# Quality Control of Fried Pepper Oils Based on GC-MS Fingerprints and Chemometrics
## 1 Introduction  
Sichuan pepper, also referred to as huajiao, is a shrub belonging to the _Zanthoxylum_ genus in the Rutaceae family [1]. They have long been used as spices and in traditional Chinese medicine for the treatment of vomiting, toothache, stomachache, abdominal pain, and infected wounds [2, 3, 4]. Some bioactive extracts, such as essential oils, sanshools, and alkaloids, exert antimicrobial and antioxidant effects and regulate blood sugar levels [5, 6]. _Zanthoxylum bungemann_ Maxim. and _Zanthoxylum armatum_ DC. are two species extensively cultivated in Sichuan Province, China. \"Hanyuan hujaao\" and \"Hongya tengjiao\" are popular varieties of _Z. bungeanum_ Maxim. and _Z. armatum_ DC., respectively. They have been recognized as geographical indication products of Hanyuan and Hongya because of their unique characteristics. The pericarp of mature Hanyuan huajiao is red and was historically called gong jiao because it was listed as a tribute during the Tang Dynasty. In contrast, Hongya tengjiao has a green pericarp. In addition to the different colors, Hanyuan huajiao and Hongya tengjiao have different flavors [7]. It is well documented that volatile components are the key quality indices of peppers. Freshly harvested peppers are highly seasonal, with a high moisture content and short storage period. If not treated in a timely manner after harvest, they are prone to wilting, browning, mold growth, andthe deterioration of flavor quality. After harvest, fresh peppers are typically processed into dried pepper, pepper powder, and fried pepper oil. Fried pepper oil is a popular commitment used in Sichuan cuisine. It is obtained by immersing hujiao granules in vegetable oil and frying them at high temperatures to extract unique flavor components. Compared with pepper granules, fried pepper oil not only has stronger flavor permeability, but also strengthens the salty taste [8]. Relevant studies have established that aldehydes, terpen, alcohols, esters, and ketones are the primary aromatic components of fried pepper oils [9]. Meanwhile, compounds such as heptanal, nonanal, (E)-2-nonenal, and pentanal are primarily the products of lipid oxidation and significantly contribute to the fatty aroma of fried pepper oils. Terpenes, such as limonene, \(\alpha\)-pinene, \(\beta\)-pinene, \(\alpha\)-terpineol, and \(\beta\)-ocimene, are the most abundant substances in fried pepper oils and exhibit strong green, woody, and minor fragrances [10]. Lastly, alcohols such as \(\alpha\)-terpineol and linalool predominantly impart a nintry and herbal aroma to fried pepper oil, while esters and ketones principally contribute to fruity and floral fragrances [10]. However, the flavor profile of fried pepper oil is influenced by vegetable oil and raw materials. Thus,tocopherol, phytosterol, essential fatty acids, phenols, and other compounds present in vegetable oil, as well as the origin of huajiao and the production process, markedly affect the flavor of fried pepper oils. Therefore, ensuring product quality stability is a vital issue for factories that manufacture fried pepper oil. Fingerprinting techniques in conjunction with chemometric analysis have been extensively employed for the quality control of various products [11]. Chromatographic techniques such as high-performance liquid chromatography (HPLC), gas chromatography (GC), and thin-layer chromatography (TLC) coupled with detectors such as UV, DAD, and MS have been applied to develop chemical composition fingerprints [12,13]. Fingerprinting data combined with chemometric tools has the potential to assess the complex composition of a product. [PERSON] et al. [14] utilized the GC-MS fingerprinting of volatile compounds to successfully differentiate olive oil samples from different geographical regions in Spain. Similarly, [PERSON] et al. [11] pioneered an effective method for identifying adulteration in camelia oil by establishing a GC fingerprint of fatty acids and a GC-MS fingerprint of phytosterols in camelia oil.