## 3 Results and Discussion
### Analysis of Aroma Active Compounds in Fresh and Frozen PJs Through GC-O/AI and OAV  
Numerous studies indicate that a multitude of volatiles have been identified within the food matrix, yet only a few contribute to aroma perception [(41; 42)]. It is noteworthy that certain volatiles, even at low concentrations, should be paid more attention due to their  
Figure 3: Multivariate statistical analysis of volatile compounds identified in fresh and frozen-treated PJ samples. (**A**) Score plot of principal component analysis (PCA); (**B**) hierarchical clustering heatmap (HCA) visualization (A1–F1 identified compounds as displayed in Table 2). extremely low odor thresholds. For this, the aroma active compounds present in the PJs were identified and screened out using GC-O/AI and odor activity value (OAV) analyses. As is known, odor-specific magnitude estimation (OSME) is widely employed to assess the volatiles responsible for aroma perception based on their aroma intensity (AI). Typically, higher AIs are attributed to more intense aromas, and are thus regarded as more significant to the aroma profiles of food. The application of GC-O/AI to different PJs showed a total of 14 aroma active compounds. Seven alcohols, four terpenes, and three aldehydes were perceived. The detailed data are indicated in Figure 4. These perceived compounds were all identified based on MS, RIs, and standards. As shown, the control group (FPJ0) contained 13 aroma active compounds, whereas the FPJ\({}_{--}20\)\({}^{\circ}\)C, FPJ\({}_{--}40\)\({}^{\circ}\)C, and FPJ\({}_{--}80\)\({}^{\circ}\)C samples contained only 9, 9, and 12 compounds, respectively. According to their characteristics, these compounds can be classified into five categories. Class 1 ((\(Z\))-3-hexen-1-ol) was characterized by fruity notes; Class 2, comprising hexanal, (\(E\))-2-hexenal, nonanal, and hexanol, was primarily associated with a grassy odor; Class 3, consisting of heptanol, teripinen-4-ol, \(\alpha\)-terpineol, and 1-octen-3-ol, was perceived as having earthrotes; Class 4, including \(\beta\)-pinene, \(\gamma\)-terpinene, and \(\beta\)-myrcene, was described as having woody notes; and Class 5 (linalool, limonene) featured floral or sweet descriptors. These findings aligned with previous research by [PERSON] et al. [19], who similarly identified \(\beta\)-pinene and \(\beta\)-myrcene as woody aroma components in pomerangate juice. Among these, nine odorants ((\(E\))-2-hexenal, linalool, hexanol, (\(Z\))-3-hexen-1-ol, heptanol, \(\beta\)-pinene, \(\beta\)-myrcene, \(\gamma\)-terpinene, and limonene) exhibited the near-highest AIs in the fresh control sample FPJ0, potentially representing the primary contributors to PJ flavor. However, the AIs of most compounds exhibited decreasing trends following frozen storage. By contrast, four compounds, 1-octen-3-ol, \(\alpha\)-terpineol, teripinen-4-ol, and nonanal, were found to have relatively strong intensities in the frozen-treated samples. The differential AIs of these 14 aroma active compounds among the PJs would result in significantly different sensory profiles. Unlike GC-O analysis, OAV can take the influence of the food matrix into account, as the odor thresholds involved depend on the individual food matrix [43]. Thus, OAVs are extensively employed in aroma active compound recognition [35; 44]. To delve deeper into their contribution to PJ aroma, the compounds perceived via GC-O/AI were selected for OAV determination. Commonly, OAVs are calculated based on their natural concentrations, with the aid of standard curves and odor thresholds sourced from the literature [22]. As shown, of the 14 aroma active compounds identified by GC-O/AI, the OAVs of six, six, six, and seven volatiles were more than 1 in FPJ0, FPJ\({}_{--}20\)\({}^{\circ}\)C, FPJ\({}_{--}40\)\({}^{\circ}\)C, and FPJ\({}_{--}80\)\({}^{\circ}\)C, respectively. Among them, 1-octen-3-ol, 1-hexanol, (\(Z\))-3-hexen-1-ol, hexanal, nonanal, and \(\beta\)-myrcene were confirmed as potent contributors to pomerangate juice's aroma profile in previous studies [19; 36].