## 1 Introduction  
Baijiu is a traditional Chinese distilled liquor, the production technique of which can be dated back 5000 years. Alongside brandy, whisky, gin, vodka, and rum, baijiu is recognized as one of the six world-renowned distilled spirits [1, 2]. Drinking baijiu neat is the most traditional and classic way to enjoy it. This method fully preserves the original aroma and taste of baijiu, allowing drinkers to appreciate its intricate flavor profile. When consuming baijiu neat, it is typically poured into specialized small cups, which usually hold 20 to 30 mL. Baijiu is made from sorghum, wheat and other grains through saccharification, fermentation, distillation, aging and other processes. Due to the diversity of terrain and climate, raw material, manufacturing process and other factors, baijiu can be divided into approximately 12 different aroma types. Among them, soy sauce-aroma, light-aroma, and strong-aroma types are considered as the three basic aroma types due to their widely known flavor characteristics [3]. Soy sauce-aroma baijiu is characterized by its high acidity, presenting a slightly yellow and transparent appearance [4]. It boasts a prominent soy sauce-like aroma, with a delicate taste, long aftertaste and a lingering fragrance that remains in the empty cup. The key flavor compound of light-aroma baijiu is ethyl acetate. Light-aroma baijiu is colorless and transparent, with a pure, sweet, and balanced flavor, and the aftertaste is clean [5]. Strong-aroma baijiu is characterized by a high content of ethyl hexanoate, with short-chain fatty acids and their ester derivatives making a major contribution to its distinctive flavor [6]. Strong-aroma baijiu can be further divided into Sichuan category and Jianghuai category. The main style of the Sichuan category is more intense, with a prominent pit and grain aroma, and the aftertaste is slightly bitter. while the aroma of Jianghuai category is more mellow and moderate, with typical aromas such as floral and fruity, honey, and grassy [7]. [PERSON] et al. [8] reviewed the GC-O and AEDA data from Jianghuai region strong-aroma baijiu (Yanghe Daqu and Gujinggong jiu) and Sichuan region strong-aroma baijiu (Luzhou Laojiao). They found that the Sichuan region strong-aroma baijiu has a higher content of esters and acids, which may be the reason for the difference in flavor between the two types of strong-aroma baijiu. The typical flavor of strong-aroma baijiu is the result of complex interactions between various aroma compounds as well as non-volatile compounds contained in it. More than 861 trace components have been found in strong-aroma baijiu and 141 trace components have been considered as the main aroma compounds [8]. Non-volatiles, although not directly affecting aroma, were found to be crucial in modulating flavor and overall flavor balance in baijiu [9]. Studies on the flavor contribution of non-volatile compounds to baijiu have mainly focused on taste and mouthfeel. Recent studies have shown that the non-volatiles could enhance the aroma release of most key aroma-active compounds in soy sauce-aroma type baijiu [10], thus affect the aroma. Another study of Laobaign baijiu reported that non-volatile compounds reduced the alcoholic and sweet odors, while amplifying fruity, acidic, floral, jujube and grain notes [11]. Non-volatile components in baijiu have diverse structures and chemical properties; how these compounds influence the aroma of baijiu remains unclear. The primary objective of this study was to elucidate the contribution of non-volatile compounds to the aroma profile of strong-aroma baijiu. GC-MS is the primary analytical technique used to classify baijiu. However, the production of baijiu involves a complex series of fermentation, distillation, and aging processes, which leads to the presence of many different compounds [12]. As a result, the limitations in separation and sensitivity of GC-MS may cause potential biomarkers to be overlooked.