渔业科学进展  2024, Vol. 45 Issue (3): 258-267  DOI: 10.19663/j.issn2095-9869.20230314001
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刘龙龙, 罗鸣, 刘洪涛, 陈傅晓, 韩丽娜. 不同规格野生黄鳍金枪鱼肌肉营养分析与评价[J]. 渔业科学进展, 2024, 45(3): 258-267. DOI: 10.19663/j.issn2095-9869.20230314001.
LIU Longlong, LUO Ming, LIU Hongtao, CHEN Fuxiao, HAN Lina. Analysis and Evaluation of the Muscle Nutrition of Different Sizes of Wild Yellowfin Tuna (Thunnus albacares)[J]. Progress in Fishery Sciences, 2024, 45(3): 258-267. DOI: 10.19663/j.issn2095-9869.20230314001.

基金项目

海南省重大科技计划(ZDKJ2021011)和财政部和农业农村部：国家现代农业产业技术体系(CARS-47-Z18)共同资助

作者简介

刘龙龙, E-mail: silyboylong@163.com

通讯作者

罗鸣, 副研究员, E-mail: hothawk@yeah.net

文章历史

收稿日期：2023-03-14
收修改稿日期：2023-04-11
Contents              Abstract              Full text              Figures/Tables              PDF
不同规格野生黄鳍金枪鱼肌肉营养分析与评价
刘龙龙 1,2,3, 罗鸣 1,2,3, 刘洪涛 4, 陈傅晓 1,2,3, 韩丽娜 1     
1. 海南省海洋与渔业科学院 海南 海口 571126;
2. 海南热带海洋学院崖州湾创新研究院 海南 三亚 572025;
3. 海南热带海洋学院 热带海洋生物资源利用与保护教育部重点实验室 海南 三亚 572022;
4. 海南省热带海水养殖技术重点实验室 海南 海口 571126
收稿日期：2023-03-14；收修改稿日期：2023-04-11
基金项目：海南省重大科技计划(ZDKJ2021011)和财政部和农业农村部：国家现代农业产业技术体系(CARS-47-Z18)共同资助
作者简介：刘龙龙, E-mail: silyboylong@163.com.
通讯作者：罗鸣, 副研究员, E-mail: hothawk@yeah.net.
摘要：为探究不同规格黄鳍金枪鱼(Thunnus albacares)肌肉营养成分及品质差异，实验以野捕的3种规格黄鳍金枪鱼J1(4.2±1.2) kg、J2(22.5±2.5) kg和J3(50.8±3.9) kg为研究对象，通过常规生化分析方法对金枪鱼肌肉的常规营养成分、氨基酸、脂肪酸及矿物质元素进行比较分析。结果显示，(1) J1组水分含量显著高于J2、J3组；J2、J3组粗蛋白含量显著高于J1组(P<0.05)；J3组粗脂肪含量显著高于J1、J2组(P<0.05)。(2)检出19种常见氨基酸，氨基酸含量最高的为谷氨酸(3.04~3.25 g/100 g)，必需氨基酸中含量最高的为赖氨酸(2.02~2.15 g/100 g)，最低的为色氨酸(0.31~0.45 g/100 g)。非必需氨基酸含量J3>J2>J1(P<0.05)；必需氨基酸、呈味氨基酸含量J1组显著低于J3组(P<0.05)。依据氨基酸评分(AAS)，缬氨酸为第一限制性氨基酸；以化学评分(CS)为评分标准，J1、J2组第一限制性氨基酸为色氨酸，J3组为苯丙氨酸+酪氨酸。(3)各组共检出25种脂肪酸，以多不饱和脂肪酸(PUFA)为主，含量最高的为二十二碳六烯酸(DHA)，占总脂肪酸含量的37.46%~39.18%。DHA含量J3组显著高于J1、J2组；二十碳五烯酸(EPA)含量J2、J3组显著高于J1组；DHA∶EPA比值J1组显著高于J2、J3组(P<0.05)。单不饱和脂肪酸(MUFA)含量J3＞J2＞J1；PUFA含量J3组显著高于J1、J2组(P<0.05)。PUFA/饱和脂肪酸(SFA)、n-3系多不饱和脂肪酸/n-6系多不饱和脂肪酸(n-3/n-6)比值J2、J3组显著高于J1组(P<0.05)。h/H比值J3组显著高于J1、J2组(P<0.05)。(4) J2、J3组Na、Ca含量显著高于J1组，J1组K含量最高且显著高于J2、J3组(P<0.05)。4种重金属元素均低于食品中建议的最大允许限量，其中Fe含量最大的为J3组，且J3＞J2＞J1(P<0.05)；Cu含量最大的为J3组，且显著高于J1组(P<0.05)。综合分析，大规格黄鳍金枪鱼具有更好的营养质量，本研究为居民膳食的选择及黄鳍金枪鱼人工配合饲料的配制提供了科学依据。
关键词：黄鳍金枪鱼    肌肉    规格    营养成分    氨基酸    脂肪酸    
Analysis and Evaluation of the Muscle Nutrition of Different Sizes of Wild Yellowfin Tuna (Thunnus albacares)
LIU Longlong 1,2,3, LUO Ming 1,2,3, LIU Hongtao 4, CHEN Fuxiao 1,2,3, HAN Lina 1     
1. Hainan Academy of Ocean and Fisheries Sciences, Haikou 571126, China;
2. Yazhou Bay Innovation Institute, Hainan Tropical Ocean University, Sanya 572025, China;
3. Key Laboratory of Utilization and Conservation for Tropical Marine Bioresources, Ministry of Education, Hainan Tropical Ocean University, Sanya 572022, China;
4. Hainan Provincial Key Laboratory of Tropical Maricultural Technologies, Haikou 571126, China
Corresponding author: LUO Ming, E-mail: hothawk@yeah.net.
Abstract: Yellowfin tuna (Thunnus albacares) is popular with consumers due to its delicious meat and high nutritional value. It is a globally recognized high-end marine economic fish. With the advancement of fishing equipment and the increase in fishing efforts, the amount of tuna resources has decreased significantly. To make up for the insufficient supply of tuna in the market and protect wild populations, it is essential to carry out research on artificial aquaculture technology for tuna and to gradually establish full-cycle cultures of tuna. In order to study the differences in the nutritional components and quality of yellowfin tuna muscles of different sizes, three different-sized yellowfin tuna, J1 (4.2±1.2) kg, J2 (22.5± 2.5) kg, and J3 (50.8±3.9) kg, were used as the research subjects, and conventional biochemical analysis methods were used to compare and analyze the proximate compositions, amino acids, fatty acids, and mineral elements of tuna muscle. The results showed that (1) the moisture level of the J1 group was significantly higher than that of the J2 and J3 groups (P<0.05); the crude protein levels of the J2 and J3 groups were significantly higher than that of the J1 group (P<0.05); and the crude fat level in the J3 group was significantly higher than that in the J1 and J2 groups (P<0.05). (2) A total of 19 common amino acids were detected in yellowfin tuna muscle, including nine essential amino acids (EAA), two semi-essential amino acids, and eight nonessential amino acids. The amino acid with the highest content was glutamic acid (3.04~3.25 g/100 g) of the three tuna sizes; the essential amino acid with the highest content was lysine (2.02~2.15 g/100 g), and the essential amino acid with the lowest content was tryptophan (0.31~0.45 g/100 g). The amino acid content of different-sized yellowfin tuna varied greatly, except for threonine, valine, methionine, isoleucine, tyrosine, and phenylalanine, which were not significantly different among the groups, and the other amino acid contents were mainly J3>J2>J1. The content of nonessential amino acids was J3>J2>J1 (P<0.05). The content of essential amino acids and delicious amino acids in the J1 group was significantly lower than that in the J3 group (P<0.05). The content of semi-essential amino acids in the J1 group was significantly lower than that in the J2 and J3 groups (P<0.05). The ratio of EAA/TAA (total amino acids) in each group was above 40%, and there were no significant differences. According to the Amino acid score (AAS) score, the valine score in each group was the lowest and<1, which was the first limiting amino acid. According to the chemical score (CS) score, except for lysine and tryptophan of the J3 group, the scores of other amino acids were all less than 1. The first limiting amino acid of groups J1 and J2 was tryptophan, while the first limiting amino acids of the J3 group were phenylalanine + tyrosine. (3) A total of 25 fatty acids were detected in the muscles of yellowfin tuna of three sizes, including 10 saturated fatty acids (SFAs), 5 monounsaturated fatty acids (MUFAs), and 10 polyunsaturated fatty acids (PUFAs). There were nine fatty acids whose content was greater than 1%, and their average content ranged from high to low: C22:6n3 docosahexaenoic acid (DHA), C16:0, C18:0, C18:1n9c, C20:5n3 eicosapentaenoic acid (EPA), C20:4n6 arachidonic acid (ARA), C18:2n6c, C24:1n9, and C16:1n7. Among these nine fatty acids, only C16:0, C24:1n9, and C16:1n7 showed no significant differences (P>0.05). The fatty acids in yellowfin tuna muscle were mainly PUFAs, and the content of DHA accounted for 37.46%~39.18% of the total fatty acid content. The DHA content of the J3 group was significantly higher than that of the J1 and J2 groups (P<0.05). The EPA content of the J2 and J3 groups was significantly higher than that of the J1 group (P<0.05). The DHA: EPA ratio of the J1 group was significantly higher than that of the J2 and J3 groups (P<0.05), and the MUFA content was J3>J2>J1 (P<0.05). The PUFA content of the J3 group was significantly higher than that of the J1 and J2 groups (P<0.05). PUFA/SFA and n-3/n-6 ratios of the J2 and J3 groups were significantly higher than those of the J1 group (P<0.05). The h/H ratio of the J3 group was significantly higher than that of the J1 and J2 groups (P<0.05). (4) Among the four macro elements, the contents of sodium and calcium of the J2 and J3 groups were significantly higher than those of the J1 group (P<0.05), and the potassium content of the J1 group was the highest and was significantly higher than that of the J2 and J3 groups (P<0.05). The contents of four heavy metal elements were all far lower than the maximum allowable limit (FAO and WHO) suggested in food, among which the iron content was the highest in the J3 group, and J3>J2>J1 (P<0.05). The copper content was the highest in the J3 group, and was significantly higher than that in the J1 group (P<0.05). Comprehensive analysis showed that large size yellowfin tuna had better nutritional quality, and the results of this study also provide a scientific basis for the selection of residents' diets and the formulation of artificial nutrition feed for yellowfin tuna.
Key words: Yellowfin tuna(Thunnus albacares)    Muscle    Size    Nutritional components    Amino acids    Fatty acids    

黄鳍金枪鱼(Thunnus albacares)隶属鲈形目(Perciformes)，鲭亚目(Scombroidei)，鲭科(Scombridae)，金枪鱼属(Thunnus)，广泛分布于印度洋、太平洋和大西洋的热带、亚热带以及温带的广阔海域，在我国主要分布于东海和南海，是高度洄游性鱼类。金枪鱼是全球公认的高端海洋经济鱼类，因其肉味鲜美、营养价值高而备受消费者的喜爱，市场需求量巨大，但随着捕捞装备的提高及捕捞强度的增加，金枪鱼资源量急剧下降，捕捞产量降低，难以满足国内外市场需求。为弥补市场金枪鱼供应的不足及保护野生种群，开展金枪鱼人工养殖技术研究，逐步建立金枪鱼人工养殖业是非常必要的。目前，许多国家如日本、澳大利亚和墨西哥等已开展金枪鱼的人工养殖，日本已基本实现了蓝鳍金枪鱼(Thunnus orientalis)的全周期人工养殖(Nakamura et al, 2007; 彭士明等, 2019)，我国沿海虽然也有金枪鱼资源分布，但截至目前，国内在金枪鱼人工养殖的研究几乎处于空白状态，仅见南海水产研究所开展相关的驯养工作(周胜杰等, 2022)。

国内外关于黄鳍金枪鱼肌肉营养组成与评价已有相关研究，如幼鱼消化酶活性及氨基酸组成(Buentello et al, 2011)；暗色肌(dark muscle)的品质特征(Elena et al, 2011)；不同海区黄鳍金枪鱼脂质质量比较(Domingues et al, 2021)；黄鳍金枪鱼和大眼金枪鱼(Thunnus obesus)肌肉组织氨基酸和脂肪酸组成比较(Peng et al, 2013)；美济礁附近海域3种金枪鱼(大眼金枪鱼、蓝鳍金枪鱼、黄鳍金枪鱼)肉质评价(周胜杰等, 2021)；黄鳍金枪鱼食用品质研究(罗殷等, 2008)等。这些研究大部分只是针对黄鳍金枪鱼某一生长阶段或不同海区的肉质比较，而关于不同规格黄鳍金枪鱼的肌肉营养组成比较尚未见报道，研究野生金枪鱼肉质组分可为金枪鱼的人工养殖营养需求提供参考(Mourente et al, 2009)。本研究通过对不同规格黄鳍金枪鱼肌肉常规营养成分、氨基酸、脂肪酸及矿物质元素综合分析与评价，为居民膳食的选择及黄鳍金枪鱼人工营养饲料的配制提供科学依据。

1 材料与方法 1.1 材料

实验用黄鳍金枪鱼于2021年9月—2022年12月在南海海区海钓捕获(见表 1)，根据平均体重分为J1 (4.2±1.2) kg、J2 (22.5±2.5) kg和J3 (50.8±3.9) kg 3种规格，各取3尾，取头部与第一背鳍之间背部肌肉，用干冰速冻后转入–80 ℃冰箱保存备用。

表 1 3种不同规格黄鳍金枪鱼体重、捕捞时间及地点 Tab.1 Yellowfin tuna with three different sizes weight, sampling date and sampling region.
1.2 肌肉常规营养成分的测定

采用GB 5009.3-2016直接干燥法测定肌肉水分，采用GB 5009.6-2016酸水解法测定肌肉粗脂肪，采用GB 5009.5-2016凯氏定氮法测定肌肉粗蛋白，采用GB 5009.4-2016高温炉灼烧法(550 ℃)测定肌肉总灰分。

1.3 肌肉氨基酸与脂肪酸的测定

肌肉氨基酸测定使用全自动氨基酸分析仪(S-433D, 德国)，其中，色氨酸按照GB/T 15400-2018，采用高效液相色谱法测定；胱氨酸、蛋氨酸按照GB/T 15399-2018，采用离子交换色谱法测定，其他氨基酸按照GB 5009.124-2016，采用分光光度法测定。

肌肉脂肪酸的测定使用气相色谱仪(Agilent 7890A，美国)，参照GB 5009.168-2016，采用内标法测定。

1.4 氨基酸与脂肪酸质量评价

根据FAO/WHO (1973)建议的氨基酸评分标准模式和全鸡蛋蛋白质的氨基酸模式分别计算黄鳍金枪鱼必需氨基酸的氨基酸评分(AAS)、化学评分(CS)(周胜杰等, 2021)；脂质营养质量通过以下指标来评估，降胆固醇脂肪酸/升胆固醇脂肪酸(h/H)、多不饱和脂肪酸/饱和脂肪酸(PUFA/SFA)、n-3系多不饱和脂肪酸/n-6系多不饱和脂肪酸(n-3/n-6)(Domingues et al, 2021)。计算公式：

$\begin{align} & \mathrm{AAS}= \\&\;\; \frac{\text {样品蛋白质中某种氨基酸含量}(\mathrm{mg} / \mathrm{g})}{\mathrm{FAO} / \mathrm{WHO} \text {评分模式中同种氨基酸含量}(\mathrm{mg} / \mathrm{g})} \\&\;\; \mathrm{CS}=\frac{\text {样品蛋白质中某种氨基酸含量}(\mathrm{mg} / \mathrm{g})}{\text {全鸡蛋蛋白质中同种氨基酸含量}(\mathrm{mg} / \mathrm{g})} \end{align}$
$\begin{gathered} \mathrm{h} / \mathrm{H}=(\mathrm{C} 18: 1 \mathrm{n}-9+\mathrm{C} 18: 2 \mathrm{n}-6+\mathrm{C} 18: 3 \mathrm{n}-3+\mathrm{C} 20: 4 \mathrm{n}-6 \\ +\mathrm{C} 20: 5 \mathrm{n}-3+\mathrm{C} 22: 5 \mathrm{n}-3+\mathrm{C} 22: 6 \mathrm{n}-3) /(\mathrm{C} 14: 0+\mathrm{C} 16: 0) \\ \mathrm{PUFA} / \mathrm{SFA}=\sum \mathrm{PUFA} / \sum \mathrm{SFA} \\ \mathrm{n}-3 / \mathrm{n}-6=\left(\sum \mathrm{n}-3\right) /\left(\sum \mathrm{n}-6\right) \end{gathered}$
1.5 矿物质元素的测定及评估

Na、K、Mg、Ca、Fe、Cu、Mn、Zn使用电感耦合等离子体发射光谱仪(Optima 8000，美国)采用GB 5009.268-2016电感耦合等离子体发射光谱法(ICP-OES)测定。重金属安全评估参照FAO (1998)和WHO (1989) (Mokhtar et al, 2009)建议的食品中允许的最大含量。

1.6 数据处理

数据以平均值±标准差(Means±SD)形式表示，使用SPSS19.0进行单因素方差分析(one-way ANOVA)和LSD多重比较，显著性水平为0.05。

2 结果 2.1 常规营养成分的比较

不同规格黄鳍金枪鱼常规营养成分见表 2。J1组水分含量显著高于J2、J3组(P<0.05)，J2和J3组无显著性差异(P>0.05)；J2、J3组粗蛋白含量显著高于J1组(P<0.05)；粗脂肪含量J3组显著高于J1、J2组(P<0.05)，J1和J2组无显著性差异(P>0.05)。各组灰分含量无显著性差异(P>0.05)。

表 2 3种规格黄鳍金枪鱼肌肉常规营养成分(以湿基计) Tab.2 Proximate composition of muscle in three different sizes of yellowfin tuna (g/100 g) (in wet basis)
2.2 氨基酸的组成与评价

黄鳍金枪鱼肌肉中检出19种常见氨基酸(表 3)，包括9种必需氨基酸(EAA)、2种半必需氨基酸和8种非必需氨基酸。3种规格黄鳍金枪鱼氨基酸含量最高的均为谷氨酸(3.04~3.25 g/100 g)；必需氨基酸中含量最高的为赖氨酸(2.02~2.15 g/100 g)，最低的为色氨酸(0.31~0.45 g/100 g)。不同规格黄鳍金枪鱼氨基酸含量差异较大，除苏氨酸、缬氨酸、蛋氨酸、异亮氨酸、酪氨酸、苯丙氨酸各组差异不显著外，其他氨基酸含量以J3组>J2组>J1组为主。总氨基酸(TAA)、非必需氨基酸含量J3组>J2组>J1组(P<0.05)；必需氨基酸、呈味氨基酸含量J1组显著低于J3组(P<0.05)，但与J2组无显著性差异(P>0.05)；半必需氨基酸含量J1组显著低于J2、J3组(P<0.05)。各组EAA/TAA比值均在40%以上，且无显著性差异(P>0.05)。

表 3 3种规格黄鳍金枪鱼肌肉氨基酸组成(以湿基计) Tab.3 Amino acid composition of muscle in three different sizes of yellowfin tuna (g/100 g) (in wet basis)

采用AAS和CS评分，对不同规格黄鳍金枪鱼氨基酸进行营养评价(表 4)。依据AAS评分，各组缬氨酸评分最低且小于1，为第一限制性氨基酸，J1、J2组第二限制性氨基酸为苏氨酸，J3组为亮氨酸；以CS为评分标准，除赖氨酸及J3组色氨酸外，其余各氨基酸评分均低于1，J1、J2组第一、第二限制性氨基酸分别为色氨酸、苯丙氨酸+酪氨酸，J3组第一、第二限制性氨基酸分别为苯丙氨酸+酪氨酸、缬氨酸。

表 4 3种规格黄鳍金枪鱼肌肉必需氨基酸营养评价 Tab.4 Nutritional evaluation of essential amino acids in muscle of three different sizes of yellowfin tuna
2.3 脂肪酸的组成比较

3种规格黄鳍金枪鱼肌肉中共检测出25种脂肪酸(表 5)，包括10种SFA，5种单不饱和脂肪(MUFA)，10种PUFA。有9种脂肪酸百分含量高于1%，其平均含量从高到低排列C22:6n3 (DHA)、C16:0、C18:0、C18:1n9c、C20:5n3 (EPA)、C20:4n6 (ARA)、C18:2n6c、C24:1n9、C16:1n7，在这9种脂肪酸中只有C16:0、C24:1n9和C16:1n7三种脂肪酸无显著性差异(P>0.05)。黄鳍金枪鱼肌肉中脂肪酸以PUFA为主，其中，二十二碳六烯酸(C22:6n3, DHA)含量占总脂肪酸含量的37.46%~39.18%，DHA含量J3组显著高于J1、J2组(P<0.05)，J1、J2组无显著性差异(P>0.05)；二十碳五烯酸(EPA)含量J2、J3组显著高于J1组(P<0.05)；DHA∶EPA比值J1组显著高于J2、J3组(P<0.05)。各组SFA无显著性差异(P>0.05)，MUFA含量J3组>J2组>J1组(P<0.05)；PUFA含量J3组显著高于J1、J2组(P<0.05)。PUFA/SFA、n-3/n-6比值J2、J3组显著高于J1组(P<0.05)，J2、J3组无显著性差异(P>0.05)。h/H比值J3组显著高于J1、J2组(P<0.05)。

表 5 3种规格黄鳍金枪鱼肌肉脂肪酸组成 Tab.5 Fatty acid composition of muscle in three different sizes of yellowfin tuna/%
2.4 矿物质元素的组成比较

3种规格黄鳍金枪鱼肌肉中矿物质元素见表 6，4种常量元素中Na、Ca的含量J2、J3组显著高于J1组(P<0.05)，K含量J1组最高且显著高于J2、J3组(P<0.05)；各组Mg含量无显著性差异(P>0.05)。4种重金属元素均低于WHO (1989)或FAO (1998)食品中规定的最大允许限量，Fe含量最大的为J3组，且J3组>J2组>J1组(P<0.05)；Cu含量最大的为J3组，且显著高于J1组(P<0.05)，各组Mn、Zn含量无显著性差异(P>0.05)。

表 6 3种规格黄鳍金枪鱼肌肉中矿物质元素(常量元素、微量元素)含量 Tab.6 Concentrations of macro and micro mineral elements in the muscle of three different sizes of yellowfin tuna /(mg/kg)
3 讨论 3.1 3种规格黄鳍金枪鱼常规营养成分的分析

鱼类肌肉成分的96%~98%由水分、蛋白质、脂肪和灰分构成(Rani et al, 2016)，鱼体成分是检验鱼的质量、营养品质、生理状态等的重要指标(Ravichandran et al, 2011)。在本研究中，黄鳍金枪鱼肌肉粗脂肪含量(0.51~0.64 g/100 g)和粗蛋白质含量(25.43~26.89 g/100 g)与大眼金枪鱼(粗脂肪0.6 g/100 g，粗蛋白23 g/100 g)、鲣鱼(Katsuwonus pelamis) (粗脂肪0.6 g/100 g，粗蛋白25.9 g/100 g)等相近(Venugopal et al, 1996)。黄鳍金枪鱼粗蛋白与粗脂肪含量随规格的增大而增加，这与全周期人工养殖蓝鳍金枪鱼(Nakamura et al, 2007)、布氏鳠(Mystus bleekeri) (Naeem et al, 2011)等的研究结果相似；Venugopal等(1996)研究认为，大部分鱼类肌肉组织中脂肪含量变化与其水分含量变化呈负相关，这也与本研究结果相似。关于不同规格鱼体组分的差异，影响因素较多，通常主要归结于摄入的食物、鱼代谢率及运动量(Ahmed et al, 2022)，黄鳍金枪鱼不同生长阶段鱼类摄食的食物存在差异(朱国平等, 2008; 陶雅晋等, 2017)，食物对鱼体组成有很大影响，鱼类通常会食用各种各样的食物，并利用这些食物获取对其正常生长和发育必需的营养物质(Koizumi et al, 2009; 刘峰等, 2018)。此外，不同生长阶段金枪鱼的代谢率及运动量变化较大(Graham et al, 2004)，这些都可能导致鱼体组分的差异。

3.2 3种规格黄鳍金枪鱼氨基酸含量的比较与营养分析

氨基酸是构建细胞、修复组织的基础材料，是评价食物营养价值的重要指标(Ahmed et al, 2022)。许多氨基酸在人体新陈代谢过程中发挥重要作用，谷氨酸对细胞增殖至关重要，而赖氨酸在促进人体生长发育、增强机体免疫力等方面发挥重要作用，是人类第一限制性氨基酸(丁德明等, 2021)。在本研究中，3种规格黄鳍金枪鱼含量最高的氨基酸均为谷氨酸(3.04~3.25 g/100 g)，必需氨基酸中含量最高的为赖氨酸(2.02~2.15 g/100 g)，最低的为色氨酸(0.31~0.45 g/100 g)，这与Peng等(2013)的研究结果相近。必需氨基酸的相对含量是决定食物蛋白质营养价值的重要因素，本研究中，不同规格黄鳍金枪鱼EAA/TAA比值无显著性差异，比值在40.81%~41.81%之间，略高于蓝鳍金枪鱼(37.90%~39.01%)(赵玲等, 2023)，符合FAO/WHO要求，均高于不同年龄人群需求的报告值(即婴儿为39%，儿童为26%，成人为11%) (Oluwaniyi et al, 2010)，因此，黄鳍金枪鱼是很好的氨基酸来源。呈味氨基酸是鱼肉风味的重要指标，本研究中，天冬氨酸、谷氨酸、甘氨酸、丙氨酸4种呈味氨基酸均随着规格的增大而增加，这与杂交鲟(Acipenser schrenckii×Acipenser baerii)研究结果一致(杜强等, 2017)，这说明大规格金枪鱼口感更好。

依据AAS评分，缬氨酸为第一限制性氨基酸，J1、J2组第二限制性氨基酸为苏氨酸，J3组为亮氨酸；以CS为评分标准，J1、J2组第一、第二限制性氨基酸分别为色氨酸、苯丙氨酸+酪氨酸，J3组第一、第二限制性氨基酸分别为苯丙氨酸+酪氨酸、缬氨酸，这说明不同规格黄鳍金枪鱼的限制性氨基酸并不完全相同，限制性氨基酸可能与鱼的大小、环境、食物，甚至取样部位等因素相关(程辉辉等, 2016; 刘书臣等, 2013)。蛋白质是鱼类人工饲料中最昂贵的成分，有研究表明，饲料中缺乏某些重要氨基酸，鱼会出现生长停滞、厌食等症状(Ahmed, 2010)，饲料中合理的蛋白质及氨基酸的搭配对促进鱼类的生长及增强鱼体免疫力具有重要作用(Craig et al, 2017; Ahmed et al, 2006)。因此，通过研究黄鳍金枪鱼氨基酸组成，确定在不同生长阶段蛋白质及氨基酸的需求量对人工养殖黄鳍金枪鱼营养饲料的研制具有重要参考价值。

3.3 3种规格黄鳍金枪鱼脂肪酸的比较与营养分析

PUFA含量是评价鱼类营养价值的重要指标之一，尤其是二十碳五烯酸(EPA, 20:5n-3)和二十二碳六烯酸(DHA, 22:6n-3)，他们在体内和体外的多种生化过程中发挥着重要作用(Calder, 1997)，包括提高学习能力、促进大脑的发育，增强免疫力，降低高血压、动脉粥样硬化和某些癌症等疾病的发生等具有重要作用(Bucher et al, 2002; Damsgaard et al, 2007)，黄鳍金枪鱼肌肉中各脂肪酸含量以PUFA为主，DHA为主要脂肪酸，含量达37.46%~39.19%，远高于石斑鱼(Epinephelus spp.) (王林娜等, 2018)及卵形鲳鲹(Trachinotus ovatus) (罗辉等, 2020)等常见海水鱼，且大规格黄鳍金枪鱼的PUFA、EPA、DHA含量高于小规格鱼，这与苏氏圆腹(Pangasius sutchi)研究结果相似(韦玲静等，2020)。此外，在本研究中，黄鳍金枪鱼DHA∶EPA比值7.30~8.71，高于大部分已研究过的鱼类(Hossain, 2011)，相对较高的DHA和DHA∶EPA比率可能是金枪鱼物种的一个特征，在大多数饲料配方的鱼油中，DHA∶EPA比值很少超过2，海洋鱼类将EPA转化为DHA的能力有限(Sargent et al, 1995)，这些都可能对金枪鱼人工营养饲料的配方产生影响。

某些饱和脂肪酸如C12:0、C14:0和C16:0等会增加血清总胆固醇(Ulbricht et al, 1991)，因此，PUFA/SFA、h/H比值常用于评估食物的营养质量(Chen et al, 2020)，其数值越高越有助于降低心血管和其他慢性疾病发生的风险。n-3/n-6比值是比较不同鱼种脂肪酸相对营养价值的较好指标，食物中n-3/n-6比例高的鱼是有益的(Guler et al, 2011)，根据健康饮食建议，n-3/n-6比值高于4能降低食物相关的慢性病的发生(Økland et al, 2005)。在本研究中，J2、J3组PUFA/SFA比值明显高于J1组；h/H比值J3组显著高于J1、J2组；各组n-3/n-6比值均大于4，且J2、J3组显著高于J1组。通过对3种不同规格黄鳍金枪鱼PUFA/SFA、h/H和n-3/n-6的比较表明，大规格黄鳍金枪鱼具有更好的营养质量。

3.4 3种规格黄鳍金枪鱼矿物质元素的分析

水生生物从环境中积累和保留的矿物质是高度选择性的，鱼类肌肉矿物质浓度受到许多因素的影响(Karunarathna et al, 2009)。在本研究中，Na和K的平均浓度分别在173.36~268.34 mg/kg和719.52~ 785.58 mg/kg之间，与养殖的大部分海水鱼含量差异较大(刘芳芳等, 2019)，Na∶K比在1∶3到1∶4之间，这与大部分金枪鱼的Na、K比相似(Karunarathna et al, 2009)，在食品中比例适当，适合食用。

重金属存在于水生环境中，可以沿着食物链积累，Cu、Fe和Zn等重金属在低浓度时是生物体代谢所必需的，但在高浓度时可能是有毒的(Chan et al, 2019)，金枪鱼等食肉鱼类比非食肉物种能积累更多的重金属。金枪鱼Fe含量范围为2.7~80.0 mg/kg，且各部位差异显著，含量最高的部位为红肌(Karunarathna et al, 2009)。本研究中，Fe含量在2.83~5.67 mg/kg之间，随规格的增加，黄鳍金枪鱼肌肉铁含量随着增大；Cu含量最大的为J3组0.75 mg/kg，且显著高于J1组；各组的Mn和Zn无显著差异。WHO (1989)和FAO (1998)关于鱼类食品中Cu的最大允许限量分别为30 μg/g和10~100 μg/g，Zn的最大允许限量分别为100 μg/g和30~100 μg/g (Mokhtar et al, 2009)，黄鳍金枪鱼肌肉重金属Cu、Zn浓度远低于食品中规定的最大允许限量。

通过对3种不同规格黄鳍金枪鱼氨基酸、脂肪酸的分析，黄鳍金枪鱼具有较好的营养质量，大规格金枪鱼呈味氨基酸含量更高，同时其PUFA/SFA、h/H和n-3/n-6比值更高，这说明大规格金枪鱼口感更好，更适合食用。在人工养殖下金枪鱼营养饲料配制时应考虑不同生长阶段氨基酸及脂肪酸的需求量，同时金枪鱼肌肉具有相对较高的DHA和高DHA∶EPA比率，须注意在饲料中补充。

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