Development and validation of an analytical method for detecting chlorantraniliprole residues in fresh tea leaves

An efficient method using multiwalled carbon nanotubes(MWCNTs)as dispersive solid-phase extraction sorbent was established for determining chlorantraniliprole residues in fresh tea leaves,which are known to be a troublesome matrix containing abundant pigments,via gas chromatography with an electron capture detector.Acetonitrile was used as the extraction solvent,with sodium chloride enhancing the analyte partition in the organic phase.The optimal mixture of MWCNTs and primary secondary amine(PSA)was based on the distribution of the target analyte recovery and on the clean-up efficiency;while matrix-matched calibration was recommended to combat the matrix effect.Mean recoveries of 95.2%–108.8%were obtained with intraday and interday precisions of less than 7.9%and 10.3%,respectively.Good linearity was observed for concentrations of 0.02–1.0 mg/kg with a correlation coefficient of 0.9984.The limits of detection and quantification were 0.005 mg/kg and 0.02 mg/kg,respectively.The method was employed to investigate the dissipation dynamics of chlorantraniliprole in fresh tea leaves with real field samples.Consequently,the dissipation rates of chlorantraniliprole in fresh tea leaves followed pseudo-first-order kinetics with a half-life of 1.9 d,and the average chlorantraniliprole residue content was below 0.02 mg/kg with a harvest withholding period of 14 d.

Determination of 18 Kinds of Amino Acids in Fresh Tea Leaves by HPLC Coupled with Pre-column Derivatization

A rapid and accurate quantitative method of high performance liquid chromatography( HPLC) with fluorescence detector has been developed for the analysis of 18 kinds of amino acids in fresh tea leaves. The samples were minced and mixed,and extracted with ultra pure water at 90℃ for 20 min. The 6-aminoquinolyl N-hydroxy-succinimidyl carbamate( AQC) was used as pre-column derivatization reagent. Gradient HPLC separation was performed on a C_(18) column( Symmetry C_(18),3. 9 mm × 15 cm,4 μm). Good linearity between concentrations and peak areas was achieved in the concentration range of 5. 0-250 μmol/L for 18 kinds of amino acids. The method was validated by the analysis of five replicates. The 18 kinds of amino acid standards were spiked in fresh tea leaf samples and the average recovery rate was 86. 25%-109. 05% with relative standard deviations( n = 5) ranging from 6. 03% to 10. 56%. The limit of detection( LOD) for the analytes was0. 05-1. 27 μmol/L. The method was successfully applied to the analysis of the 18 kinds of amino acids in fresh tea leaves from east Dongting and west Dongting mountains in Suzhou. The results indicate that the method is simple,rapid,precise and reliable.

Stability Studies on the Aqueous Extract of the Fresh Leaves of Combretum Micranthum G. Don Used as Antibacterial Agent

The fresh leaves of Combretum micranthum were harvested during the rainy season in Akwa Ibom State, washed and subjected to extraction by maceration in distilled water. Concentration was done with a rotary evaporator. The extracts were tested for content of the following phytochemicals using standard methods： alkaloids, saponins, tannins, anthraquinones, cardiac glycosides, flavonoids and steroids. Antibacterial sensitivity test of the extract was carried out on S. aureus, B. subtilis and E. coli using agar well diffusion method and Ampiclox as control. The effect of storage time of the extract on its antibacterial activity was determined after the extract was kept at room temperature for 1 h, 24 h, 48 h and 72 h, respectively. Preparations of 200 mg/mL of the aqueous extract were made with additives as follows： （a） no additive; （b） methyl paraben （0.3%）; （c） propyl paraben （0.3%）; （d） sodium metabisulfite （0.01%）; （e） A combination of methyl paraben （0.3%） and propyl paraben （0.3%）; （f） A combination of methyl paraben （0.3%）, propyl paraben （0.3%） and sodium metabisulfite （0.01%）. A visual observation of the stabilized preparations was employed on daily basis for 30 days. Phytochemical analyses on the aqueous extract of the fresh leaves showed the absence of alkaloids, anthraquinones and flavonoids. Saponins, cardiac glycosides and steroids were present in moderate amounts and there was abundance of tannins. The extract had similar effect on both S. aureus and E. coli cultures but activity was very low with B. subtilis. When S. aureus activity increased with time of storage up to 48 hours, thereafter the activity started reducing. However, the activity of E. coli continued to increase with time （within the study period）. Thus, it appears reasonable to store the extract for at least 48 hours before the use for enhanced activity.

UTILIZATION AND FRESH PRESERVATION OF CUT LEAVES OF FIVE WILD PTERIDOPHYTE SPECIES ON MAOER MOUNTAINS

The cut leaves of five pteridophyte species were evaluated on their usage in cut flowers. Two species, Lunathy rium coreanum and Dryopteris crassirhizoma, were selected. The ef fects of vase-holding and fresh preservation of the cut leaves under different conditions was studied. By measuring the contents of soluble protein and chlorophyll of leaves, the best methods of fresh preservation was determined with the use of fresh preservation and wet storage. L. rium coreanum (christ) Ching may last 14 days. The best liquid used to arrange flowers in a vase is 5 g/L sucrose.With the use of fresh preservation liquid and wet storage. D. crassirhizoma may last 34 days.

Seasonal changes of bioelements in litter and their potential return to green leaves in five species of tropical dry deciduous forest, western India

The Litter nutrient concentrations of N, P, Ca, Mg, K and Na in mature leaves, twigs and reproductive parts and their relationship between senescent and young leaves were investigated in five forest species： Acacia nilotica, Acacia leucophloea. Tectona grandis, Miliusa tomentosa and Butea monosperma in Indian tropical dry deciduous forest in Western India.. Total dry matter of plant species was recorded and analyzed for N, P, Ca, Mg, K and Na. A. nilotica had the highest concentrations of N in leaf, while ,4. leucophloea had the highest concentrations of Ca and Mg in leaf. The highest concentrations of P in leaf were found in A. nilotica, A. leucophloea and B. monosperma where as lowest in T. grandis and M. tomentosa. No significant differences in K and Na were registered among the species. A marked seasonal variability was ob- served in the concentrations of N, P and K, except for Ca and Mg. Potas- sium is the single element that undergoes leaching and mobilization in all species. Resorped N and P can be used for the production of fresh leaf in the following annual cycle. Nutrient resorption and retranslocation from senescent leaves and litter supports the production of new foliage and increase the fertility of soil.

‘白叶1号’异地生长鲜叶品质成分研究初探

从2021年开始,项目组连续三年对安吉‘白叶1号’捐苗种植地的贵州普安、雷山、沿河,湖南古丈,四川青川三省五县和安吉原产地的茶树生长习性和品质进行跟踪研究。本文总结2023年春浙江、贵州和湖南茶鲜叶品质主要成分,按安吉白茶采摘标准采一芽二叶,分析了鲜叶中水浸出物等主要理化成分的含量以及异地生长的‘白叶1号’茶鲜叶品质差异。结果显示,2023年春茶‘白叶1号’异地与原产地鲜叶理化成分在水浸出物、游离氨基酸和茶氨酸含量方面存在显著性差异,原产地的水浸出物总量>42%,游离氨基酸含量>4.5%,茶氨酸含量>2.5%;茶苗受捐地水浸出物含量>37%,游离氨基酸含量>5.5%,茶氨酸含量>3.0%;非基地水浸出物含量>36%,游离氨基酸含量>4.0%,茶氨酸含量>1.5%。

不同贮青温度及方式对红碎茶品质的影响

本实验以控温15、25℃,常温(22~28℃)以及沤红4种处理的英红九号茶青制成的红碎茶为实验材料,采用感官审评、顶空固相微萃取与气相色谱-质谱联用技术和生化分析技术研究不同贮青处理对红碎茶感官品质、香气物质、生化成分的影响。结果表明:4个处理中,15℃贮青能提高红碎茶的鲜爽度、甜度及甜香挥发性物质的含量,更有利于品质形成,而茶青沤红劣变会显著影响红碎茶感官品质和表征品质的化合物含量,实验结果可为茶青管理及红碎茶品质的提升提供参考。

Real-time monitoring of optimum timing for harvesting fresh tea leaves based on machine vision

The harvesting time of fresh tea leaves has a significant impact on product yield and quality.The aim of this study was to propose a method for real-time monitoring of the optimum harvesting time for picking fresh tea leaves based on machine vision.Firstly,the shapes of fresh tea leaves were distinguished from RGB images of the tea-tree canopy after graying with the improved B-G algorithm,filtering with a median filter algorithm,binary processing with the Otsu algorithm,and noise reduction and edge smoothing using open and close operations.Then the leaf characteristics,such as leaf area index,average length,and leaf identification index,were calculated.Based on these,the Bayesian discriminant principle and method were used to construct a discriminant model for fresh tea-leaf collection status.When this method was applied to a RGB tea-tree canopy image acquired at 45°shooting angle,the fresh tea-leaf recognition rate was 90.3%,and the accuracy for fresh tea-leaf harvesting status was 98%by cross validation.Hence,this method provides the basic conditions for future tea-plantation operation and management using information technology,automation,and intelligent systems.

开化主要产茶区域鲜叶品质成分评价

为评估开化不同区域环境条件下茶树鲜叶的品质特征,同时为不同品种原料的适制性提供理论依据,研究选取开化五个主要产茶区的3种茶树鲜叶为原料,经冷冻干燥固样后,分别对其非挥发性物质及挥发性物质进行分析。结果表明,不同环境下生长的同一茶树品种的茶多酚、氨基酸、咖啡碱、可溶性糖存在一定的差异,大部分鲜叶原料适制绿茶。在挥发性组分方面,不同区域所产群体种、福鼎大白茶和翠峰其挥发性物质差异明显,分别鉴定得到11种、7种、14种关键差异性挥发性物质。

不同茶树品种鲜叶内含物质与根际细菌群落的关联性分析研究

为探究不同茶树品种鲜叶内含物质与其根际细菌群落的相关性,以‘保靖黄金茶1号’和‘桃源大叶’为试验品种,利用非靶向代谢组学方法测定茶树鲜叶内含成分,利用微生物组学鉴定其根际细菌群落。结果共鉴定出‘保靖黄金茶1号’和‘桃源大叶’鲜叶中显著差异化合物53个,其根际差异细菌群落11种。进一步通过关联性分析确定了‘保靖黄金茶1号’和‘桃源大叶’鲜叶差异内含成分与根际差异细菌群落显著性相关。该研究可为探究根际微生物对茶树鲜叶质量的影响提供参考。

紫阳群体种鲜叶萎凋过程中主要生化成分的动态变化

以紫阳群体种1芽1叶(以下简称叶)为原料,研究紫阳群体种鲜叶萎凋过程中生化成分变化情况,在温度20~25℃、相对湿度75%~80%的条件下进行室内自然萎凋,摊叶厚度2~3 cm,分别在萎凋0、8、10、12、14、16、18、20 h时取样并微波固样,磨碎测定其生化成分含量。紫阳群体种鲜叶萎凋过程中萎凋叶水浸出物含量呈先上升后下降趋势,但不同萎凋时间其含量差异不显著;萎凋叶茶多酚含量先下降后上升,但整体呈下降趋势,在萎凋8~20 h时不同萎凋时间茶多酚含量差异不显著,含量趋于稳定,在整个萎凋期间,茶多酚含量下降了5.60%;萎凋叶可溶性糖含量呈先下降后上升趋势,与萎凋12 h相比,萎凋20 h的萎凋叶可溶性糖含量上升了14.63%;萎凋叶游离氨基酸含量呈先上升后下降趋势,从萎凋开始至萎凋结束,其游离氨基酸含量增加了18.02%;在温度20~25℃、相对湿度75%~80%条件下,紫阳群体种鲜叶在萎凋18~20 h时达到萎凋适度。萎凋过程中,水分在生化成分变化过程中同时作为反应物和反应介质,萎凋叶含水量变化对茶叶生化成分产生了重要影响,应采取合理措施,协调萎凋叶含水量和生化成分含量变化情况,使其达萎凋最适程度。

春茶后不同修剪处理对夏秋茶机采效果研究

“春茶手采+夏秋茶机采”是一种兼顾经济效益和资源利用率的生产模式。为研究春茶后不同修剪处理对夏秋茶机采效果的影响,以‘福鼎大毫茶’与‘龙井长叶’为试验品种,在春茶提早结束和正常结束后分别进行轻修剪和重修剪,探讨不同修剪处理对夏秋茶产量性状及机采鲜叶机械组成的影响。结果表明,不同修剪时间主要影响叶层厚度,春茶提早结束进行修剪的茶树叶层厚度高于春茶正常结束后修剪的茶树;不同修剪程度主要影响树高、树幅、百芽重、产量及新梢的一致性,轻修剪的茶树树高、树幅、百芽重、产量和新梢一致性优于重修剪处理;修剪时间与修剪程度交互作用主要影响发芽密度,春茶正常结束后进行轻修剪茶树发芽密度最高。不同修剪处理对夏秋季机采鲜叶目标芽叶得率及破碎叶占比无显著影响。

桑叶醇提物-普鲁兰多糖复合涂膜对冷鲜牛肉保鲜效果的研究

为了研究桑叶醇提物(Ethanol extract of mulberry leaves,MLEE)与普鲁兰多糖(Pullulan polysaccharide,PPL)复合涂膜对冷鲜牛肉保鲜效果的影响,采用不同浓度(0.25%、0.5%、1.0%)MLEE与1.0%PPL复合涂膜对牛肉4℃条件下贮藏14d,在贮藏过程中对各项指标进行测定分析。结果表明:与对照组相比,复合涂膜处理降低了牛肉的pH值、剪切力、蒸煮损失率,且有效延缓了牛肉的总挥发性盐基氮(Total volatile basic nitrogen,TVB-N)和高铁肌红蛋白含量的升高,有效抑制了牛肉的菌落总数和嗜冷菌的生长,维持了牛肉较佳的感官品质。其中,1.0%MLEE-PPL复合涂膜处理对牛肉的保鲜效果最佳。

茶叶鲜叶氟含量调查分析

为探究茶叶鲜叶氟含量情况,本研究采集了不同叶位、生长阶段、季节和地区的茶叶鲜叶,经杀青烘干处理,采用沸水浴浸泡提取氟化物,选择电极法测定氟离子,通过数据比对和分析,探究了茶叶鲜叶氟含量、变化规律和影响因素。研究表明,不同叶位鲜叶的氟含量呈线性变化规律:新芽尖<第1叶<第2叶<第3叶<第4叶;不同叶龄鲜叶氟含量整体呈线性变化规律:1芽1叶<1芽2叶<1芽3叶<1芽4叶<1芽5叶。茶叶鲜叶嫩叶氟含量低于老叶氟含量;随着叶龄的增长,茶叶鲜叶氟含量呈现上升趋势。该研究为茶叶产业发展提供参考。

鲜法匀浆萃取烟叶中茄尼醇的研究

为了建立一种高效提取烟叶中茄尼醇的方法,对鲜法匀浆萃取烟叶中茄尼醇的工艺进行了研究,确定了最佳的工艺参数:提取原料为含水率80%的鲜烟叶,溶剂为90%的乙醇,匀浆时间20min,液固比为6:1(mL:g).将该法与超声提取、索氏提取和超临界二氧化碳萃取进行了比较.结果表明,在优化的条件下,鲜法匀浆对原料的匀浆粒度为40～80μm,茄尼醇的提取率为0.722%,分别是超声提取、索氏提取、超临界二氧化碳萃取的1.32、1.62和1.98倍.鲜法匀浆萃取所用提取时间短,提取溶剂用量少,因此,该法是一种高效提取烟叶中茄尼醇的方法.

茶鲜叶萎凋过程中儿茶素和生物碱的动态变化规律

以肉桂、水仙等10个茶树品种春季新梢（采摘嫩度为1芽2、3叶和中小开面2~4叶）为供试材料,在控温控湿（22~22℃、RH 35%~45%）条件下萎凋,于鲜叶萎凋失水减重率为0、15%、30%、45%、60%时取样,检测其儿茶素和生物碱含量的变化。结果表明,在萎凋失水率为30%~45%范围内,供试茶样中儿茶素组分含量及总量具有最大值,说明萎凋前期促进儿茶素的转化形成;随着萎凋失水程度加重,儿茶素组分EGCG、EC和ECG含量及其总量呈现先增后减、总体减少趋势,EGC和TB含量以逐步减少为主,而CAF含量和生物碱总量则表现为逐渐增加趋势,而且1芽2、3叶各组分变化幅度大于中小开面2~4叶;主成分分析和聚类分析均可获得较为一致的结果,即110份供试茶样均可按芽叶嫩度分成1芽2、3叶型和中小开面2~4叶型2种类型,基于萎凋工序分类的主成分分析显示供试茶样的儿茶素和生物碱在萎凋期间含量呈现递变性增减趋势,表明萎凋过程是儿茶素类物质在多酚氧化酶作用下长时间缓慢氧化和降解的过程。因此萎凋工序对儿茶素和生物碱含量有一定影响,可通过调节鲜叶萎凋失水程度来调控二者的含量及组成比例,从而为茶叶风味品质调整及其活性成分的开发利用提供依据。

名优茶机采鲜叶分级技术研究

用滚筛机(6CXF-70大宗茶鲜叶分级机,MCF自制名优茶鲜叶分级机),平面圆筛机(浙茶精766)、风选机(FX450型)等不同茶叶分级机械对相同机采鲜叶原料进行分级,鲜叶原料在不同筛孔、风力条件下,按芽叶大小、轻重归类,实现大小芽叶分离,测定经分级后得到的各类芽叶机械组成,比较分级效果。结果表明:试验用机器采摘的茶青机械组成中标准芽叶的比例(质量分数,下同)为23.54%,粗老芽叶的比例为43.33%,其他碎片的比例达到33.13%。该鲜叶不能作为名优茶生产。经滚筛机分级,在相同分级区段内,MCF分级机分级获得的标准芽叶比率较6CXF-70大宗茶鲜叶分级机高19%,且各筛孔下得到的原料等级界限清楚。利用不同筛孔分层设置的平面圆筛机分级原料,各层级中均有标准芽叶和其他芽叶混杂的情况,不能较好地分离出鲜叶中的标准芽叶。风选机分级能较好地清除机采鲜叶内其他碎片,但标准芽叶和粗老芽叶分离效果不明显;MCF和风选组合分级效果提高。机采鲜叶先经MCF分级,再风选处理,标准芽叶比例提高了16%,其他碎片比例下降了23%,从而有效地减少了标准芽叶和其他碎片混杂。然而先风选再MCF组合分级,分级效果不理想;但是调整自制分级机结构可在一定程度上获得等级差异明显的芽叶。综上,利用滚筛、平面圆筛、风选等方法可以使机采鲜叶原料在一定程度上按大小归类,不同方法分级差异大,其中滚筛分级是3种分级方法中可获得相对整齐、标准芽叶较多的分级方法,利用自制的名优茶鲜叶分级机(MCF)与风选组合分级效果最优。

QuEChERS-气相色谱-串联质谱法测定茶青中28种农药残留

建立了QuEChERS-气相色谱-串联质谱(GC-MS/MS)同时测定茶青中28种农药残留的分析方法。样品采用乙腈匀浆提取,经75 mg PSA、25 mg C18、4 mg GCB净化,GC-MS/MS多反应离子监测模式下检测,外标法定量。结果表明:在0.020~0.40 mg/L范围内,28种农药的质量浓度与对应的峰面积间呈良好的线性关系,决定系数均大于0.991。在0.10和0.50 mg/kg两个添加水平下,28种农药的平均回收率在77%~106%之间,相对标准偏差(RSD)在1.4%~8.0%(n=6)之间。方法的检出限(LOD)为5.0~20μg/kg,定量限(LOQ)为10~60μg/kg。该方法简单、快速、准确、灵敏度高,可用于茶青中多种农药残留的同时检测分析。

分散固相萃取-气相色谱法测定茶鲜叶中7种拟除虫菊酯类农药残留

建立了超声波提取、分散固相萃取净化、气相色谱-电子捕获法（GC-ECD）同时测定茶鲜叶中甲氰菊酯、高效氯氟氰菊酯、氯菊酯、氟氯氰菊酯、氯氰菊酯、氰戊菊酯和溴氰菊酯7种拟除虫菊酯类农药残留的方法。样品采用V（乙酸）∶V（乙腈）=1∶99的混合溶剂超声提取,适量乙二胺-N-丙基硅烷（PSA）、十八烷基硅烷键合硅胶（C18）和石墨化碳黑（GCB）吸附剂净化,GC-ECD测定,基质外标法定量。结果表明：在0.004~2 mg/L范围内,7种拟除虫菊酯类农药的峰面积与相应质量浓度间呈良好的线性关系,相关系数均大于0.999;在0.01~0.5 mg/kg的添加水平下,平均回收率为80%~101%,日内相对标准偏差（RSD）均小于8.4%（n=6）,日间RSD均小于9.3%（n=3）;7种农药在茶鲜叶中的检出限为0.002~0.02 mg/kg,定量限为0.01~0.05 mg/kg。该方法操作简单、定量准确、溶剂用量少,对检测条件要求低,可同时测定茶鲜叶中7种拟除虫菊酯农药的残留量。

壳聚糖/竹叶抗氧化物复合处理对鲜切生姜保鲜效果的影响

目的:为研究壳聚糖(chitosan,CTS)/竹叶抗氧化物(antioxidant of bamboo leaves,AOB)复合处理对鲜切生姜保鲜效果的影响。方法:将鲜切生姜分别采用蒸馏水、0.3%AOB、1.5%CTS以及0.3%AOB+1.5%CTS浸泡处理5 min,取出沥干分装于市购的聚乙烯保鲜袋中,置于(14±1.0)℃恒温库中贮藏,每5 d测定各项生理生化指标。结果:与对照组相比较,3种不同处理均能对鲜切生姜起到不同程度的保鲜效果;均能抑制鲜切生姜的褐变;减缓VC含量的下降,抑制营养物质的损失;减少丙二醛的积累;抑制微生物生长;维持良好的硬度、弹性、咀嚼性,抑制生姜质构品质的下降。同时,CTS与AOB复合处理能够有效抑制鲜切生姜细胞内含物的破坏及质壁分离现象的发生。结论:在研究的3种不同处理方式中0.3%AOB+1.5%CTS处理效果最为明显,其次是1.5%CTS处理组,0.3%AOB处理组的保鲜效果不显著。