Tuna Protein Nutritional Quality Changes after Canning

Albacore tuna (Thunnus alalunga) was steamed and canned in soy bean oil and sterilized at 115°C for 55 or 90 min. Proximate composition, total amino acid and available lysine content were determined during different phases of the process. Water and protein were lost in all phases and fat content increased. There was a decrease in available lysine during cooking but no loss in total amino acids. Nutritional evaluation of the protein showed differences in biological value and net protein utilization when the canned tuna was mixed with bread flour.     

Bioactive properties of enzymatic hydrolysates from abdominal skin gelatin of yellowfin tuna (Thunnus albacares)

Gelatin (90.6 ± 0.1%) was optimally prepared by response surface methodology from yellowfin tuna (Thunnus albacares, YT) abdominal skin. To investigate bioactive properties of enzymatic hydrolysates from the abdominal skin gelatin (ASG), ASG was hydrolysed with alcalase, protamex, neutrase and flavourzyme as affected by hydrolysis time. Antioxidant, nitrite scavenging and angiotensin‐I converting enzyme (ACE) inhibitory activities of the hydrolysates were determined. Antioxidant activities of the hydrolysates were found through linoleic acid peroxidation inhibitory effects. Alcalase‐derived hydrolysates (AHs) were more effective than others in metal ions chelating, superoxide anion scavenging and hydroxyl radical scavenging activities (P < 0.05). AHs showed significantly stronger nitrite scavenging activities (44.4–60.7%) than others (P < 0.05). Fraction A from AH showed strong ACE inhibitory activity (IC₅₀ of 0.75 mg mL^?1). These results suggest that YT ASG and its enzymatic hydrolysates could be functional food and/or pharmaceutical ingredients with potent antioxidant, anticarcinogenic and antihypertensive benefits.     

Angiotensin I‐converting enzyme inhibitory and Ca‐binding activities of peptides prepared from tuna cooking juice and spleen proteases

Tuna cooking juice is a by‐product from the tuna canning industry. In this study, tuna cooking juice was hydrolysed by proteases extracted from the spleen. Tuna cooking juice showed the highest ACE inhibitory and Ca‐binding activities after hydrolysis for 270 and 180 min, respectively. The hydrolysate was further fractionated by ultrafiltration. The permeate exhibited highest ACE inhibitory and Ca‐binding activities when passed through 1 and 5 kDa cut‐off membranes, respectively. Gel filtration chromatography was used to determine the MW of bioactive peptides that exhibited highest ACE inhibitory and Ca‐binding activities. Those peptides that exhibited highest ACE inhibitory and Ca‐binding activities were the MW range of 238–829 Da and 1355–1880 Da, respectively. These results suggest that the tuna cooking juice and the spleen protease extract are a potential source of bioactive peptides that can be utilised as bioactive ingredients in functional food and nutraceuticals.     

金枪鱼鱼松的工艺研究

研究金枪鱼的营养成分、鱼肉脱腥方法,并研究了全营养金枪鱼鱼松加工工艺。因金枪鱼肉中脂肪含量高,使鱼肉制品存在鱼腥味,采用萃取法脱去鱼肉中的脂肪,去脂率高达95%。试验结果表明,金枪鱼富含蛋白质、DHA、EPA和矿物质;各因素对调味配方影响的主次顺序为:D>A>C>B,即最适宜的调味配方为盐1.5%、糖3.0%、大豆分离蛋白5.0%、姜汁3.0%、葱汁1%、味精1%、油3%;各因素对鱼松工艺影响的主次顺序为A>D>C>B,即最佳处理工艺为压榨水分55%,蒸煮时间75 min,初炒时间10 min。     

不同模拟运输条件对金枪鱼品质的影响

研究了黄鳍金枪鱼背部肌肉,在2种不同温度(4℃和20℃)下模拟运输4 h,观察其背部肌肉颜色(a*),鲜度(TVB-N值、K值)、pH、感官及微生物的变化。结果表明,温度是保证质量的关键,4℃在4 h内保持良好的鲜度和颜色,而20℃运输4 h后肉的颜色和新鲜度差异较大(p<0.05),因此在运输中应尽可能保持较低的温度。     

基于虚拟仪器技术的渔船超低温冷库制冷监控系统研究

为了解决金枪鱼渔船超低温制冷控制系统自动化程度低,监控效果不理想和监控条件恶劣等问题,提出采用虚拟仪器技术,基于LabVIEW平台设计开发了一套金枪鱼渔船超低温冷库制冷监控系统,实现了冷库机组数据的实时监测、数据及动态曲线的显示、数据的处理及保存、系统控制参数的设定、电子膨胀阀实时状态检测和电子膨胀阀控制及输出显示等功能。试验结果表明:该系统运行稳定,自动化程度高,测控及时准确,人机交互界面友好,操作简单,功能完善。     

金枪鱼头的营养成分及其蛋白酶解物的应用

对黄鳍金枪鱼鱼头的营养成分进行了分析，并对其蛋白质营养价值进行了评价。结果显示，金枪鱼头粗蛋白含量干基计为68．0％，脂肪27．2％，含有丰富的钠和钙；根据1973年FAO／WHO推荐的必需氨基酸需要量模式对金枪鱼头蛋白进行评价，氨基酸评分为60，第一限制性氨基酸为色氨酸。用木瓜蛋白酶和风味酶双酶同时酶解金枪鱼头蛋白，酶解液经调配制得营养液，其总氮为1．02g／100mL，氨基酸总量为986．81mg／100mL。     

Identification and quantification of cholesterol oxidation products in canned tuna

Cholesterol oxidation in tuna canned in brine was studied. Gas chromatography-mass spectrometry was used for the detection of the seven major cholesterol oxidation products originating from both direct and indirect oxidation. The total amount of cholesterol oxidation products in the analyzed samples varied considerably, ranging between 40 and 350 μg/g lipids, with the exception of an anomalous sample, that reached a 1600 μg/g level. The lipid content ranged between 0.5 and 1 g/100 g wet product. As most samples did not exceed 100 μg/g lipids, it is possible to assume that the total content of cholesterol oxidation products can be kept below this value if good manufacturing conditions are used, together with a careful choice of the best tuna cuts. The application of principal component analysis to the detected variables confirmed that 7-ketocholesterol is a useful index of the whole oxidation process.     

冻贮温度对生食金枪鱼品质变化的影响

研究普通冻贮条件下金枪鱼品质变化规律。以大目、黑鳍和红鳍3 种金枪鱼前腹肉为研究对象,以高铁肌红蛋白含量、硫代巴比妥酸反应活性物质（thiobarbituric acid reaction substances,TBARs）值、鲜度指标K值、pH值为检测指标,研究其在－18、－30 ℃条件下金枪鱼品质随时间的变化规律。结果表明：随着贮藏时间的延长,3 种金枪鱼的pH值、鲜度指标K值、TBARs值及高铁肌红蛋白含量等指标均呈现上升趋势,且－18 ℃条件下贮藏的金枪鱼各项指标的变化速率明显高于－30 ℃条件下贮藏的金枪鱼;相较于TBARs和K值,高铁肌红蛋白含量更能反映金枪鱼生食产品的食用品质;－18 ℃冻贮金枪鱼14 d时高铁肌红蛋白含量已超过30%,金枪鱼颜色由红色向红褐色转变,感官品质明显劣化,而－30 ℃冻贮条件下则可达28 d。