Comparison of the proximate compositions,breaking strength and histological structure by the muscle positions of the full-cycle cultured Pacific bluefin tuna <Emphasis Type="Italic">Thunnus orientalis</Emphasis>

ABSTRACT:   Using the skeletal muscle of full-cycle cultured Pacific bluefin tuna (body weight: 13.1 ± 2.6 kg, cultured for about 21 months), the proximate compositions, breaking strength and histological structure of the front and rear parts of the dorsal ordinary muscles (FD-OM and RD-OM) and the ventral ordinary muscles (FV-OM and RV-OM) were compared. The FV-OM showed low moisture, protein, ash and high fat contents ( P  < 0.05, respectively) for the other three positions. The breaking strength of FD-OM, RD-OM and RV-OM increased up to 15–18 h and decreased later. However, the breaking strength of FV-OM was maintained during chilled storage. The pH of all muscles decreased up to 15 h, and then stayed at pH 5.7–5.8. However, the pH of FV-OM stayed at a higher level (pH 5.9). The histological structure observed by optical microscopy showed a space extension among muscle cells after 24 h in all positions, and these results were also supported by image analysis.     

The changes in proximate compositions and glycogen contents in the dorsal ordinary muscles of the full-cycle cultured Pacific bluefin tuna Thunnus orientalis occurring with growth

ABSTRACT:   Using full-cycle cultured (FC) Pacific bluefin tuna (body length [BL], 42.6–66.4 cm; body weight [BW], 1.66–7.40 kg, n  = 15), the changes in chemical compositions and histological structure of the cephalal parts of the dorsal ordinary muscles (DOM) occurring with growth were investigated. A positive correlation ( r  = 0.9644, P  < 0.05) was observed between BL and BW with growth. The protein, lipid and ash contents of DOM and condition factor did not change with growth. However, the glycogen content of DOM increased ( P  < 0.05) from approximately 55 cm (BL) in this study. Using optical microscopic photographs, the various shapes of muscle fibers were observed and it was noted that the muscle fiber diameter increased ( P  < 0.05) with growth. Using transmission electron microscopic observation, many glycogen granules were observed in muscle fibers (especially, side of connective tissue) of DOM throughout the growth stage in this study. These results indicate that the glycogen content of DOM of FC Pacific bluefin tuna increases before the lipid with growth.     

Changes in myoglobin content and proximate compositions of the dorsal ordinary muscles of full-cycle cultured Pacific bluefin tuna Thunnus orientalis (Temminck et Schlegel) with body size

We investigated the changes in myoglobin (Mb) content and proximate compositions of the cephalad parts of the dorsal ordinary muscles (Ce‐DOM) of full‐cycle cultured (FC) Pacific bluefin tuna [body length: 42.6–115.4 cm, body weight (BW): 1.7–38.4 kg, killed from July 2004 to October 2005]. The Mb content of Ce‐DOM increased (P<0.01) until a BW of 7.0 kg was reached. However, the Mb content of Ce‐DOM had a wide variety above a BW of 7.0 kg. On the other hand, the moisture, protein and ash contents of Ce‐DOM of FC tuna decreased (P<0.05 and 0.01) with an increase in BW. However, the lipid content of Ce‐DOM increased gradually above about a BW of 20.0 kg. Furthermore, the Mb content in protein of the Ce‐DOM of FC tuna increased with an increase in BW. These results indicated that the increase in Mb content of Ce‐DOM of FC tuna was not related to changes in proximate composition between a BW of 1.7 and 38.4 kg.     

Effects of Brief Summer or Winter Fasting on the Muscle Quality of Cultured Pacific Bluefin Tuna (Thunnus orientalis)

The effects of fasting on the quality of the dorsal and ventral ordinary muscles from cultured Pacific bluefin tuna (Thunnus orientalis) during chilled storage were investigated. Tuna were subjected to fasting for 2 days in the summer or 6 days in the winter prior to harvesting. The breaking strength of the dorsal ordinary muscle sampled in the summer increased until 24 h and then decreased. There were no significant differences in the lipid and glycogen content of the ordinary muscle after 9 h of storage between the controls and either fasting group. The pH of the ordinary muscle subjected to summer and winter fasting was higher than in the controls after 24–48 h of storage. However, the relationship between the pH and glycogen content was unclear. The metmyoglobin content during chilled storage was lower in the ordinary muscles from either fasting group than in the controls. In conclusion, fasting for 6 days in the winter improved the color stability of the ordinary muscle without a decline in its lipid content.     

Changes of proximate compositions and myoglobin content in the dorsal ordinary muscles of the cultured Pacific bluefin tuna <Emphasis Type="Italic">Thunnus orientalis</Emphasis> with growth

ABSTRACT:   Using the dorsal ordinary muscle (DOM) of cultured Pacific bluefin tuna (body length [BL]: 47.5–81.8 cm, body weight [BW]: 2.1–13.5 kg, n  = 15), the changes of proximate compositions and myoglobin (Mb) content with growth were investigated. There was a positive correlation ( r  = 0.9832, P  < 0.05) of BL and BW in cultured tuna. The protein contents of the DOM of cultured tuna decreased ( P  < 0.05) and the lipid contents had a tendency to increase (not significantly) with growth. The meat color changed from pink to red with growth. In addition, the Mb contents of the DOM of cultured tuna increased ( P  < 0.05) from 1.0 mg/g (minimum BW fish) to 3.8 mg/g (maximum BW fish) with growth. These results indicate that the increase of the Mb content in the DOM of cultured tuna is not caused by the restriction of exercise and overfeeding between 2.1 kg and 13.5 kg of BW.     

Fatty acid and proximate composition of bluefin tuna (Thunnus thynnus) muscle with regard to plasma lipids

The composition of tail muscle fatty acids from wild and cultured bluefin tuna reared on a diet based on herring and sardine, along with the plasma lipid profile of the farmed individuals, was determined. The total lipid content of farmed bluefin in this study was 0.922 g/100 g or 3.49 g of saturated fatty acids (SAFA), 4.48 g of monounsaturated fatty acids (MUFA), 2.58 g polyunsaturated fatty acids (PUFA) n‐3 and 0.37 g of PUFA n‐6 fatty acids; for wild specimens, it was 0.920 g/100 g, or 2.85 g of SAFA, 4.82 g of MUFA, 2.78 g PUFA n‐3 and 0.27 g of PUFA n‐6 fatty acids. The major fatty acids in this study were 16:0; 16:1, n‐7; 18:1, n‐9 and DHA 22:6, n‐3 acids. The sum of these major components accounted for more than 57% and 80% of the total fatty acids in all the samples of farmed and wild tuna respectively. No significant differences in the proximate composition were demonstrated between farmed and wild samples, except for the energy value, in favour of the farmed tuna. Statistically, glucose tends to increase together with cholesterol (CHOL) and plasma triglyceride, as for these pairs, it showed positive correlation coefficients and P>0.05. Some measured tuna metabolites demonstrated strong mutual correlations, especially GLU, CHOL and TRIG, which are crucial factors in the lipid profile of animals.     

二、三倍体虹鳟肌肉组织结构及营养成分的比较

选取相同养殖条件下3个不同体质量组的二倍体虹鳟和三倍体虹鳟,其中每组二倍体和三倍体虹鳟各10尾,分析其肌肉常规营养成分、氨基酸含量和肌纤维密度及直径,以比较二倍体和三倍体虹鳟的肌肉品质特性差异。试验结果表明,随着体质量的增加,二倍体、三倍体虹鳟肌纤维密度均降低,而肌纤维直径增大;二倍体虹鳟肌纤维直径小于三倍体,密度大于三倍体(P0.05)。随着体质量的增加,二倍体和三倍体虹鳟肌肉水分含量和粗灰分含量减少,而粗蛋白、粗脂肪含量显著增加;三倍体虹鳟粗蛋白和粗脂肪含量显著高于同组二倍体(P0.05),水分和粗灰分含量略低于二倍体,均差异不显著(P0.05)。二倍体和三倍体虹鳟肌肉中谷氨酸含量均最高,三倍体虹鳟总氨基酸含量、必需氨基酸含量以及鲜味氨基酸含量高于二倍体;根据营养价值评价结果,二倍体和三倍体虹鳟均为蛋氨酸和胱氨酸总量最高,第一限制性氨基酸均为苯丙氨酸。整体上来说,二倍体虹鳟和三倍体虹鳟均为优质蛋白源,二倍体虹鳟嫩度优于三倍体,但随着体质量的增加,三倍体虹鳟肌肉在营养成分上较均衡,且鲜美度要优于二倍体,有更好的食用价值及营养价值。     

短期禁食改善池塘养殖草鱼的食用品质

为探讨短期禁食提升池塘养殖鱼类食用品质的技术可行性,以3个邻近池塘养殖的商品草鱼为对象,分别转移至另一个池塘的3个网箱中,进行21 d短期禁食。每间隔7 d采集3个池塘来源的草鱼,并将鱼体分割为A、B、C、D共4个身段,采集其肌肉样品,对肌肉水分、粗蛋白质、粗脂肪和糖原含量进行定量分析。结果显示,禁食7 d时,不同身段肌肉营养物质含量即发生改变,14 d时粗蛋白含量和粗脂肪含量变化较大,其中尾部 (C、D段)的粗蛋白含量有显著增加的趋势;而10号池塘来源的草鱼A段粗脂肪含量在14和21 d分别比0 d减少了22.60%和17.07%,B、D段分别在7、14和21 d比0 d减少了7.50%、19.41%、12.61%和28.83%、36.68%、13.49%,17号池塘来源的的草鱼A、C和D段在7 d后显著增加,B段在7、14和21 d比0 d分别减少了26.76%、58.41%和62.90%,D段在7和14 d比0 d分别减少了1.52%和22.58%。3个池塘来源的草鱼肌糖原含量 (C、D段)有显著增加的趋势。采集草鱼身体B段背部肌肉样品,测定其肌肉系水力、肌肉质构特性和组织切片,发现10号池塘来源的草鱼在14 d时,背肌的滴水损失率无显著差异,17号池塘来源的草鱼背肌的滴水损失率在14 d时显著高于0 d,18号池塘来源的草鱼背肌的滴水损失率在14 d均有下降趋势。3个池塘来源的草鱼B段肌肉随禁食时间的延长,硬度下降,肌肉弹性增加,咀嚼性在14 d前呈逐渐增加趋势,内聚性则逐渐增加。禁食过程中背部肌纤维 (肌细胞)密度增加、肌纤维之间的间隙减小,肌肉硬度随禁食时间的延长逐渐下降,而弹性、咀嚼性表现为逐渐增加的趋势。研究表明,短期禁食可以改变草鱼肌肉的食用品质,综合实验结果以禁食14 d的时长为最佳。本研究结果为改善池塘养殖鱼类食用品质提供了科学依据。     

短期禁食改善池塘养殖草鱼的食用品质

为探讨短期禁食提升池塘养殖鱼类食用品质的技术可行性,以 3 个邻近池塘养殖的商品草鱼为对象,分别转移至另一个池塘的 3 个网箱中,进行 21 d短期禁食.每间隔 7 d采集 3 个池塘来源的草鱼,并将鱼体分割为A、B、C、D共 4 个身段,采集其肌肉样品,对肌肉水分、粗蛋白质、粗脂肪和糖原含量进行定量分析.结果显示,禁食 7 d时,不同身段肌肉营养物质含量即发生改变,14 d时粗蛋白含量和粗脂肪含量变化较大,其中尾部(C、D段)的粗蛋白含量有显著增加的趋势;而 10 号池塘来源的草鱼A段粗脂肪含量在14 和 21 d分别比 0 d减少了 22.60%和 17.07%,B、D段分别在 7、14 和 21 d比 0 d减少了 7.50%、19.41%、12.61%和 28.83%、36.68%、13.49%,17 号池塘来源的的草鱼A、C和D段在 7 d后显著增加,B段在 7、14 和 21 d比 0 d分别减少了 26.76%、58.41%和62.90%,D段在 7 和 14 d比 0 d分别减少了 1.52%和 22.58%.3 个池塘来源的草鱼肌糖原含量(C、D段)有显著增加的趋势.采集草鱼身体B段背部肌肉样品,测定其肌肉系水力、肌肉质构特性和组织切片,发现 10 号池塘来源的草鱼在 14 d时,背肌的滴水损失率无显著差异,17 号池塘来源的草鱼背肌的滴水损失率在 14 d时显著高于 0 d,18 号池塘来源的草鱼背肌的滴水损失率在 14 d均有下降趋势.3 个池塘来源的草鱼B段肌肉随禁食时间的延长,硬度下降,肌肉弹性增加,咀嚼性在 14 d前呈逐渐增加趋势,内聚性则逐渐增加.禁食过程中背部肌纤维(肌细胞)密度增加、肌纤维之间的间隙减小,肌肉硬度随禁食时间的延长逐渐下降,而弹性、咀嚼性表现为逐渐增加的趋势.研究表明,短期禁食可以改变草鱼肌肉的食用品质,综合实验结果以禁食 14 d的时长为最佳.本研究结果为改善池塘养殖鱼类食用品质提供了科学依据.     

二甲基-β-丙酸噻亭对哲罗鱼生长性能和蛋白质代谢的影响

本研究旨在探讨二甲基-β-丙酸噻亭(DMPT)对哲罗鱼(Hucho taimen)生长性能、肌肉成分和蛋白质代谢的影响。选取1 800尾初始体质量为(4.20±0.02) g的健康幼鱼, 随机分为6组, 设1个对照组, 5个处理组, 每组3个重复, 每重复100尾。各处理组分别在基础饲料中添加0.02%、0.05%、0.1%、0.2%和0.5%的DMPT, 对照组投喂基础饲料。室内流水饲养周期为56 d。结果表明, 饲料中DMPT添加量为0.2%时, 哲罗鱼增重率和摄食率达最大值; 以DMPT添加量和增重率进行二次曲线回归分析, 得出DMPT最适添加量为0.24%。DMPT添加量为0.05%时, 血清总蛋白、白蛋白和球蛋白水平显著提高(P<0.05); 添加0.2%DMPT时, 血清总蛋白、球蛋白水平和谷草转氨酶水平显著提高(P<0.05); 添加水平0.02%~0.5%时, 哲罗鱼肝和肌肉蛋白质水平显著升高(P<0.05), 胃、肠道蛋白酶活性显著升高(P<0.05); 添加水平0.05%时, 脏体指数显著降低(P<0.05); 各处理组肌肉脂肪和灰分含量均与对照组差异不显著(P>0.05), 各组间血清谷丙转氨酶、肌肉氨基酸组成及含量未呈显著差异(P>0.05)。综上可见, 饲料中添加0.2%DMPT可明显提高哲罗鱼生长性能, 添加0.02%~0.5%DMPT可增加哲罗鱼肌肉和肝蛋白储存。

     

A Comparative Study of Lipid Composition of an Undervalued Crustacean (Munida spp.) Captured in Winter and Summer

This research was focused on the lipid fraction of an undervalued crustacean (lobster krill; Munida spp.) and the comparative study of individuals captured at winter and summer seasons. For this purpose, seasonal variations were analyzed in the muscle (i.e., tail meat) for proximate composition, lipid class distribution, and fatty acid (FA) profile. Mean total lipids ranged from 0.75 ± 0.08% (summer) to 0.92 ± 0.06% (winter), moisture from 77.94 ± 0.25% (winter) to 78.62 ± 0.38% (summer), and protein from 17.93 ± 0.46% (summer) to 18.22 ± 0.46% (winter). Regarding lipid class content (% of total lipids), phospholipids ranged from 64.85 ± 1.29 (summer) to 67.85 ± 2.56 (winter), sterols from 12.15 ± 0.35 (winter) to 13.54 ± 0.54 (summer), triacylglycerols from 0.04 ± 0.02 (summer) to 1.25 ± 0.88 (winter), and free FA from 1.14 ± 0.72 (winter) to 2.19 ± 0.34 (summer). In both seasons, the most abundant FA were C22:6ω3, C16:0, C18:1ω9, and C20:5ω3. Polyunsaturated fatty acids (PUFA) were found to be the most abundant group in samples from both seasons (50.4–55.3%). Higher PUFA values were determined in summer samples, while a highly valuable ω3/ω6 ratio (from 9.11 ± 1.12 in summer to 10.40 ± 1.39 in winter) was observed. It is concluded that in spite of being a low-fat product, the lipid fraction of this underutilized crustacean can provide highly valuable constituents.     

杂交鳜与鳜鱼、斑鳜肌肉营养成分和氨基酸含量比较

通过测定鳜鱼、斑鳜和杂交鳜的肌肉营养成分和18种氨基酸含量,结果表明：杂交鳜、斑鳜和鳜鱼的肌肉水分、脂肪、灰分的含量无显著差异（P〉0．05）,杂交鳜与斑鳜的肌肉蛋白质含量无显著差异（P〉0．05）,但均显著高于鳜鱼肌肉的蛋白质含量（P〈0．05）;鳜鱼、斑鳜和杂交鳜的18种氨基酸含量及其组成、18种氨基酸总量（TAA）、人体所需8种必须氨基酸总量（HEAA）及4种呈味氨基酸（天门冬氨孽、谷氨酸、甘氨酸和丙氨酸）的总量（FAA）均无显著差异（（P〉0．05）。     

Replacement of dietary fish oil with olive oil in young yellowtail <Emphasis Type="Italic">Seriola quingqueradiata</Emphasis>: effects on growth,muscular fatty acid composition and prevention of dark muscle discoloration during refrigerated storage

Dietary fish oil (FO) was replaced by olive oil (OO) in young yellowtail Seriola quinqueradiata to investigate its effects on growth, muscular fatty acid composition and prevention of color deterioration of dark muscle during storage. Yellowtail were fed one of four diets, where FO (80 g/kg diet) was replaced by OO (0, 25, 50 and 100%) for 40 days. No significant difference in growth was seen among the diet groups. In addition, these experimental diets did not affect the proximate compositions of the dorsal muscle, ventral muscle and the liver in these fish. Serum total protein, glucose and total cholesterol levels did not show significant differences; however, serum triglyceride levels were significantly higher in fish fed 50 and 100% OO diets. Fatty acid composition of ventral muscle reflected the composition of the respective diets. Dark muscle discoloration was reduced in fish fed OO diets after 12 to 18 h during storage at 4°C. Furthermore, the redness value of fresh dark muscle increased depending on the extent of FO replacement. These results indicate that the partial or total dietary replacement of FO with OO prevents discoloration of dark muscle without affecting the growth of young yellowtail after 40 days of feeding.     

Proximate biochemical variations in eggs of the prawn Macrobrachium americanum (Bate, 1869) during its embryonic development

Eggs of seven females were sampled to analyse the lipid, protein and carbohydrate content during the embryonic development of the prawn Macrobrachium americanum . Sampling was performed from recently spawned eggs to hatching. A hundred of eggs were sampled every 48 h during the trial. Proteins, lipids and carbohydrates were quantified. Proteins were the most abundant component, followed by lipids and carbohydrates as only minor constituents. Lipid decreased significantly from 42% to 23% of the total composition, while proteins increased from 55% to 76% and carbohydrates varied inconsistently. The change in total energy per egg through time during the embryonic development is represented by the equation y =−0.0133 x +0.334; r ²=0.94 ( y represents the energy content and x represents days). The main energy provider was lipids whose energy consumption is described by the equation y =−0.0158 x +0.203; r ²=0.96.