## 3 Results and Discussion
### Analysis of Odor Index in Teas of Different Types  
There is a general belief that a compound has a variety of odors and many compounds have a common odor. For example, \(\beta\)-ionone has a combination of woody, floral and burnt odors [28; 29]. (\(E\))-3-Hexen-1-ol has a strong green odor with light fruity odor [26; 30; 31], while \(\beta\)-cyclocitral has a strong fruity odor with light green and woody odors [17; 32]. After the OVA-splitting process, the odor characteristic of each tea sample was clarified (Tables 1-5). For simplicity and application, the index of odor I(o) was introduced to describe the relative intensity of each odor to OAVt. The results showed that the odor characteristics of tea with different types have distinct differences (Figure 1). The aroma of white tea was mainly composed of I( floral) 0.416, I(woody) 0.260, and I(green) 0.147, and the sum of the three I(o) was 0.823. The aroma of green tea was mainly composed of I(green) 0.455, I(fruity) 0.237, I(woody) 0.119, and I(fatty) 0.108, and the sum of the four I(o) was 0.919. The aroma of oolong tea was mainly composed of I(fruity) 0.367, I(fatty) 0.220, I(woody) 0.117, I(floral) 0.117, and I(green) 0.115, and the sum of the five I(o) was 0.936. The aroma of red tea was mainly composed of I(fruity) 0.429, I(woody) 0.157, I(green) 0.154, and I(floral) 0.141, and the sum of the four I(o) was 0.881. The aroma of dark tea was mainly composed of I(woody) 0.328, I(floral) 0.306, I(fatty) 0.171, and I(green) 0.134, and the sum of the four I(o) was 0.939. Figure 1: Radar chart of index of odor I(o) in tea with different types. No any odor has its I(o) greater than 0.50 in five types of tea (Figure 1). This indicated that tea fragrance is complexed with one or two odors as dominant components, complemented by other odors. The difference of the dominant odor components in each type of tea determines the specific odor of the tea. In other words, the differential of the dominant odor components in teas contribute the differential of odor characteristic in each type tea. To briefly summarize, green tea is a strong-flavor tea (highest OAVt) with highlight green accompanied by fruity, woody, and fatty odors; oolong tea was strong-flavor tea (higher OAVt) with fruity and fatty accompanied by woody, floral, and green odors; red tea was strong-flavor tea (higher OAVt) with highlight fruity accompanied by woody, green, and floral odors; white tea was light-flavor tea (low OAVt) with floral, woody and green odors; and dark tea was light-flavor tea (low OAVt) with woody and floral accompanied by fatty and green odors. The results fitted perfectly with the people's consensus on these five types of tea. Our results proved that the OAV-splitting method is feasible to evaluate the aroma intensity and odor characteristics of tea aroma. We hope that, in the near future, when people are discussing tea fragrance such as 'the tea aroma of A is much more intense than that of B', they could add 'because the OAV of A is 492.02 and B is 68.10' (Figure 2). Furthermore, subjective descriptions such as 'the fruity odor of No 1 tea sample is better than that of No 2' could also be updated to 'No 1 tea sample is OAV = 471.88 and I(fruity) = 0.43, however, No 2 is OAV = 302.74 and I(fruity) = 0.37' (Figure 2). The OAVt and I(o) are the digital evaluation for aroma quality of a tea. Therefore, the description and communication of tea fragrance will be more  
The aroma compounds, aroma intensity and odor characteristics of tea are also affected by many factors, such as variety and culturing, origin and region, processing and storage, and so on. It is difficult to consider the influence of various factors on tea aroma in this paper. In China, almost all of the central and southern province, as well as the western provinces, have green teas. Due to the feature of red tea technology, all tea varieties can be processed to red tea, even in the Henan and Guizhou provinces of China.