# Formation Mechanisms and Kinetic Modeling of Key Aroma Compounds During Qidan Tea Roasting
###### Abstract  
Understanding the changes in tea aroma and non-volatile substances during roasting is essential for optimizing tea processing and enhancing tea quality. In this study, the Carbon Module Labeling (CAMOLA) technique was employed to simulate the roasting conditions of Qidan, thereby elucidating the formation pathway of the theanine-glucose Maillard system. Combined with sensory evaluation, the results indicated that the floral and fruity aromas of Qidan tea decreased, while the woody, roasted, smoky, and herbal aromas increased with prolonged roasting time. Kinetic modeling demonstrated that higher temperatures favored the production of benzaldehyde, which was directly proportional to the heating temperature. In contrast, pyrazines exhibited zero-order kinetics, influenced by both temperature and time. An increasing trend in furans was observed with rising temperature and extended heating time. The kinetic equations effectively describe the changes in aroma compounds associated with merad, highlighting the differences in the production patterns of aroma compounds under varying roasting conditions. This study provides a theoretical foundation for optimizing roasting parameters to enhance tea quality. Qidan tea; roasting time; aroma formation; furan compounds; Carbon Module Labeling (CAMOLA) technique 22 May 202514 June 202514 June 202516  
effectively replicated the flavor profile of tea [5]. It has been suggested that 3,5-dimethyl-2-ethylpyrazine may contribute to the aroma of roasted Shuixian [1]. Notably, these specific pyrazines were not detected in studies on the aroma of Tieguanyin, another Oolong Tea from northern Fujian [6], indicating the unique flavor composition of Wuyi Rock Tea. While pyrazines have received considerable attention in tea aroma research, Strecker aldehydes have been relatively overlooked in previous studies. However, recent research has started to shed light on their significance in tea flavor. For example, [PERSON] and [PERSON] [7] employed molecular sensory science techniques to identify 2/3-methylbutylraldehyde as a key aroma-active compound in Darjeeling black tea. These findings, along with those related to the pyrazine series, suggest that both pyrazines and Strecker aldehydes play crucial roles in the unique aroma profile of Wuyi Rock Tea [8]. Nevertheless, the specific key pyrazine and Strecker aldehyde aroma-active compounds in Wuyi Rock Tea remain largely unclear, and there is a lack of comprehensive research on the effects of different roasting times on the pyrazine components and their formation mechanisms in this type of tea. The Maillard reaction is a complex and multi-step chemical process that occurs during tea roasting and can be broadly divided into three distinct phases. The initial phase involves the condensation of amino acids with reducing sugars, leading to the formation of Amadori and Heyns products. In the intermediate phase, the sugars and amino acids are cleaved from these products. The final phase is characterized by a series of reactions, including dehydration, fragmentation, cyclization, and polymerization [9]. Wuyi Rock Tea fresh leaves are rich in total sugars, proteins, and free amino acids, which account for 40% to 60% of the total dry weight [10]. This abundant material base, combined with the roasting process, provides favorable conditions for the Maillard reaction to occur. Theanine, which constitutes more than 50% of the total amino acids in tea, has been shown to play a vital role in the production of 2-methylpyrazine, 2,5-dimethylpyrazine, and trimethyl pyrazine [11]. During the production of Wuyi Rock Tea, enzyme catalysis helps to release amino acids and reducing sugars from their bound state, creating a more conducive environment for the Maillard reaction and the formation of pyrazines and Strecker aldehydes during the roasting process.