冷凍貯蔵中における魚肉の変色に関する研究-II : 魚肉中のFeII型およびFeIII型ミオグロビンの同時定量法

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The method reported in the previous paper1) on pure myoglobin (Mb) solution was found to be also applicable to extracts prepared from tuna meat. The procedure is as follows: 10g. of the muscle finely ground in an ice-cold mortar are weighed into a glass-stoppered centrifugal tube and extracted for about 2 hours with 25ml. of ice-cold water with occasional stirring in an atmosphere of CO (cf. Table 1). After centrifugation, 15ml. of the supernatant are taken into another glass-stoppered centrifugal tube, to which some amount (usually 0.2 to 0.5ml.) of 1N NaOH solution are added for the purpose of removal of cloudiness, and the solution is left standing at least for one hour in a refrigerator. After centrifugation, 5 or 10ml. of the supernatant are diluted with 10ml. of ice-cold 0.2M phosphate buffer of pH 7.0 and divided into three portions. These portions are subsequently treated as described in the previous paper1) and percentage distribution of metmyoglobin (MMb) in the extract is calculated by the equation, a-d/a-b×100, as shown before1). In calculating the content of Mb in tuna meat, some considerations should be paid which are not necessary in the case of pure Mb solution, especially on the impurities of extract which disturb the spectrophotometry and on the water content of meat, and the following equation is recommended: y=(α-z)(S1/10+S2)10ƒM/E(mg.%) where ƒ is dilution factor, S1 water content (%) of the muscle, S2 volume (ml.) of extractant used, M molecular weight of tuna Mb, E molar extinction coefficient of tuna carbonylmyoglobin (MbCO) at 568mμ, and z optical density at 568mμ by impurities. By the equation, z=bp-a/p-1, z may be obtainable, where p is a constant, the ratio of optical density at 568mμ of MbCO to MMb (4.31 in the case of Thunnus orientalis). The reliability of the method was checked by the recovery tests which were very satisfactory (Table 2), and some experiments were cited as examples of application of this mothod (Tables 3 to 4 and Fig. 1).
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冷凍貯蔵中における魚肉の変色に関する研究-II : 魚肉中のFeII型およびFeIII型ミオグロビンの同時定量法

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