焙火程度对黄大茶挥发性香气成分的影响

Effect of Roasting Degree on Volatile Aroma Components of Large-leaf Yellow Tea

摘要:

黄大茶因“锅巴香”而闻名，拉老火（烘焙工艺）是能够形成其特征风味的关键工序。利用气相色谱-质谱联用（Gas Chromatography-Mass Spectrometry，GC-MS）技术分析经水蒸汽蒸馏（Steam distillation，SD）提取的黄大茶挥发性香气成分，结合感官评价研究不同烘焙程度对黄大茶[小火（120~130 ℃）、中火（130~140 ℃）及老火（145~155 ℃）]挥发性品质的影响。结果表明：小火、中火及老火黄大茶均以杂环类化合物、芳香族类及酯类成分为主，小火及中火黄大茶挥发性成分数量较少（分别为84和72个），且含有反-4-己烯醇、N-乙基苯胺等具青草气或焦苦风味的异气，老火黄大茶挥发性成分较多（检测到104个，鉴定出99种），多是具烘焙、焦糖香的含氮杂环化合物，感官评价的结果揭示老火黄大茶具有饱满的烘焙香及焦糖香，坚果风味突出，且具有黄大茶特征的锅巴香（得分8.33）。老火烘焙能够成就挥发性品质优异的黄大茶。

Abstract:

Large-leaf yellow tea (LYT) is famous for its crispy-rice-like odor, and “Lalaohuo” (roasted processing) is the key important processing to form the characteristic flavor. Using Gas Chromatography-Mass Spectrometry (GC-MS) technology to investigate the volatile compositions of Large-leaf yellow tea by means of steam distillation (SD), and the effect of roasting degree under small fire (120 ℃~130 ℃), medium fire (130 ℃~140 ℃) and old fire (145 ℃~155 ℃) on its volatile quality coupled with sensory evaluation was studied. The results revealed that heterocyclics, aromatics and esters compounds were the mail volatiles of LYT undergoing small fire, medium fire and old fire roasted processing, the former two owned less volatiles (had 84, 72 volatiles, respectively), and also had undesired odors that are (E)-4-hexen-1-ol and N-ethylbenzenamine, which are of grassy or burnt flavor; the latter one contained much more volatiles (104 volatile compounds were detected, and of which 99 volatiles were identified), especially for containing-nitrogen heterocyclics which are of roasted, caramel-like odor in tea. And also the sensory evaluation results matched well with the data of volatile compositions, the LYT undergoing old fire processing enriched in roasted and caramel-like odor, protruded the nutty flavor, and had the characteristic flavor of ‘Crispy-rice-like odor’ (had the highest evaluation score, 8.33). Old fire roasted processing can make an excellent volatile quality of LYT.