| Black tea is the most widely consumed tea beverage over the world, popular among people due to its natural compounds, nutrition, and health care function. China is now greatly developing black tea. In 2015, the output of black tea has reached over 255,000 tons, accounting for 11.1% of the total output of tea, in which 73% of black tea was for selling on domestic market while export sale stagnated. Jasmine tea is unique to China and originated early. In the late Qing Dynasty to the 1990 s, jasmine tea developed rapidly, accounting for one-third of the national tea sales, which, however, is now less than 1/10. Jasmine tea and black tea need new angles, levels to showcase the new image of Chinese tea like innovation to traditional processing technology, developing tea with different flavors and functions, expanding the use of traditional black tea to meet the diverse consumption needs, extending the industrial chain of black tea and improving the comprehensive benefits of black tea industry. This paper was based on the analysis of the aroma characteristics in the aroma releasing process of jasmine tea. Using aroma absorbing and releasing theory of tea base, jasmine black tea was scented through two processing technology. Quantitative descriptive analysis, sensory evaluation, taste active value and aroma active value were used to evaluate the quality characteristics of jasmine black tea. The main research contents and results were presented as follows:1. HS-SPME-GC-MS was used to detect the aroma releasing process of in vitro jasmine. The result showed that the alcohols appeared decreased first and then increased in the process of releasing while aromatic hydrocarbons and esters exhibited an opposite trend. They reached the minimum and the maximum at 23:00 respectively and showed great difference at 7:00 the second day during which the quality of jasmine flowers aroma evaluated with sensory evaluation was the best. Principal components analysis(PCA) was used to analyze jasmine aroma. The cumulative contribution of first 5 principal components of jasmine has reached 86%, in which the first principal component contributed more than half of the variance contribution rate including cis-3-hexenol acetate, methyl salicylate, orange flower acetate, etc.; the second principal component contained benzyl alcohol, benzene methyl formate, linalool, butyric acid cis-3-hexenyl ester, indole,2-amino benzoic acid methyl ester, orange flower tertiary alcohols 7 kinds of materials. Combined with the correlation between composition change in opening process and sensory evaluation of jasmine, the second principal component was thought to have important contribution in aroma and flavor.2. Traditional scenting technology and continuous scenting technology were adopted to primarily process black jasmine tea and the moisture and temperature parameters in the process were recorded. The result showed that the moisture absorption ability of black tea was weaker than that of green tea due to structure reasons; the amount of first scenting flowers of black tea base in the process of scenting was more than 50%, the moisture content rose from 6% to 12% and the temperature during spreading was no higher than 42℃. Larger unit scenting flower quantity did not make tea base temperature in the process of scenting rise to jasmine’s best scenting temperature. The technology of scenting green jasmine tea thus didn’t suit for processing black jasmine tea.3. Through the detection of biochemical components in jasmine tea analysis, the resulted show that the chemical components of different raw materials processed by different scenting technologies presented significant differences. The contents of polyphenols, total soluble sugar, caffeine, thearubigins and theabrownins in H1, total soluble sugar, free amino acid in H2 and flavonoid in H3 processed by traditional scenting technology and continuous scenting technology were significant different. The contents of water extract, tea polyphenols, total soluble sugar, TF-3’g and TFdg increased along with the processing times while EGCG, EGC and etc. showed a downward trend. The taste active values of catechins and theaflavins monomers were analyzed. The result indicated that the taste active values of EGC, EGCG, TF-3’g, TF-3G, TFdg and caffeine were greater than 1, among which the values of caffeine and TFdg were the greatest, indicating the greatest contribution.The sensory evaluation results show that, in terms of appearance, which could be worsen due to the re-absorption of moisture, H1 showed no obvious change after scenting; the infusion of H2 and H3 lightened after traditional scenting but darkened after continuous scenting; in terms of taste, H1 tasted more balanced after traditional scenting with a highest score at 87 points; H2 tasted less bitter after scenting process, highest at 84 points; H3 exhibited no significant difference.4. The volatile components analysis of jasmine black tea and black tea base were conducted using 25 μg/m L and 5μg/m L of ethyl decanoate, respectively to quantify the contents. The average contents of aroma components were about 75.37 μg/L in jasmine black tea and black tea base, about 491.81 μg/L after traditional scenting technology, and about 356.7 μg/L in continuous scenting technology. The volatile component contents has increased 6.5 times and 4.7 times separately; The kinds and contents of aldehydes were decreased largely, accompanied by a substantial increase in the kinds and contents of alcohol and ester aroma substances, which could be considered as a re-processing of black tea aroma. The OAV values, obtained after analysis in 10 volatile components were greater than 1, namely tertiary alcohol benzene methyl formate, benzene methyl acetate, linalool, orange flower, beta ionone, anti-2-,Shun 6 nonadienal, decanal, heptanal, is hexanal and methyl salicylate, among which beta ionone’s OAV value has reached 412.23.Sensory evaluation results showed that the aroma concentration increased significantly after scenting. Meanwhile, typical aroma substances of black tea disappeared, so was the fermented flavor. Jasmine possessed sweet aroma when hot-smelled, significantly and exhibited flowery flavor when cold-smelled. By scenting, the aroma score and flavor type of H2 increased significantly.5. Quantitative descriptive analysis and sensory evaluation results showed high consistency. Quantitative descriptive analysis could outline the differences between the aroma and taste of tea samples and the correlation between samples and taste properties and aroma properties, which could theoretically be adapted as an auxiliary evaluation method of sensory evaluation of tea.6. After processing with different methods of scenting on different classes of tea base, aroma and taste varied on different degrees. Especially for aroma type, recombining in aroma substances types and contents, it changed greatly, indicating that different tea base should be matched with different scenting processes to improve the quality of jasmine black tea. |
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