Rheological and Structural Properties of Sea Cucumber Stichopus japonicus During Heat Treatment

Changes in tissue structure, rheological properties and water content of raw and heated sea cucumber meat were studied. Sea cucumber Stichopus japonicus was heated at 25℃, 70℃ and 100℃ water for 5 min. The structural changes were observed using a light microscope and the rheological parameters （rupture strength, adhesive strength and deformation） determined using a texture meter. Microscopic photograph revealed that the structural change of heated meat was greater than that of raw meat. The rupture strength, adhesive strength and deformation of raw meat were smaller than those of the heated meat. Meanwhile, rheological parameters showed positive correlation with heating temperature. These changes are mainly caused by thermal denaturation and gelatinization of collagen during heating. These changes were also evidenced in observations using a light microscope and differential scanning calorimetry.     

Starvation on changes in growth and fatty acid composition of juvenile red swamp crawfish, Procambarus clarkii

The effect of starvation on physiological and biochemical indicators of body, muscle and hepatopancreas were investigated for juvenile red swamp crawfish (Procambarus clarkii), and the results showed the effect was obvious. In a 70-day starvation experiment, mean body weight, exuvial rate, ab- dominal muscle ratio and hepatosomatic index decreased significantly. The percentage of protein, fat, ash and moisture were also significantly affected. The protein content decreased sharply at Day 30 onward and the percentage of fat decreased rapidly from Day 50 and on. The percentages of ash and moisture started to increase significantly at Day 40 and 30 respectively. After the starvation experiment, the hepa- topancreatic total and neutral lipid content decreased slightly from 23.90% to 20.39% and 73.75% to 70.35%, while the hepatopancreatic polar lipid content increased from 23.81% to 27.32%. On the other hand, all the muscular total, neutral and polar lipid contents, and the muscular fatty acid compositions did not change significantly except for the hepatopancreatic fatty acid composition. The relative percentages of 14:0, 16:0, 16:1n-7 and 18:1n-9 were decreased by 55.17%, 11.11%, 8.5% and 6.70% from the initial values, and the relative percentages of 18:2n-6, 18:3n-3, 20:4n-6, 20:5n-3 and 22:6n-3 increased obvi- ously from 5.2%, 3.9%, 2.4%, 10.6%, and 13.7% to 7.1%, 5.0%, 2.8%, 11.5%, and 14.4% respectively. Preference of utilization of fatty acids from hepatopancreas during starvation was as follows: 14:0>16:0>16:1n-7>18:1n-9, and the conservation of highly unsaturated fatty acids was in the order of: 18:2n-6 >18:3n-3>20:4n-6>20:5n-3>22:6n-3.     

Cloning of the cDNA encoding adenosine 5′-monophosphate deaminase 1 and its mRNA expression in Japanese flounder Paralichthys olivaceus

AMP deaminase catalyzes the conversion of AMP into IMP and ammonia. In the present study, a full-length cDNA of AMPD1 from skeletal muscle of Japanese flounder Paralichthys olivaceus was cloned and characterized. The 2 526 bp cDNA contains a 5’-UTR of 78 bp, a 3’-UTR of 237 bp and an open reading frame (ORF) of 2 211 bp, which encodes a protein of 736 amino acids. The predicted protein contains a highly conserved AMP deaminase motif (SLSTDDP) and an ATP-binding site sequence (EPLMEEYAIAAQVFK). Phylogenetic analysis showed that the AMPD1 and AMPD3 genes originate from the same branch, but are evolutionarily distant from the AMPD2 gene. RT-PCR showed that the flounder AMPD1 gene was expressed only in skeletal muscle. QRT-PCR analysis revealed a statistically significant 2.54 fold higher level of AMPD1 mRNA in adult muscle (750±40 g) compared with juvenile muscle (7.5±2 g) (P<0.05). HPLC analysis showed that the IMP content in adult muscle (3.35±0.21 mg/g) was also statistically significantly higher than in juvenile muscle (1.08±0.04 mg/g) (P<0.05). There is a direct relationship between the AMPD1 gene expression level and IMP content in the skeletal muscle of juvenile and adult flounders. These results may provide useful information for quality improvement and molecular breeding of aquatic animals.     

盐度对点带石斑鱼生长、肌肉成分和消化率的影响

设计盐度为5,10,15,20,25的5个水平,饲养平均体质量为21.91 g±0.23 g的点带石斑鱼(Epine-phlus coioides)56 d,研究盐度对点带石斑鱼生长、肌肉成分和消化率的影响.结果表明,不同盐度对点带石斑鱼生长有显著影响(P<0.05),盐度为15～20时,点带石斑鱼增质量率、蛋白质效率较高,饲料系数较低;盐度为5时点带石斑鱼增质量率、蛋白质效率最低,饲料系数最高.不同盐度的各组之间点带石斑鱼肌肉水分、粗蛋白、粗脂肪含量差异不显著(P>0.05).不同盐度对点带石斑鱼内脏比、丰满度有显著影响,盐度为15,20时,点带石斑鱼内脏比值较小、丰满度值较大,与其他各组差异显著(P<0.05).随着盐度的增加(5～20),点带石斑鱼干物质消化率与蛋白质消化率有上升趋势,但是盐度增加到25时,消化率下降.实验证明,点带石斑鱼的最适生长盐度为15～20.     

Determination of nitrate in the blood of the hydrothermal vent tubeworm Riftia pachyptila using a bacterial nitrate reduction assay

The vestimentiferan tubeworm Riftia pachyptila derives most or all of its nutrition from intracellular chemosynthetic bacterial symbionts. Because purified preparations of symbionts respire nitrate, possibly nitrite, and oxygen, host transport of nitrate is a topic of interest. In the present study, we have developed a nitrate detection assay that utilizes a nitrite reductase-deficient Escherichia coli strain for the reduction of nitrate to nitrite, which is then determined spectrophotometrically. Nitrate and nitrite concentrations were measured in the blood and coelomic fluids of R. pachyptila collected from hydrothermal vent sites at 9°N and 13°N. The blood was shown to have nitrate concentrations up to one hundred times that of ambient sea water (40 μM). Blood nitrate levels reached concentrations of>1 mM, while nitrite was measured in the range of 400-700 μM. The concentrations of nitrate and nitrite in the coelomic fluids were 150-240 μM and <20 μM, respectively. The nitrate determination technique we present here is simple, applicable for laboratory and shipboard use on sea water or biological fluids, and works reliably within the 0.5 to 2000 μM range.     

大黄鱼(Pseudosciaena crocea)Cathepsin L基因cDNA片段的克隆与稳定性研究

采用RACE-PCR和RT-PCR方法获得大黄鱼组织蛋白酶L(Cathepsin L)基因的cDNA中间片段,片段长度为773bp。BLAST分析显示,大黄鱼Cathepsin L基因cDNA片段与鱼的同源性最高达到95%,与斑马鱼同源性为80%。实时定量分析了大黄鱼Cathepsin L基因在宰杀当天和冷藏期间的mRNA水平,结果表明,大黄鱼0℃条件下冷藏0、5、10、15、20d肌肉中mRNA都具有相对稳定性,但是含量水平有差异并且是呈现下降趋势,宰杀当天的大黄鱼肌肉中Cathepsin L基因mRNA含量水平最高,与冷藏5、10、15、20d的Cathepsin L基因mRNA水平差异性极显著(P<0.01),冷藏5d的Cathepsin L基因mRNA水平与15、20d的水平也达到了极显著水平(P<0.01)。同时结果表明,在不同储藏时间Cathepsin L基因的mRNA含量水平与肌肉TPA和pH等也表现了高度的相关性,表明Cathepsin L基因的mRNA含量可以作为评价大黄鱼冷藏期间肉品质指标的可行性和准确性。     

Lipid and Fatty Acid Compositions of Cod(Gadus morhua),Haddock(Melanogrammus aeglefinus)and Halibut(Hippogiossus hippoglossus)

This study was conducted to compare lipid and fatty acid composition of cod,haddock and halibut.Three groups of cod(276 g±61 g),haddock(538 g±83 g)and halibut(3704 g±221 g)were maintained with commercial feeds mainly based on fish meal and marine fish oil for 12 weeks prior to sampling.The fatty acid compositions of muscle and liver were determined by GC/FID after derivatization of extracted lipids into fatty acid methyl esters(FAME).Lipids were also fractionated into neutral and polar lipids using Waters silica Sep-Pak(R).The phospholipid fraction was further separated by high-performance thin-layer chromatography(HPTLC)and the FAME profile was obtained.Results of the present study showed that cod and haddock were lean fish and their total muscle lipid contents were 0.8% and 0.7%,respectively,with phospholipid constituting 83.6% and 87.5% of the total muscle lipid,respectively.Halibut was a medium-fat fish and its muscle lipid content was 8%,with 84% of the total muscle lipid being neutral lipid.Total liver lipid contents of cod,haddock and halibut were 36.9%,67.2% and 30.7%,respectively,of which the neutral lipids accounted for the major fraction(88.1%-97.1%).Polyunsaturated fatty acids were the most abundant in cod and haddock muscle neutral lipid.Monounsaturated fatty acid level was the highest in halibut muscle neutral lipid.Fatty acid compositions of phospholipid were relatively constant.In summary,the liver of cod and haddock as lean fish was the main lipid reserve organ,and structural phospholipid is the major lipid form in flesh.However,as a medium-fat fish,halibut stored lipid in both their liver and muscle.     

冷冻贮藏对罗非鱼肌肉质构特性的影响

采用质构仪的TPA模式对冷冻贮藏罗非鱼肌肉的硬度、黏附性、弹性、咀嚼性、胶黏性、凝聚性和恢复性等进行测试。结果表明:在-18℃和-50℃的贮藏条件下,随着贮藏时间的增加,罗非鱼肌肉质构的硬度、弹性、咀嚼性、胶黏性、凝聚性、恢复性等6个参数均呈不同程度的下降趋势,黏附性则呈上升趋势;-50℃贮藏的罗非鱼肌肉的质构参数变化速率低于-18℃贮藏条件。说明罗非鱼在冷冻贮藏过程中口感特征在不断下降,贮藏温度越低,越有利于保持罗非鱼肌肉的质构特征。     

雌雄短吻新银鱼肌肉营养成分的比较分析及评价

对雌雄短吻新银鱼肌肉营养成分进行了比较分析。结果表明:雌性短吻新银鱼肌肉鲜样中粗蛋白显著低于雄性(P<0.05),粗灰分极显著低于雄性(P<0.01),而雌雄水分和粗脂肪含量无显著差异(P>0.05);短吻新银鱼肌肉样品中均测出18种氨基酸,但在含量上雄性短吻新银鱼绝大多数氨基酸均显著高于雌性(P<0.05)。其中雌雄短吻新银鱼肌肉干样中鲜味氨基酸(DAA)总量分别为26.43%、30.47%,占氨基酸总量的分别35.23%、35.83%。以氨基酸评分(Amino acid score)进行评价,雌雄短吻新银鱼的第一限制性氨基酸均为缬氨酸,第二限制性氨基酸为色氨酸,而以CS进行评价时,雌雄短吻新银鱼的第一限制性氨基酸均为色氨酸,第二限制性氨基酸为缬氨酸。雌雄短尾新银鱼的必需氨基酸指数(Essential acid score index)分别为89.51、93.13,构成比例符合FAO/WHO规定的优质蛋白质标准。雌短吻新银鱼鲜味氨基酸总量、必需氨基酸含量,氨基酸总量、DHA的比例显著低于雄性短吻新银鱼(P<0.05)。表明雄性短吻新银鱼的营养价值较雌性银鱼丰富,具有较高的食用价值和保健作用。     

南海野生斑节对虾亲虾卵巢发育过程中的脂肪酸组成

采用生物学和生理生化方法研究我国南海北部野生斑节对虾Penaeus monodon亲虾在卵巢发育不同阶段的卵巢、肝胰腺和肌肉的脂肪酸(fatty acid,FA)组成及变化规律.结果发现,亲体肝胰腺、卵巢和肌肉的脂肪酸中棕榈酸(16:0,17.61%-33.6%)、棕榈油酸(16:1n-7,8.08%-14.36%)、18:0(6.46%-17.15%)、油酸(18:1n-9,9.64%-18.81%)、花生烯酸(20:4n-6,arachidonic acid,ARA,4.8%-10.83%)、二十碳五烯酸(20:5n-3,eicosapntemacniocacid,EPA,4.64%-11.98%)及二十二碳六烯酸(22:6n-3,docosahexaenoic acid,DHA,2.23%-9.3%)占主要比例.在卵巢发育不同阶段,卵巢中的12:0、14:0、16:0、18:0、20:0及总的饱和脂肪酸(saturation fatty acid,∑SFA)的含量逐渐上升,成熟期达到最高,产卵后下降;肝胰腺16:0和饱和脂肪酸(∑SFA)呈波动上升趋势;肌肉中的14:0、16:0、18:0、20:0及∑SFA呈现出先下降后升高的变化,在接近成熟期(Ⅳ-Ⅴ)降到最低,产卵后回升到最高.在肝胰腺、卵巢、肌肉组织发育过程中,16:1、18:1n-7和单不饱和脂肪酸(mono unsaturation fatty acid,∑MUFA)的含量均呈现波浪式上升,成熟期(Ⅴ)达到最高.18:2n-6、ARA及n-6 FA含量起伏波动,先升后降,成熟前期(Ⅲ-Ⅳ)达到最大值,在成熟期达到最小值.卵巢中EPA、n-3 FA呈现出下降趋势,成熟期(Ⅴ)接近最低,EPA、DHA及总的n-3 FA和多不饱和脂肪酸(poly unsaturation fatty acid,∑PUFA)含量在卵黄囊发生期(Ⅲ)波动上升达到最大值,之后逐步下降,Ⅵ期(产卵后)最低或回落到未成熟期水平.DHA/EPA、∑n-3/n-6及∑PUFA/SFA的比值波动变化,在卵黄囊发生期(Ⅲ)或成熟期(Ⅳ-Ⅴ)上升达到最大值,之后逐步下降,Ⅵ期(产卵后)最低或恢复到未成熟期(Ⅰ)水平.在自然海区性成熟的斑节对虾亲体组织中,∑SFA:∑MUFA:∑PUFA比例近似为35%:30%:35%:n-3与n-6、∑PUFA与∑SFA及DHA与EPA达到近似的平衡状态.研究结果为斑节对虾亲虾人工配合饲料的配制提供了参考依据.