鱸鰻生化學特性及加工適性之研究

中文摘要

日本鰻(Anguilla japonica)養殖為臺灣重要產業，因鰻苗短缺導致產業衰微，鱸鰻 (A. marmorata) 成為新興替代魚種，惟生化學相關資料闕如。本研究採樣不同大小之養殖鱸鰻，分析其生化學組成，並探討其儲藏期間鮮度指標與生化學組成之變化，以了解其儲存安定性，另分析鱸鰻不同抽出液之抗氧化能力，並評估其加工利用方式，以協助業者產製新產品。 鱸鰻肌肉一般成分中蛋白質含量為15.2%~20.3%，粗脂肪為3.54~13.3%，一般成分與魚體大小無相關性。游離胺基酸(Free amino acid, FAA)總量為 93.8~176 mg/100 g，以牛磺酸、麩胺酸、甘胺酸、丙胺酸及離胺酸含量較高，小分子胜肽類則以雙胜肽之肌肽(Carnosine, Car)為主，含量高達 207-355 mg/100 g。鱸鰻死後ATP降解速度快，蓄積之核苷酸化合物主要為肌苷酸(Inosine 5’-monophosphate)。肌肉中脂肪酸含量最高者為油酸(C18:1)，其次為棕梠酸( C16:0)，且皆具高含量之DHA (C22:6)與EPA (C20:5)，不飽和脂肪酸所占比例也高於飽和脂肪酸。鱸鰻肉富含礦物質鉀、磷和鋅以及維生素A和E。 鱸鰻肉儲藏期間，pH值先降後升，而氨含量則漸上升，於7°C儲藏至3天、25°C儲藏至24小時，魚肉好氧性總生菌數(Total plate count, TPC)接近限量之3×106 CFU/g，揮發性鹽基態氮(Volatile basic nitrogen, VBN)分別在12天及16小時超過標準(25 mg/100 g)，三甲胺(Trimethylamine, TMA) 與 K 值亦隨時間增加而上升，依官能檢測、TPC、VBN 及K 值判斷鮮度品質，鱸鰻肉7°C之儲藏期限為3天，25°C為8小時。鱸鰻肉Car含量在儲藏期間下降，相對地其組成分之胺基酸b-丙胺酸(b-Ala)與組胺酸(His)含量逐漸上升，顯示Car會分解為b-Ala與His，低溫貯藏與放血處理可防止Car之分解。 利用四種檢測方法包括清除DPPH自由基、還原能力、螯合亞鐵離子以及SOD 超氧化歧化酶活性等評估鱸鰻肉與鱸鰻精之抗氧化性，結果發現鱸鰻肉與鱸鰻精之三氯醋酸(TCA)與磷酸鹽緩衝液(PBS)之萃取液皆具抗氧化能力，而鰻精之DPPH自由基清除能力、還原力與亞鐵離子螯合能力皆高於鰻肉，但鰻肉之SOD活性則明顯高於鰻精。 同一加工廠製造之鱸鰻、日本鰻與短鰭鰻蒲燒調味產品之VBN和TPC皆符合衛生標準，三種產品之官能品評分數以日本鰻產品最高，但無顯著差異。鱸鰻加工品之Car、His與β-Ala較原料低，但麩胺酸、天門冬胺酸與FAA總量較高，差異主要來自調味料；不同大小鱸鰻蒲燒加工品之FAA總量與呈味性差異明顯，須依大小適當調整加工與調味條件，以求入味均衡。 本計畫建立鱸鰻之生化學組成及機能性成分之基本資料，可供業者推廣行銷或改進產品品質之參考，並可作為研發新產品之依據。

英文摘要

The culture of Japanese eel (Anguilla japonica) is an important sector in Taiwan, but the shortage of eel fry disintegrated this sector. Giant mottled eel (A. marmorata) becomes an alternative species for aquaculture by degrees. However, few studies have been done on its biochemical characteristics and compositions. This study was to investigate the biochemical compositions in different sizes of giant mottled eels. Changes in chemical compositions and freshness index of giant mottled eel during storage were also studied to reveal the storage stability. In addition, the antioxidative activities of the tissue extracts were investigated in this study. Based on results of biochemical characteristics and functional compositions, the suitable utilization and processing of giant mottled eel was evaluated to develop new products. Crude protein in the muscle were ranged from 15.2~20.3%, and crude fat were 3.54~13.3%. The total amount of free amino acids (FAA) in the muscle was 93.8~176 mg/100g, and the major FAA were taurine, glutamic acid, glycine, alanine and lysine. The major nucleotide-related compound in the muscle was inosine 5’- monophosphate (IMP). Carnosine (Car) was the predominant small peptide, and its level reached 207~355 mg/100 g. The dominant fatty acid in the muscle was oleic acid (C18:1), followed by palmitic acid (C16:0). In addition, the contents of DHA (C22:6) and EPA (C20:5) were also high. The ratio of unsaturated fatty acid to total fatty acid was higher than that of saturated fatty acid. Giant mottled eel also contained abundant amount of minerals potassium, phosphorus and zinc, and vitamins A and E. The muscle pH value decreased at the early storage period and then increased after elongated storage. The total plate count (TPC) was closed to the limit value of 3×106 CFU/g during storage at 7°C and 25°C for 3 days and 1 day, respectively. For the limit value (25 mg/100 g) of volatile basic nitrogen (VBN), the storage time was 12 days and 16 hours, respectively. Trimethylamine (TMA) and K value also increased with increasing time. According to the results of organoleptic evaluation, TPC, VBN, K values, the self-life of giant mottled eel meat was 3 days and 8 hours during storage at 7°C and 25°C, respectively. During storage Car decreased, but b-alanine (b-Ala) and histidine (His) increased. Results showed that Car was degraded into b-Ala and His. Refrigeration storage and bleeding treatment could decrease the degradation rate. The methods including the scavenging effect of DPPH free radical, reducing power, chelating ability of Fe2+ and SOD activity are used to detect the antioxidative activities of giant mottled eel meat and its essence. Results showed that both extracts of tricholoacetic acid and phosphate buffer of eel meat and its essence possessed antioxidative activities. Eel essence had higher scavenging effect of DPPH free radical and reducing power than eel meat, but the latter had higher SOD activity.      The roasted and seasoned products of giant mottled eel, Japanese eel and short-finned eel produced by the same factory showed VBN and TPC complied with national sanitation standards. According to the results of sensory evaluation, Japanese eel product had a higher score among three roasted products, but no significant difference was found. As compared with raw materials, the processed products of giant mottled eel had lower amounts of Car, His and β-Ala, but had higher amounts of glutamic acid, aspartic acid and total FAA. Seasoning sauce resulted in this difference. There were remarkable differences in total FAA amount and flavor intensity among different size of giant mottled eel products. Processing and seasoning conditions should be adjusted to obtain balanced seasoning products.            Results of this project provided the data regarding the biochemical and functional properties of giant mottled eel for market promotion, and the reference for improving the quality of eel products. In addition, it also provided useful ways for suitable utilization and new product development. https://www.fa.gov.tw/view.php?theme=research_report&subtheme=&id=685&print=Y

Cats – telomere to telomere and nose to tail

貓科基因組醫學能夠解讀人類不確定意義的變異（VUSs）。端粒到端粒的基因組組裝技術適用於所有貓科物種，這支持了遺傳進化與物種形成的研究。與人類相比，貓科動物高度保守的基因組結構表明，牠們可能也能解讀影響三維染色體結構並調控基因的基因間變異。
https://www.cell.com/trends/genetics/fulltext/S0168-9525(21)00142-6

Abstract

Feline genomic medicine can decode human variants of uncertain significance (VUSs). Telomere-to-telomere genome assemblies are feasible for all felid species, supporting genetic evolution and speciation studies. Their highly conserved genomic organization compared to humans suggests cats may also decipher the intergenic variation affecting the 3D chromosome structures influencing gene regulation.

Keywords

1. felines
2. precision medicine
3. genome editing
4. genome sequencing
5. phase-genome
6. gapless assembly

Semidomesticated hypercarnivores (see Glossary), domestic cats are bioproxies for human agricultural development and our postagrarian migrations. These critters are often underfoot but are also the keynote predatory species and at the top of the food chain in diverse ecological niches, whether wild, rural, or urban. Darwin, Haldane, Searle, and other early geneticists recognized that cat pelage phenotypes supported Mendel’s laws and other basic genetic principles. Cats have also helped decode more complex genetic concepts including lyonization, X-inactivation, and methylation because of their X-linked Orange coat coloration and since the first cloned cat, Cc, did not come out as the expected coat coloration [1]. The coat patterns and colors of domestic and wild species of cats exemplify intricate biological pathways, demonstrating that not one of the ~20 000 genes in our mammalian genomes stands alone. Feline leukemia virus gave us our first clues into cancer etiology and the consideration of hybrid cats nearly a half century ago [2], and more recently, the nucleoside-analog-based remdesivir proving highly effective in combating the COVID pandemic was firstly shown to cure a previously fatal coronavirus-induced disease in cats, feline infectious peritonitis [3]. Quelled enthusiasm by the scientific community has historically meant cats have been perhaps a pace behind with their genetic and genomic resources. However, the cat research community may be small but is efficient and has, for arguably fewer funds and personnel, helped cats to effectively leap forward in genomics, showing new promise in supporting genomic medicine, gene regulation, and speciation studies and the development of therapeutics for use by humans and animals.

Precision/genomic medicine is now feasible in veterinary healthcare, especially for domestic cats. Approximately 33% of households in the USA own a cat, and as pets, cats have evolved from vermin control to beloved family members. With increasing vigilance, cat owners are escalating their expenditures for their cats’ veterinary care, whether the cat is one of the 10% representing a fancy breed or the 90% representing a randomly bred alley cat. Whole genome sequencing (WGS) and whole exome sequencing (WES) are available for domestic cats as genomic diagnostic tools for their healthcare via the community-based 99 Lives Cat Genome Sequencing Consortium [4,5]. Consortium studies are defining new disease variants for well-recognized disease genes, thereby supporting established biomedical models, such as Niemann–Pick disease type C [6]; new variants in new genes for known diseases, such as disproportionate dwarfism, thereby providing new genetic considerations for undiagnosed patients [7]; and new variants for new diseases of conserved biological processes, such as brain development or cell migration and differentiation [8]. The cat’s genomic tools and the 99 Lives Consortium have led to more rapid identification of causal disease and trait variants in cats, hence naturally occurring biomedical models, with ~84 mutations causing diseases under negative selection and 44 desired variants under positive selection in cats and at least seven variants influencing one blood group (https://omia.org) (Figure 1). Analyses of only 54 unrelated cat genomes and the production of the cat reference assembly V9.0 suggests cats have high genetic diversity, with 36.6 million biallelic single nucleotide variants (SNVs) in which individuals carry ~9.6 million SNVs each. Conversely, humans roughly carry 4 to 5 million SNVs per individual [4]. Variant effect prediction shows that 128 844 SNVs of the 36.6 million are synonymous, 77 662 missense, and 1179 loss of function (LoF). With hundreds of thousands of human genome sequences for comparison, deciphering DNA variants causal for diseases, traits, conditions, and behaviors is still an elusive process, leading to a plethora of VUSs that mar the decoding of causal variants. The vast cat genetic variation should be used in a comparative genetics approach. Genetic constraint can be expressed as the probability of LoF intolerance (pLI), implying specific genes have more or less tolerance to variants causing a significance loss of their protein’s function. The 15 962 direct cat–human orthologs share similar levels of pLI, suggesting variant prediction combined with pLI could support VUS prioritization [4]. The increasing DNA variant WGS and WES datasets produced during veterinary healthcare not only support the discovery of the feline causal variants for traits, conditions, and biomedical models, but their innocuous variants also have value and can be compared to human VUS databases, potentially deciphering VUS functions and influencing their priority for further investigation.

‘Dark matter’ – whether 85% of the universe or 98% of mammalian genomes – clouds the understanding of our state of being. Approximately 10% of the noncoding regions within the ‘dark matter’ of the genome are conserved across species, suggesting these sequences have some control over form and function, biology and physiology, and behavior and temperament. Besides decrypting VUSs, cross-species genomic comparisons are enlightening some of the functions of noncoding sequences, supporting the identification of regulatory sequence motifs. For an example in cats, dominant White, which is associated with deafness and white Spotting, which is associated with domestication, are traits caused by an ~800 bp and ~8 kb insertion into intron 1 of the KIT gene, respectively (OMIA 001737-9685, 000209-9685, 001580-9685). Although not an intergenic variant, the disruption of intronic sequences and noncoding sequences suggests that this variant influences gene regulation and overall melanocyte production and migration. Since hundreds to thousands of genome sequences are now being produced for many species, including domestic cats, pangenome assemblies [9], which represent both SNV and structural variation, will help decipher inter- versus intraspecies genomic variation and whether the variation controls interspecies evolution and speciation versus intraspecies phenotypes and diseases.

Cats, felids, the family Felidae, are represented by ~42 species, diverging from other mammals, including humans, ~65 million years ago (www.iucnredlist.org). Cats have easily distinguishable chromosomes that can be readily flow sorted, thus facilitating somatic cell hybridization mapping and chromosome painting [10]. These gross mapping techniques demonstrate the cat genomic organization is a strong proxy for most feliform carnivores [11]. Syntenic blocks of genes on the 23 human chromosomes are more extended in the 19 cat chromosomes in comparison to other common mammalian model organisms such as mice, rats, dogs, and pigs. Additionally, the first phased, haploid-based genome assemblies of F1 hybrid felids highlight the potential of the genomic investigation of the family Felidae, particularly for evolution and speciation [12]. Genome assemblies for the domestic cat and the Asian leopard cat (Prionailurus bengalensis) are robust with N50 scaffolds of 147.6 and 148.6 Mb and 71 and 83 total scaffolds, respectively, indicating the success of the assembly of complex repeat regions. A variety of hybrids produced by natural matings of domestic cats are available, such as crosses with the Geoffroy’s cat, (Oncifelis geoffroyi), servals (Leptailurus serval), and jungle cats (Felis chaus) or lions (Panthera leo) crossed with tigers (Panthera tigris), producing the liger, suggesting many felid phased genome assemblies are possible. In addition, reproductive techniques developed for wild felid conservation could support additional cat genome assemblies since any felid sperm will fertilize a domestic cat oocyte; thus, hybrid cell lines from disrupted embryos could be expanded to provide sufficient DNA for WGS. Thus, like the human telomere-to-telomere consortium (sites.google.com/ucsc.edu/t2tworkinggroup/home), even longer-read technologies suggest assembly scaffolds will soon encompass complete chromosomes, telomere-to-telomere. Since haploid-based phased genome assemblies are feasible for every cat species, telomere-to-telomere genome assemblies may cover the family Felidae – nose to tail.

People tend to either love them or hate them, and cats are often underappreciated by the scientific community. Will the species with conserved genomic organization with humans, or the species with less genome conservation, help resolve gene regulation via the similarities and differences in the 3D structures created in the intergenic or intragenic sequences? Felids could be the optimal species to enlighten the human genome’s dark matter. Does the dark matter hold more keys to evolution of form and function and speciation? The assisted reproductive technologies have produced both RFP and GFP transgenic cats. Thus, genome-edited cats are feasible, allowing the production of a large animal biomedical model for disease studies, understanding basic biology and physiology, and providing an alternative for long-term model therapeutic trials. New genomic technologies are allowing cats to develop new avenues for understanding evolution, domestication, and adaptation. Feline genomics holds great potential and promise for advancing human medicine and mammalian biology.

日本 45 年來首次出口體重在 13 公克以下日本鰻稚魚

 日本自2025年2月25日，日本鰻稚魚，即體重在13公克以下之日本鰻苗已達可開放出口之條件。開放出口啟動條件是其國內日本鰻苗之放養量超過其上限的五成，即10.85公噸。前一個日本鰻苗漁期暫停日本鰻稚魚之出口，在隔2年後又首次可能恢復。日本出口日本鰻苗之決定是為提高國際鰻苗貿易透明化因應措施之一，於2021年2月修訂「鰻苗出口貿易管制令」後，今年是日本45年來首次出口日本鰻稚魚，以後只要日本國內放養量確認達到一定水準後，事前經水產廳核對申請表，出口證明文件以及鰻苗交易協會發出的「鰻苗產地證明書」後，即可向經濟產業部申請並核准後即可出口的制度。

此一制度推出後，2021年鰻苗漁期的3月下旬，確定在隔45年後可出口日本鰻稚魚，但2022年漁期以後，由於日本國內鰻苗的採捕量嚴重不足，滿足放養量上限一半要到3月底及4月初，由於年度可出口之時間只到4月30日止，因此可出口之時間非常短暫，出口量因而維持在最低之水平。而今年東亞三國的鰻苗較為群集，因此滿足出口條件的時間比往年早一個月左右。

據鰻苗交易協會有關人士表示該協會從鰻苗放養量滿足出口條件以來，就一直收到有關簽發原產地憑證的詢問。如果實際出口成真的話，就成為2023年漁期以來隔2年後再度有鰻苗出口。

最近5年日本鰻稚魚出口之實績為2020年44.8公噸，2021年有17.0公噸，2023年則只有8.5公噸及2024年之18.2公噸。這些出口之日本鰻稚魚幾乎全部是體重超過13公克的魚組成，這樣大小的魚本來就合法可出口的。

李賢忠，摘譯自日刊水產經濟新聞，3 March 2025

 https://www.nature.com/articles/s42254-025-00824-6?utm_source=facebook&utm_medium=organic_social&utm_content=null&utm_campaign=CONR_JRNLS_AWA1_GL_PCOM_SMEDA_NATUREPORTFOLIO

The physics of cats

Nature Reviews Physics volume 7, page165 (2025)Cite this article

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This April, we reflect on the varied and surprisingly close connection between physics and cats.

The buttered cat paradox — the question of whether a cat will always land on its feet even if it has strapped on its back a piece of toast, which always lands buttered side down — may only be a humorous thought experiment, but the fact that cats right themselves during a fall to land on their feet is not. It posed a genuine puzzle to generations of scientists because it seems to defy the laws of nature, specifically angular momentum conservation. If a cat — approximated by a cylinder — starts its fall without a rotational component it cannot pick up angular momentum during its descent. And yet, it does.

In the late 19th century, a series of photographs of a falling cat1 provided some clues for a better understanding of the physiology involved in a cat’s righting reflex. It also ruled out one explanation of the physics: that air resistance could supply the necessary angular momentum. But it wasn’t until 1969 that a simple mathematical model was published2, which could explain how cats violate angular momentum conservation, or rather how they don’t. The solution? Modelling the cat not as one rigid cylinder but allowing it to bend, or using two cylinders in the model.

Feline flexibility continues to inspire semi-serious discussions, for example around the question of whether cats are liquids. Part of the definition of a liquid is that it takes on the shape of the container holding it. Countless memes on the Internet show that cats do the same. This photographic evidence may not match the scientific rigour of the tumbling cat series, but it was enough to get one physicist thinking. Marc-Antoine Fardin used the idea of liquid cats to illustrate a range of rheological principles3, winning him the 2017 Ig Nobel Prize in Physics.

However, the most famous cat in physics is undoubtedly Schrödinger’s cat. The thought experiment Erwin Schrödinger originally conceived as a criticism of the Copenhagen interpretation of quantum mechanics has developed a life (and death) of its own. What started as a challenge to quantum mechanics has become its popular symbol. The dead-and-alive cat lends its name to popular science books, appears in a range of science fiction stories and serves as the all-around mascot of quantum physics. People who know nothing about quantum mechanics still know the cat.

Schrödinger may have only used the cat in his thought experiment to emphasize a seeming absurdity, but the superposition it is meant to illustrate is real. For example, coherent states of an optical mode can have different phases, and it is possible to create a superposition of two such states with opposite phase. This is called a cat state or, if the mean photon number of the mode is low, a kitten state. Unlike the thought experiment that gave them their name, cat states are not a mere curiosity. They have applications in quantum information, where cat codes are an encoding scheme for quantum error correction.

There is another famous cat with ambiguity issues: the Cheshire Cat from Alice in Wonderland, which can vanish, leaving only its grin behind. Although that sounds as absurd as a cat that is simultaneously dead and alive, it comes as no surprise that quantum physicists have made it real too, in their own way. Under certain conditions, a quantum system can behave as if it is in a different place from its physical property. For example, a specific measurement protocol reveals that a neutron may take a different path through a silicon interferometer than its magnetic moment4. These quantum Cheshire cats can even exchange their grins5.

Not content with being the passive objects of (thought) experiments, some cats have joined the ranks of researchers. Possibly the only, but certainly the most well-known, feline physicist is F. D. C. Willard — Chester to his friends. He co-authored his first paper with owner Jack Hetherington in 1975 because Hetherington had used the plural ‘we’ throughout the article and didn’t want to retype it. Chester now has a Google Scholar profile, which records 113 citations across his four publications.

Although Nature Reviews Physics does not endorse feline authorship, we love to see pictures of Felis catus in our pages. You may not have noticed, but we have managed to sneak in quite a few cover cats over the years. How many can you count?

References

1. Nature 51, 80–81 (1894).

2. Kane, T. R. & Scher, M. P. Int. J. Solids Struct. 5, 663–670 (1969).

3. Fardin, M. A. Rheol. Bull. 83, 16–17 (2014).

4. Denkmayr, T. et al. Nat. Commun. 5, 4492 (2014).

5. Liu, Z.-H. et al. Nat. Commun. 11, 3006 (2020).