山药多酚氧化酶特性研究

以邻苯二酚为底物,采用分光光度法测定波长410nm处山药多酚氧化酶的活性,研究了pH、温度、底物浓度和抑制剂对山药多酚氧化酶活性的影响。结果表明,山药多酚氧化酶的最适反应pH=6·0,最适反应温度为35℃;化学抑制剂柠檬酸、苹果酸、L-抗坏血酸对多酚氧化酶均有抑制作用,L-抗坏血酸抑制作用最为明显,L-抗坏血酸抑制机理为反竞争性抑制。     

烫漂条件对冻干口蘑褐变度的影响

本试验选用新鲜口蘑切片作为试验样品,以口蘑片的褐变度为指标,考察了冻干口蘑片烫漂工序中影响产品色泽的主要因素,通过正交试验确定了冻干口蘑片的最适宜烫漂条件。     

有机酸及相关盐类在果蔬护色、防褐变中的应用研究

考察了不同浓度的曲酸、抗坏血酸、乳酸及ZnC l2、CaC l2、乳酸锌、乳酸钙处理苹果和梨的防褐变时间。结果表明,曲酸的护色效果最好。当曲酸浓度>0.1%时,防褐变效果很好,24 h时只有轻微褐变;当乳酸钙浓度>1.0%,抗坏血酸浓度>0.25%,ZnC l2浓度>0.75%,CaC l2浓度>1.0%时,防褐变效果均较好。     

rCHO细胞在葡萄糖限制流加培养过程中的生长与代谢特性

以调控rCHO细胞的葡萄糖代谢为主要研究目标,通过在2L生物反应器中进行的批培养和葡萄糖限制恒速流加培养的方法,考察了在培养过程中葡萄糖浓度对rCHO细胞生长、葡萄糖和谷氨酰胺消耗,以及副产物乳酸、氨和丙氨酸生成的影响.结果表明:葡萄糖限制的流加培养过程中,活细胞密度XV达到2.35(106cells(mL(1,较批培养提高一倍;而乳酸生成大幅减少.在葡萄糖限制培养阶段,qLac和YLac/Gluc持续降低至零,而qo2/qGluc由0.7 mmol(mmol(1上升至4.3mmol(mmol(1,说明更多葡萄糖进入高效释能代谢途径.同时谷氨酰胺的消耗增加,YAmm/Gln增大,YAla/Gln下降,证明谷氨酰胺的能量利用率也有所提高.     

变参数控制在调节阀流量特性畸变系统中的工程应用

调节阀工作流量特性随工艺而变化,难以与被控对象形成广义线性系统;高阀阻比使调节阀消耗大量能量,而低阀阻比又使得流量特性畸变非常严重从而影响控制性能.提出一种改进的变参数控制,使比例增益随设定值与测量值变化,积分时间随设定值与偏差变化,使得调节阀工作特性非线性,特别是阀阻比很低流量特性畸变严重的情况下,对流量也能较好地控制,基本消除了超调,达到了实现低阀阻比节能与提高控制性能的目的.通过将算法在DCS系统上组态与编程加以实现,完成实际装置的流量控制,证明了该控制方案的可行性.     

过程装备与控制工程专业卓越工程师培养探索

卓越工程师培养计划是由中国工程院发起,联合教育部等众多部委实施的人才培养模式,是面向未来国民经济发展对人才需求的趋势而推出的新举措,也是我国高等工程教育发展的一种新尝试。依据过程装备与控制工程专业特点,我院研究制订了该专业卓越工程师培养方案,并建立了过程装备制造和检测检验两个实践基地,拓展了实践性教学的内涵,创新了实施的载体,培养模式上采取灵活而可操作的方法,积累了一些经验。     

化工过程强非线性系统的变模型自适应预测控制

提出一种变模型自适应预测控制算法 ;基于非线性状态空间模型 ,通过每步在当前工作点 (非平衡点 )线性化获得线性化子模型 ,以此进行状态反馈预测控制 ,线性化子模型随工作点变化 ,且不限于平衡点。通过pH值控制的对比仿真实验 ,证明其对强非线性过程的控制效果优于传统的多模型预测控制。最后分析讨论了该控制算法存在的几个重要问题 ,并指出与之相关的未来研究方向     

青年教师导师制培养过程中的点滴体会

本文综述了青年教师导师制的发展基本过程和现状,针对地方院校青年教师的特点和培养现状,总结了青年教师培养过程中点滴体会。     

培养过程装备与控制工程专业卓越工程师的思考

本文简要介绍了卓越工程师的相关背景,探讨了过程装备与控制工程专业应用型工程师、设计型工程师、研究型工程师各自的培养模式和应具备的知识结构;从教学平台、师资平台、实验平台、实践平台、社会平台等方面论述了培养过程装备与控制工程专业卓越工程师的培养平台基础;从七个方面对过程装备与控制工程专业卓越工程师的培养措施进行了思考,以期为我国过控专业工程人才教育提供有益的指导。     

新型离散自适应变结构算法在步进梁控制中的应用

采用电液伺服控制系统对步进梁的上升驱动液压缸的位移进行精确控制,采用机理法建立系统的离散线性数学模型,综合考虑到步进梁输送钢坯的过程表现出大惯性负载、非线性和变结构的特点,在常规离散趋近律分析的基础上提出了一种新的离散自适应变结构算法。该算法通过双曲正切函数结合自变量的增益因子来实现对切换函数的粗调、细调,并且根据自适应增益的递推规律讨论了系统状态在各个阶段的运动特点,给出了系统的鲁棒稳定性证明。从理论与MATLAB仿真的角度说明了新的算法在变结构消抖和改善系统动态性能方面的优势。在仿真中与指数趋近律和常规自适应趋近律进行了对比,证明了该算法对于要求速度无振荡、位移无超调的步进梁运动控制系统是一种有效的控制策略。     

循环超声强化提取肉苁蓉中多糖和甜菜碱

研究了循环超声强化提取肉苁蓉中多糖和甜菜碱的工艺条件. 实验结果表明，将肉苁蓉粉碎至40目，液固比为60 ml/g时提取较为适宜. 循环超声提取多糖和甜菜碱的较优工艺条件是：提取温度40℃，超声功率1000 W，提取时间10 min，在此条件下，多糖的提取量为46.9 mg/g，甜菜碱的提取量为136.5 mg/g，分别相当于沸水回流7 h时提取量的107.3%和103.8%.     

微波消解-ICP-OES法测定肉苁蓉中矿质元素

经HNO3/H2O2湿法微波消解制样,利用全谱直读电感耦合等离子原子发射光谱法(ICP-OES),测定了青藏高原地区产肉苁蓉中的矿质元素。结果显示,肉苁蓉中含有Na、K、Ca、P、S、Mg、Si、Al、Fe、Li、Ti、Sr、Mn、Zn、Cu、Ba、B、Cr等18种矿质元素。测定结果相对标准偏差RSD值在0.85%～12.6%,其中14种在5%以内。常量元素中,Na、K、Ca、P、S、Mg的质量分数分别为4.03%,1.23%,0.31%,0.32%,0.29%,0.17%;微量元素中,Fe、Mn、Zn、Cu、Cr含量分别为788.3,16.87,15.29,7.18,1.24 mg/kg。     

肉苁蓉愈伤组织的超低温保藏方法

提出了一个优化的简单的超低温保藏方法,成功地运用于肉苁蓉愈伤组织的低温保藏. 为了获得最佳的实验结果,肉苁蓉愈伤组织首先在添加了6%二甲亚砜的B5培养基中进行预培养,然后用玻璃化保护剂在25℃处理20 min,最后投入液氮中进行冷冻. 玻璃化保护剂的成分为30%(j)甘油+15%(j)乙二醇+10%(j)二甲亚砜+0.5 mol/L蔗糖. 冷冻后的愈伤组织在30℃的水浴中迅速解冻,接着用25℃的1.0 mol/L蔗糖溶液洗净愈伤组织上附着的玻璃化保护剂,最后在B5培养基上对愈伤组织进行恢复性培养. 经过上述冻存处理的肉苁蓉愈伤组织存活率可达86％. 恢复培养5个月后,愈伤组织中苯乙醇糖甙类化合物的含量和产量分别达到冷冻前的97%和95%.     

人工栽培肉苁蓉保肝和抗氧化活性研究

采用清除二苯代苦味酰基(DPPH)自由基、清除[2,2′-连氨-(3-乙基苯并噻唑啉-6-磺酸)二氨盐](ABTS)自由基和铁离子还原/抗氧化能力(FRAP)测定法评价栽培肉苁蓉不同溶剂提取物体外抗氧化能力;腹腔注射四氯化碳复制小鼠急性肝损伤模型,测定血清谷丙转氨酶(ALT)、谷草转氨酶(AST)活性、肝脏指数和肝组织匀浆中丙二醛(MDA)含量及超氧化物歧化酶(SOD)活力值评价栽培肉苁蓉乙醇提取物的保肝作用。栽培肉苁蓉各提取物均显示较好的清除DPPH自由基、ABTS自由基及还原Fe3+-三吡啶三哑嗪(TPTZ)的能力,其中乙醇提取物具有最好的抗氧化活性(3种方法的RACT50值为3 534.32、2 726.39、2 621.68μmol/g),与阳性对照药丁基羟基茴香醚(BHA)相差不大(RACT50值为4 242.31、5 457.65、6 633.04μmol/g),大于丁基羟基甲苯(BHT)(RACT50值为724.59、1 322.27、1 581.68μmol/g);且肝损伤实验显示,乙醇提取物能显著降低小鼠血清中ALT、AST活性以及肝匀浆MDA含量,并能显著提高小鼠肝脏中的SOD值。结果表明,肉苁蓉对四氯化碳致小鼠急性肝损伤具有显著的保护作用,其机制可能与其抗氧化作用有关。     

Molecular modeling of peroxidase and polyphenol oxidase: substrate specificity and active site comparison

Peroxidases (POD) and polyphenol oxidase (PPO) are enzymes that are well known to be involved in the enzymatic browning reaction of fruits and vegetables with different catalytic mechanisms. Both enzymes have some common substrates, but each also has its specific substrates. In our computational study, the amino acid sequence of grape peroxidase (ABX) was used for the construction of models employing homology modeling method based on the X-ray structure of cytosolic ascorbate peroxidase from pea (PDB ID:1APX), whereas the model of grape polyphenol oxidase was obtained directly from the available X-ray structure (PDB ID:2P3X). Molecular docking of common substrates of these two enzymes was subsequently studied. It was found that epicatechin and catechin exhibited high affinity with both enzymes, even though POD and PPO have different binding pockets regarding the size and the key amino acids involved in binding. Predicted binding modes of substrates with both enzymes were also compared. The calculated docking interaction energy of trihydroxybenzoic acid related compounds shows high affinity, suggesting specificity and potential use as common inhibitor to grape ascorbate peroxidase and polyphenol oxidase.     

Browning behavior of button mushrooms during microwave freeze-drying

In order to achieve faster drying along with high product quality, microwave freeze-drying (MFD) was applied to dry button mushrooms. Although MFD can lead to similar product quality compared with freeze-drying (FD), the color deterioration of MFD mushroom is higher than FD ones. Therefore, two drying methods were used to investigate the browning behaviors of button mushrooms during MFD in terms of parameters including polyphenol oxidase activity, total phenolic content, moisture content, reducing sugar content, and vitamin C content. It was found that both whiteness and browning degree can be used to describe the browning kinetics of button mushrooms during the MFD process. Both nonenzymatic browning and enzymatic browning took place during MFD of button mushrooms, but the effect of enzymatic browning was more significant, which should be controlled during MFD. In order to avoid enzymatic browning during MFD of button mushrooms, a relatively low microwave power at initial stage of MFD should be adopted. Meanwhile, a low microwave power also should be used at the end stage of MFD so as to reduce nonenzymatic browning.     

水痘减毒活疫苗Oka株的传代稳定性

目的观察水痘减毒活疫苗Oka株(V-Oka)的传代稳定性。方法将V-Oka病毒在人二倍体细胞MRC-5上连续传代至50代,观察病毒的培养特性。选择32、34、38、42、46、50代病毒进行病毒滴度测定和鉴别试验,提取病毒DNA,对V-Oka的主要基因(ORF31、ORF62、ORF68、R区)进行PCR扩增和测序,并对序列进行分析。结果 V-Oka连续传代至50代,其培养特性、细胞病变一致,病毒滴度为5.0～5.6LgPFU/ml。与GenBank中登录的V-Oka序列比较,32～50代的V-OkaORF31、ORF62、ORF68、R区序列稳定,并趋于减毒型。结论 V-Oka传代至50代,生物学和分子遗传学特性稳定。     

抗坏血酸对烟草中多酚类物质稳定性影响的研究

为了找到有效抑制烟草中多酚类物质氧化分解的方法,向多酚提取液中添加抗坏血酸。放置一周后发现,与不加抗坏血酸的多酚提取液相比,加入抗坏血酸的下降趋势缓和,多酚含量稳定,说明抗坏血酸能有效抑制多酚类物质的氧化分解。该研究为控制多酚氧化酶(PPO)引起的烟草的颜色变化提供了一个有效途径。多酚类化合物的含量测定采用高效液相色谱法,重现性好,回收率为95.8%~102.8%,结果可靠。     

Influence of Drying Conditions on the Hazelnut Quality. III. Browning

The influence of drying conditions on browning in hazelnut (Corylus avellana L.) has been studied by means of color measurement. Samples of unshelled and shelled hazelnuts were dried under six air temperatures (30. 40, 50, 60, 70 and 80°C). The drying experiments were done with forced air circulation, and two varieties of hazelnut were investigated, Negret and Pauetet. CiELab system was used to evaluate changes in total color (δE^*), lightness (L^*), chroma (C^*) and hue angle (H^*) on dried hazelnuts. Browning of hazelnut was observed to occur a1 all temperatures studied. The rate of pigment formation was determined from the δE' values with zero-order kinetic model, and temperature dependence was described by the Arrhenius equation with an activation energy (E_a) varying from 28 to 39 kJlmol. Negret variety showed the highest rate of browning.     

Influence of Drying Conditions on the Hazelnut Quality. III. Browning

ABSTRACT

The influence of drying conditions on browning in hazelnut (Corylus avellana L.) has been studied by means of color measurement. Samples of unshelled and shelled hazelnuts were dried under six air temperatures (30. 40, 50, 60, 70 and 80°C). The drying experiments were done with forced air circulation, and two varieties of hazelnut were investigated, Negret and Pauetet. CiELab system was used to evaluate changes in total color (δE^?), lightness (L^?), chroma (C^?) and hue angle (H^?) on dried hazelnuts. Browning of hazelnut was observed to occur a1 all temperatures studied. The rate of pigment formation was determined from the δE' values with zero-order kinetic model, and temperature dependence was described by the Arrhenius equation with an activation energy (E_a) varying from 28 to 39 kJlmol. Negret variety showed the highest rate of browning.