自发气调包装对不同品种青椒贮藏品质的影响

目的 探究自发气调包装对不同品种青椒贮藏品质的影响。方法 以贵州主栽的“改良螺丝椒王”和“黔椒8号”品种为实验材料,使用MP20气调包装袋对其进行包装处理,贮藏于(10±0.3)℃的环境内32d,每隔8 d进行一次相关指标的测定,研究贮藏期间不同品种间青椒品质变化。结果 随着贮藏时间的延长,青椒果实的腐败率、失重率和转红指数均呈上升趋势,相比之下,“黔椒8号”的贮藏性能优于“改良螺丝椒王”。两个品种共检测出48种挥发性物质,主要以醛类、酯类为主;在贮藏末期,“黔椒8号”对醛类和酯类物质的保留率高于“改良螺丝椒王”,风味损失较少。根据化合物的香气活性值得出,两个辣椒品种共有的关键特征呈香物质为:(E,E)-2,4-癸二烯醛、水杨酸甲酯、肉豆蔻醛、正己醛、2-己烯醛和β-紫罗兰酮,其含量均随着贮藏时间的延长而下降。贮藏期间,“改良螺丝椒王”特有的挥发性物质为3-蒈烯和反式-2-壬醛,“黔椒8号”特有的挥发性物质为1-己醇和环己醇。结论 在低温下采用MP20气调包装袋进行包装的“黔椒8号”的贮藏效果最佳。     

Labeling primary nerve stem cells with quantum dots

The primary nerve stem cells (NSCs) were labeled with the carboxyl QDs by passive loading. The studies on QDs' effect on the NSCs showed that with a proper concentration, QDs have little effect on NSCs growth and proliferation within a week, and the QDs did not affect either differentiation potential of NSCs or the protein expression of neuron and astrocyte derived from NSCs. The results suggested that this labeling method is appropriate for labeling studies in vitro. Combined with the unique optical properties of QDs, it is possibly to fulfill NSCs fate-tracking in vivo.     

Optimization of field-amplified sample injection for analysis of peptides by capillary electrophoresis-mass spectrometry

A versatile experimental approach is described to achieve very high sensitivity analysis of peptides by capillary electrophoresis-mass spectrometry with sheath flow configuration based on optimization of field-amplified sample injection. Compared to traditional hydrodynamic injection methods, signal enhancement in terms of detection sensitivity of the bioanalytes by more than 3000-fold can be achieved. The effects of injection conditions, composition of the acid and organic solvent in the sample solution, length of the water plug, sample injection time, and voltage on the efficiency of the sample stacking have been systematically investigated, with peptides in the low-nanomolar (10(-9) M) range readily detected under the optimized conditions. Linearity of the established stacking method was found to be excellent over 2 orders of magnitude of concentration. The method was further evaluated for the analysis of low concentration bioactive peptide mixtures and tryptic digests of proteins. A distinguishing feature of the described approach is that it can be employed directly for the analysis of low-abundance protein fragments generated by enzymatic digestion and a reversed-phase-based sample-desalting procedure. Thus, rapid identification of protein fragments as low-abundance analytes can be achieved with this new approach by comparison of the actual tandem mass spectra of selected peptides with the predicted fragmentation patterns using online database searching algorithms.     

肃南牦牛不同部位脂肪中脂肪酸组成分析

目的 为建立科学的牦牛脂肪中脂肪酸评价方法,利用主成分分析法对牦牛不同部位脂肪品质进行综合评价,以期为指导高品质牦牛产品加工和品质评价提供依据。方法 本试验采集肃南牦牛肋条表面、臀肌、肾周、肠周及皮下5个不同部位的脂肪,测定牦牛不同部位脂肪AV、POV,并采用GC-MS技术对5个不同部位脂肪中脂肪酸组成及含量进行测定,采用面积归一化法进行定量,探究肃南牦牛不同部位脂肪组成成分的差异性,并结合多元统计分析讨论脂肪酸成分含量对不同部位脂肪品质的影响。结果 以脂肪酸种类及含量为评定指标,在5个不同部位中均检出36种脂肪酸,以硬脂酸为主,含量都在70~160 g/100g之间;其次是油酸、棕榈酸和亚油酸含量较高。对不同部位的SFA、MUFA、PUFA含量分析表明,皮下脂肪UFA/SFA比值较大,风味较佳、适口性更好。PCA分析表明前三个主成分的累积贡献率高达99.41%,很好的实现了牦牛5个不同部位脂肪的区分。结论 牦牛脂肪中脂肪酸种类丰富,富含多不饱和脂肪酸。不同部位脂肪酸含量有着显著性差异,PCA分析对牦牛不同部位脂肪品质进行综合评价是客观、可行的,为牦牛不同部位脂肪鉴别提供了快速、准确的新方法。     

紫外线与亚硝基胍复合诱变选育高效降解亚硝酸盐乳酸菌

目的 通过诱变方法获得高效降解亚硝酸盐的优良乳酸菌应用于降低腌制品中的亚硝酸盐。方法 以前期实验筛选获得的降解亚硝酸盐性能较强乳酸菌D2作为初始诱变菌株, 采用紫外线和亚硝基胍复合诱变, 选育高效降解亚硝酸盐的乳酸菌。结果 经15 W紫外线和0.5 mg/mL亚硝基胍三轮复合诱变得到一株优良乳酸菌, 该菌株24 h降解亚硝酸盐(200 mg/L)降解率为91.4%, 较初始菌株提高了12.7%; 以亚硝酸钠为底物, 其产亚硝酸盐还原酶的比活力为7.7 mmol/L, 较诱变前提高42.9%; 连续传代培养后降解亚硝酸盐能力和产亚硝酸盐还原酶活力性能稳定。结论 通过紫外线和亚硝基胍复合诱变, 获得一株遗传稳定性良好的高效降解亚硝酸盐的菌株。     

动物源性食品中糖皮质类激素残留检测技术的研究进展

近年来, 食品中激素的残留引起了社会的广泛关注。糖皮质类激素能提高饲料转化率, 促进畜禽生长, 常用于畜牧生产中。然而动物生长过程中过量使用这些激素, 会导致激素在动物源性食品中的残留, 影响人类健康。本文介绍了糖皮质类激素及其对人类的危害, 总结了动物源性食品中糖皮质类激素的检测方法, 包括利用振荡提取、超声提取、固相萃取、液液分配、加压溶剂萃取等提取和净化方法, 以及采用气相色谱法、液相色谱法、气相色谱-质谱联用法、液相色谱-质谱联用法分析检测糖皮质类激素的研究进展。