160 millivolts and the width of the measurement is 160 millivolts, the number of layers becomes two or less, and the sensor has almost no meaning. Take fish meat as an example of the freshness evaluation method. B, ready to eat as live fish. B, raw food is delicious. Ha, ready to eat raw. D, heated and delicious. E, heated and edible. F, inedible. Toxicity. Considering that a total of 7 layers are usually required, and at least 5 layers are required. Sensitivity must be more than twice the current level, or measurement error must be less than half.

[0006]

[Means for Solving the Problem] Among plastic thin films, a thin film based on polyethylene, Teflon (registered trademark), etc., which is a non-polarizable polymer, has a property of easily passing a low-molecular gas. There is. For example, the Clark oxygen sensor combines a Teflon membrane and an oxygen-selective thin film to selectively permeate oxygen, and applies a negative voltage from the outside to generate a reducing current proportional to the oxygen concentration to determine the oxygen concentration. It is a device.

Since the gas component that permeates the polyethylene thin film exhibits a unique ORP value according to its composition ratio, the present inventor changes the ORP value with time of the permeated gas in a diffusion equilibrium state with the dissolved gas of tuna meat. When measured, Figure 2
It was found that there is a tendency represented by curve B (hereinafter referred to as B value) in the graph. A curve represented by A in the figure (hereinafter referred to as A value) is the same as that in FIG. That is, the ORP value of an aqueous solution in which gas components of relatively low molecular weight such as oxygen gas, hydrogen gas, carbon dioxide gas, ammonia gas, etc., which are presumed to have permeated through the permeable membrane, rapidly decrease at room temperature, and the initial value plus 12
From 0 millivolts, it turned out to drop to minus 520 millivolts at the end of the rotting state after 12 hours. This fluctuation range is 640 millivolts, which is almost twice the fluctuation range of the ORP value of the fish meat itself. Especially, the fluctuation range more than doubled in the period of 6 hours before, when the freshness seems to be relatively high. This effect means that the freshness sensitivity as a sensor is doubled, and it becomes possible to classify 5 or 6 layers in the entire area. In particular, in the high freshness region, it enables three-level classification. According to the measurement by the inventor, the improvement of the ORP sensitivity of the permeated gas-dissolved liquid is not limited to fish meat including tuna meat, but is common to almost all meats such as chicken and livestock.

The cause of the difference between the A value and the B value can be considered as follows. Among foods, fresh food represented by meat has a large amount of dissolved oxygen, and the potential due to dissolved oxygen is dominant to the ORP value, but the ORP value decreases due to reducing components in the meat. That is, in the fresh state of meat, both dissolved oxygen and reducing components are in the active state, and even in the process of losing activity over time, the oxidation potential due to dissolved oxygen and the reducing component It is in a state of competing with the reduction potential. Therefore, since the apparent potential change appears as the sum thereof, the time variation width of the A value becomes small. On the other hand, regarding the B value, since the reducing component that does not permeate the permeable membrane does not contribute, the effect of reducing the dissolved oxygen amount directly appears, and as a result, the fluctuation range becomes large. As a factor contributing to the improvement of the sensitivity of the B value, in addition to the decrease of the dissolved oxygen amount, the increase of the permeation gas components such as hydrogen and ammonia can be mentioned. As the freshness decreases, the concentration of hydrogen or ammonia, which is a reducing substance, increases and acts on the side where the ORP value decreases, so that the sensitivity range further increases.

In order to facilitate understanding of this mechanism of action, the difference between the A value and the B value is plotted on the same graph as the curve C (hereinafter referred to as the C value) in FIG. C value is ORP of the whole food
Since it is the value obtained by subtracting the ORP value of the food gas component from the value, it means the ORP value of substances that do not permeate through the permeable membrane, such as food proteins, minerals, enzymes and ionic substrates, and it is a reducing substance even at the time of high freshness. It seems that the reduction potential of is dominant. Therefore, as a tendency of the C value to change with time, the initial value maintains a reduction potential of −200 millivolts, gradually increases in the intermediate stage and shows an increasing tendency, and in the final stage, the oxidation state after oxidation becomes plus 150. Keep a constant value in millivolts. Since the respective changing tendencies of A, B, and C show the same tendency regardless of the type of meat, this movement is schematically shown in FIG. That is, it is roughly classified into three layers: an aging period which is an auto-digestion period that causes a change in freshness, a metamorphosis period which is a start period of internal oxidation and spoilage, and a spoilage period in which microbial spoilage proceeds. The meaning of the C value is that the reducing substance inside the food is finite and the reducing substance disappears and changes into an oxidizing substance over time.

FIG. 4 is an equivalent circuit showing the relationship between the ORP of food and the dissolved gas ORP related to food components. A of FIG. 4 represents the ORP of the food, and indicates that the ORP is composed of the non-gas component M and the gas component G of the food via the reference potential R. B of FIG. 4 represents the ORP caused by the dissolved gas component of the food, and indicates that the ORP is composed of only the gas component G of the food via the reference potential R.
C in FIG. 4 means a circuit that takes out the difference between the circuit A and the circuit B, and indicates that the reference potential R is unnecessary. The circuits A, B, and C have the above-mentioned A value, B value, and C, respectively.
Corresponds to the circuit that gives the measured value of

FIG. 5 is an explanatory diagram of the basic structure of the food freshness measuring apparatus according to the present invention. FIG. 5A is a basic diagram of a conventional general ORP meter and corresponds to the equivalent circuit A of FIG. 5 and 5B show a basic structure of the freshness measuring device according to claim 1 of the present invention, and an equivalent circuit B of FIG.
Corresponding to. 5 and C show the basic structure of the freshness measuring device according to claim 2 of the present invention, and correspond to the equivalent circuit C of FIG.

In the invention of claim 1, when the basic configuration of the present invention is shown in FIG. 5 and B, 1 is a food to be measured. 2 is a platinum plate which serves as a sensitive electrode. 3 is
It is the liquid junction of the reference electrode. Reference numeral 4 denotes a housing that holds the sensitive electrode and the reference electrode liquid junction in parallel or concentric form. 5 is
A casing is provided with a permeable membrane that selectively permeates and absorbs dissolved gases such as oxygen, hydrogen, and ammonia contained in food ingredients, and an aqueous solution containing these dissolved gases as solutes therein. 6
Is a cylindrical housing that contains the sensitive electrode lead wire, the reference electrode, the electrolytic solution, and the reference electrode lead wire, and holds them.
Reference numeral 7 is a two-core lead cable for connecting the electrodes 2 and 3 to a voltmeter included in the ORP display device 8.

According to the second aspect of the present invention, when the basic configuration of the present invention is shown in FIGS. 5 and C, it includes a platinum plate 2-1 that is in direct contact with food, a gas permeable membrane and an aqueous solution. The platinum plate 2-2 surrounded by the housing 5 is used as a counter electrode, and the lead wire 7 having two cores is directly connected to the counter electrode, which is connected to a voltmeter included in the ORP display device 8.

[0014]

According to the invention described in claim 1, the dissolved gas component of the food is non-selectively extracted by the gas permeable membrane, and the ORP value of the dissolved gas component is measured to obtain the ORP due to the decrease in freshness. By increasing the value fluctuation range and increasing the sensitivity, it has become possible to determine the freshness level of foods by ORP, which was previously impossible.

According to the invention described in claim 2, without using the reference electrode requiring maintenance such as the electrolytic solution,
By using a set of platinum plates and a set of gas permeable membranes,
A method and apparatus capable of determining the freshness level of food. Thus, it is possible to provide an inexpensive food freshness measuring device that is easy to operate. Further, the device according to the present invention is not limited to fresh foods, but is attached to living epidermis, and the ORP values due to all the components that make up the biological fluid based on the ORP value of the dissolved gas component of the biological fluid that surrounds general biological cells. Since it is possible to indirectly observe the activity of enzyme components having strong oxidative or reducing activity contained in biological fluids, it is possible to evaluate the activity of general living cells and the strength of organ function. It will be a guide.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, an embodiment structure of the present invention will be described with reference to the drawings. FIG. 6 shows claim 1 of the present invention.
It is an appearance structure of an example concerning. 1 in FIG. 6 is a food to be measured. Reference numeral 4 is a housing that holds the sensitive electrode and the reference electrode liquid junction. 5 is oxygen contained in food ingredients,
The casing is provided with a permeable membrane that non-selectively permeates and absorbs dissolved gases such as hydrogen and ammonia, and an aqueous solution containing these dissolved gases as a solute. 6 is a sensitive electrode lead wire,
It is a cylindrical housing that includes a reference electrode, an electrolytic solution, and a reference electrode lead wire and holds them. Reference numeral 7 is a two-core lead cable that connects the potential between the reference electrode and the sensitive electrode to a voltmeter provided in the ORP display device housing 9 that outputs the liquid crystal ORP display surface 8. Reference numeral 10 is a switch for turning on / off the power supply and for display control.

FIG. 7 is an external structure of an embodiment according to claim 2 of the present invention. 2-1 is an exposed platinum plate, 2
Reference numeral -2 is a platinum plate covered with a polyethylene film 5, and a main body that incorporates a liquid crystal driver and a chipped microprocessor unit through a lead wire 7 in a holding portion 4 for a potential difference between both platinum electrodes caused by contact with food. Input to the electrometer input terminal of the plastic casing 9. The liquid crystal display unit 8 displays the ORP potential directly or as a symbol indicating the level of food freshness classified. Reference numeral 10 is a switch for setting a power source and a display mode.

Since the gas permeable membrane shown in this embodiment is a polyethylene membrane having relatively poor wear resistance, the permeable membrane portion is detachable and replaceable. Further, as shown in FIG. 8, the food 1 is covered with a bag-shaped polyethylene membrane 11 and an aqueous solution is added on the polyethylene membrane 11 for measurement, or the gas permeable membrane is a solid gas permeation of high durability that does not require replacement. Substitution with layers does not impair the spirit of the invention.

[Brief description of drawings]

FIG. 1 is a graph showing the change over time in the redox potential of tuna meat.

FIG. 2 is a graph showing the change over time in the redox potential of a tuna meat due to a dissolved gas.

FIG. 3 is a schematic diagram showing a change with time of redox potential of meat.

FIG. 4 is an equivalent circuit showing the relationship between the redox potential of food and the dissolved gas redox potential.

FIG. 5 is an explanatory view of the basic structure of a food freshness measuring device according to the present invention.

FIG. 6 is an embodiment of a food freshness measuring device according to claim 1 of the present invention.

FIG. 7 is an embodiment of the freshness measuring device for food according to claim 2 of the present invention.

FIG. 8 shows another embodiment of the food freshness measuring apparatus according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Food 2 Platinum plate 2-2 Platinum plate 3 covered with a permeable membrane 3 Liquid junction part 4 of a reference electrode Housing 5 holding an electrode 5 Gas permeable membrane and fitting housing 6 equipped with an aqueous solution inside 6 Electrolyte and reference Housing 7 for holding electrode lead wires, etc. 7-core lead wire 8 Liquid crystal display unit 9 Display device housing 10 Operation switch 11 Bag made of transparent film

Claims (2)

[Claims] 1. A permeable membrane that non-selectively permeates and absorbs dissolved gas components such as oxygen, hydrogen, and ammonia contained in food ingredients and an aqueous solution containing these dissolved gases as a solute, and oxygen near the permeable membrane, A method and an apparatus for measuring food freshness, characterized in that the freshness of food is determined by measuring the oxidation-reduction potential of a plurality of dissolved gas aqueous solutions derived from foods such as hydrogen and ammonia. 2. An oxidation-reduction potential caused by all the elements of a food ingredient and an oxidation-reduction potential caused by a plurality of dissolved gases such as oxygen and hydrogen ammonia contained in the food ingredient are independently detected to detect both potentials. A method and apparatus for measuring food freshness, characterized by determining the freshness of food from difference information.