## 1 Introduction  
Xuanwei ham is one of the three well-known dry-cured hams in China and has gained much popularity among consumers due to its unique flavour, rich nutrition, and delicious taste [1]. Recently, researchers have conducted in-depth studies on the functionality and absorption properties of bioactive peptides in Xuanwei ham, and it has been found that some of these peptides exhibit anti-hypertensive, antioxidant, and anti-inflammatory activities [2; 3]. Xuanwei ham is produced in the Xuanwei district of Yunnan province, where the distinctive climate attributes and intricate geographical features provide an optimal natural setting for its processes of salting, drying, fermentation, and ripening, promoting the formation of the unique flavour of Xuanwei ham [4]. Salting and ripening are crucial stages in the manufacturing of Xuanwei ham. The prolonged salting and ripening affect the biochemical and textural changes in muscles, albeit with varying degrees of intensity across different muscles [5]. The biceps femoris (BF) and semimembranosus (SM) muscles exhibit differential responses under the given circumstances [6]. The SM, as an external muscle, experiences accelerated dehydration and salt absorption during the initial phases of processing [6]. The biceps femoris (BF), as an intramuscular muscle,has a greater water content throughout its maturation, while the infiltration of salt into this muscle occurs at a comparatively advanced stage, specifically after a period of three months [6]. As a result, the proteolytic activity in BF is more pronounced compared to SM, leading to notable impacts on the textural profile and flavour profile [7]. At present, the processing method employed for Xuanwei ham is the traditional, workshop-style processing process, which is susceptible to the influence of bad weather, severely detracting from the quality of the ham. During the processing, the biochemical and microbiological activities affect the quality of the ham [8]. Different quality grades of ham may be produced due to the processing susceptibility of raw hams, even under consistent raw material and processing conditions [9]. The determination of the commercial grade of Xuanwei ham typically involves the utilisation of a traditional evaluation method known as the \"three sticks method\" [10]. This method entails inserting bamboo sticks into specific areas of the ham samples, namely the hip joint, knee joint, and sacral vertebra. Subsequently, professional technicians assess and score the odour attributes absorbed by these bamboo sticks [10]. The classification of the quality grade of the ham is based on the evaluation of changes in odour characteristics and intensities [11]. Proteolytic reactions and lipid oxidation are key processes in developing the characteristic flavour and quality grades of dry-cured ham [12]. The ham is typically subjected to an uncontrolled environment during processing, wherein numerous microorganisms are involved, notably bacteria and fungi originating from the raw materials and the surrounding surroundings [13]. A variety of microorganisms are present both inside and on the surface of the dry-cured ham, which is considered to play a crucial role in flavour development by facilitating proteolytic reactions and lipid oxidation during the product processing procedure [14]. Under specific circumstances, certain types of microorganisms undergo rapid proliferation inside or on the surface of the ham, resulting in the deterioration of the ham [15]. The presence of an unpleasant odour, along with accompanying deviations in colour and texture, renders the ham in question unsuitable for consumption [16]. _Bacillus_ are ubiquitous and diverse in terrestrial and marine ecosystems, which facilitates their contamination of a variety of foods at different stages of the food chain [17]. The genus _Bacillus_ includes species such as _Bacillus cereus_, _Bacillus licheniformis_, and _Bacillus subtilis_.