Study On Changes Of Aroma And Other Physical And Chemical Factors During Scenting Processes Of Jasmine Tea

Jasmine tea scenting at different conditions was studied in this thesis. Changes of moisture, temperature, aroma and other inherent chemical components, such as tea polyphenols, amino acids, caffeine, soluble sugar and water-extracted substances at different stages of scenting process were discussed for the first time. The main results are as follows. 1. Changes of aroma components in tea base and jasmine flower during traditional scenting were studied. The results indicated that the difference of moisture content between tea base and jasmine flower was gradually diminished as scenting procedure extended. The aroma content was extremely significantly related with scenting time and moisture difference. Aroma of jasmine tea was derived from jasmine aroma components that were absorbed by tea base, but rarely from tea base itself. 2. Changes of aroma components during the scenting at various room temperatures were studied. Aroma-releasing from jasmine flower could be promoted when room temperature for scenting was appropriately raised. However, flower life could be affected if the temperature was too high. The aroma quality scented at 3OC was better than those at 200C and 400C. Aroma analysis revealed that the difference was extremely significant among the three treatments. Meanwhile, because temperature of tea pile raised quickly at 300C, it was necessary to turn over the tea pile for decreasing the temperature during the scenting. 3. Changes of aroma components in tea base during four scentings with different jasmine flower ration were studied. The results showed that for tea base with less flower ration in the first scenting, content of aroma was higher than that with more flower ration, and the percentage of flower aroma component to total was also raised on a large scale as the frequency of scenting increased and jasmine flower was appropriately supplied in the fourth scenting. For more flower ration in the first scenting, aroma component was quickly formed. However, the flower aroma could not be used so enough that some aroma was lost. Moreover, with a lower flower ration in later scenting, the quality was lower than that of less flower ration in the first scenting. 4. Changes of aroma components at various ratios of moisture content were studied. The results demonstrated that higher percentage of moisture content was more advantageous to absorb aroma. The absorption speed was quicker and the amount was larger. On this experiment condition, the aroma quality of jasmine tea was better when percentage of moisture content of tea base was 20%?0%. First scenting time of tea base with higher percentage of moisture content could be appropriately reduced. The effect would be far better if the wet tea base continued to scent and not dried after the first scenting in traditional way. 5. In this research, besides by using GC-MS, the quality of jasmine tea was also evaluated by sensory way. The conclusions drown from both perspectives were consistent. 6. Changes of tea polyphenols, amino acids, caffeine, soluble sugar and water-extracted substances at variousconditions were studied. The results indicated that they played amore imPortant role in the taste of infusion, and had less effecton liquor.