Study of the dynamic changes in the non-volatile chemical constituents of black tea during fermentation processing by a non-targeted metabolomics approach

Fermentation is a critical manufacturing process to produce black tea, in which the chemical compositions are greatly changed. However, the dynamic changes of this sophisticated process are far from clear, and were often characterized by determining a small number of compounds. In this study, we applied a non-targeted metabolomics approach based on ultra-high performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry to comprehensively profile the variations of metabolites in tea samples with various fermentation durations of 0, 1, 2, 4, 6, 8, 10, 12 and 14 h. Principal component analysis indicated obvious stepwise alterations of tea metabolome during the fermentation. Relative quantitation of 61 identified metabolites including catechins, dimeric catechins, flavonol glycosides, amino acids, phenolic acids, alkaloids, and nucleosides revealed distinct changes of phenol pathway. Dynamic changes of a part of these compounds were mapped for the first time. To the best of our knowledge, this study offered the most comprehensive profiles of metabolite changes during the tea fermentation process.     

安徽省部分城乡居民血清维生素A水平及相关因素分析

了解安徽省部分城乡地区6周岁以上居民维生素A营养状况及其相关因素分析。通过多阶段分层与人口成比例的整群随机抽样的方法抽取安徽省合肥市某区和安庆市某农村年龄在6周岁以上居民468名,于2010年8月至2010年10月进行问卷调查,并采集清晨空腹静脉血分离血清,用超高效液相色谱(UPLC)测定血清视黄醇浓度水平,同时测定部分生理生化指标。研究对象血清维生素A缺乏及边缘性缺乏率为15.6%(血清视黄醇0.3μg/mL),维生素A正常率为84.4%(血清视黄醇0.3μg/mL)。调查对象的维生素A水平在地区、性别、年龄、受教育程度、人均年收入、BMI、DBP、SDP、TC和TG分布上存在差异(P0.05)。单因素线性回归分析发现血清视黄醇浓度水平与地区、年龄、受教育程度、BMI、DBP、SBP、TC、TG和Hb呈正相关。多元线性回归分析发现血清视黄醇浓度水平与地区、年龄、TC和TG呈正相关。安徽省部分城乡地区6周岁以上居民存在一定比例的维生素A缺乏状况,并可能受地区、年龄、性别、TC和TG等因素影响。     

2010—2020年中国大陆金黄色葡萄球菌及其肠毒素引起的食源性疾病暴发事件归因分析

目的 分析我国金黄色葡萄球菌及其肠毒素引起的食源性疾病暴发事件的流行病学特征。方法 收集整理2010—2020年国家食源性疾病暴发监测系统和文献检索的数据,对金黄色葡萄球菌及其肠毒素引起的暴发事件进行归因分析。结果 共纳入2010—2020年食源性疾病暴发事件703起（监测系统694起,文献数据9起）,单维度归因分析发现原因食品中肉类食品最高,占28.3%（199/703）,主要引发环节中因食品存储不当最高,占15.2%（107/703）,主要发生场所中餐饮服务场所最高,占85.2%（599/703）;多维度分析结果显示,华东地区各季节事件发生数均最多。除肉类食品外,我国华东和华南地区主要原因食品还有糕点类食品和米面食品,这两种食品多以存储不当而引发。发生在餐饮服务场所的暴发事件中肉类食品和米面食品主要是由于加工时污染致病因子引发,而糕点类食品主要是由于存储不当引发。结论 由金黄色葡萄球菌及其肠毒素引发的食源性疾病以肉类食品高发,应对餐饮服务场所、食品加工、储存等环节加强监管,降低发病风险。     

我国进口干酪制品中硝酸盐、亚硝酸盐含量调查及暴露风险评估研究

目的 了解我国进口干酪制品中硝酸盐、亚硝酸盐含量水平,并评估我国成人干酪消费人群健康风险。方法 基于我国市售的进口干酪制品中硝酸盐、亚硝酸盐含量和2012年我国居民干酪消费量数据,通过概率评估方法,对我国成人干酪消费人群的膳食硝酸盐、亚硝酸盐暴露量进行估计,并分别与联合国粮农组织/世界卫生组织食品添加剂联合专家委员会（JECFA）制定的硝酸盐每日允许摄入量（ADI）和欧洲食品安全局（EFSA）制定的亚硝酸盐ADI比较后进行风险表征。结果 162份进口干酪样品中,硝酸盐的检出率为89.5%,平均含量为11.23 mg/kg;亚硝酸盐仅2份检出,含量为0.4和0.6 mg/kg。不同种类进口干酪制品中硝酸盐的平均含量从高到低依次为软质、半硬质、其他、硬质。我国成人通过进口干酪硝酸盐的平均暴露量为5.13 μg/kg BW/d,占ADI的0.14%,高暴露人群（P95）为20.06 μg/kg BW/d,占ADI的0.55%。结论 我国进口干酪制品中硝酸盐的检出率较高,且不同种类进口干酪制品其含量存在差异,而亚硝酸盐检出率很低。我国成人通过进口干酪暴露硝酸盐的健康风险较低。     

Synthesis of tellurium nanowires and their transport property

By using Na₂TeO₃ and Na₂S₂O₃ as starting materials, tellurium nanowires with diameter around 25 nm were synthesized via a hydrothermal reaction at 160 °C, X-ray diffraction (XRD) showed that the product was a pure trigonal phase and TEM image indicated the widths of nanowires were in the range of 10–40 nm. Through further high-resolution TEM (HRTEM) analysis, a preferential growth direction along the [0 0 1] zone axis was observed. The intrinsic structure of tellurium, as well as the directing role of PVP leading to the formation of the 1D nanostructure was briefly discussed. Field effect transistor from individual nanowire was constructed, the nanowire device revealed a pronounced gating effect, and yield a threshold voltage of 40 V, an on–off ratio as high as 10³_, and a mobility of 163 cm² V^?1 S^?1 at V_ds = ?0.1 V.     

超高效液相色谱-串联质谱法测定动物源性食品中硝基呋喃代谢物

目的建立动物源性食品中四种硝基呋喃代谢物的超高效液相色谱串联质谱(ultra pressure liquid chromatography-tandem mass spectrometry,UPLC-MS/MS)的快速检测方法。方法样品经盐酸溶液水解,邻硝基苯甲醛(2-NBA)37℃衍生16 h后,调节衍生液的pH=7.6,用乙酸乙酯提取。分析物采用电喷雾电离,正离子扫描,多反应检测模式(MRM),基质匹配内标标准曲线法定量。结果四种代谢物的工作曲线在0.1～10.0μg/L浓度范围内线性良好,相关系数R2均达到了0.995以上,氨基脲(SEM或SCA)与1-氨基-乙内酰脲(AHD)最低检出限均为0.1μg/kg,5-吗啉甲基-3-氨基-2-恶唑烷基酮(AMOZ)与3-氨基-2-恶唑烷基酮(AOZ)最低检出限均为0.05μg/kg。平均回收率在91.8%～107.0%之间,相对标准偏差均小于10%。结论样品前处理简单、测定时间短、灵敏度高,适用于猪肉、牛肉、鸡肉、猪肝和水产品(鱼类及虾类)中硝基呋喃类代谢物残留的快速测定。     

超高压液相色谱-串联质谱法检测猪肉中玉米赤霉醇类物质

目的 建立猪肉中6种玉米赤霉醇类物质(α-玉米赤霉醇、β-玉米赤霉醇、α-玉米赤霉烯醇、β-玉米赤霉烯醇、玉米赤霉酮和玉米赤霉烯酮)的超高压液相色谱-串联质谱(UPLC-MS/MS)检测方法。方法 样品经β-葡萄糖苷酶/硫酸酯酶酶解, 无水乙醚萃取, 再经氢氧化钠溶液液-液分配, 最后通过HLB固相萃取柱富集净化, UPLC-MS/MS检测, 基质匹配外标标准曲线法定量。结果 6种玉米赤霉醇类物质的线性范围为1.0~250 μg/L, 相关系数r＞0.990。当取样量为5.0 g时, 6种玉米赤霉醇类物质检出限为0.4 μg/kg。3个不同水平(添加1.0、5.0、20 μg/kg)的加标平均回收率为66.0%~79.5%, 相对标准偏差不大于10%。结论 所建立的方法具有较好的回收率和精密度, 准确度和灵敏度高, 符合猪肉中玉米赤霉醇类物质痕量的检测要求, 为大通量样品的食品安全检测提供更灵敏、高效的技术支持。     

超高压液相色谱-电喷雾串联四极杆质谱内标法同时测定禽类食品中11种喹诺酮类药物

目的建立同时测定禽类食品中11种喹诺酮类药物残留量的超高压液相色谱-电喷雾串联四极杆质谱(UPLC-ESI-MS/MS)分析方法。方法鸡肉和鸡蛋样品经1%乙酸乙腈(1∶100,V/V)混合液提取,冷冻离心与正己烷脱脂净化,以10 mmol/L乙酸铵(含0.1%甲酸)-甲醇为流动相,采用电喷雾电离,正离子扫描,多离子反应监测(MRM)模式,基质匹配同位素内标,标准曲线法定量。结果 11种喹诺酮类药物在0.05~50.0μg/L的浓度范围内线性良好,相关系数R~2≥0.997 4,检出限范围为0.05~0.10μg/kg,平均回收率为82.4%~104.3%,相对标准偏差小于15.0%。结论该方法的样品前处理过程简单,净化效果好,减少了基质效应的影响,适用于大批量禽类食品中喹诺酮类药物残留量的快速测定。     

Bioinspired Amyloid Fibril-Based Hydrogel with Engineering Programable Functionalities for Diverse Applications

Natural proteins display organized hierarchical structures and tailored functionalities that cannot be achieved by synthetic approaches, highlighting the increased interest in developing protein-based materials. Protein self-assembly allows fabricating sophisticated supramolecular structures from relatively simple building blocks, a strategy naturally employed by amyloid proteins and intrinsically disordered proteins. However, the design of self-assembled bioinspired materials with multi functionalities is still challenging. Inspired by the natural self-assembly proteins (such as mussel foot proteins and amyloid proteins), a temperature-inducible engineering programable hydrogel-like amyloid nanostructure is developed by using a genetically modular fusion approach. The resulting hydrogel-like assemblies display outstanding adhesive capacity, high stability, and broad substrate universality. The employed SpyCatcher/SpyTag system allows modifying the hydrogel-like assemblies with any functional proteins of interest. Owing to their strong adhesive capacity and functional flexibility, such amyloid fibril-based hydrogel shows advantages in the immobilization of diverse enzymes for highly efficient biocatalysis, fabrication of multi-layered functional coatings, and construction of functionalized 3D scaffold for cell culture. Overall, a modular and straightforward approach is established to obtain a genetically programable nanostructure platform. The novel hydrogel-like assemblies described here may be potentially applied to but not limited to synthetic biology, surface/interface engineering, and tissue engineering.