## 1 Introduction  
Baijiu, as a flavor product, has its aroma characteristics playing a crucial role in consumers' selection process. Baijiu is a distilled liquor primarily produced from cereals and grains. It employs various fermentation starters--including _daqu_, _xiaoqu_, _fuqu_, enzyme preparations, and yeast--to facilitate starch saccharification and fermentation. The production process encompasses sequential stages of steaming, saccharification, fermentation, distillation, aging, and blending [1]. The aging process of Baijiu is a vital step in its production; indeed, the enhancement of aroma is significantly noticeable after aging, leading to a marked improvement in quality [2]. Industry surveys (e.g., the *2025 China Baijiu Market Mid-Term Research Report) indicate significantly higher consumer acceptance and consumption volume for extensively aged Baijiu [3]. Investigating the science behind Baijiu aging therefore addresses critical market demands while advancing modernization of traditional distilling through evidence-based research. Consequently, there is a growing interest in studying the aging process. By elucidating the changes that occurred during aging and the aroma benefits of properly stored Baijiu, we can better guide flavor regulation throughout the storage process, ultimately enhancing the quality of traditional Chinese Baijiu. _Nongxiangxing_ Baijiu is one of the most significant types in the Baijiu category. In 2021, its sales revenue constituted the dominant share of China's Baijiu market, establishing itself as the important revenue source within the industry [4]. _Gujingong_, a distinctive variety produced in the _Huanghuai_ production area, is a brand of unique and traditional _Nongxiangxing_ Baijiu. While existing studies have characterized its key aroma-active compounds, systematic investigations into aging-related critical substances remain largely unexplored [5]. Elucidating the scientific principles of maturation requires identifying key aromatic compounds exhibiting significant concentration variations during storage periods. To further reveal the underlying reasons for consumers' preference toward well-aged Baijiu products with superior flavor quality is important. Research into the flavor chemistry of _Nongxiangxing_ Baijiu has a long-standing history. [PERSON] was the first to identify the contents of ethyl lexanoate and ethyl lactate, which are the main aroma compounds in concentrated Baijiu [6]. [PERSON] et al. analyzed _Nongxiangxing_ Baijiu using HS-SPME in combination with GC-O-AEDA. Their findings revealed that esters, particularly ethyl lexanoate, were the predominant contributors to the aroma of Baijiu samples [7]. [PERSON] identified 50 aroma substances in commercial _Nongxiangxing_ Baijiu through sensory analysis and briefly examined the differences in compounds among various Baijiu samples [8]. In aging studies involving two other major aroma types of Baijiu, [PERSON] et al. concluded that terpenoids, aldehydes, ketones, and sulfur compounds are key contributors to the aroma of aged Baijiu after analyzing samples of _Qingxiangxing_ Baijiu [9]. Similarly, they found that furanones, aldehydes, and pyrazines are associated with the aging aroma in _Jiangxiangxing_ Baijiu [10]. For _Nongxiangxing_ Baijiu research, [PERSON] et al. undertook a comprehensive study of _Nongxiangxing_ Baijiu, employing Pearson's correlation coefficient to uncover characteristic compounds linked to sensory attributes. They identified eight esters and acids associated with the aging aroma [11]. Current research on _Nongxiangxing_ Baijiu has predominantly focused on alcohols, esters, and acids, with limited attention paid to other trace substances. Consequently, it was hypothesized that non-alcohol/ester/acid compounds play a pivotal role in shaping the maturation-driven aroma profile of _Nongxiangxing_ Baijiu during aging.