Multiplex PCR system to track authorized and unauthorized genetically modified soybean events in food and feed

A diverse range of genetic elements has been used to develop genetically modified organisms (GMOs) over the last 18 years. Screening methods that target few elements, such as the Cauliflower Mosaic Virus 35S promoter (P-35S) and Agrobacterium tumefaciens nopaline terminator (T-nos), are not sufficient to screen GMOs. In the present study, a multiplex PCR system for all globally commercialized GM soybean events was developed to easily trace the events. For this purpose, screening elements of 24 GM soybean events were investigated and 9 screening targets were selected and divided into three individual triplex PCR systems: P-35S, ribulose-1,5-bisphosphate carboxylase small subunit promoter of Arabidopsis thaliana, T-nos, T-35S, pea E9 terminator, open reading frame 23 terminator of A. tumefaciens, proteinase inhibitor II terminator of potato, acetohydroxy acid synthase large subunit terminator of A. thaliana, and the revealed 3′ flanking sequences of DP-305423-1. The specificity of the assays was confirmed using thirteen GM soybean events as the respective positive/negative controls. The limit of detection of each multiplex set, as determined using certified reference materials of specific GM events, ranged from 0.03 to 0.5%, depending upon target. Furthermore, 26 food samples that contained soybean ingredients, which were purchased from the USA, China, Japan, and Korea, were analyzed, 17 of which contained one or more GM soybean events. These results suggest that the developed screening method can be used to efficiently track and identify 24 GM soybean events in food and feed.     

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.     

自动QuEChERS结合气相色谱-串联质谱法测定花生油中172种农药残留

目的：基于自动QuEChERS方法建立了花生油中172种农药残留的气相色谱-串联质谱(gas chromatography-tandem mass spectrometry,GC-MS/MS)快速检测技术。方法：花生油样品加水后,加入15 mL乙腈提取,放入自动QuEChERS前处理设备,以N-丙基乙二胺(primary secondary amine,PSA)和十八烷基硅烷键合硅胶(C18)为填料进行净化。净化后,取2 mL上清液,在氮气气流下吹至近干,用1 mL乙酸乙酯复溶后,过0.22 μm有机微孔滤膜,应用气相色谱－串联质谱(GC-MS/MS)检测,HP-5MS UI气相色谱柱分离,程序升温,在多重反应监测(MRM)模式进行测定,采用基质匹配外标法进行定量。结果：方法所检测的172种农药的线性决定系数(R_²)均大于0.995,检出限范围为1～5 μg/kg,定量限范围为2～10 μg/kg;在10 μg/kg、50 μg/kg和100 μg/kg 3个添加水平下,平均回收率在70.1%～112.8%、72.6%～114.3%、71.8%～114.9%范围内,相对标准偏差(RSDs)均小于15.0%(n=6)。结论：该方法操作简单,灵敏高效,能够满足花生油中多农药残留检测的需求,也可以为复杂基质的自动化前处理提供参考。     

自动QuEChERS结合液相色谱-串联质谱法测定香叶中的212种农药残留

目的 建立自动QuEChERS结合液相色谱-三重四极杆串联质谱法测定香叶中212种农药残留.方法 香叶样品用乙腈提取,使用300 mg十八烷基硅烷键合硅胶(C18)+75 mg Nano-Carb、4.0 g无水硫酸镁和1.0 g氯化钠进行净化,经自动样品制备系统进行制备后,应用液相色谱-三重四极杆串联质谱法进行检测,...     

Tea: A new perspective on health benefits

Although among the five main types of teas (white, green, oolong, black and pu-erh), black tea is the most consumed worldwide, an impressive number of scientific publications have been focused on green tea and its major compounds, flavan-3-ols (“catechins”). However, besides flavan-3-ols, there are other compounds present in tea that could be accounted as potential bioactive compounds. Therefore, the objective of the present review is to provide a new perspective on the health benefits associated with tea consumption by critically analyzing the available literature on the potential tea bioactive compounds and the current level of scientific evidence for these health benefits. Until now the exact mechanisms of action or compounds responsible for the health benefits associated with tea consumption have only been poorly investigated. It is important to consider that tea compounds will be extensively metabolized to different metabolites that will, most likely, be the compounds circulating in blood and potentially reaching the different sites of action.     

Carotenoid composition,distribution and degradation to flavour volatiles during black tea manufacture and the effect of carotenoid supplementation on tea quality and aroma

Carotenoid content of tea leaves ranges from 36 to 73 mg/100 g dry weight, and is dominated mainly by β-carotene, lutein and zeaxanthin. Among the cultivars, China contained the maximum and Assam clone the least. Carotenoid fractions were found to degrade to different extents at different stages of tea processing. The carotenoid content was as low as 25 mg/100 g in the made tea. Only a small quantity was leached into the brew, the remaining being retained in the infused leaf/tea residue. The high stability of carotenoid in tea is mainly due to the presence of antioxidants, such as polyphenols and catechins. Carotenoid degradation was found to be greater in the CTC (Crush, Tear, Curl) process than the orthodox process, greater in withered than unwithered, and in the order β-carotene > zeaxanthin > lutin. Vitamin A value was greater in orthodox tea than CTC tea and it varied with clones. The carotenoid degradation was found to yield large quantities of desirable aroma volatiles in made tea, giving a high grown flavour status. An increase in endogenous carotene content enhanced all the quality parameters of tea, the VFC (volatile flavour compounds) index, almost being doubled. The tasters' evaluation also revealed the same trend. It was found that a 1:1 NK application at the rate of 300 kg/ha/year enhanced the carotenoid content of green leaves in the second week after application, with subsequent decline.     

高效液相色谱-串联质谱法测定水果中多种 天然植物生长调剂的残留量

目的 采用高效液相色谱-串联质谱法建立了同时测定水果中赤霉素GA3、吲哚-3-乙酸和1-萘乙酸3种天然植物生长调剂残留的检测方法。方法 样品经QuEChERS法进行预处理,以1%乙酸乙腈提取,无水硫酸镁和C18粉末净化。选用水-乙腈为流动相,C18色谱柱分离,采用Agilent AJS ESI源、负离子扫描和多反应检测模式(MRM)质谱检测,基质匹配标准溶液外标法定量。结果 3种天然植物生长调剂在0.005-1.000 mg/L浓度范围内线性关系良好,赤霉素GA3的方法定量限(S/N=10)分别为0.010 mg/kg,吲哚-3-乙酸和1-萘乙酸均为为0.005 mg/kg。对空白水果样品进行0.020、0.050和0.100 mg/kg 3个添加水平的回收试验,赤霉素GA3、吲哚-3-乙酸和1-萘乙酸的回收率分别为75.4-109.8%、79.1-109.3%和79.6-112.9%,相对标准偏差(n=6)分别为3.5-17.4%、6.5-15.8%和4.8-13.9%。结论 该方法快速简便,定量准确,可满足水果中3种农药的残留检测要求。     

Determination of flavonols in green and black tea leaves and green tea infusions by high-performance liquid chromatography

Tea flavonols are potent antioxidants and make up 2–3% of the water-soluble solids from tea leaves. In this paper, the conditions necessary for hydrolysing and analysing flavonols in tea leaves and tea infusions are optimised and an isocratic elution system for the determination of the hydrolysed flavonols by high-performance liquid chromotography is presented. Aqueous ethanol was selected as the best solution for hydrolysing flavonoids in tea leaves. The contents of flavonols on a dry weight base in green tea leaves ranged from 0.83–1.59, 1.79–4.05, and 1.56–3.31 g/kg, and in black tea leaves from 0.24–0.52, 1.04–3.03, and 1.72–2.31 g/kg for myricetin, quercetin, and kaempferol, respectively. It was observed that the particle size of ground tea leaves significantly influenced the yield of flavonols. The contents of flavonols in different green tea infusions are given.     

ICP-MS/MS检测食品中磷、硒、砷的含量

研究建立了ICP-MS/MS检测食品中磷、砷和硒含量的检测方法。分析了P、As和Se在检测过程中常见的质谱干扰和电离效率,比较了标准模式（No Gas）、He模式、H2模式、O2模式以及双四极杆等各种检测模式,发现采用O2模式双质谱对P、Se的检测结果最为准确,As采用He模式即可实现精准检测。根据优化后的检测条件,经过Q1时同位素M进入碰撞反应池,与O2反应生成的氧化物MO进入Q2被采集,通过二级质谱质量转移几乎可以彻底消除一切干扰。结果显示,P在2.0~500 μg/L范围内、As和Se在0.5~200 μg/L浓度范围内均具有良好的线性,相关系数均大于0.9995,加标回收显示回收率在94.0~101.5%之间,RSD%不大于2.1%。最终采用该方法对国家标准物质乳粉样品（GBW 10017）、螺旋藻（GBW 10025）进行测定,结果均在标准值范围内。本方法可以满足食品中P、As和Se等元素的精准检测。