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中国精品科技期刊2020

基于多元统计方法的临沧市普洱生茶香气成分分析

马林龙, 罗正飞, 刘艳丽, 曹丹, 谢飞, 金孝芳

马林龙,罗正飞,刘艳丽,等. 基于多元统计方法的临沧市普洱生茶香气成分分析[J]. 食品工业科技,2023,44(20):331−337. doi: 10.13386/j.issn1002-0306.2022120209.
引用本文: 马林龙,罗正飞,刘艳丽,等. 基于多元统计方法的临沧市普洱生茶香气成分分析[J]. 食品工业科技,2023,44(20):331−337. doi: 10.13386/j.issn1002-0306.2022120209.
MA Linlong, LUO Zhengfei, LIU Yanli, et al. Analysis of Aroma Components of Raw Pu'er Tea in Lincang City Based on Multivariate Statistical Analysis[J]. Science and Technology of Food Industry, 2023, 44(20): 331−337. (in Chinese with English abstract). doi: 10.13386/j.issn1002-0306.2022120209.
Citation: MA Linlong, LUO Zhengfei, LIU Yanli, et al. Analysis of Aroma Components of Raw Pu'er Tea in Lincang City Based on Multivariate Statistical Analysis[J]. Science and Technology of Food Industry, 2023, 44(20): 331−337. (in Chinese with English abstract). doi: 10.13386/j.issn1002-0306.2022120209.

基于多元统计方法的临沧市普洱生茶香气成分分析

基金项目: 茶叶创新团队项目(2021-620-000-001-024);湖北省重点研发计划项目(2021BBA241);湖北省农业科技成果转化项目(2021ABC005、2023BBB162)。
详细信息
    作者简介:

    马林龙(1988−),男,硕士,助理研究员,研究方向:茶树种质资源与遗传育种研究,E-mail:malinlong@hbaas.com

    罗正飞(1982−),男,硕士,副教授,研究方向:茶叶加工研究,E-mail:luophy@126.com

    通讯作者:

    金孝芳(1982−),男,博士,副研究员,研究方向:茶树种质资源与遗传育种研究,E-mail:jxf1130@126.com

    +并列第一作者

  • 中图分类号: S571.1

Analysis of Aroma Components of Raw Pu'er Tea in Lincang City Based on Multivariate Statistical Analysis

  • 摘要: 为客观准确地评价临沧市普洱生茶的香气品质,本研究系统分析了16份临沧市普洱生茶的主要香气成分,并利用多元统计方法对其主要香气成分进行综合分析。结果表明:共检测到48个香气物质,平均含量大于2%的有11个;其中芳樟醇含量最高,平均含量为24.68%。在香气种类上,醇类物质占香气总量的比例最高,平均含量为46.55%;其次是醛类物质,平均含量为26.81%;酮类、酯类和其他类物质占香气总量的比例相对较小。多元统计方法分析表明:临沧市南、北部地区普洱生茶样品能够明显区分开,南部地区醇类、酯类物质含量相对较高,而北部地区醛类、酮类以及其他类物质含量相对较高,海拔高度可能是南、北部地区普洱生茶香气成分差异形成的重要原因;基于变量投影重要性(Variable important for the projection,VIP)大于1,筛选出23个香气成分或种类作为区分临沧市南、北部地区普洱生茶香气的重要标志物,其中芳樟醇、异佛尔酮、酮类、醇类、醛类、β-环柠檬醛、α-环柠檬醛、2,2,6-三甲基环己酮、橙花醇、β-紫罗兰酮的VIP值相对较大,对临沧市南、北部地区普洱生茶分类贡献较大。该研究为准确了解临沧市普洱生茶香气品质提供理论依据,也为临沧市普洱生茶品质、产地判定研究提供思路和方法。
    Abstract: In order to accurately evaluate the aroma quality of raw Pu'er tea in Lincang City, the aroma components of 16 raw Pu'er teas were systematically analyzed and comprehensively evaluated by multivariate statistical analysis. A total of 48 aroma components were detected, with 11 aroma components were more than 2.00% content. Among them, linalool was the most abundant component and the content was 24.68%. For the aroma types, the alcohols were accounted for the largest proportion with a mean of 46.55%, followed by aldehydes with a mean of 26.81%, while ketones, esters and other components were responsible for little proportion. Multivariate statistical analysis showed that the raw Pu'er teas obtained form in southern region were clearly distinguished from those in northern region. The concentration of alcohols and esters was significantly higher in southern region than those in northern region, whereas aldehyde, ketones and other components were remarkably lower. Altitude may be an important reason for the difference of aroma components of Pu'er raw tea in the south and north regions. Furthermore, 23 aroma components were identified based on variable importance in projection (VIP) score>1, which might be responsible for the discrimination of raw Pu'er teas in southern and northern region. Linalool, isoflolone, ketones, alcohols, aldehydes, β-cyclocitral, α-cyclocitral, 2,2,6-trimethyl-cyclohexanone, nerol and β-ionone play siginificant role in the differentiation of raw Pu'er tea harvested from different regions. This study would provide some theoretical basis for accurately understanding the aroma quality of Lincang Pu'er raw tea, and also provide ideas and methods for the study on the quality evaluation and origin determination of Lincang Pu'er raw tea.
  • 普洱茶是云南省特有的地方名茶,是以地理标志保护范围内的云南大叶种晒青毛茶为原料,经特定的加工工艺加工而成的,具有独特品质特征[12]。茶叶香气是评价茶叶品质优劣的重要指标[34],普洱茶产区多数地处高原山区,海拔、温度、地形地貌等变化大,不同产区普洱茶在香气品质上存在较大的差异[56]。因此,全面系统了解普洱茶各个产区普洱茶香气品质对普洱茶的产地判定、标准建立及加工过程品质调控等方面均有着积极意义。

    临沧市地处云南省西南部,是普洱茶原产地,有“天下普洱第一仓”的美誉,是普洱茶地理标志产品重要保护区域[78]。临沧市属怒山山脉的南延部分,系滇西纵谷区,纵向上总体呈上游山地、中游丘陵、下游平原的地形地貌。地势由东北向西南逐渐倾斜(海拔450~3429 m),通常海拔每升高100 m,年平均气温会降低0.5 ℃,昼夜温差也随着海拔升高而增加,垂直气候带谱明显。复杂的地形地貌和多样的立体气候使得临沧市境内普洱茶在香气品质上存在一定的差异,但目前关于临沧市普洱茶香气品质的研究较少且仅是选取了少数区域的样本,很难全面系统的反应临沧市普洱茶的香气品质特征[910]。因此,本研究通过对16份临沧市(七县一区)普洱生茶样品的主要香气成分含量进行比较分析,并利用主成分分析(Principal component analysis,PCA)、层次聚类分析(Hierarchical cluster analysis,HCA)和正交偏最小二乘判别分析(Orthogonal projections to latent structure-discriminant analysis,OPLS-DA)等多元统计方法对主要香气成分进行综合分析,以期客观准确地了解临沧市普洱生茶的香气品质,进而为临沧市普洱生茶品质、产地判定研究提供理论基础。

    当年普洱生茶样品 16份,均来自临沧市(七县一区),其中临翔区、凤庆县、云县、双江县、镇康县、永德县、沧源县、耿马县等县(区)各2份。生产时间为2018年5月,品种均为当地群体,鲜叶规格为一芽二三叶,种按普洱生茶工艺“采摘—摊放—杀青—揉捻—晒干—蒸压—干燥”加工而成,取样后立即放入−20 ℃冰箱贮藏,于2019年1月进行香气成分检测;癸酸乙酯(纯度99%) 美国Sigma-Aldrich公司。

    手动SPME进样器、50/30 μm DVB/CAR/PDMS固相微萃取头 美国Supeclo公司;7890A气相色谱仪、5975C质谱仪 美国Agilent公司;HHS型恒温水浴锅 上海博迅实业有限公司医疗设备厂;Milli-RO PLUS 30纯水机 法国Millipore公司。

    采用顶空固相微萃取法(head-space solid-phase micro-extraction,HS-SPME)对茶叶样品中的香气进行提取[11]。准确称取3.0 g茶样放入萃取瓶中,加入90.0 mL沸水,加入2.00 μL的内标(90 mg/L癸酸乙酯),然后将装有50/30 μm DVB/CAR/PDM萃取头(实验前需250 ℃老化15 min)SPME手持器通过瓶盖的橡皮垫插入到萃取瓶中,在50 ℃水浴中平衡10 min,吸附50 min后,取出并立即插入气相色谱仪的进样口中,240 ℃解吸附3 min,同时启动仪器收集数据。

    采用气相色谱-质谱联用技术(gas chromatography-mass spectrometry,GC-MS)对茶叶香气成分进行测定[11]。GC条件:安捷伦HB-5MS(30 m×0.32 mm,0.25 μm)弹性石英毛细管柱,进样口温度240 ℃,载气为高纯氦气,流速1.0 mL/min。柱温程序:50 ℃保持5 min,以3 ℃/min升至180 ℃保持2 min,然后以10 ℃/min升至250 ℃保持3 min。MS条件:电子电离能量为70 eV;质量扫描范围为50~600 amu;离子源温度为230 ℃;四极杆温度为150 ℃;质谱传输线温度为280 ℃。

    采用NIST11.L谱库对得到的质谱图进行串联检索和人工解析,质谱匹配度>80%作为物质鉴定标准[11]。香气组分釆用峰面积归一化法定量,组分峰面积除以总峰面积得到各香气物质组分的相对含量。利用WPS对试验数据的整理与分析,采用SIMCA-P 14.1软件进行PCA、HCA和OPLS-DA等多元统计分析。

    表1可知,釆用HS-SPME-GC-MS对16份普洱生茶的香气成分进行分析鉴定,共检测到48个主要香气成分,占顶空挥发物总量的90.72%~95.65%,包括醇类13种、醛类17种、酮类8种、酯类4种和其他类6种。在香气成分上,芳樟醇、1-辛烯-3-醇、顺-氧化芳樟醇、反-氧化芳樟醇、壬醛、己醛、β-环柠檬醛、2,2,6-三甲基环己酮、β-紫罗兰酮、异佛尔酮和柠檬烯等11个香气物质平均含量大于2%。在香气种类上,醇类物质占香气总量的比例最高,平均含量为46.55%;其次是醛类物质,平均含量为26.81%;酮类、酯类和其他类占香气总量的比例相对较小。

    表  1  临沧市普洱生茶香气成分(%)
    Table  1.  Aroma contents of raw Pu-er tea in Lincang City (%)
    序号香气成分凤庆
    县1
    凤庆
    县2
    云县1云县2永德
    县1
    永德
    县2
    临翔
    区1
    临翔
    区2
    镇康
    县1
    镇康
    县2
    耿马
    县1
    耿马
    县2
    沧源
    县1
    沧源
    县2
    双江
    县1
    双江
    县2
    均值
    1芳樟醇18.0717.4317.8518.2019.5819.5815.8217.957.9315.5244.1237.9643.9637.2827.1436.5324.68
    21-辛烯-3-醇5.004.9313.6414.737.2713.1013.8012.9211.389.225.636.555.407.136.376.028.94
    3顺-氧化芳樟醇3.212.993.313.833.574.094.444.584.653.702.753.402.803.173.123.263.55
    4反-氧化芳樟醇2.852.162.081.411.931.601.662.171.691.572.872.092.222.122.342.142.06
    5(2Z)-2-辛烯-1-醇0.991.062.273.021.632.782.873.132.671.671.151.510.911.391.221.241.84
    6橙花醇1.211.351.021.241.231.151.131.490.661.001.601.562.162.091.412.741.44
    7α-松油醇1.851.680.880.941.351.241.662.081.171.351.011.200.890.940.921.261.28
    82-乙基己醇1.241.050.640.511.571.070.910.772.172.311.020.950.520.600.930.571.05
    91-戊醇0.670.670.270.230.220.330.820.430.230.200.230.250.951.010.190.420.45
    102,2,6-三甲基-6-乙烯基
    四氢-2H-呋喃-3-醇
    0.670.470.450.450.520.430.310.340.560.450.340.390.340.350.360.300.42
    114-萜烯醇0.520.450.270.270.350.340.530.580.280.300.200.280.160.130.270.340.33
    12反1,2-环戊二醇0.320.250.300.290.280.320.300.210.450.380.220.250.150.130.240.150.27
    13环戊醇0.390.260.320.170.250.280.180.180.330.360.200.210.160.150.300.170.24
    14醇类合计36.9934.7543.3045.2939.7546.3144.4346.8334.1738.0361.3456.6060.6256.4944.8155.1446.55
    15壬醛8.7111.216.547.627.577.638.368.138.139.043.406.046.817.947.588.427.69
    16己醛4.283.9110.308.014.344.454.353.654.545.963.103.574.154.995.534.524.98
    17β-环柠檬醛3.923.822.442.563.962.542.882.614.093.132.012.111.061.202.722.052.69
    18庚醛1.681.892.302.132.151.462.142.261.402.001.351.551.952.051.951.951.89
    19癸醛1.552.321.041.451.431.881.471.501.972.020.741.311.241.601.551.471.53
    202-庚烯醛0.601.152.112.910.911.820.901.521.351.030.250.870.871.470.630.911.21
    212,3-二氢-2,2,6-
    三甲基苯甲醛
    1.421.450.930.991.571.281.191.211.411.801.061.060.440.500.950.831.13
    22反-2-癸烯醛1.000.700.981.181.171.011.111.071.300.990.670.670.840.951.020.650.96
    23苯乙醛1.502.101.161.360.621.070.480.431.340.550.450.720.280.470.820.780.88
    24正戊醛0.800.230.500.371.270.251.320.351.560.600.890.331.270.701.490.530.78
    252-甲基丁醛1.350.911.290.810.920.990.540.410.720.720.870.680.500.250.940.410.77
    26异戊醛0.610.690.730.560.580.630.370.341.170.620.460.480.320.190.470.230.53
    27α-环柠檬醛0.590.580.390.340.570.550.520.470.670.620.350.390.220.280.470.320.46
    283-羟基丁醛0.440.420.360.230.580.390.380.280.860.840.270.200.310.320.420.210.41
    292-已烯醛0.301.030.280.300.180.200.400.400.460.530.230.270.210.300.420.400.37
    30反-2-壬醛0.170.300.290.420.280.330.280.350.350.290.150.220.230.310.200.280.28
    31戊二醛0.380.190.330.230.280.240.180.210.280.260.310.320.230.140.300.190.25
    32醛类合计29.2732.9031.9731.4928.4026.7126.8825.1931.6331.0016.5720.8020.9323.6627.4724.1426.81
    332,2,6-三甲基环己酮3.653.322.932.913.382.993.233.005.663.052.121.980.971.122.771.892.81
    34β-紫罗兰酮4.003.741.601.643.692.212.232.142.833.341.112.120.620.661.991.592.22
    35异佛尔酮2.432.682.422.842.372.752.222.473.092.431.171.731.101.061.921.832.16
    366-甲基-5-庚烯-2-酮1.641.581.941.911.341.991.851.801.641.781.261.101.191.471.771.401.60
    37香叶基丙酮1.061.230.690.911.151.210.941.071.261.231.840.810.660.720.910.741.03
    38α-紫罗兰酮1.631.800.650.621.400.860.860.731.371.090.690.790.310.370.830.580.91
    392-庚酮0.430.400.590.520.540.640.620.630.740.820.430.500.340.450.360.420.53
    40反-3-辛烯-2-酮0.871.150.13
    41酮类合计14.8414.7511.6912.5013.8712.6511.9511.8416.5913.748.629.035.195.8510.558.4511.38
    42水杨酸甲酯0.941.510.650.991.191.461.461.940.861.081.451.941.692.330.971.501.37
    43二氢猕猴桃内酯1.061.060.600.630.730.540.580.630.760.630.560.500.560.740.720.650.68
    442-甲基戊酸甲酯0.110.110.070.050.160.090.090.070.170.150.090.080.050.050.130.090.10
    45异戊酸叶醇酯0.480.560.07
    46酯类合计2.122.671.311.672.082.102.122.641.791.852.102.532.783.691.832.242.22
    47柠檬烯2.802.121.721.642.372.132.973.483.362.742.672.381.742.103.772.292.52
    48二甲硫2.801.811.631.101.360.640.480.461.050.560.960.671.180.751.210.591.08
    49茶香螺烷0.921.230.730.861.251.051.471.741.111.360.790.780.570.700.900.791.02
    502-乙基吡咯0.630.550.940.630.850.680.990.920.901.030.630.610.490.560.720.530.73
    510.390.470.230.300.540.620.270.330.380.380.220.270.260.320.250.220.34
    52茶吡咯0.390.830.930.190.260.340.290.370.200.370.230.430.30
    53其他类合计7.937.016.184.726.635.466.477.307.006.445.505.144.244.436.854.425.98
    54总量91.1392.0694.4695.6590.7293.2391.8993.8191.1891.0894.1494.1093.7794.1091.5194.3892.95
    注:“−”表示未检出。
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    在醇类香气中,所测样品以具有铃兰花香并伴有木香的芳樟醇含量最为丰富,平均含量高达24.68%;其次是具有蘑菇、肉味的1-辛烯-3-醇,平均含量为8.94%;具有花香并伴有木香的顺-氧化芳樟醇、反-氧化芳樟醇含量也较为丰富。在醛类香气中,所测样品主要以大部分具有青味的低级脂肪醛为主,其中壬醛含量最高,平均含量为7.69%;其次是己醛,平均含量为4.98%;庚醛、癸醛以及β-环柠檬醛含量也相对较高。酮类、酯类以及其他类香气物质虽占香气总量比例相对较小,但对普洱生茶的香气形成同样有着关键作用[1213]。酮类化合物通常呈花果香,所测样品酮类香气以2,2,6-三甲基环己酮和β-紫罗兰酮含量最高,其次异佛尔酮含量也相对较高。另外,在云县2份普洱生茶样品中均检测出含量相对较高的反式-3-辛烯-2-酮,含量分别为0.87%、1.15%。在酯类香气中,以水杨酸甲酯、二氢猕猴桃内酯含量最为丰富,并在沧源县2份普洱生茶样品中检测到含量相对较高的异戊酸叶醇酯,含量分别为0.48%、0.56%。在其他类香气中,以具有柠檬味的柠檬烯含量最高,其次二甲硫、茶香螺烷含量也较为丰富,这些香气成分已在多篇文献中被证实是构成茶叶香气的重要物质[1415]。总体来看,临沧市普洱生茶的主要香气种类、组成与前人研究的云南普洱生茶结果相一致,以清香型的醇类、醛类香气物质为主,但不同产地样品在香气物质种类以及相对含量上存在一定的差异[2,16]

    基于临沧市16份普洱生茶香气成分、种类的含量,利用SIMCA-P 14.1软件进行PCA分析。由图1可知,沧源县、双江县、耿马县等临沧市南部地区与云县、凤庆县、永德县、临翔区、镇康县等临沧市北部地区的普洱生茶样品在PCA得分图中能够明显区分开,且南、北部地区的普洱生茶分别分布在PC1的正向、负向区间,说明临沧市南、北地区普洱生茶在主要香气成分上存在较大差异。结合主要香气成分PCA载荷图(图2)分析发现,醇类、酯类物质总量以及芳樟醇、反-氧化芳樟醇、橙花醇、水杨酸甲酯等平均含量较高的醇类、酯类物质在PC1上呈正向分布,而绝大多数的醛类、酮类以及其他类物质及其总量在PC1上呈负向分布。说明临沧市南部地区普洱生茶中醇类、酯类物质含量相对较高,而北部地区普洱生茶中醛类、酮类以及其他类物质含量相对较高。普洱生茶加工工艺与绿茶较为类似,香气成分主要源于糖苷前体水解、脂肪酸和类胡萝卜素氧化或高温下氨基酸的美拉德反应[3,17],临沧市南、北部地区普洱生茶香气成分、种类含量差异可能与加工鲜叶中香气前体物质有直接关系。

    图  1  临沧市普洱生茶主要香气成分PCA得分图
    Figure  1.  PCA score plot derived from the main aroma compents of raw Pu'er tea in Lincang City
    图  2  临沧市普洱生茶主要香气成分 PCA 载荷图
    注:图中的数字为表1中香气成分序号。
    Figure  2.  PCA corresponding loading plot derived from the main aroma compents of raw Pu'er tea in Lincang City

    为了更好地观测临沧市16份普洱生茶香气组成的相似度,采用HCA对整个香气成分含量进行分析。由图3可知,当横坐标为100时,16份普洱生茶样品分为2类。第一类聚集了临翔区、永德县、镇康县、凤庆县和云县等5个县(区)的普洱生茶样品,说明这类样品在香气组成有一定的相似性,而该类样品都集中在临沧市北部地区,该类样品中绝大多数醛类、酮类以及其他类香气物质含量相对较高。第二类聚集了沧源县、耿马县和双江县等3个临沧市南部地区的普洱生茶样品,该类样品中醇类、酯类香气物质含量相对较高。以上研究结果与PCA分析结果一致。

    图  3  临沧市普洱生茶主要香气成分聚类分析
    Figure  3.  HCA derived from the main aroma compents of raw Pu'er tea in Lincang City

    为了进一步明确临翔区、永德县、镇康县、凤庆县和云县等10个北部地区的普洱生茶样品与沧源县、耿马县和双江县等6个临沧市南部地区的普洱生茶样品的差异香气成分或种类,采用OPLS-DA对整个香气成分含量进行分析。从OPLS-DA模型下的得分图(图4)可以看出,临沧市南、北部地区的普洱生茶样品明显地分开,其中R2Y(cum)=0.915、Q2(cum)=0.828,说明该模型具有良好的稳定性和较好的预测能力。为了检验模型是否存在过度拟合,建立200次OPLS-DA模型置换检验(图5),置换检验验证结果为R2Y(cum)=0.759、Q2(cum)=−0.940,说明模型具有良好的稳健性,不存在过拟合现象。基于变量投影重要性(Variable important for the projection, VIP)大于1,共筛选出23个香气成分或种类作为区分临沧市南、北部地区普洱生茶香气的重要标志物(表2)。通常VIP值越大,变量在临沧市南、北部地区普洱生茶中的差异越显著。由表2可知,芳樟醇、异佛尔酮、酮类、醇类、醛类、β-环柠檬醛、α-环柠檬醛、2,2,6-三甲基环己酮、橙花醇、β-紫罗兰酮等VIP值相对较大,对临沧市南、北部地区普洱生茶分类贡献较大。从香气成分或种类含量上看,醇类物质总量及含量较高的芳樟醇、橙花醇在南部地区普洱生茶样品中的含量明显要高于北部地区,而酮类物质总量及含量较高的异佛尔酮、2,2,6-三甲基环己酮、β-紫罗兰酮的含量明显要低于北部地区;醛类物质总量及β-环柠檬醛、α-环柠檬醛在南部地区普洱生茶样品中的含量要高于北部地区,而含量较高的壬醛、己醛在临沧市南、北部地区的普洱生茶样品中差异不显著。

    图  4  临沧市普洱生茶主要香气成分OPLS-DA得分图
    Figure  4.  OPLS-DA score plots derived from the main aroma compents of raw Pu'er tea in Lincang City
    图  5  临沧市普洱生茶主要香气成分OPLS-DA置换检验图
    Figure  5.  OPLS-DA permutations plots derived from the main aroma compents of raw Pu'er tea in Lincang City
    表  2  基于OPLS-DA的VIP值大于1.0的香气成分
    Table  2.  Aroma components with VIP values of more than 1.0 as determined by OPLS-DA
    序号香气成分VIP值北部地区均值南部地区均值
    1芳樟醇1.4616.79±3.3937.83±6.22
    2异佛尔酮1.412.57±0.261.47±0.40
    3酮类1.3913.44±1.617.95±2.03
    4醇类1.3740.99±4.8355.83±5.94
    5醛类1.2729.54±2.6422.26±3.71
    6β-环柠檬醛1.263.20±0.681.86±0.62
    7α-环柠檬醛1.250.53±0.100.34±0.09
    82,2,6-三甲基环己酮1.243.41±0.821.81±0.67
    9橙花醇1.201.15±0.221.93±0.50
    10β-紫罗兰酮1.202.74±0.901.35±0.65
    112,3-二氢-2,2,6-三甲基苯甲醛1.181.33±0.260.81±0.27
    12反1,2-环戊二醇1.180.31±0.070.19±0.05
    13α-紫罗兰酮1.141.10±0.420.60±0.22
    146-甲基-5-庚烯-2-酮1.141.75±0.201.37±0.24
    15其他类1.136.51±0.925.10±0.99
    161-辛烯-3-醇1.0910.60±3.736.18±0.63
    17(2Z)-2-辛烯-1-醇1.082.21±0.811.24±0.21
    182,2,6-三甲基-6-乙烯基四氢-
    2H-呋喃-3-醇
    1.050.47±0.100.35±0.03
    19顺-氧化芳樟醇1.043.84±0.593.08±0.26
    20反-2-壬醛1.040.31±0.060.23±0.06
    214-萜烯醇1.030.39±0.120.23±0.08
    22异戊醛1.020.63±0.230.36±0.13
    23茶吡咯1.020.42±0.250.11±0.18
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    普洱生茶中主要香气成分及其呈香特性已基本明确。其中,不经贮藏的普洱生茶在香气品质上与晒青毛茶相似,香气组成以醇类香气为主,其次为醛类和酮类物质[1819]。而随着贮藏时间的延长,醇类、酮类以及含氮类物质呈下降趋势,而甲氧基苯类物质则呈增加趋势,呈现独特陈香的品质特点[2021]。本文从16份临沧市普洱生茶中共检测到48个主要香气成分,包括醇类13种、醛类17种、酮类8种、酯类4种和其他类6种。醇类物质占香气总量的比例最高,平均含量为46.55%;其次是醛类物质,平均含量为26.81%;酮类、酯类以及其他类香气物质占香气总量比例相对较小。由于本试验的16份样品为当年普洱生茶,均未经过自然贮藏发酵,香气成分中均未检测到甲氧基苯类香气成分。田小军等[22]研究发现甲氧基苯类香气成分在普洱茶自然发酵第7年才检测到,甲氧基苯类香气的增加是导致普洱生茶香型逐渐呈现陈香的品质特征重要因素。总体来看,临沧市普洱生茶的主要香气种类、组成与前人研究的云南普洱生茶结果相一致。

    利用多元统计方法对临沧市普洱生茶主要香气成分进行综合分析发现,沧源县、双江县、耿马县等临沧市南部地区与云县、凤庆县、永德县、临翔区、镇康县等临沧市北部地区的普洱生茶样品能够明显区分开。南部地区普洱生茶醇类、酯类香气物质含量相对较高,而北部地区醛类、酮类以及其他类香气物质含量相对较高。共筛选出23个香气成分或种类作为区分临沧市南、北部地区普洱生茶香气的重要标志物,其中芳樟醇、异佛尔酮、酮类、醇类、醛类、β-环柠檬醛、α-环柠檬醛、2,2,6-三甲基环己酮、橙花醇、β-紫罗兰酮对临沧市南、北部地区普洱生茶分类贡献较大。不同产地因温度、湿度、光照以及地形地貌等环境因素的影响,鲜叶原料在香气前体物质的含量、组成比例以及内含糖苷水解酶特性等方面存在较大差异,香气品质呈现明显的产地特征[2324]。高海拔茶园具有相对低温、高湿和多云雾的气候特征,有利于茶树含氮化合物和芳香物质的合成和积累,茶叶酮类和醛类含量所占比例升高,玫瑰香气和花果香味更加浓郁[2526]。茶叶香气中大量存在的醇类、醛类及内酯类化合物等往往是由饱和或不饱和脂肪酸转化而来,较低的海拔条件更有利于脂肪酸和不饱和脂肪酸的生成在,醇类、醛类及内酯类香气物质相对丰富[23,27]。因此,推测海拔高度是形成临沧市南、北部地区普洱生茶香气成分含量差异一个重要原因。

    本研究通过对临沧市16份普洱生茶样品的主要香气成分含量进行比较分析,并利用多元统计方法综合分析临沧市普洱生茶主要香气成分,一定程度上了解了临沧市普洱生茶的香气品质。然而,普洱生茶的香气成分受茶树品种、采摘季节、加工工艺和储藏条件等因素的影响,今后还需扩大临沧市不同季节、不同品种、不同生产厂家及不同储藏时间的普洱生茶样本量,进而为临沧市普洱生茶品质与产地判定等研究提供理论依据。

  • 图  1   临沧市普洱生茶主要香气成分PCA得分图

    Figure  1.   PCA score plot derived from the main aroma compents of raw Pu'er tea in Lincang City

    图  2   临沧市普洱生茶主要香气成分 PCA 载荷图

    注:图中的数字为表1中香气成分序号。

    Figure  2.   PCA corresponding loading plot derived from the main aroma compents of raw Pu'er tea in Lincang City

    图  3   临沧市普洱生茶主要香气成分聚类分析

    Figure  3.   HCA derived from the main aroma compents of raw Pu'er tea in Lincang City

    图  4   临沧市普洱生茶主要香气成分OPLS-DA得分图

    Figure  4.   OPLS-DA score plots derived from the main aroma compents of raw Pu'er tea in Lincang City

    图  5   临沧市普洱生茶主要香气成分OPLS-DA置换检验图

    Figure  5.   OPLS-DA permutations plots derived from the main aroma compents of raw Pu'er tea in Lincang City

    表  1   临沧市普洱生茶香气成分(%)

    Table  1   Aroma contents of raw Pu-er tea in Lincang City (%)

    序号香气成分凤庆
    县1
    凤庆
    县2
    云县1云县2永德
    县1
    永德
    县2
    临翔
    区1
    临翔
    区2
    镇康
    县1
    镇康
    县2
    耿马
    县1
    耿马
    县2
    沧源
    县1
    沧源
    县2
    双江
    县1
    双江
    县2
    均值
    1芳樟醇18.0717.4317.8518.2019.5819.5815.8217.957.9315.5244.1237.9643.9637.2827.1436.5324.68
    21-辛烯-3-醇5.004.9313.6414.737.2713.1013.8012.9211.389.225.636.555.407.136.376.028.94
    3顺-氧化芳樟醇3.212.993.313.833.574.094.444.584.653.702.753.402.803.173.123.263.55
    4反-氧化芳樟醇2.852.162.081.411.931.601.662.171.691.572.872.092.222.122.342.142.06
    5(2Z)-2-辛烯-1-醇0.991.062.273.021.632.782.873.132.671.671.151.510.911.391.221.241.84
    6橙花醇1.211.351.021.241.231.151.131.490.661.001.601.562.162.091.412.741.44
    7α-松油醇1.851.680.880.941.351.241.662.081.171.351.011.200.890.940.921.261.28
    82-乙基己醇1.241.050.640.511.571.070.910.772.172.311.020.950.520.600.930.571.05
    91-戊醇0.670.670.270.230.220.330.820.430.230.200.230.250.951.010.190.420.45
    102,2,6-三甲基-6-乙烯基
    四氢-2H-呋喃-3-醇
    0.670.470.450.450.520.430.310.340.560.450.340.390.340.350.360.300.42
    114-萜烯醇0.520.450.270.270.350.340.530.580.280.300.200.280.160.130.270.340.33
    12反1,2-环戊二醇0.320.250.300.290.280.320.300.210.450.380.220.250.150.130.240.150.27
    13环戊醇0.390.260.320.170.250.280.180.180.330.360.200.210.160.150.300.170.24
    14醇类合计36.9934.7543.3045.2939.7546.3144.4346.8334.1738.0361.3456.6060.6256.4944.8155.1446.55
    15壬醛8.7111.216.547.627.577.638.368.138.139.043.406.046.817.947.588.427.69
    16己醛4.283.9110.308.014.344.454.353.654.545.963.103.574.154.995.534.524.98
    17β-环柠檬醛3.923.822.442.563.962.542.882.614.093.132.012.111.061.202.722.052.69
    18庚醛1.681.892.302.132.151.462.142.261.402.001.351.551.952.051.951.951.89
    19癸醛1.552.321.041.451.431.881.471.501.972.020.741.311.241.601.551.471.53
    202-庚烯醛0.601.152.112.910.911.820.901.521.351.030.250.870.871.470.630.911.21
    212,3-二氢-2,2,6-
    三甲基苯甲醛
    1.421.450.930.991.571.281.191.211.411.801.061.060.440.500.950.831.13
    22反-2-癸烯醛1.000.700.981.181.171.011.111.071.300.990.670.670.840.951.020.650.96
    23苯乙醛1.502.101.161.360.621.070.480.431.340.550.450.720.280.470.820.780.88
    24正戊醛0.800.230.500.371.270.251.320.351.560.600.890.331.270.701.490.530.78
    252-甲基丁醛1.350.911.290.810.920.990.540.410.720.720.870.680.500.250.940.410.77
    26异戊醛0.610.690.730.560.580.630.370.341.170.620.460.480.320.190.470.230.53
    27α-环柠檬醛0.590.580.390.340.570.550.520.470.670.620.350.390.220.280.470.320.46
    283-羟基丁醛0.440.420.360.230.580.390.380.280.860.840.270.200.310.320.420.210.41
    292-已烯醛0.301.030.280.300.180.200.400.400.460.530.230.270.210.300.420.400.37
    30反-2-壬醛0.170.300.290.420.280.330.280.350.350.290.150.220.230.310.200.280.28
    31戊二醛0.380.190.330.230.280.240.180.210.280.260.310.320.230.140.300.190.25
    32醛类合计29.2732.9031.9731.4928.4026.7126.8825.1931.6331.0016.5720.8020.9323.6627.4724.1426.81
    332,2,6-三甲基环己酮3.653.322.932.913.382.993.233.005.663.052.121.980.971.122.771.892.81
    34β-紫罗兰酮4.003.741.601.643.692.212.232.142.833.341.112.120.620.661.991.592.22
    35异佛尔酮2.432.682.422.842.372.752.222.473.092.431.171.731.101.061.921.832.16
    366-甲基-5-庚烯-2-酮1.641.581.941.911.341.991.851.801.641.781.261.101.191.471.771.401.60
    37香叶基丙酮1.061.230.690.911.151.210.941.071.261.231.840.810.660.720.910.741.03
    38α-紫罗兰酮1.631.800.650.621.400.860.860.731.371.090.690.790.310.370.830.580.91
    392-庚酮0.430.400.590.520.540.640.620.630.740.820.430.500.340.450.360.420.53
    40反-3-辛烯-2-酮0.871.150.13
    41酮类合计14.8414.7511.6912.5013.8712.6511.9511.8416.5913.748.629.035.195.8510.558.4511.38
    42水杨酸甲酯0.941.510.650.991.191.461.461.940.861.081.451.941.692.330.971.501.37
    43二氢猕猴桃内酯1.061.060.600.630.730.540.580.630.760.630.560.500.560.740.720.650.68
    442-甲基戊酸甲酯0.110.110.070.050.160.090.090.070.170.150.090.080.050.050.130.090.10
    45异戊酸叶醇酯0.480.560.07
    46酯类合计2.122.671.311.672.082.102.122.641.791.852.102.532.783.691.832.242.22
    47柠檬烯2.802.121.721.642.372.132.973.483.362.742.672.381.742.103.772.292.52
    48二甲硫2.801.811.631.101.360.640.480.461.050.560.960.671.180.751.210.591.08
    49茶香螺烷0.921.230.730.861.251.051.471.741.111.360.790.780.570.700.900.791.02
    502-乙基吡咯0.630.550.940.630.850.680.990.920.901.030.630.610.490.560.720.530.73
    510.390.470.230.300.540.620.270.330.380.380.220.270.260.320.250.220.34
    52茶吡咯0.390.830.930.190.260.340.290.370.200.370.230.430.30
    53其他类合计7.937.016.184.726.635.466.477.307.006.445.505.144.244.436.854.425.98
    54总量91.1392.0694.4695.6590.7293.2391.8993.8191.1891.0894.1494.1093.7794.1091.5194.3892.95
    注:“−”表示未检出。
    下载: 导出CSV

    表  2   基于OPLS-DA的VIP值大于1.0的香气成分

    Table  2   Aroma components with VIP values of more than 1.0 as determined by OPLS-DA

    序号香气成分VIP值北部地区均值南部地区均值
    1芳樟醇1.4616.79±3.3937.83±6.22
    2异佛尔酮1.412.57±0.261.47±0.40
    3酮类1.3913.44±1.617.95±2.03
    4醇类1.3740.99±4.8355.83±5.94
    5醛类1.2729.54±2.6422.26±3.71
    6β-环柠檬醛1.263.20±0.681.86±0.62
    7α-环柠檬醛1.250.53±0.100.34±0.09
    82,2,6-三甲基环己酮1.243.41±0.821.81±0.67
    9橙花醇1.201.15±0.221.93±0.50
    10β-紫罗兰酮1.202.74±0.901.35±0.65
    112,3-二氢-2,2,6-三甲基苯甲醛1.181.33±0.260.81±0.27
    12反1,2-环戊二醇1.180.31±0.070.19±0.05
    13α-紫罗兰酮1.141.10±0.420.60±0.22
    146-甲基-5-庚烯-2-酮1.141.75±0.201.37±0.24
    15其他类1.136.51±0.925.10±0.99
    161-辛烯-3-醇1.0910.60±3.736.18±0.63
    17(2Z)-2-辛烯-1-醇1.082.21±0.811.24±0.21
    182,2,6-三甲基-6-乙烯基四氢-
    2H-呋喃-3-醇
    1.050.47±0.100.35±0.03
    19顺-氧化芳樟醇1.043.84±0.593.08±0.26
    20反-2-壬醛1.040.31±0.060.23±0.06
    214-萜烯醇1.030.39±0.120.23±0.08
    22异戊醛1.020.63±0.230.36±0.13
    23茶吡咯1.020.42±0.250.11±0.18
    下载: 导出CSV
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  • 收稿日期:  2022-12-27
  • 网络出版日期:  2023-08-15
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