Accumulation and depuration of paralytic shellfish poisoning toxins in the oyster Ostrea rivularis Gould – Chitosan facilitates the toxin depuration

The accumulation and depuration of paralytic shellfish poisoning (PSP) toxins in the oyster of Ostrea rivularis Gould (ORG) were investigated in this study. Firstly, PSP toxin-accumulating in ORG were produced by feeding with the toxic algae Alexandrium minutum cultured in the laboratory. The feeding amounts were designed for three concentrations of 4.0 × 10³, 8.0 × 10³, and 1.2 × 10⁴ cells/mL. After 20 day's feeding, the toxicity in the ORG became high levels of 28.86, 31.17, and 38.98 MU/g, respectively. And the toxin-accumulating ORG fed only for 2 d with 8.0 × 10³ cells/mL which toxicity was 11.93 MU/g were selected for depuration experiment. In the depuration process, the ORG were fed with nontoxic microalgae (MA) of Chlorella spp., chitosan (CTS), and MA + CTS. Feeding with 8.0 × 10³ cells/mL MA and 0.05 g/L CTS resulted in the largest PSP toxin reduction in the ORG. After 7 d of depuration feeding, the toxicity of the PSP toxin decreased from 11.93 to 3.47, 1.40, and 0.50 MU/g, as determined by the mouse bioassay (MBA). High performance liquid chromatography – fluorescence detection systems (HPLC–FLD) was applied in the qualitative and quantitative detection of PSP toxins in the ORG during accumulation and depuration. Chromatograms of samples not containing oxidation and acidulating reagents in the mobile phase were used to identify unknown peaks. The HPLC results showed that PSP toxicity before depuration was 9.07 MU/g. After 7 d of depuration, feeding by CTS and MA + CTS was reduced to 1.41 and 0.12 MU/g, respectively. The laboratory experiments showed that CTS had a remarkable effect on PSP removal in ORG. The toxicity and toxin profiles of ORG were investigated by MBA combined with post-column HPLC–FLD. The results of both methods supplemented each other, thereby elucidating the accumulation, depuration, and transformation of PSP toxins from the toxic algae in ORG.     

邻苯二甲醛的简捷合成方法

以邻苯二甲醇为原料,利用浓硝酸的氧化作用,在冰醋酸/水体系中合成邻苯二甲醛。较佳合成条件为:反应时间0．5h,反应温度80℃,邻苯二甲醇与浓硝酸的用量比(摩尔比)1:2．3,邻苯二甲醛收率74．6%,纯度99．2%。     

合成温度对La0.85K0.15MnO3纳米颗粒磁性能的影响

采用非晶态配合物前躯体法在比较低的烧结温度合成了钙钛矿结构氧化物La0.85K0.15MnO3纳米颗粒,系统的研究了烧结温度对La0.85K0.15MnO3纳米颗粒磁性能的影响,用PPMS测量样品的居里温度和磁性能,结果表明烧结温度范围在600℃～1000℃之间,居里温度TC为274.5 K,和烧结温度没有明显关系,在H=2T时,烧结温度分别为600℃,800℃,1000℃,对应的磁熵变△SM分别是2.02 J/(kg.K),3.06 J/(kg.K),3.56 J/(kg.K),当烧结温度升高到1200°C时,居里温度TC为242.9K,通过控制烧结温度来调节La0.85K0.15MnO3纳米颗粒的磁性能。     

Anthocyanins from banana bracts (Musa X paradisiaca) as potential food colorants

Banana (Musa X paradisiaca) bracts, abundant edible residues of banana production, were investigated as a potential source of natural colorant. Anthocyanins were extracted with acidified methanol, purified using C-18 resin, and characterized by UV-visible spectroscopy, physicochemical reactions, HPLC, and electrospray mass spectrometry. Monomeric anthocyanin content was 32.3 mg/100 g bracts on a cyanidin-3-rutinoside basis. Color characteristics (Hunter CIE L*hc) of a solution (absorbance of 0.3, 520 nm, pH 3.5), were L*=86.8, h=44.2 and c=12.7. Cyanidin-3-rutinoside represented ∼80% of the total pigment. Other anthocyanins were 3-rutinoside derivatives of delphinidin, pelargonidin, peonidin and malvidin. One acylated anthocyanin (∼2% of the pigment) was found but not identified. Acid hydrolysis of anthocyanins revealed the concomitant presence of six more common anthocyanidins (delphinidin, cyanidin, petunidin, pelargonidin, peonidin and malvidin) suggesting that, besides being a good pigment source, it could also be a useful tool for anthocyanin identification.     

KBS-aided design of tube bending processes

Cold bending of metal tube products is a metal forming process widely used in industry. With today's demand on high quality tube-dependent products, bending of tubing parts has become a precision metalworking operation that requires sophisticated knowledge and experience. In this work, a knowledge-based system (KBS) has been developed to aid the design of tube bending processes, including bending methods selection, tool/die design, and process parameters setup. The object-oriented programming techniques and the goal-driven search mechanism, featured by an interactive graphic user interface, have been applied in development of the proposed KBS. The system developed has shown effective in tube parts production with significantly reduced number of potential defects and failures, such as inaccuracy of bend angles or linear dimensions, wall thinning, flattening, wrinkling, twisting, dents or cracks, etc.     

选区激光熔化快速成型过程温度场数值模拟

为了优化铜磷合金粉末选区激光熔化快速成型的工艺参数,采用有限元分析软件ANSYS对其温度场进行了模拟,经理论分析和实验验证,获得了其温度场分布的数据.对材料未知温度范围内的热特性参数用插值法近似获得,采用不等网格剖分方式,用热焓去处理相变潜热问题.结果表明,其温度场的等温线分布为椭圆形,用模拟遴选的工艺参数(在铺粉厚度为0.22mm时,选用激光功率为100W、扫描速度为0.25m/s和激光束半径为0.1mm)能实现选区激光熔化快速成型.这一结果对其它粉末材料的选区激光熔化快速成型也是有帮助的.     

不同海洋生物源肝素的理化性质及抗凝血活性

为研究和开发海洋生物源肝素,本实验采用酶解醇沉法从9?种海洋生物中提取出粗肝素,采用紫外光谱法、傅里叶变换红外光谱法和高效液相色谱法对其理化性质和结构特性进行分析,并通过体外凝血实验分析其抗凝血活性。结果表明：9?种肝素粗品的肝素含量从高到低依次为凡纳滨对虾（Penaeus vannaei）虾头339.92?μg/mg、海蚌（Mactra antiquata）239.15?μg/mg、泥蚶（Tegillarca granosa）234.85?μg/mg、蛏子（Sinonovacula constricta）218.29?μg/mg、文蛤（Meretrix meretrix L.）214.78?μg/mg、钝缀锦蛤（Tapes dorsatus）212.194?μg/mg、海湾扇贝（Argopecten irradias）68.52?μg/mg、象拔蚌（Panopea abrupta）61.48?μg/mg、菲律宾蛤蜊（Ruditapes philippinarum）24.29?μg/mg,其均为吡喃糖,且都含有肝素的主要单糖：氨基葡萄糖、艾杜糖醛酸和葡萄糖醛酸。体外凝血实验结果表明,9?种粗肝素效价从高到低依次为海蚌67.1?U/mg、凡纳滨对虾虾头59.3?U/mg、文蛤44.0?U/mg、钝缀锦蛤39.2?U/mg、蛏子35.0?U/mg、泥蚶29.6?U/mg、象拔蚌27.2?U/mg、海湾扇贝27.1?U/mg、菲律宾蛤蜊24.1?U/mg,它们具有不同强度的抗凝血活性,且发挥抗凝血作用的途径不同。实验结果可为海洋源肝素的开发提供参考。     

腌鱼中耐盐酵母菌的分离鉴定及其生理生化特性

为了获得生产性能优良的菌株,采用PDA固体培养基平板涂布法从腌鱼中分离、纯化酵母菌,研究优势耐盐酵母菌株的生长温度、耐酸能力、耐亚硝酸盐能力等生理生化特性及ITS rDNA分子生物学鉴定。结果表明,15种不同种类腌制海鱼中共分离出436株酵母菌,经纯化后获得9株不同种属的酵母菌,通过不同NaCl含量的YPD液体培养基对9株酵母菌进行筛选,最终筛选出7#季也蒙毕赤酵母和9#奥默柯达酵母两株耐盐性较好的优势耐盐酵母菌菌株,耐盐能力分别达到9%和12%,最适生长温度均在28~32 ℃之间,最适pH在5~6之间,耐亚硝酸盐含量可达100 mg/kg。腌鱼中获得优势菌株具有良好的生长性能,可为腌鱼制品发酵剂的开发奠定基础。     

2,4-二硝基氟苯柱前衍生HPLC-UV法测定海稻米中的γ-氨基丁酸含量

为建立海水稻活性成分γ-氨基丁酸(GABA)的高效液相色谱-紫外检测(HPLC-UV)方法。以2,4-二硝基氟苯(FDNB)为衍生化试剂,采用高效液相色谱法测定了精白米、玉米、海稻米、发芽海稻米24 h、发芽海稻米48 h、发芽海稻米72 h的γ-氨基丁酸(GABA)含量,研究了FDNB的投量,醋酸铵溶液-乙腈作为流动相以及样品的pH对GABA衍生物保留时间的影响,并考察了该方法的精密度、重复性和稳定性及加标回收率。结果表明,发芽海稻米24 h中GABA的含量最高,为34.35 μg/mg,玉米、未发芽海稻米、发芽海稻米48 h、发芽海稻米72 h中GABA的含量分别为为3.74、3.63、17.03、9.54 μg/mg,而精白米中GABA含量几乎为零;FDNB投量为0.3 mL时,可确保反应完全;用0.5%醋酸铵水溶液:乙腈(V:V)=85:15作流动相克服了泵压不稳定的现象;用硼酸盐缓冲液对衍生化后的样品进行稀释(1、5、10、15、20、40倍)后,样品的pH在9.0左右,GABA衍生物的保留时间几乎不漂移,在15.8 min左右;该方法精密度高、重复性和稳定性好,相对标准偏差值分别是0.08%、0.66%和0.60%;样品在24 h内稳定,回收率在99.29%~101.35%。结论 本实验方法简便、结果可靠,可用于高含量GABA功能性食品的质量控制。     

罐头杀菌值简单计算方法的探讨

本论文以平板型罐头食品为研究对象,探讨热杀菌过程中心部分杀菌值的简单计算方法。通常推算杀菌值就需要对温度的数值进行积分,或利用计算机软件来进行计算分析,比较困难和复杂。本研究首先利用数学解析计算出中心温度,再利用积分方法计算出杀菌值后,建立中心温度和杀菌值的函数关系式。通过函数关系式来推算杀菌值,比较简单易行。表达式以杀菌温度和Z值作为参数,推导出不同杀菌温度和Z值时杀菌值的表达式关系,不通过积分就可以通过简单的函数式来表达。将通过函数表达式求得的杀菌值和通过积分求得的杀菌值进行比较的结果表明误差在1 min以内,实现了杀菌值的简便计算。此方法便简单易行。有利于杀菌工艺的优化,对罐头食品的品质管理具有重要意义。