普洱茶后发酵过程中微生物的研究进展

对有关普洱茶后发酵生产与微生物的关系、微生物的种类、微生物对普洱茶品质的影响以及主要微生物的生长特性等方面的研究工作进行综述。指出加强普洱茶后发酵过程中微生物基础研究的必要性,提出建立普洱茶后发酵菌物库,重视对影响普洱茶品质的菌物开展系统研究的建议。     

普洱茶渥堆发酵与堆肥渥堆发酵的比较研究

普洱茶的自然渥堆发酵工艺与农业及环保中的堆肥发酵工艺在堆垛方法、堆垛形状和大小、自然升温过程、高温发酵、翻堆工艺等方面有许多相似之处,主要差别是原料和含水量的不同。对不同原料堆肥已有详细的研究及其动态菌群和多种发酵剂的研究和应用报道,明确了高温菌在渥堆发酵过程中起重要作用,对其翻堆工艺也有较详细的参数及其机械化的应用,但普洱茶渥堆发酵基本上还停留在自然发酵、人工翻堆、常温菌的研究及老茶头作发酵剂的应用等水平上。堆肥的许多研究手段和方法甚至物质转化、脱毒、高温菌的研究等都值得普洱茶渥堆发酵研究加以借鉴。     

普洱茶后发酵中咖啡碱变化研究进展(综述)

普洱茶（熟茶）的后发酵加工工艺,是形成其独特品质特征的关键工序。咖啡碱是一种甲基黄嘌呤,是茶叶中含量比较丰富的生化成分之一,也是茶叶主要呈味物质和生理活性成分,具有促进兴奋、强心、解毒、利尿、助消化等功效。咖啡碱在普洱茶后发酵过程中呈增加趋势。文章对普洱茶后发酵过程中咖啡碱变化的相关研究进行系统综述,为普洱茶咖啡碱理论研究提供科学依据。     

普洱熟茶后发酵加工过程中曲霉菌的分离和鉴定

从云南省易武、基诺山、普洱和昆明后发酵加工生产的普洱熟茶堆中分离到7种曲霉菌,分别鉴定为：温特曲霉烟色变种,帚状曲霉,具黄曲霉,埃及曲霉,臭曲霉,日本曲霉原变种,以及局限灰曲霉。发现不同产地普洱熟茶中曲霉菌菌群的组成存在差异,对曲霉菌在普洱熟茶生产中的作用与意义进行了初步的讨论。     

一种改进的普洱茶固态发酵过程微生物DNA提取方法

为开发一种改进的普洱茶固态发酵过程微生物DNA提取方法,首先配制含有吐温-20、聚乙烯吡咯烷酮(PVP)、乙二胺四乙酸二钠(Na2EDTA)等组分的洗涤缓冲液,引入超声波振荡、涡旋、65℃水浴、反复洗涤等手段,把普洱茶发酵微生物较高质量的收集起来,再使用十六烷基三甲基溴化铵(CTAB)法提取微生物总DNA。按照本文所述方法所得到的菌体沉淀接近白色,后续提取出的DNA总量高、色度低、杂质少,适用于PCR及基因组学等研究。     

普洱茶中功能性微生物的筛选及其对普洱茶感官品质的影响

普洱茶的渥堆发酵过程是以晒青毛茶的内含成分为基础,在微生物分泌的胞外酶及湿热作用下,发生一系列化学变化,最终形成普洱茶独特的风味。采用稀释涂布法,根据产酶微生物的特性,经过固体平板初筛和液体茶汤培养基复筛,从普洱茶中分离得到若干株产酶菌株,并从中挑选优良菌株接种普洱茶固体发酵,考察其对普洱茶感官品质的影响。经分子生物学鉴定,D13-16为米曲霉(Aspergillus oryzae),相似度为98.62%;GJ-02为米根霉(Rhizopus cryzae),相似度为98.57%;XW-10和DF-03均为黑曲霉(Aspergillus niger),相似度分别为99.10%和99.92%。结果表明:普洱茶香气的形成主要与蛋白酶产生菌有关,DB-16发酵后香气评分达到31分(对照28,总分40);汤色主要受多酚氧化酶产生菌的影响,DF-03发酵后汤色评分达到19分(对照12,总分20);而这四种功能性微生物均在不同程度上促进了普洱茶滋味的形成。     

普洱熟茶化学成分的HPLC-DAD-MS分析

普洱熟茶以其特殊的香气、口感和保健功效,近年来受到愈来愈多消费者的喜爱,是最受欢迎的茶叶品种之一.普洱熟茶由普洱生茶经特殊的微生物后发酵过程生产而成,而普洱生茶则以大叶茶的鲜叶为原料,是一种不发酵的绿茶.本文采用HPLC-DAD-MS技术,对普洱熟茶的化学成分进行了分析,从中共检测出21个峰;通过[M+H]+、[M-H]和碎片离子峰,以及与标准品对比,其中18个峰的化学结构分别得到了鉴定.研究结果显示,去除了大量存在的咖啡因后,HPLC-DAD-MS技术可以用于快速有效地检测普洱熟茶中的化学成分.     

60Co γ辐照对普洱茶杀菌效果及其品质的影响

以普洱茶为研究对象,利用60Co γ射线辐照,初步研究了不同辐照剂量对普洱茶的杀菌效果及其品质的影响。结果表明:60Co γ射线能有效地杀灭普洱茶中的微生物,产品初始细菌和霉菌的数量均低于105cfu/g,经3.6kGy~5kGy剂量辐照能确保普洱茶中污染微生物的量低于1×103cfu/g,而且对普洱茶主要品质成份无明显影响。     

普洱茶市场的困惑链

<正>不说全国,就是昆明的茶叶市场里也很少见到真正的古树茶,产自芒景的就更少了。茶商们给外行拿出的所谓古树茶全是假的,要价还挺高,即使是那些一两千元一公斤的所谓‘真茶'中最好的,真货也不过七八成。在盛产优质古树茶的云南芒景村,我们多次从村民口中听到这样的说法。     

贮藏条件对普洱茶品质成分的影响研究

将云南普洱茶放在不同的温度、水份和时间等条件下,观察外界的不同条件对普洱茶品质成分的影响。观察结果显示:水份和温度对普洱茶贮藏的品质成分影响最为显著,在相同的贮藏时间内,提升温度以及增加水份的含量,普洱茶的茶褐素会增加,出现变色,内含的成分会有所下降,如茶多酚和儿茶素等。经过实验证明,高温、低水分是普洱茶贮藏的较好条件,能够保持茶叶色泽和香味;而低温和高水份含量则会加速普洱茶的发霉。     

茶儿茶素抑制肿瘤血管生成的作用

对近几年茶儿茶素抑制肿瘤血管生成的研究进展进行了综述。从抑制血管内皮细胞生长、抑制细胞黏附分子表达和抑制基底膜降解三个部分讨论了其抗肿瘤血管生成的机制,并对儿茶素研究存在的问题和儿茶素开发前景进行了探讨。     

Phenolic Compounds and Allelopathic Potential of Fermented and Unfermented Wheat and Corn Straw Extracts

Total phenolic (TPC) and flavonoid (TFC) content, individual phenolic compounds and antioxidant activities of methanol extracts of wheat and corn straw were determined. Germination bioassay was conducted with Abutilon theophrasti Medik. , Asclepias syriaca L., and Chenopodium album L. seed. Samples were fermented by Lactobacillus plantarum and changes in TPC, TFC, antioxidant, and biological activity were investigated. TPC and TFC were significant in both samples and after fermentation their recovery was improved. All samples contain mainly quercetin, cinnamic acid, p‐coumaric acid, and ferulic acid. Fermentation changed the content of phenolic and flavonoid compounds, differently in each case. All tested extracts showed high DPPH activity with IC₅₀ being significantly lower for fermented samples. FRAP activity was also high. Crude straw extracts were overall more effective than fermented ones concerning inhibition of germination and seedlings growth, mainly without statistically significant differences between wheat and corn. Compared with mesotrione, extracts were more effective in germination and seedling growth inhibition of C. album and in seedling growth inhibition of A. theophrasti.     

Utilization of Unfermented Cassava Flour for the Production of an Indigenous African Fermented Food, Agbelima

Summary Unfermented cassava flour, also called high quality cassava flour (HQCF) is used as a partial substitute for wheat flour in the baking industry. This work was carried out to produce an indigenous fermented cassava dough, agbelima, from high quality cassava flour in order to diversify uses for the flour. An isolate of each of the dominant species of lactic acid bacteria isolated from agbelima, was used to ferment reconstituted HQCF dough into agbelima, whilst pH changes, population on MRS, and the organoleptic quality were assessed. The antimicrobial properties of the fermenting samples against three enteric pathogens were also investigated. Lactobacillus plantarum, Lactobacillus brevis, Lactobacillus fermentum and Leuconostoc mesenteroides were isolated at levels of 10¹⁰, 10⁹, 10⁹ and 10⁸ c.f.u. g⁻¹ respectively in agbelima. All isolates and a control sample, produced agbelima with pH of between 4.11 and 3.82 in 48 h, and ANOVA showed no significant difference between the pH of the samples at P ≤ 0.05. Spontaneous fermentation of the reconstituted dough was possible, because the flour was found to contain Lactobacillus plantarum at a level of 10⁶ c.f.u. g⁻¹ as well as the other species isolated from agbelima. Counts of Gram-positive catalase-negative rods and cocci on MRS in all the fermented samples were at levels of 10⁸ to 10⁹ c.f.u. g⁻¹, with ANOVA showing no significant difference between the populations at P ≤ 0.05. Three enteric pathogens, Salmonella typhimurium 9, Echerichia coli D2188 and Vibrio cholerae C-230, inoculated into the samples at 10⁶ to 10⁷ c.f.u. g⁻¹ at the start of fermentation, could not be detected in 10 g of any of the samples at the end of 48 h fermentation. A taste panel preferred banku - a stiff porridge made from a combination of fermented maize dough and fermented cassava dough – prepared with fermented HQCF dough to banku prepared with a market sample of agbelima or reconstituted agbelima flour. Processing the highly perishable cassava roots into high quality cassava flour, therefore, offers a means for preserving cassava, which can subsequently be used for both industrial and traditional purposes.     

Influence of Fungal Fermentation on the Development of Volatile Compounds in the Puer Tea Manufacturing Process

Puer tea is a unique Chinese fermented tea with natural flora manufactured in Yunnan Province of China. Very complex changes take place to form special quality and flavor characteristics in Puer tea due to the coordination of microbial metabolic action and natural oxidation. This paper investigates the isolation and identification of fungi responsible for the fermentation and the development of main volatile compounds of Puer tea during the fermentation process by means of GC/MS. Aldehydes and ketones in parched green tea (raw material) with low boiling‐points decreased significantly, while the amount of terpene alcohols – such as linalool and linalool oxides, methoxybenzene and derivatives, and indole – increased remarkably from the parched green tea to the Puer tea product after the manufacturing process. Degradation caused by heat and microbial growth at the piling stage likely played a key role in the generation of these compounds that contributed to the aromatic characteristics of Puer tea. It is hypothesized that the fungus Aspergillus niger plays a decisive role in the development of the volatile compounds.     

Effects of Unfermented and Fermented Whole Grain Rye Crisp Breads Served as Part of a Standardized Breakfast,on Appetite and Postprandial Glucose and Insulin Responses: A Randomized Cross-over Trial

Background

Whole grain rye products have been shown to increase satiety and elicit lower postprandial insulin response without a corresponding change in glucose response compared with soft refined wheat bread. The underlying mechanisms for these effects have not been fully determined The primary aim of the study was to investigate if whole grain rye crisp bread compared to refined wheat crisp bread, elected beneficial effects on appetite and postprandial insulin response, similarly as for other rye products.

Methods

In a randomized cross-over trial, 23 healthy volunteers, aged 27-70 years, BMI 18-31.4 kg/m², were served a standardized breakfast with unfermented whole grain rye crisp bread (uRCB), fermented whole grain rye crisp bread (RCB) or refined wheat crisp bread (WCB), Appetite was measured using a visual analogue scale (VAS) until 4 h after breakfast. Postprandial glucose and insulin were measured at 0-230 min. Breads were chemically characterized including macronutrients, energy, dietary fiber components, and amino acid composition, and microstructure was characterized with light microscopy.

Results

Reported fullness was 16% higher (P<0.001), and hunger 11% and 12% lower (P<0.05) after ingestion of uRCB and RCB, respectively, compared with WCB. Postprandial glucose response did not differ significantly between treatments. Postprandial insulin was 10% lower (P<0.007) between 0-120 min but not significantly lower between 0-230 min for RCB compared with WCB. uRCB induced 13% (P<0.002) and 17% (P<0.001) lower postprandial insulin response between 0-230 min compared with RCB and WCB respectively.

Conclusion

Whole grain rye crisp bread induces higher satiety and lower insulin response compared with refined wheat crisp bread. Microstructural characteristics, dietary fiber content and composition are probable contributors to the increased satiety after ingestion of rye crisp breads. Higher insulin secretion after ingestion of RCB and WCB compared with uRCB may be due to differences in fiber content and composition, and higher availability of insulinogenic branched chain amino acids.

Trial Registration

ClinicalTrials.gov NCT02011217     

Chemical Composition and Sensory Evaluation of Fermented Tea with Medicinal Mushrooms

In commercial tea production, plenty of tea leaf waste is generated, which may not only exert pollution risk to environment, but also a huge waste of bioactive ingredients in tea. In this study, the 4th to 7th leaves of tea bush were collected and used as substrate for mycelial culture of two renown medicinal mushrooms Grifola frondosa and Tianzhi (new variants of Ganoderma lucidum) to obtain a new type of solid-state fermented tea. Result showed that the polysaccharides of Grifola frondosa and Tianzhi fermented tea were 1.52 and 4.14 %, tea polyphenols were 1.51 and 1.85 %, the free amino acids were 1.52 and 0.94 %, caffeine were 1.16 and 1.70 %, polyphenols/amid acids ratio were 1.0 and 1.98, water extractions were 35.53 and 32.86 %, protein contents were 17.63 and 6.13 mg/g, respectively. The volatile components were mainly composed of alcohols, esters, aldehydes and ketones. The contents of major flavor compositions of fermented tea had changed and their relation tended to be harmonious, and the variety of amino acids significantly increased. Therefore, the sensory flavor and therapeutic qualities of fermented tea were significantly improved.     

酸提高绿茶提取物对脂肪酸合酶的抑制活性

脂肪酸合酶和肥胖、癌症等人类重大疾病相关.获取高活性脂肪酸合酶抑制剂有重要应用价值.50％乙醇的绿茶提取物具有抑制脂肪酸合酶和经口服降低大、小鼠体重的功能.该提取物在酸的作用下可明显地提高其抑制脂肪酸合酶的能力.采用1 mol/L硫酸或盐酸在100℃下处理绿茶提取物,发现该提取物对脂肪酸合酶的抑制活性随时间逐步提高.在25℃至120℃温度下,提高处理温度使抑制活性提高的速度加快和程度加大. 用1 mol/L盐酸120℃处理35 min或3 mol/L盐酸100℃处理30 min可使绿茶提取物抑制脂肪酸合酶的半抑制浓度下降20倍左右,达到1 μg/ml以下.用pKa值4.76至1.27的1 mol/L浓度的4种有机酸在100℃作用150 min使绿茶提取物抑制活性分别提高到1.48至5.84倍.提高酸的浓度也使被作用的提取物的抑制活性提高的更多.表现抑制活性提高的速度及程度和氢离子浓度正相关.判断绿茶提取物在酸作用下抑制活性的提高来源于其中所含儿茶素在氢离子作用下发生了化学变化.初步实验表明其变化过程比较复杂,确定其分子机制还需进一步的研究工作.     

Inhibitory Effects of Methylcellulose on Cellulose Degradation by Ruminococcus flavefaciens

Highly methylated, long-chain celluloses strongly inhibited cellulose degradation by several species of cellulolytic bacteria of ruminal origin. Specifically, the inhibitory effects of methylcellulose on the growth of Ruminococcus flavefaciens FD1 were concentration dependent, with complete inhibition at 0.1% (wt/vol). However, methylcellulose did not inhibit growth on cellobiose or cellulooligosaccharides. Mixtures of methylated cellulooligosaccharides having an average degree of polymerization of 6.7 to 9.5 inhibited cellulose degradation, but those with an average degree of polymerization of 1.0 to 4.5 did not. Similar inhibitory effects by methylcellulose and, to a lesser extent, by methyl cellulooligosaccharides were observed on cellulase activity, as measured by hydrolysis of p-nitrophenyl-beta-d-cellobioside. R. flavefaciens cultures hydrolyzed cellulooligosaccharides to cellobiose and cellotriose as final end products. Cellopentaose and cellohexaose were cleaved to these end products, but cellotetraose was also formed from cellohexaose. Methylcellulose did not inhibit hydrolysis of cellulooligosaccharides. These data are consistent with the presence of separate cellulase (beta-1,4-glucanase) and cellulodextrinase activities in R. flavefaciens.     

光质及种子大小对普洱地区14种植物种子萌发的影响

以普洱地区14种常见植物种子为材料,在实验室条件下研究了其在白光、黑暗、红光和蓝光条件下的萌发特性,并分析了种子大小与萌发率、萌发速率、萌发开始时间的关系。结果表明:光质对四方蒿、沙针、尖子木、藿香蓟种子萌发率和萌发速率均有显著影响(P0.05)。光质对大叶斑鸠菊、云南山枇花、臭灵丹、车桑子、光萼猪屎豆、葫芦茶、云南地桃花、西南宿苞豆、岗柃、中国宿苞豆10个物种的种子萌发率和萌发速率均没有显著影响(P0.05),以上物种中除中国宿苞豆外,其他物种种子萌发率均在20%以下,处于休眠状态。四方蒿种子在白光(89.9%)和红光(84.7%)下萌发率最高,红光下种子萌发最快(4.93),蓝光下种子萌发开始时间最晚(11.3 d);沙针种子在白光下萌发率最高(80.4%)、萌发速率最快(2.71),在黑暗和蓝光下萌发率较低(43.9%和38%)、萌发速率最慢(0.73和0.85),白光、红光下萌发开始最早(11 d),黑暗条件下萌发开始最晚(21.7 d);尖子木种子萌发率在白光、黑暗、蓝光下均在86%以上,而红光下仅32%且萌发速率最慢(1.29),在蓝光下萌发开始时间最晚(13 d);藿香蓟种子萌发率和萌发速率在红光下最高(分别为71.3%和6.46),黑暗条件下最低(分别为42.5%和2.62);大叶斑鸠菊萌发开始时间在黑暗条件下最早(6 d),其次是白光下(7 d),蓝光和红光下较晚,分别为8 d和7.7 d。14个物种种子的萌发率与种子大小间均有显著负相关关系;种子萌发速率、萌发开始时间与种子大小间也有负相关关系,但不显著;种子大小与萌发率、萌发速率和萌发开始时间的关系不会随着光质的变化而发生变化。     

不同栽培模式对茶园生态环境及茶叶品质的影响

对陕南茶区的纯茶园、塑料大棚茶园、松茶间作茶园及林篱茶园4种常见栽培模式的茶园生态环境(包括小气候因子、土壤因子)和茶叶中各项生化指标(包括氨基酸、咖啡碱、茶多酚、酚氨比、茶水浸出物)进行了测定.结果表明:不同栽培模式茶园小气候因子有显著差异.相对于纯茶园,塑料大棚茶园、松茶间作茶园和林篱茶园能更有效地改善光照条件、降低环境温度、提高土壤水分和有机质含量、增强空气湿度,提高土壤养分状况.3种复合式茶园茶叶品质也较纯茶园显著提高,氨基酸和茶水浸出物含量显著高于纯茶园茶叶,而茶多酚含量却显著低于纯茶园茶叶.因此,林茶复合栽培模式和大棚模式茶园的生态环境更有利于茶树的生长和茶叶品质的提高.