微波对茶多酚浸出及其结构和组成的影响研究

该文以中、低档绿茶为原料,研究了微波对绿茶多酚类物质浸出及其结构和组成的影响,结果表明:以水为介质,微波处理绿茶有利于茶叶多酚类物质的浸出,平均粒径0.246mm的绿茶用料液比(W/V)1∶20,时间3min,微波处理2次,再50℃水浴浸提10min1次,茶多酚浸提率达90.73%,高于乙醇水浸提;HPLC分析结果显示,经微波处理制备的茶多酚制品主要含表没食子儿茶素(EGC)、表没食子儿茶素没食子酸酯(EGCG)和表儿茶素没食子酸酯(ECG)3种儿茶素。儿茶素总含量占茶多酚的78.4%,其中以EGCG含量最高,约占3种儿茶素总量的45.8%。与乙醇水溶液浸提法制备的茶多酚相比,其儿茶素组成略有变化,酯型儿茶素EGCG和ECG的含量略有减少,但其减少量远小于沸水提取法。紫外和红外光谱分析证实,微波对茶多酚制品的化学结构无影响     

不同种类茶叶冲泡前后中红外光谱变化探析

为建立一种快速无损评价茶叶/茶汤化学品质和色泽的方法,本试验选取7种代表性茶叶样本为材料,利用傅里叶变换中红外光谱(FTIR)技术,以开水冲泡方式制备茶汤冻干粉,对茶叶与茶汤共14个样本进行FTIR光谱采集分析。通过聚类分析、光谱曲线拟合、定性分析,并结合常规化学法检测茶多酚、茶多糖、可溶性糖、游离氨基酸、主要儿茶素类和生物碱含量。结果表明,不同茶叶光谱明显不同,由于茶叶加工工艺造成的脂类、儿茶素类、咖啡碱、游离氨基酸及叶绿素含量差异,利用1 800~1 170 cm^-1狭窄区域的光谱特征,可实现茶叶分类。茶叶与对应茶汤的光谱也存在明显差异,体现了茶叶在冲泡过程中的物质变化。主要特征峰区(位)为:2 925/2 855 cm^-1代表脂类饱和烃链-CH₂振动,1 700 cm^-1峰位对应儿茶素类和咖啡碱,1 534 cm^-1对应着叶绿素脱镁过程,1 551/1 556 cm^-1和1 500/1 497 cm^-1为叶绿素中亚甲基桥的伸缩振动,1 516/1 517 cm^-1为木质素中的苯环C=C伸缩振动。本研究为市场中茶叶、新型速溶茶粉样品化学品质检测提供了一种有效、快速的无损分析方法。     

不同氮肥种类和用量对川西蒙山茶品质的影响

利用盆栽试验研究了尿素、硫酸铵、硝酸铵、碳酸氢铵和硝酸钙5种氮肥和用量对川西蒙山茶品质的影响。结果表明:肥料种类、肥料用量以及肥料种类与用量的交互作用对茶叶主要品质指标(可溶性糖除外)的影响极显著;不论施用何种氮肥,茶叶中的茶多酚、儿茶素和咖啡碱含量都有极显著的增加;各种氮肥用量为4g/盆时,茶多酚、儿茶素和咖啡碱含量较高;与施用其他种类的氮肥相比,尿素能极显著地提高茶叶中儿茶素和氨基酸的含量。施用硝态氮将能显著提高茶叶中硝酸盐和亚硝酸盐的含量,但随着硝态氮用量的增加,硝酸盐和亚硝酸盐的含量没有显著变化,而铵态氮和酰胺态氮对茶叶硝酸盐和亚硝酸盐含量基本没有影响。综合考虑春夏秋三季茶叶的品质,若单施一种氮肥,尿素最为合适,施用量为8g/盆左右。     

基于通径分析法的土壤性质对茶叶品质的影响研究

为探究土壤性质对茶叶品质的影响程度,采用通径分析法研究了贵州省主要名优绿茶产地土壤性质对茶叶中水浸出物、茶多酚、儿茶素、咖啡碱的直接和间接效应。研究结果表明,土壤性质与茶叶品质之间的相关性不明显,土壤对茶叶品质影响程度表现为:咖啡因>儿茶素>水浸出物>茶多酚,决定系数分别为:0.854,0.830,0.787和0.705,剩余项系数分别为:0.382,0.412,0.462和0.543,土壤性质能表达影响茶叶品质众多因素中50%以上的信息。     

茶叶有效成分复合分离提取技术研究

以中、低档绿茶为原料,研究了茶多酚、咖啡碱和茶多糖的复合提取技术,探讨了微波对绿茶茶多酚类物质浸出特性的影响,建立了从同一茶叶原料中同时获得茶多酚、茶多糖、咖啡碱3种产品的工艺。研究结果表明:1)以水为介质,微波处理绿茶有利于茶叶有效成分的浸出,平均粒径0.246mm的绿茶用料液比(W/V)1∶20,时间3min,微波浸提2次,再50℃水浴浸提10min,1次,茶多酚浸提率达90.73%,高于乙醇水浸提。2)Al³⁺沉淀茶多酚的最佳pH范围为5.3～5.7;确定茶多酚——铝盐的最佳转溶条件为:茶多酚——铝盐沉淀用pH1.5的酸溶液,以料酸比1∶2(V/V)于60℃水浴中转溶15min,1次,茶多酚的转溶率达79.09%。3)萃取法结合升华法制备咖啡碱,较直接升华法得率高;确定咖啡碱最佳萃取条件为:供试液中NaCl浓度0.2%,二倍量的乙酸乙酯萃取3次,咖啡碱萃取率达95.14%。4)以水为介质,茶末经微波联合水浴浸提,溶剂法和沉淀法分离,能制备得率为11.8%的茶多酚、1.5%的茶多糖和1.2%的咖啡碱,效果明显优于单一溶剂法和沉淀法     

外源硒肥对茶叶硒含量及化学品质的影响研究

硒肥对提高茶叶品质和增加茶树体内硒含量具有明显的促进作用。为了探讨硒对茶叶品质的影响机制,本研究进行了土施和喷施硒肥的盆栽试验。结果表明:叶面喷施和土施Na2SeO3两种施用方式对茶叶硒含量的提高及品质的改善都非常有利。叶面喷施浓度为120μgSe/ml时,喷施后第12天,春茶的硒含量最高为0.374μg/g;叶面喷施浓度为180μgSe/ml时,喷施后第18天,夏茶和秋茶的硒含量最高,分别为0.380μg/g和0.368μg/g。采用土施硒肥的方法制富硒茶时,土壤施硒量应不少于8mgSe/盆。叶面喷施浓度为180μgSe/ml时,夏茶化学品质提高最为明显,其中酚氨比下降为对照的65.73%,可溶性糖含量增加到对照的116.30%。与叶面喷施有降低儿茶素含量的作用相比,土施硒肥对整个采摘期内茶叶儿茶素的含量无明显影响,因此对改善茶叶品质特别是春茶品质的作用后者优于前者。     

微波远红外耦合杀青工艺对绿茶品质的影响

为研究微波远红外耦合杀青工艺对绿茶品质的影响,试验分析了杀青时间、杀青功率和投叶量等因素对绿茶香气、滋味品质的影响,通过L9(34)正交试验设计,优化了绿茶微波远红外耦合杀青工艺,并与其他杀青方式进行了比较,结果表明：较佳的耦合杀青工艺为杀青功率微波10 kW +远红外6 kW,投叶量0.5 kg/min,杀青时间先微波1.5 min+后远红外1.5 min。此时杀青的茶叶香气滋味最好,感官品质总分达到91.40,茶多酚、儿茶素、咖啡碱、氨基酸、可溶性糖和芳香油质量分数分别达到17.24%、12.62%、3.10%、3.72%、4.64%、15.40×10-2 mg/g,香气滋味品质好于其他杀青方式,杀青时间是传统杀青的1/4～1/3,能耗成本是传统杀青的1/3～1/2。该杀青工艺克服了单纯使用微波杀青的不足,为绿茶加工生产提供参考。     

砖茶中氟的研究进展

综述了砖茶中氟含量情况、氟含量过高问题以及砖茶降氟措施等方面的研究,指出寻找安全的、对茶汤品质影响较小、降氟率较高及成本较低的降氟材料是降低砖茶氟含量的关键和突破方向。     

陕南茶园茶叶品质分析及重金属含量现状评估

为了解陕南茶园茶叶品质及茶园重金属含量现状,以茶叶主产区为研究对象,采集了8个县区330个茶园土壤样品,测定分析了pH值和铅(Pb)、锌(Zn)、铜(Cu)、铬(Cr)、汞(Hg)、砷(As)、镉(Cd)等7种重金属含量;同时测定分析了33个茶园茶叶品质及茶叶和浸出液中重金属含量。结果表明,茶叶中茶多酚平均含量为25.58%,儿茶素平均总量为20.74%,茶氨酸含量均值为2.45%,游离氨基酸总量均值为4.86%。茶叶中各重金属含量差异较大,Pb为0.04～2.65 mg/kg、Zn为34.82～55.38 mg/kg、Cu为3.18～20.16 mg/kg、Cr为0.09～4.89 mg/kg、Hg为0.02～0.30 mg/kg、As为0.66～1.16mg/kg和Cd为0.02～0.19mg/kg;32茶园茶叶符合《无公害食品茶叶》(NY5244—2004)和NY659—2003标准,33个茶园茶叶Cu含量符合有机茶标准。浸出液中仅检测出Zn、Cu和Cr,平均浸出率分别为:32.65%、24.96%和10.50%。土壤中重金属Pb、Zn、Cu、Cr、Hg、As和Cd的平均含量分别为10.03、87.61、16.42、12.38、0.20、6.89和0.11 mg/kg,综合潜在生态风险指数平均值为95.4,潜在生态风险较低。     

不同干燥工艺对莲子品质的影响

为深入了解不同干燥工艺对莲子干燥后品质的影响，该文以干燥后莲子的收缩率、复水率、抗性淀粉(RS)含量、色泽和组织结构为考察对象，研究了自然干燥、热风干燥、真空干燥、冷冻干燥、微波干燥和微波—热风联合干燥等6种不同干燥工艺对莲子品质的影响。结果表明：微波—热风联合干燥莲子的收缩率小，复水率高，RS含量低，色泽与莲子原始指标较接近，且能够较好地保持莲子的原始组织结构；微波干燥莲子的品质仅次于微波—热风联合干燥莲子；冷冻干燥莲子的收缩率和复水率均最佳，但RS含量高，色泽较莲子原始指标差，且组织结构发生了明显的变形和皱缩；自然干燥、热风干燥、真空干燥莲子的品质均较差。综合考虑，微波—热风联合干燥后的莲子除RS含量较低外，其他品质均较优，可作为最佳干燥方法应用于生产。     

Effects of heat processing and storage on flavanols and sensory qualities of green tea beverage

This research was conducted to understand the effects of heat processing and storage on flavanols and sensory qualities of green tea extract. Fresh tea leaves were processed into steamed and roasted green teas by commercial methods and then extracted with hot water (80 degrees C) at 1:160 ratio (tea leaves/water by weight). Green tea extracts were heat processed at 121 degrees C for 1 min and then stored at 50 degrees C to accelerate chemical reactions. Changes in flavanol composition and sensory qualities of green tea extracts during processing and storage were measured. Eight major flavanols (catechin, epicatechin, gallocatechin, epigallocatechin, epicatechin gallate, catechin gallate, epigallocatechin gallate, and gallocatechin gallate) were identified in the processed tea extract. Among them, epigallocatechin gallate and epigallocatechin appeared to play the key role in the changes of sensory qualities of processed green tea beverage. The steamed tea leaves produced a more desirable quality of processed green tea beverage than the roasted ones.     

微波提取法对樱桃、猕猴桃和枸杞多糖特性的影响

微波提取是近年来发展迅速的天然产物提取技术之一。为考察微波提取对多糖得率、结构及生物学功能的影响,论文采用微波功率1 000 W和提取温度140℃,以不同提取时间5,10 和20 min分别对樱桃、猕猴桃和枸杞中多糖进行提取。结果表明,微波提取多糖的得率、相对分子质量和抗氧化性低于传统提取方法,随着微波提取时间延长,多糖相对分子质量逐步降低,但多糖得率与抗氧化性无显著变化;微波提取得到的多糖在单糖组成上与传统提取方法有一定的差异。该研究结果对应用微波提取水果多糖条件的选择及多糖品质控制有一定的参考价值。     

超高压提取绿茶汁的初步研究

为研究超高压处理对提高绿茶汁品质的影响,分别以料液比为1︰15和1︰50的绿茶水为原材料,采用常温常压振摇（冷提）、水浴间隔振摇（热提）和超高压（100、300和500 MPa）3种处理方法提取绿茶汁,比较其品质化学成分,分析表明：以相同料液比比较,超高压提取的绿茶汁中游离氨基酸含量均高于冷提和热提,水溶性糖含量低于冷提和热提,茶多酚得率高于冷提。色差分析表明,超高压提取的绿茶汁黄绿色度比冷提和热提的更深。超高压提取对残留的多酚氧化酶和过氧化物酶活性均具有不同程度的钝化作用。     

杏鲍菇深加工残渣多糖酶法微波辅助提取工艺优化

为了研究杏鲍菇残渣中多糖的酶处理-微波辅助提取工艺及生物活性,该文以杏鲍菇深加工后的残渣为原料,在纤维素酶处理的基础上,微波辅助法提取杏鲍菇多糖;利用响应面试验设计对提取工艺条件进行优化,并与传统热水提取方法进行比较;对杏鲍菇多糖进行抗氧化和抑菌活性评价。结果表明,微波辅助提取杏鲍菇多糖的较佳条件为:水料比35∶1 m L/g,提取时间15 min,微波功率570 W,此条件下多糖的提取率为12.11%±1.02%,比热水提取高出41.21%,且提取时间缩短了105 min。杏鲍菇多糖对1,1-二苯基-2-三硝基苯肼自由基、羟基自由基和超氧阴离子自由基具有一定的清除作用,其半数抑制浓度(IC50)分别为22.9、19和21.1 mg/m L,对枯草芽孢杆菌、大肠杆菌和金黄色葡萄球菌具有较好的抑制作用,其最低抑制质量浓度分别为8、16和16 mg/m L,对黑曲霉和酿酒酵母没有明显的抑制作用。研究结果为进一步开发杏鲍菇多糖功能和利用杏鲍菇残渣提供一定的技术依据。     

不同杀青方法对绿茶品质的影响

杀青作业是提高绿茶加工品质的关键工序,为了提高茶叶加工品质,采用微波、热风、蒸汽、锅炒和蒸汽-热风组合等不同杀青方法对加工后绿茶的感官品质和茶叶内含成分品质特性进行了试验分析,结果表明：微波输出功率 10 kW、时间2.5 min、杀青叶温室75℃,杀青后茶叶的外形色泽、汤色、叶底表现较好,只有香气、滋味欠佳,咖啡碱、茶多酚、维生素C和叶绿素含量最高,分别是2.70%、34.40%、3.335×10-3 mg/g和2.24 mg/g,时间是传统杀青的1/4～1/3,能耗成本是传统杀青的1/3。蒸汽-热风组合杀青时间为6 min（蒸汽和热风各处理3 min）、叶温80℃杀青的茶叶香气最好,氨基酸保留量达到3.48%,感官品质总分达到90.75分。     

Countercurrent supercritical fluid extraction and fractionation of alcoholic beverages

A procedure for the recovery of aromatic extracts from distilled alcoholic beverages by means of a countercurrent supercritical fluid extraction (CC-SFE) on a pilot plant scale is studied. The beverage is directly in contact with the carbon dioxide current in a packed column, and the extracts are recovered in two different fractionation cells, where the depressurization occurs. The proposed method allows the selective extraction of aromatic components of the brandy flavor, rendering a high-value concentrated extract and a colored residue without brandy aroma. The content in ethanol of the aromatic extract can be modified by tuning the extraction/fractionation conditions, rendering from 15 to 95% recovery. The effect of the main variables, including extraction pressure and quality of extracting CO(2), has been tested.     

Effects of Vermicompost Tea (Aqueous Extract) on Pak Choi Yield,Quality, and on Soil Biological Properties

This study investigated the effects of vermicompost tea (aqueous extract) on yield and chemical quality of pak choi (Brassica rapa cv Bonsai, Chinensis group) grown in three media (two soils and a peat-perlite medium) under two fertilizer regimes (compost and synthetic fertilizer). The impacts of tea application on the chemical and biological properties of the growth media were also investigated. Vermicompost teas were prepared using various extraction methods (non-aerated, aerated, aerated with additives) with 1:10 (v:v) chicken manure-based vermicompost to water dilution and applied weekly at the rate of 200 mL plant^?1 for 4 weeks. Application of vermicompost tea increased plant production, total carotenoids and total glucosinolates in plant tissue. This effect was most prominent under compost fertilization. Total phenolic was lower in vermicompost tea treated plants compared to those treated with only mineral nutrient solution and the water control. Vermicompost tea improved mineral nutrient status of plants and media, and enhanced the biological activity of the media. Variability in yield and chemical quality of plants across treatments was explained largely by variability in tissue N uptake and dry matter accumulation. Dehydrogenase activity and soil respiration of vermicompost tea-treated growth media were approximately 50% higher than untreated media. This study confirmed that vermicompost tea can positively influence plant yield and quality and increase soil biological activity in multiple soil types.     

Influence of drying methods and agronomic variables on the chemical composition of mate tea leaves (Ilex paraguariensis A. St.-Hil) obtained from high-pressure CO2 extraction

The main objective of this work is to assess the influence of two drying methods (microwave and vacuum oven) and some agronomic variables (plant fertilization conditions and sunlight intensity) on the characteristics of mate tea (Ilex paraguariensis) leaves extracts obtained from high-pressure carbon dioxide extractions performed in the temperature range from 20 to 40 degrees C and from 100 to 250 bar. Samples of mate were collected in an experiment conducted under agronomic control at Ervateira Bar?o LTDA, Brazil. Chemical distribution of the extracts was evaluated by gas chromatography coupled with a mass spectrometer detector (GC/MS). In addition to extraction variables, results showed that both sample drying methods and agronomic conditions exert a pronounced influence on the extraction yield and on the chemical distribution of the extracts.     

马铃薯茎叶挥发性成分的两种提取方法比较

应用水蒸气蒸馏-溶剂萃取法和微波辅助-溶剂萃取法提取了成熟期马铃薯茎叶挥发性成分。用乙醚为萃取溶剂的水蒸气蒸馏法提取时,以0.533%（m/m）得油率获得精油;以正己烷为溶剂的微波辅助萃取法的最适提取条件为：温度60℃,时间9 min,液料比10︰1（V/m）,在此条件下的得油率为0.528%（m/m）。用GC-MS分析检测出水蒸气蒸馏法获得的精油含有81个成分,解析鉴定出占精油相对含量79.386%的43种物质,醇类化合物（24.789%）为主要成分;微波法获得的精油检测出78个成分,解析鉴定出占总精油82.226%的36种成分,酯类化合物（44.482%）为主要成分。2种提取方法获得的精油成分有很大的差别。