WEKO3
アイテム
魚類，とくにキハダマグロのジェリーミートに関する研究
https://fra.repo.nii.ac.jp/records/2005339
https://fra.repo.nii.ac.jp/records/2005339e80b3d3b-31a3-4970-a56f-8342526ab264
| Item type | 紀要論文 / Departmental Bulletin Paper(1) | |||||
|---|---|---|---|---|---|---|
| 公開日 | 2024-05-22 | |||||
| タイトル | ||||||
| タイトル | 魚類，とくにキハダマグロのジェリーミートに関する研究 | |||||
| 言語 | ja | |||||
| タイトル | ||||||
| タイトル | Studies on the Jelly Meat of Fish, with Special Reference to That of Yellowfin Tuna | |||||
| 言語 | en | |||||
| 言語 | ||||||
| 言語 | jpn | |||||
| 資源タイプ | ||||||
| 資源タイプ識別子 | http://purl.org/coar/resource_type/c_6501 | |||||
| 資源タイプ | departmental bulletin paper | |||||
| アクセス権 | ||||||
| アクセス権 | metadata only access | |||||
| アクセス権URI | http://purl.org/coar/access_right/c_14cb | |||||
| 著者 |
小長谷, 史郎
× 小長谷, 史郎 |
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| 抄録 | ||||||
| 内容記述タイプ | Abstract | |||||
| 内容記述 | It has long been observed that commercial fish meat occasionally exhibit abnormally soft, jelly-like, or, in extreme cases, liquescent appearance. This abnormal fish meat and the phenomenon are generally called jellied meat and jellification, respectively. Recently, this so-called jellied meat has been observed very frequently along with the increase in catch by the deep-sea fishery as well as in the quantity of imported fish. The term "jellied meat" expresses several categories distinguishable from the outer appearance of the meat, or probably differing in the cause. These include abnormal meats commonly called "azuki" in case of yellowfin tuna, swordfish etc., "sashi" in cases of bigeye tuna and skipjack, "fukuro" in the case of flounder, or those described as "mushy" or "milky" in English. The most typical type of jelled meat such as azuki, mushy or milky meat are usually associated with parasitic myxosporidia. Although the myxosporidia has long deen suspected to be related to the cause of jellification, there has not been sufficient account of the cause or mechanism of jellification. Furthermore, there is no method to prevent or predict the presence of jellification, nor is there definite proof of the safety of the jellied meat for human consumption. As jellied meat actually causes economic loss to fish producers and dealers concerned, it is one of the important problems in the fisheries industry. This study was undertaken with the background just described to elucidate the cause and mechanism of jellification phenomenon. First of all, jellification of yellowfin tuna Thunnus albacares of which jellied meat is rather easy to obtain as sample was taken up. Next, similar jellied meat of three different species of fish, such as swordfish Xiphius gladius, Pacific hake Merluccius productus, and yellowfin sole Limanda aspera, being available as samples, were characterized. The results of the investigation are described in five chapters. Chapter I describes the results of microscopic and chemical examinations of jellied meat of yellowfin tuna as a preliminary survey. Careful microscopic examinations were made for detection of spores of myxosporidia using smear slides prepared from the muscle exudate of many specimens of both normal and jellied yellowfin tuna meat. Numerous spores of myxosporidia which were identified as Hexecapsula neothunni were found exclusively in the jellied meat. Further. more, histological observations indicated that the spores occured as tightly packed aggregates within some muscle fibers of the meat at premonitory stage of jellification. The site of parasitization of H. neothunni was confirmed to be inside the muscle fiber. The incidence of infected muscle fibers was no more than 4% of muscle fibers in the tissue. It was also observed histologically that the initial breakdown of muscle tissue began at the infected muscle fibers, breakdown extended progressively to surrounding un-infected fibers, and developed into visible disrupted areas as milky pockets. The coincidence between the site of infection and muscle tissue breakdown as mentioned above indicates a close relationship between myxosporidian infection and jellification. Secondly, proximate composition of proteins and non-protein nitrogen compounds was determined as usual. It was found that contents of 5% trichloroacetic acid (TCA) soluble peptides was higher in the jellied meat than in the normal meat. These histological and chemical findings strongly suggest that proteolysis took place in restricted small areas in the muscle tissue, namely, the localization of protease responsible for jellification. Thirdly, as jellied yellowfin tuna is usually found among tunas ice-chilled for 1-2 days after death of the fish, the relation between jellification and freshness of the fish was examined. The K value (a freshness index for fish) of samples from jellied yellowfin tuna never exceeded 22%, even though the jellied condition was very severe, and the amount of VBN was also below a level of 17 mg/100 g meat. The findings, accordingly suggested that the jellification phenomenon might not be related directly to freshness, although it seems to proceed along with freshness decline. Lastly, the degree of jellification of yellowfin tuna meat was tentatively divided into 5 degrees (0-IV; 0: premonitory stage of jellification, IV: extremely advanced stage) depending on the physical appearance of the condition. Furthermore, attempts were made to evaluate objectively the jellification. Two methods were found to be suitable: a method using the compressive stress of meat as parameter, and the other intensity of the copper-FOLIN color (E₆₆₀ₙ ₘ) of TCA-extract of the specimens. In chapter II, the protease activity in the jellied meat of yellowfin tuna was examined with hemoglobin and muscle proteins as substrates, as jellification was regarded as the result of proteolysis of muscle tissue protein. Strong protease activity was detected in the jellied meat in the acidic pH region from 2.5 to 5. Histochemical examination showed that the protease existed exclusively in the infected muscle fibers. The protease activity in the jellied meat was strongly inhibited by leupeptin, HgCl₂, PCMB, and to some extent by pepstatin, but not affected at all by soybean tripsin inhibitor and DFP. On the contrary, the activity in the normal meat was completely inhibited by pepstatin, but not at all by leupeptin, On the other hand, hydrolytic activity against synthetic substrates for cathepsin B (thiol protease), ie. Bz-Arg-β-naphthylamine and Bz-DL-Arg-NH₂, was not detected in the jellied meat. These findings implied that the major protease actvity in the jellied meat was due to thiol protease derived from myxosporidia H. Neothunni. If the protease activity found in the jellied meat is resposible for jellification, the jellification rate must be related to factors such as strength of protease activity, pH and temperature of the muscle of yellowfin tuna after capture. These factors were, therefore, examined. Protease activity was assayed following the method of ANSONHAGIWARA: The mixture containing one part of the muscle extract, 3 parts of 0.1 M citrate-phosphate buffer pH 3, and one part of 3% hemoglobin as substrate was incubated at 37°C for 2 h. The reaction was stopped by the addition of an equal volume of 5% TCA. Hydrolysis products in the TCA-filtrate were estimated by development of color using FOLIN's method and measured at E₆₆₀ₙ ₘ was, hereafter, used as a measure of protease activity. The level of protease (cathepsin D) activity of the normal yellowfin tuna was 0.04-0. 05, whereas the protease actvitity of the jellied meat showed a high level, ranging from 0.07 to 0. 16. On the other hand, the number of spores of H. neothunni in the jellied meats differing in protease activity: 0.075, 0. 120 and 0. 158, were estimated to be about 3 ×10⁴, 8 × 10⁴ - 10⁵, and 5 × 10⁵ - 10⁶, respectively. This suggested that there was likely correlation between the degree of infection with H. neothunni and protease activity. The effects of protease activity and temperatue on jellification rate were examined next. Specimens of slightly jellified yellowfin tuna meat (degree I) having activity of 0. 145 further jellied to degree III during 24 h incubation at 25°C, while specimens of parasitized meat with activity of 0.089 did not jellify to an appreciable extent under similar incubation conditions. Incipient meat (degree 0-I) having moderate protease activity (0. 120) barely jellified to degree II at 0°C after 8 days, However, it jellified to degree II-III at 20°C after 24 h, and after 12 h at 30°C, to degree III-IV. It appeared that jellification becomes very rapid at temperatures above 20°C. The maximum jellification rate was observed at around 55°C. As to the body temperature and muscle pH of yellowfin tuna, it was observed that yellowfin tuna as well as other species of tuna had a relatively high body temperature, when caught. The body temperature was highest at the central portion of the body, and sometimes higher than the environmental water temperature by as much as 15°C. In the coastal tuna fishery, the catch is usually chilled with ice-water until landing and there-after kept in crushed ice. However, temperature measurements made experimentally indicated that chilling was not always effective. Measurments of the post-mortem muscle pH showed a range of 5.6 to 6.2 depending on the individuals and the post-mortem time elapsed. These two factors, temperature and pH, therefore probably play an important role in acceleration of jellification. In chapter III, separation and characterisation of the protease under consideration was attempted. A specimen of jellied meat was homogenized in three parts of 0.5% KCl and the homogenate was centrifuged. The muscle extract thus obtained was submitted to salting-out by (NH₄)₂SO₄. The fraction precipitated between 30 and 50% (NH₄)₂SO₄ saturation was dissolved in a small quantity of water, and thoroughly dialyzed against 0.01 M phosphate buffer pH 7.0. The solution was then submitted to CM-Sephadex chromatography, and eluted with the same buffer in NaCl linear gradient. Two protease fractions which were named J-I and J-II in order of elution for convenience were obtained. The J-I fraction was futher separated into three fractions J-I-A, B and C by Sephadex G200 gel-filtration, and the J-II fraction into two fractions J-II-A and B by Sephadex G100 gel-filtration. In contrast, normal meat gave a single protease fraction (N-I-A) which behaved similarly to J-II-B fraction protease in chromatography and gel-filtration. As the protease activities in both J-II-B and N-I-A fractions were strongly inhibited by pepstatin, but not affected by leupeptin, proteases in both fractions were considered to be the same, ie. cathepsin D. Therefore, the other fractions of proteases appeared to be specific to jellied meat. Their activity ratio in the jellied meat was estimated to be J-I-A, 2-9%, J-I-B, 13-32%, J-I-C, 64-72% and J-II-A, 1-6%. Although the activity ratio differed to some extent from sample to sample, the proteases in J-I-B and C fractions were confirmed to be the major ones specific to the jellied yellowfin tuna meat. J-I-B and C protease fractions were then further purified byDEAE-Sephadex chromatography in 0.01 M phosphate buffer pH 6.0, in 0-0.4 M (NH₄)₂ SO₄ linear gradient. A single peak of protease activity was obtained from each fraction. The J-I-B and C fraction protease were purified 354 and 658 fold over the crude extract with 7 and 13% recovery, respectively. The molecular weight of J-I-B and C protease were estimated to be 14.6×10⁴ and 6.3 × 10⁴, respectively. Neither association nor dissociation of these protease molecules seemed to take place during the course of purification. Profiles of effects of inhibitors and chemical agents almost completely coincided with each other. They hydrolyzed sarcoplasmic proteins as well as myofibrillar fragments prepared from normal yellowfin tuna meat rapidly at pH 3 and farely well at pH 5.8. From these results, it was concluded that the proteases (J-I-B and J-I-C) produced by H. neothunni were thiol protease and responsible for jellification of the yellowfin tuna meat. In chapter IV, jellied meat of some other species of commercial fish were studied. The cause of jellification of swordfish Xiphius gladius meat was first examined. As in the case of jellied yellowfin tuna, numerous spores of myxosporidia Chloromyxum musculoliquefaciens were detected in the jellied swordfish meat. Tightly packed aggregates of spores were also found inside muscle fibers in the tissue at premonitory stage of jellification. Furthermore, it was found that strong protease activity was present exclusively within the infected muscle fibers. The nature of the tissue degeneration process was considered to be essentially the same as that of the parasitized yellowfin tuna muscle tissue. Protease specific to jellied swordfish meat were separated into 9 fractions by chromatography, gel-filtration and other treatments. The protease in the fraction which occupied 50% of the total activity and which was capable of hydolysing myofibrils was regarded as the main protease responsible for jellification. This protease belongs to the group of thiol protease and it's molecular weight was estimated to be 4.7 × 10⁴. In jellied meat of Pacific hake Merluccius productus and yellowfin sole Limanda aspera, a myriad spores of myxospridia tentatively classified as Chloromyxum sp. and Kudoa sp. respectively, and strong activity of thiol protease, probably secreted by these parasitic myxosporidia were also found. In view of these facts and other evidents it was concluded that proteases produced by the myxosporidia also account to the jellification of these fish meat. In chapter V, a comprehensive discussion was given to the all results and conclusions so far described. | |||||
| 言語 | en | |||||
| 書誌情報 |
ja : 東海区水産研究所研究報告 en : Bulletin of Tokai Regional Fisheries Research Laboratory 巻 114, p. 1-101, ページ数 101, 発行日 1984-11 |
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| 出版者 | ||||||
| 出版者 | 東海区水産研究所 | |||||
| 言語 | ja | |||||
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| 出版者 | Tokai Regional Fisheries Research Laboratory | |||||
| 言語 | en | |||||
| ISSN | ||||||
| 収録物識別子タイプ | PISSN | |||||
| 収録物識別子 | 0040-8859 | |||||
| 書誌レコードID | ||||||
| 収録物識別子タイプ | NCID | |||||
| 収録物識別子 | AN00156834 | |||||
| 情報源 | ||||||
| 識別子タイプ | Local | |||||
| 関連識別子 | tokai_k_97 | |||||
| 関連サイト | ||||||
| 識別子タイプ | URI | |||||
| 関連識別子 | https://agriknowledge.affrc.go.jp/RN/2010824079 | |||||
| 言語 | ja | |||||
| 関連名称 | 日本農学文献記事索引(agriknowledge) | |||||
