Lipid class and fatty acid composition of phospholipids from the gonads of skipjack tuna

ABSTRACT:   Lipid class and fatty acid composition of phospholipids from the gonads of skipjack tuna were examined to evaluate effective utilization of the processing of by-products. The predominant phospholipids in the ovaries were phosphatidylcholine (PC; 47.9%), phosphatidylethanolamine (PE; 19.3%) and lyso-phosphatidylcholine (LPC; 19.1%). In contrast, those in the testes were PC (40.1%), PE (29.3%) and phosphatidylserine (PS; 9.6%). The percentage of docosahexaenoic acid (DHA) was markedly high at more than 50% in LPC of the ovaries, and PE and PS of the testes were also high. The percentages of DHA at sn-position 2 of the predominant phospholipids, except for PC in the testes, were more than 60%, in particular PE in the testes was remarkably high at 81.9%. After storage for 2 days at 5°C, the LPC content in the ovaries increased twofold and the DHA level of LPC was the same as before, though the contents of other phospholipids decreased.     

Quality improvement by vacuum treatment of boiled skipjack loins for the production of dried skipjack

ABSTRACT: This study attempted to reduce the lipid and water contents in boiled skipjack loins by vacuum treatment and the quality of vacuumed boiled meat was then evaluated during the chilled and frozen storage. The boiled meats were vacuumed at a pressure of 400 Pa for 30 min using a vacuum freeze dryer as an experimental convenience in order to degrease, cool and dehydrate rapidly. The vacuumed boiled meats were stored at 0.0 ± 0.2°C for 10 days and at −20 ± 0.5°C for 90 days. The unvacuumed boiled meats were cooled by air-cooling and stored as the control. Lipid content on a wet basis (w.b.) was reduced as much as 0.5% in the ventral part and 0.4% in the dorsal part of the boiled meats after vacuum treatment. Water content (w.b.) was reduced as much as 2.5% in the ventral part and 3.0% in the dorsal part. The thiobarbituric acid and volatile basic nitrogen values in vacuumed boiled meats were significantly lower ( P < 0.05) than that in unvacuumed boiled meats during storage. Inosine monophosphate (IMP) was only detected as a major nucleotide (about 70%) in boiled meats, and the decomposition of IMP in vacuumed boiled meats was smaller than that in unvacuumed boiled meats during storage. It was concluded that the quality of boiled skipjack loins could be improved by vacuum treatment as a preprocessing procedure in the production of dried skipjack such as katsuobushi .     

The relationship between the skipjack tuna (Katsuwonus pelamis) fishery and seasonal temperature variability in the south-western Atlantic

The spatio‐temporal distribution of tuna fishing effort has been related to oceanographic circulation and features in several seas of the world. Understanding the relationship between environmental variables and fishery resource dynamics is important for management decisions and to improve fishery yields. The relationship between sea temperature variability and the pole‐and‐line skipjack tuna (Katsuwonus pelamis) fishery in the south‐western Atlantic Ocean was investigated in this work. Data from logbooks, satellite images (sea surface temperature), and oceanographic surveys were used in the analyses. Skipjack are caught in warm tropical waters of the Brazil Current (BC). The north–south displacement of fishing effort was strongly associated to seasonal variation of the surface temperature, which was coupled to the tropical BC flow. Oceanographic fronts from autumn to spring and a shallow thermocline in summer probably induces the aggregation of skipjack schools over the shelfbreak, favouring fishing operations. Hypotheses are proposed to explain the relationship between peaks of fishing events and the presence of topographic peculiarities of the shelfbreak.     

猪里脊肉烹饪终点成熟值的测定

为测定烹饪综合终点成熟值及成熟品质因子的zM值,在选定的不同试验条件下,以猪里脊肉为对象,针对其颜色、气味、口感3种成熟品质,采用感官评价差异检验中的选择法从具有不同成熟值的一系列样品中确定成熟样,对成熟样的成熟值求平均,获得相应的平均终点成熟值,结合专家给予的权重,加权平均得到综合终点成熟值。通过成熟品质因子的zM不同取值,得到各系列的终点成熟值的标准偏差,其值最小时则为合理的zM值。试验结果证实了对特定来源和特定的人群,终点成熟值存在且稳定,原料种类、厚度、形状、初始温度、不同油温和加热介质种类等因素对其影响符合成熟值理论的定义,支持了成熟值理论。A偏红和B偏白的猪里脊肉的综合终点成熟值分别为0.51和0.31 min,成熟品质因子的zM值为10℃。     

熟制中华绒螯蟹在冻藏过程中的品质变化

为了研究中华绒螯蟹在冻藏期间的品质变化,通过感官和理化指标判断冷冻蟹膏蟹黄和蟹肉的赏味期分别为180 d和240 d;180 d时蟹膏蟹黄腥味和油耗味过重,蟹肉在240 d时不被接受是由于氨味和腥味过重;使用固相微萃取(solid-phase microextraction,SPME)和气相色谱质谱联用仪(gas chromatography-mass spectrometer,GC-MS)萃取并检测中华绒螯蟹在冻藏期间的挥发性气味物质,利用气味活性值(odor activity value,OAV)筛选发现中华绒螯蟹在冻藏过后对气味影响最主要的物质是苯甲醛、壬醛、2,6-壬二烯醛、1-辛烯-3-醇、2,4-癸二烯醛和三甲胺。     

Using historical fisheries data to predict tuna distribution within the British Indian Ocean Territory Marine Protected Area,and implications for its management

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