# Evaluation of Different Drying Methods on the Quality Parameters of _Acanthopanax semicosus_ Fruits
## 3 Results
### Determination of Antioxidant Activity  
Antioxidant capacity is a crucial indicator for evaluating the functional properties of food products [53; 54]. As shown in Table S7, significant differences were observed among the groups for both DPPH and ABTS assays (\(p\)\(\leq\) 0.05), indicating that the drying method substantially affects antioxidant retention.  
DPPH radical scavenging activity is widely used to assess antioxidant potential, where higher values indicate stronger free radical scavenging capacity [55]. Among all groups, the VFD group exhibited the highest DPPH scavenging activity (65.3 \(\pm\) 2.6%), significantly higher than the other groups (\(p\)\(\leq\) 0.05), indicating that this method best preserves antioxidant compounds. The ND group (59.7 \(\pm\) 1.5%) also displayed relatively high DPPH activity, suggesting that the slow drying process may help mitigate the degradation of bioactive compounds. In contrast, HD (40.7 \(\pm\) 0.7%) and MD (46.8 \(\pm\) 2.1%) exhibited lower DPPH scavenging capacity, suggesting that high-temperature processing may lead to the degradation or oxidation of antioxidant components. The VD group had the lowest DPPH scavenging activity (11.5 \(\pm\) 0.1%), significantly lower than all other treatments (\(p\)\(\leq\) 0.05), indicating that this drying method may result in substantial degradation or structural changes of bioactive compounds, leading to a dramatic reduction in antioxidant capacity. Vacuum drying effectively preserved the antioxidant properties of Syzygium caryophylllatum fruit, particularly in retaining DPPH radical scavenging activity, whereas sun drying led to the greatest loss of antioxidant potential [56].  
ABTS radical scavenging capacity provides complementary insights into antioxidant potential, often used in combination with the DPPH assay for a more comprehensive evaluation [57]. The overall trends observed in the ABTS assay were consistent with the DPPH results. The VFD group showed the highest ABTS scavenging activity (32.1 \(\pm\) 0.6%), significantly superior to all other drying methods (\(p\leq\) 0.05), further confirming the effectiveness of freeze-drying in preserving antioxidant activity. The ND (25.1 \(\pm\) 1.1%) and MD (21.6 \(\pm\) 0.7%) groups exhibited moderate ABTS radical scavenging activity, suggesting that  
Figure 4: Metabolic profiles of AS fruits subjected to five different drying methods, analyzed using HS-SPME-GC-MS. OPLS-DA score plots illustrate the separation of metabolite profiles among drying treatments (Panel **A1,A2**), while volcano plots highlight significant metabolic variations (Panel **B1,B2**). The vertical blue dashed lines indicate the fold change (FC) threshold, and the horizontal blue dashed line represents the significance threshold (\(p\)-value). Black dots denote compounds without significant differential expression.  
these methods retain antioxidant compounds to some extent but still induce some level of degradation. Similar to the DPPH results, the HD (14.6 \(\pm\) 0.3%) and VD (4.3 \(\pm\) 0.1%) groups had the lowest ABTS scavenging activity, highlighting that these drying methods may cause severe oxidative damage or degradation of antioxidant compounds. The effect of different drying methods on mango, avocado, and tomato showed that freeze-drying retained the highest levels of antioxidants compared to refractance window and oven drying methods [58].