传统发酵豆酱中产蛋白酶菌株的筛选

该研究从东三省各地采集家庭自制豆酱254份,通过分离培养,获得纯培养真菌菌株389株。采用脱脂牛奶平板初筛获得具有蛋白酶活性的菌株31株,其中曲霉属真菌12株、青霉5株、毛霉4株、镰孢菌3株、帚霉1株、芽枝孢3株、犁头霉1株、红曲2株。通过发酵复筛提取其粗酶液,用福林酚法测定粗酶液的蛋白酶活性,筛选出了两株具有较高蛋白酶活性的米曲霉。     

刺五加活性成分的研究进展

本文对刺五加中苷类、黄酮、多糖等活性成分及功效进行了简述,同时对刺五加主要的活性成分在不同的生长环境、收获时间、取样部位以及提取方法等方面进行对比,阐述这些方面对刺五加活性成分含量的影响,为刺五加未来开发与利用提供了理论依据。     

蒙氏肠球菌Sna的抗氧化及降胆固醇特性

目的从雉鸡嗉囊分离得到一株生长良好的乳酸菌Sna,测试其抗氧化活性和降胆固醇的能力和模式。方法菌株鉴定通过菌落、菌体形态、生化试验和16S rRNA序列分析。抗氧化和降胆固醇作用通过体外实验完成。结果乳酸菌Sna确认为蒙氏肠球菌。当菌体浓度为10~9 CFU/mL时,菌株Sna对羟自由基、DPPH自由基和超氧阴离子自由基的清除率分别为78.8%、34.9%和43.3%。单位细胞干重去除胆固醇量与菌体生长有一定的相关性,在培养36 h单位细胞干重能清除最大的胆固醇量5.14μg/mg。对比试验显示生长的细胞单位干重去除的胆固醇量达到4.96μg/mg,但热杀死的和休眠的细胞去除胆固醇量分别为4.39μg/mg和4.23μg/mg。结论菌株Sna具有抗氧化作用和胆固醇的清除能力;菌株Sna去除胆固醇可能的机制是菌体对胆固醇的吸附及菌体在生长过程中对胆固醇的吸收利用。该菌株具有添加到食品中来抵抗氧化作用和降低血液胆固醇的潜能。     

Controllable chemical reaction synthesis of Tb(OH)3 nanorods and their photoluminescence property

A novel and simple chemical reaction method has been developed to synthesize the Tb(OH)₃ nanorods with diameters of 20–30 nm and lengths of about 300 nm at 90 °C using cyclohexylamine as the alkaline source. The formation mechanism for the synthesis of the Tb(OH)₃ nanostructures with different morphologies has been primarily discussed.     

Synthesis,crystal structure,and thermal stability of a novel 3D cadmium carboxyphosphonate containing left-hand helical chains Cd3Cl2[(O3PCH2–N(H)C5H9–COO)2(H2O)2] · 4H2O

A novel 3D cadmium carboxyphosphonate containing left-hand helical chains, Cd₃Cl₂[(O₃PCH₂–N(H)C₅H₉–COO)₂(H₂O)₂] · 4H₂O 1 has been synthesized by hydrothermal reaction at 120 °C and structurally characterized by single-crystal X-ray diffraction as well as with infrared spectroscopy, elemental analysis and thermogravimetric analysis. In compound 1, the hexanuclear clusters based on Cd(1)O₄Cl₂, Cd(2)O₄Cl₂, Cd(3)O₆ and CPO₃ polyhedra are interconnected through carboxyphosphonate ligands to form a 3D open-framework structure with channel system. The result of connections in this manner is the formation of 20- and 30-atom rings that are parallel to one another and run in the a-axis direction. It is interesting that a type of left-hand helical chain is formed by HL^2? ligands bridging Cd₃ ions running along the b-axis.     

水产品优势腐败菌及其群体感应系统研究进展

细菌群体感应是细菌利用胞外信号分子感知外界环境变化,并启动相关基因表达来适应环境变化的一种调控系统。群体感应系统参与调控微生物的多种生活习性以及各种生理过程,已经成为生命科学相关领域的热门研究课题之一。本文主要对群体感应及信号分子类型作了阐述,并概述了水产品贮藏过程中的优势腐败菌及其群体感应对水产品腐败的影响,旨在为水产品贮藏保鲜基础理论研究提供一定借鉴。     

贮前氯化钙处理对李果实冷害及生理生化的影响

为探索减轻李果实冷害的新途径,以串红李子为试材,研究了不同浓度的氯化钙处理对低温下贮藏的李果实冷害及生理生化的影响。结果表明,对照果在冷藏12d后,a＊值、b＊值、相对电导率、可溶性固形物含量、呼吸强度都呈现上升趋势,果实硬度、乙烯释放量快速下降,冷害指数逐渐增加,说明此时冷害已经发生。而经氯化钙处理的果实,硬度、外观、冷害指数明显低于对照,呼吸强度、乙烯释放量受到一定的抑制,L＊值降低、a＊值增大,贮藏初期的着色指数高于对照,但只有2%氯化钙处理的李果实可溶性固形物含量、相对电导率前期较低后期高于其它果,内部冷害指数明显低于对照,说明2%氯化钙处理从外观上明显地抑制了李果实冷害的发生,而综合内外两种冷害指数来看,只有2%氯化钙处理抑制冷害的效果较好,保持了李果实较好的贮藏品质。     

箱式气调贮藏对采后蓝莓生理生化变化的影响

以伯克利品种蓝莓为试材,研究了在1℃的5%O2＋10%CO2;5%O2＋20%CO2和5%O2＋30%CO2的箱式气调贮藏条件下的生理生化变化情况。每20d测定一次酶促防御系统的酶活性、抗病性相关酶活性和非酶促防御系统的抗氧化物质的含量,并测定呼吸速率、木质素含量、果实硬度和腐烂率。实验结果表明：与对照相比,3种CO2浓度的箱式气调贮藏条件均可启动酶促防御系统,使过氧化物酶（POD）、过氧化氢酶（CAT）和超氧化物歧化酶（SOD）的活性得到提高,同时也减慢了还原型谷胱甘肽（GSH）含量下降的速率,增加了VC含量。3种浓度的CO2处理还可有效减慢呼吸速率,抑制腐烂的发生并可有效提高木质素含量和果实硬度,其中5%O2＋30%CO2更有利于延缓衰老进程,可使有效贮藏期延长至95d左右。研究认为：蓝莓对高浓度CO2有很强的耐力,高浓度CO2箱式气调用于蓝莓贮藏具有很好的保鲜效果。     

抗坏血酸处理抑制李果实冷害作用机理的研究

为寻找减轻李果实冷害的新途径,以新鲜李子为试材,研究李果实经不同浓度的抗坏血酸处理后冷害与酶促褐变机理.结果表明,对照果冷藏12d后,多酚含量和PPO活性都呈现上升趋势,MDA含量和冷害指数开始逐渐提高,说明冷害已经启动.而抗坏血酸处理组延缓了多酚含量的上升趋势,提高了PPO、POD、CAT的活性,外观和内部冷害指数明显降低,SOD活性变化不大.处理1 MDA含量明显低于对照,说明用抗坏血酸处理李果实,从外观上明显抑制了李果实冷害的发生.综合内、外两种冷害指数,只有处理1抑制冷害的效果最好,保持了李果实较好的贮藏品质.     

Effects of initial low oxygen and perforated film package on quality of fresh‐cut cabbages

The effects of perforated film packages (PFP) with different oxygen partial pressures (5, 8 and 10 kPa) and a barrier package (BP) at 21 kPa of O₂ on the quality of fresh‐cut cabbages were studied at 5 and 20 °C. The microbial growth, appearance, flavor, ascorbic acid content and polyphenol oxidase activity were determined during storage. The results indicated that fresh‐cut cabbages had better color retention and quality in PFP. Oxidation of ascorbic acid (AA) and browning of fresh‐cut cabbage were inhibited effectively using a PFP and an initial oxygen partial pressure equal to 5 kPa. Analysis of microbial growth also showed that the total count on fresh‐cut cabbage was relative lower in PFP with an initial low O₂ content. Loss of total ascorbic acid was much lower in PFP than that in BP by suppressing AA oxidation. The results of sensory evaluation showed that flavor and appearance were maintained effectively at 5 °C and significant differences in flavor were found between PFP and BP both at 5 and 20 °C, while significant differences in appearance were found between PFP and BP only at 20 °C. Copyright © 2007 Society of Chemical Industry