## 1 Introduction  
Chinese bacon belongs to a wide range of salted, dried, and smoked meat products available in China. Improvements in people's living standards lead to changes in their diets, and over the past few decades, smoked meat products have risen in popularity due to their unique flavor.  
Zhenba Bacon is typically processed for two months, beginning in November and ending in December, based on the lunar calendar, with traditional processing methods of salting and smoking. Zhenba is located in the Qinba mountains, with temperatures at 0-10 \({}^{\circ}\)C in the winter, making it a suitable climate for the production of bacon. At the same time, Zhenba Bacon is a geographical symbol of China with an attractive color and a unique flavor, deeply favored by consumers.  
The flavor of Chinese bacon is a complex process involving a series of chemical reactions and a variety of factors. At present, most scholars at home and abroad believe that the flavor mainly follows three pathways: lipid oxidation, degradation of the precursor, and the Maillard reaction. Lipid oxidation in the formation of flavor in meat products is mainly caused by lipid oxidation [1].  
The research on lipid oxidation has examined two main areas [2; 3]. The first area is, the oxidation of double bonds of unsaturated fatty acid to generate peroxides, which can be further broken down to volatile carbonyl compounds. Further, hydroxyl fatty acid is hydrolyzed to produce acids and the acids undergo dehydration and cyclization to yield the final lactone compounds with meat aromas.  
A second aspect is that the degradation of precursor substances mainly includes the degradation of protein and oil [4]. Of course, the Maillard reaction is one of the most important reactions resulting from the heating process [5]. It utilizes the reaction between amino acids and reduces sugars to produce a variety of volatile flavor compounds in meat, such as pyrazine and pyridine [6].  
At present, research on volatile flavor substances in smoked meat mainly uses gas chromatography-mass spectrometry (GC-MS), full two-dimensional gas chromatography-time-of-flight mass spectrometry (GC \(\times\) GC-TOF MS), gas chromatography-sniffing (GC-O), electronic nose technology, etc. [7; 8; 9; 10; 11]. The gas chromatography-mass spectrometry (GC-IMS) ion migration technique has been emerging in recent years as a rapid detection of volatile flavor of advanced technology, GC-IMS can obtain the flavor substances and the composition of the discriminant information and sample quality, with high sensitivity, fast detection speed, easy operation and a sample analysis at low temperature, to better reflect the existing flavor state [12] of the sample. The GC-IMS approach was implemented to detect the flavor characteristics of food volatile compounds, which are usually employed to distinguish the odor characteristics of different samples. At present, the technique is commonly applied in meat [13; 14], fruits [15; 16], and wine [17]. Most of the previous studies mainly focused on the aroma and quality control and grading from food. GC-IMS has been widely used in food flavor analysis [18]. However, it is seldom used in Chinese bacon, which provides a new efficient method for future research on Chinese bacon, and can be combined with other detection techniques to obtain more suitable results.  
In order to provide some theoretical reference for the deep processing of Zhenba bacon and the development of food dishes, the evolution of volatile flavor substances of Zhenba bacon in different processing periods was studied by utilizing GC-IMS technology combined with GC-MS and heatmap analysis.