JP2007225582A - Method for evaluating mercury amount contained in fishes, and producing method of farmed fish - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of evaluating an amount of mercury contained in a fish body without damaging the fish body as a commodity with a simple method. <P>SOLUTION: In the method of evaluating an amount of mercury contained in a fish, the mercury concentration contained in an edible part of the fish body is evaluated by analyzing the mercury concentration in the blood sampled by blood removal operation of the fishes or the muscle in disposed part of the fish by a known method. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for evaluating the amount of mercury contained in cultured fish or natural fish by a simple analytical method.

  In recent years, due to the deterioration of the global environment, especially polluted wastewater, the concentration of mercury in the water has increased due to water pollution of seawater, rivers, lakes, etc., and as a result, mercury in the water is taken up by plankton, etc. that inhabit the water. As a result of the successive enrichment of the food chain, a high concentration of mercury contamination occurs as it progresses to the top of the food chain. When fish containing such mercury in high concentration is used for food, there is a risk of causing pollution such as so-called Minamata disease.

  The Ministry of Health, Labor and Welfare in Japan has established a standard for the safety of mercury levels in edible fish, and in accordance with the Food Safety Act, for general fish, the total mercury content in the edible part of seafood (the total amount of mercury present in all compound forms) The provisional regulation value is set to 0.4 μg / g or less (concentration), and the regulation of the amount of mercury as methylmercury, which is particularly toxic and dangerous for humans, is 0.3 μg / g or less. It is legally stipulated that general fish containing excess methylmercury should be disposed of. However, tuna, marlin, skipjack, and deep-sea fish and shellfish have high mercury levels, but for consumers, they are out of regulation because they consume less.

  For tuna such as bluefin tuna, these fish species are located at the top of the food chain, and as a result, the mercury contained in the ingested diet is gradually concentrated, resulting in the mercury concentration in the edible part of naturally occurring tuna Although it varies depending on the fish species, habitat, fishing ground, season, etc., it is common to detect a high total mercury concentration of 0.2 to 6 μg / g. The value cannot be applied to tuna, and it is problematic that it is out of regulation simply because it is low in food intake.

  For many years, the inventors of this application worked on research on complete culture from bluefin tuna adult egg collection, fertilization, hatching, fry farming to adult fish as a method to deal with the depletion of bluefin tuna, a luxury fish. It has reached the stage of shipping 3 year old fish weighing 20-60kg, produced by complete aquaculture, to the market.

  As a result of bluefin tuna complete aquaculture research, it became clear that the amount of mercury accumulated in the fish body could be controlled by selecting the food used to cultivate high-quality fish. If the mercury concentration can be measured, all the individuals shipped to the market can be examined for mercury concentration, and safety certification can be attached to the mercury concentration, further enhancing the value of the high-grade farmed fish in the market be able to.

  Measuring the mercury content by cutting off a portion of a high-grade fish body may reduce the value of the product as well as cause deterioration in the quality of the meat and spoilage.Therefore, consider the economic burden of farmed fish producers and fishers. Then, it is difficult to do on a daily basis. In addition, even if the mercury content is measured using some individuals, there may be large individual differences, so it is dangerous to estimate the values of all individuals from the measured values of some individuals. .

  Therefore, an object of the present invention is to provide a method for evaluating the amount of mercury contained in a fish body by a simple method without damaging the fish body as a product.

  In order to achieve the above object, the inventors of the present invention have conducted research on methods for evaluating the amount of mercury contained in fish. Or the amount of mercury contained in the tail muscles to be discarded and the amount of mercury contained in the edible parts of the whole fish body have a certain positive correlation, whereby the fish blood or tail It was found that the amount of mercury contained in the edible part of the whole fish body can be evaluated by analyzing the amount of mercury contained in some meat parts of the fish, and the present invention has been completed.

  That is, the present invention analyzes the mercury concentration in the blood collected by the blood removal operation of fish or in the muscle of the site where the fish is disposed of by a known method, thereby determining the mercury concentration contained in the edible portion of the fish body. The summary is the method for evaluating the amount of mercury contained in fish.

  Yet another aspect of the present invention is that when a cultured fish is landed and shipped, the cultured fish is subjected to a blood removal operation, and the mercury concentration in the removed blood is measured by a known method. Evaluating the mercury concentration in the edible part, and only confirming that the evaluation value is below the safety standard, a safety certificate for mercury concentration is attached The gist of the fish production method.

  Next, taking a fully cultured bluefin tuna as an example, the results of analyzing the total mercury concentration contained in the edible part and blood of each part of the fish body and the contents of the present invention derived therefrom will be described in detail. As shown in FIG. 1, the cultured tuna fish body 1 is divided into the front part 2, the back part 3, the back part 4, the abdominal part 5, the abdominal part 6, the abdominal part 7, the tail part 8, and the muscles of these parts. The result of analyzing and measuring the total mercury concentration contained in the edible portion for three cultured bluefin tuna individuals aged 3 years is shown in the graph of FIG. 2 (the T-shaped line at the top of each bar graph shows the standard deviation. The same applies to the graph.) The values shown in the bar graph of the same color are the analysis values of the same individual. These results show that the total mercury concentration in blood is considerably lower than the total mercury concentration in the edible part of each part of the fish body, but there is a clear correlation between the two.

  In order to further clarify this correlation, the total mercury concentration in the blood of cultured bluefin tuna and the mercury concentration in the muscles in the back 3 were measured for a number of individuals, and these relationships are shown in the graph of FIG. From this graph, the linear correlation between the two is very clearly shown.

Furthermore, regarding the tailed normal and blood muscles of 98 fully-cultivated bluefin tuna tails of 2-3 years old fish (24 months to less than 42 months old) with a shipment size (weight 20-60 km) shipped to the market for one year, The mercury concentration was measured, and the relationship between the weight of each individual and the total mercury concentration is shown in the graph of FIG. The dotted line with a total mercury concentration of 1 μg / g represents the average value of the total mercury concentration contained in natural bluefin tuna. From these results, it can be said that the total mercury concentration does not increase even if the weight of the fish increases due to growth. Table 1 shows the distribution of body weight and total length of the 98 samples.

  Next, 98 fish (monthly average number of shipments of 8) that were raised in the same aquaculture ginger and shipped sequentially in one year from December to November of the following year, The graph of FIG. 4 shows the seasonal variation of the total mercury concentration contained in the tail muscle. From these results, it can be seen that the total mercury concentration of the fish repeatedly increases and decreases seasonally and accumulates gradually over a long span.

  Even in bluefin tuna farmed under the same conditions, there are large individual differences in the amount of fat riding, but the graph of Fig. 5 shows the relationship between the crude fat content and total mercury concentration measured for the 98 tail samples shown in Table 1. Shown in There is almost no difference in the total mercury concentration due to the difference in the crude fat content of the cultured bluefin tuna samples.

  The graph shown in FIG. 6 shows the result of measuring the total mercury concentration contained in each of the tails of the samples shown in Table 3 by dividing them into normal muscles and blood muscles. There is a slight difference between the total mercury concentrations in normal muscle and blood muscle.

  The graph shown in FIG. 7 shows the average value of the results of measuring the total mercury concentration of each tail muscle of 60 cultured bluefin tuna males and 34 females. From this, there is no difference in total mercury concentration between male and female bluefin tuna.

  From the above test results, the total mercury concentration contained in the edible portion of the bluefin tuna can be easily evaluated by analyzing the mercury concentration in the blood of the bluefin tuna or the muscle of the tail.

  A bottomed cylindrical ginger surrounded by a net with a diameter of about 30m and a depth of about 10m is installed below the surface of the sea. In this, the fully cultured bluefin tuna is raised mainly using mackerel, and shipped from 24 months to 42 months after birth. The size of the bluefin tuna is subjected to blood removal immediately after being picked up for shipment, blood and tail muscles are collected, and the blood is directly decomposed with concentrated nitric acid. The tail muscle was minced meat and then decomposed with concentrated nitric acid, and the mercury content of these samples was measured by a known reduction vapor atomic absorption method.

  In the above description, the results of testing the method for evaluating the mercury concentration of mainly fully-cultured bluefin tuna have been described. However, for high-grade fish other than bluefin tuna that undergo blood removal immediately after fishing, one of the blood ejected at that time Of the mercury amount of the present invention by taking a part of the sample as a sample, or collecting a muscle such as a tail that can be excised without impairing the commercial value, and measuring the amount of mercury in the sample in the same manner. Evaluation methods can be applied.

  For example, the method for evaluating the amount of mercury contained in the fish of the present invention is not limited to bluefin tuna, albacore, bigeye, yellowfin tuna, Atlantic bluefin tuna, cotyna and other tuna, swordfish, skipjack and other fish species. It can be applied to not only farmed fish but also natural fish. The ratio of mercury concentration in blood and mercury concentration in edible parts differs depending on the fish species, but once the correlation is measured, various methods can be used for various fish using the mercury concentration evaluation method of the present invention. It is possible to evaluate the total mercury concentration in the food area.

  According to the method for evaluating the amount of mercury contained in fish according to the present invention, after catching a fish, a part of blood is collected at the time of blood removal operation or a part of a tail muscle to be disposed of is removed. By collecting and analyzing the concentration of mercury contained in these, the amount of mercury for each individual can be evaluated very easily without compromising the commercial value of high-grade fish. If the safety certification for mercury concentration is attached only to those that have been confirmed, it is guaranteed that the mercury concentration is within the provisional regulation value for mercury concentration of general fish stipulated in the Food Sanitation Law for each individual. It is possible to dramatically increase the commercial value of fish and to provide a highly safe and guaranteed traceable product with safety certification to consumers in the market.

  It is a figure which shows the division | segmentation of the fish body of the bluefin tuna which applies the evaluation method of the amount of mercury contained in the fish of this invention.   It is a graph which compares and shows the amount of mercury for every muscle part of 3 bluefin tuna individuals.   It is a graph which shows the relationship between the body weight of the result of measuring total mercury concentration of blood and tail muscles, and total mercury concentration about 98 bluefin tuna fish of 3 years old shipped for one year.   It is a graph which shows the seasonal variation of the result of having measured the total mercury concentration of the bluefin tuna shipped for one year by the method of this invention.   It is a graph which shows the relationship between the total mercury concentration and fat mass which were measured about the muscle of the tail in bluefin tuna.   It is a graph which shows the result of having classified the muscle of the tail part of a bluefin tuna into normal muscle and blood muscle, and measuring the total mercury concentration, respectively.   It is a graph of the result of having measured total mercury concentration about the bluefin tuna male and female, respectively.   It is a graph which shows the relationship between the total mercury concentration in the bluefin tuna blood and the total mercury concentration in the back.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fish body 2 Back part 3 Middle back part 4 Back part 5 Abdominal part 6 Middle abdominal part 7 Abdominal part 8 Tail part

Claims (7)

  By analyzing the mercury concentration in the blood collected by the blood removal operation of fish or in the muscle of the site where the fish is disposed of by a known method, the mercury concentration in the edible part of the fish body is evaluated. A method for evaluating the amount of mercury contained.   2. The method for evaluating an amount of mercury according to claim 1, wherein the site to be disposed of is a tail.   The method for evaluating mercury content according to claim 1 or 2, wherein the fish is a tuna.   The method for evaluating mercury content according to claim 3, wherein the tuna is bluefin tuna.   The method for evaluating an amount of mercury according to claim 1, 2, 3, or 4, wherein the edible part is muscle.   When the cultured fish are landed and shipped, the cultured fish is subjected to blood removal operation, and the mercury concentration in the removed blood is measured by a known method. From the measured value, the mercury concentration in the edible portion of the cultured fish is measured. A safety-certified farmed fish production method, characterized in that only those whose evaluation values are confirmed to be at or below the safety standard are certified with mercury safety.   The method for producing cultured fish that has been certified as safe according to claim 6, wherein the cultured fish is bluefin tuna.

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