不同温度波动对冻藏三文鱼色差和质构的影响

以超低温[(-50±0.1)℃]冷冻三文鱼为对照,研究低温(-18℃)环境条件下的不同温度波动(±2、±1、±0.5℃)条件下三文鱼的质构(硬度,弹性,咀嚼性,嫩度)、色差、感官等理化指标的变化,探究不同温度波动幅度对冷冻三文鱼品质的影响,以及与超低温[(-50±0.1)℃]冷冻下品质的对比。结果表明,三文鱼色差随着冻藏时间的延长而不断增大,三文鱼的咀嚼度、硬度、弹性等质构特性随贮藏时间的延长而显著降低;-18℃冻藏条件下温度波动幅度对三文鱼的色差、质构(弹性、硬度、咀嚼性、嫩度)影响的差异显著(P<0.05),与(-18±2)℃、(-18±1)℃组相比,(-18±0.5)℃可将贮藏时间延长1~2个月;短期贮藏时,减小温度波动幅度至±0.5℃,保证相同冻结率的情况下,可将三文鱼的冻藏温度从-50℃提高至-18℃;三文鱼的质构特性(硬度,弹性,咀嚼性,嫩度)之间相互影响,且相关系数均大于0.84。以冻藏时间和温度波动幅度为自变量,以弹性、咀嚼度、嫩度为因变量,建立三文鱼质构特性的多元线性回归拟合方程,为建立货架期预测提供依据。

基于吊装运输条件的预制箱涵结构合理划分的研究

为指导预制装配式混凝土箱涵(以下简称“预制箱涵”)结构的合理划分,依据现有规范、标准及工程应用分析,开展预制箱涵结构纵向及横向合理划分的研究。结果表明:预制箱涵构件重量宜控制在20~25 t,其结构尺寸应满足运输尺寸限值要求,节段划分长度宜为1 m、1.5 m、2 m、3 m和6 m;据此提出各截面尺寸型式的预制箱涵构件结构合理划分结果及运输方式。为小型装配式桥涵的标准化设计与施工提供了技术支撑。

微塑料对两种硅藻生长以及二甲基硫产生的影响

本论文研究了聚苯乙烯(Polystyrene,PS)微塑料对旋链角毛藻(培养16 d)以及聚乙烯(Polyethylene,PE)微塑料对中肋骨条藻(培养96 h)的生长和二甲基硫(Dimethylsulfide,DMS)产生的影响。结果表明,与0、0.05、0.5和5 mg·L^(-1) PS微塑料相比,50 mg·L^(-1)的80 nm PS微塑料显著抑制旋链角毛藻生长,而单细胞DMS浓度以及10~16 d的单细胞叶绿素a、单细胞叶绿素c和单细胞类胡萝卜素浓度却显著升高。80 nm PS荧光微塑料对旋链角毛藻暴露的观察结果显示,荧光微塑料附着在旋链角毛藻的角毛上。50 mg·L^(-1)的80 nm PS微塑料对旋链角毛藻2~16 d的生长抑制率为41.4%~93.2%。50和100 mg·L^(-1) PE微塑料暴露48 h时,生长抑制率达到最大值,分别为36.1%和40.0%。0~100 mg·L^(-1)的20μm PE微塑料暴露96 h对中肋骨条藻单细胞叶绿素a、单细胞叶绿素c、单细胞类胡萝卜素、单细胞DMS和二甲基巯基丙酸内盐(Dimethylsulphoniopropionate,DMSP)浓度两两之间均无显著性差异。因此,80 nm PS微塑料对旋链角毛藻的影响比20μm PE微塑料对中肋骨条藻的影响大。研究结果可以为进一步探究微塑料对海洋微藻的生态毒理学以及生源硫化物释放的影响提供参考依据。

黄、东海春季海水胞外酶活性水平分布特征研究

海水胞外酶活性可以指示有机物的分布特征以及微生物的营养状况。我们测定了2017年3月25日至4月15日黄海和东海44个大面站以及2018年4月28日至29日胶州湾湾口附近海域10个站位表层海水中的8种胞外酶活性并研究了其分布特征。2017年春季黄、东海表层海水中碱性磷酸酶和脂肪酶活性较高,高值区出现在苏北沿岸和南黄海中部,碱性磷酸酶与磷酸盐浓度之间呈正相关。其余6种酶(肽酶、几丁质酶、纤维素酶、α-D-葡萄糖苷酶、β-D-半乳糖苷酶、木糖苷酶)活性高值区出现在长江口以东的外海,东海的β-D-半乳糖苷酶、木糖苷酶平均酶活性显著高于黄海。8种酶活性平均值排列顺序由大到小为:碱性磷酸酶、脂肪酶、肽酶、几丁质酶、α-D-葡萄糖苷酶、β-D-半乳糖苷酶、纤维素酶、木糖苷酶,其中α-D-葡萄糖苷酶和β-D-半乳糖苷酶的活性基本一致。2018年春季胶州湾附近海域海水中碱性磷酸酶、脂肪酶、木糖苷酶活性分布为近岸高于远岸,几丁质酶活性为近岸低于远岸。8种酶活性平均值排列顺序由大到小为:碱性磷酸酶、脂肪酶、肽酶、木糖苷酶、α-D-葡萄糖苷酶、β-D-半乳糖苷酶、几丁质酶、纤维素酶,其中几丁质酶和纤维素酶的活性基本一致。黄海的碱性磷酸酶和脂肪酶平均酶活性均显著高于东海和胶州湾附近海域。糖类水解酶(几丁质酶、纤维素酶、α-D-葡萄糖苷酶、β-D-半乳糖苷酶、木糖苷酶)平均酶活性在黄海最低。本文的结果对于理解中国近海海水有机碳的分布、浮游植物及异养细菌对有机碳的降解具有重要意义。

冻藏的温度波动对三文鱼化学指标值及持水力的影响

在短期冻藏时,为了提高三文鱼的冻藏温度,减少冻藏能耗与运行成本。研究了冻藏期间(6个月)在−18℃冻藏环境下,温度波动幅度对三文鱼的挥发性盐基氮(TVB-N)值、硫代巴比妥酸(TBARS)值、K值等化学指标值与持水力的影响,并与(−50±0.1)℃冻藏品质对比。结果表明:三文鱼的TVB-N、TBARS、K值、持水力的冻藏初始值分别为6.21 mg N/100 g、0.11 mg MDA/kg、9.87%、86.31%,在(−18±0.5)、(−18±1)、(−18±2)℃环境下冻藏6个月后,TVB-N值分别增大到19.06、23.25和25.91 mg N/100 g,TBARS值分别增大到1.65、1.89、1.96 mg MDA/kg,K值分别增大至43.28%、55.38%、63.54%,持水力分别下降至57.16%、53.49%、51.67%,即温度波动越大,化学指标增加越显著,持水力下降越明显;通过减小冻藏期间温度波动幅度至±0.5℃,可以在3个月内有效提高三文鱼的冻藏温度至−18℃,并保证三文鱼的TVB-N值、TBARS值、K值及持水力与在(−50±0.1)℃冻藏6个月时相当,从而节约成本并降低能耗。以冻藏时间和温度波动幅度为自变量,以持水力为因变量,建立了多元线性回归拟合方程,为建立货架期预测提供依据。

The effects of enriched C0_(2) and enhanced UV-B radiation on ultrastructure of Dunaliella salina, singly and in combination

The effects of ambient CO2/ambient UV-B, enriched CO2/ambient UV-B, ambient CO2/enhanced UV-B, and enriched CO2/enhanced UV-B on the ultrastructure of Dunaliella salina were investigated. （1） The ultrastructure of D..salina cell in the control experiment showed that the arrangement of thylakoid lamellae was regular, and there were many large starch grains among the thylakoid lamellae. A prominent well-developed pyrenoid was found in the middle of the chloroplast. Nucleus envelope and nucleolus were clearly observed. The Golgi apparatus accompanied by numerous vesicles with a compact arrangement of cisternae and the peripheral tips of the cisternae were swollen to a size comparable to that of some of the associated vesicles. （2） The ultrastructure of D. salina cell in enriched CO2 showed that the arrangement of thylakoid was regular and the lamellae were vivid. Developed pyrenoids were found in the low-CO2-grown cells, but not in the high-CO2-grown cells. The mitochondria cristae were vivid. The arrangement of Golgi apparatus was compact. （3） The ultrastructure of D. salina cell in enhanced UV-B showed that the thylakoid was dissolved and the cells had a less developed pyrenoid or no detectable pyrenoid. Part of the nucleus envelope was dissolved. The number ofmitochondria was increased and some mitochondria cristae were disintegrated. The starch grains were broken apart into many small starch grains. The Golgi apparatus with a loose arrangement ofcistemae and the peripheral tips of the Golgi cistemae were not especially swollen, with several large associated vesicles. （4） The ultrastructure of D. salina cell in the enriched CO2/enhanced UV-B showed that part of the thylakoid and nucleus envelopes of some cells were dissolved. The pyrenoid was larger than that of the enhanced UV-B. There were many mitochondria between stroma and chloroplast membrane, but mitochondria cristae were partly dissolved. Many small starch grains were accumulated in cells. The starch sheath was broken into several discontinuous starch grains with different sizes. The arrangement of Golgi apparatus was loose. Above all, although the enriched CO2 can alleviate the damage induced by the UV-B radiation, the effects of experimental UV-B radiation were larger than the effects of actual UV-B radiation, the damage induced by the UV-B radiation was so severe, therefore, CO2 enrichment could not restore the ultrastructure to the control level.

海洋酸化对碳、氮和硫循环的影响

工业革命以来,大气CO_2浓度呈现快速增加的趋势,随之而来的问题是海洋酸化的程度越来越明显。与工业革命前相比,目前海洋表层海水pH降低了0.1个单位,到本世纪末估计会降低0.4个pH单位。本文综述了海洋酸化对碳、氮和硫循环的影响,包括碳循环中的溶解度泵、碳酸盐泵、软组织泵和微型生物碳泵,海洋酸化对氮循环中氮的固定、硝化作用、反硝化作用、N_2O的产生的影响,海洋酸化与硫循环中二甲基硫(DMS)的产生及其与食物网结构之间的关系。海洋酸化无论是以直接或间接方式均会在一定程度上对碳、氮和硫的生物地球化学循环产生影响,最终改变海洋系统的结构与功能。在自然界中,海洋酸化不是一个独立的过程,而是与其他物理、化学、生物变化因素相偶联共同作用于碳、氮和硫的生物地球化学循环。