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2019 Volume 41 Issue 12
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Xiao-lian LI, Wei LI, Jiu-yan LI, et al. Analysis of Quality Characteristics of Camellia nanchuanica During Primary Processing of Black Tea[J]. Journal of Southwest University Natural Science Edition, 2019, 41(12): 15-23. doi: 10.13718/j.cnki.xdzk.2019.12.003
Citation: Xiao-lian LI, Wei LI, Jiu-yan LI, et al. Analysis of Quality Characteristics of Camellia nanchuanica During Primary Processing of Black Tea[J]. Journal of Southwest University Natural Science Edition, 2019, 41(12): 15-23. doi: 10.13718/j.cnki.xdzk.2019.12.003
shu

Analysis of Quality Characteristics of Camellia nanchuanica During Primary Processing of Black Tea

  • 1.

    School of Food Science, Southwest University, Chongqing 400715, China

  • 2.

    Economic Crops Center of Agricultural Commission of Nanchuan District, Nanchuan Chongqing 408400, China

  • 3.

    Ancient Tree Tea Research Institute, Chongqing 400013, China

More Information
  • Received Date: 18/12/2018
    Available Online: 20/12/2019

  • MSC: TS272;S375

  • In this experiment, Camellia nanchuanica with a bud and two leaves, was used as the material to process orthodox black tea. The changes of each major quality component during processing were studied. With C. sinensis var. assamica in Yunnan as the CK, the adaptability of processing and variety characteristics of C. nanchuanica were evaluated. The results showed that during the processing of black tea, the total amount of water extracts and tea polyphenols decreased gradually; the total amount of catechins was greatly reduced; of the 8 catechins studied, the contents of 7 decreased significantly, with the exception of gallocatechin gallate (GCG), and the content of gallic acid(GA)increased significantly. The total amount of theaflavins and the four monomers:theaflavin (TF), theaflavin-3-gallate (TF-3-G), theaflavin-3'-gallat (TF-3'-G) and theaflavin digallat (TFDG) increased sharply after rolling, only TFDG continued to increase in the subsequent processes, and it was always the component with the highest content. The content of thearubigin increased first and then decreased, while the tea brown pigment was steadily accumulated throughout processing. The total amount of free amino acids increased during processing, reaching a maximum of 36.34 mg/g in raw black tea. Theanine, aspartic acid and glutamic acid had higher content. The content of theanine and glutamic were decreased with the processing, Aspartic acid, asparagine, and glutamine increased. Most amino acids increased significantly after withering, and all amino acids increased from the end of fermentation to drying. The sensory evaluation showed that after 80 minutes' fermentation the taste of the product was the best, sweet and mellow and refreshing. The primary tea of C. nanchuanica had the highest comprehensive score, its knot being tight and the soup being orange and bright in color, sweet and refreshing in taste, and sweet and fragrant in smell. Compared with the black tea, the fermentation time is shorter in 80 minutes, which is beneficial to processing. Comparatively, the soup color of CK was better, but its aroma was not as good as C. nanchuanica black tea, which was better in overall quality.
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Analysis of Quality Characteristics of Camellia nanchuanica During Primary Processing of Black Tea

  • Received Date: 18/12/2018
  • Available Online: 20/12/2019

Abstract: In this experiment, Camellia nanchuanica with a bud and two leaves, was used as the material to process orthodox black tea. The changes of each major quality component during processing were studied. With C. sinensis var. assamica in Yunnan as the CK, the adaptability of processing and variety characteristics of C. nanchuanica were evaluated. The results showed that during the processing of black tea, the total amount of water extracts and tea polyphenols decreased gradually; the total amount of catechins was greatly reduced; of the 8 catechins studied, the contents of 7 decreased significantly, with the exception of gallocatechin gallate (GCG), and the content of gallic acid(GA)increased significantly. The total amount of theaflavins and the four monomers:theaflavin (TF), theaflavin-3-gallate (TF-3-G), theaflavin-3'-gallat (TF-3'-G) and theaflavin digallat (TFDG) increased sharply after rolling, only TFDG continued to increase in the subsequent processes, and it was always the component with the highest content. The content of thearubigin increased first and then decreased, while the tea brown pigment was steadily accumulated throughout processing. The total amount of free amino acids increased during processing, reaching a maximum of 36.34 mg/g in raw black tea. Theanine, aspartic acid and glutamic acid had higher content. The content of theanine and glutamic were decreased with the processing, Aspartic acid, asparagine, and glutamine increased. Most amino acids increased significantly after withering, and all amino acids increased from the end of fermentation to drying. The sensory evaluation showed that after 80 minutes' fermentation the taste of the product was the best, sweet and mellow and refreshing. The primary tea of C. nanchuanica had the highest comprehensive score, its knot being tight and the soup being orange and bright in color, sweet and refreshing in taste, and sweet and fragrant in smell. Compared with the black tea, the fermentation time is shorter in 80 minutes, which is beneficial to processing. Comparatively, the soup color of CK was better, but its aroma was not as good as C. nanchuanica black tea, which was better in overall quality.

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  • 南川大树茶是重庆地区的一种独特的地方品种资源，具有明显的原始特征[1]，叶片大，节间长，角质层较厚，芽叶肥壮，且比当地多数中小叶种发芽早[2]，有较高的开发利用价值. 2012年，“南川大树茶”获得了地理标志认证和地理标志证明商标，目前在南川区德隆乡茶树村已经形成了“南川大树茶扦插繁育、生产技术”等技术规范，大树茶仿原生态栽培技术初获成功[3].有关研究表明[4]，南川大树茶属大叶种，儿茶素质量分数丰富，咖啡碱质量分数较高，推测南川大树茶适制红碎茶，滋味较好.

    工夫红茶是中国特有的茶类，也是世界最早的红茶花色，是重要的出口茶类[5].近年来，红茶的消费量逐渐增长，传统工夫红茶的生产得以恢复，生产规模逐年扩大，引起茶叶界的重视.目前，关于工夫红茶适制品种以及加工过程的研究报道很多，但南川大树茶作为特殊的地方资源，关于其加工的研究却鲜有报道.因此本实验以南川大树茶1芽2叶为原料，加工工夫红茶，研究分析加工过程中感官品质、主要品质成分的变化规律，与当地栽培品种云南大叶种比较，分析两种茶的差异，挖掘南川大树茶的品质特色，并为确定大树红茶的最佳工艺参数提供一定的理论依据，促进大树红茶的生产加工利用.

1.   材料与方法

    1.1.   实验材料

  • 2018年4月18日，大树茶采于南川市德隆乡南川大树茶示范基地，云南大叶种采于南川香炉寺山庄茶园，均为1芽2叶.

    • 1.2.   实验方法

    1.2.1.   加工工艺

  • 加工工艺流程按照鲜叶—萎凋—揉捻—发酵—干燥—毛茶，具体如下：

    1) 萎凋温度：20 ℃~25 ℃，湿度：65%~75%，时长16 h，萎凋至含水量60%.采用型揉捻机，总揉70 min；发酵温度：26 ℃~28 ℃，湿度：85%以上，发酵200 min.将发酵叶投入热风杀青机2 min，至含水量30%左右.

    2) 烘干机中100 ℃烘至足干.

    • 1.2.2.   取样固样

  • 采用微波杀青固样方式：微波高火1 min+1 min固定，然后80 ℃烘至足干.南川大树茶在每个工序分别取样，即鲜叶(dsc-1)，萎凋叶(dsc-2)，揉捻叶(dsc-3)，发酵40 min(dsc-4)，发酵80 min(dsc-5)，发酵120 min(dsc-6)，发酵160 min(dsc-7)，发酵200 min(dsc-8)，毛茶(dsc-9)；云南大叶种毛茶样(CK).

    • 1.2.3.   感官审评

  • 按照GB/T 23776-2009《茶叶感官审评方法》[6].

    • 1.2.4.   水分、水浸出物、茶多酚、茶色素的测定

  • 按照GB/T8303-2013《茶磨碎试样的制备及其干物质含量测定》[7]，GB/T 8305-2013《茶水浸出物测定》[8]，GB/T 8305-2008《茶叶中茶多酚和儿茶素类含量的检测方法》[9]进行测定，茶红素、茶褐素的测定采用系统分析方法[10].

    • 1.2.5.   儿茶素、没食子酸、咖啡碱、茶黄素组分的测定

  • 1) 标准曲线绘制：分别准确称取8种儿茶素组分、没食子酸、咖啡碱、茶黄素等标品各20 mg，用50%甲醇溶解，定容至25 mL容量瓶，得标准母液.吸取一定量的单标配制成混标，并稀释至不同梯度，分别进样分析，以峰面积为纵坐标，样品浓度为横坐标，绘制标准曲线.

    2) 样品制备：参照GB/T 8305-2008《茶叶中茶多酚和儿茶素类含量的检测方法》[9].

    液相色谱仪：赛默飞UltiMate3000，色谱条件：Ascentis © RP-Amide柱(5 μm，25 cm×4.6 mm)，流动相A：体积分数为2‰的冰乙酸；流动相B：纯乙腈；检测波长：278 nm；温度：35 ℃；进样量：5 μL；流速：1 mL/min(表 1).

    • 1.2.6.   氨基酸组分的测定

  • 1) 标准曲线绘制：分别准确称取21种氨基酸标品各50 mg，用0.1 mol/L盐酸溶液溶解，定容至25 mL容量瓶，得标准母液.分别取100 μL配制成混标，稀释至不同梯度，取40 μL进行衍生，进样分析，以峰面积为纵坐标，样品浓度为横坐标，绘制标准曲线.

    2) 样品制备：参照GB/T 8314-2013《茶游离氨基酸总量的测定》.

    3) 氨基酸的衍生[11]：取200 μL茶汤，200 μL 2，4-二硝基氟苯溶液，200 μL Na2CO3-NaHCO3缓冲液(pH值为9.16)，200 μL超纯水于2 mL离心管中，60 ℃暗水浴1 h，冷却至室温后加入800 μL KH2PO4-NaOH缓冲液(pH值为7.0)，涡旋1 min，暗条件放置15 min，过0.22 μm水系膜，进样分析.

    液相色谱仪：赛默飞UltiMate3000；检测条件：色谱柱AQ12S05-1546WT YMC-Pack ODS-AQ(5 μm，150×4.6 mm)，流动相A：4 mmol/L乙酸钠溶液与四氢呋喃比例为96:4；流动相B：体积分数为80%的乙腈；检测波长：360 nm；温度：35 ℃；进样量：10 μL；流速：0.9 mL/min(表 2).

    • 1.2.7.   统计分析

  • 利用Excel，SPSS 18.0软件等进行单因素方差等分析.

2.   结果与分析

    2.1.   南川大树茶红茶加工过程感官品质变化

  • 将揉捻叶及之后各个工序的在制品进行感官审评，研究其品质变化.从表 3可知，随着加工的进行，青气逐渐减退，至发酵80 min(dsc-5)时开始透发出甜香、花果香，其中发酵结束时香气最好；汤色逐渐加深变为橙黄；各种内含物质转化，滋味慢慢变得甜醇，发酵80 min时滋味最佳，随着发酵时间的延长，茶汤逐渐带酸.相较之下，云南大叶种(CK)汤色更优，但香气不如大树茶，大树茶整体品质更优.

    • 2.2.   主要品质成分在红茶加工中的变化

  • 鲜叶(dsc-1)中水浸出物质量分数高达50.80%，发酵后降至最低值，烘干后又显著增加.鲜叶中茶多酚质量分数为22.50%，在加工中持续减少，毛茶(dsc-9)中保留量为14.18%，较鲜叶减少了36.98%.咖啡碱对大树茶红茶汤的鲜爽味有重要影响，从鲜叶到发酵初阶段，咖啡碱质量分数减少，发酵120 min(dsc-6)时降至最低，发酵结束(dsc-8)时达最大值5.16%，毛茶对比发酵叶和鲜叶质量分数差异有统计学意义(p＜0.05).相较于云南大叶种，大树茶红茶水浸出物、茶多酚及咖啡碱质量分数更丰富.

    萎凋叶经过揉捻，儿茶素即开始氧化，茶黄素、茶红素开始形成，在揉捻结束时，茶黄素质量分数已达到0.71%，在发酵初期继续增加，在后续发酵和干燥过程中变化幅度较小.茶红素在揉捻、发酵初期持续增加，发酵40 min(dsc-4)达到最大值5.15%，随后降低；而茶褐素质量分数在整个加工中持续增加，但是，总质量分数并不太高(表 4).相较之下，云南大叶种茶色素质量分数更高，但南川大树茶的茶黄素也明显高于国内川红、祁红等品种[12]，甚至高于某些国外的红茶[13].

    • 2.3.   儿茶素组分及没食子酸(GA)在加工中的变化

  • 鲜叶中GA质量分数只有0.43 mg/g，萎凋过程中由于酯型儿茶素降解生成GA[14]，因此质量分数显著增多，揉捻后达最大值4.00 mg/g，而后的工序中，由于GA氧化形成邻醌，与儿茶素类反应生成茶黄棓灵(theagallin)或茶黄酸[15]等，质量分数又逐步减少.

    大树茶鲜叶中儿茶素总量为207.2 mg/g，其中酯型儿茶素比例高达88.44%，显著高于大多数云南大叶种，包括群体种和无性系良种[16].儿茶素总量随着加工的进行，质量分数持续减少，毛茶中保留量仅为30.8 mg/g.除GCG外，其余儿茶素组分质量分数在加工中逐步减少. EGCG在鲜叶中质量分数高达152.51 mg/g，占儿茶素总量的72.80%，加工后毛茶中保留量为12.50 mg/g，是云南大叶种的3.87倍. EGC和ECG两者变化趋势相同，加工中持续减少，最后烘干过程中略有上升. GCG在加工中质量分数明显增多(p＜0.05)，主要由EGCG差向异构化而来[17-18]，发酵40 min(dsc-4)后达到最大值10.71 mg/g，毛茶中仍有8.04 mg/g，显著高于云南大叶种(表 5).日本学者坂本彬等[19]曾分析了来自4个国家的12个不同品种的红茶成分，发现大多数品种的EGCG保留量不足5.00 mg/g，而GCG均不足0.50 mg/g.相比之下，南川大树茶红茶中两者质量分数都很高，尤其是GCG，高于多数品种.

    • 2.4.   茶黄素组分在红茶加工中的变化

  • 总体来看，TFDG是质量分数最高的组分，其次为TF-3-G，TF质量分数最低.由图 1可知，从萎凋到揉捻结束，各组分质量分数都急剧增加. TF在揉捻(dsc-3)时达到峰值0.1%，之后有所降低，毛茶(dsc-9)中有0.08%. TF-3-G，TF-3'-G从萎凋到发酵40 min(dsc-4)时质量分数显著增加，此时TF-3-G达到峰值，随后降低；TF-3'-G在发酵结束(dsc-8)时达到最高值. TFDG从萎凋到发酵结束，质量分数持续积累，发酵结束时达到最大值0.49%.大树茶TFDG质量分数明显高于云南大叶种，其余3种质量分数均低于云南大叶种.

    Okinda等[20]证实TFDG与红茶品质呈极显著相关，不同茶黄素对红茶汤收敛性的贡献值不同[21].易晓芹等[22]分析了来自印度、斯里兰卡、肯尼亚等不同产地的15种红茶样茶黄素组分，发现TF-3-G质量分数均不足0.1%，TFDG质量分数也不高，相较之下，南川大树茶红茶中两者质量分数较为丰富，造就了红茶汤收敛性较强，滋味鲜爽的优良品质.

    • 2.5.   氨基酸组分在红茶加工中的变化

  • 游离氨基酸在加工中的变化见表 6.鲜叶经萎凋后，由于各种水解酶的作用，蛋白质、多肽等水解，因此绝大多数氨基酸质量分数有所增加，其中苯丙氨酸、天冬酰胺等升幅较大，尤其苯丙氨酸相比鲜叶增加了7.49倍，天冬酰胺增长了3.44倍；游离氨基酸总量从24.11 mg/g上升到35.03 mg/g，增加了45.29%，之后的工序中呈现先降后升趋势，毛茶中为36.34 mg/g，质量分数显著高于鲜叶.鲜叶中质量分数较高的有茶氨酸、谷氨酸、丝氨酸等，随着后续加工的进行，茶氨酸在叶片中持续分解为谷氨酸和乙胺[23-24]，因此质量分数降低；谷氨酸作为氨的转运站，可以进一步转化为重要的呈味氨基酸，质量分数也降低.脯氨酸、精氨酸等7种氨基酸在揉捻时质量分数有所增加，其余14种氨基酸均减少，此后的发酵过程有少量变化，但趋势较缓.发酵叶在烘干过程中，所有氨基酸质量分数均有增加，推测可能由于高温，蛋白质大量热水解，使得氨基酸质量分数增多[25].谷氨酸、茶氨酸、精氨酸、蛋氨酸这4种氨基酸在毛茶中的质量分数比鲜叶低，其余17种氨基酸在毛茶中的质量分数均显著高于鲜叶(p＜0.05).

    氨基酸在红茶加工中的变化较复杂，对红茶品质有重要影响[26].各氨酸经脱羧、脱水等生成了吡嗪类[27]、醛类[28]、吡咯类[29]等香气物质，使南川大树茶红茶透发出甜香和花果香.此外，氨基酸与多酚类氧化缩合形成的黑褐色物质[30]，造就干茶乌润的色泽.大树茶红茶中茶氨酸[31]、天冬氨酸、丝氨酸[32]等质量分数较高，这些呈味氨基酸造就了大树茶红茶汤鲜爽[33]、甜醇[34]的优良品质.茶氨酸质量分数稍低于云南大叶种，但游离氨基酸总量更丰富，滋味更鲜爽醇厚.

3.   讨论

  • 实验表明，南川大树茶鲜叶中儿茶素质量分数极丰富，且酯型儿茶素比例大，咖啡碱质量分数也较高，酚氨比大于8，且毛茶中茶黄素质量分数较高，氨基酸质量分数高，表明此品种适制红茶.在南川大树茶红茶加工中，水浸出物质量分数逐步减少，但毛茶中质量分数依然丰富，明显高于云南大叶种，符合优质红茶的标准.茶多酚和儿茶素类在加工中质量分数大幅减少，GA，GCG质量分数在加工中显著增加；TFDG在加工中整体呈上升趋势，是质量分数最高的组分，其次为TF-3-G；茶黄素总量呈上升—下降—上升趋势，茶红素质量分数先增多后减少，茶褐素持续积累，成茶中茶色素质量分数低于云南大叶种，游离氨基酸在加工中质量分数显著增加，质量分数较云南大叶种更高.云南大叶种汤色红亮，但香气、滋味等欠佳，大树茶红茶整体品质更优.

    从南川大树茶鲜叶分析结果可看出，南川大树茶具明显的品种特征，鲜叶中EGCG质量分数极高，明显高于云南大叶种[35]、祁门种[36]、福鼎大白茶[4]、茗科一号[37]、四川中小叶种[38]等，在红茶加工过程中，高质量分数的EGCG分别与EC，ECG偶联氧化形成TF-3-G和TFDG，因此，毛茶中TF-3-G和TFDG的质量分数虽低于云南大叶种，但也较大多品种高.此外，EGCG转化形成大量的GCG，GCG也是红茶中的一种功能性成分，可减少血浆中的胆固醇，对脂质过氧化抑制能力很强，具有抗氧化活性，在某一特定条件下，清除自由基的能力甚至高于EGCG[39].

    在后续的工艺优化过程中，可以通过对发酵叶的发酵温度、供氧状态、pH等因素加以调控和优化，抑制EGCG异构化为GCG，进一步促进茶黄素的形成，充分发挥南川大树茶的品种特性，提高产品品质.

Figure (1)  Table (6) Reference (39)

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