JP2002207025A - Freshness measuring method for fishes - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive measuring method capable of simply evaluating the freshness of fishes on the spot in a short time regardless of the presence and kind of freezing. SOLUTION: An electrode is inserted in the meat texture of fishes or the juice squeezed from the meat texture of fishes and oxidation-reduction potential is measured to decide the freshness of fishes capable of being eaten raw.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring freshness of fish. More specifically, the invention of this application inserts an electrode into the juice of fish meat tissue or fish meat tissue, measures the oxidation-reduction potential, and determines freshness that can be eaten quickly, and It relates to a simple freshness measuring method.

[0002]

2. Description of the Related Art In the early stage after fish are caught, oxygen supply is cut off, and glycolysis, protein denaturation, protein degradation, lipid oxidation, etc., proceed at different rates in meat tissue, resulting in bacterial growth. In addition, various enzymes produced by bacteria are involved in various biochemical reactions, resulting in a decrease in freshness (Etsuo Watanabe, Ed., "Freshness and Processing and Storage of Seafood", No. 6,
3 pages, Seizando Bookstore, date of issue unknown). For example, in raw fish meat to be served for sashimi, the degree of reduction in the initial freshness of fish meat at the distribution stage is important.

Conventionally, as a quantitative evaluation method of freshness of fish,
In Japan, a method based on the K value using the change of the ATP-related substance as an index is widely used, and it is generally said that if the K value is 20% or less, it can be eaten raw. For the measurement of the K value, ATP-related substances must be quantified by high performance liquid chromatography or the like, and there is a disadvantage that it cannot be measured unless a well-equipped laboratory is used. Quantification of related substances has been simplified.

However, the degree of change in the K value varies depending on the type of fish. For example, in Thailand, even though the K value hardly changes, rot may progress, and this method is applied to all fish types. I can't.
This evaluation method is also used for measuring beef ripeness (Japanese Patent Application Laid-Open No. H5-119033).

[0005] On the other hand, overseas, a freshness sensor has been developed in the United Kingdom that uses a change in the dielectric constant of fish meat as an index. This method makes use of the fact that the dynamic properties of water in fish meat change with a decrease in freshness. However, in the case of frozen-thawed fish, the water condition is different from that of non-frozen fish, and the measured values are significantly different. There is.

[0006] In addition, as a freshness index of fish and its measuring method, there are a method for measuring volatile basic nitrogen, a method for measuring trimethylamine, a method for measuring polyamines,
There are known methods for measuring organic acids, sensory test methods, viable cell count measurement methods, measurement methods using a buffer capacity sensor, measurement methods using a non-destructive freshness sensor, etc. (edited by Etsuo Watanabe,
"Freshness and Processing and Storage of Seafood", pp. 65-76,
Seizando Shoten, date of issue unknown), no evaluation method for measuring oxidation-reduction potential has been hitherto known.

[0007]

The quality of freshness in distribution of fresh fish, especially for fresh food, is an important factor in determining fish prices. It would be desirable if it could be easily determined on the spot whether or not fresh food could be purchased or sold with a mass retailer such as a supermarket or supermarket in the fish market, or with a consumer at a store. Also, in the manufacture of surimi products, dried products, etc., it may be necessary to adjust the process depending on the freshness of the raw fish, if the freshness of the fish can be easily evaluated,
The process can be standardized, and the advantage is great.

In view of the prior art as described above, the inventors of the present application have intensively studied a method for easily and quickly evaluating the freshness of fish regardless of the presence or absence of freezing and the type thereof. As a result, it was found that the oxidation-reduction potential of meat tissue increases with time due to various biochemical changes from immediately after the death of fish to the early stage of putrefaction.

The invention of this application provides a method that can easily and quickly evaluate the freshness of fish from a part of fish meat tissue or the juice of fish meat tissue on site based on such knowledge. That is the task.

[0010]

Means for Solving the Problems To solve the above problems, the invention of the present application is to insert an electrode in fish meat tissue or juice of fish meat tissue, measure the oxidation-reduction potential, and determine the freshness that can be eaten raw. A method for measuring the freshness of fish, characterized in that the freshness of freshly edible fish is about 0.3
Methods are also provided that assume an oxidation-reduction potential of 7 V or less, and that the electrodes have a temperature compensation sensor and a pH compensation sensor.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The implementation of the invention of this application is extremely simple and does not require special techniques. It is only necessary to insert an electrode into the meat tissue of the fish whose freshness is to be measured or into the juice extracted from the meat tissue and measure the oxidation-reduction potential by a conventional method. As shown in FIG. 1, for example, an apparatus for measuring the oxidation-reduction potential includes an electrode, a lead wire connecting the electrode and the measuring device, and a measuring device, and a commercially available product can be used. Also, to measure the oxidation-reduction potential more accurately,
It is desirable to provide a temperature correction sensor and a pH correction sensor on the electrode.

This is because it is known that the oxidation-reduction potential (ORP) depends on temperature and pH from the physicochemical definition. For example, without temperature compensation,
The variation may increase depending on the outside air temperature and the product temperature. However, if a temperature standard at the time of measurement is set, the temperature correction sensor is not necessarily required. Regarding pH, in general, in the case of fish meat, pH fluctuation is observed at a very early stage (3 or 4 hours after death), but practically almost no pH fluctuation occurs when the freshness decreases over a longer time. Is not seen. Therefore, the pH correction sensor is not always required.

When an electrode is inserted into the collected meat tissue, a hole almost identical to the electrode is provided in the meat tissue, an electrode for measuring the solid surface is inserted into the hole, and the oxidation-reduction potential is measured. When measuring juice squeezed from the collected meat tissue, a normal electrode is inserted into the juice and the oxidation-reduction potential is measured. In any case, it is a simple operation only to read the value of the oxidation-reduction potential displayed on the measuring instrument,
The measurement is completed in a short time of about 3 minutes. For more accurate evaluation, it is desirable to collect some samples, measure the oxidation-reduction potential, and calculate the average value.

As shown in the test examples described below, the inventors measured changes in the oxidation-reduction potential of various fishes from immediately after death to the beginning of putrefaction. As a result, regardless of the type of fish and the storage temperature of the fish, the oxidation-reduction potential gradually increases immediately after death, and is usually about 0.35 to 0.37 V
It was found that the maximum value was reached and gradually decreased thereafter.

[0015] The inventors compare the freshness evaluation method which has been conventionally carried out with the method of the invention of this application, and the period until the measured value of the oxidation-reduction potential reaches the maximum value is the period during which the fresh food can be eaten. Thus, a new method for evaluating freshness was completed. Therefore, the second invention of this application is characterized in that the freshness that can be eaten raw is determined at an oxidation-reduction potential of about 0.37 V or less. Here, "about" means
Common sense includes the range of ± 0.01V.

In practicing the invention of this application, it is desired to determine whether the measured oxidation-reduction potential (ORP) is before or after reaching a maximum value (peak potential). This determination can be made, for example, by any of the following methods.

(A) Since an odor comes out sensuously when the peak is exceeded, it is determined in combination with an odor sensor, a trimethylamine concentration sensor, or a sensor that captures the same quality characteristics after the appearance of the peak.

(B) As a trend, if a time differential value of the oxidation-reduction potential can be calculated, the difference before and after the peak is judged as plus or minus.

Next, the invention of this application will be described in detail with reference to test examples. <Test Example 1> This test was performed to examine the relationship between the oxidation-reduction potential of yellowfin tuna and yellowtail and the storage period, storage temperature, and pH. (1) Preparation of Samples Yellowfin tuna 5 and yellowtail 7 purchased from Tsukiji Market were used. Samples before storage were collected from each of the yellowfin tuna and yellowtail crusts, and the rest were directly sealed in polyethylene bags and stored in refrigerators at 0, 5 and 10 ° C. 1 day, 2 days, 4 days, 6 days and 7 days after storage for yellowfin tuna, 5 hours, 10 hours, 25 hours, 60 hours and 80 hours after storage for yellowtail
After hours, 160 hours and 180 hours, samples were taken from each frog. (2) Test method Commercially available portable measuring device TOKO ph / OR shown in FIG.
Using P (Tokyo Chemical Laboratory “TPX-90i” (with temperature compensation sensor built-in type)), each sample collected was drilled with a cork borer into a fish meat with a solid surface with a diameter and depth of about 1 cm. Measuring the oxidation-reduction potential
The average value of 5 samples collected for yellowfin tuna and 7 samples collected for yellowtail was calculated and tested. still,
In order to measure accurately, the electrodes were inspected with a quinhydrone solution (standard solution) before the measurement. (3) Test results The test results are as shown in FIGS. 2 and 3, the left vertical axis represents the oxidation-reduction potential: ORP (V),
The right vertical axis indicates the pH, and the horizontal axis indicates the storage period.
° C, the dashed line indicates the storage temperature of 5 ° C, and the dotted line indicates the storage temperature of 10 ° C. In each drawing, the average value, the maximum value, and the minimum value are shown.

As is clear from FIG. 2, in the case of yellowfin tuna, the pH changes with the storage period at each storage temperature were small, and the oxidation-reduction potential increased with the storage period at each storage temperature, and reached a maximum at about 0.37 V. And decreased with increasing storage time. The time to reach the maximum value is different at the storage temperature, when the storage temperature is 10 ° C, after 2 days,
At 0 ° C. and 5 ° C., after 4 days. From these results, it was found that in the yellowfin tuna, at a storage temperature of 10 ° C., the edible period is two days later, and at the storage temperatures of 0 ° C. and 5 ° C., the edible period is four days later.

Further, as is apparent from FIG. 3, the case of yellowtail is the same as that of yellowfin tuna, with little change in pH due to the storage period at each storage temperature, and the oxidation-reduction potential increases with the storage period at each storage temperature. , Approx.
It reached a maximum at 35-0.37V and decreased with increasing storage time. The time to reach the maximum varies with storage temperature, 25 hours at 10 ° C, 0 ° C and 5 ° C.
Then it was 125 hours later. From these results, it is 1 in yellowtail
At the storage temperature of 0 ° C., it was found that the period of up to about 1 day was the period during which it was possible to eat, and at the storage temperatures of 0 ° C. and 5 ° C., up to 5 days afterwards, the period during which it was possible to eat. <Test Example 2> This test was performed to examine the relationship between the oxidation-reduction potential of Thai and Japanese flounder, storage period, and pH. (1) Preparation of samples Purchase 9 live fish of Thailand and Japanese flounder from Tsukiji Market, kill them immediately, collect samples from the back meat before storage, put the rest as they are in polyethylene bags and seal them, 5 ℃
5 hours, 10 hours, 25 hours, 40 hours, 70 hours, 90 hours, 120 hours, 160 hours and 180 hours after harvesting the back meat from each fish body And used as a sample. (2) Test method A test was performed by the same method as in Test Example 1. (3) Test results The test results are as shown in FIG. In FIG. 4, the left vertical axis indicates the oxidation-reduction potential (V), the right vertical axis indicates the pH, and the horizontal axis indicates the storage period. The lower line shows the pH. In the drawings, the average value, the maximum value, and the minimum value are shown.

As is apparent from FIG. 4, in all the fishes, the change in pH with the storage period at each storage temperature was small, and the oxidation-reduction potential increased with the increase in the storage period, and reached the maximum at about 0.37 V. , Decreased due to an increase in the storage period. The time to reach the maximum was about 100 hours after in any fish. From this result, it was found that in the case of flounder and Thailand, the storage edible period was about 4 days after storage at 5 ° C. <Test Example 3> In this test, K is a conventional freshness evaluation method.
This was done to compare the values with the method of the invention of this application. (1) Preparation of Sample The same sample as in Test Examples 1 and 2 was used. (2) Test method The K value was calculated from the results measured by a conventional high performance liquid chromatography and tested.

As the values measured by the method of the present invention, the values of Test Examples 1 and 2 were used. (3) Test Results FIGS. 5 to 7 show the correlation between the test results and Test Examples 1 and 2. In each figure, the vertical axis represents the K value,
The horizontal axis indicates the oxidation-reduction potential. In FIGS. 5 and 6, the solid line indicates 0 ° C., the dashed line indicates 5 ° C., and the dotted line indicates the storage temperature of 10 ° C.
In FIG. 7, a solid line indicates a tie and a dotted line indicates a flounder. Note that the scale of the vertical axis in FIGS. 5 and 6 is different from that in FIG.

As is clear from FIGS. 5 to 7, the oxidation-reduction potential increases with the K value at the beginning of storage and then decreases. The K value, which is the limit of raw food, differs depending on the type of fish, and is around 20% for tuna and 30 for yellowtail.
It is said to be around%.

On the other hand, in Thai and flounder, the K value did not increase even if the storage period increased, and as is clear from FIG.
The change in the K value is remarkably small as compared with other fishes, and it is clear that the K value is not an index of freshness evaluation in these fishes. From the above results, it was found that the method of the present invention was extremely effective for freshness evaluation.

Next, an embodiment will be shown and described in more detail.

[0027]

<Example 1> The freshness of yellowfin tuna purchased from Tsukiji Fish Market was measured using a commercially available portable measuring device TOKO.
The measurement was performed in the same manner as in Test Example 1 except that ph / ORP was used and stored in a refrigerator at 6 ° C. As a result, it was found that the oxidation-reduction potential reached 0.37 V after 4 days, and that it was possible to eat raw food. <Example 2> Freshness of yellowtail purchased from a supermarket in Tokyo was measured in the same manner as in Test Example 1 except that it was stored in a refrigerator at 6 ° C using a commercially available portable device TOKOph / ORP. did. As a result, it was found that the oxidation-reduction potential reached 0.37 V after 60 hours, and that it was possible to eat raw food. <Example 3> Back meat is collected from live flounder purchased from Tsukiji Market, and its freshness is measured using a commercially available portable measuring device TOKO p.
The measurement was performed in the same manner as in Test Example 1 except that h / ORP was used and stored in a refrigerator at 6 ° C. as a result,
After 90 hours, the oxidation-reduction potential reached 0.36 V, indicating that it was possible to eat raw food.

[0028]

As described above in detail, the invention of this application relates to a method for measuring the freshness of fish, and the effects achieved by the present invention are as follows.

1) Regardless of the type of fish, the freshness of the fish can be easily measured.

2) Freshness of fish can be easily measured irrespective of the condition of the fish such as freeze-thaw.

3) The apparatus for measuring the oxidation-reduction potential is small,
Lightweight.

4) The measurement of the oxidation-reduction potential can be performed in a short time without requiring any special technique.

5) It is possible to automate and standardize the determination of freshness of fish requiring skill.

[Brief description of the drawings]

FIG. 1 shows an example of an oxidation-reduction potential measuring apparatus for carrying out the invention of this application.

FIG. 2 shows the storage temperature, storage period, and storage time of yellowfin tuna.
4 shows the relationship between oxidation-reduction potential and pH.

FIG. 3 shows the relationship between storage temperature, storage period, oxidation-reduction potential, and pH of yellowtail.

FIG. 4 shows the relationship between the storage period, redox potential and pH of Thai and Japanese flounder.

FIG. 5 shows the correlation between the K value of yellowfin tuna and the oxidation-reduction potential.

FIG. 6 shows a correlation between yellowtail K value and oxidation-reduction potential.

FIG. 7 shows the correlation between the K value of Thai and Japanese flounder and redox potential.

[Explanation of symbols]

 1 sample 2 electrode 3 lead wire 4 measuring instrument

Claims (3)

[Claims] 1. A method for measuring freshness of fish, comprising inserting an electrode into fish meat tissue or juice of fish meat tissue, measuring an oxidation-reduction potential, and judging freshness of fish that can be eaten. 2. The method for measuring freshness of fish according to claim 1, wherein the freshness of the fish that can be eaten has an oxidation-reduction potential of about 0.37 V or less. 3. The method according to claim 1, wherein the electrode has a temperature correction sensor and a pH correction sensor.