Effects of Different Fermentation Methods on Flavor Quality of Liupao Tea Using GC-Q-TOF-MS and Electronic Nose Analyses  
[PERSON]  
1 College of Tea Science, Yunnan Agricultural University, Kunming 60500, China; [EMAIL_ADDRESS] (X.Z. ); [EMAIL_ADDRESS] (H.Z. ); [EMAIL_ADDRESS] (R.D. ); [EMAIL_ADDRESS] (C.M. ); [EMAIL_ADDRESS] (L.R. ); [EMAIL_ADDRESS] (X.Y. ); [EMAIL_ADDRESS] (Q.W. ); 1 [EMAIL_ADDRESS] (N.C.); [EMAIL_ADDRESS] (L.Y. ); [EMAIL_ADDRESS] (X.T. ); [EMAIL_ADDRESS] (Y.B. ); [EMAIL_ADDRESS] (Y.L. ); [EMAIL_ADDRESS] (X.D. );  
aging [5]. In contrast, cold fermentation does not require the initial steaming step before fermentation. Comparing the two techniques, the advantages of hot fermentation are that it occupies the site for a short period of time and is more efficient. However, the degree of transformation of the raw material achieved within this short period of time is not significant, and a longer aging period may be required to obtain the desired red and thick quality. On the other hand, the advantage of cold fermentation is that it is energy-efficient and allows for better control of the degree of fermentation. However, it requires a longer fermentation time and occupies a long period of time at the site [6]. Microorganisms play an important role in the fermentation process of Liupao tea. However, traditional production methods face challenges such as long fermentation cycles, difficulty controlling fermentation strains, and inconsistent product quality [7]. To address these issues, it is essential to continuously optimize and improve the traditional Liupao tea fermentation process, develop new processing equipment, control the microbial species during fermentation, stabilize product quality, and advance the research and development of high-quality Liupao tea products. In recent years, there has been a growing interest in innovative fermentation methods aimed at enhancing the quality of Liupao tea. [PERSON] [8] conducted a study to identify the most suitable new process combination for Liupao tea by investigating the impact of exogenous enzymes and fermentation conditions on the fermentation rate and quality of Liupao tea. [PERSON] [9], in addition, carried out an artificial inoculation fermentation test on Liupao tea. By combining five dominant strains with seven different treatments, [PERSON] found that the addition of exogenous microflora could lead to significant transformations in the composition of Liupao tea. [PERSON] et al. [7] fermented Liupao tea with the inoculation of \"_E. cristatum_\", resulting in a notable enhancement in the quality of Liupao tea. Similarly, [PERSON] et al. [10] used high-throughput sequencing to analyze the microbial community composition of Liupao tea at different stages of can fermentation, which provided a basis for innovating Liupao tea fermentation technology and leveraging microbial strains for improved outcomes. As one of the microorganisms with a long history of applications in food processing in China, _M. purpureus_ is now widely employed in the field of food fermentation [11; 12; 13]. In addition, _M. purpureus_ has been used several times in the fermentation of post-fermented tea. [PERSON] et al. applied a strain of _M. purpureus_ (independent patent, 201010182965.9) capable of producing lovastatin to ferment Pu-erh tea, resulting in Pu-erh tea with a distinctive \"Chenquan\" aroma, and extensively examined its characteristic aroma [14]. [PERSON] et al. [15] revealed the specificity of aroma in Pu-erh tea through different fermentation methods of _M. purpureus_. However, no relevant studies have investigated the flavor quality of Liupao tea fermented by _M. purpureus_. This study aims to comprehensively investigate the effects of different fermentation methods under the action of _M. purpureus_ on the characteristic aroma of Liupao tea. The electronic nose (E-nose) is an olfactory system that simulates the mammalian nose. It utilizes a sensor array to detect the aroma of samples, allowing for direct access to the overall flavor characteristics.