A Novel Type Mitochondrial Monoamine Oxidase from the Liver of Skipjack Tuna (Katsuwonus pelamis): Purification and Characterisation

A novel type of monoamine oxidase (EC. 1.4.3.4) present in the liver of skipjack tuna (Katsuwonus pelamis) was extracted from mitochondrial preparations by Triton X-100. The enzyme was purified by ammonium sulphate fractionation, followed by Sephadex G-200, butyl-toyopearl 650 M, phenyl-toyopearl 650 M and hydroxyapatite chromatography. The molecular weight of the enzyme was estimated to be about 110000 by gel filtration on Sephadex G-200. The enzyme was activated by Mn²⁺, but was inhibited by Cu²⁺, Zn²⁺ and p-chloromercuribenzoic acid (PCMB). Furthermore, the enzyme was completely inhibited by Hg²⁺ and 5,5′-dithiobis(2-nitrobenzoic acid) (DTNB). © 1997 SCI.     

Effect of Slurry Ice on the Functional Properties of Proteins Related to Quality Loss during Skipjack Tuna (Katsuwonus pelamis) Chilled Storage

The effect of slurry ice on the quality of Skipjack tuna (Katsuwonus pelamis) during chilling storage was investigated and compared to flake ice. Slurry ice‐treated samples showed significantly higher springiness and chewiness variables than the blank and flake ice‐treated samples (P < 0.05). The growth of microorganisms in tuna muscle treated with slurry ice was also down significantly (P < 0.05), and the total aerobic counts didn't reach higher scores than 5.0 log CFU/g during the whole chilling storage. Additionally, the myofibrillar protein, Ca²⁺‐ATPase activity, and total sulfydryl (SH) content in muscle treated with slurry ice were all significantly higher than the blank and flake‐iced samples (P < 0.05). This was probably due to the faster cooling, subzero final‐temperature, and larger heat exchange derived from slurry ice. Standard error of mean and sodium dodecyl sulfate–polyacrylamide gel electrophoresis results also confirmed that slurry ice treatment could effectively retard the degradation of myofibrillar proteins and showed a positive effect on the stability of tissue structures.     

Effect of Thermal Treatment on Moisture Transport during Steam Cooking of Skipjack Tuna (Katsuwonas pelamis)

ABSTRACT: Moisture and mass loss were determined during atmospheric steam cooking of skipjack tuna by measurement of muscle moisture content in whole fish and on-line measurement of mass and temperature in fillets. Thermal denaturation temperatures of muscle proteins were measured by differential scanning calorimetry. Muscle moisture content and mass loss were dependent on muscle temperature. Temperature distribution was predicted and mass loss rates were calculated in fillets. A decreasing rate of mass loss was followed by a steady rate period and a resumption of a decreasing rate period. The increased loss of mass during the steady period corresponded to thermal denaturation temperatures of muscle proteins. Changes in mass loss rates resulted from a gradient of muscle changes produced by the temperature gradient created during cooking.     

鲣鱼脱酸技术研究

以多聚磷酸盐为脱酸材料,对鲣鱼进行脱酸处理。通过单因素试验及正交试验得到的最佳脱酸条件为:多聚磷酸盐质量浓度3%、温度10℃、浸泡时间4 h。此条件下,经脱酸处理的鱼肉pH 6.3,基本无酸味。     

Purification and biochemical properties of pepsins from the stomach of skipjack tuna (Katsuwonus pelamis)

Pepsins 1 and 2 from the stomach of skipjack tuna (Katsuwonus pelamis) were purified to homogeneity by using a series of chromatographic purification involving DEAE-cellulose, Sephadex G-50 and Sephadex G-75 with increase in purity of 246-fold and 213-fold, respectively. Molecular weights of pepsins 1 and 2 were estimated by SDS–PAGE to be 33.9 and 33.7 kDa, respectively. The N-terminal amino acid sequences of the first 20 amino acids of both isoenzymes were YQDGTEPMTNDADLSYYGVI. The optimal pH and temperature for pepsin 1 were 2.5 and 50 °C, respectively, while pepsin 2 showed optimal activity at pH 2.0 and 45 °C. The activity of two pepsins was stable in the pH range of 2–5 and at temperatures up to 50 °C. The activity of purified pepsins was strongly inhibited by pepstatin A in a dose-dependent manner. SDS and cysteine showed inhibitory effects toward both pepsins. Activity of pepsin 2 was slightly activated by NaCl, but NaCl had no effect on pepsin 1. Pepsins 1 and 2 had high affinity and hydrolytic activity toward hemoglobin with K _m of 54 and 71 μM, respectively. k _cat of pepsins 1 and 2 were 38.1 and 44.3 s⁻¹, respectively. Both pepsins effectively hydrolyzed bovine serum albumin, egg white, natural actomyosin from brownstripe red snapper muscle and acid-solubilized collagen from arabesque greenling skin. Nevertheless, the hydrolytic activity was slightly less than that of pepsin from porcine stomach.     

蒸煮工艺对鲣鱼鱼柳品质的影响

以鲣鱼为原料,考察了两种不同的蒸煮工艺(T1、T2)对蒸煮过程中鱼柳的升温曲线、失水率、失重率、色泽、质构和组胺含量等的变化情况,分析两种蒸煮工艺对鱼柳蒸煮品质影响的差异,找出两种工艺的优缺点。结果表明,蒸煮工艺T1蒸煮损失较低,鱼柳得率比T2高1%~2%,蒸煮时间比T2短6~8 min,蒸煮过程中鱼肉色泽变化稳定,蒸煮完成后具有较好的质构特性,并且T1能有效降低鲣鱼肉中的盐含量。蒸煮工艺T2步骤相对简单,总加工时间比T1短20~30 min,组胺产生量比(T1)少约18 mg/kg,同时所得鱼柳还具有较高的非蛋白氮,气味较浓郁。两种蒸煮工艺各有优势,企业可以根据鲣鱼新鲜度及生产条件选择合适生产工艺。      

Biogenic amines assessment during different stages of the canning process of skipjack tuna (Katsuwonus pelamis)

The present research focused on the biogenic amines (BAs) formation in skipjack tuna (Katsuwonus pelamis) throughout the whole canning process. In agreement with its wide employment on this species, on‐board brine immersion freezing (BIF) was tested as post‐mortem processing. The study included fish samples corresponding to different stages of the canning process such as frozen, thawed, cooked and canned; after cooking, two kinds of tuna muscles were considered, that is, whole fillets (main product) and grated muscle (off‐product arising from small pieces). For the BAs (tryptamine, putrescine, cadaverine, histamine, spermidine and spermine) assessment, an HPLC‐DAD method was developed and validated in skipjack tuna samples, in agreement with different parameters such as suitability, linearity, limits of detection and quantification, precision, accuracy and robustness. Tuna submitted on‐board to BIF procedure provided low levels of spermine and spermidine (up to 27.6 mg kg^?1), while contents on the remaining BAs maintained below the limit of detection. Throughout the different stages of the canning process, skipjack tuna showed a low formation of most BAs; interestingly, histamine content was found below 10.6 mg kg^?1 level. The highest values were obtained for spermidine, these related to cooked grated tuna (from 22.6 to 66.7 mg kg^?1) and canned grated tuna (from 70.6 to 104.4 mg kg^?1). Values for pH assessment in all kinds of tuna samples corroborated the results obtained for BAs determination. BIF procedure proved to be an amenable post‐mortem processing to guarantee the quality of canned skipjack tuna.     

鲣鱼双酶酶解工艺优化及其产物动态变化研究

以鲣鱼为对象,优化了胰蛋白酶(trypsin)与木瓜蛋白酶(papain)复合酶解鱼肉蛋白的条件,研究了酶解过程中酶解液中游离氨基酸组成和含量、肽分子质量分布以及呈味核苷酸二钠含量的动态变化规律。结果表明:木瓜蛋白酶和胰蛋白酶双酶酶解鲣鱼最优条件为:最适比例1:3,总酶添加量3 000 U/g,底物浓度为25%。酶解过程中,酶解液中游离氨基酸总量不断增加,酶解6 h后,呈苦味氨基酸含量有所减少,而呈鲜味氨基酸大幅增加;对氨基酸呈味强度值(taste activity value,TAV)的分析表明,Glu、Met、Ile和His等几种氨基酸对酶解液的呈味特性起了关键作用。随着酶解时间的增加,大分子质量蛋白和肽类组分逐渐减少而小分子质量肽类组分逐渐增多,酶解6 h后分子质量小于0.5 ku的组分含量达到80.17%。呈味核苷酸二钠含量随酶解时间缓慢增加。     

Comparative study of basic characteristics of ordinary and dark muscle in skipjack tuna (Katsuwonus pelamis)

Differences between ordinary and dark muscle of skipjack tuna (Katsuwonus pelamis) including proximate composition, flavor, color, texture, and freshness were investigated. Ordinary muscle had a higher crude protein content, but a lower crude lipid content than dark muscle. Alcohols (30.41%) and aldehydes (25.56%) were the prominent flavor compounds present in ordinary muscle, whereas hydrocarbons (39.51%) and ketones (21.81%) were more abundant in dark muscle. Different L*, a*, and b* values were also observed. Texture profile analysis (TPA) showed that dark muscle had higher values for adhesiveness, and lower values for cohensiveness, chewiness, and resilience. After mechanical breaking, large myofibril fragments were observed in ordinary muscle under phase contrast microscopy, but not in dark muscle. Freshness indices, including K values, total volatile basic nitrogen (TVB-N), and thiobarbituric acid (TBA) values of dark muscle were higher than for ordinary muscle.     

Precooking and Cooling of Skipjack Tuna (Katsuwonas pelamis): A Numerical Simulation

A numerical simulation of the commercial tuna precooking and cooling process was developed as an aid to improving these critical thermal processing steps. Using the finite element method, a two-dimensional model of a tuna consisting of three regions, muscle, backbone, and viscera, was developed. Results from previous research on thermal properties of skipjack tuna were applied in the model. Preprocessor software, GAMBIT 1.1, and commercial finite element software, FIDAP 8.52, were used. The model was tested via comparison with experimental data collected in a commercial processing facility and a pilot plant. Good agreement between the simulation and experimental results was obtained.     

深海鲣鱼鱼油对D-半乳糖致衰老模型小鼠抗衰老的作用

以D-半乳糖致衰老模型小鼠为研究对象,评价深海鲣鱼鱼油对衰老模型小鼠抗衰老的作用。以健康育龄ICR小鼠为实验对象,随机分成6 组,每组8 只,即空白对照组,鲣鱼鱼油制剂低、中、高剂量组（20、50、100 mg/mL）,D-半乳糖模型组和阳性对照组。采用皮下注射方式,空白对照组小鼠每只每天注射质量分数0.9%的生理盐水,其余实验组注射质量分数为4%的D-半乳糖（1 000 mg/kg mb）,同时,鲣鱼鱼油制剂组分别每天灌胃10 mL/kg mb不同质量浓度（20、50、100 mg/mL）的鱼油制剂,阳性组灌胃市售鱼油（100 mg/kg mb）,空白对照组和模型组灌胃等体积生理盐水,持续6 周。随后检测各组小鼠肝、脾指数,肝脏组织和血清的谷胱甘肽过氧化物酶（glutathione peroxidase,GSH-Px）、总超氧化物歧化酶（total superoxide dismutase,T-SOD）、过氧化氢酶（catalase,CAT）活力及丙二醛（malondialdehyde,MDA）水平等指标,制备肝脏切片,观察小鼠肝脏组织的病理变化情况。结果表明：与模型组相比,鲣鱼鱼油高剂量组和空白对照组的肝、脾指数均呈显著下降趋势（P＜0.05）;模型组小鼠血清和肝组织GSH-Px、T-SOD、CAT活力较空白对照组显著降低,MDA水平显著升高（P＜0.05）,鲣鱼鱼油各剂量组均能提高血清和肝组织中GSH-Px、T-SOD、CAT活力并降低MDA水平;通过切片观察,深海鲣鱼鱼油可缓解衰老过程中肝脏的损伤,并且高剂量组的效果最为明显。     

Studies on size distribution of skipjack tuna (Katsuwonus pelamis): effect on chemical composition and implications for its utilization

Size and composition of skipjack tuna in Nigeria's Exclusive Economic Zone were investigated between May 1982 and January 1983. Monthly average length ± standard deviation varied between 41.65 ± 2.64 cm in January 1983 and 46.60 ± 3.02 cm in September 1982. Corresponding average weight varied between 1.34 ± 0.18 and 1.90 ± 0.37 kg. After logarithmic transformation of the variables (length and weight), a correlation coefficient of 0.901 was obtained. Frequency distribution of length classes enabled three size groups (small, medium and large) to be distinguished. Moisture, protein and ash content of fillets were not significantly affected by the size of the fish, but lipid content increased significantly ( P < 0.05) with size. Widest variations were observed in salt content, which decreased significantly ( P < 0.05) with increase in size. All chemical components were significantly affected ( P < 0.05) by seasonal variation. The implications for the fishery and utilization of this resource are discussed.     

Oxymyoglobin and Lipid Oxidation in Yellowfin Tuna (Thunnus albacares) Loins

The present study characterized oxymyoglobin (OxyMb) and lipid oxidation in yellowfin tuna, and determined the influence of various aldehydes on tuna OxyMb stability in vitro. Surface metmyoglobin accumulation and lipid oxidation increased in tuna steaks with time (P < 0.05). In both tuna steaks and patties, a* values decreased (P < 0.05) and hue angle increased following 6 d storage (P < 0.05). Sensory evaluation demonstrated increased discoloration and decreased odor acceptability in refrigerated steaks and patties over time (P < 0.05). Hexanal, hexenal, and 4‐hydroxynonenal enhanced OxyMb oxidation relative to controls in vitro (P < 0.05). These results indicate a relationship between myoglobin and lipid oxidation in tuna, and that aldehydes known to be produced during lipid oxidation can accelerate tuna OxyMb oxidation in vitro. Keywords: yellowfin tuna, oxymyoglobin, lipid oxidation, discoloration, aldehydes     

鲣鱼鱼卵成分分析及其活性糖蛋白提取工艺优化

目的 分析鲣鱼鱼卵营养成分组成,优化鲣鱼鱼卵糖蛋白(Katsuwonus pelamis roe glycoprotein, TGP)制备工艺,并考察其对MC3T3-E1成骨细胞增殖活性的影响。方法 采用食品安全国家标准方法测定鲣鱼鱼卵基本营养成分及其氨基酸、脂肪酸和胆固醇含量;以糖蛋白得率为评价指标,采用单因素实验结合响应面法研究优化TGP制备工艺;应用细胞毒性检测试剂盒(cell counting kit-8, CCK-8)检测TGP对MC3T3-E1细胞增殖活性的影响。结果 鲣鱼鱼卵中水分含量(72.79±0.33) g/100 g,蛋白质含量(21.09±0.03) g/100 g,脂肪含量(3.91±0.06)g/100g,灰分含量(1.50±0.01)g/100g,总糖含量(0.50±0.01)g/100g。鱼卵中氨基酸总量(727.38±8.77) mg/g,其中必需氨基酸占39.42%,鲜味氨基酸占30.68%,且谷氨酸含量最高(84.61±0.98) mg/g。鱼卵中含有17种脂肪酸,其中二十二碳六烯酸(docosahexaenoi cacid,DHA)和二十碳五烯酸...     

流化冰保鲜对鲣鱼蛋白质功能特性的影响

为探索流化冰对冰鲜水产品保鲜效果,以鲣鱼鱼肉为研究对象,以传统碎块冰保鲜为对照,探讨流化冰处理对鲣鱼肌肉蛋白质功能特性影响。结果表明：1）流化冰冰粒子呈球形,外表光滑、单位表面积大且流动性能好,8 min内可将鱼肉整体温度由35 ℃降低至1.3 ℃;2）－4 ℃贮藏18 d后,流化冰保鲜处理的鱼肉弹性和咀嚼性依次为1.19 mm和5.50 mJ,而空白（不加冰）、淡水碎块冰组分别为0.67 mm和1.65 mJ、0.95 mm和3.32 mJ,可见流化冰对鱼肉质构特性保持效果显著（P＜0.05）;3）0～18 d贮藏期内,不同处理鲣鱼肌原纤维蛋白含量、Ca2＋-ATPase活性及总巯基含量均呈逐渐下降趋势,其中以流化冰处理对鲣鱼蛋白质功能特性的保持效果最佳;此外,流化冰保鲜还兼具有抑制鱼肉氧合肌红蛋白自动氧化、维持肌肉原有色泽的作用。流化冰处理显著保持了鲣鱼肌肉组织的质构和相关蛋白质功能特性,可满足冰鲜水产品远洋、长距离运输和保鲜贮藏要求。     

Anti-inflammatory activity of ethanolic extract from skipjack tuna (Katsuwonus pelamis) heart in LPS-induced RAW 264.7 cells and mouse ear edema model

Food Science and Biotechnology - This study investigated the anti-inflammatory activity of the ethanolic extract (THEE) obtained from the heart of skipjack tuna using lipopolysaccharide...