## 1 Introduction  
Pear (_Pyrus_) is one of the most important temperate fruit tree species in the world, with a global cultivation area of about 1.4 million hm\({}^{2}\) and a total annual production of about 25.66 million tons [1], which has outstanding economic benefits. Aroma is an important indicator reflecting the flavor, ripeness and quality of pear fruits. The pleasant aroma of pear fruits is also a crucial factor in attracting consumers and enhancing market competitiveness [2]. Pear varieties are divided into European and Asian pears due to their geographical distribution [3]. Most European pears have a soft and juicy flesh texture and strong aroma, and main cultivars belong to _P. communis_[2, 4]. However, most _P. ussuriensis_ cultivars share similarities with European pears in softer fruits and develop very strong aroma during their ripening period [5]. The main cultivars of Asian pears belong to _P. bretschneideri, P. pyrifolia, P. ussuriensis_ and _P. sinkangensis_, and most crispy Asian pears have a crisp flesh with more juice but light aroma [4, 6]. In recent years, there have been many research reports on pear fruits aroma and VOCs. The VOCs of pears have been studied, and more than 300 kinds of VOCs have been detected in pear fruits [7]. Aroma consists of a mixture of VOCs, mainly including esters, aldehydes, alcohols, ketones and terpenoids [8; 9; 10]. Various combinations and contents of VOCs in fruits contribute to significant differences in aroma [11]. Although the type and content of VOCs can be influenced by some factors, such as cultivation [12; 13; 14], harvest maturity [15; 16; 17] and storage conditions [18; 19; 20; 21], variety itself is the fundamental factor affecting aroma formation. Furthermore, the formation of aroma substances is a dynamic process during fruit growth and storage. There are significant differences in the composition and concentration of VOCs in different varieties: esters are the most important volatile compounds in the fruit of _P. communis_[9]; the volatile compounds of _P. ussuriensis_ are mainly esters, hydrocarbons and aldehydes [22]; _P. pyrifolia_ mainly has esters, alcohols and aldehydes [10]; the volatile compounds of _P. bretschneideri_ are mainly esters and alcohols [23]; and the main volatile compounds of Korla pear (_P. sinkiangensis_) are hexanal, (E)-2-hexenal, 1-hexanol, (E)-2-hexen-1-ol, (Z)-3-hexen-1-ol and hexyl acetate [17]. Moreover, it was found that the VOCs of wild Kainth (_P. ushia_) pears in India are mainly esters and alkanes [24]. In addition, the quality of pear fruits is also influenced by the length of the storage period. Researchers found that the content of esters in the [PERSON] pear gradually increased and the content of alcohols and aldehydes gradually decreased as the storage time increased [10]. In recent years, HS-SPME combined with GC-MS has been used to accurately and efficiently analyze and identify volatiles in fruits [25]. It has been widely used for the determination of VOCs in apples [26; 27], pears [28; 29], grapes [30; 31], peaches [32], citrus [33] and other fruits. Currently, important progress has been made in research on pear flavor quality, but relatively few studies have been conducted on the changes in the VOCs of pear varieties with different flesh textures during different post-harvest shelf life. Storage is very important for pear fruits, not only to extend the freshness period of pear fruits and ensure their quality and taste, but also to increase the economic value of the fruits. In addition, the length of shelf life affects the type and content of aroma substances in the fruits, and changes in aroma substances are important in determining the shelf life of fruits. In this experiment, HS-SPME with GC-MS was used to study the differences in VOCs among eight pear varieties during their shelf life at room temperature.