Analysys Of Yunnan Black Tea Aromatic Components Based On SPME-GC-MS

The tea aroma composition, which plays a great role in quality of tea, has been a research hotpot in recent year. In this paper, headspace solid-phase microextraction coupled with gas chromatography-mass spectrometry (HS-SPME-GC-MS) was applied to analyze aromatic components in Yunnan black tea. The factors affecting the extraction efficiency were investigated and then qualitative analysis of aroma components in Yunnan black tea was performed. On the other hand, the HS-SPME method was chosen for quantitative analysis of ten floral and fruity compounds in Yunnan black tea samples. The main contents were as follows:1 The extraction and analysis of aroma components in Yunnan black tea(1) The sensitivity and repeatability of five fibers with different polarities were evaluated. The result showed that 50/30 μm DVB/CAR/PDMS fiber exhibited the highest extraction efficiency.(2) The effects of extraction conditions were investigated, such as the sodium chloride saturation concentration、brewing proportion of tea and water、extraction temperature and extraction time to extraction efficiency. On the basis of single factor experiment, Central-Composite experimental design were used to optimize HS-SPME conditions. The obtained optimal HS-SPME conditions were:sodium chloride saturation concentration 100%, proportion of tea and water 1:5.92, extraction time 60.9min, extraction temperature 60℃. And then a new multi-temperature control strategy was applied to obtain a high extraction efficiency for aromatic components during HS-SPME process. Mixture experimental design were used to optimize the extraction time at each temperature. The final optimised extraction method was that the tea sample held at 70℃ for 30.7 min,50℃ for 17.4 min and 30℃ for 11.9 min. And compared to constant extraction temperature, the more low-boiling point and total aromatic components were extracted by multiple extraction temperatures.(3) The aromatic compounds in 16 Yunnan black tea samples were extracted with the final optimized HS-SPME conditions and analysised by GC-MS. A total of 115 kinds of aroma components were identified, and 72 mutual aroma compounds were determined in sixteen tea samples. The average content of floral and fruity aroma compounds account for 40.64% of the total content, which has important effects on the characteristics of Yunnan black tea aroma.2 Quantitative analysis of the floral and fruity aroma compounds in Yunnan black tea samples(1) Based on fiber screening result in the previous section, the 75 μm CAR/PDMS fiber was selected as the optimal one for the extraction of floral and fruity aroma compounds.(2) Then the effects of extraction conditions such as brewing proportion of tea and water、 extraction temperature and extraction time to extraction efficiency were investigated. On the basis of single factor experiment, Orthogonal experimental design were used to optimize HS-SPME conditions. The obtained optimal HS-SPME conditions were:proportion of tea and water 1:5, extraction time 70 min, extraction temperature 70℃. Under the optimal conditions, the linear regression correlation coefficients (R2) for the ten floral and fruity aroma compounds were between 0.9965 to 0.9997, and the method accuracy is satisfactory with recoveries between 89.6% to 110.6%, and their RSD were lower than 12%.(3) Under the optimized conditions, the content of the floral and fruity aroma compounds in sixteen Yunnan black tea samples was determined by HS-SPME-GC-MS method. It suggests that the method has satisfactory accuracy and good repeatability.